Phased-array beam steering by multiplex sampling

One approach to phased-array antenna beam forming and steering is to multiplex the element signals into a single channel. Appropriate "sampling" of the resulting multiplexed signal can provide electronically steered and shaped beams. This paper describes four practical system concepts for linear and ring arrays based on this approach and discusses significant interrelationships between the various concepts. For linear arrays of elements, the two alternatives are to frequency or time multiplex the element signals. Frequency multiplexing of the element signals produces time-multiplexed beam output signals, and time multiplexing the element signals produces frequency-multiplexed beam output signals. It is also shown here that appropriate correlation "sampling" may be used with either of these to produce easily one or more continuously and electronically steered signal bandwidth beam outputs. Ring arrays of elements may be multiplexed and "sampled" in a somewhat analogous pair of techniques. It is also pointed out that the beam steering in this case may be visualized as the linear phase steering of a set of linear phase modes into which the signal received at the array may be resolved. Ring array beam forming and steering may thus be directly understood in terms of the previous linear array techniques.     

Microstrip active path array with beam scanning

A four-element microstrip active path array with beam scanning is described consisting of locked path oscillators with DC bias phase control. The radiating elements are formed by transistor oscillators whose frequency is controlled by a rectangular patch. The oscillators are locked to an external source. Control of the radiated phase is achieved by varying the bias on the transistor. Close to 360 degrees of radiated phase control can be achieved from each element by locating two oscillators on each patch. Measured results indicate that beam scanning in excess of 40 degrees can be achieved.<>     

Synthesis of a laterally displaced cluster feed for a reflector antenna with application to multiple beams and contoured patterns

When a feed is displaced from the focus of a reflector, phase distortion results in the effective aperture distribution, which in turn gives rise to secondary beam distortion. In multiple beam or contour beam antennas, the feed normally consists of an array of identical elements located on a triangular lattice. Taking advantage of this arrangement, a "cluster" of feed elements instead of a single element may be used to control each beam. By adjusting the relative excitations of the elements in a cluster, the aperture phase distortion due to the feed displacement may be partially compensated. Two general methods for synthesizing the excitations for a laterally displaced feed cluster are presented. In the first method the excitations are chosen to minimize the weighted phase error in the effective aperture by analytical means. The second method determines the excitations by a gradient optimization algorithm which minimizes the weighted error between an objective and the actual power patterns in the secondary pattern space. The first method is roughly two orders of magnitude more efficient computationally than the gradient optimization algorithm, but not as flexible in application or as precise. Numerical results are presented for cluster feed designs and their application to the synthesis of contour patterns.     

Feed network for dual beam reflector antennas

A primary feed network for doubly curved shaped-beam reflector antennas is described which allows simultaneous signal reception on two distinct elevation plane patterns such that the underside falloff separation between a fixed lower beam and a higher beam can be substantially varied in a lossless manner. A three-element feed array is employed wherein two elements of the array are interconnected by means of a sum-difference hybrid. The sum port generates the fixed low beam while the difference port generates an orthogonal beam pattern suitable for RF combining with an independent high beam generated by the third array element. Adjustment of the combining amplitude and phase relationships permits the variation of the underside falloff separation. The fixed low beam is, of course, also used for transmission at high power. Design parameters for a typical surveillance radar application axe discussed for a linearly polarized case. Calculated antenna patterns and free-space coverage diagrams are presented. The complexities of extending the feed network concept to handle switchable linear/circular polarization cases and an integral directional beacon pattern for L band systems are indicated.     

A systematic design formulation for Butler matrix applied FFT algorithm

A systematic general design formulation for a Butler matrix (Bmatrix) is described. TheBmatrix design problem discussed is used to determine phase shift location and value in a matrix, when the number of beam (elements of array)M = 2^{N}and the scattering matrix for the hybrid couplers are specified. The design formulation presented is based on the fact that aBmatrix design procedure and an FFT algorithm are equivalent in fundamental concepts. It is shown that theBmatrix design procedure can be systematically formulated by the FFT algorithm modifications, which preserves the topological properties of the original signal flow diagram. A simple design formula has been established by this formulation.     

基于时域调制反射阵列的波束赋形技术

传统的反射阵利用相控器件与微带线实现波束赋形。为了降低相控成本与系统复杂度,提出基于时域调制阵列波束赋形技术。时域调制反射阵列是一种基于简单可重构反射单元的反射阵,它利用控制可重构反射单元的开与关,达到控制阵列输出,实现旁瓣抑制、波束赋形等功能。通过理论推导及仿真,结果表明,时域调制反射阵可以在不采用传统阵列中的相控器件及馈电网络的前提下,采用最小方差无失真响应波束赋形方法与时间调制法,生成理想的方向图,实现波束赋形功能。此特性将有利于推广波束赋形技术在毫米波频段反射阵的应用。     

A Novel Implementation Technique of Conical Scan Radar Using A Programmable Phased Array

In radar, planar phased array antenna plays vital role in electronic scanning in the azimuth and elevation direction to the horizon. In most operations using planar phased array both the coordinates of azimuth and elevation, are steered electronically. In this paper a conceptual schematic of a phased array antenna with programmable time delay units has been presented. It is shown that by suitably exploiting the time delay matrix one can have electronic beam rotation around the target axis as required in conical scan. Thus both the elevation and azimuth motors in conical scan system are replaced by electronic scanning. Heuristically, we have selected eight consecutive points for beam rotation in a polygon shape and can also be extended almost circular shape by increasing number of array elements and phase shifter (delays) in the delay matrix. The array requires dual control of phase gradient and individual phase values. The whole array is controlled by micro-controller. This presents exciting possibilities in radar operation.     

