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The authors propose the dual-tapered structure consisting of piecewise-linear inner taper and outer shaped-comb corrugation and the antipodal feeding section to present a modified antipodal Fermi antenna. This antenna exhibits the performance with wider band (3.6–15 GHz) in return loss responses, moderately high gain (5.1–14.5 dBi), high front-to-back ratio (24.8–38.9 dB) and available end-fire (29.8° beamwidth and -18.7 dB side lobe level) in radiation patterns. The current distributions demonstrate the characteristics of leakage, transverse waves among dual-taper and transition on balun. The proposed antenna presents the longitudinal conformation for mounting application and evaluate the pulse responses with linearity test for ultra-wideband (UWB) ranging and imaging applications. [ABSTRACT FROM AUTHOR]

The authors propose a reconfigurable angular diversity antenna, constructed with quad corner reflector arrays and switching control, that can provide effective polarisation. With switches in the control unit of the base station, a high radiation gain antenna to provide cross-pair polarisations for receiving operations, as well as an omni-directional radiation pattern for transmitting, has been reconfigured. Simulation and measurement results including frequency responses, radiation patterns and three-dimensional polar plots demonstrate the design of an antenna. Diversity measurements with correlation and root mean square (RMS) error vector magnitude (EVM) are presented in order to evaluate the proposed antennas. The angular diversity technique can be applied to wireless local area network (WLAN) and multiple-input and multiple-output (MIMO) systems. [ABSTRACT FROM AUTHOR]

The novel design of a T-coupled circular microstrip antenna with H-shaped aperture for active reflectantenna application is presented in this paper. The circular patch determines the frequency resonated; the H-shaped aperture is used to obtain the responses of the desired 2.4–2.48 GHz ISM band and the T-coupled feed line enhances the response of the band using the impedance-matching technique. Meanwhile, the dual-polarized ports of the T-coupled microstrip antenna are developed for the active reflectantenna and applied to a corner-wall structure. The antenna is capable of achieving high-directivity gain, wide bandwidth, high isolation, and low cross-polarization levels. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 120–125, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20919 [ABSTRACT FROM AUTHOR]

A compact active ring antenna integrated with diodes for direct conversion,or zero-IF detection, is presented. The circular aperture ring antenna exhibits a wide bandwidth and a high gain performance. The ring can act as a phase shifter to provide the necessary 90° characteristics to operate with I/Q signals for direct conversions. Two Schottky diodes can be connected to the ring structure and are used as a mixer. The authors focus on the case at 2.44 GHz, which is of particular interest for home networking communication systems. [ABSTRACT FROM AUTHOR]

An improved design of the U-shaped stub rectangular slot antenna with a tuning pad for enhancing the impedance bandwidth is proposed. By properly tuning the physical size of the copper pad, a wide impedance bandwidth of the antenna can be achieved for UWB applications. For 10 dB return loss, a impedance bandwidth of the antenna is covered from 2.3 to 12 GHz (135.7%). A gain variation from 2 to 6.82 dBi is obtained. [ABSTRACT FROM AUTHOR]

A non-constant fractal ratio antenna dependent on the Descartes circle theorem is proposed. The multi-band performances with compound log-periodic behaviour of Apollonian packing monopole antennas are presented. For comparison, typical Sierpinski, modified Sierpinski and Apollonian packing monopole antennas are examined. [ABSTRACT FROM AUTHOR]