Infinite Array Environment Research Articles

A Wide-Scanning Array Antenna of Connected Vertical Bowtie Elements Structurally Integrated Within an Aircraft Fuselage

A low-profile, wide-scanning phased-array antenna of vertical bowtie elements fully integrated with a structurally efficient radome and ribs of an aircraft fuselage is proposed in this paper. The array is designed to simultaneously fulfil the electrical requirements of an airborne antenna sensor and the mechanical requirements of a load-carrying aircraft fuselage. The array antenna is capable of steering the beam up to ±80° in the azimuth plane over a 20% bandwidth (2.4 GHz to 3 GHz) with the active reflection coefficient (Γ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>act</i></sub> ) below –10 dB in an infinite array environment. Experimental results of a 16×16 element array demonstrator agree well with the simulation results. The 16×16 array antenna is capable of steering the beam up to ±60° and ±75° with the bandwidth of 20% and 10%, respectively at Γ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>act</i></sub> ≤ –10 dB. The array antenna also achieved good stiffness and performed well in the vibration loads of commercial transport aircraft.

A UWB Low-Profile Hemispherical Array for Wide Angle Scanning

We report the first low-profile array on a doubly curved surface that supports wide angle electronic scanning and ultrawide bandwidth (7:1 ratio). The array elements are based on the balanced antipodal Vivaldi antenna (BAVA). The antennas are optimized for a good impedance match in an infinite planar array environment and are then deformed to fit along the surface of a hemisphere. The array is comprised of 104 linearly polarized BAVA elements arranged along a quadrilateral mesh on the surface of a 100 mm diameter hemisphere. The antennas and SMP connectors are 3-D printed out of titanium. The array has grating lobe-free operation at frequencies < 8 GHz. The array can also maintain relatively low sidelobe levels above 8 GHz compared with planar arrays because the aperiodicity of the hemispherical element locations reduces the magnitude of grating lobes. The simulated and measured realized gain is within 1 dB of the theoretical limit from 2.5–18 GHz and scan angles with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta \le {\mathrm {90}}^{\circ }$ </tex-math></inline-formula> except near 14 GHz where a resonance reduces the gain by 3 dB for some scan angles.

Scan-Angle-Independent FEM Analysis of Infinite Arrays Based on Spherical Harmonic Lattice Sums and the Generalized Scattering Matrix of an Isolated Antenna

Infinite periodic arrays of antennas that can be individually described by means of spherical modes are analyzed starting from the generalized scattering matrix (GSM) of an isolated element. After computing the GSM of an isolated element with the finite-element method (FEM), a fast postprocessing can be carried out to calculate the response of the element in an infinite array environment by using addition theorems for spherical modes. For this purpose, an efficient computation of lattice sums of spherical harmonics is used. The main advantage of this method is that the antenna is analyzed only once whatever the array lattice or scan angle. In addition, fast frequency analysis can be performed since the starting point is the computation of the isolated antenna with the FEM, which is suitable for fast frequency sweep. The active reflection coefficient and the embedded radiation pattern of the infinite periodic array are calculated for several examples to show the capabilities of the proposed method.

Corporate-Fed Planar 60-GHz Slot Array Made of Three Unconnected Metal Layers Using AMC Pin Surface for the Gap Waveguide

This paper presents the design of a high efficiency corporate-fed 8×8-slot array antenna in the 60 GHz band. The antenna is built using three unconnected metal layers based on Artificial Magnetic Conductor (AMC) in gap waveguide technology. A 2×2 cavity-backed slot subarray is designed in a groove gap waveguide cavity. The cavity is fed through a coupling slot from a ridge gap waveguide corporate-feed network in the lower layer. The subarray is numerically optimized in an infinite array environment. The corporate-feed network is realized by a texture of pins and a guiding ridge. There is very good agreement between simulated and measured results. The fabricated antenna shows a relative bandwidth of 14% with input reflection coefficient better than -10 dB and an overall aperture efficiency larger than 65% (i.e. – 2 dB) with about 25 dBi realized gain between 56.2 and 65.0 GHz.

2&lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$\times$&lt;/tex&gt; &lt;/formula&gt;2-Slot Element for 60-GHz Planar Array Antenna Realized on Two Doubled-Sided PCBs Using SIW Cavity and EBG-Type Soft Surface fed by Microstrip-Ridge Gap Waveguide

A wideband 2x2-slot element for a 60-GHz antenna array is designed by making use of two double-sided printed circuit boards (PCBs). The upper PCB contains the four radiating cavity-backed slots, where the cavity is formed in substrate-integrated waveguide (SIW) using metalized via holes. The SIW cavity is excited by a coupling slot. The excitation slot is fed by a microstrip-ridge gap waveguide formed in the air gap between the upper and lower PCBs. The lower PCB contains the microstrip line, being short-circuited to the ground plane of the lower PCB with via holes, and with additional metalized via holes alongside the microstrip line to form a stopband for parallel-platemodes in the air gap. The designed element can be used in large arrays with distribution networks realized in such microstrip-ridge gap waveguide technology. Therefore, the present paper describes a generic study in an infinite array environment, and performance is measured in terms of the active reflection coefficient S11 and the power lost in grating lobes. The study shows that the radiation characteristics of the array antenna is considerably improved by using a soft surface EBG-type SIW corrugation between each 2x2-slot element in E-plane to reduce the mutual coupling. The study is verified by measurements on a 4x4 element array surrounded by dummy elements and including a transition to rectangular waveguide WR15.

