FMCW Level Radar System Control And Echo Signal Processing Circuit Design

In the field of oil transportation and chemical industry, liquid level measurement has become an important part of the ship crude oil and chemical raw materials. Level measurements obtain the height of liquid level in real time and accurately and thus play an important role in the integrated control process.The hydrostatic and capacitive systems are simple and cheap, but the measurement is affected by the physical properties of the media in the tank and is difficult to achieve high accuracy. Laser systems have strict environmental requirement. Laser, ultrasonic beam and microwave are used in non contacting level measuring systems. So microwave level sensor systems can be used with hard measuring conditions such as high temperature, high pressure or aggressive media. The FMCW (frequency-modulated continuous wave) radar system, owing to its features of low transmitting power, high range-resolution and small size, is suitable for level systems.This thesis describes the FMCW radar ranging principles of level measurement. The level information depends on frequency of the radar beat-note signal, however it can't meet accuracy by useing FFT (Fast Fourier Transform) spectrum transform directly. The thesis uses the algorithm of FFT combined with CZT (Chirp-Z Transform). First FFT is used to transform radar beat-note signal and find the range of spectrum peak Then the scope of frequency is subdivided in order to get radar beat-note signal accurately. The thesis also designs the signal processing system, since FMCW radar transmitter power is small, the beat-note signal first needs amplification and then A/D converter, and finally uses DSP (Digital Signal Processor) to transform the spectrum using TMS320C5416 as the main processor and using CPLD (Complex Programmable Logic Device) to control the external circuits. This thesis describes various moduls of the system, designs the software system, and analyses the experiment results.