Most of the current designs of intermediate frequency (IF) circuit in traffic radar systems use the same-gain amplifier circuit to amplify the frequency signal, which leads to the same dynamic range of both the input and output intermediate frequency signals. Limited by the back-end signal processing ability, the dynamic range of detected intermediate frequency input signal is smaller, leading to a smaller detection distance. Then only four lanes can be monitored by the traffic radar simultaneously because of this limit in detection distance. Aiming at this issue, this paper puts forward a positive slope gain amplifier circuit to magnify intermediate frequency signal, which can effectively reduce the output signal dynamic range of the intermediate frequency circuit and facilitate the signal processing. This makes the dynamic range of the detected intermediate frequency input signal greater than before. So the detection distance is improved and the traffic radar has the ability to test eight lanes simultaneously. Test results show that the proposed positive slope gain amplifier circuit is effective.%在目前车流量雷达的中频电路设计中,基本上是采用同增益放大电路来放大中频信号,导致中频输出信号和中频输入信号的动态范围相同.由于受限于后端的信号处理能力,所以能够检测到的中频输入信号的动态范围较小,探测距离有限,使得车流量雷达通常只能同时检测4车道.针对该问题,提出采用正斜率增益放大电路来放大中频信号,可有效地减小中频电路输出信号的动态范围,便于后端的信号处理,能够检测的中频输入信号的动态范围也就比以前更大,从而有效提高了探测距离,使得车流量雷达能够同时检测8车道.实测结果证明了所提正斜率增益放大电路的有效性.
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