TWI501575B - Mobile rf apparatus, rf ic card and rf storage card - Google Patents

Description

Mobile RF device, RF IC card and RF memory card Field of invention

The present invention relates to the field of communications, and in particular, to a mobile radio frequency device, a radio frequency IC card, and a radio frequency memory card.

Background of the invention

With the popularity of mobile terminals, the application requirements for mobile terminal payment using mobile terminals are very urgent. At present, there are various implementation solutions, but each has its own disadvantages. At present, a radio frequency function (called a radio frequency SIM card) is added to a Subscriber Identity Module (SIM) card in a mobile terminal, or a short-range communication module is added to a mobile terminal motherboard to implement a mobile terminal. The method of short-range communication, the latter is called NFC (Near Field Communication). The emergence of these methods makes the mobile terminal become a super-smart terminal that can be recharged, consumed, traded and authenticated, which greatly satisfies the market. Urgent needs.

Among them, the short-distance solution of the mobile terminal based on the radio frequency SIM card has received extensive attention because of its simplicity and no need to change the mobile terminal. In this solution, the radio frequency SIM card adopts UHF (Ultra High Frequency) technology, UHF, especially the RF SIM card using the 2.4GHz ISM common frequency band (ie industrial, scientific and medical frequency bands), the operating frequency is very high, the size of the antenna is small, and a small antenna can be placed in the SIM card to transmit sufficient intensity. Signal, even if the RF SIM card is embedded in the mobile terminal, the RF signal can still be transmitted from the mobile terminal. In the card reader, the industry's mainstream RF (Radio Frequency) transceiver chip can be used to receive the majority of the receiver without additional amplification. The radio frequency signal of the mobile terminal enables the mobile terminal to have the short-range communication function without any structural change to the existing mobile terminal. However, different mobile terminals have great differences in the transmission effect of radio frequency signals due to different internal structures. The radio frequency SIM card radio communication distance of a mobile terminal with strong transmission may reach a distance of several meters, and the radio frequency SIM card communication distance of a mobile terminal with weak transmission. Only a few centimeters can be reached. In order to avoid the huge difference in RF signal attenuation between different mobile terminals, the radio frequency SIM card must be calibrated to the mobile terminal, that is, the attenuation parameter of the mobile terminal must be recorded into the card before use. The need for calibration is a major issue with RF SIM cards.

Another mobile payment technology, NFC, evolved based on the ISO 14443 standard contactless card technology. The fundamental point is that both transmit signals and energy using a magnetic field of 13.56 MHz. The main problems of NFC technology are:

1. The mobile terminal must be modified to achieve reliable two-way data communication. The NFC magnetic field coil cannot be integrated into the SIM card or SD card (Secure Digital Memory Card)/TF (TransFLash) card. The card used in the terminal.

At the frequency of 13.56MHz, the card reader and the card use the inductive coil coupling method to exchange signals and transmit energy. The direction of the card reader to the card needs to transmit energy and the 13.56MHz amplitude modulation signal simultaneously, and the size of the receiving coil on the card. The area has higher requirements; the card is in the direction of the card reader, and the card relies on the short-circuit and the load modulation mode of the coil on the open-circuit card instead of relying on the external energy to directly transmit the field strength to transmit information to the card reader, due to the load modulation signal requirement. The higher the coupling coefficient between the card coil and the card reader coil, the better the information transmitted by the card reader decoding card, which further increases the size and area requirements of the antenna on the card. On the other hand, since the 13.56 MHz frequency is lower, the size of the coupling coil is relatively large. In view of the above factors, the NFC requires that the antenna coil in the mobile terminal is sufficiently large, and the size cannot be placed in the card for the mobile terminal such as the SIM card or the SD/TF card. In addition, the metal and other conductive objects on the mobile terminal will be Seriously interfere with the receiving and load modulation effects of the antenna. In order to achieve good communication performance in near field communication, the mobile phone must be customized and modified to achieve the best effect of the antenna. The transformation point is, for example, placing the card's multi-turn antenna on the battery back cover of the mobile terminal, or guiding the antenna from the terminal motherboard to the back of the battery through a flexible PCB, the area of the antenna is equivalent to the size of the ordinary battery, and the rear of the mobile phone The cover cannot be made of metal.

2. The 13.56MHz frequency used by NFC needs to be calibrated for distance control.

Even if an NFC antenna can be replaced in any mobile terminal, since it uses the 13.56MHz frequency, the frequency signal will form a strong eddy current effect when encountering metal and other conductive objects, and the signal strength will follow the structure of the mobile terminal. The change causes a large fluctuation in the field strength on the NFC card receiving antenna, and the uncalibrated distance control cannot be performed.

Figure 1 shows the voltage-distance curve of the coil receiving circuit placed in various mobile terminals and maintaining the 13.56 MHz carrier constant on the same 14443 POS machine. The signal strength value is the necessary amplification of the receiving antenna induced voltage. Value, the magnification remains constant, just pay attention to the relative change in intensity with distance. It can be seen that the field strength difference received by different terminals is >30dB, and the field strength of the same terminal changes from 1cm to 10cm to about 25dB. The field strength change caused by the difference of the mobile phone has exceeded the field strength of the terminal within the control range of 1cm to 10cm. Changes, so the distance control of each terminal cannot be controlled by the same threshold, that is, the non-calibrated distance control cannot be realized.

Summary of invention

The technical problem to be solved by the present invention is to provide a mobile radio frequency device, so that a mobile terminal provided with the mobile radio frequency device can implement a credit card transaction such as electronic payment.

To solve the above technical problem, the present invention provides a mobile radio frequency device comprising at least one low frequency magnetic induction circuit, at least one low frequency amplification circuit, at least one threshold determination and demodulation circuit, at least one second main processor, and at least one radio frequency transceiver circuit. And the at least one radio frequency antenna, the low frequency magnetic induction circuit, the low frequency amplification circuit, the threshold determination and demodulation circuit, the second main processor, the radio frequency transceiver circuit, and the radio frequency antenna are connected in series; wherein the low frequency magnetic induction circuit and the low frequency amplification circuit The low-frequency receiving link composed of the threshold determination and demodulation circuit operates at a frequency below the highest frequency f0 of the pre-selected system without calibration work.

Further, the mobile radio frequency device may further have the following characteristics: the low frequency magnetic induction circuit is a coil, and the product of the conversion gain of the low frequency magnetic induction circuit and the amplification factor of the low frequency amplification circuit is the farthest card swiping with the system applied by the mobile terminal where the mobile radio device is located. The corresponding system preset value, the volume of the low frequency receiving link depends on the conversion gain of the low frequency magnetic induction circuit and the amplification factor of the low frequency amplifying circuit, and the volume of the low frequency receiving link increases with the increase of the conversion gain of the low frequency magnetic induction circuit. Large, or increased with the reduction of the amplification factor of the low frequency amplification circuit.

Further, the mobile radio frequency device may further have the following feature: the highest frequency f0 of the system without calibration work is in the special low frequency band or the low frequency band or the low frequency band, and the frequency range of the special low frequency band is 300 Hz to 3000 Hz. The frequency range of the very low frequency band is 3 kHz to 30 kHz, and the frequency range of the low frequency band is 30 kHz to 300 kHz.

Further, the above mobile radio frequency device may further have the following characteristics: the highest frequency f0 of the system without calibration work is in a frequency range of 300 Hz to 50 kHz.

Further, the above mobile radio frequency device may further have the following characteristics: the highest frequency f0 of the system without calibration work is 500 Hz, 1 KHz, 1.5 KHz, 2 KHz, 2.5 KHz, 3 KHz, 4 KHz, 5 KHz, 10 KHz, 20 KHz or 30 KHz.

Further, the above mobile radio frequency device may further have the following features, the threshold determination and demodulation circuit being composed of a comparison circuit and a decoding circuit connected to each other.

Further, the mobile radio frequency device may further have the following features: the threshold determination and demodulation circuit is composed of a sequentially connected comparison circuit, a demodulation circuit, and a decoding circuit.

Further, the above mobile radio frequency device may further have the following features: the low frequency magnetic induction circuit is a PCB coil, an enameled wire coil, a Hall device or a giant magnetoresistive device.

Further, the above mobile radio frequency device may further have the following features, and the mobile radio frequency device is placed in the mobile terminal.

Further, the mobile radio frequency device may further have the following features: the mobile radio frequency device is placed in a SIM card, a UIM card, a USIM card, a TF card, an SD card or an MMC card in the mobile terminal.

Further, the above mobile radio frequency device may also have the following features: the second main processor and the processor in the SIM/UIM/USIM/TF/SD/MMC card are the same shared processor.

Further, the mobile radio frequency device may further have the following characteristics: the mobile terminal is a mobile phone, a personal digital assistant PDA or a notebook computer.

In order to solve the above technical problem, the present invention also provides a radio frequency IC card comprising the mobile radio frequency device of any of the above.

In order to solve the above technical problem, the present invention also provides a radio frequency memory card comprising the mobile radio frequency device of any of the above.

In order to solve the above technical problem, the present invention also provides a method for determining the highest frequency f0 of the system in the above mobile radio frequency device without calibration work, comprising the following steps: step a1, determining the distance control target (Din, Dv) of the system, The system includes at least one mobile radio frequency device and at least one card reader, wherein Din indicates that all terminals loaded with the mobile radio frequency device ensure that the card can be swiped within a range of 0 to Din, and Dv represents a range of distance fluctuation, and the distance is The range of Din~(Din+Dv) is allowed to be swiped, and the range of distance greater than Din+Dv is not allowed to swipe; in step a2, the fluctuation range δ _R of the detection voltage in the mobile radio device caused by the card reader is determined; step a3, determining The fluctuation range δ _C of the detection voltage caused by the mobile radio frequency device itself; in step a4, the voltage distance curve of each typical terminal and the obstacle is tested at the f frequency, and the f frequency is in the ultra low frequency band or the low frequency band or the low frequency band Any of the frequencies, the frequency range of the special low frequency band is 300 Hz to 3000 Hz, and the frequency range of the very low frequency band is 3 kHz to 30 kHz. The frequency range of the low frequency band is 30 KHz to 300 KHz; in step a5, the distance control target (Din, Dv) determines the fluctuation range δ _A of the detection voltage in the mobile radio device, and δ _A is equal to the voltage distance from each typical terminal and obstacle The difference between the voltage value corresponding to the Din point on the curve of the curve having the average field strength attenuation curve and the voltage value corresponding to the (Din+Dv) point; and step a6, determining the detection of the mobile radio device caused by the terminal The voltage fluctuation range δ _T , δ _T represents the detection voltage fluctuation range in the mobile radio frequency device caused by the terminal attenuation characteristic, δ _T = δ _A - δ _R - δ _C ; Step a7, calculating the distance control between each typical terminal and the obstacle The maximum field strength difference δ at each distance point in the range, if δ is greater than δ _T , the frequency f is decreased, and the process proceeds to step a4; if δ is smaller than δ _T , the frequency f is increased, and the process proceeds to step a4; if δ is equal to δ _T , The current test frequency f is equal to the highest frequency f0 of the system without calibration work.

In order to solve the above technical problem, the present invention also provides a low frequency alternating magnetic field distance control method, which is applied to a mobile terminal including the mobile radio frequency device according to any of the preceding claims, the method comprising the following steps: Step a, receiving the received The low-frequency alternating magnetic field signal Br performs magnetoelectric conversion, and converts the low-frequency alternating magnetic field signal into an electrical signal Vo. If Br is a low-frequency alternating magnetic field signal with a constant amplitude, the magnetoelectric conversion formula is Vo=A*K*Br; if Br is For a low-frequency alternating magnetic field signal with a constant differential amplitude, the magnetoelectric conversion formula is Vo=A*K*dBr/dt, where K is the low-frequency magnetic induction circuit gain, A low-frequency amplification circuit gain, and A*K is the magnetoelectric conversion gain. Setting; step b, if the electric signal Vo converted by the low-frequency alternating magnetic field signal is greater than the preset comparison voltage signal threshold Vt, decoding the IDR of the card reader, entering the radio frequency communication, and the IDr together with the mobile radio frequency through the radio frequency channel The unique identification code IDc of the device itself is transmitted to the card reader while continuously monitoring the low frequency alternating magnetic field signal; step c, performing radio frequency communication, and splitting the radio frequency communication data Send and receive multiple data packets several times, each time receiving packets or radio contract will check if Vo is greater than Vt, if it is to continue trading until the end of the RF communications, RF communications or the end of the transaction, return to step a.

Further, the low frequency alternating magnetic field distance control method may further have the following features: the method for determining the magnetoelectric conversion gain in the step a is as follows: step a1, determining the magnetic induction gain K, and selecting the low frequency magnetic induction circuit on the carrier where the mobile radio device is located, Thereby the magnetic induction gain K is selected; in step a2, the gain A of the low frequency amplifying circuit is arbitrarily selected under the following principle:

1) The magnetic induction intensity Br received by the mobile radio frequency device at any position is less than the value required by the system safety specification;

2) The mobile radio frequency device is placed in one or more carriers specified by the system, and the signal-to-noise ratio of the magnetic induction signal after the magnetoelectric conversion is greater than the SNR;

3) If the magnetic induction circuit is a Hall device or a giant magnetoresistive device: A*K=Vt/Bgate, where Bgate is the magnetic induction threshold; if the magnetic induction circuit is a coil: A*K=Vt/B_RATEgate, where B_RATEgate is the magnetic induction change Rate threshold, magnetic induction rate change rate B_RATE = dBr / dt.

