Domestic research and development of ultra-high frequency automatic recognition technology lags behind international standards by 2-3 years. Although a number of patented technologies have been developed, the quantity is relatively small. The core technologies of ultra-high frequency RFID mainly include anti-collision algorithms, low-power chip design, UHF electronic tag antenna design, testing and certification, etc.

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Let's briefly introduce the patented technologies related to ultra-high frequency RFID below!

In terms of low-power chip design

In April 2008, Peking University Shenzhen Graduate School applied for a Chinese invention patent, which disclosed a demodulation circuit for ultra-high frequency radio frequency identification chips, including an envelope detection circuit and an envelope shaping circuit. The RF signal received by the antenna is sequentially processed into S signal and Sav signal by the envelope detection circuit and envelope shaping circuit, and then output to the comparator.

The envelope shaping circuit includes a leakage resistor, a diode, a filtering resistor, and a filtering capacitor. Among them, the leakage resistor is connected between the signal output terminal of the envelope detection circuit and the ground; The anode of the diode is connected to the signal output terminal of the envelope detection circuit; The cathode is connected to one end of a parallel branch consisting of a filtering resistor and a filtering capacitor, and the other end of the parallel branch is grounded.

The signal output terminal of the envelope detection circuit is the S signal output terminal, and the connection point of the parallel branch composed of the diode cathode, filter resistor, and filter capacitor is the Sav signal output terminal. This invention achieves the coexistence of low power consumption and low cost in the demodulation circuit of ultra-high frequency radio frequency identification chips.

Anti Collision Algorithm

1. In February 2007, Shenzhen Contemporary Communication Technology Co., Ltd. applied for a Chinese invention patent involving a multi tag anti-collision algorithm in an ultra-high frequency long-distance automatic recognition system. This algorithm dynamically adjusts the Q value based on the collision of data returned by labels, and includes the following steps:

a、 The preset Q value is 0-15;

b、 The reader/writer sends the Querying command and receives tag returns;

c、 The reader/writer sends a query reply command of 2 Q-power units;

d、 After steps a, b, and c, if the collision count is 0, the label reading process ends; If the collision count is not 0, determine the Q value of the next Query command based on the collision count, and repeat steps a, b, and c.

The dynamic Q value is determined by the following method:

a、 Estimate the quantity of labels;

b、 Based on the estimated number of labels and the calculation of the power and exponent of probabilities, calculate the new Q value by taking the exponent with a base of 2.

This invention can achieve seamless and complete reading of multiple tags in ultra-high frequency long-distance automatic recognition systems, and has high reading efficiency.

2. In December 2007, Fudan University applied for a Chinese invention patent and disclosed a random anti-collision algorithm that combines Bit Slot and ID Slot.

Firstly, the tag randomly selects a slot to provide a 1-bit confirmation instruction. The return information of all tags forms a bit string of length L. After eliminating empty slots, the reader/writer sends L-C0 QueryRep instructions. The tag provides its ID code in the slot corresponding to the slot counter, and the reader/writer determines whether a collision occurs based on the received ID code; The reader recognizes the tag and counts the number of collision time slots and successful time slots; If the tags have not been fully recognized, the reader/writer will continue to recognize the tags in the next frame until all tags have been recognized.

This invention adopts the Bit plot method to reduce the time overhead of empty time slots, and uses shorter QueryRep instructions instead of longer "unique 1 code" confirmation instructions in Bit Plot, which can effectively improve the speed of multi tag recognition.

3. In August 2003, Shanghai Fudan Microelectronics Co., Ltd. applied for a Chinese invention patent and disclosed a collision resistant identification method for a high-frequency radio frequency identification system, which includes a reader and at least one responder. Its characteristic is to establish wireless communication between the reader and the responder using a specific form of wireless signal, which consists of a logical signal part and a time slot part. The logical signal part is used to transmit various commands or information from the reader to the responder, while the time slot part is used for the responder to perform backscatter modulation and transmit a binary response signal to the reader.

Based on wireless communication, the reader sends corresponding commands or information to the responder, causing the responder to make corresponding transitions between initial state, general query state, general search state, waiting state, and confirmation state, and execute the search and query actions of the reader corresponding to the responder, thereby completing the recognition of the reader corresponding to the responder.

This invention solves the synchronization problem of previous binary search methods and improves their anti-interference performance.

4. In December 2008, Shanghai Fudan Microelectronics Co., Ltd. applied for a Chinese invention patent and disclosed a multi tag anti-collision algorithm. The algorithm includes: zeroing; The reader/writer sends a label query command; The responder judges the received query command; The reader/writer receives tag query responses and makes judgments; The reader/writer performs data processing on the responder; Set the PD value to 1 and Q value to Q; the reader/writer sends a query change command while the responder responds; The reader/writer receives tag query responses and makes judgments.

