Mutual coupling between metal strip antennas on finite size,electrically thick dielectric substrates

An analysis of the mutual coupling between metal strip antennas which are contiguous with the ends of finite-size, electrically thick dielectric substrates is outlined. Such antennas have been proposed as useful monolithic microwave integrated circuit antennas for millimeter-wavelength applications. The analysis presented was verified experimentally, and the results are applied to three-element arrays of metal strip folded dipoles with coplanar strip feed lines. The effect of the electrically thick, finite-size dielectric substrates on the mutual coupling between elements of the arrays is described     

Impedances of Offset Parallel-Coupled Strip Transmission Lines

An offset parallel-coupled strip configuration is described, in which the mechanical parameters are strip width, strip offset, and ratio of strip spacing to ground-plane spacing. The electrical parameters are dielectric constant, characteristic impedance, even and odd mode impedance. The configuration is analyzed by conformal rnapping techniques. Explicit design equations are derived in which the mechanical parameters are expressed in terms of the electrical parameters. Illustrative results are presented, and the limitations on coupling strength, characteristic impedance, and strip configuration are discussed.     

Numerical modeling of ultrawide-band dielectric horn antennas using FDTD

A detailed characterization of the input impedance of ultrawide-band (UWB) dielectric horn antennas is presented using the finite-difference time-domain (FDTD) technique. The FDTD model is first validated by computing the characteristic impedance of two conical plate transmission lines (including planar bow-tie antennas) and comparing the results to analytical solutions. The FDTD model is next used to calculate the surge impedance of dielectric horn antennas using the conical plates as launchers. Design curves of the surge impedance for different choices of geometries and dielectric loadings are provided. The modeled antennas are particularly attractive for applications such as UWB ground penetrating radars (GPR) applications.     

Simple and Accurate Analytical Model of Planar Grids and High-Impedance Surfaces Comprising Metal Strips or Patches

Simple analytical formulas are introduced for the grid impedance of electrically dense arrays of square patches and for the surface impedance of high-impedance surfaces based on the dense arrays of metal strips or square patches over ground planes. Emphasis is on the oblique-incidence excitation. The approach is based on the known analytical models for strip grids combined with the approximate Babinet principle for planar grids located at a dielectric interface. Analytical expressions for the surface impedance and reflection coefficient resulting from our analysis are thoroughly verified by full-wave simulations and compared with available data in open literature for particular cases. The results can be used in the design of various antennas and microwave or millimeter wave devices which use artificial impedance surfaces and artificial magnetic conductors (reflect-array antennas, tunable phase shifters, etc.), as well as for the derivation of accurate higher-order impedance boundary conditions for artificial (high-) impedance surfaces. As an example, the propagation properties of surface waves along the high-impedance surfaces are studied.     

On antenna impedances in a cold plasma with a perpendicular static magnetic field

A flat strip antenna is embedded in a magnetoionic medium with its longitudinal axis perpendicular to the static magnetic field. The antenna characteristics differ for antennas oriented with their surfaces parallel and perpendicular to the static magnetic field. In the former case there are no resistance peaks for frequencies near the plasma frequency and the reactance of a short antenna is capacitive for low frequencies. For frequencies near the gyrofrequency the antennas are electrically longer for the parallel orientation of their surfaces. The accuracy of the solutions is illustrated by computing the tangential electric surface fields that are excited by the approximate current distributions used in the impedance computations.     

Wire and strip conductors over a dielectric-coated conducting ordielectric half-space

The complex wavenumber and characteristic impedance are determined for a wire or flat strip over a dielectric-coated half-space that can be a conductor or a dielectric with large permittivity. Elevated microstrip is an example of the configuration. The properties of the wire as an antenna or transmission lines are determined from those of the insulated antenna with a two-layer eccentric insulation. The theory is extended to the strip conductor with the help of a comparison of the tubular and strip conductors over a perfectly conducting half-space     

Design of broad-band and dual-band antennas comprised of series-fedprinted-strip dipole pairs

The design of antennas consisting of two strip dipoles the arms of which are printed on opposite sides of an electrically thin dielectric substrate and connected through a parallel stripline is presented. The antennas are designed to have broad-band or dual-band capability suitable for application in base stations of wireless communication systems. An important advantage of these antennas is their simple structure, allowing them to be readily manufactured as printed circuits. Broad-band antennas with bandwidths greater than 30% for VSWR ⩽1.5 operating near 2.0 GHz and dual-frequency antennas operating at 0.9 GHz/1.5 GHz and 0.9 GHz/1.8 GHz bands are presented     

Impedance matching of tapered slot antenna using a dielectrictransformer

A new impedance matching technique for tapered slot antennas using a dielectric transformer is presented. The technique is demonstrated by measuring the input impedance, VSWR and the gain of a Vivaldi antenna (VA). Measured results at Ka-band frequencies are presented and discussed     

Broadband stacked dielectric resonator antennas

The input impedance of stacked cylindrical dielectric resonator antennas is investigated experimentally. The dielectric resonators are made of different materials. The bandwidth of 25% has been observed for a standing wave ratio better than 2.<>     

Electromagnetic Radiation by Antennas of Arbitrary Shape in a Layered Spherical Media

A unified method of moments model is developed for the analysis of arbitrarily shaped antennas that are radiating next to a multilayered dielectric sphere. The curvilinear Rao-Wilton-Glisson triangular basis functions and dyadic Green's functions have been used in the model. Antennas of various geometries including spherical, circular and rectangular microstrip antennas as well as hemispherical dielectric resonators have been modeled. Input impedance and radiation pattern results are presented and shown to be in good agreement with published data.      

Moment method analysis of infinite stripline-fed tapered slotantenna arrays with a ground plane

A full-wave method of moments solution for infinite arrays of stripline-fed tapered slot antennas is described. The formulation of the problem is sufficiently general to permit performance evaluation of most of the geometries that have been proposed for stripline-fed antennas as well as of several other types of array antennas. Computed results for some well-known antenna arrays are presented to demonstrate the validity and accuracy of the method. Excellent agreement with published results has been obtained for scattering from corrugated surfaces and grounded dielectric slabs and for the input impedance of dipole and monopole arrays. Catastrophic effects such as scan blindness are accurately predicted. A sample result showing the measured and computed input impedance of a stripline-fed tapered slot antenna array is also presented     

ANSERLIN. a broad-band, low-profile, circularly polarized antenna

A technique is presented for improving the performance of low-profile, circularly polarized (CP) radiating-line antennas. The essential elements of the technique pertain to establishing a single traveling wave on an annular sector of conducting strip that is positioned parallel and close to a large conducting surface. The antenna is named the annular sector, radiating-line (ANSERLIN) antenna. Using this technique, the impedance bandwidth becomes so large that it no longer has any bearing on the operating bandwidth. Instead, the pattern shape and axial ratio become the factors that limit the bandwidth. Both senses of circular polarization can be transmitted or received from the same structure. Experimental results for two-port ANSERLIN antennas are presented. The method of exciting a traveling wave on the annular sector is discussed. Design parameters are given for an antenna that will produce a broadside axial ratio that is less than 0.5 dB at a specified frequency     

Mutual impedance of hemispherical dielectric resonator antennas

The mutual coupling between two hemispherical dielectric resonator antennas is studied analytically. The radiation fields of the antennas are derived rigorously from a Green's function. The mutual impedance is then determined from a reaction formula. Comparison between theory and experiment is presented     

An integral equation and its application to spiral antennas onsemi-infinite dielectric materials

This paper presents an integral equation that can handle wire antennas on a semi-infinite dielectric material. The integral equation is reduced to a set of linear equations by the method of moments. For efficiency, the impedance matrix element Z_m,n is divided into two parts on the basis of weighted Green's function extractions. The far-zone radiation field, which is formulated using the stationary phase method, is also described. After the validity of the presented numerical techniques is checked using a bow-tie antenna, a spiral antenna is analyzed. The current distribution, radiation pattern, axial ratio, power gain, and input impedance are discussed. It is found that the radiation field inside a dielectric material is circularly polarized. As the relative permittivity of the dielectric material increases, the angle coverage over which the axial ratio is less than 3 dB becomes narrower     

