Research On Broadband Digital Radio Frequency Memory System

Digital Radio Frequency Memory (DRFM) realizes the radar echo signals simulation bybroadband sampling, real-time storage, processing and reconstruction of the received radar signal.The simulation of the target echo signals of radar systems by DRFM has the advantage of goodcoherency, high accuracy and easily control. DRFM is the key component of the Radio FrequencySimulation System (RFSS). DRFM can also produce a variety of clutter and deception jammingsignal, which makes it also widely used in the field of electronic countermeasures. With the rapiddevelopment of modern communications and radar technology, especially the needs proposed bythe development of broadband radar system, the development of broadband DRFM has becomeimperative.In this thesis, a broadband DRFM is designed based on a certain national defense project,which is a target, clutter and deception-jamming simulator of a coherent radar system. Therealization of the high-speed circuit of broadband DRFM is studied for the project’s specifictechnical requirements. An implementation based on high capacity FPGA, high sampling ADCand DAC devices is given. Based on the top-bottom approach, the hardware is designed andimplemented from the top-level architecture to the bottom-level circuit. This paper analyzes thekey modules of the design and gives the physical circuit. The high-speed printed circuit board isdesigned and implemented in this paper. The signal integrity of the key modules in the hardware issimulated and analyzed.An implementation of digital automatic gain control system based on FPGA is given. Thealgorithm and the method of software and hardware design are described in detail. Simulation andexperimental results show that this AGC module has the features of short response time, highregulation accuracy and flexible parameter control.The hardware of the DRFM system is debugged and detailed analysis of the performance ofthe broadband ADC and DAC module is given. The principle of the generation of the spurioussignal is studied and the possible ways of reducing the spurious signal are proposed. Animplementation of the target, clutter and deception-jamming simulator of a coherent radar systemis given, and some of the measured waveform as well. Test result shows that this broadbandDRFM system has the advantages of an instantaneous bandwidth of500MHz and a spurious levelof better than-50dBc.