Planar Dipole Array Research Articles

Asymptotic high-frequency Green's function for a large rectangular planar periodic phased array of dipoles with weakly tapered excitation in two dimensions

This paper deals with the derivation and physical interpretation of a uniform high-frequency representation of the Green's function for a large planar rectangular phased array of dipoles with weakly varying excitation. Thereby, our earlier published results, valid for equiamplitude excitation, and those for tapered illumination in one dimension are extended to tapering along both dimensions, including dipole amplitudes tending to zero at the edges. As previously, the field obtained by direct summation over the contributions from the individual radiators is restructured into a double spectral integral whose high-frequency asymptotic reduction yields a series of propagating and evanescent Floquet waves (FWs) together with corresponding FW-modulated diffracted fields, which arise from FW scattering at the array edges and vertexes. To accommodate the weak amplitude tapering, new generalized periodicity-modulated edge and vertex slope transition functions are introduced, accompanied by a systematic procedure for their numerical evaluation. Special attention is given to the analysis and physical interpretation of the complex vertex diffracted ray fields. A sample calculation is included to demonstrate the accuracy of the asymptotic algorithm. The resulting array Green's function forms the basic building block for the full-wave analysis of planar weakly amplitude-tapered phased array antennas, and for the description of electromagnetic radiation and scattering from weakly amplitude-tapered rectangular periodic structures

Matrix pseudo-inversion technique for diagnostics of planar arrays

It is shown, by means of numerical simulation, that the Moore-Penrose pseudoinverse of a matrix taken from an overdetermined system can be applied to retrieve the excitation distribution of a planar array of parallel dipoles with faulty elements, by measuring the complex radiated field in its near zone. Failures on voltage (considering mutual coupling) and current of several elements, and systematic or random measurement errors, are considered in the simulation.

Planar reconfigurable pattern antenna by reactive-load switching

Reactive-load switching is proposed to achieve a reconfigurable unidirectional pattern for a planar center-loaded linear Yagi dipole array. Two crossed arrays of dipoles are printed on both sides of a substrate in order to implement a scanning pattern in the whole horizontal plane, and each group consists of one active dipole and a couple of reactive-load parasitic dipoles. Due to the capacity of loaded value optimization, this antenna has good front-to-back ratio in its gain pattern; moreover, it has a compact structure and is suitable for integration with mobile terminals. Simulation and measurement are carried out to verify this design. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 506–507, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21212

Non‐Foster and connected planar arrays

A planar array of dipoles, with contiguous collinear dipole ends connected by a fixed inductor or capacitor, is evaluated. A Moment Method simulation of a 20 × 20 array provides Scan Element Pattern (gain per element), Scan Impedance, and current distributions. Cases considered, over a 10:1 bandwidth (dipole length .05λ to .5λ), include zero impedance coupling, capacitor coupling, inductor coupling, and Non‐Foster negative inductor coupling. The last is outstanding, probably because the physics of the Non‐Foster coupling makes sense.

Omnidirectional Planar Dipole Array Antenna

A planar dipole array antenna having good omnidirectional radiation in the azimuthal plane is presented. The planar dipole array antenna comprises two 1 /spl times/ 2 dipole arrays arranged back to back and separated by a narrow rectangular ground plane, and is easily constructed by printing on both sides of a dielectric substrate. Prototypes of the proposed antenna for WLAN operation in the 2.4 GHz band (2400-2484 MHz) were constructed and studied. Good omnidirectional radiation with gain variations less than 2 dBi in the azimuthal plane has been obtained, and the measured maximum antenna gain for operating frequencies across the 2.4 GHz band is about 5.0-6.1 dBi. Effects of the ground-plane width and the array spacing on the performance of the proposed antenna are also studied.

A matrix decomposition technique based on the concept of measure and its application to planar phased dipole arrays

Full impedance matrices of the method of moments (MoM) type have been decomposed into sparse matrices in the application of on-surface measured equation of invariance (OSMEI) (Rius et al. (1996, 1997)). The objectives in Rius are to find continuous current distributions on scatterers. Thus, the concept of metron and measure is justified under the postulate that the local relation between fields and current densities is an invariant of the excitation. In this paper, we have extended the concept to dipole arrays, where the objective is to find the discrete driving point currents. Numerical results show that using the windowed metrons presented in this paper, the sparsity rate of the sparse matrices can be kept within 1%, while the E- and H-plane patterns are still in good agreement with the MoM results except for the farthest side lobes of the H-plane patterns.

