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Research and Implementation of Automotive Millimeter-wave Collision Avoidance Radar

Author: ZhaoShuang
Tutor: ChenDianRen
School: Changchun University of Science and Technology
Course: Communication and Information System
Keywords: Millimeter-wave Target recognition Distance estimation
CLC: TN957.51
Type: PhD thesis
Year: 2013
Downloads: 14
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Abstract

With the development of society, the number of cars is increasing and the traffic accidents occur frequently. Automotive collision avoidance radar can detect whether the target exists in front of the car and measure the speed and the distance, thus reminds the driver to avoid traffic accidents. It has very broad application prospect. This paper mainly did research on the radar target recognition algorithms and the realization of the radar. The work of this paper epitomized in the following areas:the radar target recognition technology、 precision ranging correction algorithm、Millimeter-wave radar anti-jamming and the correction of the chirp source of high linearity and error. The paper made progress and innovation in the following areas:1、 For radar transmitted waveform, proposed the pulse segmented LFMCW as the radar transmitter waveform. When the radar uses the LFMCW waveform as the transmitted waveform, the upper and lower sweep band echo contain a short linear FM signal after the stretching process. When using FFT as a main process method of the echo signal, this part of the chirp signal and can not provide valid information. This causes the emission energy wasted in the chirp segment time. While using the pulse segmented LFMCW as the radar transmitted waveform, it can be guaranteed the echo signal does not contain the linear FM signal after the stretching treatment. It improves the SNR of the signal and the target distance estimation algorithm accuracy.2、In the target distance algorithm, by calculating the spectral amplitude difference of the upper and lower sweep band echo signal, corrected the target distance algorithm, which increased ranging precision. When plus zero to the simple point and use the side lobe suppression weighting algorithm as radar signal processing, multi-spectral lines will appear within the main lobe of the spectrum when using FFT process the data of the radar. It will cause the target fuzzy, unable to distinguish whether it is a target or multiple targets. To solve this problem, this paper used two-dimensional FFT calculate target Doppler shift. In the case of the known Doppler frequency shift, drawn a one-dimensional FFT spectrum amplitude difference normalized curve, and then normalized one-dimensional FFT spectrum amplitude difference of the target echo up and down sweep band. In the normalized difference curve, the corresponding correction frequency to correct the target spectrum has been funded. Though the correction algorithm, the multiple spectral lines of the main lobe could be corrected to one. At the same time, it improved the ranging accuracy.3、For the targets of similar distance but different speed,proposed use CZT transform extract the speed information of the target and the amplitude difference of the band spectrum.Then use the distance correction method to correct the target distance. When there are similar distance but different speed targets in front of the the radar, Their one-dimensional FFT spectrum overlap so can not normalize the one-dimensional FFT Spectral amplitude. However, due to the different speed of the target, the amplitude information of the respective target can be extracted by using CZT to process the results of the two-dimensional FFT. Then the distance of the target can be corrected by using amplitude spectrum difference normalized. So that the radar can identify different target with similar distance but different speed, and increases the distance measurement accuracy of the various target.4、For multiple radar work simultaneously interference problems, the the system hopping echo processing algorithms combined with low sidelobe microstrip antenna have been proposed. The work environment of the automotive collision avoidance radar is complex, it often encounters multiple radar work at the same time. Using system hopping, each radar has a different transmitter frequency. Through analyzing the upper and lower sweep band of the radar and the interference signal, pairing of upper and lower sweep band target, allows the radar to be able to distinguish between the front of the target and the interference signal. In the millimeter wave automotive anti-collision radar antenna, the paper designed microstrip array antenna. Used the weighted algorithm combined with the zero constraints to reduce the antenna sidelobes. Then reduce the interference caused by the possible directions.5、Broadband chirp source systems based on DDS technology have been researched. By analysis system error model, proposed according to the DDS phase truncation digit to select chirp step and according to Chirp frequency agility speed to select the A/D sampling speed of the receiver. Reduces the system error caused by the discontinuous phase truncation and linear FM.

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