Design Of Ka Band Radar Altimeter

Radar altimeter is an electronic device used to measure the relative height between the aircraft carrier and the ground.It is an essential airborne device for many aircraft.Linear frequency modulation continuous wave(LFMCW)radar altimeter has a series of advantages,such as strong anti-jamming,no range blind area,low transmission power,light weight and small volume.As the application scenarios of radar altimeter become more and more complex,people put forward higher requirements for the performance of radar altimeter.This thesis focuses on the modeling and simulation analysis of the altimeter signal processing method,and designs and implements a complete set of digital signal processing prototype with FPGA as the core.Finally,the relevant performance of the radar altimeter is verified through the UAV hang flight experiment.This thesis describes the working principle of LFMCW radar altimeter,completes the modeling and simulation of ground echo under sawtooth wave modulation,applies twodimensional FFT algorithm and unilateral CFAR detection method to the digital signal processing of the radar altimeter,and uses filtering to smooth the altitude measurement results of aircraft,and achieves ideal altitude measurement results.In terms of system implementation,the domestic Ka band radar front-end chip and the PLL chip ADF4158 with high linearity slope characteristics are used in the radar front-end.On the premise of high sampling rate of the system,in order to make the system have higher ranging accuracy and better real-time performance when flying near the ground,the radar altimeter combines with the front end of the radar to make the system transmit linear FM signals with small modulation period and large modulation bandwidth by changing the transmission waveform.In the remote altimeter mode,the transmission waveform with larger modulation period and smaller modulation bandwidth is used.Therefore,a digital signal processing scheme of radar altimeter based on constant modulation period operating system of far and near altimeter modes is designed,and a complete digital baseband processing scheme is realized with only one FPGA chip.The core of the hardware system of this design is the FPGA chip Zynq-7020 of Xilinx.Compared with classic FPGA,Zynq-7020 is based on So C architecture and can be divided into processor PS and programmable resource PL.It is especially suitable for software and hardware co design.In this thesis,the design and implementation methods of each module are introduced in detail,and the resource occupation and running time of each module are analyzed in detail.The digital signal processing scheme of the radar altimeter is completed within the limited FPGA resources,and the design requirements are met.