Polarization filtering for narrowband interference suppression in ultra-wideband communications

To suppress narrowband interference (NBI) in an ultra-wideband (UWB) communications environment, a null phase-shift polarization (NPSP) filter is proposed. The proposed NPSP filter is a combination of a linear polarization-vector transformer (PVT), a conventional single notch polarization (SNP) filter, and an amplitude and phase compensator (APC). The NBI, which has polarized states different from those of the UWB, can be suppressed completely and the UWB signal can be recovered without distortion if the polarized states can be estimated exactly. Analytical and simulation results indicate that the signal-to-interference ratio (SIR) can be improved effectively after NPSP filtering. The proposed NPSP filter can be implemented in a time-hopping spread spectrum (TH-SS) or a direct-sequence spread spectrum (DS-SS) UWB system.