In this paper, a compact dual-band MIMO antenna for WI-MAX and WLAN applications with improved isolation is proposed. The proposed design consists of two counter facing F shaped monopoles placed closely to each other with edge to edge spacing of 10 mm (0.1167λ 0 at 3.5 GHz). Each monopole element operates over 3.5 and 5.8 GHz bands. The isolation over the operating dual bands is achieved by using an elliptical slot and a rectangular parasitic strip. S 11 < −10 dB is achieved over 3.2-3.8 GHz and 5.7-6.2 GHz with S 12 < −20 dB. The overall dimension of the proposed antenna is 30 × 26 mm 2. The proposed antenna has correlation coefficient < 0.03, diversity gain > 9.8 dB with stable radiation pattern over the operating dual bands. The measured results are in good agreement with the simulated ones. The proposed antenna is a suitable candidate for MIMO applications.
This paper proposes low profile, high gain and wideband circularly polarized (CP) microstrip antennas (MSA), using gap coupled parasitic patches (PPs) on superstrate layer. Printed and suspended probe fed, CP MSAs are designed on a 1.59 mm thick FR4 substrate, and an array of closely spaced hexagonal PPs are printed on the bottom side of the 1.59 mm thick FR4 superstrate and placed at a height about λ 0 /8 above the ground plane, where λ 0 is the free space wavelength, corresponding to the central frequency of the operating frequency band. The gap coupled hexagonal PPs are not only used to enhance the axial ratio bandwidth (AR BW) and gain of the antenna, but also used to reduce impedance and gain variation of the antenna over the operating frequency band. 'Ant9' is a suspended MSA with 7 hexagonal PPs. A prototype 'Ant9' is fabricated and tested, which provides a peak gain of 9 dBi, S 11 < −10 dB, gain variation < 1 dB, and AR < 3 dB over 4.9 to 6.45 GHz frequency band. ARBW of 27.3% is achieved. The proposed 'Ant9' covers three frequency bands viz., 5.15 to 5.35 GHz, WLAN band, 5.725 to 5.875 GHz, ISM band, and 5.9 to 6.4 GHz, Satellite C band. The space fed antenna configuration reduces the cross polar radiation level (CPL) and increases the efficiency of the antenna. The measured results agree with the simulation ones. The overall size of 'Ant9' is 0.96λ 0 × 0.96λ 0 × 0.136λ 0 .
Abstract-In this paper, a compact MIMO antenna with improved isolation is proposed. Elliptical slots and an SRR like structure are employed to improve the isolation. The proposed MIMO antenna structure consists of two semi-circular radiators attached to a rectangular monopole which are mirror images of each other with edge to edge spacing of 0.125λ 0 , where λ 0 is the free space wavelength corresponding to the lowest operating frequency of the structure. Two square steps are added to the above semi-circular monopole to increase the effective path length to cover the lower frequencies. Thereafter, a semi-annular ring slot is introduced, and square steps above the semi-circular monopole are modified to curved steps to further improve the impedance bandwidth of the antenna. The mutual coupling over the wideband is reduced by placing elliptical slots and SRR like structure in the ground plane. The proposed antenna has impedance bandwidth of 2.1-12 GHz with |S 21 | < −20 dB over the entire frequency range. The antenna is designed and fabricated on an FR-4 substrate having overall dimensions of 38 mm × 33.4 mm × 1.6 mm. The measured results show a good correlation with the simulated ones. The envelope correlation coefficient (ECC) of the antenna is less than 0.02 over the entire band. The proposed MIMO antenna is an appropriate candidate for 3G, 4G, Wi-Fi, Bluetooth and UWB applications.
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