Chirp Broadband Ultra-wideband Communications Technology Research,

The fading effect of indoor wireless channel is prominent. In order to overcome the effects of flat fading, spread spectrum (SS) technique is used for better communication quality. Common SS techniques are direct sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS) and ultra wideband (UWB). DSSS and FHSS suffer the disadvantages of high complexity, high power consumption and heat dissipation. UWB is good for indoor wireless communication, but it has the disadvantages of high peak power, short communication range and strong potential interference for other devices. In order to meet the new demands of Wireless Personal Area Network (WPAN), such as low cost, low implementation complexity and low power consumption, a new solution is tried in this thesis.This work is to find a Chirp UWB based solution for WPAN. A Chirp UWB based technique is introduced and discussed. The research includes the following topics:The basic ideas of Chirp UWB, including pulse compression theory, chirp spread spectrum (CSS) and UWB. Pulse compression is the foundation of CSS. It provides CSS with the ability of high processing gain and anti-interference. If the bandwidth of CSS is large enough, CSS is Chirp UWB. Chirp UWB inherited the advantages of both CSS and UWB. Moreover, it can overcome the disadvantages of high peak power and short communication range for UWB.Common modulation techniques for Chirp UWB, including binary orthogonal keying (BOK) and direct modulation (DM) are discussed. DM can be combined with time overlapping, which improves the efficiency of modulation. However, time overlapping has some disadvantages. A high order modulation solution is proposed. Besides, overlapping in the frequency domain is proposed for better system performance.Receiver structure for Chirp UWB indoor wireless communication system is discussed. A differential scheme is used to avoid random phase introduced by the channel. Since the multipath resolution for Chirp UWB can be in the order of less than t 1ns, a RAKE receiver structure can be used for better performance. Multipath combining technique is discussed in this work.Multiple access for Chirp UWB is discussed. To mitigate the multiple access interference (MAI), several schemes are reviewed and a new solution is proposed. The solution is based on "Chirp Code" and can meet the needs for multiple user multiple data rate.