Array Element Pattern Research Articles

A sidelobe level control algorithm for wide-beam power gain pattern synthesis via array antenna

The paper tries to maximize the minimum power gain in a wide-beam mainlobe with a controllable peak sidelobe level (PSLL) by solving the power gain pattern synthesis (PGPS) problem. Since the PGPS problem is nonconvex, it cannot be solved effectively in polynomial time. In this paper, the nonconvex PGPS problem is simplified by converting it into two nonconvex subproblems. The first subproblem's solution space is divided into a finite set of smaller spaces in which the solution has a closed-form, resulting in the subproblem being pseudo-analytically solvable. The second subproblem's solution can be rapidly obtained with a bisection searching strategy. In such a way, the original problem can be solved effectively by iteratively solving these two subproblems. Another advantage of the proposed algorithm is that its convergence is theoretically guaranteed and the PSLL is strictly controllable. Numerical examples with both isotropic element pattern (IEP) array and active element pattern (AEP) array are simulated to validate the effectiveness and superiority of the proposed algorithm by comparing it with the existing algorithms.

Phased Array Calibration Based on Measured Complex Signals in a Compact Multiprobe Setup

Phased array calibration is typically carried out in plane-wave conditions, which requires expensive far-field setups. This letter presents a novel phased array calibration method based on measured complex array signal, which works in the cost-effective compact testing setup. The basic principle is to employ multiprobe antennas in a short measurement distance such that we can effectively retrieve the array element patterns in the boresight direction based on the recorded complex signals at the multiple probes using the interpolation technique. Both theoretical derivations and measurement validations are provided to demonstrate the effectiveness of the proposed method.

Geochemical constraints on mantle source nature and recycling of subducted sediments in the Sulu Sea

The Sulu Sea is a marginal spreading basin in the triple junction of Euro-Asia/Indian/Pacific plates. The genesis of seafloor basalts is crucial for understanding the nature and evolution history of the underlying mantle in this region. Nevertheless, the mantle source of the Sulu Sea remains unclear due to limited geochemical data. In this study, we report a complete set of whole-rock major and trace elements and Sr-Nd-Pb-Hf isotopes for the volcanic rocks at Ocean Drilling Program Site U768 in the Southeast Sulu Sea. These volcanic rock samples are characterized by transitional trace element compositions between mid-ocean ridge basalts (MORBs) and island arc basalts (IABs). A subduction modified depleted mantle source is indicated by their higher Th/Yb ratios than the MORB-OIB array and trace element patterns. We propose that the pelagic sediments contributed to the mantle source of the Southeast Sulu Sea based on the plots of 206Pb/204Pb vs. Ce/Pb and Th/Nb. Based on the decoupled Hf–Nd isotopes and the variation of Pb isotopes for Site U768 volcanic rocks, we suggest that subducted pelagic sediments contributed to the origin of the Indian-type mantle of the Southeast Sulu Sea.

Rapid Test Method for Multi-Beam Profile of Phased Array Antennas.

The measurement of the phased array antenna (PAA) is completely different from the traditional antenna, due to its multi beam patterns. Usually, each beam pattern of the PAA needs a separate measurement, which makes the overall time extremely long. Thus, the traditional method can no longer meet the efficiency and cost requirements of new PAA measurement. In this paper, a pattern reconstruction method is proposed which significantly reduce the measurement time of multi-beam PAAs. With the known array element patterns (AEP) and theoretical weighted port excitation of the beams, any beam pattern can be predicted by measuring only a certain beam pattern, due to the element excitation coefficient (including the matching, mutual coupling, and manufacturing factors, etc.) of the specific PAA being calculated. The approach has low reconstruction error in term of beam pointing accuracy, side lobe, and co-polar and cross-polar patterns while being validated for large scanning range. Through theoretical derivation and experiments, the effectiveness of the method is verified, and the testing efficiency of the phased array antenna can be improved by 10 times or even more.

