Modeling and Hardware Emulation of Satellite-to-Ground Channel Incorporating Satellite Posture

‍ ‍To address the issue of traditional satellite-to-ground channel models and their hardware emulation methods that do not consider the impact of satellite posture on channel characteristics， a novel satellite-to-ground channel model that incorporates satellite posture based on the framework of the geometry-based stochastic model （GBSM） is proposed in this paper. The model constructs four independent coordinate systems and introduces a posture correction matrix to accurately describe the influence of satellite posture changes on the satellite-to-ground channel characteristics. Based on this model， a satellite-to-ground channel hardware emulator using a field programmable gate array （FPGA） is designed and developed. The hardware emulator utilizes a differential iteration algorithm to generate channel fading data， significantly enhancing the real-time capability of hardware emulation and ensuring the generated fading data matches the actual scenarios. In addition， a parallel processing architecture is utilized to support satellite-to-ground channel emulation with a maximum bandwidth of 640 MHz. Moreover， a parallel interpolation algorithm is introduced to match the fading data with the parallel architecture. This algorithm interpolates the serial fading data into parallel fading data at the same rate， ensuring accurate emulation of the channel characteristics. Furthermore， to achieve precise control over the output signal power of the hardware device， a pre-trained power calibration method is designed. This method utilizes pre-training with internal calibration source signals to calculate the gain introduced by the entire emulation process， enabling accurate power compensation and precise control over the output signal power. Finally， simulation and analysis are conducted in typical scenarios to derive the output results of the hardware emulator and examine their statistical characteristics. The results demonstrate that the measured probability density function （PDF） and Doppler power spectral density （DPSD） of the output data align closely with theoretical values， confirming that the hardware simulator designed in this study accurately reproduces satellite-to-ground channel variations caused by changing satellite attitudes in real-world scenarios. In conclusion， this paper’s satellite-to-ground channel model， which factors in satellite posture， and the associated hardware emulator overcome the constraints of traditional approaches and hold significant potential for optimizing， evaluating， and verifying satellite communication systems.