A Study On The Collection Technology Of Traffic Information Based On MMICs

The collection of traffic information, acts as an input to the intelligent transportation systems (ITS), takes on an very important task for providing the whole ITS with accurate information sources. Investment on ITS around the world are huge.In China, 11 cities, such as Beijing, had progressed the pilot program on ITS during the past "10^th Five-Year Plan" period, and it will be the emphasis generalization period for the ITS achievements during the "11^th Five-Year Plan" period of China. The needs for traffic information collection will be huge. So it's very important and is of great significance to study the traffic information collection technology, and to make this technology become a real apparatus for traffic information detection applications.Regarding to those mentioned above, a new technology for traffic information collection has been studied here in this paper, and this new technology is based on the microwave radar technology, which is grounded on MMICs (Microwave monolithic ICs). With this technology, a new kind of traffic information collection apparatus called MPR (MicroPu Radar) has been successfully achieved. This product had been judged by the related authority and now it's in the period of the middle test before massive produce.Generally speaking, the traffic information collection technologies can be divided into three categories: Wave(microwave, supersonic, infrared),coil and video. Each has its own advantages and disadvantages, and as a whole, the traffic information collection technology based on microwave technology is of the most prosperous future. First of all, this technology has overcome such problems caused by the installation as difficult to install and to maintain, traffic needs to be interrupted and the roads need to be destroyed for installation and maintenance, expensive for maintenance and short life time; Secondly, it will not be influenced by the atrocious weather and illumination conditions; and the last but not the least, it can detect several lanes simultaneously with a relatively low cost. Of course, as mentioned above, it has its own shortcomings, it can only give the average velocity for vehicles, and it can not detect the vehicle type accurately.The main research works performed by the author are as follows: systematic design for the traffic information detection system and in charge of its implementation; organization of the develop of the sample apparatus and its outside tests; design and test for MMIC VCO and MMIC mixer; research on the process technology for the intermediate frequency signals; arithmetic study for radar signal process; proposal of the next generation traffic information collection technology.The innovations and the key technologies solved by the author during this research are as follows: 1) Applied the micro radar technology to the traffic information detection, and based on this technology, a new kind of traffic information detection sample apparatus has been achieved. This kind of detection technology is new and unique in China at present time. According to the test results, this technology is of international advanced level;2) Designed and fabricated (using the 0.25um GaAs PHEMT process abroad) successfully the first time in China the MMIC VCO and MMIC mixer, and these MMICs have been used in the traffic information collection apparatus. Several key technologies have been solved during the design, for example, greatly decreased the chip size of MMIC VCO and increased its tuning range, solved the process compatible problem for MMIC mixer, and decreased the microstrip gap for Lange coupler;3) A band-path filter with high positive slope and high gain has been designed by cascading multiple band-path filters, and this filter has very sharp raising edge and fall edge; the influence of radar signal process caused by the DC source ripple has been overcome;4) A set of arithmetic model for the radar system has been put forward, and by means of this model, such key problems as zero-signal, processing for traffic jam situation and the influence of near by lanes have been solved successfully;5) Grounding on the review of present time traffic information collection technologies, a new idea for the next generation traffic information detection technology has been proposed, which is based on a dual-beam microwave radar technology, the technological way to realize it and its feasibility have been put forward.MPR, the achievements of this research, can detect the presence of the vehicle accurately, but it can't accurately measure the vehicle velocity and its length, and further more, the sensitivity for detection can't be adjusted automatically. Now, the improvements for these shortcomings are being carried out, but the author think that the ultimate way will be the next generation technology—the dual-microwave beam radar technology.