Phairote Wounchoum

A TWO-SLOT ARRAY ANTENNA ON A CONCENTRIC SECTORAL CYLINDRICAL CAVITY EXCITED BY A COUPLING SLOT

A two-slot array antenna on a concentric sectoral cylindrical cavity excited by a coupling slot is investigated. The electromagnetic fields and Q factors for the first few modes of a concentric sectoral cylindrical cavity are presented. It shows that the appropriate mode for a slot array antenna on a concentric sectoral cylindrical cavity is the TM110 mode. The correlations between each mode distribution and the magnetic field distributions inside the cavity are presented. The antenna design and the parametric study of a two-slot array antenna on a concentric sectoral cylindrical cavity for a single sector are illustrated. Simulated results are validated by measurements. The results provide useful information for the design of a switched-beam slot array antenna on the concentric sectoral cylindrical cavities.

Radiation Characteristics of Two-Slot Array Antenna on a Concentric Sectoral Cylindrical Resonator Excited by a Coupling Slot

This paper presents the radiation characteristics of two-slot array antenna on a concentric sectoral cylindrical resonator excited by a coupling slot. The magnetic fields inside the sectoral cylindrical resonator for the first few modes are presented with sectoral angle of 60 degrees. It shows that the appropriate mode for a slot array antenna on a concentric sectoral cylindrical resonator is the TM110 mode. The radiation patterns of two-slot array antenna on a concentric sectoral cylindrical resonator for single sector are illustrated. The location of the coupling slot is considered to find the appropriate radiation pattern. The results provide useful information for the design of switched-beam array antenna on the concentric sectoral cylindrical resonators.

Trapezoidal dual loop antenna for radio frequency identification (RFID) system at low frequency

This paper proposes the trapezoidal dual loop antenna for radio frequency identification (RFID) system at low frequency band (125 kHz and 134.2 kHz). Typically, the conventional antenna for this system is the rectangular loop. The antenna structure is simple at the expense of limited tag orientation and shorter distance communications. The advantage of the proposed antenna is that it can be used for arbitrary orientation with the further distance. It also possesses the simple structure with low cost. The simulation is carried out by using the numerical electromagnetic code (NEC) to determine the suitable parameters. The antenna prototype is fabricated and measured to validate the antenna design and performance in RFID system.

Improvement of Communication Performance for Trapezoidal Dual Loop Antennas by Switching Techniques

This paper presents the switching techniques for trapezoidal dual loop antennas to improve the communication performance of Radio Frequency Identification (RFID) system at low frequency. The switching techniques use two sets of antennas in walk-through gate configuration in order that the RFID reader can activate two sets of antenna at different times. Both antennas were designed to yield the magnetic field covering the entire volume. The antenna prototype was fabricated and measured the percentage of volume to confirm the communication performance. The obtained percentages of volume in three principal axes are 100%. The experimental results verify the antenna capability in RFID system.

Effects of ruminal magnets in the vicinity of a bolus tag of an LF-RFID system

This paper presents effects of ruminal magnets in the vicinity of a bolus tag of an LF-RFID (low frequency-radio frequency identification) system. The study on effects of ruminal magnets to the communication for an RFID reader and a bolus tag is performed by the resonant-frequency measurement. From measurement results, it is found that effects of ruminal magnets in the vicinity of a bolus tag are strong when the ruminal magnets and the bolus tag are arranged in parallel, and the distance between the ruminal magnets and the bolus tag is small.

Characteristics of a helical array antenna radiating circularly polarized conical beam

This paper presents the characteristics of a helical array antenna radiating circularly polarized conical beam. The structure of the antenna is simple and easy to fabricate. The radiation pattern of the antenna is calculated by combining the total fields radiated from each small helical antenna on the ground plane. The effect of the finite size ground plane is taken into account and compared with one considered in case of the ground plane is infinite extent. The radiation patterns for various parameters viz., the array radius and the number of elements are demonstrated. Guidelines for the antenna design to realize the desired directivity and elevation angle are illustrated. The experiment is under investigation.

Magnetic field distributions of two-slot array antenna on a concentric Sectoral Cylindrical Resonator Excited by a Coupling Slot

In this paper, the magnetic field distribution of two-slot array antenna on a concentric sectoral cylindrical resonator excited by a coupling slot is presented. The correlations between the field distributions of the antenna and the mode-based field distributions are presented. The radiation pattern, magnetic field distribution and magnitude of S11 are investigated in the terms of the length of the sectoral resonator. It shows that the TE112 mode has degenerated to the magnitude of S11 for the circumferential slot array antenna. The results provide useful information for the design of switched-beam array antenna on the concentric sectoral cylindrical resonators.

Analysis of probe excited circular ring above reflector in outdoor WLAN systems

This paper presents the analysis of probe excited circular ring above reflector in WLAN bridge systems. The evaluation performance mainly in terms of link distance, compared probe excited circular ring above reflector and monopole antenna. The path loss used to determine service range is modelled by two-ray model. The calculation and experimental results are very useful for design and evaluation performance of WLAN bridge systems.