Further, the low frequency alternating magnetic field distance control method may further have the following feature, in which the signal to noise ratio SNR is greater than 5.

Further, the low frequency alternating magnetic field distance control method may further have the following characteristics: the low frequency magnetic induction circuit is a coil, and the mobile radio frequency device is placed in a SIM card, a UIM card, a USIM card, a TF card, an SD card, or an MMC card. The number of turns of the coil is 1 to 20 匝, and the gain A of the low frequency amplifying circuit is greater than 100.

Further, the low frequency alternating magnetic field distance control method may further have the following characteristics. In the step a, the magnetoelectric conversion has an error, that is, Vo has fluctuation, the fluctuation range is δc (db), and the error δc (db) is selected. And the control method is as follows: the range of δc is 2-6dB; the control method of δc includes the following steps: assuming that the maximum fluctuation range of the attenuation of the low-frequency alternating magnetic field signal by various mobile terminals applied by the mobile radio device is δT, the error The attenuation of standard obstacles in the control system is δT/2.

Step 601: The standard card reader emits a low-frequency alternating magnetic field signal having a constant amplitude or a constant differential amplitude at a fixed distance and a position. The amplitude value of the magnetic field after the magnetic field of the amplitude value Bgate or the differential amplitude value B_RATEgate of the system is a voltage signal Vo near Vt; step 602: determining a Vo range (Vt - δcx / 2, Vt - δcx / 2), where δcx < δc; step 603: measuring an output electrical signal Vo of the low frequency amplifying circuit in the mobile radio frequency device, if If Vo exceeds the range of (Vt-δcx/2, Vt-δcx/2), the amplification factor A of the low-frequency amplification circuit is adjusted by the software setting until Vo is within the above range; Step 604: setting the Vt value of the mobile radio device through the software setting Step 603 adjusts the output electrical signal Vo after A.

Further, the low frequency alternating magnetic field distance control method may further have the following feature: the voltage threshold Vt is replaced by a current threshold corresponding to the voltage threshold Vt.

The mobile radio frequency device of the present invention enables a mobile terminal provided with the mobile radio frequency device to implement a credit card transaction such as electronic payment.

Simple illustration

The first picture shows the voltage-distance curve tested when the coil receiving circuit is placed in various mobile terminals and the 13.56 MHz carrier is kept constant on the same 14443 POS machine. The second picture shows the system without calibration in the short-distance communication method of the present invention. The block diagram of the selection system of the highest frequency f0; Figure 3 is a schematic diagram of determining the total receiving detection voltage fluctuation range δ _A of the system by the distance control target (Din, Dv); Figure 4 is the typical terminal and obstacle voltage distance curve. And its fluctuation interval δ schematic diagram; Figure 5 is the voltage distance curve of five typical mobile terminals when the frequency f is 3.3KHz; Figure 6 is the received voltage signal and sine of the unmodulated direct baseband transmission detected inside the mobile RF device FIG. 7 is a schematic diagram of a calculation method of a reference voltage distance curve; FIG. 8 is a structural diagram of a short-range communication system according to an embodiment of the present invention; and FIG. 9 is a card reader. Schematic diagram of the low-frequency transmitting part; Figure 10 is a schematic diagram of the format of the low-frequency data frame of the card reader; Figure 11 shows the coil receiving circuit placed in various mobile terminals and passed by the signal source. The low-frequency transmitting coil emits a voltage distance curve tested under a constant 1 KHz magnetic field; FIG. 12 is a structural diagram of a radio frequency IC card according to an embodiment of the present invention; and FIG. 13 is a schematic structural view of a 4匝pcb copper-cord coil antenna applied to a SIM card; Figure 14 is the differential Manchester encoding format of 5bit data 11010 and the field strength, coil receiving voltage waveform; Figure 15 is the constant amplitude map received by the sim card in the 1KHz low frequency magnetic mobile terminal; Figure 16 is the application Schematic diagram of the 4匝pcb coil antenna of the TF card; Figure 17 is a block diagram of the error control system.

Detailed description of the preferred embodiment

Firstly, the terminal appearing in the following refers to a terminal loaded with a mobile radio device in a preset case, and refers to a terminal that can be moved, that is, a mobile terminal, such as a mobile phone, a distance finger reader and a mobile radio device. The distance between the reader and the terminal loaded with the mobile radio device.

The invention aims at the distance control problem of the short-distance transaction of the radio frequency device (especially the radio frequency card built in the terminal, such as the radio frequency SIM card) and the card reader device, and proposes a function of transmitting and receiving with low frequency alternating magnetic field and transmitting and receiving radio frequency signals. The function of the card reader and the corresponding short-range communication system comprising a low-frequency alternating magnetic field induction receiving function and a radio frequency signal transceiving function, and a short-distance communication method corresponding to the system. The invention utilizes the characteristics of low-frequency alternating magnetic field penetrating different terminal attenuation differences to perform distance control, and uses high-frequency radio frequency to effectively penetrate the terminal to complete high-speed two-way communication for transaction. The system performs the distance detection and control without calibration by a preset threshold determination method, that is, the card reader transmits the low frequency alternating magnetic field signal according to the preset transmission parameter, and the mobile radio frequency device detects the magnetic field signal at each distance point and amplifies the signal. A voltage signal having a constant amplitude corresponding to the distance is further determined by a preset voltage threshold Vt to determine whether the terminal enters a preset effective distance interval (a range of effective distances, that is, a range in which the card is allowed to be swiped), and the voltage threshold Vt is the same for all terminals. No calibration required. The invention combines the low-frequency one-way communication and the RF two-way communication to complete the unique binding of the card reader and the mobile radio device, and after binding, completes the bidirectional high-speed and large-volume communication through the radio frequency channel. The system of the present invention can realize that the data communication distance (ie, the transaction distance) of the terminal (such as the mobile phone equipped with the radio frequency SIM card) containing the mobile radio frequency device and the card reader is reliably controlled within a prescribed range, and the terminal is not required to be calibrated.

The principles and features of the present invention are described in the following with reference to the accompanying drawings.

The short-range communication method of the present invention is applied to a short-range communication system including at least one card reader and at least one mobile radio frequency device, and includes the following four steps of step a, step b, step c and step d, respectively The steps are specifically described: in step a, the card reader transmits a low frequency alternating magnetic field signal according to a preset transmission parameter, and the low frequency alternating magnetic field signal carries the identity identification information of the card reader, wherein the transmitting parameter includes a low frequency alternating magnetic field. The frequency of the signal, which is equal to or less than the highest frequency f0 of the system without calibration work; wherein the identity information may be the identification code ID.

It should be noted here that the frequency of the low-frequency alternating magnetic field signal in this step refers to the frequency corresponding to the high-end frequency cut-off point of the 3 dB bandwidth of the spectrum of the low-frequency alternating signal.

The lower the frequency of the low-frequency alternating magnetic field, the smaller the difference in attenuation after passing through various types of terminals. With this characteristic, the frequency selection system (as shown in Fig. 2) selects frequency points with sufficiently small differences to achieve no Calibrate distance control. The low frequency alternating magnetic field signal is transmitted through a standard magnetic field transmitting coil by using a standard signal source, and the low frequency alternating magnetic field signal is received inside each typical mobile terminal and obstacle, and the transmitting frequency is adjusted until the frequency point f0 is found, so that the mobile radio frequency device is loaded (loading In the mobile terminal, the received voltage (the voltage is a voltage signal whose amplitude corresponding to the distance obtained by the low-frequency alternating magnetic field signal is amplified) is at the same distance from the center point of the plane of the transmitting coil, and different terminals and The field strength difference between the obstacles is roughly equal to the set fluctuation range δ _T . The frequency point f0 and the frequency band lower than the frequency point f0 are the frequency bands in which the system has no calibration work. It is not necessary to calibrate any terminal in any system, and the working frequency point (The frequency of the aforementioned low-frequency alternating magnetic field signal) is higher than f0, and the system needs to be calibrated. Generally, the more the operating frequency is higher than f0, the more terminals that need to be calibrated, the higher the calibration complexity. Frequency selection is a one-time job, once selected, no changes are needed during use.

2 is a structural block diagram of a selection system of the highest frequency f0 in which the system has no calibration work in the short-range communication method of the present invention. As shown in FIG. 2, the frequency point selection system has the following components: the transmission system consists of a signal source 505 and a low-frequency magnetic field. The transmitting coil is composed of a typical mobile terminal 501 and an obstacle, a signal strength tester 503 (a voltmeter, an oscilloscope, a spectrum analyzer, etc.), and the mobile terminal 501 has a low frequency receiving module 502 therein. Signal source 505 can accurately generate signals of various frequencies, waveforms, and amplitudes. The principle of frequency point selection is that the signal source 505 generates a sine wave signal with a fixed amplitude frequency f, which is transmitted through the transmitting coil 504, and the low frequency receiving module 502 is placed inside the selected typical mobile terminal 501 or obstacle, and the received low frequency signal. The signal strength tester 503 is connected to the signal strength tester 503 through a dedicated signal line, and the signal strength tester 503 tests the received voltage. Changing the distance of the mobile terminal can obtain a curve of the detection voltage of the mobile terminal or the obstacle under the condition of the frequency f (hereinafter referred to as a voltage distance curve), and changing the mobile terminal or the obstacle can obtain a curve of the plurality of terminals, and change A different curve can also be obtained for the frequency f.

In step a, the highest frequency f0 of the system without calibration work is determined by the following steps: Step 101, determining the distance control target (Din, Dv), wherein Din indicates that all terminals in the range of 0~Din ensure that the card can be swiped, and Dv represents the range of distance fluctuation. , the distance is Din~ (Din+Dv) is allowed to swipe, the distance is greater than Din+Dv range is not allowed to swipe; for example (5cm, 5 cm) means that all terminals below 5cm ensure that the card can be swiped, 5cm ~ 10cm allow swiping, more than 10cm can't swipe. The distance control target is determined by the specific application. (0 to Din+Dv) is called the distance control range.

Step 102: determining a fluctuation range δ _R of the detection voltage in the mobile radio frequency device caused by the card reader; the fluctuation of the low frequency transmission circuit parameter of the card reader forms a fluctuation of the transmission field strength, causing fluctuation of the detection voltage in the mobile radio frequency device, and the parameter includes the transmission. Drive voltage fluctuations, coil parameter fluctuations, temperature effects, etc. δ _{R is} controlled by the reader design and production process. This fluctuation can be calibrated in the production process. Since the low frequency transmitting circuit operates at a low frequency, δ _R can usually be controlled well, for example, within 4 dB.

Step 103: determining a fluctuation range δ _C of the detection voltage caused by the mobile radio frequency device itself; and fluctuating the final detection output voltage caused by the fluctuation of the low frequency receiving circuit parameter of the mobile radio frequency device, the parameter including the receiving antenna error, the amplifier gain error, the comparator or AD error, temperature effects, and noise. δ _{C is} controlled by the design and production of mobile RF devices. This fluctuation can be calibrated at the production stage. Since the operating frequency of the low frequency receiving circuit of the mobile RF device is very low, δ _C can usually be controlled well, for example, within 4 dB.

Step 104, testing the voltage distance curve of each typical terminal and the obstacle at the f frequency, wherein the f frequency is any frequency in the special low frequency band or the low frequency band or the low frequency band, and the frequency range of the special low frequency band is 300 Hz~ 3000Hz, the frequency range of the very low frequency band is 3KHz~30KHz, and the frequency range of the low frequency band is 30KHz~300KHz. Before performing this step 104, a preparatory work is to be done, that is, a typical terminal and a typical obstacle are selected. The selection principle of a typical terminal is mainly selected according to the number of terminal metals or conductive structures. The more metal, the greater the attenuation. For example, plastic casing, metal casing, thick metal shell, thin metal shell, large-size terminal, small-sized terminal, etc. can be selected. The number of typical terminals is not strictly limited. The selection of a typical terminal can basically cover the attenuation characteristics of the terminal to the low-frequency alternating magnetic field signal. In order to avoid the difference of individual mobile terminals, the mobile terminal model authentication may be added in the application, and the mobile terminal that needs to support the payment application is attempted to perform a card test to confirm that the attenuation characteristics of the mobile terminal of the model meet the requirements. Typical obstacles can be selected from different materials, such as plastic, aluminum, copper, iron, stainless steel and other mobile terminals. It is placed between the card reader and the mobile RF device as an equivalent obstacle for the attenuation characteristics of the mobile terminal. .

