Thin Dipole Research Articles

Comment on "The minimization of the back scattering of a cylinder by central loading"

K.M. Chen and V. Liepa (IEEE Trans. Antennas Propag., p.576-82, September 1964) described the broadside backscatter of a thin dipole. The model is summarized by various. These work very well at all frequencies specified by those authors, except for one-physical resonance. This is the wavelength at which the antenna's total length is half a wavelength. The present author develops an alternate set of equations which are valid at resonance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Behavior of a received pulse radiated by half-wave dipole excited by a single-cycle sinusoidal voltage

The zero-order approximate solution for the currents along thin antennae is used to study the behavior of a received voltage pulse across the terminals of a thin dipole placed at the far zone of a thin transmitting dipole excited by a single-cycle sinusoidal voltage. It is found that each of the four distinct electric field pulses which the transmitting dipole radiates, induces four distinct (although overlapping) voltage pulses at the discontinuities of the receiving dipole antenna. Although the exciting voltage is single-cycle, the time duration of the incident electric field and the induced received voltage is lengthened by 1.5 cycles and up to 2 cycles, respectively. The receiving antenna behaves like an integrating circuit. The spectra of the short-pulse radiated field and the received voltage have peak values at frequencies higher than the carrier frequency f 0 of the exciting single-cycle sinusoidal voltage.

Transient radiation of a single-cycle sinusoidal pulse from a thin dipole

The behavior of the radiated electric field from a half-wave dipole in free space excited by a single-cycle sinusoidal voltage is studied. The zero-order approximate solution for the current along the antenna in the frequency domain is used, so that the time-dependent current as well as the radiated electric field can be calculated and interpreted easily. Under a suitable matched condition, the time dependent current along each half-section of the dipole is made up of a current pulse traveling from the feed-point and a reflected one from the end-point. However, the radiated electric field consists of five overlapping signals exhibiting that radiation takes place only from the discontinuities of the dipole antenna. Both current and the radiated electric field are extended in time due to the reflection of current from the end-points of the dipole antenna. It appears that the spectral bandwidth of the radiated electric field is narrower than that of the exciting voltage pulse. This phenomenon may be due to the filtering effect of the half-wave dipole.

Arrays: A software package for analysis of antenna arrays

This article describes a software package useful for the instruction of antenna array theory. The program provides the radiation pattern of different types of antennas, the array factor of linear, two-dimensional and three-dimensional arrays, and the total radiation pattern. The elements of the array are isotropic source, Hertzian dipole, straight thin wire dipole, and finite line source with uniform current distribution. The user has the freedom to choose one of the supported element types or to provide the pattern of an antenna element based on experimental or calculated data. This article serves as a tutorial for selected examples as well as a quick guide for the use of this software.

A scale-model study of down-hole VHF dipole arrays with application to subsurface exploration

The cross-borehole measurement technique at VHF frequencies typically employs winched single transmitting and receiving dipoles in various offset configurations to detect a buried target and estimate its vertical position from the pattern of forward scatter. Signal-to-noise ratio (SNR) and clutter from random scatterers in the host medium are practical limitations to target detection that can be modified by means of synthetic collinear arrays whose electric fields are determined as a function of vertical position from the measured amplitude and phase of a single element as it moves in the borehole. The present paper compares theoretical calculations based on a thin bare dipole in a moderately lossy host medium with a combination of laboratory scale model measurements and simple synthetic array techniques to indicate the potential advantages of the latter to geophysical exploration. >

Comments on "An exact method of integration for vector potentials of thin dipole antennas" [with reply

It is noted that the result given in eq.(11) of the above named work (see ibid., vol.AP-35, no.4, p.442-4, 1987) is not unique because of the sign. The relation is corrected. In replying P.L. Overfelt corrects eq.(12) and explains the sign convention of the original eq.(11).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thin wire dipoles—a finite-difference time-domain approach

The computation of thin wire dipole radiation patterns using the finite-difference time-domain method is discussed.

Vernier acuity as line and dipole detection

The vernier judgment is commonly thought of as discriminating the displacement of a portion of a pattern. However, we have found it revealing to consider vernier stimuli in another light; as the composite of a test pattern superimposed on a masking pedestal. The pedestal is the pattern with zero spatial offset and the test pattern is the luminance distribution which, when added to the pedestal, produces the offset. For example, a vernier offset of an edge can be generated by adding a thin line (the derivative of an edge) to one half of an edge pedestal, and a vernier offset of a line can be generated by adding a thin dipole (the derivative of a line) to one half of a line pedestal. Vernier thresholds for low contrast edge and line pedestals can be directly predicted from detection thresholds of thin lines and dipoles on uniform fields. A surprisingly simple relationship is also derived between vernier thresholds and the size of Ricco's integration zone. We have found this masking paradigm to be fruitful and believe it is relevant to all the hyperacuities, not just vernier.

Rigorous analysis of an imperfectly conducting linear antenna

A Wiener–Hopf type analysis is introduced to determine the radiation characteristics of an imperfectly conducting solid thin long dipole antenna. The analysis is applicable to dipoles with constant impedance per unit length. The input admittance of the infinitely long imperfectly conducting dipole is calculated and compared with available experimental and analytical data.

Simple expressions for mutual impedances

A method of evaluating mutual impedances between thin dipoles is presented. They may be free or printed ones. It involves an asymptotic expansion of a bidimensional Fourier integral. Very simple algebraic expressions are derived, which are convenient for hand calculations. The numerical results are more accurate than previously. The technique is extended to include the presence of an infinite ground plane. Then, using the stationary phase method, simple coupling equations are derived for microstrip elements.

