Rangsan Wongsan

Creating a Gain Enhancement Technique for a Conical Horn Antenna by Adding a Wire Medium Structure at the Aperture

This paper proposes a technique for improving the conventional conical horn antenna for the X-band frequency using metamaterial on a wire medium structure. The main idea of this research is the application of the wire medium metamaterial to the conical horn’s aperture for the enhancement of the horn’s gain; this is done without changing the antenna’s dimensions. The results show that the wire medium structure can increase the gain of a conventional conical horn antenna from approximately 17.7 dB to 20.9 dB (an increase of approximately 3.2 dB). A prototype antenna was fabricated, and its fundamental parameters including its reflection coefficient (S 11 ), radiation patterns, and directive gain were measured. The simulated and measured results were very good. The wire medium structure of the proposed antenna improved the radiation pattern, enhanced the directivity, increased the gain, and reduced the side lobe level using a simple integrated wire medium structure.

Phase-Bandwidth Enhancement of Microstrip Patch Reflectarray with Cross Slot Loads

A reflectarray antenna composed of microstrip square patches with cross slot loads is introduced. The desired phase delay of reflectarray elements, which are duplicated the same radiating aperture as parabolic backscatters, are determined on the construction of the curvature of a shaped backscatter surface with the help of Snells law for beam forming to cover a broad area. The method of moment (MoM) and the infinite-array are applied to calculate reflection phase characteristic. Using this technique, simple two-layer reflectarray with wider phase-bandwidth and compact size is fabricated. The measured results demonstrate that the reflection phase- bandwidth at center frequency of 10 GHz is higher than conventional single-layer reflectarray.

Bandwidth improvement of band-notched printed dipole antenna for DTV signal reception

This paper presents the design and experiment of wideband using band-notched printed dipole antenna operates covering frequency band for digital television (DTV) signal reception in the 470-862 MHz. Besides this proposed antenna is required to be compact, light-weight, and easy to fabricate. The antenna is of rectangular shape of width (W) 35 mm and length (L) 223 mm, and comprises two asymmetric radiating portions of left-arm and right-arm, which are separated by step-shaped feed gap with its one open end at the center of antennas one long side edge and the other open end at about L/4 away from the center of the opposite long side edge. The results of the return loss (S11), gain and radiation patterns of the proposed antenna have been simulated by using antenna analysis software CST Microwave Studio program. It is found that the proposed antenna is accessible to bandwidth about 62.77% at frequency range 470-900 MHz. Measured maximum gains were approximately 2.43 dBi, 2.53 dBi and 3.69 dBi for 514 MHz, 650 MHz and 786 MHz band, respectively. Finally, simulation and measurement results for the design example are presented and a conclusion follows.

The effective directivity of resonator antenna using curved strip dipole

This paper presents the optimum shape of a curved strip dipole antenna for maximum directive gain, which is used for excitation source of the circularly polarized resonator antenna. The proposed antenna consists of three main components, a curved strip dipole, conductor plane, and electromagnetic band gap (EBG). A curved strip dipole is constructed of a metallic sheet and bended to be a half of annular with feed point at the center for yielding wider beamwidth. Furthermore, EBG and conductor plane are used for cavity wall which is made practical use for high gain antenna. In this study, two difference shape of a curved strip dipole antenna located on conductor plane at 45° angle are appropriated, they are begotten the circularly polarized antenna. Finally, a well shape optimization case is presented together with axial ratio, directivity, and radiation patterns.

A study of gain enhancement of horn antenna using EBG

This paper presents a study of the technique to enhance the gain of horn antenna by using Electromagnetic Band Gap (EBG) transfer the power from its aperture through EBG structures. The proposed antenna has the advantages of low profile, low cost for fabrication, and light weight. Moreover, it provides the moderately high gain. A Computer Simulation Technology (CST) software has been used to compute the reflection coefficient (S11), VSWR, radiation patterns, and gain of the antenna. The bandwidth, at S11 (-10 dB), is between 10 to 14 GHz with a gain of 24 dB at 12 GHz.

Design of a novel microwave diplexer using slit-top mushroom-like units electromagnetic band gap structure and transmission line layer

This paper presents a multi-bandpass filter using the slit-top mushroom-like on two-layer of electromagnetic band gap (EBG) and transmission line structures. The proposed EBG filter will be utilized as diplexers. The characteristics of this diplexer have been studied by using CST software that was found that it can provide the very good performance. The maximum isolation and minimum insertion loss at the Rx-port when the diplexer operates in Tx-mode are around −40.22 dB and −1.38 dB, respectively. The maximum isolation and minimum insertion loss at the Tx-port in Rx-mode is around −38.42 dB and −0.85 dB, respectively. The bandwidth of Tx-mode and Rx-mode are in the range of 3.646 to 3.715 GHz and 3.141 to 3.214 GHz. This work is the feasibility study of the diplexer design by using EBG technology which can be modified to the other desired frequency bands.

Finding capability enhancement for 360-degree DOA finder

This paper presents an increased capability of direction finding for DOA finder. The use of one and two-dimensional antenna array is compared using conventional DOA finding algorithm. The simulation results reveal that one-dimensional antenna array cannot perform accurate DOA finding for 360°. On the contrary, utilizing planar array provides incredibly satisfied results.

Low profile multi-beam former operating in wide frequency band

Recently, an outstanding wideband beamformer utilizing only space domain, not time or frequency domain, has been proposed, so called wideband spatial beamformer. The advantage of this beamformer is that it requires only attenuators or amplifiers to perform beam formation in wide frequency band as its weighting coefficients become real values. As a result tapped-delay lines, frequency filters or phase shifters are avoidable. This paper presents an extended work for the mentioned wideband spatial beamformer. The beamforming algorithm is modified in order to produce multi-beam patterns with one set of real-valued weights with the purpose of energy saving. The proposed concept is tested through simulation results to confirm beamforming capability.

Enhancement of WLAN signal strength using switched-beam single antenna

This paper reports a low cost switched-beam antenna operating at 2.45 GHz. This single octagonal-shape antenna allows eight different beam-patterns which can be controlled by shorted-circuit terminations at different edges. The prototype of proposed antenna is constructed and tested to demonstrate its beam steering capability compared with simulation results. In addition, the prototype is tested under real circumstance in existing WLAN infrastructure. The measured results reveal that signal strength can be improved using the proposed antenna over omni-directional antenna utilized in these days.

Design of a demultiplexer using slit-top mushroom-like electromagnetic band gap structures

This paper presents the three channels demultiplexer using the slit-top mushroom-like on two-layer structure of electromagnetic band gap (EBG) and transmission line. The challenge is to design an EBG structure providing variety of bandwidths of the multi-bandpass filter. The proposed structure of filter in this paper is composed of the four units of slit-top mushroom-like EBG, which are cascaded to yield the multi-bandpass characteristic. The differences of dimension and number of slit-tops truncating on the surface of mushroom-like EBG units that influence to the resonant frequency and bandwidth of filter have been shown and compared to the conventional mushroom-like EBG unit. Afterwards, the appropriate slit-top on the classical mushroom-like patches of EBG structure has been considered for the proposed multi-bandpass filter and diplexer. This work is the feasibility study of the multi-bandpass filter and the diplexer design by using EBG technology which can be modified to the microwave demultiplexer. Finally, the simulated and measured results for transmission characteristics, S21, are investigated to be in good agreement.