Step 105: Determine, by the distance control target (Din, Dv), a fluctuation range δ _A of the detection voltage in the mobile radio frequency device, and δ _A is equal to a voltage having a slope of the average field strength attenuation curve obtained from a voltage distance curve of each typical terminal and the obstacle The difference between the voltage value corresponding to the Din point on the curve and the voltage value corresponding to the (Din+Dv) point; the third figure is the total receiving detection voltage fluctuation range δ _A determined by the distance control target (Din, Dv) schematic diagram. As shown in Fig. 3, the voltage value corresponding to the (Din+Dv) point is V2, and the voltage value corresponding to the Din point is V1, then δ _A = V1 - V2.

Step 106: determining a fluctuation range δ _T of the detected voltage in the mobile radio frequency device caused by the terminal, where the parameter δ _T represents a range of detection voltage fluctuations in the mobile radio frequency device caused by the terminal attenuation characteristic, δ _T = δ _A - δ _R - δ _C ; Step 107: Calculate a maximum field strength difference δ (also referred to as a fluctuation interval) at each distance point between each typical terminal and an obstacle in a distance control range. If δ is greater than δ _T , decrease the frequency f, and go to step a4; If δ is smaller than δ _T , the frequency f is increased, and step a4 is turned; if δ is equal to δ _T , the current test frequency f is equal to the highest frequency f0 of the system without calibration work.

Figure 4 is a typical terminal and obstacle voltage distance curve and its fluctuation interval δ schematic. As shown in Figure 4, the voltage distance curve corresponding to the maximum attenuation terminal or obstacle is called the maximum attenuation curve. The voltage attenuation curve corresponding to the minimum attenuation terminal or obstacle is called the minimum attenuation curve, and the area surrounded by the maximum and minimum attenuation curves is called For a typical terminal and obstacle voltage distance curve distribution interval, the voltage corresponding to the minimum attenuation curve of any distance D is V3, and the corresponding voltage on the maximum attenuation curve is V4, then δ=V3-V4.

So far, in the case of limiting the distance control target, the highest frequency f0 of the system without calibration work is determined. The system can adopt the modulation method or the method of directly transmitting the baseband signal. The maximum frequency component of the system operation is as long as it is not greater than f0, and the distance control does not need to be calibrated.

An example of the determination process of f0. Figure 5 is a voltage distance curve of five typical mobile terminals at a frequency f of 3.3 kHz. As shown in Figure 5, the system distance control target is (5cm, 5 cm), the range of the system 0 to 10cm distance range is about 40dB, and the detection voltage fluctuations in the mobile radio frequency device caused by the card reader and the mobile radio device are both It is 4 dB, that is, δ _R = δ _C = 4 dB, δ _A = 20 dB, δ _T = δ _A - δ _R - δ _C = 12 dB. Assuming that the five terminals can represent all the terminals used by the system, the maximum fluctuation of the inspection curve at each distance point is approximately equal to 12 dB, so the highest frequency f0 of the system without calibration work can be determined as f0=3.3 KHz.

In step a, the transmission parameters may further include a modulation mode, an encoding mode, and a transmitting magnetic induction intensity amplitude Br. The basic principle of selecting the transmission parameters is to ensure that the mobile radio frequency device detects and amplifies the low-frequency alternating magnetic field signal emitted by the card reader at various distance points, and the signal is a voltage signal with a constant amplitude corresponding to the distance. Figure 6 is a voltage waveform diagram of the received voltage signal and the received voltage signal when the sinusoidal FSK modulation is detected in the unmodulated direct baseband transmission detected by the mobile radio frequency device, where a is the received voltage signal when the direct baseband is transmitted without modulation. Waveform diagram, b is the waveform of the received voltage signal when sinusoidal FSK modulation. As shown in FIG. 6, the detection voltage signal is a variable voltage signal including demodulation information, and the signal may be an AC voltage signal without a DC component or a voltage signal having a DC component, and the constant amplitude refers to a change of an AC component. The maximum is constant between different transmission symbols.

The modulation mode, the coding mode and the emission magnetic induction intensity amplitude Br in the transmission parameters are selected by the following steps a11 to a13: step a11, selecting any coding mode without the average DC component, such as Manchester code, differential Manchester code, zeroing Code, etc.; in step a12, a carrier modulation mode with no modulation mode or no amplitude change is selected, and the carrier modulation mode can select any modulation mode with no change in amplitude. For example, the carrier can adopt a sine wave, a pulse, a triangle wave, etc., and the modulation mode can be selected as Open key control method (OOK), phase shift keying method or frequency shift keying method (FSK); when using no modulation mode, the encoded baseband signal is directly driven by the transmitting coil by the driving circuit; step a13, selected emission The magnetic induction intensity amplitude Br is obtained by selecting a typical noise terminal and an easy-to-implement gain parameter of the magnetic detection and amplification in the mobile radio device under the selected operating frequency, modulation mode and coding mode less than f0, which will include the mobile The mobile terminal of the radio frequency device is placed at a distance Din+Dv farthest from the card reader for the distance control target. If the mobile RF device is received by a magnetic induction circuit that detects a magnetic field strength value such as a Hall device or a giant magnetoresistive device, the card reader emits a magnetic field signal having a constant amplitude of change in magnetic induction intensity; if the mobile RF device uses a coil or the like to detect a rate of change of the magnetic field strength When the sensing circuit receives, the card reader emits a magnetic field signal with a constant magnitude of the magnetic induction intensity change rate (ie, the differential amplitude), and tests the inherent noise voltage amplitude of the detection voltage in the mobile radio device under the condition that the card reader does not transmit the low frequency alternating magnetic field signal. Vn, then measuring the detection voltage Vr in the radio frequency device when the card reader transmits the low frequency alternating magnetic field signal by using the selected modulation and coding mode, and selecting the emission amplitude value Bgate or the differential amplitude value B_RATEgate so that Vr/Vn>SNR and SNR are mobile radio frequencies. The signal to noise ratio of the device. The choice of SNR value is usually as large as possible, but too large will cause the reader to transmit too much power, which is difficult to achieve. The typical value can be SNR=10. When SNR is determined, Br is determined by the above method, according to the type of magnetic induction circuit selected by the system. Differently, the Br parameter values are divided into two types. The Hall device and the giant magnetoresistive device receiving system are the magnetic induction intensity amplitude threshold Bgate, and the coil receiving system is the magnetic induction intensity change rate amplitude threshold B_RATEgate.

Step b, the mobile radio frequency device receives and detects the low frequency alternating magnetic field signal at each distance point and amplifies the voltage signal with a constant amplitude corresponding to the distance, and further determines that the mobile radio frequency is loaded by a preset voltage threshold Vt. Whether the terminal of the device enters a preset effective distance interval, the voltage threshold Vt is the same for all terminals loaded with the mobile radio frequency device; in step b, the preset voltage threshold Vt is determined by the following steps 201 to 203 The premise is that it is determined that the reader transmitter and the mobile radio device receive no fluctuation, or the received detection voltage fluctuation caused by the two is much smaller than δ _R and δ _c : Step 201, under the selected transmission parameters, measure each typical terminal And a voltage distance curve of the obstacle, wherein the emission parameter includes a frequency of the low frequency alternating magnetic field signal, a modulation mode, a coding mode, and a magnitude of the transmitted magnetic induction intensity Br; step 202, obtaining a reference voltage distance curve, and the reference voltage distance curve is typical The intermediate value of the terminal and obstacle curves, the voltage amplitudes from the upper and lower boundaries of the typical terminal curve are δ _T /2, as shown in FIG. 7; in step 203, the detection voltage threshold Vt in the mobile radio device is selected, and the Vt value is equal to the voltage value corresponding to the distance control target Din and (Din+Dv) respectively in dBmV. The intermediate value of the voltage value. As shown in Fig. 7, the voltage corresponding to Din on the reference voltage distance curve is V5 (dBmV), and the voltage value corresponding to the (Din+Dv) point is V6 (dBmV), then Vt=V5-(V5-V6 )/2 (dBmV).

Step c, if the voltage signal corresponding to the received low frequency alternating magnetic field signal is greater than or equal to the preset voltage threshold Vt, the terminal loaded with the mobile radio frequency device enters the preset effective swipe interval, and the mobile radio frequency device receives from the receiving Obtaining the identity information of the card reader in the low frequency alternating magnetic field signal, and transmitting the card identification information together with the identity information thereof to the card reader through the radio frequency channel; in step d, the card reader receives the mobile radio frequency device and transmits the information through the radio frequency channel. Information, comparing whether the identity information of the card reader in the information is consistent with the identity information of the card, and if they are consistent, combining the identity information and the identity information of the mobile radio device as a combined address, and the mobile radio device Swipe transactions through the RF channel. Here, the card transaction does not only refer to electronic payment, but also other communication processes through the RF channel, such as recharge, consumption, identity authentication, etc. The card transaction in this document refers to communication through the RF channel, especially near-field communication. Communication through the RF channel.

In the present invention, the frequency of the low-frequency alternating magnetic field signal is in the ultra-low frequency band or the low-frequency band or the low-frequency band, wherein the frequency range of the ultra-low frequency band is 300 Hz to 3000 Hz, and the frequency range of the low-frequency band is 3 kHz to 30 KHz, and the frequency band of the low frequency band is The frequency range is from 30KHz to 300KHz. Preferably, the frequency of the low frequency alternating magnetic field signal may be 300 Hz to 50 kHz. Preferably, the frequency of the low frequency alternating magnetic field signal may be 500 Hz, 1 KHz, 1.5 KHz, 2 KHz, 2.5 KHz, 3 KHz, 4 KHz, 5 KHz, 10 KHz, 20 KHz or 30 KHz.

The short-distance communication method of the invention adopts a combination of low-frequency magnetic field one-way communication and radio frequency electromagnetic field high-speed two-way communication, thereby avoiding problems such as antenna problem caused by unique 13.56 MHz frequency point two-way communication and distance control in NFC system, and large difference in terminal signal attenuation. . In the method, the card reader transmits the unique identifier Idr (ie, the aforementioned identity information) to the mobile radio device by using the low frequency unidirectional channel, and the mobile radio device attaches its unique identifier IDc to the IDr through the radio frequency bidirectional channel, and then transmits the signal to the IDr. The card reader compares the correctness of the returned IDr, thereby realizing the unique binding of the card reader to the mobile radio device. After binding, the card reader and the mobile RF device use the RF bidirectional channel to realize high-speed and large-volume communication until the transaction is completed.

The short-range communication method of the invention realizes that the data communication distance (ie, the transaction distance) of the radio frequency communication terminal (such as the mobile phone equipped with the radio frequency SIM card) containing the mobile radio frequency device and the card reader is reliably controlled within the prescribed range, and Calibrate the terminal.

In order to implement the above-described short-range communication method, the present invention also proposes a short-range communication system. The short-range communication system of the present invention comprises at least one card reader and at least one mobile radio frequency device, wherein: the card reader is configured to transmit a low-frequency alternating magnetic field signal according to a preset transmission parameter, and the low-frequency alternating magnetic field signal carries the card reading The identification information of the device, wherein the transmission parameter comprises a frequency of the low frequency alternating magnetic field signal, the frequency is equal to or less than the highest frequency f0 of the system without calibration work; the card reader is further configured to receive information transmitted by the mobile radio device through the radio frequency channel, Comparing whether the identity information of the card reader in the information is consistent with the identity information of the card reader. If they are consistent, the combination of the identity information of the identity and the identity information of the mobile radio device is used as the combined address, and the mobile radio device passes the radio frequency. The channel performs a credit card transaction; the mobile radio frequency device is configured to receive and detect the low frequency alternating magnetic field signal emitted by the card reader at each distance point and amplify the voltage signal with a constant amplitude corresponding to the distance, and then pass the preset voltage threshold Vt determines whether the terminal loaded with the mobile radio device has entered the preset effective a distance interval, wherein the voltage threshold Vt is the same for all terminals loaded with the mobile radio frequency device; and the mobile radio frequency device is further configured to: when the voltage signal corresponding to the received low frequency alternating magnetic field signal is greater than or equal to a preset voltage threshold Vt Obtaining the identity information of the card reader from the received low frequency alternating magnetic field signal, and transmitting the card identification information together with the identity information thereof to the card reader through the radio frequency channel; the mobile radio frequency device is also used to pass the card reader The RF channel performs a credit card transaction.

The identity information may be an ID code.

It can be seen from the above that the card reader in the short-range communication system of the present invention has two basic functions of a low-frequency transmitting function and a radio frequency transceiving function, and it can be said that the card reader in the short-range communication system of the present invention has a low-frequency transmitting module and a radio frequency. The two basic modules of the transceiver module; the mobile radio frequency device in the short-range communication system of the present invention has two basic functions of a low frequency receiving function and a radio frequency transceiving function, and it can also be said that the mobile radio frequency device in the short-distance communication system of the present invention has Two basic modules, such as a low frequency receiving module and a radio frequency transceiver module.

