A novel method for measuring body bioimpedance and its FPGA implementation

Abstract

One of the most promising methods for assessing human tissue and diagnosing diseases is to measure the bioimpedance of the body. They have been various methods presented for achieving this goal. The most important point is measuring the phase along with the amplitude. On this basis, a field-programmable gate array (FPGA) is used in this study to measure the accuracy in amplitude and phase. At the first, a frequency spectrum is applied to the body model, then an algorithm in the VHDL compiler determines the amplitude of the output voltage. The phase change is measured by using direct digital measurement (DDM), and the product displayed in degrees or radian units. Subsequently, an FPGA model of the body has been simulated by using a lookup table (LUT) and various dependent circuits. FPGA-based hardware implementation is conducted by using Xilinx ISE 14.7 software, in which the chip selected for implementation is xc7z0203clg484. In this regard, the phase has detected. It's using an XOR gate, which consumes less power and hardware compared to flip-flop detectors. This novel phase measurement technique eliminates that needs for an exact adjustment of the clock, which increases measurement accuracy and reduces error. In the analysis of simulation results and theoretical values, the amount of the error has been calculated and plotted. As a result, the advantages of this method include being highly accurate, requiring little hardware, being flexible when changing the circuit, and consuming very little power.