WO2011140731A1

WO2011140731A1 - Device, system and method for low-frequency magnetic field signal detecting, transmission and distance estimating

Info

Publication number: WO2011140731A1
Application number: PCT/CN2010/073764
Authority: WO
Inventors: 汪海翔; 蒋宇
Original assignee: 国民技术股份有限公司
Priority date: 2010-05-10
Filing date: 2010-06-10
Publication date: 2011-11-17
Also published as: CN103023536A; CN103023536B

Abstract

A device, system and method for close range low-frequency magnetic field signal detecting, transmission and distance estimating. The device includes: at least one low-frequency inducing module (01) for inducing the low-frequency signal, at least one amplifier (02) for amplifying the low-frequency induced signal, at least one analog to digital converter (03) which is connected with the output of the amplifier, and a digital processing module (04) which is connected with the analog to digital converter and arranged for estimating intensity of the original signal and detecting signal output.

Description

Apparatus, system and method for low frequency magnetic field signal detection and transmission and distance determination

The present invention relates to the field of communications, and in particular, to a device and method for detecting and transmitting a low-frequency magnetic field signal when a distance-controlled close-range secure data communication is performed between a terminal and a terminal, and particularly relates to a radio frequency device (such as a radio frequency card) or Distance control of radio frequency communication terminals (such as mobile phones, PDAs, etc.) with close-range radio frequency communication functions and short-range radio communication devices (such as P0S or card readers; P0S, ie Po int of sa les), low-frequency signal detection of magnetic fields Apparatus and method of transmission. Background technique

With the rapid advancement of science and technology, people's lives are becoming more and more convenient. The mobile payment industry has emerged in this situation. Now, just change the mobile phone to a SIM card to realize close-range communication of mobile phones. The emergence of the mobile phone becomes a super smart terminal that can be recharged, consumed, traded and authenticated, which greatly meets the urgent needs of the market.

Such an SIM card is embedded in a mobile phone card slot by using a technology such as UHF (Ultra tra Hi gh Frequency) to complete short-range communication and transactions without modifying other structures.

However, due to the transmission difference of UHF in different structure mobile phones, the communication distances of mobile phones with different shielding performances are quite different, ranging from a few meters to a few centimeters, in the case of card transactions such as bus P0S machines or subway gates. There are strict limits on tradable distance to ensure that misuse is avoided. Therefore, effective control of distance becomes an urgent need.

In the prior art, there is a system and method for low-frequency alternating magnetic field close-range detection combined with RF high-frequency communication, which solves the above problem of distance control. The system utilizes low-frequency alternating magnetic field to realize one-way communication from the card reader to the card, complete distance control and identity authentication, and then use the RF channel to realize high-speed communication between the card reader and the card. The system features no need to modify the mobile terminal, just replace the SIM card / TF / SD card inside the terminal, you can achieve reliable two-way distance communication.

The card reader transmits the low frequency alternating magnetic field signal, and the card only needs to receive the magnetic field signal. Since the communication is one-way communication, and the card reader does not need to provide energy through the magnetic field, the receiving line or other receiving circuit can be miniaturized enough to be placed. SIM card / TF / SD card. Since the received signal is weak, the card needs to be increased. amplifying circuit.

In addition, the RF transceiver circuit is placed in the card 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.

The distance detection and control is realized by the low frequency channel, and the card reader transmits its unique identification IDr to the card through the low frequency unidirectional channel, and the card is transmitted to the card reader through the RF channel together with the card's own unique IDc. The unique binding of the card reader and the card is realized, that is, the process of the mobile terminal accessing the card reader.

Since the card reader and the card are uniquely bound, the communication after the access process is carried out using the RF channel, and the reliability of the distance control and the reliability of the communication can still be ensured.

In summary, both the low frequency and the size of the RF antenna can be integrated into the card, and the two-way communication is realized by the combination of low frequency and RF, so there is no need to modify the mobile terminal, and only the SIM card/TF/SD card inside the terminal needs to be replaced. , to achieve reliable two-way distance communication.

