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A wide-beam circularly polarized (CP) asymmetric-microstrip antenna with four unequal circular-patches is proposed for global navigation satellite systems. Four unequal circular-patches are integrated symmetrically onto corners of a square microstrip radiator for CP radiation with wide-beamwidth. The measured 3-dB axial ratio (AR) bandwidth of the proposed antenna is 24.0 MHz (1.568–1.592 GHz) with a 3-dB AR beamwidth of around 180° across the bandwidth and a 10-dB return loss bandwidth is 56.0 MHz (1.556–1.612 GHz) with a gain of more than 5.0 dBic. The overall size of the antenna is \bf 0.373\boldsymbol\lambda\bf o \bf{\times 0.373{\boldsymbol\lambda}\bf o} \bf{\times 0.016}{\boldsymbol{\lambda}\bf o} at 1.6 GHz. [ABSTRACT FROM PUBLISHER]

ABSTRACT A moon-shaped printed monopole antenna with modified ground plane is proposed for broadband circularly polarized (CP) radiation. Proposed monopole antenna consists of a moon-shaped radiator with a microstrip feed line. The moon-shaped radiator and its ground-plane shaped are optimized for broadband CP radiation. Impedance matching is improved using the quarter-wave transformer along with microstrip line. The measured results of the prototype antenna on FR4 substrate are 1.67 GHz (2.08−3.75 GHz) for 2.5-VSWR bandwidth, 1.48 GHz (2.28-3.76 GHz) for 3-dB axial ratio (AR) bandwidth, and gain around 1.6 dBic across the 3-dB AR bandwidth. Overall antenna volume is 0.466λ0 × 0.70λ0 × 0.008λ0 at 3.0 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1135-1139, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A leaky-wave antenna (LWA) based on tapered composite right/left-handed unit cell sections is proposed for wideband broadside radiation. The substrate-integrated-waveguide metamaterial based antenna consists of three sections with varying slot lengths for unit cells. The measured broadside gain of the proposed tapered antenna prototype is higher than 9.0 dBi over a bandwidth of 4.7% (8.825-9.250 GHz). The bandwidth of the proposed tapered LWA for 1-dB gain variation doubles that of the conventional LWA with non-tapered unit cells. In addition, the proposed antenna is able to scan the beam from −72° to +75° over a frequency range of 8.0-13.0 GHz with the gain greater than 9.0 dBi. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:624-629, 2015 [ABSTRACT FROM AUTHOR]

A compact circularly polarized (CP) square-ring slotted patch antenna with vias is proposed for global navigation satellite systems (GNSS). Four square-ring-shaped slots are cut symmetrically onto a square patch radiator along its diagonals for wide-angle CP radiation and miniaturization. The antenna size is further reduced by grounding the central patches surrounded by the square-ring-shaped slots. An antenna prototype with an overall size of 60 mm\,\times \,60 mm\,\times \,5 mm shows a measured 10-dB return loss bandwidth of 90.0 MHz (1.565–1.655 GHz) with a maximum gain of 4.65 dBic. The measured 3-dB axial ratio (AR) bandwidth is 35.0 MHz (1.57–1.605 GHz) with a 3-dB AR beamwidth of more than 140^\circ across the bandwidth. [ABSTRACT FROM PUBLISHER]

In this study, a compact, triple-band, circularly polarised stacked microstrip antenna is proposed over the artificial metasurface called reactive impedance surface (RIS) for enhancing antenna radiation efficiency for GPS applications. The proposed design utilises the concept of combining multi-stacked patches with RIS as imaginary-impedance metamaterial-ground-plane for selective frequency reduction of lower bands with improvement in antenna radiation properties for multi-band applications. The circularly polarised (CP) radiation with compact antenna size is achieved for triple-band GPS frequencies of L1 (1.575 GHz), L2 (1.227 GHz) and L5 (1.176 GHz) by placing three stacked patches with two different pairs of symmetric slits, four different sized symmetric cross-shaped slots and truncated corners over RIS. As RIS meta-surface reduces the wave penetration through the lossy substrate beneath it, the proposed stacked patch antenna over RIS demonstrates enhanced forward gain with suppressed back radiation. The measured results for antenna prototype are (1.168-1.185 GHz): L5 band, (1.2-1.245 GHz): L2 band and (1.51–1.59 GHz): L1 band for 10 dB return loss bandwidth with good CP radiation. Forward (boresight) right-handed CP gain of 2.88 dBic (L5 band), 3.25 dBic (L2 band) and 5.53 dBic (L1 band) is observed for compact antenna overall volume of 0.32 λo × 0.32λo × 0.024 λo at 1.2 GHz. [ABSTRACT FROM AUTHOR]