Further, the above-mentioned short-range communication system may be implemented by a specific circuit: the card reader includes at least one low-frequency transmitting coil, at least one driving circuit, at least one encoding circuit, at least one first main processor, and at least one radio frequency transceiver The circuit and the at least one radio frequency antenna, wherein the low frequency transmitting coil, the driving circuit, the encoding circuit, the first main processor, the radio frequency transceiver circuit, the radio frequency antenna, and the serial connection in series; the mobile radio frequency device comprises at least one low frequency magnetic induction circuit, at least one low frequency amplification a circuit, at least one threshold determination and demodulation circuit, at least one second main processor, at least one radio frequency transceiver circuit, and at least one radio frequency antenna, wherein the low frequency magnetic induction circuit, the low frequency amplification circuit, the threshold determination and demodulation circuit, and the second main The processor, the RF transceiver circuit, and the RF antenna are connected in series in series. Preferably, in the above specific implementation circuit, a modulation circuit may be further disposed between the driving circuit of the card reader and the encoding circuit.

In the above specific implementation circuit, the low frequency transmitting coil, the driving circuit and the encoding circuit (including the modulating circuit when modulating the circuit) in the card reader can be regarded as a component of the low frequency transmitting module, and the first in the card reader The main processor, the RF transceiver circuit and the RF antenna can be considered as components of the RF transceiver module in the card reader; the low frequency magnetic induction circuit, the low frequency amplification circuit and the threshold determination and demodulation circuit in the mobile RF device can be regarded as the low frequency receiving mode. The components of the group, the second main processor in the mobile radio device, the radio frequency transceiver circuit, and the radio frequency antenna can be considered as components of the radio frequency transceiver module in the mobile radio device.

Preferably, in the above specific implementation circuit, the low frequency transmitting coil may be an enameled wire coil or a PCB coil. Further, the number of turns of the low frequency transmitting coil may be greater than 10 turns. Preferably, the number of turns of the low frequency transmitting coil is 50 to 500 turns. Preferably, the low frequency transmitting coil is packed with a ferrite core or a core. Preferably, the cross-sectional area of the area enclosed by the low-frequency transmitting coil is the widest than the cross-sectional width of the mobile radio frequency terminal. Preferably, the section of the area enclosed by the low frequency transmitting coil comprises at least a circular area of 3 cm in diameter or a square area of 3 cm * 3 cm.

Preferably, the low frequency magnetic induction circuit described above may be a PCB coil, an enameled wire coil, a Hall device or a giant magnetoresistive device.

In the present invention, the mobile radio frequency device may be placed in the mobile terminal, or may be placed in a SIM card, a UIM card, a USIM card, a TF card or an SD card in the mobile terminal. The mobile terminal can be a mobile phone, a personal digital assistant PDA or a notebook computer.

The principle of the short-range communication system of the present invention will be described below:

1. The method and apparatus for selecting the highest frequency f0 of the system without calibration work have been described in the content of the aforementioned short-range communication method, and will not be described herein;

2. The principle of distance measurement and control is as follows: the card reader transmits a low-frequency alternating magnetic field signal not higher than the selected frequency f0 according to the distance control target and continuously circulates with the set transmission parameter, and the signal is modulated or directly baseband The transmission method carries a data frame, and the data frame contains the unique identification code Idr of the card reader (of course, other identification information). When the mobile terminal loaded with the mobile radio frequency device is placed around the card reader, the low frequency alternating magnetic field signal penetrates the terminal to reach the internal mobile radio frequency device, and the mobile radio frequency device detects the magnetic field signal at each distance point and amplifies the distance to the distance Corresponding to the constant voltage signal, when the amplitude of the voltage is lower than the preset receiving voltage threshold Vt in the card, it indicates that the terminal does not enter the effective swipe distance range, and the card is not allowed to be swiped; when the voltage is higher than the preset in the card Receiving the voltage threshold value Vt, indicating that the terminal enters the predetermined valid card swipe range of the card reader, and the low frequency receiving circuit (refers to the low frequency magnetic induction circuit, the low frequency amplifying circuit and the threshold determining and demodulating circuit) in the mobile radio device starts the decoding process, and obtains the decoding process. The unique identification code IDr of the reader. On the other hand, there is a one-to-one correspondence between the voltage signal after the magnetic field conversion in the mobile radio frequency device and the distance between the card reader and the mobile radio frequency device, and the relationship is determined by the voltage distance variation curve, and according to the corresponding relationship, the voltage can be used. The distance between the mobile radio device and the card reader is determined, thereby indirectly determining the distance between the mobile terminal and the card reader. The setting of Vt and transmission parameters is one operation, and no change is required once the setting is in use.

3. Process principle of mobile radio device accessing card reader: The mobile radio device access card reader mainly includes the unique binding process of the card reader and the mobile radio device. The binding process is illustrated here: the mobile radio device removes the card reader unique identification code IDr from the low frequency signal and transmits it to the second main processing module in the mobile radio device, and the second main processing module will move the radio frequency The unique identification code IDc of the device is sent to the card reader through the RF transceiver module together with the received IDr, and the card reader receives the (IDr, IDc) returned by the mobile radio device, and confirms the mobile radio device with the identification code IDc. Correctly returned the reader ID code IDr, which is the only communication terminal of this transaction. Since the IDr encoding ensures that the identification codes of other card readers around the card reader are different at this time, the mobile radio device with the ID code IDc confirms that it has unique communication with the card reader whose ID code is IDr. At this point, the mobile radio device and the card reader implement a unique binding, and the two parties uniquely identify each other through the (IDr, Idc) combined address. The binding communication process uses RF channels for interaction without error. After the mobile radio device is successfully accessed, the distance control process is completed, and the subsequent transaction process can be performed on the RF channel until the transaction ends.

4. Transaction process: The card reader and the mobile radio device establish a reliable unique communication link through the RF channel. On the basis of the link, both parties can implement the process required for identity authentication and other transactions required for the transaction. All of these processes are performed through a fast RF channel. Since the completion of the aforementioned process ensures that access can only be completed within a predetermined distance, the entire transaction process is also within a limited range of short-range communication.

The invention is further illustrated by the following examples.

Figure 8 is a structural diagram of a short-range communication system in an embodiment of the present invention. As shown in Fig. 8, the system consists of two parts: a card reader device 100 and a mobile radio device 200, which is placed inside the mobile terminal and interacts with the terminal through the mobile terminal communication interface.

The card reader 100 is composed of the following modules: the first main processor 101 is responsible for the low frequency and high frequency control of the card reader and other protocol processing, and the first main processor 101 is directly connected to the external communication interface through the interface circuit 102 or directly. The encoding circuit 108 is responsible for bit-by-bit encoding of the low-frequency frame data, and the modulating circuit 107 is responsible for modulating the encoded-output symbol stream to form a modulated signal to the driving circuit 106, and the encoded signal is directly sent to the driver without modulation. The circuit 106; the driving circuit 106 is responsible for driving the low-frequency transmitting coil 105 to generate a low-frequency alternating magnetic field 301; and the low-frequency transmitting module consisting of the low-frequency transmitting coil 105, the driving circuit 106, the modulating circuit 107 and the encoding circuit 108, and the transmission field strength value thereof It can be modified and set; the low frequency transmitting coil 105 is generally composed of a plurality of turns of a specific shape of the coil; the RF transmitting and receiving circuit 103 receives and transmits the RF signal through the RF antenna 104.

The mobile radio device is composed of the following modules: a second main processor 201, which is responsible for the control of low frequency and radio frequency modules and other protocol processing, and is also responsible for communication with the mobile terminal; the SIM/TF/SD card module 202 is a mobile terminal. The SIM/TF/SD card body module, which module is determined by the card type; the low frequency magnetic induction circuit 207 is composed of a PCB coil, an enameled wire coil, a Hall device or other circuit components capable of sensing a magnetic field change, and is responsible for sensing the low frequency. The alternating magnetic field signal 301 is converted into an electrical signal; the low frequency amplifying circuit 206 is responsible for amplifying the electrical signal detected by the low frequency magnetic induction circuit to obtain a low frequency magnetic detecting voltage signal 303; the threshold determining and demodulating circuit 205 is responsible for the low frequency magnetic detecting voltage signal 303. The preset threshold Vt is determined. If the threshold Vt is not reached, the card is not demodulated, and the signal is demodulated. The demodulated signal is sent to the second main processor 201. The RF transceiver circuit 203 passes through the RF antenna. 204 is responsible for completing RF two-way communication with the RF transceiver module of the card reader.

The system performs the distance detection and control without calibration by using a preset threshold determination method, that is, the card reader 100 transmits the low frequency alternating magnetic field signal 301 according to the preset transmission parameter, and the mobile radio frequency device 200 receives the magnetic field signal and converts it into a low frequency magnetic field. The voltage signal 303 is detected, and it is judged whether the terminal enters a preset effective distance interval by a preset threshold Vt. The threshold Vt is the same for all terminals, and does not need to be modified for different terminals (so-called calibration). The unique binding of the card reader 100 and the mobile radio frequency device 200 is completed by the combination of the low frequency one-way communication and the RF two-way communication, that is, the card reader 100 transmits the unique identifier IDr to the mobile radio device 200 by using the low frequency one-way channel. The mobile radio device 200 transmits the card's own unique identifier IDc to the card reader 100 through the RF bidirectional channel, and the card reader 100 compares the correctness of the IDR, thereby implementing the card reader 100 and the mobile radio device 200. The only binding. After the binding, the two-way high-speed and large-volume communication is completed through the RF channel.

In this embodiment, the specific working process of the short-range communication system is as follows:

(1) First, select the basic parameters of the system operation, including the RF frequency point, the uncalibrated low frequency frequency point f0, the reader transmission parameter, and the receiving voltage threshold Vt of the mobile RF device.

1. RF frequency selection

The frequency of the above RF communication usually adopts the 2400~2483MH 2.4G ISM frequency band to achieve high-speed communication and good penetration to the terminal, and other frequency points such as 433MHz, 900MHz, 5GHz, etc. can also be used.

2. No calibration low frequency frequency f0 selection

The above method is used to determine the system low frequency uncalibrated working frequency point f0. For a typical GSM mobile communication terminal, the distance control in the range of 0 to 10 cm is to be realized, and the f0 frequency point is usually less than 10 kHz, and the typical values include 500 Hz, 1 kHz, 1.5 kHz, 2 kHz, 2.5KHz, 3KHz, 5KHz, etc.

3. Selection of the reader's transmission parameters

The transmission parameters mainly include the modulation mode, the coding mode and the amplitude of the transmitted magnetic induction intensity Br.

Figure 9 is a schematic diagram of the low frequency transmitting part of the card reader. Referring to Fig. 8, the low frequency transmitting circuit of the card reader is composed of a driving circuit 106, a modulating circuit 107 and an encoding circuit 108, and the low frequency modulated signal driven by the driving circuit 106 is output to the low frequency transmitting coil 105.

Modulation circuit 107 can take a variety of modulation methods:

1) Carrier modulation mode modulation: the baseband signal generated by the encoding circuit 108 is modulated by the modulation circuit 107, and the carrier can be a sine wave, a square wave, a triangle wave, etc. The modulation can be switched frequency shift keying OOK, phase shift keying, frequency Shift keying FSK or the like, the modulated signal is loaded into the low frequency transmitting coil 105 through the driving circuit 106;

2) Carrierless direct baseband transmission: the baseband signal generated by the encoding circuit 108 is directly loaded into the low frequency transmitting coil 105 through the driving circuit 106;

3) Other modulation methods: Since the system of the present invention uses the threshold judgment method for distance control, the modulation method should not adopt amplitude modulation, and any modulation method capable of keeping the detection voltage amplitude in the mobile radio frequency device substantially constant during the transmission process can be used for the present invention. Invented near field communication system;

The encoding circuit 108 can employ a variety of encoding methods:

1) Manchester coding: Bit 1 is encoded as two symbols 01 and bit 0 is encoded as 10.

2) Differential Manchester coding: There are two sequences of bit symbols: 01 and 10, bit 1 is encoded differently from the previous symbol sequence, bit 0 is the same, or vice versa.

3) Other coding methods: Since the system of the present invention uses the threshold judgment method for distance control, the low-frequency modulation signal must maintain a stable average value, and the encoded sequence cannot contain a DC component, and any coding method in which the average DC component after coding is zero can be used. A near field communication system for use in the present invention.

After determining the modulation mode and the coding mode, the aforementioned method is used to determine the amplitude of the magnetic induction intensity Br of the card reader. The process of adjusting Br is actually a process of adjusting the parameters such as the number of turns of the coil, the wire diameter, and the shape.

4. Mobile RF device receiving voltage threshold Vt selection

The card receiving threshold voltage Vt is determined by the aforementioned method.

The selection of the above parameters is one-off. Once selected, there is no need to change the work.