A Dual-Polarized 27 dBi Scanning Lens Phased Array Antenna for 5G Point-to-Point Communications

A dual-polarized 4×4 scanning phased array antenna with leaky-wave enhanced lenses operating at 28 GHz is presented. Such an antenna can be used for point-to-point fifth-generation (5G) communications that require high gain, wide bandwidth (BW), and limited steering ranges. The proposed array has a periodicity of two wavelengths, and the resulting grating lobes are suppressed by directive and steerable array element patterns. To achieve a low-cost and low-profile solution, the leaky-wave antenna feeds are designed in printed circuit board and the lenses are made of plastic. The lenses are optimized in the near-field region of the feeds, with the goal of maximizing the array element aperture efficiency. The array performance obtained from the proposed approach is validated by full-wave simulations, showing a 27.5 dBi broadside gain at 28 GHz and a steering capability up to ±20° with 2 dB of scan loss. An antenna prototype was fabricated and measured. Measurement results are in excellent agreement with full-wave simulations. The prototype antenna, at broadside, achieves a 20% relative BW and a gain of 26.2 dBi.

Taylor Expansion and Matrix-Based Interval Analysis of Linear Arrays With Patch Element Pattern Tolerance

In this study, a novel interval analysis (IA) approach for linear arrays with element pattern tolerance is proposed. This study differentiates itself from the classic interval analysis (CIA) method because it focuses on the effects of the array element (e.g., patch) pattern tolerance on the antenna array pattern; the tolerance may be caused by fabrication errors in the element. The closed-form pattern expressions of the element (e.g., patch) and array are deduced by the interval arithmetic method. To mitigate the interval extension (also referred to as the overestimation problem) caused by the dependency problem, Taylor expansion and matrix-based interval analysis (TMIA) methods are proposed and implemented in this study. A set of numerical examples is reported and analyzed to indicate the effectiveness of the proposed TMIA approach with the results of Monte Carlo (MC) and CIA methods, as well as to indicate its potential capabilities and advantages in the actual application of industrial antenna arrays.

Dual-Beam Periodic Leaky-Wave Antenna With Reduced Beam Squinting

In this letter, a dual-beam periodic leaky-wave antenna with a low beam-squinting character is presented. It has a simple and low-profile configuration, which consists of 15 slot radiating elements and one microstrip feedline. The slot radiating element creates nulls in the pattern at forward and backward endfire. By properly arranging the radiating elements with a small separation, the higher order spatial harmonics are suppressed. Fed by an air-substrate microstrip line working on the non-dispersion transverse electromagnetic (TEM) mode, the antenna has a moderate phase constant leading to a stable endfire array factor. By integrating the almost unchanged array factor and element pattern, the dual-beam radiation pattern with reduced beam squinting is obtained. To verify the design strategy, a prototype was designed, fabricated, and measured. Over the operating bandwidth from 2.7 to 3.2 GHz, the antenna exhibits a small measured beam squint of 6.8°.

A wideband digital polarization synthesis method

A novel wideband digital polarization synthesis method is presented here. The method is based on the definition of antenna polarization and both simulated and measured antenna patterns. A mathematical formulation is used to determine the synthesis coefficients. Any state of polarization (elliptical, circular, and linear) can be synthesized theoretically. Here, we mainly focus on the method for synthesizing linearly polarized antennas into circularly polarized antennas. There is no restriction regarding the array geometry or element patterns. The method can yield pure circularly polarized antenna patterns within the whole working band. The synthesized circularly polarized antennas are then used to receive circularly polarized signals. The method can provide more accurate polarized data for wideband solar radio observations and other systems that require accurate polarization measurements.

Ninja array antenna: novel approach for low backscattering phased array antenna

This study presents a novel concept of a low backscattering phased array antenna, a Ninja array antenna. One of the advantages of the Ninja array antenna over the conventional phased array antenna is low backscattering performance over its operating frequency band, which is not available using a conventional phased array antenna with a band-pass radome. The Ninja array antenna is designed in the same manner as the design of reflectarrays, so that the main lobe of its scattering field is directed to a specific direction except for backscattering one. As a result, its backscattering is reduced in comparison with that of the conventional phased array antenna. Although the Ninja array antenna is composed of non-identical array elements such as the reflectarray, it works as a phased array antenna because desired amplitude and phase of excitation can be obtained numerically via an array element pattern. Numerical simulation is performed and the scattering/radiation performance of the Ninja array antenna is demonstrated.

