TWI549063B - A card reader - Google Patents

Description

Card reader

The present invention relates to the field of communications, and in particular, to a card reader.

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 radio frequency SIM card is embedded in the mobile terminal, the radio frequency signal can still be transmitted from the mobile terminal, and the industry mainstream RF (Radio Frequency) transceiver chip is used in the card reader. The RF signal of most mobile terminals can be reliably received without additional amplification, so that the mobile terminal can 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 Severely dry In order to achieve good communication effect of near-field communication, it is necessary to customize the mobile phone to optimize the 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 card reader that enables a card transaction such as electronic payment for a mobile terminal having various short-range communication functions without calibration.

In order to solve the above technical problem, the present invention provides a card reader comprising at least one low frequency transmitting coil, at least one driving circuit, at least one encoding circuit, at least one first main processor, at least one radio frequency transceiver circuit and at least one radio frequency antenna. The low frequency transmitting coil, the driving circuit, the encoding circuit, the first main processor, the radio frequency transceiver circuit, and the radio frequency antenna are connected in series; wherein the low frequency transmitting coil, the driving circuit, and the encoding circuit form a low frequency transmitting link The preselected system has no frequency below the highest frequency f0 of the calibration operation; the card reader emits a preset low frequency alternating magnetic field signal having a constant amplitude or a constant differential amplitude, the amplitude value of the low frequency alternating magnetic field signal corresponding to the set The physical communication distance, the error of the amplitude of the low-frequency alternating magnetic field signal is less than the preset error value δ _R , wherein the typical range of δ _R is <4 dB; further, the card reader may further have the following features, the card reader A modulation circuit is further provided between the driving circuit and the encoding circuit.

Further, the card reader may further have the following features, and the driving circuit includes an adjusting circuit.

Further, the above card reader may also have the following features, the driving circuit is composed of a DAC, an operational amplifier and a resistor connected in series.

Further, the card reader may further have the following features: the low frequency transmitting coil is an enameled wire coil or a PCB coil.

Further, the card reader may further have the following feature: the number of turns of the low frequency transmitting coil is greater than 10 turns.

Further, the card reader may further have the following feature: the low frequency transmitting coil has a number of turns of 50 to 500 turns.

Further, the card reader may further have the following features: the low frequency transmitting coil is filled with a ferrite core or a core.

Further, the card reader may further have the following feature, the cross section of the area enclosed by the low frequency transmitting coil includes at least a circular area of 3 cm in diameter or a square area of 3 cm * 3 cm.

Further, the card reader may further have the following feature: the area surrounded by the low frequency transmitting coil is greater than 10 square centimeters.

Further, the card reader may further have the following features: the area surrounded by the low frequency transmitting coil is 20-1000 square centimeters.

Further, the card reader may further have the following features, and further includes a local magnetic field strength detecting device.

Further, the card reader may further have the following features: the local magnetic field strength detecting device is composed of a sequentially connected controller, a sampling circuit, an amplifying circuit and a low frequency receiving coil.

Further, the above card reader may further have the following features, and the controller is integrated in the first main processor.

Further, the card reader may further have the following feature, the preset error value δ _{R of the} amplitude of the low-frequency alternating magnetic field signal is less than 4 dB.

In order to solve the above technical problem, the present invention provides a method for determining a highest frequency f0 of a system without calibration work in any of the above-mentioned card readers, comprising the following steps: Step a1, determining a 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 represents that all terminals loaded with the mobile radio frequency device within the range of 0~Din ensure that the card can be swiped, Dv represents the range of distance fluctuation, and the distance is Din. ~(Din+Dv) is allowed to swipe in the range, 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 movement The fluctuation range of the detection voltage caused by the radio frequency device itself is δ _C ; in step a4, the voltage distance curve of each typical terminal and the obstacle is tested at the f frequency; step a5, the distance control target (Din, Dv) determines the detection in the mobile radio frequency device voltage fluctuation range of δ _a, δ _a each having an average voltage equal to the distance field voltage terminal and a typical curve obtained obstacles strong attenuation slope of the curve The difference between the voltage value from Din point on the curve corresponding to the voltage value (Din + Dv) the corresponding point; step a6, determining the fluctuation range of the mobile radio apparatus by the terminal due to the detection voltage δ _T, δ _T represents a terminal attenuation The characteristic voltage fluctuation range in the mobile radio frequency device caused by the characteristic, δ _T = δ _A - δ _R - δ _C ; Step a7, calculate the maximum field strength difference δ at each distance point between the typical terminal and the obstacle within the distance control range If δ is greater than δ _T , the frequency f is decreased, and step a4 is turned; if δ is less 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 of the system without calibration work. F0.

In order to solve the above technical problem, the present invention provides a low frequency alternating magnetic field distance control method, which is applied to the card reader of any of the above, comprising the following steps: Step a, transmitting a predetermined emission through a low frequency transmission channel a low-frequency alternating magnetic field signal of the parameter, wherein the signal includes an identifier IDr of the card reader, and the predetermined transmission parameter includes a highest frequency f0, a coding mode, a modulation mode, and a constant field strength parameter of the system without calibration work; The channel waits to receive information from the terminal containing the mobile radio device; in step b, the radio channel receives the information of the terminal containing the mobile radio device, and the information includes the identifier IDr of the card reader returned by the terminal and the identification code of the terminal itself. IDc, decode IDr and IDc, compare whether the returned IDr is the same as the IDr sent. If the same, the subsequent RF communication realizes the unique binding communication between the reader and the terminal through the combined address of (IDr, IDc), otherwise communication In error, the RF channel continues to wait until it receives the correct data; at the same time the low frequency channel continues to transmit low of the predetermined transmission parameters. An alternating magnetic field signal; step C, by a radio frequency channel for communication transactions until the transaction is completed.

