Wavelet Denoising Method For RFID Signal

RFID, is a kind technique which can automatically identify and track the target without direct contact. Since the advent of this technology at 1990's, it has been adopted in identification and track of objects in production, storage, distribution, sales and other procedures due to its quickness, convenience, efficiency, reliability, less demands for distance, environments and other advantages. Though RFID technique has tended to be perfect and matured, there are still some questions that should be overcome in the actual adoption. The noise generated in the communication process of label and reader data is one of the crucial problems that should be solved urgently. In order to solve this problem, the received radio-frequency signal of the target should be firstly denoised.In recent years, in the related fields of signal denoising techniques, the wavelet denoising technique has attracted more and more attention in the field of signal processing. As a new signal denoising technique, it could observe and analyze the target signal from coarse to fine, thus has the feature of possessing multiresolution, as well as the ability to local partial feature of the signal in time and frequency domains. Since the radio-frequency signal is a kind of unstable signal, the wavelet denoising technique is particularly suitable for deniosing and isolating abnormal signals randomly to avoid the crucial problem of failure in acquiring signal caused by enlarging of signal entropy after the denoise. The wavelet denoising method is more efficient for the deniose of unstable signal, has the advantage of getting more useful signal, compared to the traditional Fourier filtering method.In order to test the denosing efficiency of wavelet denosing method, the author designed a virtual signal processing system based on LabVIEW, which contains the producing module of radio-frequency signal, signal and data acquisition module, coding module, modulation module, demodulation module and filter module of the signal data in order to facilitate the simulation analysis of the wavelet denosing method in this thesis, as well as the simulation analysis of other the research methods of new technique in the communication field.Meanwhile, this thesis has demonstrated the radio-frequency identification technology, as well as the wavelet transform theories related to the wavelet denosing method; has specially introduced the threshold denosing method of the wavelet denosing methods. It has adopted the designed LabVIEW virtual signal processing system to process the unstable signal which has already become the Gaussian white noise, respectively adopted two different threshold functions and four threshold select forms to conduct denoising processing simulation after the different combinations. Based on the result analysis of the signal after the denoise, it gets the conclusion that the adoption of wavelet denosing method in RFID system could effectively enhance the internal system performances.