Wideband dipole arrays using non‐Foster coupling

AbstractA planar array of dipoles, with collinear dipoles connected by lumped negative inductances, is simulated by the piecewise sinusoidal method of moments. Over a multi‐octave bandwidth, the gain is close to the area gain, which is a remarkable result. The non‐Foster couplings smooth out and increase the current at low frequencies. Recent advances in transistor circuits and topology allow this new array to be considered. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 453–455, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11087

Short‐pulse radiation by a sequentially excited semi‐infinite periodic planar array of dipoles

This paper deals with the fourth in a sequence of canonical problems aimed toward an understanding of the time domain (TD) behavior of wideband‐excited sequentially pulsed planar periodic finite arrays of dipoles, which play an important role in a variety of practical applications. The present investigation of sequentially pulsed semi‐infinite planar dipole arrays extends our previous studies of sequentially pulsed infinite and semi‐infinite line dipole arrays and of infinite planar dipole arrays. The discrete element‐by‐element radiations are converted collectively to radiations from a series of Floquet wave (FW)‐modulated truncated smooth equivalent aperture distributions, and to corresponding FW‐modulated edge diffraction. After a summary of necessary results from the earlier studies, emphasis is placed on the new truncation‐induced TD results and interpretations, which are extracted via phenomenology‐matched high‐frequency asymptotics from rigorous frequency and time domain formulations parameterized in terms of the dispersive FW instantaneous frequencies and wave numbers. As in our previous studies, the outcome is a numerically efficient, physically incisive algorithm whose accuracy is verified preliminarily by application to a pulsed planar strip array of dipoles.

Time-domain green's function for an infinite sequentially excited periodic planar array of dipoles

The present paper is a continuation of previous explorations by the authors, aimed at gaining a basic understanding of the time domain (TD) behavior of large periodic phased (i.e., sequentially turned-on) array antennas and related configurations. Our systematic investigation of the relevant canonical TD dipole-excited Green's functions has so far included those for infinite and truncated sequentially pulsed line periodic arrays, parameterized in terms of radiating (propagating) and nonradiating (evanescent) conical TD Floquet waves (FW) and truncation-induced TD FW-modulated tip diffractions. The present contribution extends these investigations to an infinite periodic sequentially pulsed planar array, which generates pulsed plane propagating and evanescent FW. Starting from the familiar frequency domain (FD) transformation of the linearly phased element-by-element summation synthesis into summations of propagating and evanescent FWs, we access the time domain by Fourier inversion. The inversion integrals are manipulated in a unified fashion into exact closed forms, which are parameterized by the single nondimensional quantity /spl eta/=c/v/sup (p)//sub u1/, where v/sup (p)//sub u1/ and c are the excitation phase speed along a preferred phasing direction u/sub 1/ in the array plane and the ambient wave speed, respectively. The present study deals with the practically relevant rapidly phased propagating case /spl eta/<1, reserving the more intricate slowly phased /spl eta/>1 regime for a future manuscript. Numerical reference data generated via element-by-element summation over the fields radiated by the individual dipoles with ultrawide band-limited excitation are compared with results obtained much more efficiently by inclusion of a few TD-FWs. Physical interpretation of the formal TD-FW solutions is obtained by recourse to asymptotics, instantaneous frequencies and wavenumbers, and related constructs. Of special interest is the demonstration that the TD-FWs emerge along "equal-delay" ellipses from the array plane; this furnishes a novel and physically appealing interpretation of the planar array TD-FW phenomenology.