In order to solve the above technical problem, the present invention provides a method for selecting a transmission parameter in the low frequency alternating magnetic field distance control method described above, comprising the following steps: step a1, selecting a constant field strength mode, that is, a constant field strength parameter, field strength The constant mode includes constant peak field strength amplitude and constant differential field strength amplitude, selecting peak field strength constant to perform step a2, selecting differential field strength constant to perform step a3, and the amplitude error of the constant field strength parameter is less than the preset error value δ _R ; In step a2, under the condition that the peak field strength is constant, the coding mode, the modulation mode, and the driving voltage waveform are selected, and the target value of the low frequency magnetic field strength is determined, thereby selecting the driving voltage amplitude, the adjustment parameter, the low frequency transmitting coil resistance, and the low frequency transmitting coil lap. Measuring whether the low-frequency magnetic field strength meets the predetermined low-frequency magnetic field strength target value under the selected parameter, if yes, the transmission parameter selection is completed, and the process ends, otherwise the drive circuit and the low-frequency transmission coil parameters are re-adjusted until the measured low-frequency magnetic field strength meets the predetermined low-frequency magnetic field strength. Target value; step a3, in differential Under strong constant amplitude conditions, select the encoding mode, modulation mode, driving voltage waveform, determine the low frequency magnetic field strength target value, and select the driving voltage amplitude, adjustment parameters, low frequency transmitting coil resistance, low frequency transmitting coil turns, and then measure the selected parameters. Whether the low-frequency magnetic field strength meets the predetermined low-frequency magnetic field strength target value, if yes, the transmission parameter selection is completed, and ends, otherwise the drive circuit and the low-frequency transmission coil parameters are re-adjusted until the measured low-frequency magnetic field strength meets the predetermined low-frequency magnetic field strength target value.

In order to solve the above technical problem, the present invention provides a self-adjusting error correction method for a card reader, which is applied to any of the aforementioned card readers with a local magnetic field strength detecting device, and includes the following steps: Step 1. Setting a card reader The measurement target Hs and the error range He of the local magnetic field strength detecting device, wherein He is smaller than the preset error value δ _R , the error correction field strength range under the local magnetic field strength detecting device of the card reader is [Hs-He, Hs+He] Step 2: When testing the card reader, the card reader emits a low frequency magnetic field signal, and the local magnetic field strength detecting device compares the magnetic field strength of the currently received low frequency magnetic field signal, adjusts the emission adjustment circuit on the card reader, and makes the card reader The magnetic field strength is within the set error correction field strength range [Hs-He, Hs + He].

In order to solve the above technical problem, the present invention provides an error correction system applied to the card reader according to any of the above, wherein the error correction system includes a card reader to be tested and a set height above the card reader to be tested. Magnetic field strength detecting device.

In order to solve the above technical problem, the present invention provides an error correction method for a card reader based on the error correction system of the above card reader, characterized in that it comprises the following steps: Step 1, setting a measurement target Hs of the magnetic field strength detecting device and For the error range He, the error correction field strength range of the card reader under the standard magnetic field strength detecting device is [Hs-He, Hs+He], where He is less than the preset error value δ _R ; Step 2, in the test When the card reader is in use, the card reader under test transmits a low frequency magnetic field signal, and the magnetic field strength detecting device compares the magnetic field strength of the currently received low frequency magnetic field signal, and adjusts the emission adjustment circuit on the card reader under test to make the card reader under test The magnetic field strength is within the set error correction field strength range [Hs-He, Hs + He].

In order to solve the above technical problem, the present invention provides a method for detecting an interference card reader. When a legal card reader works, it searches for a low frequency or radio frequency signal nearby, and decodes the searched low frequency or radio frequency signal to determine the low frequency or Whether the information carried in the RF signal contains the unique identification code of the legal card reader. If it is included, it means that there is no interference with the card reader nearby, otherwise it will interfere with the card reader.

Further, the foregoing method for detecting an interference card reader may further have the following feature: the legal card reader further detects a signal strength of the received low frequency or radio frequency signal, and determines, according to the signal strength, itself and the nearby interference card reader. Distance, if the nearby interference card reader is set The alarm is within a certain safe distance.

The card reader of the present invention enables card swiping transactions such as electronic payment without requiring calibration for various mobile terminals having short-range communication functions.

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 view of the card reader in the embodiment of the present invention; and FIG. 13 is a structural view of the driving portion in FIG. 12; Schematic diagram of a typical form of a direct current or alternating magnetic field having a constant peak field strength; Fig. 15 is a schematic diagram showing a typical form of a low frequency alternating magnetic field having a constant differential field strength; and Fig. 16 is a flow chart for selecting a transmission parameter of a card reader in an embodiment of the present invention; Fig. 17 is a diagram showing an error control system of the card reader; Fig. 18 is a structural diagram of a card reader with an error control device according to an embodiment of the present invention.

100‧‧‧ card reader

101‧‧‧First main processor

102‧‧‧Interface circuit

103‧‧‧RF transceiver circuit

104‧‧‧RF antenna

105‧‧‧Low frequency transmitting coil

106‧‧‧Drive circuit

107‧‧‧ Circuitry

108‧‧‧Code Circuit

200‧‧‧Mobile RF 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

501‧‧‧Mobile terminal

502‧‧‧Low frequency receiving module

503‧‧‧Signal Strength Tester

504‧‧‧Low frequency magnetic field transmitting coil

505‧‧‧Signal source

1100‧‧‧RF Transceiver Section

1101‧‧‧ Controller

1102‧‧‧RF Transceiver

1103‧‧‧RF antenna

1200‧‧‧Low frequency magnetic field emission part

1201‧‧‧Code Circuit

1202‧‧‧Modulation circuit

1203‧‧‧Drive section

1204‧‧‧Low frequency transmitting coil

1213‧‧‧DAC

1223‧‧‧Operation

1233‧‧‧resistance

1400‧‧‧ Error correction section

1401‧‧‧Sampling circuit

1402‧‧‧Amplification circuit

1403‧‧‧Low frequency receiving coil

1701‧‧‧Magnetic field strength measuring device

1702‧‧‧Revised card reader

F0‧‧‧ frequency

Vt‧‧‧ threshold

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 view of the card reader in the embodiment of the present invention; and FIG. 13 is a structural view of the driving portion in FIG. 12; Schematic diagram of a typical form of a direct current or alternating magnetic field having a constant peak field strength; Fig. 15 is a schematic diagram showing a typical form of a low frequency alternating magnetic field having a constant differential field strength; and Fig. 16 is a flow chart for selecting a transmission parameter of a card reader in an embodiment of the present invention; Fig. 17 is a diagram showing an error control system of the card reader; Fig. 18 is a structural diagram of a card reader with an error control device according to an embodiment of the present invention.

