Passive Components for Ultra-Wide Band (UWB) Applications

Abstract

UWB technology brings the convenience and mobility of wireless communications to very high-speed interconnects in the home and office due to the precision capabilities combined with the low power. This makes it ideal for certain radio frequency sensitive environments such as hospitals and healthcare as well as radars. UWB intrusion-detection radar is used for detecting through the wall and also used for security with fuse avoidance radar, precision locating and tracking (using distance measurements between radios), and precision time-of-arrival-based localization approaches. The FCC issued a ruling in 2002 that allowed intentional UWB emissions in the frequency range between 3.1 and 10.6 GHz, subject to certain restrictions for the emission power spectrum. Other definitions for ultra-wideband range of frequency are also used such as any device that has 500 MHz bandwidth or fractional bandwidth greater than 25% is considered an UWB enable high data rate to be transferred with a very low power that does not exceed À41.3 dBm. The main advantage of UWB technology is that it has the ability to transmit high bandwidth data between various devices with distances in the order of 10 m far from each other, such as home or office appliances with high sped transfer which may reach 1Gbit/s. There are many components that are designed and used in UWB systems such as antennas, power dividers/combiners, filters (LPF, BPF, etc.), rectennas, filtennas, etc. Many types of antennas are able to achieve UWB. Monopole antennas are usually used as linearly polarized antennas which prove to be the best whelming choice for use in various automobiles and mobile equipment. Log parodic and Yagi antennas are other types of UWB with high gain. Electromagnetic band gap (EBG) structure as defected ground or split ring resonator are also used to improve the antenna bandwidth and achieve UWB. Many UWB filters are designed and implemented using modern techniques such as meta-material, tuning stubs, defected ground structures, modified CMRC (compact microstrip resonant cell), etc. These filters may be switchable or tunable in order to make notch frequencies within the passband to provide interference immunity from unwanted radio signals, such as wireless local area networks (WLAN) and worldwide interoperability for microwave access (WiMAX) that cohabit within the UWB spectrum. The need of compact multiband filtenna (filter combined with antenna) with the ability of covering the current standards at the microwave band and the next generation standards at the millimeter wave band simultaneously is raising. Also, the operation of cognitive radio and self-adaptive systems need to dynamically monitor the frequency spectrum in search of the unused licensed channels. All these applications need different types of filtenna which may be fixed, switchable or tunable that can operate in the UWB range of frequency and also with narrow band modes to cover for example UWB/WiMAX applications.