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In this article, a wide-band circularly polarized slot antenna array with reconfigurable feed-network for WiMAX, C-Band, and ITU-R applications is proposed. Different novel methods are used in proposed array to improve antenna features such as impedance matching, 3 dB axial-ratio bandwidth (ARBW), gain, and destructive coupling effects. Miniaturized dual-feed square slot antenna, with one attached L-shaped strip and a pair of Tshaped strip at ground surface for improving impedance matching and circular polarization (CP) purity, is presented. For further enhancement of CP attributes, reconfigurable sequentially rotated feed network is utilized to obtain wider 3 dB ARBW. Furthermore reconfigurable property of network gives controlling Right and Left handed CPs, respectively. Finally, a special form of Electromagnetic Band gap structure is employed on top layer of substrate that provides high isolation between radiating elements and array feed network to enhance overall performance of antenna. The measured results depict 3 dB ARBW from 4.6 to 7.2 GHz, impedance bandwidth from 3.3 to 8.8 GHz for VWSR<2, and peak gain of 10 dBi at 6 GHz. V C 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:825-833, 2015.

This article proposes the novel design of a coplanar waveguide fed (CPW-Fed) monopole ultra wideband (UWB) semifractal antenna with dual band-notched specification and circular polarization (CP) attributes at ITU-R (7.725-8.5 GHz). The semifractal patch of antenna is composed of unitcell which unitcell patterns form branchs of tree. The fractal geometry in radiator leads to have an effective impedance matching over the UWB spectrum. The Dual-band filtering property can be adjusted finely by embedding a pair of L-strips length inside the slotted conductor-backed-plane (SCBP) and mirrored defected ground structure (MDGS). Beside that, the length and position of Lstrips have great role in achieving CP in ITU-R band. The actual size of the miniature and fabricated antenna is limited to 15 3 15 3 1 mm 3 and it operates across 2.2-12.52 GHz for S 11 <210dB, except the bandwidths of 3.1-3.6 for WiMAX and 5-6 GHz for WLAN. The antenna has CP bandwidth from 7.5 to 8.5 GHz for axial ratio less than 3 dB. The antenna's parameters were investigated to fully understand their affects. Main parameters achieved from this analysis enabled the optimization of the antenna's entire performances. The prototype was fabricated, to validate the performance of antenna, through simulations and measurements. The measured results certify the antenna radiates omnidirectionally and has a large impedance bandwidth, dual-band rejection and CP property.

A unique slot antenna, for multiband applications with asymmetric coplanar waveguide feed is proposed. Different form of strips is used as grounded slits for providing multiband functionality. By adopting the proposed strips length and size, much wider impedance band width is achieved in two bands. Beside that an asymmetric feeding method is applied with rectangular patch for generating new resonances and good matching. By utilizing this novel method, good impedance matching is seen in both bands. The antenna size is only about 40 × 40, which covers the frequency band from 4.8 to 6.5 GHz in band#1 and from 7.8 to 8.4 GHz in band#2 for VSWR <2. Furthermore, by variation of strips positions and patch lengths, the control of the impedance band width and resonances are steered. Both simulated and measured results are illustrated and compared with each other to guaranties antenna's performance. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1653–1655, 2015