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 completes the card reader and the mobile radio device by the combination of the low frequency one-way communication and the RF two-way communication The unique binding, after binding, through the RF channel to complete two-way high-speed large data volume communication. 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 specified:

Step a, the card reader transmits a low frequency alternating magnetic field signal according to a preset transmission parameter, where the low frequency alternating magnetic field signal carries the identity identification information of the card reader, wherein the transmission parameter includes 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; wherein the identity information may be an 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 a distance control target (Din, Dv), wherein Din indicates that all terminals in the range of 0~Din ensure that the card can be swiped, Dv represents the range of distance fluctuation, and the distance is allowed to be swiped within the range of Din~(Din+Dv). More than Din+Dv range is not allowed to swipe; for example (5cm, 5cm) means that all terminals below 5cm ensure that the card can be swiped, 5cm~10cm allow swiping, and more than 10cm can not swipe. The distance control target is determined by the specific application. (0~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 obstacle at the f frequency, wherein the f frequency is in any of the ultra 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 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 performed, 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 choose the standard of different materials Shapes of plastic, aluminum, copper, iron, stainless steel and other mobile terminal common materials, placed between the card reader and the mobile radio device as an equivalent obstacle measurement attenuation effect of the mobile terminal attenuation characteristics.

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.

At this point, in the case of limiting the distance control target, the system has no calibration frequency of the highest frequency f0 It is sure. 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, 5cm), the range of the system 0~10cm distance voltage is about 40dB, and the detection voltage fluctuations in the mobile RF device caused by the reader and mobile radio device are 4 dB, ie 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 may select any modulation mode with no change in amplitude. For example, the carrier may adopt a sine wave, a pulse, a triangular wave, etc., and the modulation mode may be selected as an open key control. Method (OOK), phase shift keying method or frequency shift keying method (FSK); when using no modulation method, the encoded baseband signal is directly driven by the transmitting coil by the driving circuit; in step a13, the selected transmitting magnetic induction intensity is selected. The value 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 radio device. The mobile terminal is placed at a distance from the card reader at a distance far from the control target, that is, Din+Dv. If the mobile radio 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 reader emits A magnetic field signal having a constant amplitude of change in magnetic induction intensity; if the mobile radio frequency 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 whose amplitude of the magnetic induction intensity change rate (ie, the differential amplitude) is constant, 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. And 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, selecting the emission amplitude value Bgate or the differential amplitude value B_RATEgate, so that Vr/Vn>SNR, SNR is the mobile radio frequency device Signal to noise ratio. The choice of SNR value is usually as large as possible, but too large will cause the reader to transmit too much power and achieve difficulty. Typical values can be SNR=10. When the SNR is determined, Br is determined by the above method. According to different types of magnetic induction circuits selected by the system, the Br parameter values are divided into two types. The Hall device and the giant magnetoresistive device receiving system are magnetic induction intensity amplitude thresholds Bgate, coil receiving system. For 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 that are equipped with the mobile radio frequency device; in step b, the preset voltage threshold Vt passes through the following steps 201 to 203 The determination is based on the premise that it is determined that the reader transmitter and the mobile radio device receive no fluctuations, or that 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 a voltage distance curve of the terminal and the obstacle, wherein the transmission parameter includes a frequency, a modulation mode, a coding mode, and a transmission magnetic induction intensity amplitude Br of the low frequency alternating magnetic field signal; and step 202, obtaining a reference voltage distance curve, and the reference voltage distance curve is The intermediate value of the typical terminal and obstacle curve, the voltage amplitude from the upper and lower boundaries of the typical terminal curve is 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;

Step d, the card reader receives the information transmitted by the mobile radio device through the radio frequency channel, and compares 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, the identity information and the mobile radio device are identified by themselves. Combination of identity information as a group The address is combined with the mobile radio device to perform a card transaction 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 near field communication system of the present invention includes 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, where the low frequency alternating magnetic field signal carries identity information of the card reader, wherein the transmission parameter includes a frequency of the low frequency alternating magnetic field signal, and the frequency is equal to Or the maximum 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, and compare whether the identity information of the card reader in the information is consistent with the identity information of the card, if consistent The combination of the identity information of the identity and the identity information of the mobile radio device is used as a combined address, and the mobile radio device performs the card transaction through the radio frequency channel; the mobile radio device is configured to receive and detect the card reader at each distance point. Transmitting the low-frequency alternating magnetic field signal and amplifying the voltage signal with a constant amplitude corresponding to the distance, and determining whether the terminal loaded with the mobile radio frequency device enters a preset effective distance interval by using a preset voltage threshold Vt, wherein The voltage threshold Vt is the same for all terminals loaded with the mobile radio device; The 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 the preset voltage threshold Vt, obtain the identifier information of the card reader from the received low frequency alternating magnetic field signal, and It is transmitted to the card reader through the RF channel together with its own identity information; the mobile radio device is also used for card transaction with the card reader through the RF channel.

