Broadband-interference rejection for mobile satellite communications

Electromagnetic interference can disrupt mobile satellite communications in both military and commercial mobile applications. Not only is this true when a high-power terrestrial source is in close proximity to a mobile satellite receiver, but it can be especially problematic when the vehicle or nearby vehicle has its own onboard interference source that overpowers the desired satellite signal. This can cause interference even if that interfering signal were out of the frequency band of the desired satellite signal, due to non-ideal filtering. To exacerbate this problem, many of these sources are ultra wideband (UWB), consisting of electromagnetic energy spread over a very large bandwidth that may overlap the desired satellite channel. In this case even the fraction of the UWB interfering power that is in-band, could potentially overpower the satellite signal power. Algorithms exist that suppress interference in narrow and broadband applications. So, rather than introduce another exotic algorithm, this paper discusses a relatively simple system for broadband interference rejection that takes advantage of the difference in bandwidths between broadband interference and a narrowband satellite signal. This is achieved by adding an interference-detection channel to the satellite receiver that adaptively steers an antenna-pattern null, in order to reject terrestrial interference caused by emitters from nearby military vehicles, as well as onboard the receiver's own vehicle.