The Processing Of RFID Signal Based On Wavelet Transform

Automatic identification of RF signal modulation is of great significance to achieve the RFID receiver, which is an important aspect of RF signal processing. Only by correctly identifying the communication signal modulation type, can be more focused on the signal demodulator and handling.Using wavelet transform to extract digital signal modulation characteristics is an effective method of identification. Because wavelet transform has good localizing time and frequency characteristics,and multi-resolution performance,it is an effective technique for extracting the transient characteristics from different digital modulation signals with out any prior knowledge. The wavelet transformations of three kinds of different digital communication signals are deduced theoretically,and the modulation identifier is constructed based on these results.Problems in identification of the RFID modulation type (2ASK,2FSP,2PSK) are discussed in this paper,and wavelet algorithm using in automation identification of communication signal modulation is studied.The characters of the digital signal in different modulation types in wavelet transform domain are extracted,and a trapezoidal sorter is designed.The characters in the wavelet domain being used as main identification parametres, automatic identification model of the digital signal modulation type using wavelet algorithm is established. The relationships among SNR gain,carrier frequency,sampling rate and wavelet zoom scale after wavelet transform in signal feature extraction are deeply researched, the optimization of sampling rate and wavelet zoom scale is proposed;and the noise impact is reduced.Massive simulations have confirmed good performance of this algorithm.The correct identification rate of most digital signal has all achieved above 90% when SNR>5db,which satisfies the request of this project well.The modulation parameters of digital signal are also estimated with the wavelet in this paper.The application of continuous morlet wavelet transform is studied,a method of estimate the carrier frequency and symbol cycle of 2FSK&2PSK by using wavelet ridge theory is proposed.In order to extract the signal character and identify the modulation type more correctly,the author has proved some related equations of the algorithm.