Filterbanks for Adaptive Transmit Filtering

The terrestrial terminals of the MUOS (Mobile User Objective System) satellite communication system transmit and receive in UHF bands near 300 MHz. These bands are used worldwide by a variety of narrowband voice and data systems. The MUOS waveform is not narrowband, however; and can interfere with these systems, possibly causing loss of critical links in host nations, including the US. UHF receivers that have the potential to experience MUOS interference are referred to as victim radios, and the MUOS system is designed to minimize the impact on victim radios by employing an adaptive notch-on-transmit filter Moreover; the MUOS terrestrial radio equipment must adaptively notch its transmit band to match high-interference subbands that are unilaterally notched at the basestation receiver. In this paper, two filterbanks are considered for use in adaptive transmit filtering in MUOS: the DFT filterbank and the modified DFT (mDFT) filterbank. The frequency resolution, achievable notch depth, computational cost, and design flexibility properties of the filterbanks are studied and compared in the context of MUOS adaptive transmit filtering.