Research On The Secondary Cm-Wave Automotive Anticollision Radar

Focused on the realization in engineering practice, this paper discussed automotive anticollision radar's function requirement, working principle and system design. Through summarizing and analysis of its research and development, the paper proposes a new type of secondary centimeter wave automotive anticollision radar that applied on the expressway.Carrier frequency and modulation scheme are two key issues in the system design of automotive anticollision radar. Popular automotive anticollision radar is required to measure the velocity and angle of its targets as well as range. Therefore, the short-wavelength high-resolution millimeter wave is used, measuring range and velocity through FMCW scheme, measuring angle through multi-beam scanning. However, this type of radar demands complex technologies and components of excellent performance, hence difficult to realize in applications. Considering that: (1) radar can achieve its basic application of collision avoidance and warning with the only function of ranging; (2) under high speed conditions, radar should have lager effective range than that under slow speed, we designed a new easily realizable automotive anticollision radar, which employs centimeter wave and square pulse amplitude modulation. To compensate centimeter wave's shorting comings such as broad beam and short effective range, a transponder is added in the back of target automotive. This secondary radar measures range in the way of transponding.The ranging performance of radar is based on its performance of echo detection. Detecting echo in the background of noise is a probability problem. There are two ways to enhance the radar's detection performance: (1) for certain signal to noise ratio, choose a optimum detection threshold, whose false decisions producing minimum cost under the preset cost rules; (2) basically reduce the false decision probability by increasing echo's SNR. This paper deduces the optimum threshold expression under certain cost rule and relationship between the number of pulse accumulation and the increased ratio of echo's SNR. The according pulse accumulation method is designed and realized, i.e. digitalizing the echo and synchronously accumulating them in RAM.With the illustrations of many block diagrams, circuit schematics and waveformfigures, this paper expatiates the system architecture, working principle and working flow of the revised secondary Cm-wave automotive anticollision radar. The whole system is divided into three parts according to the signal frequency, i.e., RF channel, IF modulation and demodulation, digital terminal. Part 1 discusses system design and parameter selection. Part 2 puts forward the circuits of pulse and IF carrier generation and square pulse amplitude modulation and demodulation. The final part brings the circuits of digitalization, pulse accumulation, range calculation and decoding of range display. All the circuits in digital terminal module are designed in FPGA.