On the electromagnetic field of a rectangular patch of uniform andlinear distributions of current in the source region

Exact analytical expressions for the magnetic vector potential and the electric and magnetic fields of a rectangular patch of uniform and linear distributions of electric current in an unbounded homogeneous medium have been given by the authors in a previous paper (see ibid., vol.37, p.1503-9, December 1989). In this paper, these expressions are utilized to investigate the nature of the electromagnetic field of such current distributions in the source region. Specifically, the singular parts and points of singularity of the various functions involved in the analytical expressions, as well as those of the field components of both current distributions, are obtained and tabulated     

Electromagnetic missile launched from a uniform current sheet ofarbitrary shape

A time-domain method, referred to as the variable transformation method, is used to study the transient radiation field from a uniform current sheet of any shape. A uniform current sheet of arbitrary shape is found to be capable of launching an electromagnetic missile (EMM) over the area equal to that of the sheet. The authors first derive the time-domain expression of the transverse electric and magnetic field strength along the axis of a circular sheet. The EMM condition is then derived in the time-domain form. It is then proven that the EMM can exist over an area equal to that of the sheet in any shape     

Far field radiated by rectangular patch microstrip antenna

Using the volume equivalence theorem, we introduce electric and polarisation current distributions for a rectangular patch microstrip antenna. These distributions are known from transmission-line-model analysis. Literal formulas are given especially to express the E-plane radiation pattern and the worst-case crosspolarisation level. Theoretical results are in good agreement with experiments.     

Electromagnetic field inside a surface current distribution

The electromagnetic field and a generalised electric Green's dyad, when the field point is inside a surface current distribution are derived. The Green's dyad is represented by the sum of the dyadic Green's function in free space and a source dyad determined by the shape of the principal area that surrounds the singularities of the Green's function.<>     

Resonance frequency of a rectangular microstrip patch

The microstrip-patch resonant frequency problem is formulated in terms of an integral equation using vector Fourier transforms. Using Galerkins's method in solving the integral equation, the resonant frequency of the microstrip patch is studied with both Chebyshev polynomials and sinusoidal functions as basis functions. In the case of the Chebyshev polynomials, the edge singularity is included, but it is not important for convergence. Furthermore, the resonant frequency of the microstrip patch is ascertained with a perturbation calculation. The results for Galerkin's method and experiments are in good agreement. The perturbation calculation agrees asymptotically with Galerkin's method. With the aim of developing a computer-aided design formula, the solutions obtained by Galerkin's method are interpolated with a three-variable polynomial     

Small rectangular patch antenna

A novel folded rectangular patch antenna is designed and measured. Compared with a conventional patch antenna with the same surface area, the resonant frequency is reduced by 37%. The cross-polarisation level is ~-20 dB     

Resonant frequency of a tunable rectangular patch antenna

The uniform transmission-line model is applied to determine the resonant frequency of a coaxial probe fed rectangular patch antenna tuned by a number of passive metallic posts suitably placed within the antenna's boundary. An approximate expression is given for the resonant frequency as a function of the post location and number, and of the other characteristic parameters of the antenna. Theoretical results are compared with available measured values.     

Long rectangular patch antenna with a single feed

Radiation characteristics of a long rectangular patch antenna excited by a single feed are investigated. The equivalent circuit of the patch including the feed line section is developed. It is found theoretically that a single feed long rectangular patch supports a leaky traveling wave along the length of the patch. The complex propagation constant of the traveling wave is estimated by solving the wave equation with impedance boundary conditions. Radiation patterns of the antenna are obtained using the principle of equivalence. Various radiation characteristics of center-fed and end-fed long patch antennas are presented     

Resonance of a rectangular microstrip patch on a uniaxial substrate

Effects of uniaxial anisotropy in the substrate on the complex resonant frequency of the microstrip patch antenna are investigated in terms of an integral equation formulation. The complex resonant frequency of the microstrip patch antenna is calculated using Galerkin's method to solve the integral equation. The sinusoidal functions that are selected as the basis functions, which show fast numerical convergence. Numerical results indicate that both the resonant frequency and the half-power bandwidth are increased due to positive uniaxial anisotropy and decreased due to negative uniaxial anisotropy     

Double U-slot rectangular patch antenna

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

Characteristics of a two-layer electromagnetically coupled rectangular patch antenna

Experimental results on the characteristics of a two-layer electromagnetically coupled rectangular patch antenna are presented. The variations of pattern shape, 3 dB beamwidth and impedance bandwidth with spacing s between the two layers are studied for s between 0 and 0.37?0. A relatively high-gain region is found for s between 0.31?0 and 0.37?0.     

