Research On Key Technologies Of W-band FMCW Radar Transceiver Front-End

The transceiver front-end in the FMCW radar system can realize the functions of baseband signal frequency conversion transmitting and receiving signal mixing to produce IF signal.Its performance determines the quality of the whole radar system.The W-band is one of the four atmospheric window frequencies.The transceiver module working in this band has a small size and high range resolution,which has very important research value.Based on the characteristics of the millimeter wave,the application background and the working principle of the FMCW radar,this paper uses the hybrid integration technology to design the W-band FMCW radar transceiver front-end system.The front-end of this subject includes the local oscillator,receiving and transmitting functions.The transmitting branch and the local oscillator branch are homologous,the dual-channel receiving branch uses an image rejection mixer;in order to improve the integration,the 90-degree bridge of the receiving branch is placed on the back of the lower cavity,and the I/Q signal of the mixer in the front of the lower cavity is connected with the bridge through the vertical transition of the glass insulator,the DC board is placed on the back of the lower cavity.Considering that the heat dissipation of the transmitting branch power amplifier is large,the thermal simulation software FloTHERM is used to simulate the temperature to verify the heat dissipation performance of the component.Finally,the entire transceiver system is integrated into a single cavity,which improves the integration degree.The size of the entire transceiver front end is 115 mm(length)*56 mm(widest)*21 mm(thickness).According to the system design requirements,the W-band Wilkinson power divider and the W-band waveguide-microstrip probe are designed by HFSS,and the modules were tested separately.The experimental results show that the passive structure has good performance,The insertion loss of Wilkinson power splitter is about 1dB,and the insertion loss of probe is about 0.7dB,which can be used in transceiver front-end systems.The performance of power amplifier,low noise amplifier and other important chips is verified by individual module test.After completing the design and experiment of the key unit structure of the transceiver front end,assemble and debug the whole system of the transceiver unit.The experimental results show that the output power of the transmitting branch is greater than 29.2dBm and the highest is 30.1dBm in the working frequency required by the design.The output frequency of the IF is 50-90 MHz.The gain of both receiving branches is greater than 23.7dB.The maximum gain of branch 1 is 25.43 dB,the maximum gain of receiving branch 2 is 28.45 dB.The noise figure is up to 5.01 dB.The image rejection is better than 25.94 dB,which meets the design requirements.The W-band FMCW radar transceiver front-end developed in this paper has the characteristics of high integration and large output power,which can be used in the whole FMCW radar system.