Study On Chirp Based Cognitive Radio Technology For UWB System

Chirp signals has long been widely used in the area of radar systems. With the development of related technology, the chirp based UWB systems are not only used for accurate position location and vehicle radar systems, but also applied for spread spectrum communication. In 2005, a proposal based on chirp spread spectrum(CSS) was proposed for IEEE 802.15.4a by Nanotron Technologies. Chirp signals and associated technique of pulse compression which is extensively used in radar systems are well suited for spread spectrum transmission and gaining more and more attention from academia and industry. Besides, recent development of surface acoustic wave(SAW) technology has made all-passive and low cost SAW chirp delay lines further used for generating Chirp signals and implementing matched filters and correlators. On the other side, UWB system combined with cognitive radio technology which makes use of cognitive virtue to adopt flexible spectrum sharing strategy between UWB system and other narrow bandwidth system has been becoming a more and more hot topic. This paper chooses chirp signal as the starting point and explores the implementation details about chirp based UWB system and chirp based Cognitive UWB system respectively. The subject of this paper is from one of sub-topics of the National Natural Science Fund project, which has significant theoretical and practical values.This paper firstly discusses the basic design ideas and structure of the chirp based UWB system. Based on the feasibility of chirp spectrum spread principles applied in UWB system, we extend it to the further implementation of cognitive UWB system and propose two kind of UWB systems scheme which take the initiative to avoid the narrow bandwidth communication system's working frequency band and suppress the corresponding interference, and it is also called cognitive UWB system. The two different schemes are based on single band chirp signal and multi-band chirp signal from the point view of the spectrum respectively which both guarantee the transmitting signals in accordance with FCC spectral mask and coexistence, interference avoidance with other traditional narrow band system, and most importantly have the merits of both the multi-band OFDM-UWB scheme and the pulsed UWB scheme.