Research On A FPGA Based Impedance Measurement Module And Denoising By Wavelet

It has been confirmed that the bioelectrical impedance of normal tissue andtumor has obvious difference, which providing basis for distinguishing tumor fromnormal tissue. To improve the accuracy and precision of identification andmeasurement, a FPGA based dual channels measurement module has been designed,and the characteristic curves have been denoised using wavelet transform to highlightthe features. The main work of the paper is as follows:1. FPGA program of the dual channels measurement module is written byVerilog, which can output mixing frequency digit sequence. The quadraturedemodulation is completed by the MAC IP core, and the method to reduce the error ofdemodulation has been found by researching the relation of accumulated points,sampling frequency and testing frequency. The feasibility of software has been provenby modelsim.2. Hardware of the FPGA measurement module with dual acquisition channels isdesigned according to measurement requirements. The program can be downloadedthrough JTAG. Fouctions the module can realize are measuring using two channels,adjusting signals using programmable amplifier, ouputing frequency mixingexcitation, USB communication, etc.3. Accuracy of demodulating sinusoid and mixing frequency excitation and alsothe performance of USB are checked through the software test. The linearity of theexcitation is calculated after hardware test. The degree of accuracy is obtained bymeasuring several resistors and capacitor based on virtual reference point method, andthe repeatability is also be proven.4. The bioelectrical impedance of fat, gland, and breast cancer is measured andfrequency-resistance curves are drawn by Agilent4294A and optimized probe underdifferent frequencies. The curves are denoised using wavelet transforming, whichhighlights the features and makes it easy to extract characteristic parameters.