RFID reader-writer implementation method and system based on self-interference cancellation
By generating a reconstructed signal with the same amplitude but opposite phase as the self-interference signal in the RFID reader and performing vector synthesis, the self-interference is effectively canceled, solving the self-interference problem in compact RFID readers and improving receiving sensitivity and communication distance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-01-28
- Publication Date
- 2026-05-08
AI Technical Summary
In compact RFID readers, leakage of transmitted signals into the receiving channel causes self-interference signals, reducing the receiver's signal-to-noise ratio and limiting communication distance and tag identification reliability.
The transmitted signal is split into two paths by a coupler. One path is used for transmission, and the other path is used as a reference signal to generate a reconstructed signal with the same amplitude but opposite phase to the self-interference signal. Vector synthesis is then performed in the receiving channel to cancel out the self-interference and retain the pure tag reflection signal.
It significantly improves receiver sensitivity and effective communication distance, thereby enhancing the reliability of tag identification.
Smart Images
Figure CN121997958A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of radio frequency identification, and in particular to an RFID reader implementation method and system based on self-interference cancellation. Background Technology
[0002] Radio Frequency Identification (RFID) technology, as a non-contact automatic identification technology, has been widely used in many fields such as retail, logistics, asset management, and the Industrial Internet of Things (IIoT) due to its advantages of high efficiency, durability, and cost-effectiveness. Passive RFID systems are particularly favored because their tags do not require an internal power source and can be activated by the radio frequency energy emitted by the reader, achieving long lifespan and low maintenance costs. However, short communication distance remains a core bottleneck restricting further performance improvements of passive RFID systems.
[0003] In compact RFID reader designs, the transceiver-single-antenna architecture is widely used due to its small size and low cost. However, this architecture has an inherent drawback: strong transmitted signals can leak into the sensitive receiving channel through the antenna, circulator, and other paths, generating severe self-interference. This self-interference significantly reduces the receiver's signal-to-noise ratio, leading to a sharp deterioration in receiving sensitivity, thereby limiting the reader's effective communication distance and tag identification reliability. Traditional solutions, such as using high-isolation circulators or adding out-of-band filtering, have limited isolation and are difficult to meet the system requirements under high transmit power. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an RFID reader implementation method and system based on self-interference cancellation, which effectively suppresses strong self-interference signals leaking from the transmission channel to the receiving channel, thereby significantly improving receiving sensitivity, increasing effective communication distance and identification reliability.
[0005] The objective of this invention is achieved through the following technical solution: a method for implementing an RFID reader / writer based on self-interference cancellation, comprising the following steps:
[0006] Step S1: The RFID chip generates a radio frequency signal, which is split into two paths in the transmission channel by the first coupler. One path is transmitted to the antenna for transmission; the other path is coupled to the self-interference reconstruction module as a reference signal. At the same time, the reflected signal from the tag received by the antenna enters the receiving channel through the first coupler.
[0007] Step S2: Based on the reference signal coupled from the transmission channel, the self-interference reconstruction module performs precise amplitude and phase modulation to generate a self-interference reconstruction signal with the same amplitude but opposite phase as the self-interference signal.
[0008] Step S3: In the receiving channel, the self-interference reconstruction signal and the received signal are vector synthesized using the interference cancellation module, thereby effectively canceling the self-interference components, so that only the pure tag reflection signal is retained after cancellation processing.
[0009] Step S4: After cancellation processing, only the pure tag reflection signal is retained and coupled into two paths through the second coupler. One signal is transmitted back to the RFID chip, and the other signal is fed back through the feedback link.
[0010] Step S5: In the feedback link, the power of the residual self-interference signal is obtained by the detector and sent to the microcontroller, which then iteratively controls the self-interference reconstruction module.
[0011] An RFID reader / writer system based on self-interference cancellation includes: an RFID chip, a transmitting channel, an antenna, an interference reconstruction module, a receiving channel, and a feedback link;
[0012] The RFID chip is used to generate radio frequency signals and transmit them to the transmission channel;
[0013] The transmission channel includes a first coupler for splitting the radio frequency signal from the RFID chip into two paths: one path is transmitted to the antenna for transmission; the other path is coupled to the self-interference reconstruction module as a reference signal; at the same time, the reflected signal from the tag received by the antenna enters the receiving channel through the first coupler.
[0014] The self-interference reconstruction module, based on the reference signal coupled from the transmission channel, performs precise amplitude and phase modulation to generate a self-interference reconstruction signal with the same amplitude but opposite phase as the self-interference signal.
[0015] The receiving channel includes an interference cancellation module and a second coupler. The interference cancellation module uses the interference cancellation module to perform vector synthesis between the self-interference reconstruction signal and the received signal, thereby effectively canceling the self-interference components, so that only the pure tag reflection signal is retained after cancellation processing. The pure tag reflection signal retained after cancellation processing is coupled into two paths through the second coupler. One signal is transmitted back to the RFID chip, and the other signal enters the feedback link.
