Shortwave Channel Simulator Key Technology Research And Validation

Channel simulator is widely used in military and civilian communications systems,and performance testing is the primary means of guarantee the performance of the HFcommunication equipment. There are two ways of equipment performance testing, first,by the outdoor-based field test, and second, by the indoor test grounded on the HFchannel simulator. The latter one has the advantages of low testing cost, reproduciblechannel scenarios, and so on.However, the short-wave channel starts late in the domestic research and domesticproductions of HF channel simulators are usually narrow-banded, single-functionedwhereas the oversea products are very expensive. So, it is very vital to development anovel channel simulator with the features of wide band, multi-function and low cost.Based on the software radio architecture, the wideband HF channel simulator hasbeen proposed. Different scene channel analog functions can be realized by setting theparameters of different HF channel scenarios (e.g. Doppler frequency shift, DopplerSpread) by software rather than replacing the hardware.Firstly, the state of art and the applications of the shortwave channel as well as thechannel simulator were discussed, and the Watterson shortwave channel model wasrealized by sinusoidal superposition method, which offered the algorithm supports forthe implementation of shortwave channel simulator.Secondly, based on the FPGA digital chips, the Watterson and ITS short wavechannel model were realized. Among them, the core module included quadraturedown-converter module, low-IF signal processing module and the power controlmodule, respectively. Moreover, modular functions corresponding to the modules abovewere moving from the RF signal to low-IF signal to facilitate the signal processing,small-scale fading and large-scale fading, respectively.Finally, an experimental test platform has been established, the functions and theperformance of the channel simulator have been measured. The results demonstratedthat the frequency shift accuracy of channel simulator was1Hz and the attenuationaccuracy was0.5dB, which met the design requirements.The channel simulator raised by this study has various features such as low cost,selectable channel scenarios, configurable channel parameters (e.g. Doppler frequencyshift parameters, Doppler Spread parameters, etc.), which is appropriate for bothlaboratory condition and field environment. Furthermore, the design ideas as well as theoverall framework can be valuable references for the subsequent development andresearch of the channel simulator.