(2) Secondly, the system workflow after the work parameters are determined is as follows: Step A100: Distance measurement and control process. The first main processor 101 of the card reader 100 generates a data frame containing the unique identification code IDr of the card reader, and sends it to the encoding circuit 108 for encoding. The encoded signal is modulated by the modulation circuit 107 or directly sent to the driver without modulation. In the circuit 106, the modulation voltage is sent to the low-frequency transmitting coil 105 for transmission. By setting the frame format, the modulation and coding mode and the driving capability in advance, the transmitting coil 105 continuously transmits the low-frequency intersection of the specified parameters according to the frame format at the set intensity Br. The variable magnetic field signal 301. When the mobile terminal is placed around the card reader, the low frequency alternating magnetic field signal 301 penetrates the terminal to reach the internal mobile radio frequency device 200, and the low frequency magnetic induction circuit 207 in the mobile radio frequency device 200 detects the low frequency magnetic signal and converts it into an electrical signal. After being amplified by the low frequency amplifying circuit 206, the low frequency magnetic detecting voltage 303 is obtained. When the amplitude of the voltage is less than (or greater than) the preset receiving voltage threshold value Vt, the card is not allowed to be swiped; when the magnitude of the voltage is greater than or equal to (or less than or equal to) The received voltage threshold value Vt indicates that the terminal enters the predetermined effective card swipe range of the card reader, and the low frequency receiving circuit starts the decoding process to obtain the unique identification code IDr of the card reader. On the other hand, there is a one-to-one correspondence between the voltage signal after the magnetic field conversion in the mobile radio frequency device and the distance between the card reader and the mobile radio frequency device, and the relationship is determined by the voltage-distance curve, and according to the corresponding relationship, The distance between the mobile radio device and the card reader is determined by the voltage, thereby indirectly determining the distance between the mobile terminal and the card reader. The above threshold Vt is the same for all terminals, and there is no need to correct for each terminal, that is, there is no need to know the calibration, so the above process is a distance measurement and control process without calibration; the frame format in step A100 is defined as follows: Figure 10 is Card reader low-frequency data frame format diagram, as shown in Figure 10, the reader low-frequency data frame is divided into the following fields: synchronization code: 8 bits, usually FFH, for frame synchronization; control field: 8 bits, Deframing information used to provide frame data, such as length, data type, etc., can be reserved for extension; IDr: N bits, reader unique identification code, specified by the control field; CRC: for the control domain, IDr For verification, a CRC checksum or other means may be employed.

The frame format described above is only an example and does not limit the frame format actually employed by the present invention. In principle, any frame format including a card reader that can uniquely recognize the card reader can be used. The unique identification code may be a random number of sufficient length, or a method in which all readers manually assign a unique code, or an identification code generated in other manners.

Step A200: The process of the mobile radio device accessing the card reader: the mobile radio device access card reader mainly includes the unique binding process of the card reader 100 and the mobile radio device 200, which actually indicates that the card reader and the mobile radio device are located. The unique binding process for mobile terminals. The internal low frequency receiving circuit of the mobile radio frequency device 200 decodes the card reader unique identification code Idr and transmits it to the first main processor 201 in the mobile radio device. The module together with the unique identification code Idc of the mobile radio device itself together with the received Idr The RF transceiver unit 203 and the RF antenna 204 in the mobile radio device are sent to the card reader 100, and the internal RF antenna 103 and the RF transceiver circuit 104 of the card reader receive the (IDr, IDc) returned by the mobile radio device, and then transmit the signal to the first A main processor 101 processes, and the first main processor 101 confirms that the mobile radio device whose identification code is IDc correctly returns the card reader IDr, which is the only communication terminal of the transaction. Since the IDr encoding ensures that the identification codes of other card readers around the card reader are different at this time, the card whose ID is IDc confirms that it has unique communication with the card reader whose ID code is IDr. At this point, the mobile radio device and the card reader implement a unique binding, and the two parties uniquely identify each other through the (IDr, Idc) combined address. The binding communication process uses RF channels for interaction without error. After the mobile radio device successfully accesses the card reader, the distance control process is completed, and the subsequent transaction process can be performed on the RF channel; the mobile radio device unique identification code IDc in step A200 is pre-stored in the non-dynamic memory of the mobile radio device. A unique identifier in the body (NVM), or a sufficiently long random number generated by a mobile radio device.

Step A300: The transaction process. The card reader 100 and the mobile radio device 200 establish a reliable unique communication link through the RF channel, on the basis of which the two parties can implement the process required for identity authentication and other transactions required for the transaction. All of these processes are done through a fast RF channel until the end of the transaction. Since the completion of the foregoing steps A100-A200 ensures that the mobile radio frequency device 200 can only complete access within a predetermined distance range, the entire transaction process is also within a limited distance to complete the transaction. The transaction process is a mature POS machine processing flow, which is not described in detail in the present invention.

The low frequency signal detecting circuit 207 in the mobile radio frequency device 200 can generally be constructed by using a PCB coil, an enameled wire coil or a Hall device. The detecting circuit is not limited to the use of these components, and in principle any sensing capable of converting a magnetic field change into an electrical signal. The device can be used for this module, the only restriction is that it can be placed inside the card.

The system of the invention realizes the distance detection and control by using the low frequency alternating magnetic field, realizes the one-way communication between the card reader and the mobile radio frequency device, realizes the reliable binding of the terminal by using the RF channel combined with the low frequency communication, and realizes the card reader by using the RF channel. High-speed data communication between mobile radio devices. It has the following characteristics: 1. It can realize reliable two-way distance communication without replacing the mobile terminal, and only need to replace the SIM card/TF/SD card inside the terminal; 2. The card reader emits low-frequency alternating magnetic field signal and moves The radio frequency device only needs to receive the magnetic field signal. Because it is one-way communication, and the card reader does not need to provide energy through the magnetic field, the receiving coil or other receiving circuit can be miniaturized enough to put the mobile radio device into the SIM card/TF/SD. Card internal; 3. Due to the weak reception signal, it is necessary to increase the amplification circuit in the mobile radio frequency device. In addition, the RF transceiver circuit is placed in the mobile RF device at the same time, and the RF transceiver circuit in the card reader realizes two-way high-speed communication. As described above, the antenna of the RF circuit is small and can be easily integrated into the SIM card/TF/SD card. .

According to the frequency point f0 selected by the method of the present invention, the system does not need to be calibrated below the frequency point. As an extension, the system works above the f0 frequency point, and it is not absolutely impossible. The possible effect is performance degradation, accuracy of distance control. The reduction, while possibly requiring a simple calibration, does not fundamentally conflict with the principles described herein, but is an extended application of performance changes.

The near field communication system of the invention realizes that the data communication distance (ie, the transaction distance) of the radio frequency communication terminal (such as the mobile phone equipped with the radio frequency SIM card) containing the mobile radio frequency device and the card reader is reliably controlled within the prescribed range, and Calibrate the terminal.

By adopting the system and method of the invention, selecting the highest frequency point f0 of the non-calibration work, and measuring and controlling the distance with the low frequency alternating magnetic field lower than f0, the influence of the structural difference between the mobile terminals can be reduced to the distance control The range of fluctuations required by the target, thus achieving uncalibrated distance control. Figure 11 is a voltage distance curve tested by a coil receiving circuit placed in various mobile terminals using a signal source to emit a constant 1 KHz magnetic field through a low frequency transmitting coil. As shown in Fig. 11, it is an example of the voltage distance curve of a plurality of typical terminals at a frequency of 1 kHz. The signal strength value is the value after the necessary amplification of the receiving antenna induced voltage, and the magnification is kept constant, and only the relative change of the intensity with the distance is concerned. It can be seen from Fig. 11 that the field strength difference between the terminals is <5 dB, and the field strength variation range of each terminal in the range of 1 to 10 cm reaches 40 dB, regardless of the fluctuation of the field strength of the reader and the detection circuit of the mobile radio device. Error, the mobile RF device uses a uniform threshold Vt to determine whether each terminal is within the target distance range. The distance control error is approximately 1 cm between the terminals, which fully meets the requirements of non-calibrated distance control.

RF IC card, RF memory card

As a party of short-range communication, a mobile radio device is usually an IC card (such as a SIM card, a UIM card, a USIM card, etc.) or a memory card (such as a TF card, an SD card, an MMC (Multi Media Card) placed in a mobile terminal). In the card), we will refer to the IC card and memory card of the mobile radio device as the radio frequency IC card and the radio frequency memory card.

Figure 12 is a structural diagram of a radio frequency IC card in an embodiment of the present invention. As shown in FIG. 12, in this embodiment, the radio frequency IC card 1200 is composed of a mobile radio frequency device and a SIM/UIM/USIM card module (which may be collectively referred to as an IC card module) 1202 and an interface module 1207. In FIG. 12, the mobile radio frequency device includes at least one low frequency magnetic induction circuit 1206, at least one low frequency amplification circuit 1215, at least one comparison circuit 1225, at least one demodulation circuit 1235, at least one decoding circuit 1245, and at least one second main processor 1201. At least one RF (radio frequency) transceiver circuit 1203 and at least one RF (radio frequency) antenna 1204, wherein the low frequency magnetic induction circuit 1206, the low frequency amplification circuit 1215, the comparison circuit 1225, the demodulation circuit 1235, the decoding circuit 1245, and the second main processor 1201 The RF transceiver circuit 1203 and the RF antenna 1204 are connected in series in series. The comparison circuit 1225, the demodulation circuit 1235 and the decoding circuit 1245 constitute a threshold determination and demodulation circuit of the mobile radio frequency device. In other embodiments of the present invention, the threshold determination and demodulation circuit of the mobile radio frequency device may not include the demodulation circuit 1235, but only the comparison circuit 1225 and the decoding circuit 1245. In Fig. 12, the low frequency amplifying circuit 1215, the comparing circuit 1225, the demodulating circuit 1235, and the decoding circuit 1245 constitute a low frequency signal receiving and processing module 1205. The second main processor 1201 is the same as the second main processor in the aforementioned mobile radio frequency device. The low frequency receiving circuit composed of the low frequency magnetic sensing circuit 1206, the low frequency amplifying circuit 1215, the threshold determining and demodulating circuit (including the comparing circuit 1225, the demodulating circuit 1235 and the decoding circuit 1245) operates in the highest selected system without calibration work. Frequency below f0. The method for determining the highest frequency f0 of the system without calibration work has been previously described, and will not be described herein. The low frequency receiving link converts the low frequency alternating magnetic field of constant amplitude or constant amplitude by magnetoelectric conversion to obtain a constant amplitude detection voltage with an error of δc dB.

The volume of different low frequency receiving links can be selected by selecting different low frequency magnetic induction circuits and amplification factors of the low frequency amplifying circuits, so that the mobile radio frequency device can be selected to be placed in carriers of different volume requirements. If the low frequency magnetic induction circuit is a coil, the volume of the low frequency receiving link depends on the conversion gain of the low frequency magnetic induction circuit and the amplification factor of the low frequency amplification circuit. The magnetoelectric conversion gain conversion formula is: K*A=Vt/B_RATEgate, where B_RATEgate is the threshold value of the magnetic induction intensity change rate, the magnetic induction intensity change rate B_RATE=dBr/dt, A is the amplification factor of the low frequency amplification circuit, and K is the low frequency magnetic induction circuit. Conversion gain; the product of the conversion gain of the low-frequency magnetic induction circuit and the amplification factor of the low-frequency amplification circuit is the system preset value corresponding to the farthest card-swapping distance of the system applied by the mobile terminal, and the far-reaching card-distance distance is the reader-discharge field at the distance The strong parameter value is B_RATEgate, and the internal detection voltage of the mobile device is just the threshold value Vt. At this time, the card is allowed to be swiped. Above this distance, the transmission field strength is continuously attenuated and less than B_RATEgate, and the internal detection voltage of the mobile device is less than Vt, and the card is not allowed to be swiped. In the above relationship, Vt and B_RATEgate are values determined by the system, so the K*A value is determined, and the volume of the coil is mainly determined by the K value. The more the number of turns of the coil, the larger the K, the larger the volume, and the magnitude of the A value to the low frequency. The volume of the amplifying circuit has essentially no effect, so the distribution of the total magnetoelectric conversion gain between K and A will determine the volume of the low frequency receive link. For example, if the mobile radio device is placed in the SIM card, the coil volume that is easy to be placed into the card is selected within the range of 1 to 20 ,, so the conversion gain of the magnetic induction circuit is first determined, and then the gain of the low frequency amplifying circuit is selected. Just fine. If the mobile radio device is placed on the terminal motherboard, this can increase the number of turns and the area of the coil, and the gain of the amplifier can be reduced. The advantage is that the signal-to-noise ratio is improved, and the disadvantage is that the volume of the low-frequency receiving link becomes larger. When the low frequency magnetic induction circuit is a coil, when the magnetoelectric conversion gain A*K of the low frequency receiving link is a preset value, changing the gain distribution of A and K can change the volume of the low frequency receiving link and the signal to noise ratio of the received signal. Increase K, decrease A, increase volume, increase signal-to-noise ratio; decrease K, increase A, decrease volume, and reduce signal-to-noise ratio.

If the magnetic induction circuit is a Hall device or a giant magnetoresistive device, the volume of the low frequency receiving link has little to do with the conversion gain of the low frequency magnetic induction circuit and the amplification factor of the low frequency amplifying circuit.

