A transceiver completely separated type RFID system and a signal mode detection method based on the system

Abstract

The application discloses a kind of transceiver complete separation type RFID system and signal mode detection method based on the system, system includes transmitting unit, transmitting unit is connected signal transmitter by signal generation host computer, signal transmitter connects transmitting antenna;Signal excited tag by transmitting unit, and through the way of backscattering, tag ID encoding modulation is sent, receiving unit includes receiving antenna, receiving antenna connects signal receiver, signal receiver connects signal acquisition host computer, carries out signal processing;Signal mode detection method is: to build system model, insert signal mode detection supervisory code in Miller coding, signal sending, receiving, signal filtering and digitization, signal mode detection, signal mode correction and decoding method;The application solves the problem of signal mode ambiguity in the RFID system of transceiver separation.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and specifically relates to an RFID system with completely separate transmitting and receiving capabilities and a signal mode detection method based on the system. Background Technology

[0002] Radio Frequency Identification (RFID) is a non-contact automatic identification technology. An RFID system mainly consists of two parts: a reader and an electronic tag. The working principle of an RFID system is as follows: First, the reader generates and radiates electromagnetic waves into the vicinity of the tag. Then, the tag receives the electromagnetic waves and converts them into DC voltage to power its built-in chip. Simultaneously, it uses backscatter modulation to transmit the identification ID information stored in the chip back to the reader. Since tags are usually passive and do not generate or transmit signals themselves, the tag's scattered signal maintains the same carrier frequency as the reader's transmitted signal. Finally, the reader receives the tag's scattered signal, demodulates and decodes it to obtain the tag's ID information. Because the reader's transmitted carrier needs to continuously output to power the tag, the co-frequency interference between the reader's transmitted signal and the tag's backscattered signal reduces the signal-to-noise ratio, limiting the operating distance of traditional RFID systems.

[0003] Most existing RFID systems are based on the traditional transceiver integrated system architecture, while a smaller portion are based on semi-transceiver and fully segregated system architectures. In the transceiver integrated architecture, the RF transmitter used to activate the electronic tag and the receiver receiving the scattered signal from the tag are deployed in the same location and often share a single local oscillator signal source. This introduces a large amount of interference from co-frequency transmitted signals into the receiving link, causing unstable reading performance and significantly limiting the system's ability to improve performance and signal transmission anti-interference capabilities. In the semi-transceiver integrated system, the RF transmitter and the receiver receiving the scattered signal from the tag are deployed in different locations but still share a single local oscillator signal source. In the fully segregated system, the RF transmitter and the receiver receiving the scattered signal from the tag are deployed in different locations and use their own independent local oscillator signal sources. The advantage of the transceiver integrated architecture is its simplicity and ease of deployment, but its coverage is limited. Semi-transceiver and fully segregated architectures allow for distributed collaborative networking, which is more difficult to deploy but offers wider coverage. In the physical and logical layers of communication, the ISO 18000-6 protocol specifies that the transmitter sends a modulated radio frequency (RF) signal in the 860-960MHz range to the tag. The tag receives this RF signal, converts it into chip operating energy, demodulates the information within, and simultaneously modulates the tag ID information onto an RF carrier before backscattering it to the reader receiver. In data communication between the electronic tag and the reader, the commonly used information encoding method is the Miller modulation subcarrier method. The rule is that the baseband Miller code undergoes a phase flip between two consecutive states of 0, and there is also a phase flip in the middle of the symbol representing data 1. Currently, the Milller subcarrier signal begins transmission through one of two seekers and typically ends with a 1-bit "dummy" data 1 signal.

