Design Of Hardware Platform For Multi-channel Dual-frequency New System High-frequency Over-the-horizon Radar Receiver

High-frequency radio can interact with the ocean surface to generate Bragg diffraction.Based on this feature,the high-frequency ground wave radar can not only realize the monitoring of dynamic state of ocean surface,but also also has the advantage of long distance,anti-low-altitude penetration and anti-stealth.However,the traditional single-waveform high-frequency ground wave radar is difficult to achieve near-distance and simultaneous detection of fast and slow targets,can not fully take advantages of high-frequency ground wave radar.Based on this situation,this paper mainly discusses the design and development of a new multi-channel dual-frequency high-frequency ground wave radar receiver hardware platform,which can simultaneously implement the emission of DDMA-LFM and DDMA-FMICW waveform system signals and the multi-channel echo signal reception,which can detect the long-distance high-speed moving target in real time,and also consider the short-range low-speed target detection and the ocean state monitoring.The main research work includes the following aspects:(1)Determine the system waveform design and echo demodulation scheme.The DDMA-LFM waveform is used to realize real-time detection of high-speed moving targets at long distances,and the corresponding echo signal demodulation scheme is pulse compression method based on matched filtering;the DDMA-FMICW waveform is used to detect low-speed targets at close distances,and the corresponding echo signal demodulation scheme is de-slope method.And determine the main waveform parameters of the two waveform systems according to the radar system detection indicators.(2)The signal synthesis module and the echo signal demodulation module of the two waveform systems are completed based on FPGA.According to the system echo demodulation design scheme,orthogonal mixing and digital down conversion are used to obtain target distance information for DDMA-FMICW echo signals;and orthogonal mixing,digital down conversion,and matched filtering are required to obtain target distance information for DDMA-LFM echo signals.Considering the resources,performance and ease of implementation,introducing the design and implementation of the digital down conversion module and the matched filter module in detail.(3)By simulating the actual echo,the digital transmitting signals of two systems with fixed delay are directly input into the demodulation module of the echo signal to realize the functional simulation of the closed-loop Modelsim in the FPGA,so as to verify the feasibility of the hardware design of each module in the FPGA.On this basis,completing the board-level closed-loop simulation,measuring and evaluating the quality of transmitted signal and the performance of receiver analog front-end.The test results show that the radar receiver can demodulate the 8-channel dual-system echo signal and obtain the target distance information,which further verifies the correctness of the system design.