Therefore, how to effectively reduce the interference of circuit noise and environmental noise on low-frequency signals, accurately recover the data stream from the low-frequency signal, realize the one-way communication between the card reader and the card, and extract the distance information to effectively control the distance of the transaction. Problems to be solved. Summary of the invention

The technical problem to be solved by the present invention is to provide a method and device for detecting and transmitting short-range low-frequency magnetic field signals and determining distance, for sensing low-frequency signals, pre-amplifying low-frequency weak signals, analog-to-digital conversion, and field strength detection. And means and methods of data communication.

The technical solution of the present invention to solve the above technical problem is as follows: A device for detecting and transmitting low frequency magnetic field signals and determining a distance, comprising at least one low frequency sensing module for sensing a low frequency magnetic field signal, and at least one for amplifying a low frequency sensing signal. An amplifier, at least one analog to digital converter coupled to the output of the amplifier, and a digital processing module coupled to the analog to digital converter for determining the strength of the original signal and completing the signal detection output.

The invention has the beneficial effects that: by using the structure of the device of the invention, it is not necessary to modify the mobile terminal, and only the SIM card/TF/SD card inside the terminal needs to be replaced, so that reliable two-way distance communication can be realized.

Based on the above technical solutions, the present invention can also be improved as follows.

Further, the low frequency sensing module is a sensing coil, a Hall sensor, or a giant magnetoresistance. Further, the amplifier adopts a cascade of multi-stage amplifiers.

Further, the amplifier is a single-ended amplifier, and may also be a differential amplifier.

Further, each of the cascaded multi-stage amplifiers is connected to a high-pass filter circuit, each stage output is connected to a low-pass filter circuit, and the amplifier is an amplifier with low offset and high gain bandwidth product.

The beneficial effect of using the above further solution is to introduce high-pass and low-pass filtering at each input and output to improve the signal-to-noise ratio.

Further, the analog to digital converter employs a parallel analog to digital converter.

The beneficial effects of using the above further solution are: improving the processing efficiency of the back end digital module. Further, the analog to digital converter speed is greater than 1 KSPS and the input range is 0V to the analog to digital converter reference voltage.

Further, the analog-to-digital converter input front end is provided with a voltage follower connected to the amplifier.

The beneficial effects of using the above further solution are as follows: Stabilizing the analog amplified signal outputted by the amplifier to avoid voltage drift caused by high resistance of the A/D front end, resulting in distortion of analog to digital conversion.

Further, a digital glitch filter for puncturing the digital signal is disposed between the analog to digital converter and the digital processing module.

The present invention also provides a system for low-frequency alternating magnetic field close-range detection combined with radio frequency high-frequency communication, including a radio frequency communication terminal and a short-range radio frequency communication device, wherein the radio frequency communication terminal includes any one of claims 1 to 8. The device for detecting and transmitting short-range magnetic field signals and determining the distance, and the RF device for bidirectional communication with the short-range radio communication device and the device for detecting and transmitting short-range magnetic field signals and distance Transceiver circuit.

The invention also provides a method for detecting and transmitting short-range magnetic field signals and distance determination, the method comprising:

Step a: measuring the induced voltage of the magnetic induction module and the magnetic field reader at different distance points, the voltage amplitude value amplified by the amplifier, determining the corresponding relationship between the voltage amplitude value and the distance, and establishing a correspondence table between the amplitude value and the distance;

Step b: according to the requirement of decoding the low-frequency signal transmission data and controlling the swipe distance, combined with the signal-to-noise ratio requirement, determining the output signal of the analog-to-digital converter by comparing the threshold to form the hysteresis decision voltage threshold, and obtaining the code stream information transmitted by the low-frequency magnetic field; By comparing the threshold to form a non-hysteresis decision voltage threshold, the output signal of the analog-to-digital converter is determined, and the distance characteristic information transmitted by the low-frequency magnetic field is obtained; Step c: sampling the non-hysteresis decision condition signal to obtain a 0, 1 code stream sequence, setting a 1 signal proportional threshold, and counting the code stream sequence within a set time window length, when the 1 signal occupies the code stream When the sequence ratio reaches the preset proportional threshold, it is considered to enter the set distance range, otherwise it is considered that the distance range is not entered; the signal sequence after the decision of the hysteresis decision condition is decoded, the code stream information of the low frequency magnetic field is extracted, and the low frequency magnetic field signal signal is completed. To communication.

