Showing papers on "Dipole antenna published in 1981"

Antenna theory and design

Abstract: Antenna Fundamentals and Definitions. Some Simple Radiating Systems and Antenna Practice. Arrays. Line Sources. Resonant Antennas: Wires and Patches. Broadband Antennas. Aperture Antennas. Antenna Synthesis. Antennas in Systems and Antenna Measurements. CEM for Antennas: The Method of Moments. CEM for Antennas: Finite Difference Time Domain Method. CEM for Antennas: High-Frequency Methods. Appendices. Index.

Microstrip antenna technology

Abstract: A survey of microstrip antenna elements is presented, with emphasis on theoretical and practical design techniques. Available substrate materials are reviewed along with the relation between dielectric constant tolerance and resonant frequency of microstrip patches. Several theoretical analysis techniques are summarized, including transmission-line and modal-expansion (cavity) techniques as well as numerical methods such as the method of moments and finite-element techniques. Practical procedures are given for both standard rectangular and circular patches, as well as variations on those designs including circularly polarized microstrip patches. The quality, bandwidth, and efficiency factors of typical patch designs are discussed. Microstrip dipole and conformal antennas are summarized. Finally, critical needs for further research and development for this antenna are identified.

Finite-Difference Analysis of EMP Coupling to Thin Struts and Wires

Abstract: This paper describes the implementation of the thin-strut formalism in the 3-D EMP time-domain finite-difference code THREDE. The thin-strut formalism permits inclusion of arbitrary fine wires in THREDE without imposing any corresponding demand to reduce the cell size to the wire size. The keystone of this technique is the so-called in-cell inductance-the inductance per unit length a thin wire would have with respect to an enclosing conductor half a cell removed. THREDE results using this formalism are compared with analytic EMP solutions for a linear dipole antenna and a loop antenna. Errors are around 10 percent for the loop and 7 percent for the dipole. The 10-percent loop error could probably be improved; the 7-percent dipole error seems to be fundamental to the basic THREDE approximations.

Current distribution and input impedance of printed dipoles

Abstract: Printed dipole antennas find increasing use in microwave as well as far infrared frequencies. The current distribution, input impedance, and radiation pattern are computed for wire antennas printed on a dielectric substrate. The current distribution is obtained by solving Pocklington's equation by moment methods. The Green's function pertinent to the problem involves improper Sommerfeld-type integrals. These integrals are computed by a real-axis integration technique which involves analytical and numerical steps. The effect of surface modes is carefully taken into account.

Antennas in Matter: Fundamentals, Theory, and Applications

Abstract: The volume provides an introduction to antennas and probes embedded within or near material bodies such as the earth, the ocean, or a living organism. After a fundamental analysis of insulated and bare antennas, an advanced treatment of antennas in various media is presented, including a detailed study of the electromagnetic equations in homogeneous isotropic media, the complete theory of the bare dipole in a general medium, and a rigorous analysis of the insulated antenna as well as bare and insulated loop antennas. Finally, experimental models and measuring techniques related to antennas and probes in a general dissipative or dielectric medium are examined.

Phased array theory and technology

Abstract: This review of array antennas highlights those elements of theory and hardware that are a part of the present rapid technological growth. The growth and change in array antennas include increased emphasis on "special-purpose" array techniques such as conformal and printed circuit arrays, wide angle scanning arrays, techniques for limited sector coverage, and antennas with dramatically increased pattern control features such as low sidelobe, adaptively controlled patterns. These new topics have substantially replaced large radar arrays in the literature and constitute a major change in the technology. The paper presents a tutorial review of theoretical developments emphasizing techniques appropriate to finite arrays, but indicating parallel developments in infinite array theory, which has become the useful tool for analysis of large arrays. A brief review of the theory of ideal arrays is followed by a generalized formulation of array theory including mutual coupling effects, and is appropriate to finite or infinite arrays of arbitrary wire elements or apertures in the presence of a conducting ground screen. Some results of array tolerance theory are summarized from the literature and retained as reference throughout discussions of array component requirements and device tolerance for low sidelobe arrays. Examples from present technology include conformal and hemispherical coverage arrays, lightweight printed circuit arrays, systems for use with reflectors and lenses in limited sector coverage applications, and wide-band array techniques.

Electromagnetically coupled microstrip dipoles

Abstract: A new class of printed circuit radiator consisting of a microstrip dipole electromagnetically coupled to a microstrip feed line is described. Several configurations which differ in bandwidth, efficiency, and construction simplicity are presented. A geometry which has been found to be optimum for many applications is noted. Radiation characteristics of both isolated elements and arrays of elements are examined. Experimental and theoretical results are presented.

Mutual impedance computation between printed dipoles

Abstract: The mutual impedance between microstrip dipoles printed on a grounded substrate is computed. Results for the microstrip dipoles in broadside, collinear, and echelon arrangements are presented. The significance of surface waves to mutual coupling is discussed.

Planar antennas on a dielectric surface

Abstract: A theory has been developed for planar metal antennas on a dielectric surface and the main predictions have been verified experimentally. Current dipole antennas have radiation diagrams and impedances favourable for microwave to far-infra-red integrated circuits.

