The utilization rate of licensed spectrum is very low in the time domain, frequency domain and space domain, while the unlicensed band is overcrowded seriously.

大部分授权频段在时域、频域和空间域的利用率很低，而公共频段出现了严重的频谱拥挤。

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Contrasted with the methods in time space domain, this one has high computation efficiency and is prone to image, because all its computation is in frequency space domain.

当在频率-空间域进行计算时，相对于纯粹的时间-空间域有限差分算法有计算效率高、成像方便的优点。

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The frequency domain and space domain anti-stealth techniques of radars are summarized, and Fight F-117A is taken as a typical example in order to discuss the radar detectability of stealth vehicles.

本文综合论述雷达的频域反隐身与空域反隐身技术并以F - 117a飞机为例探讨了隐身飞行器的雷达可探测性。

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