Research On Thickness Measurement Technology Based On FMCW Radar

With the rapid development of microwave and millimeter wave solid-state devices and digital signal processors,the performance of FMCW(Frequency Modulated Continuous Wave)radar has been significantly improved,with smaller size and lighter weight.In recent years,FMCW radar has been increasingly widely used in various fields.In this thesis,the thickness measurement technology based on FMCW radar is studied,and a Cband FMCW radar front-end is designed and fabricated.The Chirp-Z transform(CZT)algorithm is applied to improve the thickness measurement accuracy.Finally,an FMCW radar thickness measurement experimental system with a center frequency of 5.8 GHz and a bandwidth of 1 GHz was built.The designed radar system is mainly divided into three parts: a sawtooth wave generation circuit module,a radio frequency transceiver module,and transceiver antenna.The radio frequency transceiver module includes a voltage controlled oscillator,a power amplifier,a power divider,a low noise amplifier,a mixer,and an intermediate frequency filter circuit.The experimental results show that in two different thickness measurement schemes,the measurement error of FFT reaches 2.95 cm and10cm,respectively,while using the CZT algorithm can reduce the error to 0.5cm and 1cm.It can be seen that combining the CZT algorithm can significantly improve the measurement accuracy of the FMCW radar system and reduce measurement errors.The main work of this thesis includes:1.Based on the principle of linear frequency modulated continuous wave,the principle of ranging and thickness measurement of FMCW radar,as well as the two key performance indicators of range resolution and thickness measurement accuracy are analyzed.2.Then,according to the usage scenario,the system scheme of the FMCW radar is designed,and the system indicators are determined.The determination of main technical parameters,selection of RF chips,design of sawtooth wave generation circuits,power distributors,filters,antennas,and other devices are completed.The overall circuit design and engineering of the RF transceiver module are carried out.A shielding shell is designed and fabricated for the RF transceiver module to prevent signal interference and protect the circuit.3.In order to improve measurement accuracy and reduce measurement errors,research on algorithms for improving measurement accuracy has been carried out.Theoretical analysis has been conducted on algorithms such as Fast Fourier Transform,Sampling Sequence Zeroing,Spectral Peak Estimation,and Chirp-Z Transform.The effectiveness of Spectral Peak Estimation and Chirp-Z Transform algorithms has been verified in experiments.4.Finally,an experimental prototype device and an experimental system were made and Experimental tests were conducted,including dielectric constant testing,distance testing,and thickness testing.The measurement results of direct FFT,spectral peak estimation,and CZT algorithm were compared.The results showed that compared to the direct FFT algorithm,spectral peak estimation can reduce measurement errors to a certain extent,while CZT algorithm can significantly reduce measurement errors.