The Design And Implementation Of FMCW Level Radar Experiment Platform Based On DSP

The traditional pressure sensor is simple and easy to use, but its precision is low. Ultrasonic distance measurement has the advantages of simple, low cost, but due to air attenuation, echo signal amplitude fluctuation is large, which can cause larger error. Laser distance measuring has the advantage of high accuracy, but is easy to be impacted by the environment. Microwave liquid level measurement is non-contact measurement, can be used in a harsh environment. The FMCW radar has a high accuracy, high resolution and it is the most commonly used liquid level measurement now.The focus of this thesis is the design of FMCW level radar experimental platform hardware system. The system mainly includes:power supply module, filter module, amplifier module, A/D transformation module, memory module, digital signal processing module and the DSP and FMCW radar interface control part. The power module provides several power sources of different voltages for the system. Four IC chips and voltage divider circuit are used to achieve the desired voltages. Three parallel filters are designed so that the parameters can adjusted to test different cut-off frequencies of the measurement accuracy. The A/D accuracy directly restricts the entire system and the final calculation precision, so it needs extremely accurate sampling frequency. The system used DSP internal timer to control the sampling frequency. The FMCW radar interface control part is relatively complex. The system uses DSP s MCBSP interface to connect to FMCW module s SPI interface, and then to control FMCW radars data format and transmitting frequency. For data transmission, a wireless transmission mode is designed. The designed circuit is tested, so that we can adjust the system parameters. The precision requirement is achieved. The system accuracy can be achieved 1mm, which meets the established requirements.This thesis also introduces the FMCW radar ranging principle, according to the height of the liquid level and the difference frequency signal frequency relationship, using FFT can get the difference frequency signal frequency. But the accuracy achieved in this way can not meet the requirement. This thesis uses an improved FFT transform method. Using the improved algorithm the frequency error can be less than 0.5Hz, which is consistent with the experimental requirements.