Broadband Impedance Measurement Technology Research

Impedance measurement plays an important role in the distributed parameter analysis of sensor, instrument and PCB(Printed Circuit Board).Various types of techniques and instruments(ac bridges, oscillators, time-domain techniques and amplitude-phase measurements)have been developed over many years. However, all these methods require the power source to be low distorted sinusoidal periodic wave, which restrict the expansion of measurement range and the improvement of accuracy because it's difficult to gain low distorted sinusoidal signal. The impedance measurement technique, with the rapid development of communication technology, more and more high frequency components, and the frequency is not fixed, and therefore requires the measurement of impedance measurement to a wider bandwidth.In this thesis, the broadband system for impedance measurement method is studied, and make the integrated use of the DSP, DDS technology. Measurement system bandwidth of 25Hz~2MHz. Introduced a wide range of impedance measurement method and implementation of the principle, set out the advantages of vector voltammetry and the use of vector basis voltammetry; given the overall design of broadband impedance analysis program; on the signal circuit and the signal detection circuit design; one signal circuit Direct Digital Synthesis (DDS) chip AD9858 to achieve, there are several options Sweep, Sweep range can be arbitrarily set, and meet the requirements of broadband. Microprocessor circuit to DSP as the core, control and coordination of the entire system in real-time measurements of data processing, DSP chip is used in TI's TMS320F2812, the chip of a higher price than can be both cost and performance to DSP for the control of the core, you can improve system capacity and data-processing speed. At the same time, such as providing flexible RS-485/232 interface circuit for the measuring instrument to provide a certain degree of scalability.