Modern antennas are usually operating on platforms with existence of other antennas or unintentional radiators. In many scenarios, the multiple antennas mounted on one platform have highly contrasting power levels and overlapping frequency bands, due to their different usage. Besides the impact upon antenna pattern and near field distortion introduced by the platform, the mutual coupling among antennas on board is another very interesting and challenging problem. It is of vital importance since it can cause severe electromagnetic compatibility (EMC) problem, which may makes the multiple functional modules of the system unable to operating simulateously. This issue will be even worse when the modern stealth technology are requiring wider frequency band and lower power level.