| 摘要 |
The invention relates to a diplex Doppler type radar system which can detect a preceding vehicle (202) even when the range rate (e.g. a relative velocity, a relative distance DL) of a preceding vehicle (202) relative to a vehicle (201) having the radar system is small. The Radar system is mounted on a vehicle (201), the transmit antenna (104) alternately transmits two signals on different frequencies. When the transmitted signals meet an object (a preceding vehicle 202) and reflected, the reflected signals are received by a receive antenna (106). Usually, the first A/D converter (112) digitizes IF signals (said received signals) and the DSP (digital signal processor) (113) frequency-analyzes the digitized signals to compute the range rate of the preceding vehicle (202). When a peak spectrum exists in a low frequency range below a preset threshold as the result of the frequency analysis, the IF signals are digitized by the second A/D converter (116) which has a higher sampling resolution than that of the first A/D converter (112). The digitized IF signals are frequency-analyzed by the system control microcomputer 115. Thus the range rate (e.g. a relative velocity and a relative distance DL between the preceding vehicle (202) and the following vehicle (201)) of the preceding vehicle (202) is computed. <IMAGE>
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