Research On Passive Dual-polarization Radar Tag

With the rapid increase of the vehicle in cities, the building of the effective traffic monitoring system and the automatic management system for traffic signal control have become a very important task in modern urban infrastructure construction. At present, the detection solutions of this field mainly based on the circular coil sensor, video surveillance and RFID. Facing the city traffic and environment of the actual situation, the system above has many disadvantages such as all-weather, real-time, reliability, accuracy, stability, economy, easy implementation of all aspects of existence or deficiencies. On the base of the depth analysis, this paper showed that the combination of the vehicle's radar target system with the traffic control radar system in cities was an effective solution. The radar target of the vehicles should not affect the appearance of vehicles, also with maintenance-free, easy to use, ect. This paper adopted the tabbed radar target to meet the above requirements.The radar target was a special radar reflector that could reflect a specific frequency range of radar single significantly. It could show in radar system for far outweigh the physical size of the RCS. The detecting capabilities of radar to the small object adopting the radar reflector could be significantly improved. The existing forms of radar reflector were suffered from the limitations of their configuration so that they could not installed on the small vehicle, while RFID could not satisfy the demand of long-distance traffic detection. Based on the drawbacks above, this paper presented a radar reflector in type of tag. This radar reflector had a small volume, no mechanical fixation and no influence on the appearance of the equipment, which was fit for vehicle in cities.Facing the complex urban traffic environment, we discussed a variety of weather factors on the degree of attenuation of electromagnetic waves of different frequency bands, based on that we determined the design frequency of radar target in this paper is 2.4GHz of the S-band. Radar scattering properties attributed the ability to reflect the radar waves of radar target. Radar cross section determines the radar detection range of targets, and polarization scattering characteristics of the radar target determines recognition ability. Based on the introduction of the target material, shape of the reflection properties of electromagnetic waves, L-shaped resonator had taken to be used as basic unit in the array to improve the radar cross section and cross-polarization scattering characteristics.According to different objects of electric size, we must choose the appropriate algorithm to achieve fast and accurate calculation of its radar scattering. By analyzing, we made clear the use of moment method to study the scattering characteristics of radar targets in the resonant zone. At the same time, the hybrid method was selected in order to study the scattering characteristics of complex systems including the electrically large targets and the electrically small targets effectively and accurately. Then on the base of scattering principle of radar targets, the integral equation of the scattering field of L-shaped resonator was given. Based on those above, the surface current distribution of the L-shaped resonator with external electromagnetic wave was discussed in the three-dimensional electromagnetic simulation platform Feko. Then the study of how to strengthen the cross-polarization scattering cross section using the current distribution in same direction was also carried out. The comparison of two arrays in different arranged was carried out and then the array with narrow lobe width as the final radar label array which could improve the resolution of radar. Finally, the joint simulation was carried out with the optimized radar label placed on the actual size vehicles.The results of this study showed that the adopting of the radar label could improve the ability of the radar detection to the vehicles placed in the complex environment in a convenient way. The radar label could also provide a sufficiently large, uniform and reliable RCS and the radar scattering properties spotlight on the target itself and the background, so as to achieve the purpose of target detection and identification. On the basis, the intelligent traffic control system of cities and the vehicle route guidance system could be developed.