FPGA based Miller subcarrier decoding method of ultrahigh frequency RFID reader-writer
A decoding method and reader technology are applied in the field of Miller sub-carrier decoding of UHF RFID readers to achieve the effect of avoiding accumulated errors
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Embodiment 1
[0055] Embodiment 1 of the present invention provides a Miller subcarrier decoding method for an UHF RFID reader based on FPGA. The RFID reader includes the following circuit components: digital baseband, transmission link, reception link, antenna radio frequency Front end and digital interface, where the transmission link is to modulate the coded signal output by the digital baseband into a UHF radio signal and amplify it through a power amplifier and send it to the RF front end of the antenna, and the receiving link is to receive the modulated signal returned from the tag by the RF front end of the antenna Demodulate the baseband signal and send it to the digital baseband for decoding and other digital signal processing. Since the baseband signal of the digital baseband is easily disturbed by the surrounding environment during transmission, the waveform of the signal will be distorted in the propagation path, resulting in missing data and symbol signals, etc. Problem, the dec...
Embodiment 2
[0074] Embodiment 2 of the present invention further provides a Miller subcarrier decoding method based on FPGA on the basis of Embodiment 1, and the decoding method also includes the following methods:
[0075] S5, code element logic judgment: analyze the correctness of code element logic by the echo sequence collected, as: " 1111111111 " is the collection data of Miller subcarrier half BLF period (such as image 3 As shown), in order to improve the ability of anti-signal jitter and anti-noise, the possible noise interference is filtered out when analyzing the actual collected data. The specific method is as follows:
[0076] S5-1. First, analyze the echo sequence collected in half the BLF cycle, and determine whether there is a mutation in the echo sequence;
[0077] S5-2. If it exists, count the duration T of the mutation bit and the number of mutations. If the duration T≤preset time or the number of mutations≤the preset number, it is judged as noise interference. At this t...
Embodiment 3
[0089] Embodiment 2 of the present invention further provides a Miller subcarrier decoding method based on FPGA on the basis of Embodiment 1, and the decoding method also includes the following methods:
[0090] S10, data analysis, similar to preamble data analysis, the specific method is: detect the received echo sequence, when the signal jump edge is detected, restart the square wave sampling signal with frequency F of 20*BLF, and start at the same time The level timer performs timing value W detection. When the next signal jump edge is detected, whether the timing value W of the detection timer satisfies the following formula,
[0091] Timing value W=(1 / 2*BLF)*80%,
[0092] If it is satisfied, stop the timing and reset the timer, judge whether the timing value meets the requirements, and restart the square wave sampling signal with a frequency F of 20*BLF for subsequent symbol sampling, and the cached echo The sampling data of the symbols in the sequence is judged by noise...
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