The reader/writer performs data processing on the responder. This algorithm can quickly eliminate conflicting tags and has high practical recognition efficiency. It can quickly reduce the number of responders within the working range of the reader/writer. On the one hand, it can improve recognition efficiency by rapidly reducing the number of responders, and on the other hand, it can reduce the interference of the reader/writer in the electromagnetic environment to further improve recognition quality.

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In terms of testing and certification

In October 2008, Shanghai Juxing Instrument Co., Ltd. applied for a Chinese utility model patent involving a radio frequency identification comprehensive testing instrument with real-time response function. It consists of a controller, intermediate frequency, baseband processor, RF up converter, and RF down converter. The output terminal of the controller is connected to the input terminal of the intermediate frequency and baseband processors, and the output terminal of the intermediate frequency and baseband processors is connected to the input terminal of the RF up converter. The output terminal of the RF up converter outputs a signal, the input terminal of the RF down converter is connected to the return signal of the tested equipment, and the output terminal of the RF down converter is connected to the input terminal of the intermediate frequency and baseband processors.

This testing instrument is mainly used for protocol consistency testing and performance testing of card readers and tags. The RFID protocol is implemented through software, and a modular instrument is used to integrate a testing system specifically designed for RFID testing. At the same time, the second generation ultra-high frequency RFID standard microsecond level real-time response is achieved using an intermediate frequency and baseband processor onboard FPGA.

Design of UHF electronic tag antenna

1. In July 2007, Beijing University of Posts and Telecommunications applied for a Chinese invention patent, involving the design of a tag antenna with capacitive and inductive coupling, consisting of a dielectric substrate and an antenna unit set on the dielectric substrate.

The antenna unit includes:

a. The first component is the main body of the antenna unit, which includes a first conductor and a second conductor, composed of straight or bent lines, used to control the operating frequency;

b. The second component provides good capacitive coupling for the first component and achieves adjustable antenna capacitance values within a certain range;

c. The third component is located in the closed space formed by the second conductor of the first component and the second component. Based on its shape, area, and relative position in the closed space, it provides good inductive coupling for the first component and achieves adjustable antenna inductance values within a certain range.

This tag antenna can achieve impedance matching with different tag chips through simple adjustment, while ensuring sufficient bandwidth within the operating frequency range.

2. In August 2008, Zhejiang University applied for a Chinese invention patent and disclosed a dual band anti metal ultra-high frequency RFID tag antenna. It includes a metal ground, a metal radiation surface, a substrate, a rectangular groove, a first feed line, a second feed line, a via, an RFID chip, and a U-shaped slot. The substrate is rectangular. The metal radiation surface is located on the upper surface of the substrate, and the metal ground is located on the lower surface of the substrate. A rectangular groove is embedded on one side of the metal radiation surface near the short side, with a first feeding line and a second feeding line in the middle of the rectangular groove. A radio frequency identification chip is placed between one end of the first feeding line and one end of the second feeding line, and the other end of the first feeding line is connected to the metal radiation surface. The second feeding line has a via hole, with the upper end of the via hole connected to the second feeding line and the lower end of the via hole connected to the metal ground. A pair of U-shaped slots are embedded on both sides of the metal radiation surface near.

The RFID anti metal tag produced by this antenna can simultaneously cover two frequency bands of China's ultra-high frequency RFID or two frequency bands of North America and Europe's ultra-high frequency RFID.

3. In November 2008, Aerospace Information Co., Ltd. applied for a Chinese utility model patent and disclosed a broadband RFID ultra-high frequency antenna, which includes a near-field antenna and a far-field antenna combined together. Among them, the near-field antenna is an induction coil, and the far-field antenna is a dipole antenna. The antenna is etched on an aluminum coated polyester PET substrate. Meanwhile, the utility model also provides a radio frequency tag using the above-mentioned antenna.

The working distance range of the antenna of this utility model includes near-field or far-field range, and its working frequency range can cover the entire RFID UHF frequency band, thus having wide adaptability. At the same time, the impedance value is very stable within the frequency band, and it has good omnidirectional performance in the xz direction within the operating frequency band.

4. In September 2005, Samsung Techwin Co., Ltd. disclosed a UHF RFID tag and its production method in a Chinese invention patent application.

The tag includes a substrate, a chip attached to the substrate and having multiple solder pads for connecting circuits formed within the chip to external circuits, and at least one UHF antenna extending longitudinally and responding to ultra-high frequency electromagnetic fields transmitted from the outside.

At least one end of the UHF antenna is connected to a solder block and a portion of the antenna is fixed to the substrate. Because the UHF RFID tag uses multiple short UHF antennas instead of circular antennas, it can integrate as many tags as needed due to its small size, and the process of combining antennas onto chips can be quickly and easily implemented.

Ultra high frequency RFID technology has the characteristics of being able to read multiple tags at once, having strong penetration, being able to read and write multiple times, having a large memory capacity for data, low cost, small size, easy use, high reliability and lifespan of passive electronic tags. We believe that it will develop better in the future, thus expanding the application fields of ultra-high frequency RFID.