In FIG. 12, the second main processor 1201, the SIM/UIM/USIM card module 1202, the RF transceiver module 1203, the low frequency signal receiving and processing module 1205, and the interface module 1207 can be integrated into one IC (integrated body). Circuit) The internal circuit and peripheral passive components are also composed, and can also be combined into different ICs, plus peripheral passive components.

Among them, the RF antenna 1204 cannot be integrated into the IC, and the PCB antenna can be used, which is composed of the copper printed circuit of the PCB.

The low frequency magnetic induction circuit 1206 is configured to receive the low frequency magnetic field signal, convert the low frequency magnetic field signal into a corresponding voltage signal, and send it to the subsequent low frequency amplifying circuit 1215. The low frequency magnetic induction circuit 1206 can be implemented by a PCB coil, an enameled wire coil, a Hall device, a giant magnetoresistive device, or the like. In general, the signal 1302 output by the low frequency magnetic induction circuit 1206 is in a fixed linear proportional relationship with the low frequency magnetic field signal strength signal 1301 of the environment or the low frequency magnetic field signal strength signal change rate 1301, that is, 1302=1301*K, where K It is a constant, and K depends on the characteristic parameters of the low frequency magnetic induction circuit 1206. The signal 1302 output by the low frequency magnetic induction circuit 1206 may be a voltage signal or other signal such as a current. In general, the signal 1302 is a voltage signal. If the low frequency magnetic induction circuit 1206 is constructed using a Hall device or a giant magnetoresistive device, the voltage signal 1302 is proportional to the low frequency magnetic field signal strength 1301. If the low frequency magnetic induction circuit 1206 is constructed using a PCB coil or an enameled wire coil, the voltage signal 1302 is proportional to the low frequency magnetic field signal strength signal change rate 1301. A typical antenna is a ring-shaped differential amplitude constant-sensing antenna composed of the outermost ring N匝pcb of the card, and the output is a voltage signal 1302. For example, a structure of a 4" pcb copper-coil antenna applied to a SIM card is shown in Fig. 13.

The second main processor 1201 implements coordinated control processing of the entire radio frequency IC card 1200. The second main processor 1201 includes various control hardware, a program module, and a memory. The second main processor 1201 is implemented by an IC and peripheral passive components, and the main functions are implemented by the IC, and the peripheral components only serve as an auxiliary function.

The SIM/UIM/USIM card module 1202 is connected to the second main processor 1201, and has interaction with the application data between the second main processor 1201. The SIM/UIM/USIM card module 1202 is mainly implemented by an IC. The second host processor can be the same shared processor as the processor in the SIM/UIM/USIM/TF/SD/MMC card. That is, using a shared processor to do the work of the second processor and the processor in the SIM/UIM/USIM/TF/SD/MMC card at the same time.

The interface module 1207 is connected to the second main processor 1201, and the second main processor 1201 is connected to the communication interface of the mobile terminal through the interface module 1207, and performs data interaction with the mobile terminal. The interface module 1207 is implemented by an IC. In general, the second main processor 1201 and the interface module 1207 are integrated inside the same IC. The SIM/UIM/USIM card module 1202 can perform data interaction with the mobile terminal through the second main processor 1201 and the interface module 1207 to perform the functions that should be performed.

The low frequency signal receiving and processing module 1205 is connected to the second main processor 1201 and also to the low frequency magnetic sensing circuit 1206. The low frequency signal receiving and processing module 1205 receives the low frequency magnetic field signal 1302 transmitted from the low frequency magnetic induction circuit 1206, and amplifies the low frequency magnetic field signal 1302 by A times to obtain a signal 1303, that is, the signal 1303=A* signal 302. The low frequency signal receiving and processing module 1205 compares whether the signal 1303 is greater than the set threshold Vt and transmits the comparison result to the second main processor 1201. The low frequency signal receiving and processing module 1205 also decodes the data information in the signal 1303 and sends it to the second main processor 1201. The low frequency signal receiving and processing module 1205 receives the control of the second main processor 1201 and receives control information such as the threshold Vt sent from the second main processor 1201.

The RF transceiver circuit 1203 is connected to the second host processor 1201. The RF transceiver circuit 1203 is connected to the RF antenna 1204, and transmits and receives the RF signal 400 in the air through the RF antenna 1204. The RF transceiver module 1203 and the RF antenna 1204 together complete the radio frequency data communication with the card reader under the control of the second host processor 1201.

The low frequency magnetic induction circuit 1206 is connected to the low frequency signal receiving and processing module 1205, receives the low frequency magnetic field signal 1301 transmitted by the air card reader, converts it into a low frequency magnetic field signal 1302, and sends it to the low frequency signal receiving and processing module 1205 for processing.

The low frequency signal receiving and processing module 1205 is composed of a low frequency amplifying circuit 1215, a comparing circuit 1225, a decoding circuit 1245, and an optional demodulating circuit 1235. The demodulation circuit 1235 is optional. When the digital signal transmitted to the low frequency magnetic field is only subjected to baseband coding without modulation and demodulation, the demodulation circuit 1235 is not required, otherwise the demodulation circuit 1235 is required.

The low frequency amplifying circuit 1215 receives the low frequency magnetic field signal 1302 sent from the low frequency magnetic induction circuit 1206, and amplifies the low frequency magnetic field signal 1302 by A times to obtain the signal 1303. Signal 1303 is sent to comparison circuit 1225 for processing. The signal 1303 is also sent to the demodulation circuit 1235 for processing. If there is no demodulation circuit 1235, the signal 1303 is sent directly to the decoding circuit 1245 for processing. The magnetic induction threshold Bgate or the magnetic induction intensity change rate threshold B_RATEgate, the low-frequency magnetic induction circuit 1206 sensing coefficient K, the low-frequency amplification circuit 1215 amplification factor A, and the set threshold voltage signal Vt must satisfy the following relationship, that is, Bgate* K*A=Vt or B_RATEgate*K*A=Vt. The amplification factor A of the low frequency amplifying circuit 1215 can be set by software.

The comparison circuit 1225 is connected to the second main processor 1201, receives the signal 1303 sent from the low frequency amplifying circuit 1215, and compares whether the signal 1303 exceeds the threshold Vt. If the signal 1303 changes in comparison with the threshold Vt, the information of the change is sent to the information. The second main processor 1201. The threshold Vt is set by the second main processor 1201 and stored in the comparison circuit 1225. When the comparison circuit 1225 compares the signal 1303 with Vt, the Vt value can also be set by software.

The demodulation circuit 1235 is connected to the decoding circuit 1245, receives the signal 1303 sent from the low frequency amplifying circuit 1215, and the demodulated baseband signal is supplied to the decoding circuit 1245.

The decoding circuit 1245 is connected to the second main processor 1201, and receives the baseband signal sent by the low frequency amplifying circuit 1215 or the demodulating circuit 1235. After decoding, the information sent by the card reader through the low frequency magnetic field is sent to the second main processor 1201. . Decoding circuit 1245 can be implemented using the techniques of a differential Manchester decoder.

The RF memory card is composed of a mobile RF device and a TF/SD/MMC card module (which can be collectively referred to as a memory card module) and an interface module. In Fig. 12, the RF memory card can be obtained by simply replacing the SIM/UIM/USIM card module 1202 of the radio frequency IC card with the TF/SD/MMC card module. The other parts of the RF memory card are the same as those of the RF IC card. The RF memory card is not mentioned here. Figure 16 is a schematic diagram showing the structure of a 4匝pcb coil antenna applied to a TF card.

The above functions can be realized by using the above RF IC card/RF memory card:

1. Low-frequency magnetic field unidirectional data communication function

The radio frequency IC card/radio frequency memory card of the invention can receive data information in a low frequency magnetic field. The coded modulation method of the data information can use various existing mature technologies. For example, a differential Manchester coded technique can be used to directly pass the encoded differential Manchester coded baseband signal using the low frequency magnetic field rate of change.

Each fixed-length period transmits a data bit (bit). The level must change during the middle of the transmission period of one bit, but the level of the boundary between two different bits can be changed or not. . Therefore, there are only two codewords at the middle of a bit transmission period: 01, 10. Bit 1 is transmitted using a different codeword than the previous codeword. Bit 0 is transmitted, using the same codeword as the previous codeword. Figure 14 is a differential Manchester encoding format of 5bit data 11010 and a waveform diagram of field strength and coil receiving voltage. Figure 14 is a differential Manchester coding format diagram of 5bit data 11010, b is the field strength map corresponding to a, and c is the corresponding voltage waveform diagram received by the coil. As can be seen from Fig. 14, in the differential Manchester code, the difference represents 1 and the same represents 0.

2. The low-frequency alternating magnetic field with constant amplitude or constant differential amplitude is magnetically converted to obtain a constant detection voltage, and the threshold comparison function and the function of swiping are controlled.

Amplitude constant low-frequency alternating magnetic field is a low-frequency alternating magnetic field with a constant amplitude of change in magnetic induction, such as a square wave and a sine wave.

The differential amplitude constant low-frequency alternating magnetic field refers to a low-frequency alternating magnetic field whose amplitude of change in the rate of change of the magnetic induction intensity is constant, such as a triangular wave and a sine wave.

The amplitude constant (or differential amplitude constant) signal 1301 is converted into a low frequency magnetic field voltage signal 1302 via the low frequency magnetic induction circuit block 1206, the 1301 magnetic induction is Br, the magnetic induction circuit receiving sensitivity is K; then the voltage signal 1302 = K*Br or K*dBr /dt.

The low frequency amplifying circuit 1215 amplifies the voltage signal 1302 by A times to obtain a voltage signal 1303. Then, the voltage signal 1303 = A* voltage signal 1302.

Therefore, the voltage signal 1303 = K*A*Br or K*A*dBr/dt.

As long as the measured voltage signal 1303 is converted to a corresponding constant amplitude (or differential amplitude constant) signal 1301.

The comparison circuit 1225 compares whether the voltage signal 1303 is greater than Vt, and sends the comparison result information to the second main processor 1201. The second main processor 1201 determines whether the card is allowed to be swiped based on the comparison result information.

The measurement field strength of the low-frequency receiving link of the mobile radio device is errory, and the error is basically equal to the error of the radio frequency IC card/radio frequency memory card, and the error is derived from the following five aspects: a) to e):

a) error ratio eK(db) of the transform coefficient K of the sensor (low frequency magnetic induction circuit);

b) amplifier (low frequency amplifier circuit) amplification factor A error ratio eA (db);

c) comparator (comparison circuit) error ratio eO (db);

d) the amplifier (low frequency amplifier circuit) allows the equivalent input noise coefficient eN (db);

e) Other errors eC(db); these 5 errors all contain errors due to working environment factors such as temperature and voltage.

A system consisting of a card reader and a mobile terminal with a built-in mobile radio frequency device, in order to achieve the goal of no calibration distance control, distributes the fluctuation of the detection voltage at various points in the system, and the fluctuations allowed to be allocated to the mobile radio frequency device itself are called The low frequency detection voltage fluctuation range δc(db) caused by the mobile radio device. The sum of the error factors of the above five mobile radio frequency device RF IC card/RF memory card must be smaller than the error index δc(db) assigned by the system to the card. which is:

eK(db)+eA(db)+eO(db)+eN(db)+eC(db)<δc(db)

The low frequency amplifying circuit 1215 is integrated inside the card chip. Generally, the working power voltage inside the chip is on the order of 1 volt. Therefore, taking the amplitude constant detecting circuit as an example, the corresponding Vt should be on the order of 1 volt, then, Bgate*K *A should be about 1V, which requires K*A=Vt/Bgate=1 volts/Bgate. The amplification factor A of the low-frequency amplifier circuit is determined by the design of the chip design. In theory, there is a large range that can be freely selected, but once the Bgate is determined and the sensor determines K, the size of A is also determined. It is determined that A=Vt/Bgate/K, in general, Vt can take 1V, then A can take 1V/Bgate/K. In this way, the size of A is determined by other parameters, but the range of values of K allows a wider range, and as a result, the selection of the low frequency magnetic sensing circuit 1206 has great flexibility.

Since the selection of the low frequency magnetic induction circuit 1206 can have a large degree of freedom, a 4" pcb coil which is easy to implement on the card in engineering can be selected as the low frequency magnetic induction circuit 1206, see Fig. 13. Of course, sensors with other parameters can also be selected. The use of 4匝pcb coil sensor has the following advantages: 1. It is easy to implement, does not increase the structure on the card, and the card needs to be pcb; 2. The volume of the card is not increased. Thus the antenna of this solution can be implemented on the card and does not need to be connected to an antenna other than the card.

The design of the error margin δc(db) of the RF IC card/RF memory card is also an important part of the card. Using the design of this scheme, the error margin δc(db) needs to be assigned to the following five factors:

a) error ratio eK(db) of the transform coefficient K of the sensor (low frequency magnetic induction circuit);

b) amplifier (low frequency amplifier circuit) amplification factor A error ratio eA (db);

c) comparator (comparison circuit) error ratio eO (db);

d) the amplifier (low frequency amplifier circuit) allows the equivalent input noise coefficient eN (db);

e) Other errors eC(db).

