| Due to its short wavelength,small size,wide frequency bandwidth,high measurement accuracy,and strong anti-interference ability,millimeter-wave radar is used in short-range,high-precision,high-resolution conditions and under the conditions of strict restrictions on system volume.It has been widely used in both military and civilian fields.In this paper,the short-range detection object is used as the detection target,and the Ka-band micro-miniature millimeter-wave ranging system is studied and designed.Based on the background of short-range ranging engineering,the key technologies of millimeter-wave radar front-end circuits,sub-harmonic mixers and difference frequency signal processing at home and abroad are compared and analyzed.According to the requirements of the millimeter-wave ranging system,the ranging principle of FMCW radar is analyzed,the key parameters of the system are determined,and the zero-IF receiver method is proposed as the receiver scheme of the ranging system.According to the requirements of the millimeter wave ranging system and the allocation of various indicators,the overall scheme design of the system is determined.According to the overall scheme of the system,the front-end circuit of the millimeter-wave ranging system is designed,and the key components of the system receiving components are designed,including the improved design of the sub-harmonic mixer to improve the port isolation and reduce the frequency conversion loss,and the millimeter-wave band pass.Filter design,step impedance low-pass filter design,phase-locked loop frequency source design with high stability and low noise amplifier,transmit branch and receive branch design.Complete the design of the front-end cavity of the entire system,and connect the frequency source,the transmitting branch and the receiving branch in the cavity.In the research of FMCW high-precision ranging algorithm,the key factors affecting ranging accuracy are analyzed,and several commonly used spectrum refinement methods arestudied.In this paper,two spectrum refinement algorithms,complex modulation Zoom-FFT and CZT,are proposed to improve the frequency resolution.Rate.Through the analysis and verification of the two algorithms,it is determined that the spectrum of the beat frequency signal is refined based on the complex modulation Zoom-FFT method to obtain accurate frequency values.The experimental test shows that when the transmitting frequency of the detection front end is 36?37GHz and the receiving sensitivity reaches-65 d Bm,the maximum distance of the target can reach 20 m.Effectively improve the ranging accuracy. |
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