[0016] The feedback link includes a detector and a microcontroller. The detector obtains the power of the residual self-interference signal and sends it to the microcontroller, which then iteratively controls the self-interference reconstruction module.
[0017] The beneficial effects of this invention are as follows: This invention uses the coupled transmitted signal as a reference, and utilizes an adjustable attenuator and a phase shifting module to generate a cancellation signal with the same amplitude and opposite phase as the self-interference signal. This cancellation signal is then combined with the received signal containing interference in the receiving channel, thereby significantly canceling strong self-interference. This allows weak tag return signals to be effectively detected, ultimately greatly improving the effective communication distance and tag identification reliability of the system. Attached Figure Description
[0018] Figure 1 This is a flowchart of the method of the present invention;
[0019] Figure 2 This is a schematic diagram of the overall system link;
[0020] Figure 3 This is a schematic diagram illustrating the principle of interference reconstruction link;
[0021] Figure 4 This is a schematic diagram illustrating the principle of iterative control of the self-interference reconstruction module by a microcontroller. Detailed Implementation
[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.
[0023] like Figure 1 As shown, an RFID reader implementation method based on self-interference cancellation includes the following steps:
[0024] Step S1: The RFID chip generates a radio frequency signal, which is split into two paths in the transmission channel by the first coupler. One path is transmitted to the antenna for transmission; the other path is coupled to the self-interference reconstruction module as a reference signal. At the same time, the reflected signal from the tag received by the antenna enters the receiving channel through the first coupler.
[0025] Step S2: Based on the reference signal coupled from the transmission channel, the self-interference reconstruction module performs precise amplitude and phase modulation to generate a self-interference reconstruction signal with the same amplitude but opposite phase as the self-interference signal.
[0026] Step S3: In the receiving channel, the self-interference reconstruction signal and the received signal are vector synthesized using the interference cancellation module, thereby effectively canceling the self-interference components, so that only the pure tag reflection signal is retained after cancellation processing.
[0027] Step S4: After cancellation processing, only the pure tag reflection signal is retained and coupled into two paths through the second coupler. One signal is transmitted back to the RFID chip, and the other signal enters the feedback link.
[0028] Step S5: In the feedback link, the power of the residual self-interference signal is obtained by the detector and sent to the microcontroller, which then iteratively controls the self-interference reconstruction module.
[0029] like Figure 2 As shown, an RFID reader / writer system based on self-interference cancellation includes: an RFID chip, a transmitting channel, an antenna, an interference reconstruction module, a receiving channel, and a feedback link;
[0030] The RFID chip is used to generate radio frequency signals and transmit them to the transmission channel;
[0031] The transmission channel includes a first coupler for splitting the radio frequency signal from the RFID chip into two paths: one path is transmitted to the antenna for transmission; the other path is coupled to the self-interference reconstruction module as a reference signal; at the same time, the reflected signal from the tag received by the antenna enters the receiving channel through the first coupler.
[0032] The self-interference reconstruction module, based on the reference signal coupled from the transmission channel, performs precise amplitude and phase modulation to generate a self-interference reconstruction signal with the same amplitude but opposite phase as the self-interference signal.
[0033] The receiving channel includes an interference cancellation module and a second coupler. The interference cancellation module uses the interference cancellation module to perform vector synthesis between the self-interference reconstruction signal and the received signal, thereby effectively canceling the self-interference components, so that only the pure tag reflection signal is retained after cancellation processing. The pure tag reflection signal retained after cancellation processing is coupled into two paths through the second coupler. One signal is transmitted back to the RFID chip, and the other signal enters the feedback link.
[0034] The feedback link includes a detector and a microcontroller. The detector obtains the power of the residual self-interference signal and sends it to the microcontroller, which then iteratively controls the self-interference reconstruction module.
[0035] In this application, the radio frequency signal generated by the RFID chip in the transmission link is split into two paths by a first coupler: the main signal is transmitted to the antenna; the other path is coupled to the self-interference reconstruction module as a reference signal. Simultaneously, the weak reflected signal from the tag received by the antenna also enters the receiving channel (the first coupler is a four-port bidirectional coupler; the first port connects to the RFID chip, the second and third ports connect to the antenna and the self-interference reconstruction module, and the fourth port connects to the receiving channel. During signal transmission, the radio frequency signal is coupled to the antenna and the self-interference reconstruction module; during signal reception, the antenna-received signal is coupled to the receiving channel). To extract the effective signal, the system uses the reconstruction link and the reference signal coupled from the transmission channel, with precise amplitude and phase modulation by the self-interference reconstruction module, to generate a self-interference reconstruction signal with the same amplitude but opposite phase to the self-interference signal. This reconstruction signal is vector-synthesized with the received signal, effectively canceling the self-interference components, so that only the pure tag-reflected signal is retained after cancellation. This signal is then coupled through a second coupler and enters the feedback link. The detector in the feedback link sends the power of the residual self-interference signal to the microcontroller, which then completes the iteration and update of the cancellation algorithm. This significantly improves the receiving sensitivity and system performance without increasing the number of antennas, thereby increasing the effective communication distance of RFID.
