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A novel broadband horizontally polarized (HP) omnidirectional antenna is proposed for meteor-burst communication system in VHF. The proposed antenna is composed of three bowtie dipoles, which are concentrically placed to form a loop antenna. The bowtie dipole is shorted at the terminal by folded elements in order to reduce antenna size. The bowtie dipoles are fed by a three-way power divider. A slotted line balun is employed to achieve broadband impedance matching and realize balanced-to-unbalanced transformation. The designed HP omnidirectional antenna exhibits a fractional bandwidth of 24.7% with VSWR < 2 ranging from 39 to 50 MHz. Uniform omnidirectional radiation patterns in the azimuth plane with HP have been obtained. The loop antenna provides a relatively low gain of no more than 1.5 dBi. Therefore, a two-element HP antenna array is developed to enhance its gain. In order to reduce longitudinal dimension of the array, the two loop antenna elements are placed in reverse and employ differential feeding method to realize in-phase current. Both the simulation and measured results are used to verify the design approach. [ABSTRACT FROM PUBLISHER]

The paper proposes a wideband bowtie antenna for indoor base station applications. By using the inverted L-shaped coupling feed structure, the impedance bandwidth of the lower band is improved; while using the four tuning stubs, the upper band is enhanced. Thus, a wide impedance bandwidth of about 77.8% (VSWR les; 2) ranging from 1.38 to 3.14 GHz is obtained. In addition, by connecting two folded elements to the patches of the bowtie dipole, the compact dimensions of the antenna can be achieved. It also provides stable peak gain, unidirectional radiation patterns and low cross-polarization over the whole operating band. Owing to these good performances, the proposed antenna is very suitable for the recent indoor base station wireless communication services such as 3G, WiFi, WiMax, Bluetooth and LTE applications, etc. [ABSTRACT FROM AUTHOR]

ABSTRACT A wideband circularly polarized (CP) antenna with high gain is proposed. The circular polarization performance is obtained by two pairs of orthogonal bowtie dipoles with a coaxial balun feed and a broadband 90° hybrid feed network. Particularly, a design of rectangular ring with eight shorted posts is added around the bowtie dipoles, which can obtain a high gain. To further improve the gain of the novel antenna, a circular ring is placed around the rectangular ring on the same plane. With such an arrangement, the proposed antenna delivers a higher gain than that of the conventional dual-fed type CP antenna. The measured results show that the proposed antenna can achieve a measured impedance bandwidth for VSWR ≤ 1.5 of 61.5% and a 3-dB axial ratio bandwidth of 66.7%. The antenna has a stable peak CP gain better than 10.3 dBi ranging from 1.1 to 1.6 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1274-1277, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT The wideband performance of a bowtie antenna with Γ-shaped strip feed and tuning stubs is presented. Besides two folded elements connecting the patches of the bowtie dipole for a compact dimension, the Γ-shaped strip feed structure and the four tuning stubs to effectively improve the impendence matching can be used for bandwidth enhancement. A wideband impedance characteristics of about 58.6% for VSWR ≤ 1.5 ranging from 1.58-2.89 GHz is obtained and the stable peak gain of around 9 dBi, unidirectional radiation patterns and low cross-polarization over the whole operating band are also achieved. It is very suitable for the recent wireless communication services for the indoor-base station such as 3G, WiFi, WiMax, Bluetooth, and LTE/2.5 applications, and so on. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2145-2149, 2013 [ABSTRACT FROM AUTHOR]