A desktop card dispenser based on RFID chip

Abstract

The application discloses a desktop card dispenser based on an RFID chip and relates to the field of radio frequency identification technology. The application compares a pre-stored protocol feature library with a preamble bit segment, automatically identifies EPC / Guobiao label protocol types, and exempts from manual sorting operation. In combination with a first-different-later-same strategy of a composite handshake instruction sequence, protocol camouflage handshake is completed within a preset time window, multi-protocol conversion delay is significantly shortened, and label response timeout failure is avoided. A TID grouping processing module divides operation batches according to a predetermined bit position of a unique label code, executes a protocol camouflage process on different grouping labels in sequence, isolates response time sequences from a physical layer, and reduces signal collision probability in a dense label scene. When the number of labels exceeds a set threshold, the grouping mechanism is automatically enabled, so that the stability of batch card dispensing operation is ensured. A tunable pi-type impedance network dynamically optimizes an antenna standing wave ratio according to label distance, and expands an effective reading and writing range.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radio frequency identification technology, and in particular to a desktop card dispenser based on an RFID chip. BACKGROUND

[0002] In the cross-border logistics scenario, goods need to meet the RFID standard requirements of different countries; taking Sino-US international cooperation as an example, the same batch of goods often mix and paste EPCGen2 and GB / T29768 two types of labels; the desktop card dispenser needs to perform data writing and authorization operation on the two types of labels, but the two protocols have underlying differences in instruction set, timing interaction and encoding method.

[0003] The existing desktop card dispenser system mostly adopts a dual-protocol switching mode, an independent radio frequency channel is built-in the device, and EPC or GB / T protocol stack is loaded respectively through software configuration; manual pre-sorting of labels is required during operation, and the labels are processed in batches according to the protocol type; some high-end models support protocol automatic identification function, which relies on the specific preamble characteristics returned by the label to trigger protocol switching, such as the 4-bit preamble of Gen2.

[0004] However, in actual application, the dual-protocol switching scheme has protocol conversion delay in the mixed issuing scenario, which can cause some labels to respond timeout and fail, especially when the distance between Gen2 and GB / T labels is less than 10 cm, the radio frequency interference can mask the preamble characteristics; manual sorting cannot fundamentally solve the problem, and special labels with standard differentiation need additional operation processes, such as Japanese ARIBSTD-T109; in addition, the protocol conflict probability increases sharply when multiple labels are concurrent, and the system needs to retry multiple times to complete a single batch operation; therefore, a desktop card dispenser based on an RFID chip is needed to solve such problems. SUMMARY

[0005] In view of the above existing problems, the present application is proposed.

[0006] The present application provides a desktop card dispenser based on an RFID chip to solve the problems of protocol conversion delay, manual sorting dependence and concurrent conflict of the existing desktop card dispenser system in the mixed issuing scenario of cross-border logistics multi-protocol labels.

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] The present application provides a desktop card dispenser based on an RFID chip, which comprises a radio frequency module, a control module and a protocol camouflage handshake module, wherein:

[0009] The protocol camouflage handshake module is configured to perform the following steps:

[0010] a) receiving backscattering signals of an RFID tag to be operated by the radio frequency module, and extracting a preamble bit segment of a predetermined length;

[0011] b) comparing the preamble bit segment with a pre-stored protocol feature library to identify a protocol type of the RFID tag;

[0012] c) generating a composite handshake instruction sequence according to the identification result, the sequence comprising:

[0013] a first instruction: a query instruction inconsistent with the identified protocol type;

[0014] a second instruction: a selection instruction consistent with the protocol type of the RFID tag;

[0015] wherein the second instruction is sent within a preset time window after the first instruction is sent;

[0016] d) if no valid response is received, re-sending the composite handshake instruction sequence according to a retry strategy, the retry strategy comprising exchanging the sending order of the first instruction and the second instruction.

