Suppression of noise and narrowband interference in UWB indoor channel measurements

In this paper, the impact of the noise due to undersampling of noncoherent narrowband interference in time domain UWB channel measurements is investigated. Different measurements were carried out within the building for LOS and NLOS situations. The obtained results show that energy of external narrowband interference (especially at frequencies below 3.1 GHz) is spread over the whole measured bandwidth (1-12 GHz) as a quasi-white noise. This spreading is caused by the stroboscopic sampling receiver used in the measurement setup. The level of this additional noise is relatively high and its suppression is required for long-distance measurements. Suppression of the narrowband interference by an analogue bandpass filter directly after the receive antenna substantially decreases the noise floor and results in a large improvement of the signal-to-noise ratio.