This paper investigates spectrum shaping in ultrawideband (UWB) communication systems in order to introduce spectral nulls to mitigate the impact of in-band narrowband interference (NBI) signals in the IEEE 802.15.3a UWB channel models. It has been seen that due to the restraint on their transmission power levels, UWB systems unavoidably suffer from the interference caused by the coexisting systems, making it extremely difficult to maintain adequate signal-to-noise-and-interference ratio (SNIR) levels. To this end, we propose the use of a “Digital Delay Filter” scheme, which is designed to generate a spectral null at the frequency being used by existing narrowband devices. Our results show that NBI can be effectively suppressed with the use of such null steering scheme, therefore improving the robustness of UWB systems to NBI. Also, it will be shown that the proposed delay filter outperforms a perfectly tuned notch filter.
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