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Physical-Layer Modeling of UWB Interference Effects

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The NETEX program is focused initially on understanding the effects of interference from ultra-wideband UWB transmitters on legacy military radio receivers, nearly all of which are narrowband NB relative to the UWB signal, which can have a bandwidth on the order of 1 GHz. The purpose of this report is to document a set of mathematical models which have been developed to analyze the impact of UWB signals on NB receivers. This analysis work is being done in parallel with a UWB interference testing program being conducted by other parties. There are two main components to the work presented here. The first is a detailed analysis of the power spectral density PSD of the UWB signal, which shows the distribution of the UWB transmit power over frequency. The PSD is determined by 1 the spectrum of the basic UWB pulse and 2 pulse position modulationdithering and pulse amplitude modulation. A clear understanding of the PSD is important, because the main factor that determines the impact on a NB receiver is the total average UWB interference power within the receiver passband. This is demonstrated by the second main component of the report, which is a set of models describing the impact of UWB interference on several different representative receiver types, both digital and analog. The PSD gives the average power-per-Hz as a function of frequency for the UWB signal. The UWB PSD models developed here allow the PSD to be computed analytically for a wide range of different UWB signal types, and include the effects of pulse-position modulation PPM, random or periodic pseudo-random dithering of the pulse position, modulation or random or pseudo-random coding of the pulse amplitude, modulation symbols that include multiple UWB frames giving integration gain, and modulation of the actual pulse repetition frequency PRF by either a periodic PRF-modulating signal or by a random process such as a data signal.

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  • Radiofrequency Wave Propagation

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