Channel emulators are the key instrument in radio performance testing. The fidelity of the emulated channel with respect to the target channel models directly affects the credibility of the testing result. In practice, due to some non-idealities of the radio-frequency (RF) components of the emulator, its intrinsic frequency response, i.e., the response of the bypass mode, may not be flat over the frequency band of interest, which leads to an excessive distortion over the target channel models, and hence a less accurate emulated channel. This problem could be even more profound when the emulator engages the band-stitching process for a wider-bandwidth emulation, especially in the transition frequency band between adjacent sub-bands. To enable high-fidelity band-stitched or even ultra-wideband channel emulation, we propose a novel digital pre-distortion concept in this work, where we pre-distort the target channel models according to the measured intrinsic response of the emulator to compensate for its effect on the emulated channel. The proposed method is numerically assessed with measured intrinsic responses of a commercial emulator, and the magnitude and phase variations of the stitched channel reduce by one order of magnitude in comparison to that of the conventional method.

中文翻译：

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启用高保真超宽带无线电信道仿真：频带拼接和数字预失真概念

信道仿真器是无线电性能测试的关键工具。仿真通道相对于目标通道模型的保真度直接影响测试结果的可信度。在实践中，由于仿真器的射频（RF）组件的一些非理想性，其固有频率响应，即旁路模式的响应，在感兴趣的频带上可能不是平坦的，这导致目标通道模型的过度失真，因此模拟通道的准确性较低。当仿真器使用带拼接过程进行更宽带宽的仿真时，这个问题可能会更加严重，尤其是在相邻子带之间的过渡频带中。为了实现高保真带拼接甚至超宽带信道仿真，我们在这项工作中提出了一种新颖的数字预失真概念，我们根据仿真器的测量固有响应对目标通道模型进行预失真，以补偿其对仿真通道的影响。所提出的方法通过测量商业仿真器的固有响应进行数值评估，与传统方法相比，缝合通道的幅度和相位变化减少了一个数量级。