Guest Editorial: "Special Issue: Ultra-Wideband Antennas and Propagation"

In February 2002, the Federal Communications Commission (FCC) released the unlicensed frequency band of 3.1–10.6 GHz for commercial applications. This has greatly spurred the development of commercial ultra-wideband (UWB) communications systems and devices worldwide. Due to the extremely wide spectrum, the UWB-based systems have the potential to achieve high data rate in the order of 500Mbps up to even Gbps. On the other hand, in the low power and low data rate applications, the research and development effort has been focused on high accuracy localization or positioning systems. In UWB technology, to cater for the increase in transmission speed, reduction in power consumption and transceiver cost, a comprehensive investigation of UWB system issues, RF circuitry, antenna design, and propagation characteristics must be carried out. This Special Issue with eight strictly selected papers presents advanced progress in research and development of Antennas and Propagation for promising UWB applications. We have to mention here that the response from the community to this Special Issue is pretty good after the call for paper was announced for only six months, and we received 16 very high quality papers. The contributions cover almost all topics related to UWB antennas and propagation. Unfortunately, due to the limited space available, we have to make a very hard decision to include only eight of them in this Special Issue. Some of them have been recommended for possible publication as regular papers in International Journal of Wireless and Optical Communications in the future. The major content of the eight papers in this Special Issue can be summarized below. The first paper entitled “Antenna Time Domain Planar Near-field Measurement System” by N. Wang et al. reports on the advanced progress in development of time-domain near-field measurement. Such time-domain near-field measurement technology is the key to obtain antenna under test’s (AUT) far-field radiation patterns in frequency domain by Fourier transforming the far-field in time domain which is the outcome of transform of near-field far-field and time domain probe correction. The work started in 1996 and has been focused on developing software for general measurement system design, such as system control, time domain sampling, frequency domain probe correction, near-field far-field transform, results correction and analysis. In 2003, the authors built the first antenna time