Further, in the step b, according to the correspondence table of the amplitude value and the distance in the step a, combining the decoding distance, the requirement of the distance control, and the proportional threshold of the setting 1 signal, the comparison threshold in the digital processing module is set.

Further, in the step b, the magnetic field distance information and the code stream information are extracted using a single, a plurality of single, a pair, a plurality of pairs of comparison thresholds or a combination thereof.

Further, the pair of comparison thresholds in the digital processing module is a non-hysteresis decision condition, and the setting method is: setting the distance of the desired control to D1, searching the correspondence table of the amplitude value and the distance, and obtaining the signal variation range corresponding to D1 is +A1 To -A1, set the proportional threshold of the 1 signal to R1. According to A1 and R1, set the level Ll, L2 output to the comparator to meet the time percentage of the output signal amplitude of the front-end device greater than L1 or less than L2 in one cycle. R1, that is, greater than R1, enters the range of the required control distance D1, otherwise it does not enter the range of the required control distance D1.

Further, the pair of comparison thresholds in the digital processing module is a hysteresis decision condition, and the setting method is: if the distance to be decoded is D2, the correspondence table between the amplitude value and the distance is searched, and the variation range of the D2 corresponding signal is +A2. To -A2, the amplitude of most noise is measured as A3, and the level of output L3, L4 is set to the comparator so that L3 should be greater than +A3 and less than +A2; L4 is less than -A3 and greater than -A2. That is, decoding is allowed when the distance is less than D2, otherwise decoding is not allowed.

Further, in the step b, the two output signals judged by using a pair of non-hysteresis decision conditions are logically processed, and the digital signals for extracting the distance information are obtained after the processing.

Further, in the step b, the two output signals judged by using a pair of hysteresis decision conditions are subjected to hysteresis processing, and after the hysteresis processing, a digital signal for extracting the magnetic field code stream information is obtained.

Further, when a single comparison threshold is used to extract the magnetic field code stream information, the comparison threshold is set to the amplifier input reference level; when a single comparison threshold output comparison level is used to extract the magnetic field distance information, the comparison threshold setting method is consistent with a pair of comparison threshold setting methods. .

Further, the method uses a single comparison threshold to output a digital signal for single distance and code stream determination, or a pair of comparison thresholds to output a digital signal for a single distance And the determination of the code stream; the method uses a plurality of single comparison thresholds to output a digital signal for judging a plurality of distances and code streams, or using a plurality of pairs of comparison thresholds to output a digital signal for multiple distances, multiple Distance interval and code stream judgment.

Further, the method performs a plurality of distances, a plurality of distance intervals, and a code stream by using a plurality of single comparison thresholds to output a digital signal and a plurality of pairs of comparison thresholds to output the digital signals.

Further, in the step C, the step of performing burr filtering on the input digital signal is performed, and then the low frequency magnetic field data stream is decoded from the signal for filtering the glitch. DRAWINGS

1 is a structural diagram of an embodiment of an apparatus for detecting and transmitting short-range magnetic field signals and distance determination according to the present invention;

2 is a schematic structural view of a sensing coil inductive low frequency mode and a single-ended input amplifier according to the present invention; FIG. 3 is a schematic structural view of a Hall sensor inductive low frequency mode and a single-ended input amplifier according to the present invention;

4 is a schematic structural view of a giant magnetoresistance induction low frequency mode and a single-ended input amplifier according to the present invention; FIG. 5 is an application example of the differential signal input amplifier of the sensing signal according to the present invention;

FIG. 6 is a flowchart of a method for detecting a low frequency signal according to an embodiment of the present invention.

FIG. 7 is a schematic diagram showing the correspondence between the distance and the amplitude value of the low frequency sensing signal by the experimentally measured sensing module being placed in different mobile communication terminals according to an embodiment of the present invention.

8 is a diagram showing an internal basic structure of an analog-to-digital converter according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a decoding process using a low-frequency magnetic field signal detecting method using a pair of comparison thresholds according to an embodiment of the present invention; FIG.

