A novel Narrowband Interference (NBI) suppression scheme using a Soft Limiter (SLM) is proposed for a digital noncoherent receiver in Time-Hopping Pulse Position Modulation Ultra Wideband (TH-PPM-UWB) communications. The NBI suppression is carried out in the analog domain (before the digital processing) via a feedforward structure. The suitability of this NBI suppression concept is confirmed by the performance evaluation in the presence of strong NBI. We consider both an unmodulated single-tone interference and Orthogonal Frequency Division Multiplex (OFDM) interference from an IEEE 802.11a Wireless Local Area Network (WLAN). As a comparison, we also investigate the use of a Hard Limiter (HLM). To ensure an effective NBI mitigation, we discuss the threshold selection of the SLM/HLM in the case of full-resolution as well as b-bit receivers (1 ≤ b ≤ 4). When b ≠ 1, a joint adjustment of both the threshold and the Automatic Gain Control (AGC) is required. In the presence of the strong OFDM interference, a block-based threshold adaptive NBI suppression technique is proposed. Moreover, we also evaluate the frequency-dependent performance of the proposed receiver.
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