Study And Design On RF Front For S-band FMCW Radar

In recent years,due to uncontrollable factors such as ecological imbalances caused by human factors or geographical structure and natural environment,landslides have been caused by collapses and falling rocks,resulting in significant losses to people’s lives and property.Therefore,monitoring the surface micro deformation of mountain slopes has become a hot research topic both domestically and internationally.Addressing the issues of large size,poor penetrating power and low range resolution of traditional SAR,the design and implementation method of the RF frontend of S band FMCW radar was proposed in this paper,which builds a basis for further study of the ground-based radar.Firstly,a theoretical analysis and overall design of the principle of frequency modulated continuous wave radar were presented.On the basis of analyzing the advantages and disadvantages of several different frequency synthesis methods,a frequency synthesis scheme using DDS+PLL+up-conversion technology was determined.STM32 was used to configure AD9910 direct frequency synthesis module and ADF4351 phase-locked loop module.The generated signal was finally generated by the ADL5801 mixer chip to generate a S band frequency-modulated continuous wave signal with center frequency of 2.8GHz and bandwidth of 200 MHz.By comparing and analyzing the advantages and disadvantages of zero intermediate frequency and superheterodyne,the basis of selecting zero intermediate frequency receivers in this paper was provided.On this basis,the overall system block diagram and performance indicators of RF frontend of S band FMCW radar were determined,and the gain and output power of each module in the system were allocated reasonably.Secondly,according to the indicators requirement of each module in the radar RF front-end,chip selection and program design were carried out for MCU,DDS,and PLL modules.ADS software was used for circuit design and simulation analysis of Class F power amplifier and low noise amplifier.The circuit design and simulation optimization of bandpass filter and microstrip Yagi antenna were carried out by HFSS software.Finally,the circuit diagram drawing and PCB production of each module were completed,as well as the testing and result analysis of five modules including Wilkinson power divider.Finally,the RF front-end of the designed S-band FMCW radar was tested experimentally,including the output power and flatness of the transmitting branch,the maximum receiving gain,sensitivity and dynamic range of the receiving branch,and the ranging performance of the system was tested.The experimental results indicate that the designed system can meet the requirements of the proposed indicators.