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This study presents a single‐layer via‐less antenna array operating in circular polarisation for wide‐band operation in C‐band. The antenna comprises 2×2 disc based elements arranged in a sequential rotation architecture. Each element is tuned to exhibit multiple resonances with good circular polarisation performance over a broadband of frequencies. A proper feeding network is then designed so that the resulting array is capable of a wide‐band operation and enhanced gain, equalising the frequency response of the set of elements. Simulations are validated by fabricating and measuring a prototype realised on a commercial FR408 dielectric substrate. Notwithstanding a dimension of only 7×7cm2, that is only 1.66λ02 at centre frequency, measured performance of the proposed array can be summarised in a gain better than 7 dB over an operation bandwidth of 24.45%, which is an unmatched result, given the via‐less single‐layer technology and the specific available area. [ABSTRACT FROM AUTHOR]

The identify friend or foe antenna is a complement to many radar antennas which allows the discrimination between friendly and hostile targets by receiving identification data. Such antenna must synthesize both a sum and a difference pattern in azimuth to allow target discrimination and must point to the target being inquired, either by mechanical or electronic scanning in azimuth. In this paper, to attain optimal electronic scanning, an array of antennas lying on a generic planar curve is considered. A multi-objective optimization based on the invasive weed optimization algorithm is then applied to the shape of such curve, aimed at maximizing performances. Whereas a conventional linear array of 6 elements can effectively scan ±30°, with respect to broadside, the proposed array, notwithstanding the same number of elements and overall length, can scan ±45° and still synthesize effective sum and difference patterns. [ABSTRACT FROM AUTHOR]

ABSTRACT A pentagonal circular polarized subarray composed of five elements is proposed for operation at 2.45 GHz. The array is based on the sequential rotation architecture (SRA), implemented with a sequential phase distribution network. Despite a more complex design in comparison to the canonical 4-elements SRA, a pentagonal subarray is more suited to be packed in a Bucky-ball or icosahedral arrangement, ideal for smart antennas with wide angle spatial coverage. A single-layer via-less prototype is fabricated on a common FR4 substrate. Measurements show a realized gain of 6.15 dBi with a polarization purity exceeding 20 dB at 2.45 GHz. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1077-1081, 2017 [ABSTRACT FROM AUTHOR]