Showing papers on "Patch antenna published in 1968"

Variational Method for the Analysis of Microstrip Lines

Abstract: This paper reports a method for computing the line capacitance of a microstrip line based on the application of Fourier transform and variational techniques. The characteristic impedance, guide wavelength, and the surface potential distribution in the microstrip line are obtained for a range of structure parameters and the dielectric constant. The results calculated from the expressions developed in the paper are compared with the theoretical results presently available in the literature and good agreement is found. Comparison with available experimental results is also made where feasible. Possible applications and limitations of the method are discussed.

Variational Method for the Analysis of Microstrip-Like Transmission Lines

Abstract: A theoretical method is presented by which microstrip-like transmission lines can be analyzed. These transmission lines are characterized by conducting strips, large ground planes, multi-dielectric-layer insulation, and planar geometry. The method is essentially based on a variational calculation of the line capacitance in the Fourier-transformed domain and on the charge density distribution as a trial function. A shielded double-layer microstrip line is analyzed by this method. Derived formulas for this structure are also applicable to simpler structures: a double-layer microstrip line, a shielded microstrip line, and a microstrip line. The calculated values of the line capacitance and the guide wavelength are compared with the measured values where possible. Oxide-layer effects on a silicon microstrip line and shielding effects on a sapphire microstrip line are also discussed based on this theory. The limitations and possible applications of this method are described.

On the electrically thick monopole: Part I--Theoretical solution

Abstract: A new integral equation is formulated for the current distribution of an electrically thick, cylindrical antenna which is driven by a voltage across a finite gap on an infinitely large ground plane. Compared to the conventional integral equation of Hallen, this equation has an additional source term which can be expressed in terms of both the radius of the antenna and the width of the gap. A numerical solution of the integral equation has also been obtained by a so-called "approximate product-integration technique" and the results have been compared with the experimental data of a monopole antenna driven by a coaxial transmission line over an infinitely large ground plane. When the circumference of the antenna is comparable to a free-space wavelength, the experiment verifies that the theoretical model with finite gap excitation describes the experimental situation more properly than either the conventional model of a delta-function excitation on both outside and inside surfaces of the antenna, or the King-Wu model of a delta-fanction excitation only on the outside surface.

The finite tubular antenna in a warm plasma

Abstract: A cylindrical dipole antenna, immersed in a warm homogeneous and isotropic plasma and driven at the center by a delta-function voltage generator, is treated as a boundary value problem. The current on the antenna is determined and found to consist of two parts: a slowly varying component that varies like the current on an antenna in a cold medium, and an oscillating component. The spatial periodicity of the oscillatory component is of the same order as that of the surface waves launched on an infinite tube containing and surrounded by warm plasma. If the antenna is driven well above the plasma frequency, the oscillatory portion of the current is negligible, while if it is driven at slightly above the plasma frequency, the oscillatory portion of current is dominant. It is found that a radiation resistance calculation made by using a current distribution valid only for an antenna in a cold environment can be incorrect when applied to an antenna in a warm plasma.

Tunable radio antenna

Abstract: A tunable, resonant antenna in which reduction in height and multiple frequency band operation is achieved by using a symmetrical in-phase array of two or more electrically short, vertical wave radiator elements of equal length which are brought to electrical resonance by end connection to an equal number of horizontal transmission line sections so folded in alignment as to be non-radiative, such transmission line sections being commonly terminated in a shunt variable reactor located at the center of the symmetrical array to provide change of the resonant frequency.

Theoretical and experimental study of a finite cylindrical antenna in a plasma column

Abstract: A numerical technique has been used to solve the integral equation determining the current distribution on a finite cylindrical antenna in a long plasma column; a "cold" isotropic plasma model with a relative dielectric constant \epsilon_{r} = 1 - \omega_{p}^{2}/\omega^{2} is used in the analysis. Collision losses and inhomogeneities in the plasma have been ignored for the sake of mathematical simplicity. It is found that when 0 , the plasma column tends to behave like a dielectric and reduces the effective electrical length of the antenna. The current distribution is still somewhat sinusoidal but with a longer wavelength. In the range -1 , the antenna characteristics undergo a drastic change; the current decays very rapidly along the antenna and, for antennas longer than a quarter wavelength, the input admittance remains almost constant and independent of the length. Extensive experimental measurements have been made to verify the theory. The plasma sheath surrounding the antenna was produced by an active, hot.cathode, helium discharge; the plasma diagnostic measurements were made by using Langmuir probes and cavity perturbation techniques. The theoretical and experimental results show a significant degree of qualitative agreement.