[0004] Patent application CN111092633A discloses a system and method for improving the excitation distance of transmit-receive split backscatter communication. In this system and method, the exciter utilizes a repeater architecture to make the excitation signal transmitted by the exciter and the carrier signal transmitted by the receiver highly correlated, thereby preserving the corresponding phase noise, spectrum, and other errors in the excitation signal received by the receiver. The receiver receives its own transmitted carrier signal and the excitation signal transmitted by the exciter, along with their associated terminal feedback signals, in two separate paths. Then, in digital processing, the receiver uses its own transmitted carrier signal as a reference signal and reduces or eliminates the interference of phase noise, spectrum, and spatial multipath errors of the exciter's transmitted excitation signal on the terminal feedback signal through iterative equalization and other methods, thereby improving the excitation distance of the transmit-receive split backscatter communication system to the terminal. However, this system is complex, difficult to deploy, and its operating range is limited by the length of the radio frequency cable.

[0005] Patent application CN106549692A discloses a signal receiving method for a backscatter communication system. The main steps are: (1) Signal transmission: The signal source consists of a radio frequency (RF) source and a tag, and the RF source and tag are equipped with a single antenna; the tag is powered by the RF source, and the signal transmitted by the tag is modulated from the signal of the RF source as a carrier. The tag includes a backscatter antenna; (2) Signal reception: A combined receiver is used to receive the signal s(n) of the RF source and the backscatter signal c(n) of the tag. The combined receiver is equipped with M antennas, M≥1; (3) Signal detection: The signal received by the combined receiver is detected. This invention adopts a completely separate RFID communication system. The tag uses the switching antenna impedance to modulate the carrier signal to transmit information. However, the signal mode ambiguity caused by the change in the position of the receiver and the tag during the separation of transmission and reception is not considered in the signal detection process.

[0006] In a fully separate RFID system, the transmitter sends an RFID signal to the tag. The tag modulates the signal by modulating the reflection coefficient of its antenna. The receiver receives the signal and demodulates it. Due to changes in the position of the tag or the receiver, the phases of the signal sent by the transmitter and the signal reflected by the tag to the receiver are different. The synthesized vector signal will have modal ambiguity, making it impossible to accurately decode the 1 and 0 modes of the transmitted information. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention aims to propose a fully transceiver-separated RFID system and a signal mode detection method based on the system. By providing a mode supervision code inserted into Miller coding and providing a signal mode identification method and a signal mode correction and decoding method, the problem of signal mode ambiguity in the transceiver-separated RFID system is solved.

[0008] To achieve the above objectives, the present invention proposes the following technical solution:

[0009] A fully transceiver-separated RFID system includes: a transmitting unit, wherein a tag is excited by a signal emitted by the transmitting unit, and the tag ID is encoded and modulated and sent to a receiving unit by backscattering;

[0010] The transmitting unit includes a signal generating host computer, the output of which is connected to the input of a signal transmitter, the output of which is connected to the input of a transmitting antenna, and the output of which transmits a carrier signal to the receiving unit.

[0011] The receiving unit includes a receiving antenna. The input end of the receiving antenna receives the carrier signal transmitted by the output end of the transmitting antenna and the signal backscattered by the tag. The output end of the receiving antenna is connected to the input end of the signal receiver. The output end of the signal receiver is connected to the input end of the signal acquisition host computer, which performs signal processing.

[0012] The internal encoding program of the tag specifically involves replacing the flag data-1 with several consecutive low-level signals of 4 subcarrier cycles at the end of the Miller subcarrier modulation encoding. The tag modulates the transmitted information on the carrier signal by switching its load impedance, and the backscattered signal carrying the transmitted information is transmitted to the receiving unit.

[0013] The aforementioned low-level signals of four consecutive subcarrier cycles can be any combination of other high and low level signals of any number of subcarrier cycles greater than two.

[0014] A signal mode detection method based on a fully transceiver-separated RFID system includes the following steps:

[0015] Step 1: Build the system model;

[0016] Step 2: Design a signal coding algorithm and insert a signal mode detection check code into the Miller coding;

[0017] Step 3, signal transmission; after the host computer generates the control signal, it transmits the control signal to the signal transmitter. The signal transmitter continuously transmits carrier signals through the transmitting antenna; according to the signal encoding algorithm in step 2, the transmitted information is encoded and the encoding program is embedded in the tag chip. The tag modulates the transmitted information on the carrier signal by switching the load impedance and backscatters the signal carrying the transmitted information.

[0018] Step 4, signal reception; the signal receiver receives the carrier signal transmitted by the signal transmitter and the signal carrying the transmission information backscattered from the tag through the receiving antenna;

[0019] Step 5: The signal acquisition host computer performs signal filtering on the carrier signal and the signal carrying the transmission information obtained in step 4, and digitizes the carrier signal and the signal carrying the transmission information after signal filtering.

[0020] Step 6: The host computer performs signal mode detection on the carrier signal and the signal carrying the transmission information obtained in Step 5 after signal filtering and signal digitization.

[0021] Step 7: The host computer performs signal mode correction and decoding on the carrier signal and the signal carrying the transmission information that have undergone signal mode detection in Step 6.

[0022] The specific process for building the system model is as follows:

[0023] A transmitting unit is set up, consisting of a signal generation host computer connected to a signal transmitter, which in turn is connected to a transmitting antenna. The signal emitted by the transmitting unit excites the tag, and the tag ID is encoded, modulated, and transmitted through backscattering.

[0024] A receiving unit is set up, which includes a receiving antenna. The receiving antenna is connected to a signal receiver, which is connected to a signal acquisition host computer for signal processing.

[0025] The specific process of step 2 is as follows: at the end position of Miller subcarrier modulation coding, the flag data-1 is replaced with several consecutive low-level signals of 4 subcarrier cycles. The several consecutive low-level signals of 4 subcarrier cycles can be any number of other high and low level combination signals of subcarrier cycles greater than 2.

[0026] The specific process of step 5 is as follows: signal filtering includes digital bandpass filter and adaptive filtering. After the signal receiver receives the signal, the signal acquisition host computer first passes the original signal s1 through the bandpass filter to filter out noise interference and obtain the filtered signal s2. The original signal s1 is used as the input signal and the filtered signal s2 is used as the desired signal for adaptive filtering using an adaptive algorithm. An appropriate number of iterations is set to obtain the final signal s after filtering.

[0027] The specific process of signal digitization is as follows: the average dynamic signal amplitude of the final signal s after filtering is obtained as a function of time. The average dynamic signal amplitude is used as the signal threshold. The amplitude of the final signal s is compared with the threshold. If the amplitude is higher than the threshold, the level value is recorded as +1, otherwise it is recorded as -1. After digitizing the signal, the rising edge and falling edge positions are determined, and the number of sampling points per unit level of the signal is determined.

[0028] The specific process of signal mode detection in step 6 is as follows: mode detection is performed according to the signal encoding algorithm in step 2. The default signal mode is mode one. It is detected whether there are three consecutive sampling points with a unit level sample number that are high level. If the detection is true, then the signal mode is mode two; otherwise, it is still mode one.

[0029] Based on the signal mode detected in step 7, the level value of the digitized signal is recalibrated. The level value of the signal detected as mode two is multiplied by -1 and all are corrected to mode one before the signal decoding operation is performed.

[0030] The position of the signal seeker is found using a cross-correlation algorithm. This involves extracting the signal length by locating the start and end points of the seeker sequence, setting a sliding window with a size equal to the length of the encoded and modulated seeker sequence, and calculating the amplitude of the sampling points within the window and the cross-correlation value between the seeker sequences. The window with the largest cross-correlation value is found, and its position is recorded as the signal seeker. Starting from the seeker position, the signal is decoded according to the basic principles of Miller subcarrier modulation and coding in step 2 to restore the transmitted information.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. In step 2 of this invention, by inserting a signal mode detection supervision code into the Miller encoding, the end position marker in the original encoding rule is replaced with a mode supervision code, which has the characteristics of distinguishing and marking signal modes and is beneficial for judging signal modes in signal processing.

[0033] 2. In step 6 of this invention, signal mode detection has the advantage of accurately determining signal mode characteristics before signal decoding and solving signal mode ambiguity.