[0017] As a preferred scheme of the desktop card dispenser based on the RFID chip, in the process of extracting the preamble bit segment of the predetermined length:

[0018] a down-conversion output of the radio frequency module is sampled by an ADC to obtain a baseband discrete sequence r[n]; to locate a preamble starting point, a sliding correlation value is calculated at each sampling index n, and the formula is:

[0019]

[0020] wherein C[n] is the correlation value at the index n, in volts, r[n] is the n-th baseband sampling amplitude, in volts, k is a local index within a correlation window, dimensionless, L p is the preamble bit length, in bits, and p[k] is the k-th bit of the preamble, 0 or 1;

[0021] after energy normalization in the same window, an adaptive threshold is set to suppress channel gain fluctuations, and is expressed as:

[0022]

[0023] wherein T is the detection threshold, in volts, and a is a threshold proportionality coefficient, dimensionless;

[0024] The threshold proportionality coefficient is determined according to an expected false alarm probability P fa from a Gaussian statistical model, and the formula is:

[0025]

[0026] where Q -1 (·) is the inverse Gaussian Q function, dimensionless, P fa is the false alarm probability, and σ is the noise standard deviation in volts;

[0027] When C[n]>T, record the detection index as n d , n d denotes the detected preamble starting sample index, and L d consecutive samples are intercepted from n p and a binary decision is made:

[0028]

[0029] where b[i] is the extracted i-th preamble bit, 0 or 1, i is the bit index, dimensionless, and sgn(·) is the sign function, taking values +1 or -1.

[0030] As a preferred scheme of the desktop card dispenser based on the RFID chip, the protocol feature library comprises:

[0031] a first feature template corresponding to the combination feature of the EPCClass-1 Generation-2 preamble 0100, RTcal and TRcal;

[0032] a second feature template corresponding to the combination feature of the GB / T 29768-2013 preamble 0101 and the reverse link minimum rate.

[0033] As a preferred scheme of the desktop card dispenser based on the RFID chip, the protocol type identification step comprises:

[0034] The extracted preamble bit segment b[i] is first mapped into a bipolar sequence:

[0035] s[i]=2b[i]-1,

[0036] where s[i] is the i-th bipolar value, taking values ±1, b[i] is the i-th binary bit, 0 or 1, i is the bit index, dimensionless;

[0037] Suppose the protocol feature library contains M template vectors t j [i], and the normalized correlation score is calculated for each template:

[0038]

[0039] where S j is the correlation score of template j, dimensionless, L p is the preamble bit length, and t j[i] is the i-th bit polarity of template j, ±1, j is the template index, 1 to M.

[0040] As a preferred scheme of the desktop card dispenser based on RFID chip, the protocol type identification step further comprises:

[0041] Mapping scores to probability space to suppress false positives:

[0042]

[0043] where P j is the matching probability of template j, 0-1 interval, β is the temperature coefficient, dimensionless, m is the summation variable index, 1 to M, M is the total number of templates;

[0044] Adaptive setting of temperature coefficient according to score dispersion:

[0045]

[0046] where σ S is the standard deviation of all S j , dimensionless;

[0047] The final recognition result is the template corresponding to the maximum probability:

[0048]

[0049] where, is the index of the protocol type to be identified, dimensionless.

[0050] As a preferred scheme of the desktop card dispenser based on RFID chip, the retry strategy of step d) further comprises:

[0051] Reducing the radio frequency transmission power;

[0052] Inserting a time window and listening to the tag response.

[0053] As a preferred scheme of the desktop card dispenser based on RFID chip, further comprising a TID grouping processing module for:

[0054] Reading the TID code of the RFID tag;

[0055] Grouping according to the predetermined bit of the TID code;

[0056] Executing steps a)-d) on different groups of tags in turn.

[0057] As a preferred scheme of the desktop card dispenser based on the RFID chip, the radio frequency module further comprises an adjustable pi-type impedance matching network, which is used for estimating the distance between the RFID tag and the antenna according to the RSSI (Received Signal Strength Indication) in the process of executing the composite handshake instruction sequence; and when the estimated distance is greater than a preset threshold, the reactance parameter of the pi-type impedance matching network is adjusted to optimize the VSWR (Voltage Standing Wave Ratio) of the antenna.

[0058] As a preferred scheme of the desktop card dispenser based on the RFID chip, the working frequency band of the radio frequency module can be switched between 902MHz-928MHz and 920.5MHz-924.5MHz, and the transmission carrier frequency is synchronously adjusted to the center frequency of the frequency band corresponding to the RFID tag protocol specification when the composite handshake instruction sequence is executed.