10 is a schematic diagram of a distance control process using a low-frequency signal detection method using a pair of comparison thresholds in an embodiment of the present invention;

11 is a schematic diagram of decoding processing using a magnetic field data low-frequency signal detection method using a single comparison threshold in an embodiment of the present invention; schematic diagram of distance control processing;

Figure 13 is a system for low-frequency alternating magnetic field close-range detection combined with radio frequency high-frequency communication according to the present invention Structure diagram.

In the drawings, the list of parts represented by each label is as follows:

01 氐 frequency sensing module

02 amplifier

03 Analog/Digital Converter

04 Digital Logic Module

05 comparator

06 Analog to Digital Converter Control Module

07 analog to digital converter

08 data register

AIN: Single-ended input signal

VINP: differential input signal positive terminal

VINN: Negative input signal negative

VCM: Common mode voltage

Vref: reference voltage

V0UT: Output analog signal at the last stage of the amplifier

Ral, Ra2, Ra3, Ra4, Ra5, Rl, R2: Resistor

R3, R4, R5, R6: Hall sensor internal devices

CI, C2, C3, C4, C5, C6, C7, C8, C9, CIO: Capacitance

L: induction line 圏

D0-Dn-1: ADC digital output

A: Voltage follower

B: Analog to digital converter core module. detailed description

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

The invention specifically realizes the detection and information communication of the low-frequency magnetic field strength, and adopts a structure of single-stage or cascaded gain-adjustable amplifier and analog-to-digital converter to complete information collection and response. Specifically, the amplifier is used to amplify the weak signal at the front end, and the amplified signal is connected to the input of the analog-to-digital converter. After the analog-to-digital conversion, the digital module is digitally algorithmized to realize distance control and communication. The following description will be made with reference to the drawings:

1 is a structural diagram of an apparatus for detecting and transmitting low frequency magnetic field signals and distance determination according to the present invention, which includes a low frequency sensing module 01, an amplifier 02 for amplifying a low frequency sensing signal, and an analog to digital converter connected to an output of the amplifier. 03. A digital processing module 04 coupled to the analog to digital converter 03 for determining the strength of the original signal and completing the signal detection output. The device for detecting and transmitting low-frequency magnetic field signals and distance judging device collects and amplifies weak low-frequency signals, and performs analog-digital conversion, digital algorithm, and finally completes distance control and transaction communication.

Fig. 2 is a view showing an example of the configuration of a cascaded gain tunable amplifier used in a device for detecting and transmitting short-range magnetic field signals and distance determination according to the present invention. The cascaded gain adjustable amplifier in this example uses a single-ended input. As shown in Figure 2, the sense line 圏L is input to the negative voltage of the first amplifier by the change voltage AIN coupled by the low-frequency magnetic field strength change. The inverting amplification method is used to complete the preamplification of the low frequency weak signal through a 5-stage inverting amplifier.

In this example, each stage input introduces high-pass filtering, and the low-pass filter circuit is placed in the feedback loop. In Figure 2, Cl /Ral, C3/Ra2, C5/Ra3, C7/Ra4, and C9/Ra5 are RC high-pass filters for each input. As the frequency increases, the capacitance of the capacitor decreases, resulting in a rise in circuit gain and Qualcomm. Filtering, and C2/Rbl, C4/Rb2, C6/Ra3, C8/Rb4, C10/Rb5 are RC pass-through filtering of each stage of the feedback loop. As the frequency increases, the equivalent feedback impedance decreases continuously, resulting in gain. Drops, resulting in low pass filtering. In addition, the capacitor C1 input at the first stage acts as a blocking function to prevent the DC voltage difference across the sensing line from causing signal mis-amplification and false detection. The low frequency cutoff frequency of each stage is determined by its RC high-pass filter circuit, and the high-frequency cutoff frequency is determined by its RC low-pass filter circuit.

In this example, the amplification factor of each stage is determined by the corresponding Rb/Ra, and the total amplification factor after the amplification of the 5th stage is Rbl *Rb2*Rb3*Rb4*Rb5/Ral *Ra2*Ra 3*Ra4*Ra5, which can be used in practical applications. Increase or decrease the number of stages according to the situation. The common mode voltage is half of the amplifier power supply voltage. The amplifier is powered by a single power supply. In applications, positive and negative power supplies can also be used depending on the situation. Amplifier Ra i l to Ra i l (rail-to-rail) with low offset and high gain-bandwidth product.