[0036] like Figure 3 As shown, the self-interference reconstruction module is as follows: the input signal coupled from the transmit link is first evenly distributed to four parallel processing branches via a power divider. Each branch is connected in sequence to a digitally controlled attenuator and a phase delay unit. The phase delay units are transmission lines that generate fixed phase shifts of 90°, 180°, and 270°, and a straight path that serves as a phase reference. Each digitally controlled attenuator independently modulates the amplitude of the signal in its branch under the drive of the control unit, generating signal components with specific amplitude and phase characteristics. Finally, all branch signals are vector-synthesized by the output power divider to reconstruct a precise cancellation signal with the same amplitude and opposite phase as the original interference signal.
[0037] The system monitors the residual power signal after interference cancellation in real time using a detector and feeds it back to the microcontroller. The microcontroller's built-in simulated annealing algorithm analyzes the received power data and generates control commands to dynamically adjust the attenuation value of the digitally controlled attenuator. Through continuous iterative optimization, the system can find the optimal attenuation configuration that minimizes residual power and configure the optimal configuration.
[0038] The specific process is as follows: The system initializes and performs real-time power monitoring. When the residual power is detected to be greater than the power threshold, the simulated annealing optimization algorithm is started. This algorithm generates new attenuator parameter combinations (new solutions) through random perturbation and uses a detector to measure the corresponding power value. Strictly following the Metropolis criterion, it accepts inferior solutions with a certain probability, balancing global exploration and local development, while employing a multi-stage cooling strategy to gradually converge. Finally, when the power is lower than the threshold or the temperature drops to the limit, the optimal attenuation configuration is output and the system state is locked, achieving the goal of minimizing residual power. The specific process is as follows: Figure 4 As shown.
[0039] S501. First, by initializing the system, obtain the random attenuation values of the attenuators for the four channels. =[ , , , The attenuator has an attenuation range of 0-31.5dB, with a step size of 0.5dB.
[0040] S502. Apply a perturbation near the initial solution to obtain a new solution. A multi-level perturbation scheme is adopted:
[0041]
[0042] in, The basic perturbation is achieved by randomly selecting one of the four channels and adding a random step. The value range of the basic perturbation / random step is {-1, -0.5, 0, 0.5, 1}, and the unit is dB.
[0043] Let be a Bernoulli random variable, with probability The value is 1 (triggering this level of disturbance), otherwise it is 0. The value is generated randomly. This refers to an additional perturbation that is triggered with a certain probability. For the first Level of disturbance amplitude = And satisfy: when hour,
[0044] S503. For the new solution and the current solution Define the power difference:
[0045]
[0046] According to the Metropolis acceptance criterion of the simulated annealing algorithm, the acceptance probability is:
[0047]
[0048] in This is the current temperature parameter. It is the base of the natural logarithm;
[0049] If the new solution is better, i.e., has lower power, then the new solution is accepted directly, and the update is performed. = ;
[0050] If the new solution is worse, i.e., has higher power, then it is probabilistically... Accepting the new solution: Update after accepting the new solution. = When receiving new solutions The process remains unchanged; then, return to step S502 and repeat steps S502-S503.
[0051] S504. The temperature decreases with each new solution obtained:
[0052] The coefficient of performance is the cooling factor.
[0053] Until the temperature drops to the temperature threshold: Or the new solution reaches the power threshold. The annealing algorithm ends, and the optimal decay configuration is output. And lock in, to achieve the goal of minimizing residual power. This refers to the results obtained during the repeated execution of steps S502~S503. The minimum value.
[0054] The foregoing description illustrates and describes a preferred embodiment of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.
Claims
1. A method for implementing an RFID reader / writer based on self-interference cancellation, characterized in that: Includes the following steps: Step S1: The RFID chip generates a radio frequency signal, which is split into two paths in the transmission channel by the first coupler. One path is transmitted to the antenna for transmission; the other path is coupled to the self-interference reconstruction module as a reference signal. At the same time, the reflected signal from the tag received by the antenna enters the receiving channel through the first coupler. Step S2: Based on the reference signal coupled from the transmission channel, the self-interference reconstruction module performs precise amplitude and phase modulation to generate a self-interference reconstruction signal with the same amplitude but opposite phase as the self-interference signal. Step S3: In the receiving channel, the self-interference reconstruction signal and the received signal are vector synthesized using the interference cancellation module, thereby effectively canceling the self-interference components, so that only the pure tag reflection signal is retained after cancellation processing. Step S4: After cancellation processing, only the pure tag reflection signal is retained and coupled into two paths through the second coupler. One signal is transmitted back to the RFID chip, and the other signal enters the feedback link. Step S5: In the feedback link, the power of the residual self-interference signal is obtained by the detector and sent to the microcontroller, which then iteratively controls the self-interference reconstruction module.