Applications of hybrid discrete Fourier transform moment method to the fast analysis of large rectangular dipole arrays printed on a thin grounded dielectric substrate

AbstractRecently a discrete Fourier transform–method of moments (DFT‐MoM) scheme was developed for fast analysis of electrically large rectangular planar dipole arrays, which has been shown to be very efficient in terms of number reduction of unknown variables and computational complexity. The applications of this DFT‐MoM to treat dipole arrays printed on a grounded dielectric substrate are examined in this Letter. Numerical results are presented to validate its efficiency and accuracy. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 203–207, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10417

Three-dimensional Green’s function for planar rectangular phased dipole arrays

This paper deals with the construction, physical interpretation and application of a uniform high-frequency representation of array Green’s functions (AGFs) for planar rectangular phased arrays of dipoles. An AGF is the basic constituent for the full-wave description of electromagnetic radiation from large periodic structures. For efficient treatment of high-frequency phenomena, the AGF obtained by direct summation over the contributions from the individual radiators is globally restructured via the Poisson sum formula into a series of propagating and evanescent Floquet waves (FWs) together with corresponding FW-modulated diffracted waves, which arise from FW scattering at the array edges and vertexes. These results are obtained by high-frequency uniform asymptotics applied to the wave integrals generated by Poisson summation in the spatial or spectral domains. The final algorithm is physically appealing, numerically accurate, and efficient, owing to the rapid convergence of both the FW series and the series of corresponding FW-modulated diffracted fields away from the array plane. The use of the asymptotic AGF in the full-wave analysis of large slot arrays is discussed, with the inclusion of numerical results.

Asymptotic high‐frequency Green's function for a planar phased sectoral array of dipoles

This paper deals with the derivation and physical interpretation of a uniform high‐frequency Green's function for a planar right‐angle sectoral phased array of dipoles. This high‐frequency Green's function represents the basic constituent for the full‐wave description of electromagnetic radiation from rectangular periodic arrays and scattering from rectangular periodic structures. The field obtained by direct summation over the contributions from the individual radiators is restructured into a double spectral integral whose high‐frequency asymptotic reduction yields a series of propagating and evanescent Floquet waves (FWs) together with corresponding FW‐modulated diffracted fields, which arise from FW scattering at the array edges and vertex. Emphasis is given to the analysis and physical interpretation of the vertex diffracted rays. The locally uniform asymptotics governing this phenomenology is physically appealing, numerically accurate, and efficient, owing to the rapid convergence of both the FW series and the series of corresponding FW‐modulated diffracted fields away from the array plane. A sample calculation is included to demonstrate the accuracy of the asymptotic algorithm.

Frequency-domain Green's function for a planar periodic semi-infinite phased array .I. Truncated floquet wave formulation

This two-part sequence deals with the derivation and physical interpretation of a uniform high-frequency solution for the field radiated at finite distance by a planar semi-infinite phased array of parallel elementary electric dipoles. The field obtained by direct summation over the contributions from the individual radiators is restructured into a double series of wavenumber spectral integrals whose asymptotic reduction yields a series encompassing propagating and evanescent Floquet waves (FWs) together with corresponding diffracted rays, which arise from scattering of the FW at the edge of the array. The formal aspects of the solution are treated in the present paper. They involve a sequence of manipulations in the complex spectral wavenumber planes that prepare the integrands for subsequent efficient and physically incisive asymptotics based on the method of steepest descent. Different species of spectral poles define the various species of propagating and evanescent FW. Their interception by the steepest descent path (SDP) determines the variety of shadow boundaries for the edge truncated FW. The uniform asymptotic reduction of the SDP integrals, performed by the Van der Waerden (1951) procedure and yielding a variety of edge-diffracted fields, completes the formal treatment.

Antenna Array Pattern Synthesis in the Presence of Near-Zone Scatterers: Three-Dimensional Vector Case

A method for the array pattern synthesis in the presence of near-zone scatterers in the three-dimensional vector case is presented. The synthesis is based on the minimization of an objective function using the simulated annealing technique. In order to take into account the effects of the scatterers, the physical optics approximation is used. The polarization in both the incident and the scattered fields is also taken into account. Examples for a 10 x 10-element planar array of dipoles in the presence of a perfectly electric conducting cylinder are presented.