[0034] 3. In step 7 of this invention, the signal modes are unified through signal mode correction and decoding before decoding. Unifying the signal modes eliminates the multi-mode problem caused by the change of receiver and tag position during the transmission and reception separation. Decoding is performed when the signal is unified in mode one, which has the characteristics of improving signal decoding performance and reducing bit error rate.

[0035] 4. The signal filtering in step 5 of this invention uses an adaptive filter to take the original signal as the input signal and the denoised signal as the desired signal. The final filtered signal is obtained by iteratively using the adaptive filter algorithm. This effectively removes the influence of environmental noise and multipath effects on the signal, reduces the signal error rate, and accurately restores the transmitted information.

[0036] This invention is based on a completely separate RFID wireless communication system architecture, which allows transceivers to be deployed independently without being restricted by wired connections. It also proposes to add a signal mode detection supervision code method to the Miller subcarrier and design a corresponding decoding algorithm to solve the problem of signal mode ambiguity in the transceiver separation system. At the same time, the LMS algorithm is used in signal processing to reduce interference caused by spatial multipath and channel noise. Based on the above technical solutions, this invention can effectively improve the working distance of the RFID system and reduce the bit error rate. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the system structure of the present invention.

[0038] Figure 2 This is a comparison chart of encoding methods, in which... Figure 2 (a) is the original encoding method. Figure 2 (b) is a comparison diagram of the encoding methods after the addition of the supervision code algorithm in this invention.

[0039] Figure 3 This is a flowchart of the signal filtering process of the present invention.

[0040] Figure 4 This is a schematic diagram of the signal mode of the present invention.

[0041] Figure 5 This is a schematic diagram of the second signal mode of the present invention.

[0042] Figure 6 This is a flowchart of the signal mode detection algorithm of the present invention.

[0043] Figure 7 This is a diagram showing the experimental setup for an embodiment of the present invention.

[0044] Figure 8 The diagram shows a comparison of the original signal waveform and the signal waveform after passing through a bandpass filter, according to an embodiment of the present invention. Figure 8 (a) is the original signal waveform. Figure 8 (b) is the signal waveform after passing through the bandpass filter.

[0045] Figure 9 The diagram shows a comparison of the original signal waveform and the signal waveform after filtering by the adaptive filter, according to an embodiment of the present invention. Figure 9 (a) is the original signal waveform. Figure 9 (b) is the waveform of the signal after filtering by the adaptive filter.

[0046] Figure 10 For the positioning of the signal guide head in an embodiment of the present invention, wherein, Figure 10 (a) is the signal waveform after signal digitization and detection correction. Figure 10 (b) is the cross-correlation value between the amplitude of the signal sampling point and the leader sequence.

[0047] Figure 11 This is an output diagram showing the results of an embodiment of the present invention. Detailed Implementation

[0048] The present invention will now be described in further detail with reference to the accompanying drawings.

[0049] like Figure 1 As shown, a fully transceiver-separated RFID system includes: a transmitting unit, wherein the tag is excited by a signal emitted by the transmitting unit, and the tag ID is encoded and modulated and sent to the receiving unit by backscattering;

[0050] The transmitting unit includes a signal generating host computer, the output of which is connected to the input of a signal transmitter, the output of which is connected to the input of a transmitting antenna, and the output of which transmits a carrier signal to the receiving unit.

[0051] The receiving unit includes a receiving antenna. The input end of the receiving antenna receives the carrier signal transmitted by the output end of the transmitting antenna and the signal backscattered by the tag. The output end of the receiving antenna is connected to the input end of the signal receiver. The output end of the signal receiver is connected to the input end of the signal acquisition host computer, which performs signal processing.

[0052] The internal encoding program of the tag specifically involves replacing the flag data-1 with several consecutive low-level signals of 4 subcarrier cycles at the end of the Miller subcarrier modulation encoding. The tag modulates the transmitted information on the carrier signal by switching the load impedance, and the backscattered signal carrying the transmitted information is transmitted to the receiving unit.

