Study On The Effects Of Pluse Radiation Distortion On The Performance Of IR-UWB

Recently, more and more effort was devoted to short-range ultra-wideband (UWB) communication systems, which operate under the FCC emission limits regulated for the allocated indoor/outdoor UWB band. After a brief introduction to the three prevailing UWB communication schemes, viz. the impulse radio (IR), the direct sequence-CDMA (DS-CDMA) and the multi-band OFDM (MB-OFDM), and a detailed comparison of their technical characteristics, the IR-UWB is considered as an example to study the influence of the radiation characteristics of UWB antenna on the UWB communication system performance.As is well known, the radiation of UWB antenna will introduce angle-dependent pulse distortion, i.e., the pulse waveforms radiated in different directions could be obviously different. In illustration of such angle-dependent distortion, a Gaussian pulse excited aperture is studied with uniform aperture field distribution, linearly-tapered aperture field distribution and Gaussian aperture field distribution, respectively. It turns out that more obvious pulse distortion can be observed as the radiation direction deviates more from the aperture's principal radiation direction. Generally, the peak value of the radiated waveform reduces and the pulse width increases for larger direction angle, and more serious angle-dependent pulse distortion can be observed for antenna with higher directivity.Due to the angle-dependent pulse distortion, UWB receivers at different directions will capture different pulses, and thus the angle-dependent pulse distortion has different impacts on the performance of IR-UWB communication. For IR-UWB system with BPSK modulation, the bit error rate is calculated for UWB receiver at different directions under situations of fixed signal-to-noise ratio or fixed noise power spectrum density in the channel. The results indicate that the angle-dependent pulse distortion of the UWB antenna has considerable effects on the performance of IR-UWB. The selection principle of the template pulse for IR-UWB communication system is also investigated.