Low profile circular array antenna and microstrip elements therefor

Abstract: An antenna element is comprised of two rectangular microstrip patch dipoles spaced by dielectric a predetermined distance above a ground plane conductor. One edge of each dipole is electrically shunted to the ground plane conductor. The dipole feedpoints are separated by a quarter wavelength of the antenna resonant frequency. An isolated power splitter and phase shifter connects an antenna element port with the dipole feedpoints so that the signal at one feedpoint lags the signal at the other feedpoint by 90°. The antenna element will end fire through the dipoles in the direction of the lagging signal feedpoint. A low profile circular array antenna is comprised of eight such antenna elements arranged on the ground plane conductor equally spaced with their phase centers on a common phase center circle.

An experimental study of the circular-polarized elliptical printed-circuit antenna

Abstract: Elliptical-shaped printed-circuit antennas were fabricated with varying eccentricities, and their impedance and radiation patterns were measured. Special attention was devoted to investigating the design criteria which produced the best circular polarization.

Wideband quasi-log-periodic microstrip antenna

Abstract: The paper describes a new design method for a wideband array of log-periodically scaled microstrip resonator antennas. The radiating elements are series-fed by a simple coplanar microstrip network. This network consists of an open-circuited feed line with a branch line connected to each radiating element. Both a network and a radiating model for the complete structure are explained. These models predict with good accuracy the input impedance and the radiation pattern as a function of frequency. The results for a 5-element S-band antenna are presented as an illustrative example. This antenna combines a good impedance match (VSWR ? 2.6) with a reasonable power gain in broadside direction (> 5.5 dB) over a 22% bandwidth. This means a tenfold increase in the bandwidth in comparison with a single microstrip resonator antenna.

Theft detection apparatus using saturable magnetic targets

Abstract: An electronic theft detection apparatus for detection of saturable magnetic targets has transmitter and receiver antennas formed of single turn loops of rigid metal pipe. The antennas are rectangular and have a width, in the direction of passage, through the interrogation zone, less than the length of a shopping cart. The transmitter antenna is in the form of a rectangular loop and the receiver antenna is of the same overall size and configuration but is bisected with a conductor to form two balanced loops. The antennas are purely inductive and a series resonant circuit is inductively coupled into the transmitter antenna and a parallel resonant circuit is inductively coupled out of the receiver antenna. Special circuits are also provided for temporarily disabling the apparatus when a related lower harmonic frequency signal decreases in amplitude.

Improved performance of a subsurface radar target identification system through antenna design

Abstract: Improved identification performance of a video pulse subsurface radar system is reported. The video pulse system, which utilizes complex natural resonances of the target and a prediction correlation processing, is improved in comparison to the system reported previously by better fitting the system bandwidth to the bandwidth which contains the complex natural resonances of the desired target. The antenna and associated hardware modifications to achieve this are described. Identification performance of the modified system is given using actual buried land mine-like targets. Significant improvement of the quality of the received waveforms and hence the signal-to-clutter ratio is obtained. Potential further improvement is discussed. This may be achieved by removing the natural resonance associated with the antenna from the data prior to the application of the predictor correlator.

Phase-variable spiral antenna and steerable arrays thereof

Abstract: An antenna utilizes a conductive helix mounted in front of a conductive cup and transformer impedance-matching balun, with the helix rotatable about the antenna center line to allow adjustment of the variable phase thereof with respect to a reference phase. An array formed of a plurality of the phase-variable antennas allows the maximum gain lobe of that array to be steered through some angle, relative to an array center line essentially parallel to the parallel center lines of the plurality of array antennas, by variation of the individual antenna phases, relative to a reference phase. The plurality of antennas may have the feed points thereof combined, to provide a high-gain steerable array of relatively great mechanical strength.

Note on the integral equation for a straight wire antenna

Abstract: It is shown that certain integral equations for the wire antenna possess a unique solution so that difficulties associated with analytical or numerical evaluation cannot be attributed to either the absence of a solution or its nonuniqueness. There are, however, some singularities in the solution and the significance of these for numerical methods is discussed.

Broadband pulse-optimised antenna

Abstract: The theoretical far-field pattern, gain, and aperture are derived for a V-shaped dipole carrying a nonuniform current wave. Particular attention is given to broadening in the far field of a sharp current pulse applied at the input. The optimum variation of characteristic TEM wave impedance is then derived with reflection coefficient and pulse broadening as constraints. Measurements on a practical design of 70 cm length show a bandwidth from 200 MHz to 1.6 GHz for an input voltage reflection coefficient less than 0.1 and a pulse broadening of 35ps. The directional diagram is±25° to half power.

The design of microstrip dipole arrays including mutual coupling, part II: Experiment

Abstract: Experiments are described from which determination can be made of the self and mutual impedance for microstrip dipoles and of the backscattering relation involving the radiating current. Functional representations of these sources of input data then permits the design of planar microstrip dipole arrays, including the effects of mutual coupling. The design, construction, and performance of a typical array are described. Agreement between theory and experiment is good.

