Design Of Phase Difference Detecting System Based On Spectrum Analysis

Phase difference detecting is the key technology of Hydrocephalus detection based on PSSMI(phase shift spectroscopy of magnetic inductio n), and the digital phase difference detecting technology has the characteristics of high accuracy and strong real-time. The thesis studies simulation and DSP implementation of two digital phase difference detecting algorithms based on spectrum analysis(FFT method and all phase FFT method).Based on demonstration and contrast of two phase difference detecting algorithms, the thesis verifies that all phase FFT(ap FFT) method has greater spectral leakage suppression capability than FFT method and has “phase invariance”. By MATLAB simulation, The thesis obtains that windowed ap FFT method can achieve higher accuracy of the phase difference detecting. The thesis combines the phase difference detecting theory based on spectrum analysis and DSP technology, and designs a complete program of phase difference detecting system which is based on dual DSP+FPGA. The system hardware includes correction module, pre-processing module, dual-channel ADC module, FPGA module, control module, algorithm module, human-computer interaction module, etc. The system software includes FPGA software, control system software and algorithm module software.The thesis by means of the design tool CCES tests the overall functionality and performance of the system. The results show that the system is stable and the accuracy of phase difference detecting reaches 0.005 ?, to meet the design requirements.