Supakit Kawdungta

Compact flat monopole antenna for small aircraft of VHF communication system

This paper presents the design of compact flat monopole antenna for the small aircraft of VHF communication system. It can operate along the wide frequency band without the matching circuit that make itself compact size. From the simulation results, the proposed antenna has a frequency range between 112 and 130 MHz. It yields an omnidirectional pattern with a linear polarization. The simulated gain is 1.88 dBi. The prototype antenna was fabricated and tested with the VHF aircraft communication system. It has sufficient characteristics for the VHF communication system. It is found that this antenna can be efficiently used for the small aircraft.

An Analysis of Electrically Large Planar Dipole Antenna Arrays with an Efficient Hybrid MSMM/CG Method

In this paper, an efficient hybrid method is proposed for solving electrically large planar dipole antenna arrays in free space. The hybrid method appropriately combines the multiple sweep method of moments (MSMM) and conjugate gradient (CG) method, called hybrid MSMM/CG method, yielding better convergence rate compared with the conventional MSMM and CG method. Two examples of 21× 21 uniform and 24× 24 non-uniform planar dipole antenna arrays are analyzed. Results show that the hybrid MSMM/CG method converges rapidly compared to the conventional methods. In addition, the current distributions and radiation patterns computed by using the hybrid MSMM/CG method are in excellent agreement with those obtained from the standard method of moments (MM). It is found that the hybrid MSMM/CG method is very efficient and accurate for electrically large planar dipole antenna arrays in free space.

Realization of switched-beam metamaterial-inspired microstrip antenna

This research has proposed the enhancement technique of the antenna gain by using a superstrate of metamaterial (MTM). It is deployed with a switchable beam microstrip antenna with double parasitic patches, in which two PIN diodes. Simulations and experimental were carried out for the proposed switchable beam microstrip antenna and the proposed antenna with the superstrate of MTM. The simulation and experimental results are in good agreement and it is a good impedance matching (|S11|<−10dB) along the operating frequency (2.4–2.5 GHz). The average measured gain is 7dBi with the unidirectional radiation pattern along the operating frequency. The proposed switchable antennas with and without the superstrate of MTM are operable in the 2.4–2.5GHz WLAN system and switchable in three directions of xy-plane.

An efficient analysis of the far-field radiation of an electric/magnetic Hertzian dipole embedded in electromagnetic bandgap structures of periodic lossless multilayers using the equivalent CCITL model

Abstract In this paper, the far-field radiation of a Hertzian dipole embedded in electromagnetic bandgap structures of periodic lossless multilayers is studied analytically and numerically. To simplify the analysis of this radiation problem, the equivalent transmission line (TL) model based on conjugately characteristic-impedance TLs (CCITLs) is employed to efficiently compute the far-field radiation of the Hertzian dipole due to the periodic nature of the problem, where associated reflection coefficients, which are useful in computing far fields, can be determined effectively. It is found that numerical results based on the equivalent CCITL model are in very good agreement with those obtained from a commercial electromagnetic software.

LF-RFID spiral loop antenna for conveyor belt applications

This paper presents the spiral loop antenna for low frequency radio frequency identification (LF-RFID) in conveyor belt applications. The structure of spiral loop antenna can provide the magnetic field distribution of each principal component (Hx-, Hy- and Hz-component) to enhance the communication distance in all principal directions. The overall size of antenna is 55 cm × 60 cm. The antenna was fabricated with 24 AWG copper wire and fed by BNC-connector. The numerical electromagnetics code (NEC) is employed to analyze the magnetic field distribution and communication performance in each principal component. The antenna prototype was fabricated to confirm the communication performance between reader and tag. From the measured results, the spiral loop antenna has the percentage of surface equal to 76.34%, 98.96% and 67.56% in x-, y-, and z-directions, respectively. For the measured results with the conveyor belt applications, it is found that the percentage of surface is 42.50% in x-direction, 100% in y-direction, and 95% in z-direction, respectively.

Farfield analysis of a Hertzian dipole embedded in EBG structures of multilayers terminated in a high impedance surface using the CCITL model

This paper presents the conjugately characteristic-impedance transmission lines (CCITLs) for the analysis of an electric/magnetic Hertzian dipole embedded in EBG structures of multilayers terminated in a high impedance surface. Numerical results show that the CCITL model provides accurate results. It is found that the high impedance surface can improve the directivity of Hertzian dipole embeded in EBG structures comparing to the perfect electric conductor case.

The MSMM/GA design of non-uniform planar dipole antenna arrays

In this paper, the multiple sweep method of moments (MSMM) is employed to design non-uniform planar dipole antenna arrays in free space, where the genetic algorithm (GA) is integrated with the MSMM to find optimum array parameters. The antenna design is focused on parameters of non-uniform planar dipole antenna arrays, which are the length of each element, spacing between elements, and the feeding voltage of each element. Numerical results are presented to demonstrate the accuracy and efficiency of the MSMM/GA method for non-uniform planar dipole antenna arrays in free space.

Fishing net antenna for LF-RFID reader of cuboid aquarium applications

The fishing net antenna can efficiently achieve the good magnetic field distributions in the interested directions. The NEC in conjunction with the MATLAB is employed to determine the magnetic field distribution of fishing net antenna. Both the simulated and measured results show acceptable communication performance. It is found that the measured percentages of volume of fishing net antenna at d of 20.32 cm, l of 40.64 cm and h of 60.96 cm with the glass tag in the xdirection, y-direction and z-direction are 22.22%, 35.19% and 12.22% respectively. It is obvious that the fishing net antenna can be efficiently used in the actual system.

A parasitic printed monopole antenna for a VHF mobile communication

In this paper, the parasitic printed monopole antenna is proposed for the VHF mobile communication. The parasitic monopole is added with the printed monopole to achieve a good impedance matching and desired gain. The simulated results show a good matching at the operating frequency. The obtained antenna gain is around 2 dBi with the omnidirectional radiation pattern. The prototype antenna was fabricated and tested to verify the theoretical predictions. It is apparent that this antenna can be a potential candidate for the VHF communication system.