In FMCW based radar system which is often adopted in vehicle collision avoidance radar system (VCARS), there are many factors which can affect the detection accuracy including hardware implementation method and signal processing algorithms. It is mainly discussed the effects of waveform design on system errors, especially the effects of the symmetry of triangle waveform. And the theoretical analysis with the experimental results was given. In the end, we offered two methods to reduce system errors. In the 24GHz VCARS developed by us, VCO is modulated by triangle waveform. The system errors are greatly determined by the parameters of the triangle waveform. Apart from the frequency of triangle wave, the band width of modulation, and the band width of intermediate frequency, we find that the detection accuracy of range and speed is also greatly affected by the symmetry of triangle waveform. So, the triangle waveform should be designed in consideration of its frequency, amplitude, offset, and strict symmetry. It is presented the theoretical analysis. When doing experiments with the VCARS, the parameters of triangle waveform are regulated including its frequency, amplitude, offset and symmetry. From the experimental results, it can be seen that it consistent with the theoretical analysis. In order to reduce such kind of system errors, there exist some methods. Two methods are discussed and the calibration results are given. These two methods are: (1) the application of direct digital synthesizer (DDS); (2) system calibration. With the former one, digital modulating wave is generated. Because digital wave can be easily regulated and the triangle waveform can be much more symmetrical than that generated by analog circuit, we can effectively reduce the system error due to the unsymmetrical triangle. The latter one is one easier method. That is to calibrate the entire radar system to reduce the system errors as a whole. There are five parts in this paper. In the first one, we briefly introduced the principle of FMCW and discussed the potential system errors in our VCARS due to hardware implementation method; in the second one, we theoretically analyzed the effects of triangle modulating wave on system errors; in the third one, we did experiments through regulating the parameters of triangle waveform and gave the experimental results; in the fourth one, we offered two methods to reduce such kind of system errors; in the fifth one, the paper is summarized.
Effects of waveform on the system errors of FMCW-based vehicle collision avoidance radar system
Einfluss der Wellenform auf den Systemfehler des FM-Dauerstrich-Kollisionsschutzradar auf Fahrzeugen
2004
4 Seiten, 9 Bilder, 2 Quellen
Conference paper
English
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