For example, if the farthest allowable swipe distance Dmax is 10cm, and the swipe distance Dmin must be 5cm recently, then from the 15th figure, it can be seen that the strongest signal of 10cm is 12db, and the weakest signal of 5cm is 28db, then the total error margin There are 28-12=16db, in which only 4db error margin is allocated to the card, then δc(db)=4db. eK (db), eA (db), eO (db), eO (db), eC (db) evenly distributed, each has 0.8db. When the low frequency magnetic induction circuit 1206 uses a 4 匝 pcb coil, since the PCB production process is very mature, the dimensional error is within 0.1 mm, and the K value error is mainly determined by the area error of the coil, and the percentage error of K can be calculated. 0.1mm*0.1mm/25mm/15mm, which is about 2.67*10-5, converted to db number 20log (1+2.67*10-5)=0.0023db. Its value is much smaller than 0.8db. The error ratio eA of the amplification factor A of the low-frequency amplifier circuit is determined by the resistance ratio in the integrated circuit process. The error of the ratio is easily less than 1% under the existing process conditions, and the conversion to the db number should be 20log (1). +0.01) = 0.086db, which is also much smaller than 0.8db. Comparing circuit errors and other errors are no longer analyzed. The above error distribution and analysis show that the goal of distance control can be easily achieved by using this scheme.

In order to achieve no change of the mobile terminal, it is only necessary to replace the SIM/UIM/USIM/SD/TF/MMC card in the mobile terminal to implement credit card transaction such as electronic payment. The present invention proposes a low frequency alternating magnetic field distance control method, which is applied to include The various mobile terminals of the mobile radio device include the following steps: Precondition: The mobile device operates at a frequency point below the calibration work frequency f0 of the pre-selected system.

In step a, the received low frequency alternating magnetic field signal Br is magnetoelectrically converted, and the low frequency alternating magnetic field signal is converted into an electrical signal Vo. If Br is a low-frequency magnetic field signal with a constant amplitude, the magnetoelectric conversion formula is Vo=A*K*Br; if Br is a low-frequency magnetic field signal with a constant differential amplitude, the magnetoelectric conversion formula is Vo=A*K*dBr/dt, where K is the magnetic induction circuit gain, A low frequency amplification circuit gain, A*K is the magnetoelectric conversion gain, the gain is preset, and there is no need to change in use; there is error in the magnetoelectric conversion, that is, Vo has fluctuation, and the fluctuation range is δc(db); b. If the electrical signal Vo converted by the low frequency magnetic induction magnetic signal is greater than the preset comparison voltage signal threshold Vt, the identification identifier IDr of the card reader is decoded, enters the radio frequency communication, and the IDr is uniquely identified along with the mobile device itself through the radio frequency channel. The code IDc is transmitted to the card reader together, and the low frequency magnetic induction signal is continuously monitored; in step c, the radio frequency communication is performed, and the radio frequency communication data is split into multiple data packets and sent and received in stages, and each time the radio receiving or sending the packet is checked, whether the Vo is greater than or equal to If Vt is, continue RF communication until the transaction ends, otherwise end the RF communication of this transaction and return to step a.

The method of determining the magnetoelectric conversion gain in the step a is as follows: in step a1, the magnetic induction gain K is determined. The magnetic induction circuit, such as a coil, a Hall device and a giant magnetoresistive device, which are easy to be realized on the carrier of the mobile radio device, is selected, thereby selecting the magnetic induction gain K; in step a2, the gain A of the low frequency amplifying circuit is arbitrarily selected under the following principle

1) The magnetic induction intensity Br received by the mobile device at any position is less than the value required by the system safety specification;

2) The mobile device is placed in one or more carriers (such as mobile terminals) specified by the system, and the signal-to-noise ratio of the magnetic induction signal after magneto-electric conversion is greater than SNR at the distance that the system requires the distance to control the target. Usually SNR>5;

3) If the low-frequency magnetic induction circuit is a Hall device or a giant magnetoresistive device, it is used to detect a low-frequency alternating magnetic field signal with a constant amplitude: A*K=Vt/Bgate, where Bgate is the magnetic induction threshold; if the magnetic induction circuit is a coil, For detecting a low-frequency alternating magnetic field signal with a constant differential amplitude: A*K=Vt/B_RATEgate, where B_RATEgate is the threshold value of the rate of change of the magnetic induction intensity, and the rate of change of the magnetic induction intensity is B_RATE=dBr/dt.

If the low frequency magnetic induction circuit is a coil, the mobile radio frequency device is placed in a SIM, UIM card, USIM card, TF card, SD card or MMC card, the number of turns of the coil may be 1 to 20 匝, the amplifier gain A is greater than 100; if the low frequency magnetic induction The circuit is a coil, and the mobile device is placed in the mobile terminal. Under the condition that the above-mentioned magnetoelectric conversion gain selection method is satisfied, the number of turns of the coil is not limited, and the gain A of the low frequency amplifying circuit is not limited.

In step a, the selection and control method of the fluctuation range δc of the detection voltage of the mobile radio device is as follows: The selection method of δc is as follows: δc is a system composed of a card reader and a mobile terminal with a built-in mobile radio device in order to achieve non-calibrated distance control The goal is to distribute the fluctuations of the detection voltage at various points in the system. The allowable fluctuations allocated to the mobile radio frequency device itself are called the low frequency detection voltage fluctuation range δc(db) caused by the mobile radio frequency device. Since the working frequency of the low-frequency receiving link is very low, the factors that detect the voltage fluctuation: the low-frequency magnetic induction circuit gain error, the low-frequency amplifier amplification error, the comparison circuit error, the circuit noise, and the error caused by the circuit temperature coefficient have little effect. Therefore, the fluctuation range of the card can be determined to be relatively small, for example, 2 to 6 dB.

The control method of δc is as follows: In order to solve the problem of the difference in detected field strength between a plurality of mobile radio frequency devices, the present invention proposes an error control method based on the error control system as shown in Fig. 17, which is applied to the above mobile radio frequency device. In Fig. 17, the transmitting coil 504 in the standard card reader 505 transmits a low frequency magnetic field signal having a constant amplitude or a constant differential amplitude to the mobile radio device 501 at a fixed distance and the standard obstacle 502 at a fixed position. The mobile radio device 501 is connected to the PC via a device 503 that communicates with the card. The control method of δc includes the following steps: assuming that the maximum fluctuation range of the attenuation of the low-frequency alternating magnetic field signal by various mobile terminals applied by the mobile device is δT, the attenuation of the standard obstacle in the error control system is δT/2, the obstacle The role of the attenuation of the low-frequency alternating magnetic field received by the mobile radio frequency device is the intermediate value of various terminal attenuation.

Step 601: As shown in FIG. 17, the standard card reader transmits a low-frequency alternating magnetic field signal having a constant amplitude or a constant differential amplitude at a fixed distance and a position, and the magnetic field of the amplitude value Bgate or the differential amplitude value B_RATEgate of the system is subjected to magnetoelectric conversion. The voltage value should be a voltage signal Vo near the amplitude Vt; step 602: determine a reasonable Vo range value = (Vt - δcx / 2, Vt - δcx / 2), where δcx < δc, because δc contains a variety of fluctuations Factors, in order to simplify the error control system and method, some factors cannot be completely measured, such as temperature error, etc.; Step 603: Measure the output electrical signal Vo of the low frequency amplifying circuit in the mobile radio device, if Vo exceeds (Vt-δcx/2, Vt- In the range of δcx/2), the amplification factor A of the low-frequency amplifier circuit is adjusted by the software setting until Vo is within the above range; Step 604: The Vt value of the mobile radio frequency device is set by the software to adjust the output electrical signal Vo after the step 603.

The invention can realize the payment of the mobile terminal without calibration, and the method and the process for realizing the payment of the mobile terminal without calibration are specifically described below with reference to the examples.

The realization process has the following preconditions: Precondition 1: The intensity of the low-frequency magnetic field signal emitted by the matched card reader has been adjusted, and the spatial distribution of the field strength has met the requirements of the distance control; further, the magnetic field signal with a constant differential amplitude, The field strength threshold of Bgate is allowed to be ±26500A/m/s (26500A/m/s). If it is a 2KHz magnetic field signal, the peak value of magnetic induction is ±3.32A/m, and its peak-to-peak magnetic induction The intensity is 6.64A/m. If it is a 1KHz magnetic field signal, the peak value of magnetic induction is ±6.64A/m, and the peak-to-peak magnetic induction is 13.28A/m. Precondition 2: RF IC card/RF memory card before leaving the factory And setting a suitable threshold voltage Vt corresponding to the required swipe operation distance; further, the threshold voltage Vt corresponds to the magnetic intensity change rate of the gate strength threshold Bgate allowing the card to be ±26500 A/m/s. The peak-to-peak voltage Vt of the output voltage 1302 of the low-frequency magnetic induction circuit is 1V; when the rate of change of the magnetic induction is ±26500A/m/s, the peak-to-peak value of the output voltage of the low-frequency magnetic induction circuit is 10 0uV, then the magnification A=Vt/100uV=1V/100uV=10000; Precondition 3: The communication and card-swapping agreement between the RF IC card/RF memory card and the card reader has been specified; further, the RF IC card/ The data bit stream between the RF memory card and the card reader can be transmitted using a differential Manchester coded baseband signal of 2K serial transmission rate. The data information is transmitted in units of data frames. The encoding method of the data frame bit stream is as follows: each frame has a 9-bit sync header, the sync header is 8 bits, and the latter is 0. In the data information behind the synchronization header, one bit 0 is added after 7 consecutive 1s to distinguish the data information and the synchronization header; Precondition 4: The RF IC card/RF memory card has been installed in the mobile terminal and is ready. Do the card swiping operation; Precondition 5: The card reader is ready to continuously transmit the low frequency magnetic field signal carrying the Idr digit information of the card reader data frame; further, the data frame information Idr contains the RF module of the card reader Channel information; further, the channel information of the RF module of the card reader is a channel between 2480MHz and 2843MHz; Precondition 6: The frequency point f0 of the low frequency operation has been determined according to the foregoing steps; Precondition 7: RF IC card The amplification factor A and the threshold Vt of the low frequency amplifying circuit of the RF memory card have been set in accordance with the aforementioned error control method.

The RF IC card/RF memory card implementing the method is as described above.

The process of implementing the card swipe operation is as follows:

1. When the mobile terminal equipped with the aforementioned radio frequency IC card/radio frequency memory card is close to the card reader, the low frequency magnetic induction circuit 1206 of the radio frequency IC card/radio frequency memory card converts the low frequency magnetic field signal 1301 at the position into the low frequency magnetic field voltage signal 1302. The low frequency magnetic induction circuit 1206, the low frequency amplifier circuit 1215, and the comparison circuit 1225 are low power consumption modules, and the power supply current consumption during operation is less than 300 uA. The low frequency magnetic induction circuit 1206, the low frequency amplification circuit 1215, and the comparison circuit 1225 can operate continuously, and the consumed power supply current is not large, and has no significant influence on the standby operation time of the battery of the battery powered mobile terminal. The other modules in the RF IC card/RF memory card are in a sleep state for most of the time, and basically do not consume the power supply current;

2. The low frequency magnetic induction circuit 1206 sends the low frequency magnetic field voltage signal 1302 to the low frequency amplifying circuit 1215 in the low frequency signal receiving and processing module 1205, and the amplified voltage signal 1303 of the low frequency amplifying circuit 1215 is supplied to the comparing circuit 1225 and the decoding circuit 1245. Further, if it is a radio frequency sim card, its shape is rectangular, its size is 25mm*15mm, and the low frequency magnetic induction circuit 1206 is composed of 4 pcs of coils along the outer frame of the sim card, such a low frequency magnetic induction circuit 1206 has a constant differential amplitude of ± In the magnetic field of 26500A/m/s, a peak voltage signal of ±50uV will be sensed with a peak-to-peak value of 100uV;

3. The comparison circuit 1225 compares the voltage signal 1303 with the threshold voltage Vt and sends the comparison result to the second main processor 1201. If the comparison result is greater than Vt, the other modules of the wake-up card work together; otherwise, the other modules continue to sleep;

4. If the voltage signal 1303 is greater than the threshold voltage Vt, the second main processor 1201 controls the decoding circuit 1245 to decode the received voltage signal 1303 to obtain the card reader Idr digital information. The decoding circuit 1245 sends the decoded card reader Idr digital information to the second main processor 1201;

5. After receiving the valid card reader Idr, the second main processor 1201 finds the channel information CH, and controls the RF transceiver circuit 1203 to communicate with the card reader through the RF antenna 1204 to establish only the current card reader and The RF IC card/RF memory card can communicate with the RF communication channel CH, and the received card reader Idr is sent to the card reader through the RF communication channel;

6. The card reader determines whether the Idr received from the RF communication channel is the Idr that it sends out from the low frequency magnetic field signal. If not, the communication is rejected. If it is correct, the subsequent communication with the card is initiated until the required card swipe operation is completed. During the card operation process, the RF IC card/RF memory card and the card reader need multiple RF communication. During each RF communication process, the card must judge whether the voltage signal 1303 is less than the threshold voltage Vt. If it is less than Vt, it will end immediately. RF communication, ending the card-free operation that has not yet been completed. If the RF IC card/RF memory card interacts with the mobile terminal during the card swiping operation, the interface module 1207 can be implemented. After the card swipe operation is completed, the modules other than the low frequency magnetic induction circuit 1206, the low frequency amplifying circuit 1215, and the comparison circuit 1225 in the low frequency signal receiving and processing module 1205 continue to sleep until the voltage corresponding to the next low frequency magnetic field signal is less than 1303. Vt to a swipe operation after a change greater than Vt.

