Monai Krairiksh

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.

Tri-Band Wilkinson Power Divider Using a Three-Section Transmission-Line Transformer

The analysis and design of a triple-band equal-split Wilkinson power divider are described. The circuit proposed is well matched and isolated at three arbitrary frequencies. The design procedure for the three-section transmission-line transformer based equal-split Wilkinson power divider derived from the ideal transmission-line model is provided. Simulated and experimental results in microstrip technology are presented to verify the idea and the derived equations

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.

TWO-PROBE EXCITED CIRCULAR RING ANTENNA FOR MIMO APPLICATION

This paper presents the analysis and design of a two-probe excited circular ring antenna. The analysis is conducted by using induced emf method and transmission line model. The design process is to choose a suitable radius of the ring for a single probe antenna. Then, the suitable probe length and ring length are determined for the two- probe antenna. Finally, isolation between the two probes is enhanced by insertion of an inductor coil between the probes. The operational characteristics of the prototype antenna at the frequency of 5.2GHz are measured and compared with calculation results. It is evident that these results are in good agreement. The antenna achieved isolation in excess of 20dB and VSWR less than 2 : 1 over the desired bandwidth and a bidirectional radiation pattern with 4dBi gain. This antenna is suitable for Multiple-Input Multiple-Output (MIMO) system covering a long and narrow environment.

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.

Keynote speakers: Wireless power transfer: From long-distance transmission to short-range charging

Since Nikola Tesla proposed the Wardenclyfee Tower in 1889 for the wireless power transmission to date, it has been over a century. The idea was later picked up and implemented continuously in the last half a century. Recently in 2007, MIT research group picked up the old concept and implemented for potential applications into telecommunications. This talk will address briefly the state of-the-art research and development progresses in the wireless power transmission technology and also potential applications. The talk is categorized into two aspects, that is, (a) the long-distance and high-power wireless energy transmission and (b) the short-range and low-power wireless energy transmission. For the long-distance high-power transmission, the talk will cover atmospheric effects, high-power microwave generation, transmitting antennas, EMC/EMI effects on radio frequency wireless system, rectennas, and biological effects on human being and animals. For the short-range wireless power transmission, the review will touch inductive couple effects and their applications onto power-grid systems, wireless power charging systems, mine-tunnel power charge system, and medical applications. The talk will, of course, discuss on advantages and short-comings of these proposals.

A Four-Beam Pattern Reconfigurable Yagi-Uda Antenna

This communication presents a pattern reconfigurable antenna which is based on the Yagi-Uda configuration that can change the radiation beam into four directions. The function of the parasitic elements can be altered between a director and a reflector with PIN diodes while the driven element can be altered between two perpendicular directions with RF switches. To be able to use this proposed antenna on an electric conductor, such as on the vehicle rooftop, the antenna is thus mounted on electromagnetic band gap (EBG) structure which serves as a magnetic conductor. The gain is approximately 5 dBi and the field trial exhibited the diversity gain of 17 dB over the fixed beam antenna. As a result, the proposed antenna possesses high potential for further development into a TV signal reception on moving vehicles.

A flat four-beam compact phased array antenna

This paper presents a flat four-beam compact phased array antenna. The low-cost and compact phased array antenna is designed using a circular array of four circular microstrip antennas made of low-cost material and four 1-bit phase shifters. The main beam of the antenna can be switched in four directions with the gain of about 4 dBi in each main-beam direction. More than 90/spl deg/ half-power beamwidth and over 10 dB F/B ratio are obtained. In addition, the diversity performance is considered and the diversity performance of this antenna can be provided with the envelope correlation about 0.6.

DETERMINATION OF DIELECTRIC PROPERTY OF CONSTRUCTION MATERIAL PRODUCTS USING A NOVEL RFID SENSOR

This paper presents a concept, by which radio frequency (RF) tags are employed as remotely read dielectric-property sensors to determine qualities of some construction material products (CMPs); e.g., light weight concrete (LWC), mortar specimens and concrete. Using the dependency of the read range of the passive RF identiflcation (RFID) sensor system on the electromagnetic properties of CMPs near or in contact with RFID tags, the qualities of CMPs can be determined through their estimated dielectric properties. Theoretical formulation is provided, and numerical simulations are performed for optimal design of passive RFID tag antennas suitable for RFID sensors and for read-range calculations. In addition, a series of measurements is performed to measure read ranges of the passive RFID sensor system for an LWC as an example of CMPs, and these measured read ranges will be processed appropriately to inversely determine the dielectric constant of the LWC under test, which in turn provides information on its qualities. It is found that the novel RFID sensor can be employed to determine the dielectric properties of the LWC under test with reasonable accuracy.

A Continuous Fluidized Bed Microwave Paddy Drying System Using Applicators with Perpendicular Slots on a Concentric Cylindrical Cavity

This article presents a continuous fluidized bed microwave drying system that provided a higher drying capacity than that provided by comparable conventional hot air drying systems. Its applicator consists of perpendicular slots over a concentric cylindrical cavity that is excited by perpendicular waveguides. The paddy to be dried was dropped vertically into the center of the applicator while hot air at 60°C, heated by magnetron ventilation, was injected from the opposite direction. Statistical data on the temperature distribution of the paddy, which scattered over the whole volume of the applicator, were collected and analyzed together with the probability of its orientation, position, and density. A suitable system was proposed, constructed, and tested. It provided good quality dried paddy, similar to that from a fluidized bed drying system. The systems maximum leakage power of 4.8 mW/cm2 was well within the safety standard. With only 5.2 kJ of energy consumption, this system reduced the moisture content of a large quantity of paddy from 24 to 14% (wb) with a capacity of 3.1 kg/h. The energy cost for drying was US