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 can be implemented by the following specific circuits: 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, at least one radio frequency transceiver circuit, and at least one radio frequency antenna, wherein the low frequency transmitting coil, the driving circuit, and the encoding circuit a first main processor, a radio frequency transceiver circuit, an RF antenna, and a serial connection; the mobile radio device includes at least one low frequency magnetic induction circuit, at least one low frequency amplification circuit, at least one threshold determination and demodulation circuit, and 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, the second main processor, the radio frequency transceiver circuit, and the radio frequency antenna are sequentially connected 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 data transmission method carries the data frame, and the data frame contains the unique identification code Idr of the card reader (of course, it can also be other identity 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. The process principle of the mobile radio device accessing the card reader: The mobile radio device access card reader mainly includes a 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 realize 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: a first main processor 101, which is responsible for the low frequency of the card reader and For high frequency control and other protocol processing, the first main processor 101 is directly connected to the external communication interface through the interface circuit 102; the encoding circuit 108 is responsible for bit-by-bit encoding the low frequency frame data, and the modulation circuit 107 is responsible for encoding the output. The symbol stream modulates the carrier to form a modulated signal and sends it to the driving circuit 106. The encoded signal is directly sent to the driving circuit 106 when no modulation is required. The driving circuit 106 is responsible for driving the low frequency transmitting coil 105 to generate a low frequency alternating magnetic field 301; The low-frequency transmitting module formed by the transmitting coil 105, the driving circuit 106, the modulating circuit 107 and the encoding circuit 108 can change and set the transmission field strength value; the low-frequency transmitting coil 105 is usually composed of a plurality of coils of a specific shape; The circuit 103 receives and transmits an RF signal through the RF antenna 104.

The mobile radio device 200 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 mobile The SIM/TF/SD card body module of the terminal, 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 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 sensing 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 decision is made according to the preset threshold Vt. If the threshold Vt is not reached, the card is not demodulated and the card is not allowed to be swiped. The threshold Vt is used to demodulate the signal, and the demodulated signal is sent to the second main processor 201. The RF transceiver circuit 203 passes the RF. The antenna 204 is responsible for performing 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. Detecting the voltage signal 303 and determining whether the terminal enters a preset effective distance interval by a preset threshold Vt, the gate The limit 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 0~10 cm is to be realized, 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 triangular wave, etc., and the modulation can be switched frequency shift keying OOK, phase shift keying, frequency Shift keyed FSK or the like, the modulated signal is loaded into the low frequency transmitting coil 105 through the driving circuit 106; 2) the carrierless direct baseband transmitting: the baseband signal generated by the encoding circuit 108 is directly loaded into the low frequency transmitting coil through the driving circuit 106. 105; 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 maintaining the amplitude of the detection voltage in the mobile radio frequency device substantially constant during the transmission process can be The short-range communication system used in the present invention; the encoding circuit 108 can adopt various 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 bit symbol sequences: 01 and 10. The bit 1 code is different from the previous symbol sequence, bit 0 is the same, or the code is reversed.

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 including 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 without modulation. The driving circuit 106 transmits the modulation voltage to the low-frequency transmitting coil 105. 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 of the specified parameter according to the frame format with the set intensity Br continuously. The alternating 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 The format of the low frequency data frame of the card reader is as shown in Fig. 10. The frame of the low frequency data frame of the card reader is divided into the following fields: synchronization code: 8 bits, usually FFH, used for frame synchronization; control domain: 8 bits, used to provide information about the frame of the frame data, such as length, data class Type, etc., can retain reserved bits for expansion; IDr: N bits, card reader unique identification code, specified by the control field; CRC: check the control domain, IDr, CRC checksum or other methods can be used.

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 realize 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. In vivo (NVM) unique identification code, or by mobile radio device Produce a long enough random number.

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 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 is possible to 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 signals, and moves the radio frequency The 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. 3. Because the receiving signal is weak, an amplifying circuit needs to be added 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 work 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 that the performance is degraded, the accuracy of the distance control is reduced, and it may be necessary to supplement the simple calibration. These applications are not described in the present invention. The principle is fundamentally conflicting, but an extension 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.

Card reader

The present invention proposes a card reader. Figure 12 is a structural diagram of a card reader in an embodiment of the present invention. As shown in FIG. 12, in the present embodiment, the card reader includes a low frequency magnetic field transmitting portion 1200 and a radio frequency transmitting and receiving portion 1100. The low frequency magnetic field transmitting portion 1200 includes an encoding circuit 1201, a modulation circuit 1202, a driving portion 1203, and a low frequency. The transmitting coil 1204, the radio frequency transceiver portion 1100 includes a controller 1101, a radio frequency transceiver 1102, and a radio frequency antenna 1103. The driving portion 1203 includes a driving circuit and an adjusting circuit. It can be seen that the card reader shown in FIG. 12 is basically identical to the structure of the card reader device 100 in the short-range communication system shown in FIG. 8, but in FIG. 12, the first in FIG. The main processor 101 is specifically the controller 1101. Wherein, the low-frequency transmitting link composed of the low-frequency transmitting coil, the driving circuit and the encoding circuit operates at a frequency below the highest frequency f0 of the pre-selected system without calibration work. The card reader emits a preset low-frequency alternating magnetic field signal with a constant amplitude or a constant differential amplitude, and the amplitude value of the low-frequency alternating magnetic field signal corresponds to a set physical communication distance, and the error of the amplitude of the low-frequency alternating magnetic field signal is less than a preset error value. The method for determining the amplitude value and the physical communication distance of the δ _{R with} respect to the low-frequency alternating magnetic field signal has been described above, and will not be described herein.

Wherein: the low frequency transmitting coil 1204, the function of which is to emit a low frequency magnetic field signal. The controller 1101 can be mainly composed of an enameled wire or a PCB trace; the controller 1101 is responsible for the control of the entire card reader, including the control of the low frequency magnetic field transmitting portion 1200 and the control of the radio frequency transceiver portion 1100; the radio frequency transceiver 1102 is responsible for transmitting and receiving radio frequency signals. The RF communication frequency is mainly UHF frequency band, especially the 2400Mhz~2483MHz frequency band, and other frequency bands, such as 433MHz, 900MHz, 5GHz, etc.; the RF antenna 1103 is responsible for the radiation and reception of the RF energy; the coding circuit 1201 is mainly responsible for the low frequency magnetic field signal information. The modulation circuit 1202 is mainly responsible for modulating the encoded low frequency magnetic field signal information onto the carrier; the driving portion 1203 includes a driving circuit and an adjusting circuit, and the driving circuit is mainly responsible for the low The frequency magnetic field signal amplifies and enhances its driving capability, and the adjustment circuit is mainly responsible for adjusting the error of the low frequency magnetic field signal strength. The driving circuit may be a square wave, a sine wave, a triangular wave or the like which is formed by a DAC (Digital Analog Canverter) and an operational amplifier (hereinafter referred to as an operational amplifier), and may be a resistor, a capacitor, or a capacitor. Waveforms such as square waves, sine waves, and triangular waves composed of op amps and amplifier circuits. The adjustment circuit can be an adjustment of the output voltage of the driving circuit or a resistance of the adjustment load.

Figure 13 is a structural view of the driving portion in Fig. 12. The driving portion 1203 may be composed of a DAC 1213, an operational amplifier 1223, and a resistor 1233 that are sequentially connected in series.

Based on the above card reader, the present invention proposes a low frequency alternating magnetic field distance control method, which is applied to the above card reader, and the low frequency alternating magnetic field distance control method comprises the following steps:

Step a, transmitting a low-frequency alternating magnetic field signal of a predetermined transmission parameter through a low-frequency transmission channel, wherein the signal includes an identifier IDr of the card reader, and the top emission parameter includes a highest frequency f0 of the system without calibration work, and an encoding method The modulation mode and the constant field strength parameter; at the same time, waiting for receiving information from the terminal containing the mobile radio device through the radio frequency channel; in step a, the selection method of the highest frequency f0 of the system without calibration work is as follows: the frequency of the low frequency alternating magnetic field is higher Low, the smaller the difference in attenuation after passing through various types of terminals, the characteristic point is used to select a frequency point with a sufficiently small difference in the frequency selection system to achieve non-calibrated distance control. Using a standard signal source to transmit a low-frequency alternating magnetic field through a standard magnetic field transmitting coil, receiving the alternating magnetic field inside each typical mobile terminal and obstacle, adjusting the transmitting frequency until the frequency point f0 is found, so that the voltage received by the mobile radio frequency device is Under the same distance from the plane center point of the transmitting coil, the field strength difference between different terminals and obstacles is approximately equal to the set fluctuation range δ _T . The frequency point and the frequency band below the frequency point are the frequency bands in which the system has no calibration work, and the frequency is high. At the f0 frequency, the system needs to be calibrated. Generally, the more frequencies are higher than f0, the more terminals that need to be calibrated, the higher the complexity of calibration. Frequency selection is a one-time job, once selected, no changes are needed during use.

In step a, in addition to the frequency point, other predetermined transmission parameters are selected as follows:

Step a1: Select a constant field strength mode (ie, a constant field strength parameter). The constant field strength method includes a constant peak field strength amplitude and a constant differential field strength amplitude, and the peak field strength is selected to be constant. Step a2 is performed to select a differential field strength constant. In step a3, the amplitude error of the constant field strength parameter is less than the preset error value δ _R ; the typical form of the direct current or alternating magnetic field having a constant peak field strength amplitude is as shown in Fig. 14, which may be a DC magnetic field or a square wave magnetic field. Or a sinusoidal magnetic field: a low-frequency alternating magnetic field with a constant differential field strength, which is a low-frequency alternating magnetic field with a constant maximum rate of change of the magnetic field. The typical form is shown in Fig. 15, which can be seen from Fig. 15: a triangular wave magnetic field with a constant differential amplitude. Under the launch condition, the voltage sensed by the SIM card coil is in the form of a square wave.

The reader can emit a constant field strength as the reference field strength for distance detection. Since the low frequency magnetic field decays rapidly with the distance, the low frequency field strength around the reader can be used as the distance gauge. The accuracy of the reader as a distance detection ruler can be controlled by precisely controlling the difference value δ _{R of the field} strength of each reader, wherein the typical range of δ _R is within 4 dB, that is, the typical value of δ _R is less than 4 dB.

