A novel wideband unidirectional antenna composed of a planar electric dipole and a shorted patch antenna is presented. The antenna is excited by a Γ-shaped strip feed line. A wide impedance bandwidth of 43.8% (SWR≤1.5) from the frequency of 1.85 to 2.89 GHz is achieved. Stable radiation pattern with low cross- polarization, low backlobe radiation, nearly identical E-and H-plane patterns and an antenna gain of ~8dBi is found across the entire operating bandwidth.

https://www.ijmot.com/ijmot/uploaded/fJAl1POcc7.pdf

A New Wideband Unidirectional Antenna Element

Integral Equation Methods for Electromagnetic and Elastic Waves is an outgrowth of several years of work. There have been no recent books on integral equation methods. There are books written on integral equations, but either they have been around for a while, or they were written by mathematicians. Much of the knowledge in integral equation methods still resides in journal papers. With this book, important relevant knowledge for integral equations are consolidated in one place and researchers need only read the pertinent chapters in this book to gain important knowledge needed for integral equation research. Also, learning the fundamentals of linear elastic wave theory does not require a quantum leap for electromagnetic practitioners. Integral equation methods have been around for several decades, and their introduction to electromagnetics has been due to the seminal works of Richmond and Harrington in the 1960s. There was a surge in the interest in this topic in the 1980s (notably the work of Wilton and his coworkers) due to increased computing power. The interest in this area was on the wane when it was demonstrated that differential equation methods, with their sparse matrices, can solve many problems more efficiently than integral equation methods. Recently, due to the advent of fast algorithms, there has been a revival in integral equation methods in electromagnetics. Much of our work in recent years has been in fast algorithms for integral equations, which prompted our interest in integral equation methods. While previously, only tens of thousands of unknowns could be solved by integral equation methods, now, tens of millions of unknowns can be solved with fast algorithms. This has prompted new enthusiasm in integral equation methods.

Integral Equation Methods for Electromagnetic and Elastic Waves

The L-shaped probe is shown to be an attractive feed for the thick microstrip antenna (thickness around 10% of the operating wavelength). A parametric study on the rectangular patch antenna is presented. It is found that the antenna attains 36% impedance bandwidth (SWR/spl les/2) as well as gain bandwidth and about 7-dBi average gain. A two-element array fed by L-probes is also proposed. Experiments show that the array design can substantially suppress the cross polarization of the proposed antenna. Both the antennas have stable radiation patterns across the passband. Moreover, the measured resonant frequencies of the proposed antenna agree well with an existing formula and the L-probe does not have much effect on the resonant frequency.

Experimental study of a microstrip patch antenna with an L-shaped probe

A new numerical stochastic optimization algorithm, inspired from colonizing weeds, is proposed for Electromagnetic applications. This algorithm, invasive weed optimization (IWO), is described and applied to different electromagnetic problems. The linear array antenna synthesis, the standard problem used by antenna engineers, is presented as an example for the application of the IWO. Compared to the PSO, The features of the IWO are shown. As another application, the design of aperiodic thinned array antennas by optimizing the number of elements and at the same time their positions is presented. By implementing this new scenario, thinned arrays with less number of elements and lower sidelobes, compared to the results achieved by genetic algorithm (GA) for the same aperture dimensions, are obtained. Finally, the IWO is applied to a U-slot patch antenna to have the desired dual-band characteristics.

Invasive Weed Optimization and its Features in Electromagnetics

A wide operating bandwidth for a single-layer coaxially fed rectangular microstrip patch antenna can be obtained by cutting a U-shaped slot on the patch. This antenna structure has recently been found experimentally to provide impedance bandwidths of 10%-40%, even with nonair substrates. However, design rules for this antenna have not yet been presented. This paper develops principle design procedures through examination of the structure's multiple resonant frequencies as well as the radiation and impedance properties of different antenna geometries. The approximate design rules are derived by analysis of former experiments, method of moments (MoM) simulations, and measurement results. Simulations and measurements of several antennas designed using these new rules are presented and directions for further study are discussed.

Analysis and design of broad-band single-layer rectangular U-slot microstrip patch antennas

The characteristics of a rectangular microstrip antenna with an L-shaped probe are investigated. A foam layer with a thickness of around 10% of the wavelength is used as the supporting substrate. An impedance bandwidth of 35% and an average gain of 7.5 dBi can be achieved. The radiation pattern is stable across the passband.

Broadband microstrip patch antenna

A rectangular microstrip antenna with two U-shaped slots on the patch is described. Using a foam layer of thickness /spl sim/8% wavelength as the supporting substate, an impedance bandwidth of 44% is achieved. The radiation patterns are stable across the passband.

Double U-slot rectangular patch antenna

The design and measured results of a rectangular U-slot patch antenna proximity fed by an L-shaped probe are described. Using a foam layer of thickness /spl sim/7% wavelength as a supporting substrate. An impedance bandwidth of 42.7% and a gain of 6.7 dBi has been achieved. The radiation patterns obtained are stable across the passband.

L-probe proximity fed U-slot patch antenna

The derivation of a simple and numerically efficient spectral Green's-function formulation for multilayer media is presented. From this formulation, the complete set of spectral Green's functions of scalar and vector potentials for a multilayer medium for vertical and horizontal electric as well as magnetic dipoles is obtained. By this method, the spectral functions of multilayer media and their derivatives can be obtained numerically by using a closed-form formula. This will remove the necessity of obtaining the complicated spectral functions analytically. A number of numerical results are given for verification.

Y.L. Chow

Papers

Broadband microstrip patch antenna

Experimental study of a microstrip patch antenna with an L-shaped probe

Double U-slot rectangular patch antenna

L-probe proximity fed U-slot patch antenna

Spectral Green's functions for multilayer media in a convenient computational form