The Design Of FMCW Level Radar Experiment Platform Communication And Control Unit

High accuracy liquid level measurement plays an important role in the field of oil transportation and chemical industry storage. Some traditional methods of liquid level measurements are no longer satisfying the enterprise production and transportation. The hydrostatic and capacitive systems are simple and cheap, but the measurement is difficult to achieve high accuracy. Laser system can achieve high accuracy but it is easy to be affected by environment. Microwave level sensor system is a very good way to measure liquid level and can be applied to all kinds of complicated environment. The FMCW (Frequency Modulated Continuous Wave) radar system is the preferred way of liquid level measurement, owing to its high accuracy and high range-resolution.This thesis describes the principles of the FMCW level radar, the relationship of the distance of the radar and the liquid level and the difference frequency signal frequency. The differential frequency signal spectrum can be calculated by FFT transform. And the frequency of the differential frequency signal can be calculated accurately by the maximum spectral estimation algorithm. Then the hardware system of FMCW level radar is introduced, including filter and amplifier module, A/D conversion module, storage module, digital signal processing modules, logic control module and serial port module. High-accuracy measuring algorithm for radar differential frequency signal and DSP’s program are also introduced. When doing research on the existing experimental platform, the control operations for DSP can only be done by emulator and the CCS software, which can not control the signal sweep frequency bandwidth and cycle flexibly, and the difference frequency signal data sampled by DSP can not be observed. In addition, the differential frequency signal and noise can not be separated well by the existing experimental platform, which affecting the experimental results. Therefore the serial module is designed in this thesis to make the DSP module communicate with the computer. Moreover, serial communication software can be written on computer to control DSP and realize the graphical display of the difference frequency signal on the PC. By further analysis of difference frequency signal, a more suitable hardware filter is designed.Finally, by welding and debugging of the designed circuit board, the existing system is modified to make all hardware modules work properly. Meanwhile the radar sweep frequency bandwidth and the display of the differential frequency signal can be controlled by the serial port software on computer.