Design And Implementation Of Real Time Echo Simulator Based On FPGA

In a complete radar system research work, its performance test is a very important part. Traditional field tests cost a lot of manpower, material and financial resources,furthermore, in bad weather conditions, this test method could not even be achieved.These factors are very unfavorable to the development of radar system. The technology of radar echo simulation is used to replace the field test by simulating the target echo and noise signal in real environment, which greatly facilitates the research of radar system. Radar echo simulator has the characteristics of low cost, high flexibility and repeatability, and it greatly reduce the difficulty of radar system research. In the modern radar system research process, the radar echo simulator has become an indispensable part.This paper designs and implements a FPGA-based universal scalable low-cost radar echo simulator, and the study completed the following main work:1.The radar echo principle and the related echo simulation technology are studied,and the mathematical model of radar echo signal is established and analyzed in this paper. The analogies of the transmitter front end are compared, and the PLL frequency synthesis technology is analyzed. The influence of the IQ phase imbalance and the DC offset on the output signal is studied.2.A low cost, high availability and high flexibility low cost radar echo simulator based on FPGA is proposed. Simulator is divided into two modules, namely the baseband signal generator and RF signal transmitter. The baseband signal generator is used to generate two orthogonal echo signals in various conditions. The RF transmitter is used to orthogonally mix the baseband signal to the RF signal.3.The design of the baseband signal generator was completed. FPGA is mainly used to generate radar echo digital signals, including the target echo signal and noise signal. In addition, FPGA is also used to realize the DC orthogonal calibration of the baseband signal. Because the hardware circuit is purely in many deviations and unsatisfactory, it is relatively difficult to realize the DC orthogonal calibration on the analog circuit, so this paper adopts the digital calibration method. The final analog output of the baseband signal is implemented by the digital-to-analog conversion chip AD9752.4.The RF signal transmitter design was completed. The transmitter uses direct conversion quadrature modulation structure,the signal source part is based on ADL4351 chip design completed. The quadrature mixer is based on the ADL5375 chip design. And add a filter selection channel to the link to achieve the second harmonic suppression of the transmitter. The final signal is amplified by the ADL5610.5.The radar echo simulator test was completed.All the indexes meet the design requirements.