Research On Low-Spurious And Wide-Band Digital Radio Frequency Memory System

Digital Radio Frequency Memory(DRFM) is the key component of the Radio Frequency Simulation System(RFSS), which has the advantages of good coherence, high accuracy and controllability for the simulation of target echo. With the rapid development of new radar technology, especially the needs proposed by the development of ultra wideband radar system and agile frequency radar, the development of wideband DRFM has become imperative.Firstly, the factors that produce spurious in the wideband DRFM system are analyzed, and the modeling and simulation are performed in this thesis. According to the main parameters of DRFM system, the factors affecting the performance of the system, such as quantization error, multi-channel alternating sampling mismatch error, sampling clock spurious, wideband reconstruction SINC fading, and their affecting degree are analyzed and verified by simulation. On this basis, the effective method to improve system spurious performance is proposed.Secondly, according to the requirement analysis, the performance requirement of wideband DRFM system are proposed, and then the design and implementation of the hardware platform is presented. An implementation based on high capacity FPGA, high sampling ADC and DAC devices is given. Then the key issues and implementation of each module are analyzed, and the high-speed printed circuit board is completed.Thirdly, according to the above research method of improving the spurious performance of the system, a low spurious clock generation system is designed. The design and implementation of the hardware circuit and software algorithm are completed and the experimental verification is given. The experimental results show that the spurious/ harmonic suppression of the clock generator is better than 60 dBc, which can meet the needs of the DRFM system.Finally, the thesis carries on the experiment about the wideband DRFM performance and analyzes the testing results. Test result shows that this wideband DRFM system has the advantages of an instantaneous bandwidth of 1GHz and a spurious level of better than-50 dBc when the sampling rate is 2.5GHz. After the digital predistortion calibration, the amplitude fluctuation is less than ±1.5dB, which achieves the expected results.