Transmission-line model analysis of a lossy rectangular microstrip patch

A theoretical method, namely transmission-line model analysis, is outlined to explain the radiation conductance, the bandwidth and the efficiency of a lossy rectangular microstrip patch. We are able to express the characteristics by simple formulas and we obtain good agreement between theoretical and experimental results.     

Crosspolarisation characteristics of rectangular patch antennas

Theoretical results describing the crosspolarisation characteristics of rectangular patch antennas are presented. Of particular interest is the result that the copolarisation radiation is not sensitive to resonant frequency and substrate thickness while the crosspolarisation component increases with resonant frequency and/or substrate thickness     

A broad-band U-slot rectangular patch antenna on a microwavesubstrate

A broad-band U-slot rectangular patch antenna printed on a microwave substrate is investigated. The dielectric constant of the substrate is 2.33. The antenna is fed by a coaxial probe. The characteristics of the U-slot patch antenna are analyzed by the finite-difference time-domain (FDTD) method. Experimental results for the input impedance and radiation patterns are obtained and compared with numerical results. The maximum impedance bandwidth achieved is 27%, centered around 3.1 GHz, with good pattern characteristics     

The RCS of a rectangular microstrip patch in asubstrate-superstrate geometry

A general scattering formula is derived for an arbitrary resonant conductive body within a layered medium, which shows that the body radar cross section (RCS) is directly related to the radiation efficiency of the body. The radar cross section of a rectangular microstrip patch antenna in a lossy substrate-superstrate configuration is then investigated as a specific case. Results are presented to show the effects of loss in the substrate, a lossless superstrate, and a lossy superstrate     

Resonant frequency of a rectangular microstrip patch on severaluniaxial substrates

A full-wave analysis for determining the resonant frequency of a rectangular microstrip patch on multiple uniaxial anisotropic layers with or without an anisotropic overlay is presented. Two independent methods are used to derive the immittance matrix for the patch, from which the resonant frequency is determined. They are the Hertz vector potentials and the modified spectral domain immittance approach. Numerical results of the resonant frequency are given for several patch configurations, including cases of a patch on a single anisotropic layer, a patch on a double layer with one layer anisotropic and one layer isotropic, a suspended patch resonator with anisotropic substrate, a patch with anisotropic overlay and a patch on two anisotropic substrates with an anisotropic overlay. Changes in the resonant frequency of up to 58% are reported as n_x/n _y is changed from 1.0 (for isotropic substrates) to 2.0     

Noise considerations for a tunnel diode integrated rectangular patch antenna

The tunnel diode integrated rectangular patch antenna is investigated, with emphasis mainly on noise considerations. Noise power is calculated and is found to increase very slightly with frequency for both GaAs and Ge tunnel diode loaded patches. Noise figure and noise temperature also increase with frequency for GaAs and Ge tunnel diode loaded patches. Loading the patch with the tunnel diode increases the effective noise figure and effective noise temperature of the patch, degrading the performance of the communication system significantly.     

Radiation of a rectangular microstrip patch antenna covered with a dielectric layer

The effect of a protecting dielectric superstrate on the radiation pattern of a rectangular microstrip patch antenna is investigated theoretically. The analysis approach is based on the spectral-domain method of moments in conjunction with the stationary phase method. A new concise expression is derived for computing the radiation electric field. The validity of the solution is tested by comparing the computed results with the experimental data. At higher superstrate thicknesses, numerical results indicate that the radiation pattern drastically changes into three lobes. The resonant frequency, on the other hand, increases with the increase of the thickness of the dielectric cover.     

Analysis of stacked rectangular patch antennas with nonalignedpatches or unequal patch sizes

Using the spectral domain technique, changes in the characteristics of electromagnetically coupled stacked rectangular patch antennas due to variations in the alignment of patches and patch sizes are investigated. Some of the observations can be used in the design of these antennas in order to equalize the input impedances at the resonances, shift the resonant frequencies, broaden the bandwidth, and estimate changes in the radiation patterns. It is specifically shown that a displacement in the top patch in the direction of resonance can broaden the beamwidth in the E-plane at the upper resonance at the expense of some distortion in the radiation pattern     

Approximate expression for the resonant frequency of a rectangular patch antenna

An approximate expression is derived for the resonant frequency of a rectangular patch antenna. It shows explicitly the dependence of the resonant frequency on the characteristic parameters of the antenna. Accuracy of the expression is established by comparing the theoretical results with available measured results.