Design of microwave components for ultra-wideband applications

Abstract

The Federal Communications Commission (FCC) issued the Report and Order (R&O) in February 2002, in which an unlicensed band with 7500 MHz bandwidth was allocated for the use of Ultra-wide band (UWB). UWB technology is becoming more and more fascinating because of its potential for a vast number of applications such as wireless local area network (LAN) and personal area network (PAN). The benefits to employ UWB technology are that the ultra fast data transmission rate and simplicity of the system architecture can be achieved. Thus, implementation of an UWB system is an innovative topic over the field of wireless communications. Due to the existing measurement facility, we have to scale down the frequency range of UWB from 3.1 -10.6 GHz to 2.0 – 4.0 GHz. In this thesis, the emphasis of an UWB system and its components are described in detail. The main objective of this work is the design of the microwave components for UWB applications. UWB signals are pulse-based with a train of pulses are generated by a pulse generator in precise time interval. As the generator will significantly influence the performance of the system, so its characteristics are discussed in both the time and frequency domains. In this work, a monocycle pulse generator is proposed with only a few of electronic components employed. It brings out the simplicity of the circuit layout as well as the low-cost to be fabricated. As the energy of a pulse is spread across an extremely wide bandwidth in the frequency spectrum, bandpass filters are required to perform out-of-band signals rejection that fulfil the spectrum allocated by the FCC. Here a new bandpass filter is proposed based on parallel coupled structure and incorporating a CMRC dual-band stub. This leads to achieve a low-cost, wideband and sharp rejection bandpass filter. Employing the proposed monocycle pulse generator and bandpass filter, an UWB transmitter is constructed. In addition, a field programmable gate array (FPGA) processor is used to perform digital signal processing. And, the performance of the transmitter is discussed in both the time and frequency domains.

Date of Award	4 Oct 2004
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Leung TSANG (Supervisor)