Figure 2 shows the sensing module using the sensing coil. Other low-frequency sensing methods such as Hall sensor or giant magnetoresistance can be used depending on the situation, as shown in Figure 3 and Figure 4.

The examples in Figures 2 to 4 describe the low-frequency sensing signal using a single-ended input. Depending on the application, a differential input can also be used. As shown in Figure 5, the first stage uses differential input, single-ended output. The first stage output introduces RC passive low-pass filtering, the latter four stages adopt single-pole filtering method, the input end introduces RC high-pass filtering, and the feedback end introduces RC low-pass filtering to determine the lower limit cutoff frequency and the upper limit cutoff frequency respectively. The common terminal is VCM (VDD/2), which satisfies the sensing signal with VDD/2 as the center axis up and down to avoid distortion of the waveform. The advantage of introducing this method is to increase the common mode rejection ratio and reduce common mode noise. In this example, the amplifier uses a single-ended output op amp. According to the actual situation, the differential input and differential output modes can also be selected.

FIG. 6 is a flowchart of a method for detecting a low frequency signal according to an embodiment of the present invention. The detection of low frequency signals includes the following steps:

Step 601, measuring amplitude values of induced voltages after amplification at different distances;

Through experimental means, the amplitude values of the induced voltage of the magnetic induction module and the magnetic field-transmitting card reader at different distance points are amplified by the amplifier on the different mobile phone terminals, and corresponding records are made.

Step 602: Establish a correspondence table between the amplitude value and the distance.

The measurement data of a plurality of terminals is processed to obtain a correspondence table of amplitude values and distances.

Step 603, entering a low frequency magnetic field data decoding process;

Step 605, comparing threshold settings;

The distance to be decoded is D2, and the correspondence table between the amplitude value and the distance is searched, and the variation range of the signal corresponding to D2 is +A2 to -A2, and the amplitude of most noise is measured as A3, and the level of output to the comparator is set. L3, L4, such that L3 should be greater than +A3 and less than +A2; L4 is less than -A3 and greater than -A2, that is, decoding is allowed when the distance is less than D2, otherwise decoding is not allowed.

Step 607, comparing the delayed output signal after the decision;

Step 609, decoding the processed signal;

The decoder decodes the logically processed signal according to the encoding format to obtain low frequency magnetic field data stream information. The decoder sets the digital glitch filter to perform glitch filtering on the input digital signal.

Step 611, completing one-way communication of the low frequency magnetic field signal;

The decoded data is correlated and applied to complete the one-way communication function of the low frequency magnetic field signal. Step 604, entering a distance control process;

Step 606, setting a signal proportional threshold and a comparison threshold;

If the distance to be controlled is D1, find the correspondence table between the amplitude value and the distance, and the signal change amplitude corresponding to D1 is +A1 to - A1, and the proportional threshold of the set 1 signal is R1. According to A1 and R1, the output is set to the comparator. The level Ll, L2, meets the output signal of the front-end device in one cycle The percentage of time that the amplitude is greater than L1 or less than L2 is equal to R1, that is, if it is greater than R1, it enters the range of the required control distance D1, otherwise it does not enter the range of the required control distance D1.

Step 608, comparing the output signal logic or processing after the judgment;

When a pair of comparison thresholds is used to obtain a digital signal for judging the distance between the card reader and the card, the pair of digital signals are operated as follows: the output signal after passing the high comparison threshold is determined to be low. The comparison threshold is performed after the decision output signal is inverted, and a digital signal for distance determination is obtained.

Step 61 0: The signal processed by the logic processing in step 608 is sampled to obtain a data stream of 0, 1; Step 612, the data of 0 and 1 is counted by using a preset time window;

The length of the time window is preset, and the 0 and 1 data in the time window are counted, and the ratio of 1 is calculated.

Steps 614 and 616, comparing the statistical result with the set signal threshold of the set 1 to complete the distance judgment and realizing the distance control.

FIG. 7 is a schematic diagram showing the correspondence between the distance and the amplitude value of the low-frequency sensing signal by the experimentally measured sensing module placed in different mobile communication terminals according to an embodiment of the present invention.

