|
Signal source is electronic equipment, particularly an essential part of the test equipment, which produces a variety of reference signals to the device under test, to analyze and study the performance of the device under test conditions, are widely used in aerospace equipment, electronic test, measurement, and research and other fields. The current source waveform mainly price and kind and the contradiction between accuracy. Digitize the signal source, software has become the current trend. In this paper, a research institute of China Electronics Technology Group's satellites supporting the test project, based on the idea of ??developing a software radio universal versatile, low-cost source platform. The platform can achieve FM, BFSK, BPSK, QPSK, OQPSK, and MSK modulation etc.. Meanwhile, by analyzing the non-linear power amplifier and local oscillator phase noise and error vector magnitude (EVM) relationships obtained EVM and third-order intermodulation interference and phase noise of the mathematical model, the signal source transmitter performance made a systematic analysis. The main contents of this paper and work: a study of the hardware implementation of the principle of modulation, shaping filter, interpolation filters, direct digital frequency synthesizer principle and its FPGA implementation. 2, on the shaping filter roll-off factor, sample rate, length and truncated quantization bits of the system MATLAB simulation and selected according to project needs proper parameters. Carried out for each modulation MATLAB / SIMULINK modeling and simulation, further validate the realization of the principle and its hardware implementation is correct. 3, in the QUARTUSII environment, using VHDL hardware description language for the signal source and the modulation mode key module programming. By timing simulation verify the correctness and stability. 4, the use of software to make the signal source PROTEL99 PCB circuit board diagram. Chip selection according to project requirements, structural design, layout system board, and debugging. Download the program to produce the hardware platform, the hardware environment to test the modulation index, the EVM can be maintained at less than 1%, by comparing the signal generator Agilent E443B type modulation waveform generated by similar, indicating that the source system design The signal generator reaches the target. 5, the system analyzes the signal source transmitter performance, the use of third-order intermodulation distortion power amplifier (IMD3) to quickly and accurately predict the impact of the power amplifier of the transmitter EVM, and deduced the presence of both phase noise and third-order intercept tone when the EVM expression. At the same time, gives the EVM and SNR, BER relationship.
|