A novel multiband and vertically/horizontally polarized omnidirectional antenna is proposed for 2G/3G/LTE mobile communication systems. The proposed antenna is a combination of a modified asymmetric biconical for vertical polarization (VP) and six printed dipoles with concentric placement for horizontal polarization (HP). The VP element consists of two modified cones with different diameters, designed to work in the multiband . Printed dipoles of the HP element are fed by a six-way power splitter printed on the substrate. The HP element is nested between two cones of the VP element, forming a compact structure. The bottom cone can be used as the reflector for VP and HP in the overlapping work frequencies band for 3G and LTE communication systems. The VP element achieves a bandwidth of 17.4% and gain of 1.5 dBi in the 806 960-MHz band. The HP element achieves a bandwidth of 35% (1880 2700 MHz) directly overlapping with the VP-element higher frequency band. An isolation of 25 dB is achieved in the overlapping band. The cross-polarization levels in the azimuth plane for both VP and HP are lower than 15 dB. Index Terms-Asymmetric biconical, broadband antenna, dualpolarized antenna, omnidirectional antenna, printed dipole.

In this paper, a compact multiple-input multiple-output (MIMO) antenna system with high isolation is proposed for 2.4 GHz wireless local area network (WLAN) application. The system is composed of two aperture-coupled shorted patch antennas with a spacing of 4 mm (only 0.032λ). The antenna is fed with an H-shaped coupling slot, and the defected shorting wall is used for high isolation. The proposed MIMO system exhibits an isolation of better than −20 dB and a maximum isolation of −43 dB at the central frequency. The envelope correlation coefficient is less than 0.01. The simulated and measured results show that the proposed antenna is a good candidate for MIMO system with higher isolation and better diversity.

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Abstract-A new design methodology for multi-band rectangular microstrip antenna using a metamaterial-inspired technique is proposed. The methodology uses the metal disk with SRR-shaped slot placed horizontally between the patch and the ground plane. With the introduction of the split ring, sub-wavelength resonance can be achieved while the dominant mode of patch cavity remains the same, so the antenna can operate at multi resonant frequencies. Construction of the multi-band antenna requires only the sandwiching of two etched circuit boards. The antenna has the properties of low profile, easy fabrication and low cost. Dual-band and tri-band antennas are fabricated and measured, which validate the design methodology.

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