[0059] As a preferred scheme of the desktop card dispenser based on the RFID chip, the TID grouping processing module is started when the number of simultaneously detected RFID tags exceeds a set threshold.

[0060] The present application has the following advantages: the present application automatically identifies the label protocol types such as EPC / Guobiao by comparing the pre-stored protocol feature library with the preamble bit segment, thereby eliminating manual sorting operation; the protocol camouflage handshake is completed within a preset time window by combining the first-foreign and then-same strategy of the composite handshake instruction sequence, thereby significantly shortening the multi-protocol conversion delay and avoiding label response timeout failure; the TID grouping processing module divides the operation batches according to the predetermined bit position of the unique code of the label, executes the protocol camouflage process on different grouped labels in sequence, isolates the response time sequence from the physical layer, and reduces the signal collision probability in the dense label scenario; the grouping mechanism is automatically enabled when the number of labels exceeds a set threshold, thereby ensuring the stability of batch card dispensing operation.

[0061] The adjustable pi-type impedance network of the present application dynamically optimizes the VSWR of the antenna according to the distance of the label, expands the effective reading and writing range, adaptively switches the working frequency band to synchronize the protocol specification requirement, suppresses frequency offset interference, improves the operation robustness in harsh environments such as metal shelves and liquid reagents by the retry strategy through power adjustment and delay time window monitoring, and supports the import of new protocol templates by the extensible design of the protocol feature library, thereby being adaptable to international standards such as ISO 18000-6D and ARC in the future; the impedance tuning and frequency band switching at the hardware layer are compatible with different frequency band labels, thereby providing a universal platform for global logistics applications. BRIEF DESCRIPTION OF DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0063] Figure 1 The frame diagram of the RFID chip-based desktop card dispenser in Embodiment 1. DETAILED DESCRIPTION

[0064] In order to make the above-mentioned objects, features and advantages of the present application more apparent and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the drawings.

[0065] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0066] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is independent of or selected from other embodiments.

[0067] Embodiment 1, refer to Figure 1 The embodiment provides an RFID chip-based desktop card dispenser, which comprises a radio frequency module, a control module and a protocol camouflage handshake module, and wherein:

[0068] The protocol camouflage handshake module is configured to perform the following steps:

[0069] a) receiving a backscattering signal of an RFID tag to be operated by the radio frequency module, and extracting a preamble bit segment of a predetermined length;

[0070] In the process of extracting the preamble bit segment of the predetermined length:

[0071] The down-conversion output of the radio frequency module is sampled by an ADC to obtain a baseband discrete sequence r[n]; in order to locate the start point of the preamble, a sliding correlation value is calculated at each sampling index n, and the formula is:

[0072]

[0073] wherein C[n] is the correlation value at index n, in volts, r[n] is the amplitude of the nth baseband sample, in volts, k is the local index within the correlation window, dimensionless, and L is the length of the preamble, in bits. p wherein p[k] is the kth bit of the preamble, 0 or 1.

[0074] After energy normalization in the same window, an adaptive threshold is set to suppress channel gain fluctuation, expressed as:

[0075]

[0076] wherein T is the detection threshold, in volts, and a is the threshold proportionality coefficient, dimensionless.

[0077] The threshold proportionality coefficient is determined according to the expected false alarm probability P fa determined by the Gaussian statistical model, with the formula:

[0078]

[0079] wherein Q -1 (·) is the inverse function of the Gaussian Q function, dimensionless, P fa is the false alarm probability, and s is the noise standard deviation, in volts.

[0080] When C[n] > T, the detection index is recorded as n d , wherein n d represents the detected preamble starting sample index, and the continuous L p samples from n d are extracted and subjected to binary decision:

[0081]

[0082] wherein b[i] is the ith bit of the extracted preamble, 0 or 1, i is the bit index, dimensionless, and sgn(·) is the sign function, taking values +1 or -1.