[0053] The aforementioned low-level signals of four consecutive subcarrier cycles can be any combination of other high and low level signals of any number of subcarrier cycles greater than two.

[0054] A signal mode detection method based on a fully transceiver-separated RFID system includes the following steps:

[0055] Step 1: Build the system model.

[0056] A transmitting unit is set up, consisting of a signal generation host computer connected to a signal transmitter, which in turn is connected to a transmitting antenna. The signal emitted by the transmitting unit excites the tag, and the tag ID is encoded, modulated, and transmitted through backscattering.

[0057] A receiving unit is set up, which includes a receiving antenna. The receiving antenna is connected to a signal receiver, which is connected to a signal acquisition host computer for signal processing.

[0058] Step 2: Design a signal encoding algorithm and insert a signal mode detection supervision code.

[0059] The basic principle of Miller subcarrier modulation and coding is that a phase flip occurs in the middle of a logic 1 level; a phase flip occurs between two adjacent logic 0 levels; and no phase flip occurs during a logic 0 level. The Milller subcarrier coding method starts transmission via a seeker and ends with a 1-bit "dummy" data-1 signal. The signal mode detection check code method is designed to replace the original end position marker data-1 with several consecutive low-level signals of four subcarrier cycles. For example... Figure 2 As shown, where Figure 2(a) is the original encoding method structure diagram. Figure 2 (b) is the encoding diagram after adding the check code algorithm.

[0060] The period of the low-level signal can be of any length, and the low-level signal can be a combination of other high and low level signals.

[0061] Step 3, signal transmission: After the host computer generates a control signal, it transmits the control signal to the signal transmitter. The signal transmitter continuously transmits carrier signals through the transmitting antenna. Based on the information transmitted in Step 2, the signal is encoded and the encoding program is embedded in the tag chip. The tag modulates the transmitted information on the carrier signal by switching the load impedance and backscatters the signal carrying the transmitted information. The signal source consists of two parts: the signal transmitter and the tag.

[0062] Step 4, signal reception: The signal receiver receives the carrier signal and tag backscattered signal transmitted from the signal transmitter through the receiving antenna.

[0063] Step 5: The signal acquisition host computer performs signal filtering on the carrier signal and the signal carrying the transmission information obtained in step 4, and digitizes the carrier signal and the signal carrying the transmission information after signal filtering.

[0064] The signal filtering process includes digital bandpass filters and adaptive filtering:

[0065] After the signal receiver receives the signal, such as Figure 3 As shown, the signal acquisition host computer first passes the original signal s1 through a bandpass filter to filter out noise interference and obtain signal s2; then, using the LMS algorithm, the original signal s1 is used as the input signal and s2 is used as the desired signal for adaptive filtering; by setting an appropriate number of iterations, the filtered signal s is obtained.

[0066] Signal digitization: Calculate the average dynamic amplitude of the filtered signal s over time, use this average as the signal threshold, compare the amplitude of signal s with the threshold, record +1 if the amplitude is higher than the threshold, and -1 otherwise. After digitizing the signal, determine the rising and falling edge positions, and calculate the number of sampling points per unit level of the signal.

[0067] Step 6: Signal acquisition. The host computer performs signal mode detection, i.e., signal mode recognition, on the carrier signal and the signal carrying transmission information obtained in step 5 after signal filtering and signal digitization.

[0068] A transceiver-separated RFID system receives signals in two modes, as illustrated in the diagram below. Figure 4 , Figure 5As shown in step 2, when performing mode detection, the modal detection algorithm defaults to mode one. It then checks if there are three consecutive high-level sampling points (each with a unit level sample count). If the detection is true, the signal mode is mode two; otherwise, it remains mode one. The flowchart of the signal modal detection algorithm is shown below. Figure 6 As shown. After detecting the signal mode, the next step of signal decoding is performed according to the decoding algorithm to restore the transmitted information.

[0069] Step 7: The host computer performs signal mode correction and decoding on the carrier signal and the signal carrying the transmission information that have undergone signal mode detection in Step 6.