Analysis of coupling between a curved FSS and an enclosed planar dipole array

Interaction between an antenna and an enclosing FSS is investigated using the Pocklington equation approach from an earlier study of arbitrarily curved free-standing arrays of dipoles. Part of such a collection of elements can be regarded as a receiving antenna, and the rest can be distributed around it to form a dichroic enclosure. It is then possible to analyse this structure with and without mutual coupling between the two sets of dipoles, to give an indication of antenna-radome coupling in a simple case.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Correction: Incompleteness of periodic moment method

It was previously shown by the author (see ibid., vol. 29, no. 14, p.1245-6, 1993) that the periodic moment method (PMM) predicts the correct impedance between a dipole in a planar array of dipoles with rectangular lattice, and a single dipole in a parallel plane, when the single dipole is also parallel to the array dipoles. Also it was asserted that when the single dipole was inclined the PMM results were incorrect; a correct formula for perpendicular dipoles was presented. S. Schneider of the USAF Wright Laboratories has shown how a correct formulation for the parallel plane PMM case can be obtained, and that a coding error of a missing factor of 2 was made by the author for the limiting case of mod alpha mod =1. Now the calculated results agree with those the author calculated using the Richmond piecewise sinusoidal code. >

A planar dipole array antenna with an elliptical lens

AbstractWe describe a planar antenna structure consisting of two half‐wave dipoles, which are backed by a metallic reflector to create an image of two more elements. The array produces rather a wide main beam, and is therefore used with a dielectric lens. The far‐field pattern of the dipole liens antenna has cross‐pol better than −20 dB, and side lobes below −13 dB over an octave band. The impedance at the feedpoint of the antenna is approximately 70 ‐ j10 Ω at the center of the band.

A microwave printed planar log-periodic dipole array antenna

A microwave printed planar log-periodic dipole array (LPDA) antenna analysis and design procedure is presented together with the description of a planar feeding technique. The effects of the dielectric substrate on the antenna design are also discussed and taken into account. A numerical technique using the finite element method is employed to obtain the characteristic impedance and effective dielectric constant of the transmission lines involved, i.e., an unbalanced stripline and a balanced line having only two parallel strips. A 4-8 GHz printed LPDA antenna was manufactured and tested, showing very good radiation pattern and voltage standing-wave ratio (VSWR) values over the entire frequency range.

Thermal desorption mass spectrometry of alkali metal atoms from transition metal surfaces. The influence of coadsorbed oxygen

The coverage dependence of the activation energy of desorption for a planar array of electrical dipoles has been calculated in order to understand thermal desorption traces of alkali metal atoms from transition metal surfaces. The successful comparison between the computed spectra and available experimental data for K/Fe(110), K/Fe(100), K/Fe(polycrystalline), and K/Pt(111) allows us to demonstrate that the mutual dipolar repulsion within the adlayer is responsible for the coverage dependence of the thermal desorption spectra (TDS) characteristic of the above mentioned systems. Shifts of the TDS peaks up to about 450 K due to the lowering of ∼50% in the energy of desorption are well described by the proposed model. Based on these results a simple and accurate method to assess the coverage dependence of the desorption energy is presented. The coadsorption of electropositive and electronegative atoms has been modeled assuming a planar array of electrical dipoles of opposite directions. It is demonstrated that oxygen atoms substantially reduce the repulsion energy on the alkali adlayer which becomes thermally stabilized in agreement with published experimental results. In fact, for the systems K+O/Fe(polycrystalline) and K+O/Pt(111) the onset of K desorption is found to be shifted by about 200 K due to the presence of coadsorbed oxygen atoms.

Substrate-related effects on the optical behavior of a granular surface: The Maxwell Garnett theory revisited

An approximate treatment, describing the influence of a dielectric substrate on the optical behavior of a granular surface, is reported. It shows that discrepancies between experimental results and predictions mainly based upon the Maxwell Garnett theory [Philos. Trans. R. Soc. London 203, 385 (1904); 205A, 237 (1906)] cannot be interpreted as substrate-related effects. The magnitudes and locations of the multiple images of the unperturbed dipole of a small metallic sphere have been carried out in an approximate, though reliable, way in the presence of polarizing fields both parallel and perpendicular to the substrate. The resulting dipole is introduced in a long-known optical model, describing a granular surface as a planar array of equal dipoles interacting with each other. Graphical results, showing the influence of substrates of various dielectric constants, are presented. A discussion of possible improvements of the available model is also reported.