Table 1 is a table showing the correspondence between the amplitude value and the distance of the low frequency sensing signal in the embodiment of the present invention.

Table 1

Figure 8 shows the basic architecture of the analog-to-digital conversion circuit of the system. The A/D of this example uses a typical The successive comparison type includes a voltage follower A and an analog to digital converter core module 8. Among them, the voltage follower A is mainly used to stabilize the analog amplified signal of the amplifier output, avoiding the voltage drift caused by the high resistance of the A/D front end, resulting in distortion of the analog-to-digital conversion. The common mode input port uses the same common mode voltage VCM of the front end amplifier. C10 is the sampling capacitor, and the capacitance is selected according to the sampling rate.

In this example, the reference voltage Vref>=amplifier analog amplified signal V0UT is selected, and the parallel digital output is used, and the number of bits is selected to be more than 8 bits.

The DO shown in Figure 9 is the output signal of the digital-to-analog converter after converting the input signal of the amplifier. The high comparison threshold and the low comparison threshold are set according to the decoding distance and with reference to the correspondence table of the amplitude value and the distance. D02 is the output signal of the analog-to-digital converter output signal compared with the high comparison threshold. D03 is the output signal of the analog-to-digital converter output signal compared with the low comparison threshold. D04 is a signal obtained by delaying the compared signals D02 and D03. This signal is input to the decoder for decoding the data. The decoder can set a digital glitch filter to perform glitch filtering on the input signal, and the decoder decodes the logically processed signal according to the encoding format to obtain low frequency magnetic field data stream information.

The DO shown in the figure is the output signal of the digital-to-analog converter after converting the input signal of the amplifier. Its amplitude varies from -A1 to +A1 and its corresponding distance is L. Assuming that the distance L needs to be controlled, first look up the correspondence table of the amplitude value and the distance to obtain the signal amplitude value at the distance. Set the proportional threshold of the 1 signal to R1. According to R1, the high comparison threshold VG+ and the low comparison threshold VG- are set such that the percentage of time that the front-end device output signal amplitude is greater than VG+ or less than VG- is equal to R1 in one cycle. After a pair of comparison threshold decisions, the output signals D02 and D03 are processed or processed to obtain a signal D04, and the signal is sampled to obtain a sampled 0, 1 data stream D5. In the figure, the dotted line box on the 0 and 1 data streams represents the preset time window. The length of the time window is set equal to one signal period. The 0 and 1 signals in the time window are counted, and the ratio of the 1 signal is obtained. The proportional threshold of the signal is compared. If it is greater than the proportional threshold, the sensing module is considered to be within the distance L; otherwise, the distance is not considered to be entered.

11 is a schematic diagram of decoding processing using a magnetic field data low frequency signal detecting method using a single comparison threshold in an embodiment of the present invention; The DO shown in the figure is the output signal of the digital-to-analog converter after analog-to-digital conversion of the amplifier input signal. The comparison threshold is set to the amplifier input reference level. The compared signal is directly input to the decoder as a decoder input digital signal. The decoder sets a digital glitch filter to glitch the input signal. The decoder decodes the logically processed signal according to the encoding format to obtain low frequency magnetic field data stream information. Schematic diagram of distance control processing;

The DO shown in Figure 12 is the output signal of the digital-to-analog converter that converts the amplifier input signal. Its amplitude varies from -A1 to +A1 and its corresponding distance is L. Assuming that the distance L needs to be controlled, first look up the correspondence table of the amplitude value and the distance to obtain the signal amplitude value at the distance. Set the proportional threshold of the 1 signal to R1. According to R1, the comparison threshold VG is set to be equal to Rl in a period in which the front-end device output signal amplitude is greater than VG. The output signal D01 after the comparison judgment is sampled, and the sampled 0, 1 data stream D02 is obtained. In the figure, the dotted line box on the 0 and 1 data streams represents the preset time window. The length of the time window is set equal to one signal period. The 0 and 1 signals in the time window are counted, and the ratio of the 1 signal is obtained. The proportional threshold of the signal is compared. If it is greater than the proportional threshold, the sensing module is considered to be within the distance L; otherwise, the distance is not considered to be entered.