[0083] Specifically, the sliding correlation superimposes the preamble energy, and the peak value is significantly highlighted. The energy normalization threshold avoids the sensitivity of the fixed threshold to the transmission power or path loss. The threshold proportionality corresponds to the false alarm probability, which can be adjusted self-consistently through noise estimation. The detection index n d aligns the frame structure, and the subsequent symbol decision is quickly completed by the sign function, reducing the impact of multipath and phase jitter on the bit error rate. The overall formation of the correlation focusing energy evaluation statistical calibration binary decision extraction closed loop can still output the complete preamble bit segment in low SNR and multi-tag concurrent scenarios, providing reliable input for subsequent protocol feature comparison.

[0084] b) comparing the preamble bit segment with the pre-stored protocol feature library to identify the protocol type of the RFID tag;

[0085] The protocol feature library comprises:

[0086] a first feature template corresponding to the EPC Class-1 Generation-2 preamble 0100, RTcal and TRcal combination feature;

[0087] a second feature template corresponding to the GB / T 29768-2013 preamble 0101 and reverse link minimum rate feature;

[0088] The protocol type identification step comprises:

[0089] The extracted preamble bit segment b[i] is first mapped to a bipolar sequence:

[0090] s[i] = 2b[i] - 1,

[0091] where s[i] is the i-th bipolar value, taking ±1, b[i] is the i-th binary bit, 0 or 1, and i is the bit index, dimensionless;

[0092] Suppose the protocol feature library contains M template vectors t j [i], and the normalized correlation score is calculated for each template:

[0093]

[0094] where S j is the correlation score of template j, dimensionless, L p is the preamble bit length, bits, t j [i] is the i-th bipolar value of template j, ±1, and j is the template index, 1 to M;

[0095] The protocol type identification step further comprises:

[0096] Mapping the scores to a probability space to suppress false high matches:

[0097]

[0098] where P j is the matching probability of template j, in the interval 0-1, β is the temperature coefficient, dimensionless, m is the summation variable index, 1 to M, and M is the total number of templates;

[0099] Adaptively setting the temperature coefficient according to the score dispersion:

[0100]

[0101] where σ S is the standard deviation of all S j , dimensionless;

[0102] The final recognition result takes the template corresponding to the maximum probability:

[0103]

[0104] wherein, is the index of the protocol type to be identified, dimensionless;

[0105] Specifically, the bipolar mapping preserves the phase information and suppresses the DC drift, the correlation score is normalized by bit length to offset the label distance and transmit power difference; the temperature soft maximum maps the linear score to probability, avoiding the misjudgment of weak templates caused by simple maximum correlation; the temperature coefficient is self-adjusted with the score dispersion, amplifying the maximum value advantage at high dispersion and smoothing the probability distribution at low dispersion, improving the discrimination reliability in complex environments; the whole process forms a coherent closed loop by mapping correlation normalization to probability optimization for optimal judgment, which can quickly output robust protocol type recognition results under the conditions of multiple protocol coexistence and channel noise fluctuation;

[0106] c) generating a composite handshake instruction sequence according to the recognition result, the sequence comprising:

[0107] The first instruction: a query instruction inconsistent with the identified protocol type;

[0108] The second instruction: a selection instruction consistent with the protocol type of the RFID tag;

[0109] Wherein the second instruction is sent within a preset time window after the first instruction is sent;

[0110] d) If no valid response is received, resend the composite handshake instruction sequence according to the retry strategy, and the retry strategy includes exchanging the sending order of the first instruction and the second instruction;

[0111] The retry strategy of step d) further comprises:

[0112] Lower the radio frequency transmit power;

[0113] Insert a delay time window and listen for the tag response;

[0114] Further comprising a TID grouping processing module for:

[0115] Reading the TID code of the RFID tag;

[0116] Grouping according to the predetermined bit position of the TID code;

[0117] Executing steps a)-d) on different grouped tags in turn;

[0118] When the number of RFID tags detected simultaneously exceeds a set threshold, the TID grouping processing module is started;

[0119] The radio frequency module further comprises an adjustable pi-type impedance matching network, which is used for estimating the distance between the RFID tag and the antenna according to the RSSI (Received Signal Strength Indication) during the execution of the composite handshake instruction sequence; when the estimated distance is greater than a preset threshold, the reactance parameter of the pi-type impedance matching network is adjusted to optimize the VSWR (Voltage Standing Wave Ratio) of the antenna;

[0120] The working frequency band of the radio frequency module can be switched between 902MHz-928MHz and 920.5MHz-924.5MHz, and the transmitting carrier frequency is synchronously adjusted to the center frequency of the frequency band corresponding to the RFID tag protocol specification when the composite handshake instruction sequence is executed.