An Analysis of Log Periodic Antenna with Printed Dipoles

Abstract: An analysis of Log Periodic Antenna with Printed Dioples is presented here. In this analysis, the wave equation for Hertz potential is solved in Cartesian coordinates applying the boundary conditions of a flat strip diople. Using this model, the input currents to the antenna elements, the current distribution of the antenna elements, and the radiation pattern are computed. The computed results are compared with experimental results.

Optically coupled, array antenna

Abstract: A scannable antenna having a radiating array of antenna elements correspondingly coupled, through equal line lengths, to a more closely spaced array of antenna elements positioned in a space coupling region. A feed array of antenna elements, with spacings substantially equal to the spacing in the radiating array and substantially of the same physical size as the more closely spaced array, is positioned in the space coupling region in close proximity, no more than a wave length away, to the more closely spaced array. The feed array is coupled to a distribution network which provides desired phase and amplitude aperture distributions.

Characteristics of circular loop antennas above a lossless ground plane

Abstract: The circuit and radiation characteristics of a circular loop antenna above a lossless ground plane are studied. It is shown that the gain of this antenna is higher than that of a half-wave dipole above the ground plane. A gain as high as 10 dB is obtainable with this simple geometry.

The impedance of an elliptical printed-circuit antenna

Abstract: A resonant circuit model for the input impedance of an elliptical printed-circuit antenna has been developed and the results compared with experimental data. The impedance and bandwidth were then calculated as a function of the size, eccentricity, and thickness of the radiator.

Dual band collinear dipole antenna

Abstract: A collinear dual dipole antenna is split into two sections which are connected by a central conductor extending in spaced parallel relation within hollow support mast sections, and forming an effective transmission line providing RF continuity at a high band frequency f, and discontinuity at a low band frequency 1/2 f. The configuration provides a dual band antenna operating in either band from a single source without filtering and without modification of the antenna. In the high frequency band, the antenna operates as a dual dipole array. In the low frequency band, the antenna operates as a single dipole array with each mast section and its respective dipole acting as half of the single dipole array.

Combined dipole and ferrite antenna

Abstract: A small sized reception antenna for VHF and/or UHF band for the use in a room has been found. The antenna has a horizontal dipole type first antenna portion having a folded elongated conductor, and a vertical second antenna portion having a ferrite pole electromagnetically coupled with said horizontal first antenna portion. Said horizontal first antenna portion is rotatable in a horizontal plane, while the second antenna portion is fixed vertically. A tank circuit with a tank coil wound on the ferrite pole and a variable capacitor is provided to resonate the antenna with the reception frequency. An output coil is wound on the ferrite pole, and said output coil provides the output signal of the present antenna. Means for sliding the output coil along the ferrite pole is provided to adjust the output impedance of the present antenna for each of the reception frequencies.

Rod antenna, particularly for mobile FM signal transducing applications

Abstract: To provide a short FM antenna, of about for example 40 cm length for mobile radio, for example automobile radio application, without degradation of signal strength with respect to an about 1 m long FM antenna, a conically tapering insulating rod, for example of fiberglass, has two windings applied thereover, the two windings, each, having a straight wire length of about 1/4 the median wavelength of the FM band, and the overall length (l) of the rod having said two windings applied thereover being about 1/8 of the median wavelength. The oppositely wound windings (11, 12) are connected at their center, and may be formed as one bifilar winding, with the lower end of the lower winding being connected to an electrical terminal for standard connection to, for example, a coaxial antenna connector for an automobile radio. A spiral spring can be interposed if extreme deflectability of the antenna is desired, for example to prevent damage if the antenna, applied to an automotive vehicle, is passed through a power washing and scrubbing station.

Monopole antenna patterns on finite size composite ground planes

Abstract: Geometrical theory of diffraction methods have been used to develop models and to predict the patterns of communications, navigation, and identification (CNI) blade antennas mounted on finite size composite ground planes. The computed patterns agree extremely well with measurements. It has been shown, both analytically and experimentally, that very minor differences between patterns of antennas mounted on perfectly conducting and composite ground planes appear for conductivities equal to 104s/m.

Highlights of antenna history

Abstract: A look at the major events in the development of antennas.

Analysis of Miniature Electric Field Probes with Resistive Transmission Lines

Abstract: The miniature dipole probe is a useful tool for measuring the electric field at high radio and microwave frequencies. A common design for the probe consists of an electrically short dipole antenna with a diode across its terminals; a resistive, parallel-wire transmission line transmits the detected signal from the diode to the monitoring instrumentation. The high resistance per unit length of the transmission line reduces the direct reception of the incident field by the line and also reduces the scattering of the incident field by the line. In addition, the resistive transmission line serves as a low-pass filter in the detection process. In this paper, the effect of the resistive transmission line on the operation of the miniature field probe is analyzed. Specifically, the reception of the incident signal by the transmission line is compared with that of the dipole. The scattering of the incident signal by the transmission line is studied by means of the scattering cross section, and the limitation imposed on the measurement of amplitude-modulated signals by the low-pass filtering by the resistive line is examined. The results of the theoretical analyses are presented as simple formulas which are useful in the design and optimization of the probe. The theoretical results are shown to be in good agreement with measurements.