Abstract-A novel antenna configuration for quad-band operation is presented. The quad-band antenna has a directional radiation pattern in four frequency bands, i.e., B1 (800-900 MHz), B2 (1.7-2.5 GHz), B3 (3.3-3.6 GHz), and B4 (5.1-5.9 GHz), covering all spectrums for existing wireless applications, such as GSM, PCS, WCDMA, WiFi, and WiMax. The operating frequency of the quad-band antenna can be adjusted by the use of a MEMS switch, making it suitable for cognitive radio applications. First a switchable quad-band antenna element is introduced. Then a two-element antenna array is developed to increase the antenna gain for base station applications featuring a gain value of about 9-11 dBi over all four frequency bands.Index Terms-Base station antenna, cognitive radio, quad-band antenna, switchable antenna.

Abstract-A printed dipole with an integrated balun features a broad operating bandwidth. The feed point of conventional balun structures is fixed at the top of the integrated balun, which makes it difficult to match to a 50-feed. In this communication, we demonstrate that it is possible to directly match with the 50-feed by adjusting the position of the feed point of the integrated balun. The printed dipole with the hereby presented adjustable integrated balun maintains the broadband performance and exhibits flexibility for the matching to different impedance values, which is extremely important for the design of antenna arrays since the mutual coupling between antenna elements commonly changes the input impedance of each single element. An equivalent-circuit analysis is presented for the understanding of the mechanism of the impedance match. An eight-element linear antenna array is designed as a benchmarking topology for broadband wireless base stations.Index Terms-Antenna array, base station antenna, broadband antenna, integrated balun, printed dipole, wireless communications.

A new tri-band dual-polarised omnidirectional antenna is proposed. The dual-polarised antenna consists of a metal cuboid body with a vertical slot for horizontal polarisation (HP) and a rectangular back metal cavity with two folded horizontal slots for vertical polarisation (VP). A metal HP feedline is employed to coupling feed the vertical slot while a metal VP feedline is used to excite the two horizontal slots. Due to the coupling feed and the orthogonality between the vertical and horizontal slots, the dual-polarised antenna features three bands and a high isolation. Experimental results show that the tri-band dual-polarised antenna covers the Chinese Unmanned Aircraft System bands (840.5-845, 1430-1444 and 2408-2440 MHz) with reflection coefficients <−10 dB and isolation >32 dB. Good omnidirectional radiation patterns are observed for both HP and VP.

No abstract