The Design Of Low-Frequency Vector Network Analyzer

A design of low frequency, vector network analyzer is described in this paper, which is used for the measurement of the amplitude-frequency characteristic and phase-frequency characteristic of the linear, time-invariant, two port network. The device is mainly used to measure the signal of audio, automatic control system and vibration. The frequency range of the device is from 0.01Hz to 2MHz and the resolution of the phase measurement is better than 1o.The sweep-frequency measurement is used in this paper. Being in low frequency, reflection isn't taken into account .Sweep-frequency source, the measurement of the amplitude-frequency characteristic and phase-frequency characteristic, the system of control, display and keyboard are the basic part of low frequency, vector network analyzer. In this paper , AD9852,fiter,amplifier comprise a sweep-requency source.The phase,frquency and amplitude of the source can be adjusted and known through software . Compared with the traditional VCO and PLL, it is more accurate and easier to control. SOPC is used as the core of the system .I t meanings NIOS II processor and some other circuit are placed in a chip .It can simplify the system effectively. The LCD displays the amplitude-frequency chart and phase-frequency chart clearly and directly. The LCD and keyboard provide a friendly interface between user and the instrument.There are seven chapters in the paper. In the first chapter, the theory of the network analysis is illustrated. In the second chapter, the general principle of the project is introduced.After that chapter, the embedded system of Altera is discussed. The DDS technology and the application of DDS synthesizer to realize the signal source are given in the fouth chapter. In the fifth chapters, the method of the amplitude and phase measuring is introduced. The sixth chapter introduces the LCD display system and keyboard system. In the last chapter, the structure of system software and hardware is introduced.