2. The RFID reader implementation method based on self-interference cancellation according to claim 1, characterized in that: The self-interference reconstruction module includes a first power divider, four channels, and a second power divider; each channel includes a digitally controlled attenuator and a phase delay unit. The first power divider splits the reference signal into four paths, which are transmitted to four channels respectively. In each channel, the digitally controlled attenuator receives the data from the first power divider and performs independent amplitude adjustment. Each digitally controlled attenuator is connected to the second power divider through the phase delay unit in the channel. The second power divider is used as a combiner to perform vector synthesis on the received signal, thereby reconstructing a precise cancellation signal with the same amplitude and opposite phase as the original interference signal.
3. The RFID reader implementation method based on self-interference cancellation according to claim 2, characterized in that: The phase delay units in the four channels are respectively the direct path of the phase reference, the transmission line with a fixed phase shift of 90°, the transmission line with a fixed phase shift of 180°, and the transmission line with a fixed phase shift of 270°.
4. The RFID reader implementation method based on self-interference cancellation according to claim 3, characterized in that: In the feedback link, the power of the residual self-interference signal is obtained by the detector and sent to the microcontroller. The microcontroller then iteratively controls the self-interference reconstruction module, including: S501. Initialize and obtain the random attenuation values of the digitally controlled attenuators in the four channels. =[ , , , ], , , , These represent the attenuation values of the numerically controlled attenuator in the first to fourth channels, respectively. The attenuation range of the numerically controlled attenuator is 0-31.5dB, with a step size of 0.5dB. S502. In Applying a perturbation near the solution yields a new solution. A multi-level perturbation scheme is adopted: ； in, The basic disturbance has a value range of {-1, -0.5, 0, 0.5, 1}, and the unit is dB; set up Let be a Bernoulli random variable, which is a variable with probability... The variable takes a value of 1, which indicates that the disturbance at this level has been triggered; otherwise, it takes a value of 0. The value is generated randomly. To use random probability Additional disturbances triggered. For the first Level of disturbance amplitude = And satisfy: when hour, ; S503. For the new solution and the current solution Define the power difference: ； According to the Metropolis acceptance criterion of the simulated annealing algorithm, the acceptance probability is: ； in This is the current temperature parameter. It is the base of the natural logarithm; If the new solution is better, i.e., has lower power, then the new solution is accepted directly, and the update is performed. = ; If the new solution is worse, i.e., has higher power, then it is probabilistically... Accepting the new solution: Update after accepting the new solution. = When receiving new solutions The process remains unchanged; then, return to step S502 and repeat steps S502-S503. S504. The temperature decreases with each new solution obtained: The coefficient of performance is the cooling factor. Until the temperature drops to the temperature threshold: Or the new solution reaches the power threshold. The annealing algorithm ends, and the optimal decay configuration is output. And lock in, to achieve the goal of minimizing residual power. This refers to the results obtained during the repeated execution of steps S502~S503. The minimum value.
5. An RFID reader / writer implementation system based on self-interference cancellation, characterized in that: Includes: RFID chip, transmitting channel, antenna, interference reconstruction module, receiving channel, and feedback link; The RFID chip is used to generate radio frequency signals and transmit them to the transmission channel; The transmission channel includes a first coupler for splitting the radio frequency signal from the RFID chip into two paths: one path is transmitted to the antenna for transmission; the other path is coupled to the self-interference reconstruction module as a reference signal; at the same time, the reflected signal from the tag received by the antenna enters the receiving channel through the first coupler. The self-interference reconstruction module, based on the reference signal coupled from the transmission channel, performs precise amplitude and phase modulation to generate a self-interference reconstruction signal with the same amplitude but opposite phase as the self-interference signal. The receiving channel includes an interference cancellation module and a second coupler. The interference cancellation module uses the interference cancellation module to perform vector synthesis between the self-interference reconstruction signal and the received signal, thereby effectively canceling the self-interference components, so that only the pure tag reflection signal is retained after cancellation processing. The pure tag reflection signal retained after cancellation processing is coupled into two paths through the second coupler. One signal is transmitted back to the RFID chip, and the other signal enters the feedback link. The feedback link includes a detector and a microcontroller. The detector obtains the power of the residual self-interference signal and sends it to the microcontroller, which then iteratively controls the self-interference reconstruction module.