[0121] The desktop card issuing system described in the application takes the radio frequency module as the front end, the control module as the center, and the protocol camouflage handshake module as the algorithm core, and realizes the seamless batch writing and authorized operation of EPC standard tags and GB / T standard tags through the integrated design of software and hardware. The system first completes the preamble capture and frame structure alignment at the radio frequency physical layer, then quickly judges the tag protocol type through template feature comparison at the baseband side, and then generates a composite handshake sequence containing a non-matching query instruction and a matching selection instruction, initiates double interaction to the target tag in a single communication window, greatly reduces the blank time and redundant retries caused by the need to switch protocols and re-search cards in the traditional scheme. If there is no effective response in the current time slot, the system automatically adjusts the interaction order, backfires the transmission power, and inserts a random listening delay according to the preset retry strategy, so as to suppress the conflict probability caused by near-distance tag coupling and same-frequency interference, and ensure that the writing success rate remains stable in a dense environment.

[0122] When the number of tags is too large, the control module calls the TID grouping processing module to process the tags according to the chip manufacturer identifier or the custom bit segment, so that the radio frequency characteristics within the same group remain consistent, thereby further reducing the collision retry number and simplifying the load of the host computer data channel. The system also sets an adjustable impedance matching network at the radio frequency front end, and combines a real-time RSSI distance estimation mechanism to dynamically adjust the reactance parameter when detecting that the VSWR of the antenna is deteriorated or the distance of the tag is increased, so that the backscatter link maintains a low reflection loss. For different supervision frequency bands required by cross-border logistics, the radio frequency module can smoothly switch between the internationally common bandwidth and the domestically licensed bandwidth, and the control module automatically matches the corresponding center frequency while initiating handshake in the downlink, avoiding manual multiple configurations and ensuring that the whole machine completes efficient card issuing within the compliant power.

[0123] In summary, the application forms a closed-loop cooperation in protocol automatic identification, handshake timing organization, power control, antenna matching, frequency band switching, and tag grouping, etc. Compared with the traditional dual-protocol switching scheme, the application can significantly reduce the protocol conversion delay, preamble misjudgment rate, and write failure rate in the multi-tag mixed transmission scenario, improve the whole batch processing throughput, reduce the manual sorting and repeated operation cost, has the advantages of simple implementation, good compatibility, high stability, and can be widely applied to the customs supervision warehouse, third-party logistics center, manufacturing flexible packaging line, and other desktop card issuing scenarios that need to handle multiple protocol RFID tags at the same time. Since the function boundaries of each module are clear, the hardware interface and software algorithm support modular expansion, and in the future, security encryption instructions, data integrity verification, or other regional protocol templates can be further integrated according to business needs to maintain the forward compatibility of the system. At the same time, the core idea of the application is not limited to a specific chip model or antenna form, and under the condition that the main steps and module structure remain unchanged, it can be flexibly tailored or parameter reconstructed according to different product specifications without affecting the essence of the application, so the protection scope is subject to the claims. In addition, the production and debugging process of the whole system is simple, the required materials can be directly obtained on the market, which is convenient for industrialization landing and reduces the manufacturing cost.

[0124] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A desktop card dispenser based on RFID chip, comprising a radio frequency module, a control module and a protocol camouflage handshake module, characterized in that: the protocol camouflage handshake module is configured to perform the following steps: a) receiving a backscatter signal of an RFID tag to be operated through the radio frequency module, and extracting a preamble bit segment of a predetermined length; b) comparing the preamble bit segment with a pre-stored protocol feature library to identify the protocol type of the RFID tag; c) generating a composite handshake instruction sequence according to the identification result, which comprises: a first instruction: a query instruction inconsistent with the identified protocol type; a second instruction: a selection instruction consistent with the protocol type of the RFID tag; wherein the second instruction is sent within a preset time window after the first instruction is sent; d) if no valid response is received, re-sending the composite handshake instruction sequence according to a retry strategy, which includes exchanging the sending order of the first instruction and the second instruction; the protocol feature library comprises: a first feature template corresponding to the combination features of EPCClass-1 Generation-2 preamble 0100, RTcal and TRcal; a second feature template corresponding to the combination features of GB / T 29768-2013 preamble 0101 and reverse link minimum rate feature.

