A 14443 interface pcd frame end detection method
A technology for interface and frame detection, applied in receiver monitoring, digital transmission systems, electrical components, etc., can solve the problems of small useful signal modulation amplitude, low communication efficiency, and difficulty in correctly distinguishing useful signals and noises
Active Publication Date: 2015-08-19
BEIJING CEC HUADA ELECTRONIC DESIGN CO LTD
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Problems solved by technology
Due to the existence of noise, the digital decoding circuit will mishandle in the frame end detection and other links. After the end of the frame, the noise signal is misjudged as a useful signal, or the signal is misjudged as the end of the frame during signal transmission, which leads to this time. Communication error, lower communication efficiency
This problem is particularly prominent when the working distance is long. The modulation amplitude of the useful signal is small, and the signal-to-noise ratio is reduced. The amplitude of the useful signal and noise is comparable. It is difficult to correct the threshold level of the quantization circuit through demodulation, filtering or adjustment. Distinguish between useful signals and noise, a large number of noise signals enter the digital decoding circuit
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[0013] The present invention will be described in detail below in conjunction with the accompanying drawings.
[0014] figure 2 The end-of-frame detection flow chart shows the processing flow chart of the present invention for misjudging the end of a frame caused by a noise signal. According to a specific implementation, it includes the following steps:
[0015] Step 201: Filter out noise spikes in the signal whose width is smaller than the protocol requirement. Considering that the signal width of the useful signal will change to a certain extent after demodulation, the set filtering threshold needs to have a certain margin.
[0016] Step 202 , judging whether the filtered signal width is greater than a corresponding threshold, if not greater than the corresponding threshold, proceed to step 203 , otherwise perform step 206 . Similarly, considering that the signal width of the useful signal will change to a certain extent after being demodulated, a certain margin needs to b...
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The invention discloses a method for processing an end of frame detection error caused by a noise signal in a PCD end physical layer with a 14443 interface. A 14443 carrier signal is sent to a digital decoding circuit for processing after being received, demodulated, amplified and quantized via radio frequency; and the noise signal is quantized after the amplitude of the amplified noise signal exceeds a threshold level of a quantizing circuit. In order to prevent the misjudgment of end of frame error caused by the noise signal, the time spent on detecting and judging the end of frame is increased by adopting a manner of character template; consequently, the probability of correctly detecting the end of frame is improved, the error of misjudging the noise signal as a useful signal after the frame end is avoided; the communication efficiency of the interface is improved.
Description
Technical field: [0001] The invention relates to a detection technology for the end of the received signal frame at the PCD end of the 14443 interface. Background technique: [0002] In the field of non-contact smart cards, the communication system is divided into two parts: the reader (PCD) and the card (PICC). Noise and interference will inevitably be introduced into the physical layer signals transmitted by radio frequency modulation at the PICC end and propagated through the air channel. When these signals are demodulated, amplified, and quantized by the RF end at the PCD end, noise will be introduced into the digital decoding circuit. Due to the existence of noise, the digital decoding circuit will mishandle in the frame end detection and other links. After the end of the frame, the noise signal is misjudged as a useful signal, or the signal is misjudged as the end of the frame during signal transmission, which leads to this time. Communication error, communication eff...
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IPC IPC(8): H04L12/26H04B17/20
Inventor 高慧尹晓杰胡毅
Owner BEIJING CEC HUADA ELECTRONIC DESIGN CO LTD