On edge melting under the Colorado Plateau margin

AbstractAsthenosphere beneath the relatively thin lithosphere of the Basin and Range province appears to be juxtaposed in step‐like fashion against the Colorado Plateau's thick lithospheric keel. Primary to near‐primary basalts are found above this edge, in the San Francisco‐Morman Mountain volcanic fields, north central Arizona, western USA. We show that at least two distinct peridotite‐dominated mantle end‐members contributed to the origin of the basalts. One has paired Nd and Hf isotopic characteristics that cluster near the mantle array and trace element patterns as expected for melts generated in the asthenosphere, possibly in the presence of garnet. The second has isotopic compositions displaced above the εHf ‐ εNd mantle array which, together with its particular trace element characteristics, indicate contributions from hydrogenous sediments and/or melt (carbonatite or silicate)‐related metasomatism. Melt equilibration temperatures obtained from Si‐ and Mg‐thermobarometry are mostly 1340–1425°C and account for the effects of water (assumed to be 2 wt.%) and estimated CO2 (variable). Melt equilibration depths cluster at the inferred location of the lithosphere‐asthenosphere boundary at ∼70–75 km beneath the southwestern margin of the Colorado Plateau but scatter to somewhat greater values (∼100 km). Melt generation may have initiated in or below the garnet‐spinel facies transition zone by edge‐driven convection and continued as mantle and/or melts upwelled, assimilating and sometimes equilibrating with shallower contaminated mantle, until melts were finally extracted.

A Computer-Aided Technique for the Analysis of Embedded Element Patterns of Cylindrical Arrays [EM Programmer's Notebook

A computer-aided technique is proposed to obtain the embedded characteristics of the elements in a cylindrical phased array using a unitcell approach in Ansys High Frequency Structure Simulator (HFSS). The proposed technique is general and can be used with other commercially available electromagnetic (EM) products that support periodic boundary conditions. Therefore, it can be widely adopted by engineers and researchers to analyze arbitrary element structures in cylindrical phased arrays. The implementation of the technique is discussed in detail, and the related formulation is presented. The method is verified by comparing its results with published literature as well as results obtained through full-wave analysis of a ring of microstrip patch antennas in HFSS.

Grating Lobe Suppression with Element Count Optimization in Planar Antenna Array

The novel approach of this paper describes the suppression of grating lobe level with the element count optimization in planar antenna array. Rectangular lattice (RL) and triangular lattice (TL) structures are chosen for determining the achievable array element patterns (EP) and further suppressing the grating lobe level. The element spacing and number of elements (10 × 20 array) are taken into account for particular lattice. Grating lobe peaks are observed for the 200-element planar array at maximum scan angle (θ) with the set frequency of 3 GHz. Further, it is found that 14°; bore sight elevation of rectangular lattice produces a transformed field of view, which permits a reduction in element count of 20.39% compared with 10° bore sight elevation. Finally, the typical values of elevation, element count and array size (25 cm2) are trained using artificial neural network (ANN) algorithm and element count is predicted after testing the network. The network shows a high success rate.

On the Forming of Orthogonal Beams by Planar Array Antennas

A general approach to determination of geometrical parameters of planar array antennas designed for forming of orthogonal beams steered in the nodes of a Cartesian periodic lattice specified in the space of direction cosines is proposed. The proof of orthogonality of the complex amplitude distributions and appropriate array factors for the arrays constructed according to the proposed approach is given. The role of the array element patterns in providing the beam pattern orthogonality is underlined. The issue of the number of the array elements necessary for forming of the specified number of beams is discussed. A few demonstrative examples of the beam clusters and appropriate configurations of the arrays where the number of the elements is equal to the specified number of the beams are considered.

Optimal polarised pattern synthesis of wideband arrays via convex optimisation

The digital wideband arrays with data converters and digital signal processing capability permit greater flexibility in the pattern synthesis than conventional time-delay steered wideband arrays, which provides an opportunity to solve the polarised pattern synthesis of wideband arrays by using numerical optimisation algorithms. A finite-impulse response (FIR) filter is placed at each element to directly optimise the synthesised polarisation and wideband power patterns. Both the optimisations of the sum and difference patterns are formulated as convex programming problems to obtain efficient solutions. The proposed synthesis method, which has no special requirement on the array geometry and element pattern, is flexible and applicable to arbitrary arrays. By optimising the complex coefficients of FIR filters, any state of polarisation can be synthesised in a given angle-frequency space with frequency-invariant main beams and arbitrary sidelobe upper bounds. Various design examples are presented to testify the potentiality of the proposed method.

