On the Effect of Antennas on UWB Systems

Abstract- Ultra-wideband (UWB) communication systems are emerging as the most promising solution for high rate, short range wireless communication, with applications in home networking and high quality multimedia content delivery. This technique is being studied in numerous research projects and is the subject of a standardization work within the IEEE 802.15.3a task group. UWB systems are characterised by a radio signal whose fractional bandwidth, i.e the ratio between 3-dB bandwidth and center frequency, is greater than 25 % and by a very low radiated power (−41.3dBm/MHz at most, by FCC requirements [1]). UWB systems cover a spectrum of several gigahertz and the transmitted pulses are very short, in the order of a few nanoseconds. For these kind of pulses, antennas act as pulse shaping filters for which the impulse response depends on the direction of arrival (DoA) of the received waveform. During the standardization work in IEEE802.15.3a, a new UWB channel model was proposed, following the Saleh-Valenzuela cluster model [2] with some modifications [3]. The model is parameterised in four scenarios describing different communication situations, e.g., line-of-sight (LOS) or non line-of-sight (NLOS) communication and shadowing effect. A model for the direction of arrival was proposed in [4]. Combining these two models, we obtained a description of the channel suitable for including antennas in the system model. The antenna is modeled using a bank of discrete FIR filters with one filter for each direction of arrival. The antenna under study is a UWB monocone antenna designed at ENSTA as reported in [5]