7. The implementation of the card swiping operation function of the mobile terminal is completed by the second main processor 1201, the SIM/UIM/USIM/TF/SD/MMC card module, the RF transceiver circuit 1203, and the RF antenna 1204 together with the card reader;

8. The SIM/UIM/USIM/TF/SD/MMC card module performs its proper function. When implementing its function, the second main processor 1201 and the interface module 1207 are required to exchange data with the mobile terminal.

With the present invention, it is possible to realize short-range communication without calibration, such as electronic payment.

The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

100. . . Card reader device

101. . . First main processor

102. . . Interface circuit

103. . . RF transceiver circuit

104. . . RF antenna

105. . . Low frequency transmitting coil

106. . . Drive circuit

107. . . Modulation circuit

108. . . Coding circuit

200. . . Mobile radio device

201. . . Second main processor

202. . . SIM/TF/SD card module

203. . . RF transceiver circuit

204. . . RF antenna

205. . . Threshold judgment and demodulation circuit

206. . . Low frequency amplifier circuit

207. . . Low frequency magnetic induction circuit

301. . . Low frequency alternating magnetic field

303. . . Low frequency magnetic detection voltage signal

400. . . Radio frequency signal

501. . . Mobile terminal

502. . . Low frequency receiving module

503. . . Signal strength tester

504. . . Low frequency magnetic field transmitting coil

505. . . signal source

1200. . . RF IC card

1201. . . Second main processor

1202. . . SIM/UIM/USIM card module (IC card module)

1203. . . RF (radio frequency) transceiver circuit

1204. . . RF (radio frequency) antenna

1205. . . Low frequency signal receiving and processing module

1206. . . Low frequency magnetic induction circuit

1207. . . Interface module

1215. . . Low frequency amplifier circuit

1225. . . Comparison circuit

1235. . . Demodulation circuit

1245. . . Decoding circuit

1301. . . Low frequency magnetic field signal strength signal

1302. . . Low frequency magnetic field signal

1303. . . signal

Vt. . . Threshold

Figure 1 is a voltage-distance curve tested when the coil receiving circuit is placed in various mobile terminals and the 13.56 MHz carrier is kept constant on the same 14443 POS machine;

2 is a structural block diagram of a selection system of a highest frequency f0 in which the system has no calibration work in the short-range communication method of the present invention;

Figure 3 is a schematic diagram of determining the total received detection voltage fluctuation range δ _A of the system by the distance control target (Din, Dv);

Figure 4 is a schematic diagram of a typical terminal and obstacle voltage distance curve and its fluctuation interval δ;

Figure 5 is a voltage distance curve of five typical mobile terminals when the frequency f is 3.3KHz;

Figure 6 is a voltage waveform diagram of a received voltage signal when the unmodulated direct baseband is transmitted and a received voltage signal when the sinusoidal FSK is modulated detected inside the mobile radio frequency device;

Figure 7 is a schematic diagram of a calculation method of a reference voltage distance curve;

Figure 8 is a structural diagram of a short-range communication system in an embodiment of the present invention;

Figure 9 is a schematic diagram of the low frequency transmitting part of the card reader;

Figure 10 is a schematic diagram of the format of the low frequency data frame of the card reader;

Figure 11 is a voltage distance curve of the coil receiving circuit placed in various mobile terminals and tested by a signal source through a low frequency transmitting coil to emit a constant 1 KHz magnetic field;

Figure 12 is a structural diagram of a radio frequency IC card in an embodiment of the present invention;

Figure 13 is a schematic view showing the structure of a 4匝pcb copper-copper coil antenna applied to a SIM card;

Figure 14 is a differential Manchester encoding format of 5bit data 11010 and a waveform diagram of field strength and coil receiving voltage;

Figure 15 is a constant amplitude map received by the sim card in the mobile terminal of the low frequency magnetic field of 1 KHz;

Figure 16 is a schematic diagram showing the structure of a 4匝pcb coil antenna applied to a TF card;

Figure 17 is a block diagram of the error control system.

1200. . . RF IC card

1201. . . Second main processor

1202. . . SIM/UIM/U SIM card module (IC card module)

1203. . . RF (radio frequency) transceiver circuit

1204. . . RF (radio frequency) antenna

1205. . . Low frequency signal receiving and processing module

1206. . . Low frequency magnetic induction circuit

1207. . . Interface module

1215. . . Low frequency amplifier circuit

1225. . . Comparison circuit

1235. . . Demodulation circuit

1245. . . Decoding circuit

1301. . . Low frequency magnetic field signal strength signal

1302. . . Low frequency magnetic field signal

1303. . . signal

Claims (20)

A mobile radio frequency device comprising: an RF antenna for communicating with a radio frequency reader through a radio frequency channel; and a magnetic detector for detecting a magnetic signal, wherein the magnetic detector is based on the detected magnetic signal Controlling a communication distance of the radio frequency channel, and wherein the magnetic detector operates at a frequency lower than a pre-selected highest system operating frequency f0, so that the radio frequency device is installed in different mobile terminals without communication range Perform a substantial calibration. The mobile radio frequency device of claim 1, wherein the communication distance is controlled by a gain of the magnetic detector, and wherein a gain of the magnetic detector is related to a size of the magnetic detector. The radio frequency device according to claim 2, wherein the magnetic detector comprises: a magnetic induction coil having a conversion gain; and a low frequency amplification coil having an amplification factor, wherein a product of the conversion gain and the amplification factor corresponds to The system-specified maximum communication distance between the mobile terminal where the radio frequency device is located and the radio frequency reader. The radio frequency device according to claim 3, wherein the size of the magnetic induction coil depends on the conversion gain and the amplification factor, and wherein the magnitude of the magnetic induction coil increases as the conversion gain increases, and decreases with the amplification factor. And increase. According to the radio frequency device described in claim 1, wherein f0 is in a super frequency band of 300 Hz to 3 kHz, a very low frequency band of 3 kHz to 30 kHz, or a low frequency band of 30 kHz to 300 kHz. The radio frequency device according to claim 5, wherein f0 ranges from 300 Hz to 50 kHz. The radio frequency device according to claim 6 wherein f0 is 500 Hz, 1 kHz, 1.5 kHz, 2 kHz, 2.5 kHz, 3 kHz, 4 kHz, 5 kHz, 10 kHz, 20 kHz, or 30 kHz one. The radio frequency device according to claim 1, further comprising a comparison circuit for comparing the electrical signal converted into the detected magnetic signal with a preset threshold value Vt. The radio frequency device according to claim 8 of the patent application, further comprising a decoding circuit. The radio frequency device according to claim 9, further comprising a demodulation circuit, wherein the comparison circuit, the demodulation circuit and the decoding circuit are connected in series. The radio frequency device according to claim 10, further comprising: a radio frequency transceiver connected to the radio frequency antenna; and a processor for processing the radio frequency signal received through the radio frequency channel, and the electrical signal is detected by the radio frequency The magnetic signal is transformed. The radio frequency device according to claim 1, wherein the magnetic detector is a PCB coil, an enameled wire coil, a Hall device, or a giant magnetoresistive device. The radio frequency device according to claim 1, wherein the radio frequency device is installed on a SIM card, a UIM card, a USIM card, a TF card, an SD card, or an MMC card, or with a SIM card, a UIM card, a USIM card. A TF card, an SD card, or an MMC card shares a processor. The radio frequency device of claim 13, wherein the radio frequency device is within the mobile terminal, and wherein the mobile terminal is a mobile phone, a personal digital assistant (PDA), or a notebook computer. A method for controlling a frequency communication distance between a mobile terminal equipped with a mobile radio frequency device and a radio frequency card reader, wherein the radio frequency mobile device comprises: an RF antenna for communicating with a radio frequency reader through the radio frequency channel; and a a magnetic detector for detecting a magnetic signal from a radio frequency reader and converting the magnetic signal into an electrical signal; and wherein the method comprises: utilizing the detected magnetic signal to control a communication distance; and wherein the magnetic detector is lower than Working at a pre-selected frequency below the highest system operating frequency f0 allows the RF unit to be installed in different mobile terminals without substantial calibration of the communication range. The method according to claim 15 further includes: (a1) determining a distance control target (Din, Dv) of the system, wherein Din indicates that a selected group of selected terminals equipped with the mobile radio device are in reading with the radio frequency. The distance between the card exchange information is 0~Din; Dv represents the distance fluctuation range, so that the distance is allowed to be traded within the range of Din~(Din+Dv), and the transaction is prohibited after the distance exceeds Din+Dv; (a2) determined by the The detected fluctuation range δ _R of the electrical signal converted by the magnetic signal, wherein δ _{R is} caused by the radio frequency reader; (a3) determining the fluctuation range δ _{C of the} electrical signal, wherein δ _{C is} caused by the mobile radio frequency device itself; (a4) Test the electrical signal-distance curve of various typical terminals and obstacles at frequency f, where f is an ultra-low frequency range of 300 Hz to 3 kHz, a very low frequency range of 3 kHz to 30 kHz, or a low frequency range of 30 kHz to 300 kHz; (a5 Determine the fluctuation range δ _{A of the} electrical signal according to the range of the control target value (Din, Dv), where δ _A is the voltage having the slope of the average field strength decay curve obtained from the electrical signal-distance curves of various typical terminals and obstacles Distance curve The difference between the electrical signal corresponding to the Din point and the electrical signal corresponding to the (Din+Dv) point; (a6) determining the electrical signal fluctuation range δ _T , where δ _{T is} caused by the attenuation characteristic of the mobile terminal, and δ _T = δ _A -δ _R -δ _C ; (a7) Calculate the maximum difference δ at various distance points of various typical terminals and obstacles within the distance control range. If δ is greater than δ _T , decrease the frequency f and return to step (a4) If δ is smaller than δ _T , the frequency f is increased and the step (a4) is returned; if δ is equal to δ _T , f is equal to f0. The method according to claim 15 further comprises: (a) performing a magneto-electric conversion on the detected magnetic field signal (Br) to convert the Br into an electrical signal Vo; and when Br is a constant amplitude low frequency intersection When changing the magnetic field signal, Vo=A*K*Br; when Br is a low-frequency alternating magnetic field signal with a constant differential amplitude, Vo=A*K*dBr/dt, where K is the magnetic detector gain and A is the electrical signal. Low frequency amplification gain, A*K is the preset magnetic-to-electric conversion gain; (b) If Vo is greater than the preset threshold Vt, the RFID reader's identification number (IDr) is decoded, the RF channel is established, and the IDr is The unique identification code IDc of the mobile radio frequency device is sent to the radio frequency card reader through the radio frequency channel, and continuously monitors the magnetic field signal; (c) splitting the radio frequency communication data into multiple data packets to respectively send or receive the data packets, and check Each RF packet received or transmitted is judged whether its corresponding Vo is greater than Vt. If Vo>Vt, the radio communication is continued until the transaction is completed; otherwise, the RF communication of the transaction is ended and the process returns to step (a). According to the method of claim 17, further comprising the step of determining A*K: (i) selecting a low frequency magnetic induction circuit for the mobile terminal equipped with the mobile radio frequency device to determine K; (ii) according to the following principles Selected A: 1) When the mobile terminal is placed at any distance from the RF reader, Vo is less than the value specified by the safety standard; 2) Vo's signal-to-noise ratio (SNR), even at the maximum distance allowed for communication, Greater than the specified value; 3) If the magnetic detector is a Hall device or a giant magnetoresistive device, A*K=Vt/Bgate, where Bgate is the magnetic induction threshold; if the magnetic detector is a coil, then A*K= Vt/B_RATEgate, where B_RATEgate is a threshold of the rate of change of the magnetic induction intensity, wherein the rate of change of the magnetic induction intensity is B_RATE=dBr/dt. The method according to claim 18, further comprising: controlling the electrical signal fluctuation δc converted from the detected magnetic signal to be in the range of 2 to 6 dB. The method according to claim 19, further comprising: selecting Vo in the vicinity of Vt; determining the range of Vo as (Vt - δcx / 2, Vt - δcx / 2), wherein δcx < δc, measuring Vo, if Vo exceeds the above For the range, then A is corrected until Vo is within the range; and the value of Vt is set to Vo that has been calibrated within the range.