A wideband, single-feed, circularly polarized, stacked, square, slotted microstrip patch antenna is proposed for radio-frequency-identification-reader applications. The proposed antenna consists of an upper square asymmetric slotted patch, stacked over a lower square asymmetric slotted radiating patch and a microstrip stub, along with a coaxial feed. The wideband circularly polarized radiation of the antenna is achieved using a microstrip stub in the lower patch and a stacked slotted square patch. The proposed antenna is designed using a combination of low-cost FR4 substrate and foam. The measured 10 dB return-loss bandwidth of the antenna was around 21% (833 MHz to 1033 MHz), and the 3 dB axial-ratio bandwidth of the antenna was around 13.4% (835 MHz to 955 MHz). The gain was around 7.0 dBic over the 3 dB axial-ratio bandwidth. The overall antenna volume was 0.601?0 ? 0.601?0 ? 0.895?0 (where ?0 is the free-space wavelength at 900 MHz). [ABSTRACT FROM AUTHOR]

The reflection coefficient phase is studied for four different artificial magnetic conductors (AMCs) having canonical frequency selective surface (FSS)-type two-dimensional periodic structures to be used as back reflectors for an aperture antenna. The bidirectional circularly polarised (CP) radiation of the octagonal-shaped aperture (OSA) antenna is made unidirectional using these AMC surfaces as ground planes. The antenna height measured from the upper surface of AMC reflector to the OSA radiator is chosen to be small to realise low-profile antenna: 0.0825λo at the lowest analysis frequency of 4.5 GHz. Different antenna parameters like voltage standing wave ratio (VSWR) of 2, 3-dB axial ratio (AR) bandwidth, gain, and front-to-back ratio are studied and compared for these four AMCs and the conventionally used perfect electric conductor (PEC) ground plane as back reflectors. Four different aperture shapes with fixed aperture perimeter are designed to integrate with the square-loop AMC as back reflector to realise a low-profile unidirectional wideband CP aperture antenna. Hexagonal-shaped aperture antenna over the squareloop AMC shows the largest measured 3-dB AR bandwidth of 23.33% (5.65-7.05 GHz), VSWR of 2 bandwidth of 36.67% (5.16-7.36 GHz), and the gain of around 7 dBic over the band for overall antenna volume of 0.72λo × 0.60λo × 0.19λo at 6.0 GHz. [ABSTRACT FROM AUTHOR]

Circularly polarized diagonally symmetric slotted microstrip-patch antennas are proposed with compact size. The compact circularly polarized (CP) diagonally symmetric slotted microstrip-patch (DSSMP) antenna design rules are also summarized. Circularly polarized radiation can be achieved using any arbitrarily shaped slots in diagonal directions on the square microstrip-patch antenna. Different shapes for the slots are studied and compared, based on the fixed overall volume of the antenna for circularly polarized diagonally symmetric slotted microstrip-patch antennas. The cross-shaped-slot diagonally symmetric slotted microstrip-patch antenna is compact when compared with the circular-, square-, and circular-ring-shaped diagonally symmetric slotted microstrip-patch antennas. A measured 3 dB axial-ratio (AR) bandwidth of around 0.7% (6.0 MHz) with 2.0% (18.0 MHz) impedance bandwidth was achieved. The measured boresight gain was more than 3.3 dBic over the operating band, while the overall antenna size was 0.272λ0 × 0.272λ0 × 0.0138λ0 at 0.905 GHz. [ABSTRACT FROM AUTHOR]

A wideband, circularly polarized (CP), artificial magnetic conductor (AMC) reflector backed octagonal-shaped aperture (OSA) antenna is proposed for unidirectional radiation. The proposed antenna consists of an OSA fed by microstrip along with L-shaped stub and an AMC reflector. Bidirectional radiation of OSA antenna is changed to unidirectional radiation using an AMC reflector. The antenna height measured from the upper surface of the AMC reflector to OSA radiator is chosen to be small to realize a low-profile antenna: 0.0825\lambdao at the lowest analysis frequency of 4.5 GHz. Three different surfaces are studied and compared as back reflectors for OSA: perfect electric conductor (PEC), single layered AMC surface, and double layered AMC surface. The OSA with double-layered AMC surface demonstrates the largest measured 3-dB axial ratio bandwidth of 33.2% (5.20–7.19 GHz) with impedance bandwidth of 36.2% (5.04–7.21 GHz) for VSWR of 2. Almost constant gain of around 7 dBic is achieved over the band for the overall antenna volume of 0.72\lambdao\times 0.60\lambdao\times 0.19\lambdao at the center frequency of 6.0 GHz. [ABSTRACT FROM PUBLISHER]

Compact, asymmetric\symmetric-slotted\slit-microstrip patch antennas on reactive impedance surface (RIS) are proposed and studied for circularly polarized (CP) radiation. The antennas consist of a slotted-slit-microstrip patch on a RIS substrate. The CP radiation with compact size is achieved by asymmetric\symmetric-slot-slit cut along the orthogonal\diagonal directions of the patch radiator. The asymmetric\symmetric-slotted\slit microstrip patches on the RIS structure are used for further miniaturization of the antenna with improvement in CP radiation. The measured results of the compact asymmetric-cross slotted square patch antenna are 1.6% (2.51–2.55 GHz) for 3-dB axial ratio bandwidth, 5.2% (2.47–2.60 GHz) for 10-dB return loss bandwidth, and 3.41 dBic for gain over 3-dB axial ratio bandwidth. The overall antenna volume is 0.292\lambdao\times 0.292\lambdao\times 0.0308\lambdao on a low cost FR4 substrate at 2.5 GHz. [ABSTRACT FROM PUBLISHER]