Obviously, it is also possible to use a plurality of single comparison thresholds to output a digital signal for multiple distance and code stream determination, or to use a plurality of pairs of comparison thresholds to output a digital signal for multiple distances, multiple distance intervals, and The judgment of the code stream; the digital signal outputted after the comparison of the plurality of single comparison thresholds and the digital signals outputted by the comparison of the plurality of comparison thresholds may be used to determine the plurality of distances, the plurality of distance intervals, and the code stream.

13 is a block diagram of a system structure of a low-frequency alternating magnetic field short-distance detection combined with radio frequency high-frequency communication according to the present invention, as shown in the figure: The system includes a radio frequency communication terminal and a short-range radio frequency communication device, and the radio frequency communication terminal includes a low-frequency alternating magnetic field signal. a receiving circuit, a device for detecting and transmitting short-range low-frequency magnetic field signals and a distance determination connected to the low-frequency alternating magnetic field signal receiving circuit, and a device for detecting and transmitting low-frequency magnetic field signals and distance determination for close range Radio frequency transceiver circuit for bidirectional communication of radio frequency communication equipment.

During operation, the short-range RF communication device transmits a low-frequency alternating magnetic field signal, and the radio frequency communication terminal receives the magnetic field signal through the low-frequency alternating magnetic field signal receiving circuit, and transmits the magnetic field signal to the low-frequency magnetic field signal. The device for detecting and transmitting and distance judging finally realizes bidirectional distance communication by using the radio frequency transceiver circuit and the short-range radio frequency communication device.

According to the above description, the present invention can perform low frequency weak signal pre-amplification, analog-to-digital conversion, and field strength detection and data communication.

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.

Claims

Claim

A device for detecting and transmitting short-range magnetic field signals and determining a distance, comprising: at least one low-frequency sensing module for sensing a low-frequency magnetic field signal, at least one amplifier for amplifying a low-frequency sensing signal, and At least one analog to digital converter coupled to the output of the amplifier, and a digital processing module coupled to the analog to digital converter for determining the strength of the original signal and completing the signal detection output.

2. The device according to claim 1, wherein the low frequency sensing module is an induction coil, a Hall sensor, or a giant magnetoresistance.

3. Apparatus according to claim 1 wherein said amplifier is cascaded in a multi-stage amplifier.

4. Apparatus according to claim 1 or 3, characterized in that the amplifier is a single-ended amplifier or a differential amplifier.

5. The apparatus according to claim 3, wherein each of the cascaded multi-stage amplifiers is connected to a high-pass filter circuit, each stage output is connected to a low-pass filter circuit, and the amplifier is low offset and high gain. Bandwidth product amplifier.

6. The apparatus according to claim 1, wherein the analog to digital converter employs a parallel analog to digital converter.

7. Apparatus according to any of claims 1, 3, 5 or 6, wherein said analog to digital converter has a rate greater than 1 KSPS and an input range of 0 volts to an analog to digital converter reference voltage.

The apparatus according to any one of claims 1, 3, 5 or 6, wherein the input end of the analog-to-digital converter is provided with a voltage follower connected to the amplifier.

9. The apparatus according to claim 1, wherein a digital glitch filter for puncturing the digital signal is disposed between the analog to digital converter and the digital processing module.

10. A system for low frequency alternating magnetic field proximity detection combined with radio frequency high frequency communication, comprising a radio frequency communication terminal and a short range radio frequency communication device, wherein the radio frequency communication terminal comprises the method of any one of claims 1 to 8. And a device for detecting and transmitting short-range magnetic field signals and distance, and connecting the device for detecting and transmitting short-range magnetic field signals and determining distance for transmitting and receiving radio signals for bidirectional communication with a short-range radio communication device Circuit.

