Design Of Vehicle Flow Monitoring RADAR Based On LFMCW

With the constant improvement of the living standard of citizens, the amount of vehicles witnesses a sharp increase in the city, which leads to a higher requirement for the traffic monitoring and management system. Under this circumstance, new development concepts such as “intelligent transport system(ITS)” and “smart city(SC)” have been put forward and become the future direction of some large-medium cities. So, the accurate and reliable vehicle flow monitoring equipment, an important part of ITS, will be well needed in the future. Thus, LFMCW RADAR, which has a high advantage of precision, reliability and maintenance, can be widely developed and used in vehicle flow monitoring.The aim of the designed LFMCW RADAR is monitoring 4-lane to 8-lane road's vehicle flow, which mainly consists of a triangle wave generating circuit, a continuous wave RADAR sensor, an IF signal processing circuit and a digital signal processing module.The triangle wave generating circuit is made up of MAX038 and its peripheral circuits. It produces a frequency-adjustable and relatively fixed-amplitude triangle wave, which is used to manipulate the VCO in the continuous wave RADAR sensor to transmit LFMCW signal to a certain area.The continuous wave RADAR sensor is the radio part of this design. It is used to transmit high-frequency LFMCW signal, mix it with vehicles' echoes, amplify the mixing result and then output the IF signal which includes the information of vehicle's distance.The IF signal processing circuit is an important foundation of this design, in order to make the vehicle flow monitoring come true. It consists of a high-pass filter, a low-pass filter and an IF amplifying circuit. Among this module, the high-pass filter is used to filter out triangle wave's leakage when it modulates the frequency of continuous wave and decrease the dynamic range of IF signal making use of its transitional zone; the low-pass filter to filter out out-of-band noise and high-frequency interference, so as to further improve the quality of IF signal; the IF amplifying circuit to magnify the weak filtered IF signal.The digital signal processing module is the core design of this vehicle flow monitoring RADAR. It consists of a hardware part which is made up of the FPGA chip EP2S90F1020, the DSP chip TMS320C6727 B as well as their peripheral circuits and an algorithm part based on them. The FPGA part of this module is used to fulfill ADC, time-domain background cancellation processing and then transmit the result to DSP. While, the DSP part is used to utilize the vehicle detection and statistics of the vehicle flow based on FFT, adaptive threshold detection and comb band-pass filtering.The result of the test indicates that the designed LFMCW RADAR is stable and reliable, which has the fundamental functions in order to realize the vehicle flow monitoring.