Simple model for the parametric analysis of grid amplifiers

A simple method for parametric analysis of grid amplifier performances is presented here. The proposed approach is based on the development of an equivalent transmission line model where each element of the grid is represented by an S-matrix derived from a full-wave simulation in an infinite array environment. The proposed technique makes it possible to investigate the dependency of grid amplifier performance on its major parameters taking into account the actual geometry of each part of the circuit while preserving the simulation efficiency.

Miniaturized rectangular hard waveguides for use in multifrequency phased arrays

The elements of a multiband array need to be small to allow elements of other frequencies to be interlaced over the same array aperture. This paper investigates the use of miniaturized open-ended partially dielectric-loaded hard-walled rectangular waveguides for this purpose. Apart from studying its modal properties, we seek to find out how it performs in an infinite planar array environment. Specifically, we study how the various array parameters affect its radiation characteristics. Comparisons are also made with fully filled waveguides. The waveguides are matched at broadside. The results show a narrow-band solution.

Two-dimensional cylindrical dielectric resonatorantenna array

A square 2 × 2 subarray and infinite phased array of aperture-coupled cylindrical dielectric resonator antennas is investigated experimentally. The return loss, radiation pattern, and antenna gain are studied and compared with those of the single element antenna, and the waveguide simulator is used to measure the return loss of the element in an infinite array environment

Analysis of infinite arrays of substrate-supported metal strip antennas

An electric field integral equation method is applied to a metal strip antenna on an electrically thick dielectric substrate of finite size in a uniform infinite array environment. An efficient solution is found using the method of moments. Metal strip folded dipole antennas are analyzed both with and without a coplanar strip feed line, and the effects of the substrate and feed line are investigated. A technique for minimizing the effect of feed line scattering is presented, and arrays of these elements are shown to be capable of good scanning performance over a wide range of beam-steer angles. A phased array simulator experiment is described and the measured results show good agreement with those obtained by analysis. The class of antenna elements studied may be fabricated using monolithic microwave integrated circuit (MMIC) technology, and the analysis described illustrates the expected characteristics for millimeter-wavelength phased arrays of this type. >

Finite difference solution of infinite arrays of two-dimensional microstrip structures

Infinite arrays of two-dimensional microstrip elements are analyzed using the finite difference method. The method is used to study the behavior of three configurations of planar strips over a dielectric substrate in an infinite array environment. These configurations include the “dipole” element, the “microstrip” element over an inhomogeneous substrate. For each configuration, calculated results are presented with special attention given to antenna characteristics such as input impedance and scan performance. Verification of the finite difference approach for these problems is achieved by comparing its results with those obtained using other methods available in the literature.

Finite difference analysis of infinite arrays of two-dimensional microstrip structures

Infinite arrays of two-dimensional printed elements are analysed using the finite difference method. Grid models accounting for dielectric discontinuities and current continuity at rectangular junctions are developed. The procedure is used to study the behaviour of three configurations of planar strips over dielectric substrates in an infinite array environment. These configurations include the ‘dipole’ element, the ‘microstrip’ element and the ‘microstrip’ element over an inhomogeneous substrate. For each configuration, calculated results are presented with special attention given to the correctness of antenna characteristics such as input impedance and scan performance. The results accurately predict antenna performance and comparison with published data confirms the method.

Linear array of coaxially fed monopole elements in a parallel plate waveguide. I. Theory

The performance of a coaxially fed monopole element is analyzed for an infinite array environment in a parallel plate guide. The analysis takes into account the geometry of the coaxial feed. Expressions for active admittance, coupling coefficients, and element patterns are given. >

Ridged waveguide phased array elements

The mutual coupling solution of dual and quad ridged waveguide is described for an infinite array environment. The method of analysis is the numerical solution of integral equations for both the eigen solution and the boundary matching problem. In addition to numerical results, comparison of theory with waveguide simulator measurements is also given.

Analysis of finite parallel-plate waveguide arrays

An analysis has been carried out to determine the edge effects in finite parallel-plate waveguide arrays. The method used in the evaluation is to compare the element patterns and reflection coefficients versus scan for finite arrays with the corresponding results for hypothetical infinite arrays. It is found that, in arrays of empty waveguides, an element has to be about four or five elements removed from the edge in order to be regarded as being in an infinite array environment. On the other hand, when the waveguides are loaded with dielectric plugs having suitable combination of parameters, considerably more elements are needed for the simulation of an infinite array environment due to the appearance of the resonant null in the array transmission coefficient. It is found, moreover, that even though there may be substantial variation in the radiation properties from element to element in finite arrays, particularly so in the case of moderately sized arrays, this variation does not seem to severely degrade the array performance in terms of beamwidth and sidelobe levels.