11. A method for detecting and transmitting short-range magnetic field signals and distance determination, method Includes:

Step b: according to the requirement of decoding the low-frequency signal transmission data and controlling the swipe distance, combined with the signal-to-noise ratio requirement, determining the output signal of the analog-to-digital converter by comparing the threshold to form the hysteresis decision voltage threshold, and obtaining the code stream information transmitted by the low-frequency magnetic field; By comparing the threshold to form a non-hysteresis decision voltage threshold, the output signal of the analog-to-digital converter is determined, and the distance characteristic information transmitted by the low-frequency magnetic field is obtained; Step c: sampling the signal after the non-hysteresis decision condition is obtained to obtain a 0, 1 code stream sequence, Set the 1 signal proportional threshold, and count the code stream sequence within the set time window length. When the ratio of the code stream occupied by the 1 signal reaches the preset proportional threshold, it is considered to enter the set distance range, otherwise it is considered not to enter. The range of distances; decoding the signal sequence after the decision of the hysteresis decision condition, extracting the code stream information of the low frequency magnetic field, and completing the one-way communication of the low frequency magnetic field signal.

The method for detecting a short-range low-frequency signal detecting and transmitting system according to claim 11, wherein in the step b, according to the correspondence table of the amplitude value and the distance in the step a, the decoding distance and the distance are combined. Control requirements, set the proportional threshold of the 1 signal to set the comparison threshold within the digital processing module.

The method for detecting and transmitting a low-frequency signal according to claim 11, wherein in the step b, the magnetic field distance information is extracted using a single, a plurality of single, a pair, a plurality of pairs of comparison thresholds, or a combination thereof. And code stream information.

The method for short-range low-frequency signal detection and transmission system according to claim 13, wherein a pair of comparison thresholds in the digital processing module is a non-hysteresis decision condition, and the setting method is: setting a desired control The distance is D1, and the correspondence table between the amplitude value and the distance is found. The signal variation amplitude corresponding to D1 is +A1 to -A1, and the proportional threshold of the setting 1 signal is R1. According to A1 and R1, the level L1 output to the comparator is set. And L2, satisfying that in a period, the percentage of time that the output signal amplitude of the front end device is greater than L1 or less than L2 is equal to R1, that is, if the value is greater than R1, the distance D1 of the required control is entered, otherwise the required control distance D1 is not entered. Within the scope.

The method for short-range low-frequency signal detection and transmission system according to claim 13, wherein a pair of comparison thresholds in the digital processing module is a hysteresis decision condition, and the setting method is: if decoding is desired The distance is D2, and the correspondence table between the amplitude value and the distance is found, and D2 is obtained. The corresponding signal varies from +A2 to -A2. The amplitude of most noise is measured as A3. Set the level of output to the comparator L 3, L4 so that L 3 should be greater than +A3 and less than +A2 ; L4 Less than -A3, and greater than -A2, that is, when the distance is less than D2, decoding is allowed, otherwise decoding is not allowed.

The method for detecting and transmitting a low-frequency signal according to claim 14, wherein in the step b, the two output signals determined by using a pair of non-hysteresis decision conditions are logically processed, A digital signal for extracting distance information is obtained after processing.

The method for detecting and transmitting a low-frequency signal according to claim 15, wherein in the step b, the two output signals judged by using a pair of hysteresis decision conditions are subjected to hysteresis processing, hysteresis processing A digital signal for extracting the magnetic field code stream information is then obtained.

18. A method for low frequency signal detection and transmission system according to claim 13 wherein when a single comparison threshold is used to extract magnetic field code information, the comparison threshold is set to an amplifier input reference level; when a single comparison threshold is used When the comparison level is extracted to extract the magnetic field distance information, the comparison threshold setting method is identical to the method of claim 16.

19. A method for low frequency signal detection and transmission system according to claim 13 wherein said method uses a single comparison threshold to output a digital signal for single distance and code stream determination, or a pair The digital signal outputted after the comparison threshold is compared to determine a single distance and a code stream; the method uses a plurality of single comparison thresholds to output a digital signal for judging a plurality of distances and code streams, or using a plurality of pairs of comparison thresholds after comparison The output digital signal is judged by multiple distances, multiple distance intervals, and code streams.

20. The method for low frequency signal detection and transmission system according to claim 13, wherein the method mixes a digital signal outputted after comparing a plurality of single comparison thresholds with a plurality of pairs of comparison thresholds and outputs the number after comparison. The signal is judged by multiple distances, multiple distance intervals, and code streams.

The method for detecting and transmitting a low-frequency signal according to claim 11, wherein the step c includes a step of performing glitch filtering on the input digital signal, and then filtering the signal from the glitch The low frequency magnetic field data stream is decoded.