Conical logarithmic-spiral antenna

Abstract: The invention is for an antenna of the conical logarithmicspiral class. Specifically there is disclosed a means of utilizing a terminating active region to reduce the overall size of such an antenna by a factor of two without significantly modifying the antenna characteristics. Reference is made to the claims for a legal definition of the invention.

Novel helical antenna

Abstract: A directional electromagnetic radiating antenna with circular polarization capable of operating over wide frequency bands and having a greater electrical length than actual physical length. The invention applies basically to a helical antenna utilizing one or more unifilar or multifilar windings which possess the characterizing feature of having an increased electrical path length whereby the operating characteristics of the antenna will resemble that of a larger physical structure than is actually necessary to support the hardware comprising the antenna.

A Microstrip Nonreciprocal Tunable YIG Filter

Abstract: A nonreciprocal tunable YIG filter in a microstrip configuration has been constructed which makes use of a novel method of generating a circularly polarized field in the plane of a microstrip circuit. Nonreciprocities in excess of 40 dB have been obtained at X band with relatively low insertion loss and VSWR.

Broadband cornucopia-type antenna system

Abstract: The present invention describes a broadband, low-profile circularly polarized antenna, primarily for airborne applications which has a substantially omnidirectional radiation characteristic in the horizontal plane. The form factor of the antenna comprises a cornucopia-shaped element having an arcuate surface which is defined by a plurality of polynomial line segments and which diverges from one terminal end to the other.

Effect of plasma on propagation constant and radiations of a linear antenna with feed points displaced transverse to the antenna axis

Abstract: A theoretical study has been made to predict the effect of feed points displaced transverse to the axis of a centre-fed linear antenna immersed in a weakly ionized compressible warm plasma. A linearized theory is used such that the isotropic electron plasma is regarded as a single fluid continuum. A thin linear resonant antenna with its feed points displaced transverse to the antenna axis is used as a source of radiation and the propagation constant on it is taken to be general. General expressions for a field pattern factor and radiation resistance for both the electromagnetic and electroacoustic waves have been obtained. The case of a. half-wave dipole antenna is then treated, giving different values to the propagation constant. Some specialized results of other investigators are recovered under the condition that displacement is zero.

Antenna system for capacitance responsive circuit

Abstract: Each of two embodiments of an antenna system for capacitancecontrolled circuits comprises an antenna member which forms a common plate of first and second capacitances, and a shield for interrupting electric flux between the antenna and grounded elements near the rear surface of the antenna. A first embodiment also comprises a fixed increment of the first capacitance between the antenna and a conductive element situated between the antenna system encasement and the controlled sanitary facility which the encasement abuts. The encasement functions as a dielectric in the aforementioned increment of capacitance, and the conductive element operates to prevent spurious increases in antenna capacitance to ground which result from the intermittent flow of water in the controlled sanitary facility. A second embodiment comprises a conductive element disposed about the periphery of he antenna member and spaced therefrom This conductive element forms a second plate to the second capacitance, and effectively shields he antenna member from electric fields apssing through the c encasement.

The input admittance of a rectangular aperture antenna loaded with a dielectric plug

Abstract: Aperture-admittance expression for waveguide-fed rectangular aperture antenna, loaded with dielectric plug

Linear antennas in plasma media

Abstract: : The problems of a gap-excited finite-sized linear antenna, with and without a vacuum sheath, operated in a uniform cold and in a uniform warm lossy plasma medium, have been considered by applying integral equation and boundary value problem techniques. The dependence of the input admittance, the current distribution, and the radiation pattern, upon the collision frequency, the electron temperature, the length of the antenna, the length-to-radius ratio for the antenna, the ratio of the plasma frequency to the operating frequency, and the thickness of a vacuum sheath have been investigated. An integral equation formulation relating the electric field intensity to the current on the antenna, and several boundary value problem formulations concerned with prolate spheroidal antennas, with and without confocal prolate spheroidal vacuum sheaths, have been considered. Admittance curves are given from which the input admittance of a finite linear antenna can be estimated for a wide range of operating conditions and antenna structures. Conductance and susceptance maxima, dependent upon the vacuum sheath thickness, have been observed when using the cold plasma model, for omega < omega sub p. When using the warm plasma model in conjunction with the boundary condition that the normal component of the fluid velocity is zero at the antenna surface or the vacuum sheath surface, the radiation resistance of the antenna, is increased significantly, for the parameters considered. (Author)

Linear antennas in a warm plasma driven from a coaxial air-filled transmission line

Abstract: The Green's function is formed for the warm-plasma region surrounding an antenna driven from a coaxial air-filled transmission line, and hence the current distribution and input admittance of three types of antenna having this feed system are computed. Comparison is made between the antenna characteristics when driven in this fashion and by an idealised delta gap.