[0070] Based on the signal mode detected in step 6, the level value of the digitized signal is recalibrated. The level value of the signal detected as mode two is multiplied by -1 and all are corrected to mode one before the signal decoding operation is performed.

[0071] The position of the signal seeker is located using a cross-correlation algorithm, specifically by locating the start and end points of the seeker sequence to extract the signal length. A sliding window is set, with a size equal to the length of the encoded and modulated seeker sequence, to calculate the amplitude of the sampling points within the window and the cross-correlation value between the seeker sequences. The window with the largest cross-correlation value is then found, and its position is recorded; this window represents the signal seeker. Starting from the seeker position, the signal is decoded according to the basic principles of Miller subcarrier modulation and coding described in step two to reconstruct the transmitted information.

[0072] Example

[0073] Experiment setup such as Figure 7 As shown: The transmission and reception distance for the outdoor experiment is 30m.

[0074] like Figure 8 As shown, Figure 8 (a) is the original signal waveform. Figure 8 (b) is the signal waveform after passing through the bandpass filter. Although the signal after passing through the bandpass filter removes some of the influence of environmental noise, the signal waveform is still difficult to decode.

[0075] like Figure 9 As shown, Figure 9 (a) is the original signal waveform. Figure 9 (b) is the signal waveform after filtering by the adaptive filter. The signal waveform at this time can clearly observe the signal level change, and the effect of removing environmental influence is obvious. It can perform signal decoding well and greatly reduce the signal bit error rate.

[0076] like Figure 10 As shown, Figure 10(a) is a waveform diagram of the signal after digitization and detection correction. The blue and red circles indicate the start and end positions of the seeker. Figure 10 (b) is the cross-correlation value between the amplitude of the signal sampling points and the leader sequence, according to Figure 10 (b) Determine the position of the signal guide at the point where the cross-correlation value is the maximum, and determine the position where the transmission of information begins. Decoding starts from this point and proceeds to the parity code position.

[0077] Simulation results are as follows Figure 11 As shown, the system accurately decodes the transmitted information (the character "w") to achieve its functions.

Claims

1. A signal mode detection method based on a fully transceiver-separated RFID system, characterized in that, Includes the following steps: Step 1: Build the system model; Step 2: Design a signal coding algorithm and insert a signal mode detection check code into the Miller coding; At the end of Miller subcarrier modulation coding, the flag data-1 is replaced with several consecutive low-level signals for four subcarrier cycles; Step 3, Signal Transmission: After the host computer module generates the control signal, it transmits the control signal to the signal transmitter. The signal transmitter continuously transmits carrier signals through the transmitting antenna. According to the signal encoding algorithm in Step 2, the transmitted information is encoded and the encoding program is embedded in the tag chip. The tag modulates the transmitted information on the carrier signal by switching its load impedance and backscatters the signal carrying the transmitted information. Step 4, Signal Reception: The signal receiver receives the carrier signal transmitted by the signal transmitter and the signal carrying the transmission information backscattered from the tag through the receiving antenna; Step 5: The signal acquisition host computer performs signal filtering on the carrier signal and the signal carrying the transmission information obtained in step 4, and digitizes the carrier signal and the signal carrying the transmission information after signal filtering. Step 6: The signal acquisition host computer performs signal mode detection on the carrier signal and the signal carrying the transmission information obtained in step 5 after signal filtering and signal digitization. The specific process of signal mode detection in step 6 is as follows: mode detection is performed according to the signal encoding algorithm in step 2. The default signal mode is mode one. At this time, it is detected whether there are three consecutive sampling points with a unit level sampling number that are high level. If the detection is true, then the signal mode is mode two; otherwise, it is still mode one. Step 7: The signal acquisition host computer performs signal mode correction and decoding on the carrier signal and the signal carrying transmission information that have undergone signal mode detection in step 6.

