The utilization rate of licensed spectrum is very low in the time domain, frequencydomain 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。
2
Contrasted with the methods in time spacedomain, this one has high computation efficiency and is prone to image, because all its computation is in frequencyspacedomain.
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。
3
The frequencydomain 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.