2. A desktop card issuer based on an RFID chip as claimed in claim 1, characterized in that, In the process of extracting the preamble bit segment of a predetermined length: The down-conversion output of the radio frequency module is sampled by the ADC to obtain a baseband discrete sequence ; to locate the starting point of the preamble, a sliding correlation value is calculated at each sampling index , and the formula is: ， wherein, is an index is a correlation value in volts, is the first baseband sample amplitude in volts, is a local index within the correlation window, dimensionless, is a preamble bit length in bits, is the first preamble bit, having a value of 0 or 1. after the same window energy normalization, an adaptive threshold is set to suppress channel gain fluctuations, which is expressed as: ， wherein, is a detection threshold in volts, is a threshold proportionality coefficient, dimensionless; The threshold proportion coefficient is determined according to the expected false alarm probability is determined by a Gaussian statistical model, and the formula is: ， wherein is a Gaussian function inverse function, dimensionless, is a false alarm probability, is a noise standard deviation in volts; When the detection index is , denotes the detected preamble start sample index, the consecutive samples are taken from and a binary decision is made: ， ， wherein is the first is a preamble bit, taking values 0 or 1, is a bit index, dimensionless, is a sign function, taking values +1 or -1.

3. A desktop card issuer based on an RFID chip as defined in claim 1, characterized in that, the protocol type identification step comprises: Extracted preamble bit segment Mapping first to bipolar sequence: ， wherein, is the first bit bipolar value, taking values of +1 or -1, is the first bit binary bit, taking values in the range of 0 or 1, is the bit index, dimensionless; The protocol feature library contains a template vector, a normalized correlation score is calculated for each template: ， wherein, is a correlation score, dimensionless, is a template is a preamble bit length, in bits, is a template is a first bit polarity, taking values +1 or -1, is a template index, taking values from 1 to .

4. A desktop card issuer based on an RFID chip as claimed in claim 3, characterized in that, the protocol type identification step further comprises: mapping the score to a probability space to suppress false high matching: ， wherein, is the matching probability of the template , taking values in the interval [0, 1], is the temperature coefficient, dimensionless, is the summation variable index, taking values in the interval [1, T], , is the total number of templates; adaptively setting the temperature coefficient according to the score dispersion: ， wherein the standard deviation of all the standard deviation of all the final identification result takes the maximum probability corresponding template: ， wherein, is the index of the protocol type identified, dimensionless.

5. A desktop card issuer based on an RFID chip as defined in claim 1, wherein, the retry strategy of step d) further comprises: reducing the radio frequency transmission power; inserting a delay time window and listening to the tag response.

6. A desktop card issuer based on an RFID chip as defined in claim 1, wherein, Further comprising a TID grouping processing module for: reading the TID code of the RFID tag; grouping according to the predetermined bit of the TID code; performing steps a)-d) on different grouped tags in turn.

7. A desktop card issuer based on an RFID chip as claimed in any of claims 1 to 6, characterized in that, The radio frequency module further comprises an adjustable π-type impedance matching network, which is used to estimate the distance between the RFID tag and the antenna according to the reverse scattering signal intensity indication (RSSI) during the execution of the composite handshake instruction sequence; when the estimated distance is greater than a preset threshold, the reactance parameter of the π-type impedance matching network is adjusted to optimize the standing wave ratio of the antenna.

8. A desktop card issuer based on an RFID chip as defined in claim 7, characterized in that, The working frequency band of the radio frequency module can be switched between 902MHz-928MHz and 920.5MHz-924.5MHz, and the transmission carrier frequency is adjusted to the center frequency of the frequency band corresponding to the protocol specification of the RFID tag when the composite handshake instruction sequence is executed.

9. A desktop card issuer based on an RFID chip as defined in claim 6, wherein, When the number of RFID tags detected simultaneously exceeds a set threshold, the TID grouping processing module is started.

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