Optimal Difference Pattern Synthesis With Polarization Control for Arbitrary Arrays

This letter proposes an optimal difference pattern synthesis with polarization control ability for arbitrary arrays. The joint synthesis of the polarization and spatial power patterns are formulated as a convex optimization form that can be efficiently solved by existing numerical methods. The proposed synthesis method, which has no limitation on the array geometry and element pattern, is flexible and applicable to arbitrary arrays. Two typical examples, the linear arrays for circular polarization synthesis and the cylindrical arrays for elliptical polarization synthesis, are presented to testify the potentiality of the proposed method.

Optimal Polarization Synthesis of Arbitrary Arrays With Focused Power Pattern

The joint synthesis of the spatial power pattern and polarization of arbitrary arrays is addressed. Specifically, the proposed approach gives the solution to a frequently encountered problem, namely the array design (i.e., the determination of the radiating element weightings) to achieve a pattern that is arbitrarily upper bounded, while its polarization is optimized in a given angular region. Any state of polarization (elliptical, circular and linear) can be synthesized and there is no restriction regarding the array geometry and element patterns. The synthesis problem is rewritten as a convex optimization problem, that is efficiently solved using readily available software. This ensures the optimality of the proposed solution. Various numerical results are presented to validate the proposed method and illustrate its potentialities. The synthesis of a sequentially rotated array is first addressed. Then a linear array of equispaced randomly oriented dipoles is considered. Finally, a conformal and a planar array of patches, where the mutual coupling effects are considered, are synthesized to radiate a linear and a circular polarization.

Design and Characterization of an Active Impedance Matched Low-Noise Phased Array Feed

An L-band low-noise phased array feed antenna was designed, fabricated, and characterized experimentally. The element design was optimized for an active impedance matching condition with a given set of nonuniform amplitude beamformer coefficients associated with a formed PAF beam. Using measured array S-parameters and modeled array element patterns, the predicted boresight beam equivalent system noise temperature and aperture efficiency at prime focus with uncooled low-noise amplifiers were 42 K and 61% at 1600 MHz. Experimental measurements of receiver noise using an array Y-factor technique matched modeled predictions. The array feed was mounted on the Arecibo radio telescope for on-reflector characterization. The measured boresight beam sensitivity figure of merit (Tsys/ηap) was 88 K and the 1 dB sensitivity bandwidth was 450 MHz.

Multiobjective Optimization of Real and Coupled Antenna Array Excitations via Primal-Dual, Interior Point Filter Method From Spherical Mode Expansions

A novel method for the multiobjective optimization of arbitrary planar array excitations is presented. The optimization problem formulation, which inherently takes into account every array element pattern as well as all interelement couplings, is based on matrix-valued functions which are computed from the generalized-scattering-matrix characterization of an array and spherical mode expansions of its radiated field. It allows the maximization of the directive gain subject to a maximum sidelobe level, a maximum crosspolar level and a minimum aperture illumination efficiency, the setting of null-pointing directions and the dynamic range control. To solve the resulting non-linear optimization problem, we have developed a primal-dual interior point method specifically adapted to the presented formulation, which makes use of novel filtering techniques. Numerical examples of arrays of microstrip patches and dielectric resonator antennas covering a wide variety of requirements on these parameters are presented.

Experimental Study on MUSIC-Based DOA Estimation by Using Universal Steering Vector

MUSIC-based estimation of direction of arrival (DOA) using universal steering vector (USV) is experimentally studied. A four-element array antenna and a four-channel receiver are employed for the experiment. In order to improve the accuracy of DOA estimation, USV which has already included the effect of mutual coupling between array elements and effect of array elements themselves is compensated to further include the electric delay and loss of four channels in the receiver. The compensated USV (C-USV) approach proposed in this paper does not need the time-consuming measurement of array element pattern because the compensating matrix for USV is obtained by measuring the S parameters between RF input ports of the feeding cables and IF output ports of the receiver. The experimental results of MUSIC-based DOA estimation show that C-USV approach is an accurate, effective and practical method for the MUSIC-based DOA estimation.

WIDE SCANNING PHASED ARRAY ANTENNA USING PRINTED DIPOLE ANTENNAS WITH PARASITIC ELEMENT

A active phased array antenna has been developed that is capable of wide scanning angle with small deviation in antenna gain using printed dipole antennas with parasitic element, which may have the capability of adjusting the influence of mutual coupling in the array element pattern. The design of the parasitic element is examined and the effect of its shape on pattern characteristics is confirmed. Beam scanning angles of 58 degrees in the φ = 0◦ plane were obtained for each array antenna pattern.