Shi-Gang Zhou

Modified Two-Element Yagi-Uda Antenna with Tunable Beams

A modifled two-element Yagi-Uda antenna with tunable beams in the H-plane (including four signiflcant beams: forward, backward, omni-directional, and bi-directional beams) is presented. These tunable beams are achieved by simply adjusting the short-circuit position of the transmission line connected to the parasitic element. The principle of operation is investigated by examining the current relations between the driven and parasitic elements. Measured results of a fabricated prototype are presented and discussed.

A Novel Dual Band-Notched Ultra-Wideband Antenna

A novel dual band-notched monopole ultra-wideband (UWB) antenna which is composed of a radiation element, a ground patch and several tuning stubs is proposed. The antenna with compact size of 20 mm × 31.5 mm works in the band of 3.1 ∼ 10.6 GHz with voltage standing wave ratio (VSWR) below 2, except the bands of 3.3–3.8 GHz for WIMAX and 5.1–5.8 GHz for WLAN. By changing the lengths of the tuning stubs, the central frequencies of the dual notched bands can be adjusted easily, which is discussed in the paper. The results are given in this paper and show a acceptable agreement between the simulation and measurement.

A New Ultra-Wideband Microstrip-Line Fed Antenna with 3.5/5.5ghz Dual Band-Notch Function

A novel and compact planar ultra-wideband wide-slot antenna with dual band-notched function is proposed. The method of creating dual band-notch function is unique from traditional ones. By embedding a U-shaped parasitic strip and a pair of T-shaped stubs in the wide slot, dual bandstops around 3.5GHz and 5.5GHz can be obtained. The measured results demonstrate that the proposed antenna, with a compact dimension of 20 × 32.5mm, has a large bandwidth over the frequency band from 2.5 to 11.7GHz with voltage standing wave ratio (VSWR) less than 2, except the bandwidths of 3.3 ∼ 3.7GHz for WIMAX and 5 ∼ 6GHz for WLAN. In addition, the radiation pattern has an excellent omni-directional characteristic in H-plane and a typical monopole-like pattern in E-plane.

A New Fitness Function for Optimizing the Matching Network of Broadband Antennas by Genetic Algorithm

A new fitness function for the genetic optimization of broadband antennas is proposed. Compared with the previous fitness functions, the one presented in this paper takes not only voltage standing wave ratio and gain but also frequency into consideration. In practical communication system, higher gain needed in the high frequency band of the antenna, so it is more suitable. An impedance matching network for an antenna in 30 MHz to 88 MHz is studied lastly.

A novel dual band-notched ultra-wideband slot antenna

A novel ultra-wideband (UWB) design of a single-layer coplanar waveguide (CPW) fed monopole antenna with dual frequency band-notched function is presented. By attaching a tuning stub into the radiating ring and etching two L-slots in the ground plane of the CPW, dual band-notched characteristics are achieved. Details of the antenna design are presented and the measured results of voltage standing wave ratio (VSWR), radiation patterns and gain are given. Experimental results demonstrate that the proposed antenna has a super-wideband from 2.5 to 12 GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stopbands of 3.3-4.2 GHz and 5.2-6.0 GHz.

A Wideband and Dual Frequency Three-Dimensional Transition-Fed Circular Patch Antenna for Indoor Base Station Application

The design and performance of a stacked patch antenna for wideband and dual-frequency operation are presented in this paper. The proposed antenna consists of a three dimensional (3D) circular transition-fed patch that is excited by a coaxial probe. By introducing a regular patch and a ring patch above the 3D circular transition-fed patch, good input impedance matching has been achieved over two frequency bands. The lower band possesses an impedance bandwidth (VSWR < 2) of 22.8% (0.775 to 0.975GHz) and a peak gain of 5.2dBi, while the upper band has an impedance bandwidth (VSWR < 2) of 65.8% (1.425 to 2.825GHz) and a peak gain of 7.4dBi. Other than the wideband and dual-band operation features, this antenna also has a beam tilted downward with a broadside beam pattern on the horizontal plane. Therefore, this antenna is very suitable for the indoor base station that is required to service several wireless communication systems, included CDMA800, GSM900, 3G, PCS, UMTS, BLUETOOTH and WLAN, by a single antenna.

Method for Broadening the Beamwidths of Crossed Dipole for Wideband Marine GPS Applications

In this paper, a method to broaden the beamwidths of a crossed dipole antenna is proposed. By introducing four parasitic strips around the crossed dipole antenna, the beamwidths of the crossed dipole antenna in the vertical plane are broadened efiectively, making the patterns uniform over a wide frequency band. An L-band prototype, operating

OPTIMIZATION OF THREE-DIMENTIONAL (3-D) GROUND STRUCTURE FOR IMPROVED CIRCULARLY POLARIZED MICROSTRIP ANTENNA BEAMWIDTH

A novel circularly polarised (CP), single-fed widebeam microstrip antenna is presented. The antenna consists of a corner- truncated square patch and a three dimensional circular ground structure. Simulated and measured results show that, owing to the ground structure, the 3dB beamwidth of the CP radiation can reach more than 165 - , which is about 85 - greater than that of a corresponding regular microstrip antenna. It is also shown that experimental results were in good agreement with the simulated performance. Details of the proposed 3-D circular ground structure are described, and the efiects of various dimensions of the proposed ground structure on the beamwidth enhancement of CP radiation are studied.

Compact Wideband Inverted Cone Combined Spherical Segment Antenna

An antenna comprising an inverted cone, a spherical segment and three shorting plates above a circle ground is proposed. The presented antenna provides broadband characteristics and omnidirectional radiation patterns over the whole bandwidth. Simulations and experiments demonstrate that this structure exhibits a 7.25:1 impedance bandwidth (824–5800 MHz) with VSWR below 2:1 and very good radiation patterns. Owing to its low profile and wide impedance bandwidth and good radiation patterns properties, this antenna is suited for indoor wireless base station antennas mounted on the ceiling.

Wideband and Omni-Directional Antenna for DVB/GSM Applications

A novel planar monopole antenna for the digital video broadcasting (DVB) signal reception in the UHF band (470–862 MHz) and mobile communications in the GSM850/900 band (824–960 MHz) is presented. The proposed antenna consists of a modified planar monopole and a rectangular ground plane with two planar sleeves. By adjusting the sleeves, a wide bandwidth can be obtained easily. The influence of various parameters on antenna characteristics has been investigated. Simulated and measured results show a wide bandwidth of 735 MHz (465 MHz–1.20 GHz) with the VSWR less than 2.0 and omni-directional radiation properties. Details of the proposed antenna design and experimental results of the constructed prototypes are presented