Prayoot Akkaraekthalin

A Rhombic Patch Monopole Antenna with Modified Minkowski Fractal Geometry for UMTS, WLAN, and Mobile WiMAX Application

This paper presents a rhombic patch monopole antenna applied with a technique of fractal geometry. The antenna has multiband operation in which the generator model, which is an initial model to create a fractal rhombic patch monopole, is inserted at each center side of a rhombic patch monopole antenna. Especially, a modified ground plane has been employed to improve input impedance bandwidth and high frequency radiation performance. The proposed antenna is designed and implemented to effectively support personal communication system (PCS 1.85–1.99 GHz), universal mobile telecommunication system (UMTS 1.92–2.17GHz), wireless local area network (WLAN), which usually operate in the 2.4 GHz (2.4–2.484 GHz) and 5.2/5.8 GHz (5.15–5.35 GHz/5.725–5.825GHz) bands, mobile worldwide interoperability for microwave access (Mobile WiMAX), and WiMAX, which operate in the 2.3/2.5 GHz (2.305– 2.360 GHz/2.5–2.69 GHz) and 5.5 GHz (5.25–5.85 GHz) bands. The radiation patterns of the proposed antennas are similar to an omnidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement. Corresponding author: C. Mahatthanajatuphat (cmp@kmutnb.ac.th). 58 Mahatthanajatuphat et al.

A BIDIRECTIONAL MULTIBAND ANTENNA WITH MODIFIED FRACTAL SLOT FED BY CPW

This paper presents a multiband slot antenna with modifying fractal geometry fed by coplanar waveguide (CPW) transmission line. The presented antenna has been designed by modifying an inner fractal patch of the antenna to operate at multiple resonant frequencies, which efiectively supports the digital communication system (DCS 1.71{1.88GHz), worldwide interoperability for microwave access (WiMAX 3.30{3.80GHz), IMT advanced system or forth generation mobile communication system (3.40{4.2GHz), and wireless local area network (WLAN 5.15{ 5.35GHz). Manifestly, it has been found that the radiation patterns of the presented antenna are still similarly to the bidirectional radiation pattern at all operating frequencies. The properties of the antennas, for instance, return losses, radiation patterns and gain are determined via numerical simulation and measurement.

Simultaneous gain and bandwidths enhancement of a single-feed circularly polarized microstrip patch antenna using a metamaterial reflective surface

This paper proposes a metamaterial re∞ective surface (MRS) as a superstrate for a single-feed circularly polarized microstrip patch antenna (SFCP-MPA). It illustrates a simultaneous enhancement on antenna gain, impedance bandwidth (ZBW) and axial-ratio bandwidth (ARBW) by adding the MRS atop the SFCP- MPA. The MRS can enhance the ZBW and ARBW by 3.5 and 9.9 times, respectively, compared to the circularly polarized patch source. Moreover, the gain of the CP-MPA with the MRS is 7dB higher than that of the conventional CP-MPA. The small spacing between the MRS and patch source is another merit in the present design, which is as low as ‚-/16, as it results in a low-proflle antenna design that well suits modern wireless communications.

Signal-to-interference ratio improvement by using a phased array antenna of switched-beam elements

A phased array antenna of switched-beam elements is proposed to improve the signal-to-interference ratio (SIR). By using 1-bit phase shifters, the main beam of the array is switched to desired signal direction, and with the switched-beam patch antenna elements the null patterns are changeable. The results of radiation patterns show that the interference suppression can be improved. Moreover, the SIR measurement is also set up in multipath environment to ensure the array performance. It is found that the SIR is significantly affected by the multipath environment; however, the SIR improvement of more than 10 dB can be obtained by changing the null patterns.

A Broadband CPW-fed Equilateral Hexagonal Slot Antenna

This paper presents design and implementation of a coplanar waveguide (CPW)-fed equilateral hexagonal slot antenna. The simulation of the antenna has been done by using IE3D program. The transmission line and ground-plane have been designed to be on the same plane with the antenna slot to be applicable for wideband operation. It is found that the proposed antenna is accessible to bandwidth about 55.39%, a very large bandwidth comparing with conventional microstrip antennas, which mostly provide 1-5 % bandwidth. The proposed antenna can be used for many wireless systems such as GSM1800, GSM1900, IMT-2000 and WLAN

Bandpass Filters using T-shape Stepped Impedance Resonators for Wide Harmonics Suppression and their Application for a Diplexer

In this paper, the T-shape stepped impedance resonators are adopted for the design of microstrip bandpass filters for wide harmonics suppression. The proposed filters are operated at the center frequency of 2.44 GHz and 5.20 GHz, respectively. These bandpass filters have been also applied for a high performance diplexer. The insertion losses at the center frequencies of 2.44 and 5.20 GHz are 1.23 and 1.18, respectively. The applicable return losses for both frequency bands and a wide stopband better than 17 dB up to 20 GHz have been obtained.

A COMPACT ULTRAWIDEBAND MONOPOLE ANTENNA WITH 5.5 GHZ NOTCHED BAND

This paper proposes a compact ultrawideband monopole antenna fed by CPW with a 5.5GHz notched band of WLAN/WiMAX systems. The antenna input section is designed by using a gradual curvature central line and ground planes for ultrawideband achievement. In order to reject the unwanted frequency of the existing WLAN/WiMAX band, the C-shaped slit with perimeter length of a half wavelength at center frequency of 5.5GHz has been embedded into the monopole patch. The designed antenna is completely implemented and measured for impedance bandwidth covering UWB range and stably performs omnidirectional pattern in xz plane from 3.1 to 10GHz. The proposed antenna could potentially minimize frequency interference in the WLAN/WiMAX bands.

A compact ultrawideband monopole antenna with tapered CPW Feed and slot stubs

This paper presents a compact ultrawideband monopole antenna with tapered CPW feed and slot stubs. The proposed antenna is not only very small but also easy to fabricate. Both element feed and ground planes have been designed to be gradual curvatures for achievement of ultrawide impedance bandwidth. The impedance matching has been also improved by inserting two slot stubs at the central feed line. The results show the impedance bandwidth from 2.85 to over 15 GHz and the pattern bandwidth from 3.1 to 9 GHz. The linear phase and small variation of group delay time lower than ±6 nanoseconds have been also obtained. Therefore, this antenna is a good candidate for many UWB applications.

Unidirectional CPW-fed slot antenna using metasurface

A unidirectional CPW-fed slot antenna with metasurface is proposed. Instead of using a conducting reflector, a metasurface as a superstrate is applied to modify the radiation pattern and enhance the antenna gain. The simulation and measurement results confirm that the antenna with metasurface can enhance on broadside gain of 6.5 dB and front-to-back ratio of 10 dB. The overall thickness of the proposed antenna is only 8.4 mm, which corresponds to λ0/15 at 2.45 GHz. Good agreement between measured and computed results is achieved.

A Double Square Loop Antenna with Modified Minkowski Fractal Geometry for Multiband Operation

A double square loop antenna with fractal geometry that supports for multiband operation is proposed. The antenna has multiband operation in that the generator model, which is an initial model to create a fractal loop antenna to operate at the first and second resonant frequencies, is inserted at each center side of a big square loop antenna. It also has a small square loop to operate at the third resonant frequency. The proposed antenna is implemented and shown to effectively support the global system for mobile communication (880-960 MHz), digital communication system (1710-1880MHz), personal communication system (1850-1990 MHz), universal mobile telecommunication system (1920-2170 MHz), and wireless local area network (2400-2483 MHz) bands. The radiation patterns of the proposed antenna are still similar to a bidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement.