Research On Integrated RF Front-End For LFM Phased Array Radar And Communication System

With the development of radar technology, radar is more and more widely used in various fields. The requirement of the radar is not only confined to the target detection, but also the subtle characteristics of the target. Wideband phased array radar combines the advantages of wideband radar and phased array radar, can meet many requirements include the flexible beam control and great interference rejection ability and high resolution ratio. At the same time, the similarity of radar technology and wireless communication technology makes it possible for the integration of radar and communication system.The topic of this paper is the integrated RF front-end of wideband LFM phased array radar and communication system. According to the application background of this topic and comparison of the common transmitter and receiver scheme, we choose the zero IF structure in this paper, the frequency is 2.2-2.7GHz, and the bandwidth is 500MHz. We determined the system indicators according to the application background, then select a reasonable design scheme and make a link simulation of the transceiver, after these, we select the appropriate device according to the allocation index. Then, we finished the hardware design of the key modules of the transceiver, including the quadrature modulation module, quadrature demodulation module, low noise amplifier module, power amplifier module, 3dB directional coupler and so on.Finally, the performance of the T/R front-end is tested respectively. For the transmitting chain, its maximum output power is about 17dbm, the gain flatness is about 1.2dB within the bandwidth of 500 MHz; the phase of RF output signal is controlled by the baseband input signal, and when baseband signal is set to constant weights, the phase of RF output signal changes within 3 degrees; when the baseband signal is set to dynamic weights, the direction of beam scanning won't change with the change of frequency, and when the beam scanning point to 0 degrees, the side lobe level is about-14dB, when the angle of the beam scanning is within 30 degrees, the side lobe level maintained below-10dB, this; when the system input is 20Msps 16QAM modulation signal and the output power is lOdBm, the EVM of tansmitter is 2.8763%. For the receive chain, the amplitude imbalance degree of IQ baseband output signal is less than 0.3dB, the phase imbalance is less than 2.4 degrees; the overall noise figure of receiver is about 5dB; when the RF input signal is 20Msps,16QAM modulation signal, the EVM of receiver is 1.681%. The above test results show that the integrated transceiver front-end not only can realize beam forming, but also satisfy the basic needs of communication system.