2. The signal mode detection method based on a fully separate transmit / receive RFID system according to claim 1, characterized in that, The specific process of building the system model in step 1 is as follows: A transmitting unit is set up, consisting of a signal generation host computer connected to a signal transmitter, which in turn is connected to a transmitting antenna. The signal emitted by the transmitting unit excites the tag, and the tag ID is encoded, modulated, and transmitted through backscattering. A receiving unit is set up, which includes a receiving antenna. The receiving antenna is connected to a signal receiver, which is connected to a signal acquisition host computer for signal processing.

3. The signal mode detection method based on a fully transceiver-separated RFID system according to claim 1, characterized in that, The specific process of step 2 is as follows: the low-level signals of the several consecutive four subcarrier cycles are other high-low level combination signals of any number of subcarrier cycles greater than 2.

4. The signal mode detection method based on a fully transceiver-separated RFID system according to claim 1, characterized in that, The specific process of step 5 is as follows: signal filtering includes digital bandpass filter and adaptive filtering. After the signal receiver receives the signal, the signal acquisition host computer first passes the original signal s1 through the bandpass filter to filter out noise interference and obtain the filtered signal s2. The LMS algorithm is used to take the original signal s1 as the input signal and the filtered signal s2 as the desired signal for adaptive filtering. The number of iterations is set to obtain the final signal s after filtering. The specific process of signal digitization is as follows: the average dynamic signal amplitude of the final signal s after filtering is obtained as a function of time. The average dynamic signal amplitude is used as the signal threshold. The amplitude of the final signal s is compared with the threshold. If the amplitude is higher than the threshold, the level value is recorded as +1, otherwise it is recorded as -1. After digitizing the signal, the rising edge and falling edge positions are determined, and the number of sampling points per unit level of the signal is determined.

5. The signal mode detection method based on a fully transceiver-separated RFID system according to claim 1, characterized in that, Based on the signal mode detected in step 7, the level value of the digitized signal is recalibrated. The level value of the signal detected as mode two is multiplied by -1 and all are corrected to mode one before the signal decoding operation is performed. The position of the signal seeker is found using a cross-correlation algorithm. This involves extracting the signal length by locating the start and end points of the seeker sequence, setting a sliding window with a size equal to the length of the encoded and modulated seeker sequence, and calculating the amplitude of the sampling points within the window and the cross-correlation value between the seeker sequences. The window with the largest cross-correlation value is found, and its position is recorded as the signal seeker. Starting from the seeker position, the signal is decoded according to the basic principles of Miller subcarrier modulation and coding in step 2 to restore the transmitted information.

6. A fully transceiver-separated RFID system, used to implement the signal mode detection method based on a fully transceiver-separated RFID system as described in claim 1, characterized in that, include: The transmitting unit is used to excite the tag by the signal emitted by the transmitting unit, and the tag ID is encoded and modulated and sent to the receiving unit by backscattering. The transmitting unit includes a signal generating host computer, the output of which is connected to the input of a signal transmitter, the output of which is connected to the input of a transmitting antenna, and the output of which transmits a carrier signal to the receiving unit. The receiving unit includes a receiving antenna. The input end of the receiving antenna receives the carrier signal transmitted by the output end of the transmitting antenna and the signal backscattered by the tag. The output end of the receiving antenna is connected to the input end of the signal receiver. The output end of the signal receiver is connected to the input end of the signal acquisition host computer, which performs signal processing.

7. The RFID system with fully separated transmit and receive capabilities according to claim 6, characterized in that, The internal encoding program of the tag specifically involves replacing the flag data-1 with several consecutive low-level signals of 4 subcarrier cycles at the end of the Miller subcarrier modulation encoding. The tag modulates the transmitted information on the carrier signal by switching its load impedance, and the backscattered signal carrying the transmitted information is transmitted to the receiving unit.

8. The RFID system with fully separated transmit and receive capabilities according to claim 7, characterized in that, The aforementioned low-level signals of several consecutive four subcarrier cycles are other high-low level combinations of subcarrier cycles greater than two.

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