| Radar is often used for object detection.With the development of modern science and technology,people began to hope that radar can not only detect the location information of target objects,but also have further expectations which can obtain information about the target itself,including shape,size and so on.This requirement is difficult for narrow-band radar systems with low resolution.If wanted to obtain more accurate target information,the radar must have more accurate resolution capabilities,so it is determined that the radar must be developed in the direction of broadband.The most obvious advantage of ultra wide-band radar is high range resolution.Its echo signals can cover multiple targets in different positions.At the same time,this tadar also has good anti-jamming and anti-clutter performance.Therefore,the paper designs an ultra wide-band FMCW radar ranging system that works in the C-band.The radar system consists of three parts:ultra wide-band transceiver link,ultra wide-band antenna array and signal acquisition and processing module.In the transmitter part,the transmission signal generated by the frequency source based on the ultra wide-band voltage controlled oscillator chip,is sent to the antenna through the ultra wide-band transceiver isolation device for radiation after power amplification.The echo signal reflected by the target is also transmitted to the receiverbased on the ultra wide-band low noise amplifier and mixer chip through the antenna,and finally the base-band signal containing the position information of the target object is obtained.Through the analysis and calculation of each level of performance indicators in the hardware system,the selection of specific chips in all circuit modules was completed.These sub-module circuits were processed and tested.The test results were basically consistent with the preset performance parameters.Then each of the sub-circuits are laid out according to a reasonable structure,and a DC charging power 'supply circuit that can supply power to all active modules in the system is integrated into a whole PCB board and the real object is performed.The integrated board can cooperate with DSO2250U signal collector to sample and acquire the base-band signal and use MATLAB program to extract the distance information of the target.In order to further improve the performance of the system,the paper also designed an ultra wide stop-band low-pass filter and a broadband high-gain antenna.The ultra wide stop-band low-pass filter that based on the step impedance structure,the low-impedance line part uses a fan-shaped structure to improve the problem of the parasitic pass-band generated by the micro-strip filter due to the periodicity.The end incorporates two quarter-wavelength open circuit stubs to improve the problems of stop-band suppression and output matching.The measured results show that the pass-band 3 dB cutoff frequency is 2 GHz,the return loss in the pass-band is greater than 20 dB,and the stop-band suppression in the 3-20 GHz band reaches more than 25 dB.The filter is loaded on the intermediate frequency signal output of the receiver mixer which can effectively filter out the clutter interference in the base-band signal and leaked LO signal,which ensure that the hardware system can finally output a pure base-band signal.In order to meet the ultra wide-band high-gain index requirements of the antenna in the radar system,a 16-element printed wide dipole antenna array is designed in the paper,which is connected through a muti-section parallel strip-line unequal power division feed network.The designed antenna has a return loss greater than 10 dB in the 4.5?6.5 GHz frequency range of the system,and a gain of more than 15 dB. |
PDF Full Text Request