An exact method of integration for vector potentials of thin dipole antennas

A general method for exact integration of vector potentials of thin dipole antennas characterized by various current distributions is developed. Such solutions are shown to be independent of the usual farfield restrictions involving dipole length, observation point distance, and wavelength. Their convergence is rapid in the induction and near-field regions.

Convergence phenomenon in the solution of dichroic scattering problems by Galerkin's method

The convergence problem that arises when the scattering problem of dichroic surfaces is solved numerically by means of Galerkin&apos;s method and Floquet&apos;s theorem is investigated. A theoretical discussion is outlined showing that a truncation of the infinite Floquet spectrum is actually equivalent to modifying the used basis functions. Examples of modified basis functions due to different Floquet-mode truncations and the effect on the numerical results are demonstrated for the particular cases of arrays of thin dipoles and crossed dipoles. Some useful truncation rules are also presented, and the theories are verified by comparing predicted values with experimental results obtained by waveguide simulator measurements

Gap problem in king-middleton second-order theory for dipole admittance calculations

The ‘gap problem’ associated with the King-Middleton second-order theory has been solved by King et al. The empirically determined susceptance values of the knife-edge capacitance as given in Reference 1 were found to be reliable for thin dipoles, but not for thicker ones. The cause of this imperfection is determined and a table of the corrected values included in this letter.

Trigonometric Spiral Array—A Study of the Field Patterns Using Induced EMF Theory

A theoretical study of far-Held patterns for a plane trigonometric spiral array (of the form r = a cos φ/4 m) with thin, linear, centre-driven, vertically-placed and non-staggered half-wave dipole radiators has been made. The complex currents of the radiators are obtained with the help of the Induced EMF theory, considering all self and mutual impedances between the radiators. The feed voltage is assumed to be one volt in determining the complex currents. A set of graphs showing the far-field patterns using the theory, are plotted and critically discussed.

The Conical Antenna as a Sensor or Probe

The electrically small wide-angled spherically capped conical monopole is shown to have frequency-related properties closely resembling those of the electrically thin cylindrical dipole. It is frequency-independent when used to measure the time derivative of the electric field when it is connected to a matched load and kL = kl( 1 + ?0) ? 1. Here/is the radius of the conical surface and ?0 is half of the angle subtended by the cone. Graphs are shown for ?0 470° = 0.82 rad for which the characteristic impedance is 50 ?.

The near field of dipole antennas, part II: Experimental results

The results of an experimental program to evaluate the electric field near dipole antennas are presented. The measured field intensities are compared with the numerical values computed using the theory developed in Part I of this paper. The theoretical and measured field intensities are in excellent correlation even for observation points spaced from the axis of the dipole less than one hundredth of a wavelength. For thin dipoles (radius ≃ .002λ) the experimental measure of the E-field at the antenna surface or at one antenna radius distance has not been possible because of the practical limitation of available instruments. The experimental and theoretical results show that the field intensities near some parts of a dipole antenna are higher than predicted by commonly used formulas.

Wire antennas coated with magnetically and electrically lossy material

The effect of coating a thin dipole antenna with a thin layer of magnetically and electrically lossy material is considered with respect to the properties of input impedance, current distribution, far‐field pattern, bandwidth, radiation efficiency, and effective length. Moment method calculations show that the change in the antenna properties is a strong function of the location and the kind of lossy material applied. The calculated input impedance of a monopole wrapped both fully and partially with different types of lossy materials is shown to agree well with measurements. An approximate semigraphical procedure for impedance calculation is postulated and shown to be useful.

Improvements to nonnumerical methods for calculating the transient behaviour of linear and aperture antennas

The time-domain response of linear and aperture antennas is analyzed. The results are based on models which have proven to be satisfactory for sinusoidal steady-state analysis. The calculated results correlate the physical parameters of both transmitting and receiving structures with the time-domain characterization of their response. The methods presented herein are useful to provide simple yet powerful alternatives to numerical techniques for the solution of transient radiation problems. The time-domain impulse response is calculated for thin cylindrical dipoles and the aperture formed by two semi-infinite parallel planes. Comparison between experiment and theory is provided. Analytical expressions are derived which characterize the response to excitations that are bandlimited in a manner dictated by the models, e.g., thin wire approximation and TEM mode excitation limitations.

Input impedance of thin dipoles by moment method

The input impedance of half-wave dipoles with decreasing diameters has been calculated using the moment method of analysis with a stepped approximation of the current distribution. It is shown that the solution becomes increasingly inaccurate when the wire radius decreases and only a few segments for the antenna are used, and that it also diverges from the accurate answer when the length/diameter ratio of each segment is such that the axial-line-current and charge approximations become insufficient.

Radiation Patterns of TV Transmitting Dipole Arrays

When designing a dipole 'panel', a unit building block for a TV transmitting dipole array, there are several constraints which need to be met viz. beamwidth, sidelobe levels, front to back ratio and input impedance. Theories on reflector backed dipole arrays have so far dealt with idealised or thin dipoles and with infinite reflector. They are not very useful for predicting sidelobe levels and front to back ratios nor would they be of any use to calculate the input impedance of an array of relatively thick dipoles which are often used in practice. Experimental procedures are usually employed by the designer and these have proved to be very time consuming.