Step a2: under the condition that the peak field strength is constant, the coding mode, the modulation mode, and the driving voltage waveform are selected, and the target value of the low frequency magnetic field strength is determined, thereby selecting the driving voltage amplitude, the adjustment parameter, the low frequency transmitting coil resistance, and the low frequency transmitting coil lap. Measuring whether the low-frequency magnetic field strength under the selected parameter meets the target value of the predetermined low-frequency magnetic field strength in the range of δ _R , if yes, the selection of the transmission parameter is completed, and ends, otherwise the driving circuit and the low-frequency transmitting coil parameters are re-adjusted until the measured low frequency The magnetic field strength is in accordance with the predetermined low frequency magnetic field strength target value error in the range of δ _R ; the selection procedure of the emission parameters is as shown in Fig. 16. In step a2, the detailed selection method is as follows: Coding mode selection: Under the condition of constant peak field intensity constant emission magnetic field, there is no specific requirement for coding mode, and the coding mode selection is one-time work. Once selected, no change is needed in use; modulation mode Choice: Under the condition of peak field strength constant emission magnetic field, mainly constant envelope modulation mode such as FSK, PSK, etc. Modulation mode selection is one-time operation. Once selected, no change is needed in use; drive voltage waveform selection: peak field strength Under the condition of constant amplitude transmitting magnetic field, the driving voltage waveform is preferably square wave, and the driving voltage waveform selection is one-time operation. Once selected, there is no need to change in use; low frequency magnetic field strength target value selection: low frequency magnetic field strength target value according to card reader The requirements of the application are determined. If it is a medium-distance application, the magnetic field strength is high. If it is a close-range application, the magnetic field strength is low. The driving voltage amplitude is selected: after the low-frequency magnetic field strength target value is selected, the corresponding driving is selected. Voltage amplitude, drive voltage amplitude can be driven by the drive circuit Pressure over 60% of the full amplitude; adjustment parameter selection: the adjustable voltage output driving circuit may adjust the load resistance, low frequency magnetic field emission consistent with a preset field strength values. Specifically, when the driving part is the circuit shown in FIG. 13, the parameter adjustment can be performed by adjusting the DAC output voltage or the operational amplifier amplification factor and adjusting the load resistance; the transmitting coil parameter selection: the transmitting coil can be mainly wound by an enameled wire or It is composed of PCB traces; the area of the low-frequency transmit coil is as large as the area of the ordinary mobile phone, so as to ensure that the position of the SIM card of different mobile phones is within the low-frequency transmit coil, thus ensuring the stability and convenience of the mobile phone card; the area of the low-frequency transmit coil (refer to the area enclosed by the coil, the same below) is mainly greater than 10 square centimeters, further, the area of the low-frequency transmitting coil can be surrounded by 20-1000 square centimeters; low-frequency transmitting coil, under the premise of ensuring the same magnetic flux, the number of turns required It is inversely proportional to the driving voltage requirement; the number of turns of the low-frequency transmitting coil is mainly greater than 10匝, further, the number of turns of the low-frequency transmitting coil is 50-500 circles; the resistance of the low-frequency transmitting coil is mainly greater than 10 ohms, further, low-frequency emission The resistance of the coil is 50-500 ohms.

After the above parameters are selected, whether the measured magnetic field strength meets the target value of the predetermined low frequency magnetic field strength is within a range of δ _R , and if not, the drive circuit and the low frequency transmitting coil parameters are re-adjusted; if yes, the predetermined parameter is selected. carry out.

Step a3: under the condition that the differential field strength is constant, the coding mode, the modulation mode, and the driving voltage waveform are selected, and the target value of the low frequency magnetic field strength is determined, thereby selecting the driving voltage amplitude, the adjustment parameter, the low frequency transmitting coil resistance, and the low frequency transmitting coil lap. Then measuring whether the low-frequency magnetic field strength under the selected parameter meets the error of the predetermined low-frequency magnetic field strength target value in the range of δ _R , and if so, the transmission parameter selection is completed, and ends, otherwise the driving circuit and the low-frequency transmitting coil parameters are re-adjusted until the measurement The low frequency magnetic field strength meets the predetermined low frequency magnetic field strength target value error in the range of δ _R .

In step a3, the detailed selection steps are as follows: coding mode selection: under the condition of constant field intensity constant emission, the coding mode is mainly composed of Manchester code or other return-to-zero code, and the coding mode selection is one-time work. Once selected, it is used. No need to change in the medium; modulation mode selection: under the condition of constant field emission magnetic field, mainly FSK, PSK and other constant envelope modulation mode, the modulation mode selection is one-time work, once selected, no need to change in use; drive voltage waveform selection : Under the condition of constant field emission magnetic field, the driving voltage waveform is preferably triangular wave, and the driving voltage waveform selection is one-time operation. Once selected, there is no need to change in use; the peak field strength constant in the subsequent steps and step a2 is constant. The condition selection method is the same and will not be repeated.

Step b: The radio frequency channel receives the information of the terminal that includes the mobile radio frequency device, and the information includes the identifier IDr of the card reader returned by the terminal and the ID code cc of the terminal itself, decodes the IDr and the IDc, and compares the returned IDr with The IDRs sent are the same. If they are the same, the subsequent RF communication realizes the unique binding communication between the reader and the terminal through the combined address of (IDr, IDc); if it is different, the communication error occurs, and the RF channel continues to wait until receiving correctly. Data; at the same time, the low frequency channel continuously transmits a low frequency alternating magnetic field signal of a predetermined transmission parameter;

In step c, the transaction is communicated through the RF channel until the transaction is completed. At the same time, the low frequency channel continuously transmits the low frequency alternating magnetic field signal of the predetermined parameter.

The frequency of the low frequency alternating magnetic field is mainly 0-100 KHz, and further, the low frequency alternating magnetic field frequency may be 0-10 KHz.

In steps a2 and a3, the control method for transmitting the field strength error range δ _R of the card reader is as follows: in order to ensure the consistency between each card reader during mass production, it is necessary to establish an error correction for each card reader. System, the system detects and adjusts the error of each reader to ensure the consistency of each reader, thus ensuring the controllable distance of the card.

The error correction system of the card reader is as shown in Fig. 17, and the error correction system of the card reader includes a modified card reader 1702 and a magnetic field strength detecting means 1701 located at a set height Dc above the corrected card reader 1702.

Based on the error correction system described in FIG. 17, the error correction method of the card reader is as follows: Step 1. Set the measurement target Hs and the error range He of the magnetic field strength detecting device, and then correct the card reader in the standard magnetic field strength detecting device. The error correction field strength range is [Hs-He, Hs+He]; where He<δ _R , δ _R is the preset error value, the smaller He is, the larger the system margin is; the second step is when testing the card reader. The modified card reader emits a low frequency magnetic field signal, and the magnetic field strength detecting device compares the magnetic field strength of the currently received low frequency magnetic field signal, and adjusts the emission adjustment circuit on the modified card reader so that the magnetic field strength of the corrected card reader is set. The error correction field strength range [Hs-He, Hs + He].

The error correction system can be a separate system or a function module attached to the card reader, thereby implementing the self-error correction function of the card reader.

