Ka-band System Radar Receiver Front-end

The millimeter-wave has been widely used in the areas such as radar, communications and guidance due to the characters of wide bandwidth, penetration and anti-interference. Millimeter Radar with high resolution and small size has been extensively used. Pulse Radar has precise measurement as to long-distance goals, but it has blind range; Continuous wave radar can achieve accurate measurement to close targets, however it has the disadvantage of leakage signal from transmission signal. The purpose of the research is to realize the receiver front-end which can measure the range and velocity of a target and works in pulse and continuous signal system at the frequency of Ka-band on the condition that the transmitter and receiver share the same antenna.Firstly, based on the discussion of the scheme of receiver in pulse and continuous wave radar system, the conculsion can be drawed the switchs are used to suppress the leakage signal from transmission signal in pulse system and taking the leakage signal from transmission signal as the local oscillator in continuous system. The front-end of the receiver is designed that can measure the range and velocity by the pulse, CW, LFMCW and m-sequence modulated BPSK signal. After the scheme is obtained in different system, the signals in differend system are produced from DDS controlled by FPGA.Secondly, after the characteristic of spur and spectrum of the DDS and the phase noise of PLL are analysised, the center frequency of120MHz single signal, the bandwidth of10MHz m sequence modulated BPSK signal and the bandwidth of18.75MHz triangle LFMCW signal can be acquired from DDS controlled by FPGA. In the range of signal bandwidth, the spur from DDS is lower than-72dBc, the spur of signal in X-band is lower than-70dBc and the phase noise of8.48GHz signal is better than-95dBc/Hz@10kHz. At the same time the spur lower-75dBc, phase noise is better than-104dBc/Hz@10kHz of the second LO(1.475GHz).Thirdly, the effect of loop circuit to stable time of AGC by simulation and a dynamic range of34dB AGC circuit are researched in the project. In order to solve the contradiction of the high sensitivity in pulse system and the leakage signal in continuous system, the IF chain circuits at different signal system can be achieved by switch changes channels. The gain in pulse system can achieve52dB and P1dB power level of output port is12dBm. Single-ended mixer is used to extract the difference signal in continous system.Finally, by system debugging and m-sequence signal processing, receiver front-end has been designed in the project works in different signal systems. The receiver sensitivity-78dBm, noise figure is5dB, and signal to noise ratio at output port is20dB.