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In this paper, an offset reflector antenna with dual-beam and dual-polarization characteristics is developed to provide the angular diversity function for troposcatter communication system. The antenna system consists of a parabolic reflector and a dual-beam feed. For the dual-beam feed, two identical Ku-band feed elements are arranged side by side to generate two beams toward the reflector. The two beams are substantially nonoverlapping. The feed element is composed of a dielectric rod, a square waveguide, and an ortho-mode transducer. The dielectric rod is effective in reducing the beamwidth of the feed and providing more tapered illumination on the reflector in order to increase the antenna gain. Moreover, the developed antenna is able to produce two independent beams with the vertical and horizontal polarizations. The antenna was fabricated and tested with good agreement between the simulation and measurement results. The measured voltage standing wave ratios of the four feed ports are less than 1.5:1, and the beam separation angle is not more than 0.7° or about one time half-power beamwidth, and the antenna gain is higher than 45 dBi over the operating band from 14.5 to 15.35 GHz. [ABSTRACT FROM AUTHOR]

A novel wideband circularly polarized (CP) antenna is presented in this article. The proposed antenna consists of a four-leaf clover patch, four L-probes, and wideband networks. Based on the tightly coupled mechanism, the four L-probes are formed as a ring with the adjacent ones kept close for strong mutual coupling. Consequently, the proposed antenna realizes a wideband impedance matching. Meanwhile, the four-leaf clover patch is put closely inside of the ring for further improving the impedance bandwidth, which is proximity-coupled fed by the four sequential-rotation L-probes with phase of 0°, 90°, 180°, and 270°. The four L-probes are connected to the respective ports of a wideband feeding network by a two-stage impedance transforming network. The measured results indicate that the proposed design has an impedance bandwidth of 66.7% from 1.0 to 2.0 GHz for VSWR ≤ 2 and a 3-dB axial ratio bandwidth of 56.5% from 1.08 to 1.93 GHz. Furthermore, in the operating bandwidth, stable and symmetry radiation patterns and high gain are obtained. The design has a 3-dB gain bandwidth of 38% from 1.3 to 1.9 GHz with a peak gain of 8.5 dBic. [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]

A wideband circularly polarized antenna with Γ-shaped feed is presented.The proposed antenna is formed by two shorted bowtie patch antennas and two L-shaped electric dipoles. It can achieve a measured impedance bandwidth for voltage standing wave ratio (VSWR) ≤ 1.5 of 52% and a 3-dB axial ratio bandwidth of 55%. For the entire half-power beamwidth, the axial ratio can be kept below 3 dB. A prototype has been fabricated and tested, and the experimental results validate the design procedure. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:153-156, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26503 [ABSTRACT FROM AUTHOR]

A dual-resonant patch antenna applicable to active radio frequency identification (RFID) tags is designed. The designed antenna has been skillfully integrated with the active RFID tag circuit. The antenna consists of two parts. One part comprises stacked shorted patches and a ground plane. The other part is an active tag circuit mounted on the bottom of the antenna. The measurement results reveal that the antenna has the return loss less than -10 dB within the bandwidth of 42 MHz (from 911 to 953 MHz), which totally covers the 5 MHz bandwidth from 920 to 925 MHz (The band is also allowed for passive RFID) requirement for active RFID in China. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1280-1284, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26000 [ABSTRACT FROM AUTHOR]