The structure of the card reader with its own error correction function is shown in Figure 18. As can be seen from Fig. 18, the card reader with its own error correction function has an error correction portion 1400 which is composed of a sequentially connected sampling circuit 1401, an amplifying circuit 1402 and a low frequency receiving coil 1403, as compared with the aforementioned card reader. In the composition, the sampling circuit 1401 is connected to the controller 1101. The card reader senses the voltage radiated from the low-frequency transmitting coil of the card reader through the receiving coil on the card reader, and transmits it to the controller through amplification and sampling. The controller determines the low-frequency transmitting signal by judging the magnitude of the sampling signal amplitude. Whether it meets the requirements of emission intensity.

Based on the card reader with the error correction function shown in Fig. 18, the self-adjustment error correction method of the card reader is as follows: Step 1. Set the measurement target Hs and the error range He of the local magnetic field strength detecting device of the card reader, The range of error correction field strength under the local magnetic field strength detecting device of the card reader is [Hs-He, Hs+He], where He<δ _R , the smaller He is, the larger the system margin is; the local magnetic field strength detecting device is shown in Fig. 18. The sequentially connected controller 1101, the sampling circuit 1401, the amplifying circuit 1402 and the low frequency receiving coil 1403 are shown; Step 2. When testing the card reader, the low frequency transmitting coil of the card reader transmits a low frequency magnetic field signal, and the local magnetic field strength is detected. The device compares the magnetic field strength of the currently received low frequency magnetic field signal, and adjusts the emission adjustment circuit on the card reader so that the magnetic field strength of the card reader is within the set error correction field strength range [Hs-He, Hs + He].

The card reader of the present invention also has the function of detecting whether there is interference with the card reader and alarming. Specifically, the method for detecting the interference card reader is as follows: when the legal card reader works, it searches for nearby low frequency or radio frequency signals, and decodes the searched low frequency or radio frequency signals to determine Whether the information carried in the low frequency or radio frequency signal contains the unique identification code of the legal card reader, if included, it indicates that there is no interference with the card reader nearby, otherwise the card reader is interfered. The legal card reader can further detect the signal strength of the received low frequency or radio frequency signal, and determine the distance between itself and the nearby interference card reader according to the signal strength, and if the nearby interference card reader is within the set safety distance, the alarm is generated. .

As can be seen from the above, the card reader of the present invention enables a card transaction such as electronic payment for a mobile terminal having various short-range communication functions without requiring calibration.

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.

1100‧‧‧RF Transceiver Section

1101‧‧‧ Controller

1102‧‧‧RF Transceiver

1103‧‧‧RF antenna

1200‧‧‧Low frequency magnetic field emission part

1201‧‧‧Code Circuit

1202‧‧‧Modulation circuit

1203‧‧‧Drive section

1204‧‧‧Low frequency transmitting coil

Claims (17)