Analysis of finite-phased arrays of aperture-coupled stackedmicrostrip antennas

Analytical results for finite-phased arrays of aperture-coupled stacked microstrip antennas are presented. In order to evaluate the characteristics of aperture-coupled microstrip antennas in a finite array and derive the moment-method solutions for the unknown current distributions on the patches and slots, the reciprocity theorem and the spectral domain Green's functions for a dielectric slab are used. Various sized arrays are considered and compared with solutions for an infinite array. Numerical results are presented to illustrate the input impedance, mutual coupling, active reflection coefficient versus scan angle, radiation efficiency, and active-element gain patterns     

A general analysis of propagation along multiple-layersuperconducting stripline and microstrip transmission lines

A rigorous spectral-domain formulation for a superconducting stripline or microstrip transmission line with a multiple-layer dielectric substrate is presented. The formulation models the strip conductor as a surface current with an equivalent surface impedance, where the surface impedance is approximated in closed form when the strip is either much thinner or much thicker than a penetration depth. In either case the surface impedance is related to the complex conductivity of the material, which is calculated from a two-fluid model. Results are presented to show the slow-wave propagation and attenuation along both microstrip and stripline packages in a realistic multiple-layer configuration, which accounts for the field penetration into the superconducting ground planes     

Characteristic Impedance and Phase Velocity of a Dielectric-Supported Air Strip Transmission Line with Side Walls

The characteristic impedance and phase velocity of a dielectric-supported air strip transmission line with side walls and with center conductors having zero thickness have been obtained by means of the variational method. Green's functions are used for setting up the variational expression. Using a 22-term expansion for the charge distribution on the center conductors, the Rayleigh-Ritz method is then applied in the calculation of the characteristic impedance and phase velocity of the strip transmission line. Design curves are presented and a correction factor is derived that can be applied when the thickness of the center conductors is not zero. The design curves are quite general and apply equally well to any isotropic dielectric material that is used as a support, regardless of its dielectric constant. The experimental data presented verifies the theoretical results.     

Computation of the Characteristics of Coplanar-Type Strip Lines by the Relaxation Method (Short Papers)

The characteristics of new strip lines (i.e., a single strip conductor and a two symmetrical strip-conductor coplanar-type strip line, which consist of single- or two-center strip conductors and ground plates on a dielectric substrate and outer ground conductor) are calculated by the relaxation method. The effect of the outer ground conductor on these lines is analyzed, and the characteristic impedance and velocity ratio are determined. The characteristic impedance is determined experimentally, and the maximum values of the discrepancies compared with the calculated values of each of the lines are 2.0-3.0 percent.     

The application of the point matching method to the analysis ofmicrostrip lines with finite metallization thickness

The characteristics of a shielded microstrip line with finite metallization thickness are calculated using the point matching method (PMM). The advantage in this case is that the method does not depend on a special geometry of the strip metallization. The approach used is based on satisfying the boundary conditions at discrete boundary points. Numerical results are presented to assert the validity of this approach in cases of large values of strip width-to-thickness ratio. It is found that an increase in the strip thickness is always associated with difficulties in convergence. The examples presented call attention to the necessity of proving the validity of the obtained solutions by other criteria. This is because good convergence behavior of the effective dielectric constant does not always guarantee the correct characteristic impedance or field distribution. In particular, the field distribution is considered as a reliable check for the numerical results     

On the modeling of metal strip antennas contiguous with the edge ofelectrically thick finite size dielectric substrates

A solution to the problem of radiation by a narrow metal strip antenna contiguous with the edge of a dielectric substrate is presented where the substrate has parameters such that its electrical thickness is appreciable. Such an antenna may be useful at millimeter wavelengths as an integrated phased array element forming a part of a monolithic microwave integrated circuit (MMIC). A suitable geometry for this application is illustrated and an efficient computational procedure developed. Comparisons with experimental results for the input impedance and far-field radiation patterns show excellent agreement. The influence of the dielectric substrate on the performance of an antenna designed to operate at approximately 60 GHz is discussed. Two examples, the first involving the analysis of a coplanar strip transmission line fed antenna and the second involving impedance matching and control of cross-polarized radiation using a folded strip dipole, are given to illustrate practical applications of the analytical method to design problems