Design&Study Of Broadband Cavity-backed Multislot Antennas

Abstract: The history of slot antennas dates back to the1940s. As one kind of low-profile andcost-effective antennas, microstrip-fed narrow slot antennas have been intensively studied. With theimprovement of the bandwidth and their intrinsic advantages, the slot antennas can be applied inbroadband wireless systems. However, some applications, such as indoor base station andidentification systems, the unidirectional beam is required. The objective of this thesis is to proposethe design approach of broadband cavity-backed microstrip-fed multislot antennas. Two differentantenna prototypes have been fabricated to verify the validity of the design approach. The maincontent is organized as follows:At first, combined with the research on the equivalent circuit model of microstrip slot antennas,an equivalent circuit model for multi-slot microstrip antennas has been proposed. The correction ofthe equivalent circuit model has been verified by the software ADS. The equivalent circuit model iseasy to understand and be calculated.Then, a novel cavity-backed microstrip-fed multislot antenna (CBMSA) with a simple structurefor wideband application is proposed. Two different narrow, rectangular slots are combined as oneradiator and the antenna is fed by microstrip line terminated with a wide, rectangular patch. Ametallic cavity is placed under the feed line to obtain unidirectional radiation pattern. The reflectioncoefficient, radiation pattern and gain over the antenna’s operational bandwidth have beennumerically and experimentally studied and compared. It is shown that the impedance bandwidth ofthe antenna is from5to10.3GHz, which is about69%(for|S11|lower than-10dB). Goodpolarization purity with cross-polarization level lower than18dB and a front-to-back ratio betterthan12dB are obtained.Finally, a bandwidth-enhanced cavity-backed microstrip-fed multislot antenna has beenproposed and the performance parameters have been measured and analysed.