A radio frequency card reader comprising at least: a low frequency transmitting coil, a driving circuit, an encoding circuit, a first main processor, a radio frequency transceiver circuit, and an RF antenna, the low frequency transmitting coil, the driving circuit, the encoding circuit, and the The first main processor, the radio frequency transceiver circuit and the radio frequency antenna are connected in series; wherein the low frequency transmitting coil, the driving circuit and the encoding circuit form a low frequency transmitting link; the low frequency transmitting link is Configuring to transmit a low-frequency alternating magnetic field signal according to a preset transmission parameter, where the low-frequency alternating magnetic field signal carries identity information of the radio frequency card reader; wherein the transmission parameter includes the low-frequency alternating magnetic field signal Frequency and field strength parameters; wherein the frequency is equal to or less than a highest frequency f0 of the system without calibration work; the field strength parameter is set according to a preset physical communication distance, and the physical communication distance refers to the radio frequency card reader a physical distance for radio frequency communication with the mobile radio device; the radio frequency transceiver circuit and the radio frequency antenna are configured to receive the mobile shot Information transmitted by means of radio frequency channel; said first host processor for verifying the information, and credit card transactions by the radio frequency channel based on the control information with the mobile radio device. The radio frequency card reader according to claim 1, further comprising a modulation circuit between the driving circuit and the decoding circuit. The radio frequency card reader according to claim 1, wherein the driving circuit comprises a tone The whole circuit. The radio frequency card reader according to claim 3, further comprising a serial analog-to-digital converter (DAC), an operational amplifier, and a resistor. The radio frequency card reader according to claim 1, further comprising a local magnetic detector. The radio frequency card reader of claim 5, wherein the local magnetic detector comprises a controller, a sampling circuit, an amplifying circuit, and a low frequency receiving coil. The radio frequency card reader of claim 1, wherein the low frequency transmitting coil has a number of turns greater than 10 turns. A method for utilizing a radio frequency card reader, the radio frequency card reader comprising a low frequency transmit link, wherein the method comprises: the low frequency transmit link transmitting a low frequency alternating magnetic field signal according to a preset transmit parameter, the low frequency crossover The edge magnetic field signal carries the identity identification information of the radio frequency card reader; wherein the transmission parameter includes a frequency and a field strength parameter of the low frequency alternating magnetic field signal, wherein the frequency is equal to or less than a maximum frequency of the system without calibration work The field strength parameter is set according to a preset physical communication distance, where the physical communication distance refers to a physical distance between the radio frequency card reader and the mobile radio frequency device for radio frequency communication; the mobile radio frequency device is at each distance point. Receiving and detecting the low-frequency alternating magnetic field signal and amplifying the voltage signal with a constant amplitude corresponding to the distance, when receiving the low-frequency alternating magnetic field signal corresponding voltage signal is greater than or equal to a preset variable voltage threshold Vt, The mobile radio frequency device acquires the identity identification information of the radio frequency card reader from the received low frequency alternating magnetic field signal, and moves together The identity identification information of the frequency device is transmitted to the radio frequency card reader through the radio frequency channel; The radio frequency card reader receives information transmitted by the mobile radio frequency device through the radio frequency channel, verifies the information, and performs a card transaction with the mobile radio frequency device according to the information through the radio frequency channel. The method of using a radio frequency card reader according to claim 8, wherein determining the highest frequency f0 of the system without calibration operation comprises: (a1) determining between the radio frequency card and the radio frequency card reader. The distance control target value (Din, Dv), wherein Din indicates that in the range of 0~Din, all terminals configuring the radio frequency card are ensured to be read by the radio frequency card reader; wherein Dv represents a distance floating range, so that The radio frequency card is read by the radio frequency card reader within a distance range of Din~(Din+Dv) and exceeds a distance range of (Din+Dv), the radio frequency card will not be allowed to be read by the radio frequency Card reader reading; (a2) determining a floating range δR of the radio frequency card detecting electrical signal, wherein the floating range is caused by the radio frequency card reader; (a3) determining a detecting electrical signal caused by the radio frequency card itself The fluctuation range δC; (a4) testing the electrical signal-distance curve of various typical terminals and obstacles at the frequency f; (a5) determining the fluctuation of the detected electrical signal of the radio frequency card according to the distance control target value (Din, Dv) Range δA, where δA is equal to the electrical power of the various typical terminals and obstacles a difference between the Din point electric signal and the (Din+Dv) point electric signal on the voltage distance curve obtained by the distance-distance curve having the average field strength attenuation curve; (a6) determining the radio frequency card caused by the terminal Detecting a fluctuation range δT of the electrical signal, wherein δT represents: a fluctuation range of the detection voltage in the radio frequency card caused by an attenuation characteristic of the terminal, δT=δA−δR−δC; and (a7) calculating the various typical terminals And obstacles, in the range of RF communication distance control The maximum field strength difference δ at different distance points within, if δ is greater than δT, the frequency f is decreased, and the process returns to step (a4). If δ is smaller than δT, the frequency f is increased and returned to (a4). If δ is equal to δT, the current test frequency f is equal to the frequency f0. The method of using a radio frequency card reader according to claim 8, further comprising: (a) transmitting, by the low frequency transmission channel, the radio frequency card reader continuously transmits a signal with a preset transmission parameter, wherein the signal The identifier (IDr) of the radio frequency reader is included, wherein the transmission parameter includes a frequency f, an encoding mode, a modulation mode, and a constant field strength parameter; and the radio frequency card reader waits for receiving from the configuration through the radio frequency channel Information about the mobile terminal of the radio frequency card; (b) exchanging information between the radio frequency card and the radio frequency card reader through the radio frequency channel; the information includes: receiving by the radio frequency card and from the radio frequency The identification code (IDr) returned by the card; the identification code (IDc) of the mobile terminal; and the identification code (IDr) and the identification code (IDc) decoded by the radio frequency card reader; The radio frequency card reader determines whether the identity code (IDr) returned from the radio frequency card is consistent with the identity code (IDr) transmitted by the radio frequency card reader; if consistent, in subsequent radio frequency communication In the process, use (IDr, IDc) The combined address forms a unique binding of the radio frequency reader and the terminal; otherwise, indicating a communication error, returning to step (a) until a consistent identification number (IDr) is determined; (c) transacting through the radio frequency channel . The method for using a radio frequency card reader according to claim 8 of the patent application scope further includes: (a11) selecting one of the following methods: the peak field strength amplitude is constant; or the differential field strength amplitude is constant; and correspondingly performing the following steps (a21) or (a31); (a21) for the peak field strength amplitude constant mode Select the coding mode, modulation mode, and drive voltage waveform; determine the target field strength of the low frequency magnetic field to select the following parameters: drive voltage amplitude; correction parameters; low frequency transmit coil resistance; and low frequency transmit coil turns; detection in selected parameters Whether the signal strength of the low frequency magnetic field meets the intensity target value of the preset low frequency magnetic field; if it is met, the parameter selection is completed; otherwise, the parameter is recalibrated; or (a31) for the differential field strength amplitude constant mode: select coding Mode, modulation mode, driving voltage waveform; determining a target field strength of the low frequency magnetic field to select the following parameters: driving voltage amplitude; calibration parameter; low frequency transmitting coil resistance; and low frequency transmitting coil turns; Detecting whether the signal strength of the low frequency magnetic field meets the preset intensity target value of the low frequency magnetic field under the selected parameter; if it is met, the parameter selection is completed; otherwise, the parameter is recalibrated. The method for using a radio frequency card reader according to claim 8 of the patent application, further comprising self-adjustment correction for a communication distance error; the self-adjustment correction comprises: (i) setting a measurement target Hs and an error of the local magnetic detector a range He, where He is less than a preset error value δR, and wherein the field strength detected by the local magnetic detector is within an expected range [Hs-He, Hs + He]; (ii) the local magnetic detector will The magnetic field strength of the signal currently receiving the low frequency magnetic field is compared to the expected range, and if not within the expected range, the emission adjustment coil of the radio frequency reader is adjusted. The method of using a radio frequency card reader according to claim 12, wherein the error self-adjustment correction is performed externally by a local magnetic detector external to the radio frequency reader, or by being placed in the radio frequency reading The magnetic detector inside the card is internally performed. The method of using a radio frequency card reader according to claim 8 of the patent application, further comprising: detecting an interfering radio frequency card reader. The method of using a radio frequency card reader according to claim 14, wherein the detecting the interference radio frequency card reader comprises: searching for a low frequency signal or a radio frequency signal. The method for using a radio frequency card reader according to claim 15, further comprising: decoding the low frequency signal or the radio frequency signal if the low frequency signal or the radio frequency signal is detected; Determining whether the decoded signal includes a unique identification code on a legitimate radio frequency reader. The method for using a radio frequency card reader according to claim 16 , further comprising: determining a distance from the interfering radio frequency card reader according to the strength of the low frequency signal or the radio frequency signal; if the distance is determined to be An alarm is issued within the preset safety distance.