Abstract-This paper presents a circular ring antenna fed by two perpendicular probes, both of which are placed above the square reflector. The antenna is employed to radiate unidirectional beam for polarization diversity reception. A linear isolator is added to improve the isolation between the two probes. The antenna is proposed for the point-to-point communication of Wireless Local Area Network (WLAN) system according to the IEEE 802.11a standard in which the allocated frequency band ranges from 5.150 GHz to 5.825 GHz. The proposed antenna is compact and suitable for mass production. Without the dielectric material, the antenna is free of dielectric loss and capable of high power handling. The prototype antenna was fabricated and measured to verify the theoretical predictions. At the center frequency, the unidirectional pattern with the measured half-power beamwidths in two principal planes of 65 and 75 degrees is achieved. The front-to-back ratio is 31 dB, and the antenna gain is 7.42 dBi. The |S 11 | and |S 21 | are respectively −23.09 dB and −33.99 dB; the obtained bandwidth is 23.64%. Based on the aforementioned characteristics, the antenna is a potential candidate for polarization diversity of WLAN applications.

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This research presents a rectangular ring antenna excited by a circular disc monopole (CDM) mounted in front of a square reflector. The proposed antenna is designed to cover a frequency range of 2.300–5.825 GHz and thereby is suitable for WiMAX applications. Multiple parametric studies were carried out using the CST Microwave Studio simulation program. A prototype antenna was fabricated and experimented. The measurements were taken and compared with the simulation results, which indicates good agreement between both results. The prototype antenna produces an impedance bandwidth (|S11|< −10 dB) that covers the WiMAX frequency range and a constant unidirectional radiation pattern (θ=0°and∅=90°). The minimum and maximum gains are 3.7 and 8.7 dBi, respectively. The proposed antenna is of compact size and has good unidirectional radiation performance. Thus, it is very suitable for a multitude of WiMAX applications.

This paper presents the characteristics of a bent probe excited circular ring antenna above cylindrical reflector radiating circular polarization for the point to point wireless Local Area Network communication system. The proposed antenna is operated at the center frequency of 2.45 GHz. The CST software based on FIT (Finite Integral Techniques) is used as the simulation tool for investigating the antenna characteristics. The probe was shielded by dielectric rod and it is bent to obtain good impedance matching and circular polarization. The simulated results of the return loss, radiation pattern, and axial ratio are presented. The antenna has an impedance bandwidth (2:1 VSWR) of 24.93% that cover the frequency range of 2.089 -2.684 GHz. The antenna has a unidirectional pattern with maximum gain of 8.88 dBi. The average gain level is 8.18 dBi from simulation. The front-toback ratio in both E-plane and H-plane is better than 20 dB.

This paper presents an ultra-wideband (UWB) rectangular ring antenna excited by a circular disc monopole (CDM) with a conducting rod and two double ridges to radiate bidirectional pattern with constant beam direction along the entire UWB frequency range of 3.1-10.6 GHz. The conducting rod and double ridges at the upper wall of the ring are added to solve the tilted beam problem at the higher edge frequency whereas the double ridges at the lower wall are used to enhance the impedance bandwidth. The dimensions of the rectangular ring and the CDM are initially considered to achieve the bidirectional pattern with the suitable resonant frequencies and bandwidth. Then, the parameters of copper rod and two double ridges are determined by parametric study using CST Microwave Studio simulation software. The prototype antenna was fabricated, and the measured results show good agreement with the simulated ones. The obtained bandwidth of |S 11 | < −10 dB can cover the UWB frequency range as well as the bidirectional beam radiation with constant beam direction (θ = 0 • , 180 • and φ = 90 • ). The minimum and maximum measured gains are 3.1 dBi to 5.3 dBi, respectively. The proposed antenna possesses compact size with good radiation performance that can be a promising candidate for UWB applications.