A multilayered composite right/left-handed (CRLH) based leaky-wave antenna is proposed for the continuous beam scanning from backward to forward direction with consistent gain. The antenna comprises a substrate integrated waveguide (SIW) with an array of the CRLH unit cells. The CRLH unit cell is formed by a slot cut on the upper ground of the SIW, and a parasitic patch beneath the slot. The antenna achieves continuous beam scanning against frequency and the optimal boresight gain at the balanced condition frequency. The antenna prototype with 15 unit cells exhibits the measured beam scanning angle of -66^\circ to 78^\circ over the frequency range from 8.0 to 13.0 GHz with a consistent gain of more than 9.0 dBi. [ABSTRACT FROM PUBLISHER]

A compact, asymmetric-slotted-slit-microstrip patch, based antenna on a reactive impedance surface (RIS) is proposed and studied for the circularly polarized (CP) radiation.The antenna consists of a slotted-slit-microstrip patch on a RIS substrate. The CP radiation with compact size is achieved by asymmetric slots and slits cut along the diagonal and orthogonal directions of the patch radiator. The asymmetric slotted-slit-microstrip on the RIS structure is used for further miniaturization of the antenna with CP radiation. The measured results of the proposed antenna are 2.1% (2.625-2.68 GHz) for 3-dB axial ratio bandwidth, 9.5% (2.575-2.82 GHz) for 10-dB return loss bandwidth, and 3.87 dBic for gain at the boresight. The patch radiator size is 0.187 λ × 0.179 λ on a low cost FR4 substrate at 2.6 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2505-2510, 2012; this online at wileyonlinelibrary.com. DOI 10.1002/mop.27147 [ABSTRACT FROM AUTHOR]

The single-feed, circularly polarized microstrip antennas (CPMAs) based on the slotted-ground plane are investigated for radiofrequency identification readers.The conventional CPMA with truncated corners is also studied to compare with the proposed CPMA's performances. In the proposed designs, four square slots with asymmetrical configuration are etched in the diagonal directions on the ground plane of the antenna to achieve circularly polarized radiation. The proposed CPMAs are designed with low-cost FR4 substrate and RO4003C substrate and their performances are compared. The antenna bandwidth is also studied on thin and thick dielectric substrates. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2304-2309, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27075 [ABSTRACT FROM AUTHOR]

A technique is demonstrated to generate circularly polarized (CP) radiation of the compact diagonally asymmetric-slotted microstrip patch antennas. Design rules for the single-feed, compact, circularly polarized microstrip antennas (CPMA) with any arbitrary-shaped slots along the diagonal directions are first summarized. Four, compact, CPMA with circular-, square-, cross-, and square-ring-shaped slots along the diagonal directions are proposed and compared based on a fixed overall antenna size. A compact, CP, cross-shaped slotted, microstrip antenna is fabricated and measured to verify the proposed technique experimentally. The measured 3-dB axial-ratio bandwidth of about 6.0 MHz is achieved with 10-dB return loss bandwidth of 19.0 MHz while measured gain of the antenna is 4.0 dBic at 930 MHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1920-1927, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26959 [ABSTRACT FROM AUTHOR]

A compact cross-shaped slotted microstrip patch antenna is proposed for circularly polarized (CP) radiation. A symmetric, cross- shaped slot is embedded along one of the diagonal axes of the square patch for CP radiation and antenna size reduction. The structure is asymmetric (unbalanced) along the diagonal axes. The overall size of the antenna with CP radiation can be reduced by increasing the perimeter of the symmetric cross-shaped slot within the first patch quadrant of the square patch. The performance of the CP radiation is also studied by varying the size and angle variation of the cross-shaped slot. A measured 3-dB axial-ratio (AR) bandwidth of around 6.0 MHz is achieved with the CP cross-shaped slotted microstrip antenna, with an 18.0 MHz 10-dB return-loss bandwidth. The measured boresight gain is more than 3.8 dBic over the operating band, while the overall antenna volume is 0.273\lambdao\times 0.273\lambdao\times 0.013\lambdao (\lambdao operating wavelength at 910 MHz). [ABSTRACT FROM PUBLISHER]

A novel symmetric-aperture antenna is proposed for broadband circularly polarized (CP) radiation using a coplanar waveguide (CPW) feed. The proposed antenna consists of a CPW-feed and a wide symmetric aperture along the diagonal axis. A symmetric-aperture consists of two diamond-shaped sections. The symmetric-aperture and CPW-feeding structure are fabricated on the same plane of a dielectric substrate. Wideband CP radiation is achieved by changing the arms of symmetric-aperture and stripline length. The measured bandwidths of 3-dB axial ratio (AR) and 10-dB return loss are around 68% (2.4–4.85 GHz) and 107% (1.6–5.25 GHz), respectively. The measured boresight gain is more than 3.0 dBic over the CP bandwidth. Overall antenna size is around 0.7\lambdao\times 0.7\lambdao\times 0.019\lambdao at 3.5 GHz. [ABSTRACT FROM AUTHOR]