The Research Of RF Cancellaion Technology In A SFCW Radar System

According to the waveform of the radar when it works, the radar can be divided into: pulse radar(PR) and continuous wave radar(CW). Comparing the CW radar system with the pulse radar system, the CW radar system has lower transmitting power, higher resolution and lower peak power.These features make the CW radar system hard to be detected. However, a serious shortcoming of the continuous wave radar is the signal leakage. The direct coupling signal from the transmitter to the receiver is much bigger than the echo signal of the target. According to radar equation when the target need to be detected in the distance, the transmission power of the radar will need to be increased, then the echo signal of the target is likely to be submerged by the direct coupling signal and even the receiver may be burned down. This is a inevitable question of continuous wave radar. The work of this paper is to study the working principle of CW radar and RF cancellation system and develop a RF cancellation system for a step frequency continuous radar(SFCW).The paper mainly includes the following aspects.Firstly, the working principle of CW radar and pulse radar are analyzed. The direct coupling signal is the reason for constraining the performance of CW radar. In order to solve this problem, the RF cancellation is proposed.Secondly, the ideal conditions to cancel the direct coupling are analyzed. And the error analysis has been completed.Next, the CW radar and RF cancellation system has been designed. Depending on the indicators of the system, the suitable chips has been selected to draw the layout of the system.Finally, after debugging the modules of the system, the whole RF cancellation system will be measured. Then analyze the test data.According to the test data, when the frequency is a point the cancel ratio is beyond 40 dB.And when the frequency sweep the cancel ratio can get 30 dB in 400 MHz band.