Measurement and modeling of a microwave active-patch phased arrayfor wide-angle scanning

An active antenna consisting of an integrated oscillator with a passive radiator has been arrayed and beam-scanned using a new principle for phase shifting. The radiating elements consist of a transistor oscillator whose frequency is controlled by a rectangular microstrip patch antenna. Each oscillator is injection locked to an external source. The phase control of the radiated wave is achieved by varying the bias on the transistor. Individual element performance has been characterized for potential use as an array element and is comprehensively reported. Methods used to achieve configurations with full 360° phase control have been investigated utilizing novel configurations and cascaded oscillator pairs. Close to 360° of radiated phase control from each element has been achieved. Measured results on an experimental four-element S-band array indicate that beam scanning in excess of ±60° can be achieved. Mutual coupling effects on this new form of array are studied both experimentally and theoretically. A van der Pol (1934) model for the weak coupling that is occurring on the array is developed and used to qualitatively predict the phase offsetting on array elements. Reasonable agreement between theory and experiment is obtained and it is observed that good control of the coupling mechanism is essential to array performance within this new form of active integrated phase shifterless array     

Series-fed circular array

This letter describes how a circular array may be phased to produce a main beam in one direction by feeding the elements from a set of series-connected phase shifts. The direction of the main beam may consequently be varied by control of the values of phase shift. The significant feature of the series-feeding technique is the small phase deviation required per phase changer for 360° beam steering.     

Concept of an interlaced phased array for beam switching

A novel concept is described for feeding and phasing a large linear array of N antenna elements using only three or five feed points and phase shifters and still achieving beam switching. The idea consists of drastically reducing the number of input points by interlacing a small numer of serially fed subarrays which are suitably phased. This so-called interlaced phased array (IPA) concept was tested using an array of 15 four-element Yagi antennas with a spacing equal to 0.8 wavelengths and found feasible. Some of the distinct advantages of the IPA in comparison with a conventional system of beam switching are reduced power loss, reduced phasing errors, reduced cost, increased reliability resulting from greatly reduced number of phase shifters, and better symmetry of off-zenith beams     

Synthesis of spacecraft array antennas for intelsat frequency reuse multiple contoured beams

A method is described for synthesis of planar array antennas where both the amplitude and phase of each radiating element is a design variable. The method improves the computational efficiency of conventional optimization procedures based upon, for example, minimax or least square algorithms. Application of the proposed method demon-strafes the feasibility of spacecraft frequency reuse array antennas with multiple contoured beams for typical Intelsat sixfold frequency reuse requirements. It is demonstrated that repetitive optimization will reduce the number of array elements required. Shifting the array aperture normal toward a beam center will dramatically improve the frequency sensitivity of the beam coverage.     

Beam broadening synthesis for SAR antenna array based on Projection Matrix Algorithm

A new beam broadening synthesis technique for Synthetic Aperture Radar （SAR） antenna array, namely Projection Matrix Algorithm （PMA） is presented. The theory of PMA is introduced firstly, and then the iterative renewed manner is improved to resolve the unbalance problem under amplitude and phase control. In order to validate the algorithm correct and effective, an actual en- gineering application example is investigated. The beam synthesis results of 1.0-4.5 times broadening under the phase only control and the amplitude and phase control using improved PMA are given. The results show that the beam directivity, the beam broadening, and the side-lobe level requirements were met. It is demonstrated that the improved PMA was effective and feasible for SAR application.     

频控阵雷达技术及其应用研究进展

与传统的相控阵只形成方位角依赖性的发射波束不同,频控阵通过在阵元间采用一个小频差来实现波束的自动扫描功能。频控阵能够形成具有距离依赖性和时变性的发射波束,克服了传统相控阵阵列因子不包含距离和时间变量的缺点,因而带来很多独特的应用优势。该文在作者的“频控阵雷达:概念、原理与应用”(《电子与信息学报》,2016, 38(4): 1000–1011)基础上,简要介绍频控阵雷达的基本原理,全面梳理近3年来国内外关于频控阵雷达技术及其应用方面的最新研究进展,讨论几种新的频控阵雷达技术应用前景,主要包括雷达对抗和雷达-通信一体化应用,并指出目前亟待研究解决的波束时变性、有效接收机设计、自适应信号检测与估计和原理样机研制等几个关键问题。      

A new active phased array antenna for mobile direct broadcastingsatellite reception

This paper represents a new active phase array antenna for a Ku-band mobile service that will be possible with satellite broadcasting. The main idea for the antenna is to use minimum active array elements with cost-effective one-dimensional subarrays with an inclined pencil beam structure for a 34 dBi gain. For this antenna, we also used the squint beam tracking algorithm. This tracking gives a different way to the traditional monopulse tracking method in tracking capability. The electronic scanning angle of the beam peak in this antenna is over ±12° wide only with 20 phase shifter elements for its scan ranges. This antenna with the attractive hybrid-tracking concept has about 142 times less array elements than antennas with a two-dimensional array     

On a simple method of obtaining sidelobe reduction over a wideangular range in one and two dimensions

A patented technique for suppressing the sidelobes of an array antenna is considered. This technique involves the addition of two elements, one at each end of the array, which together produce an interferometer pattern used for the cancellation of sidelobes. It is shown here that the technique is most effective for uniform illumination and that there then exists an optimum fixed position for the added elements. The amplitude of the excitation of the auxiliary elements determines the angular location of the region of sidelobe reduction while the phase of the excitation tracks the beamsteering phase of the array. Thus, this technique is seen to be easily implemented in an array controlled by coupled oscillators. The technique generalizes in a straightforward manner to two-dimensional (2-D) arrays in which case a set of auxiliary elements on the perimeter of the array is required. A 2-D oscillator controlled array of this type is described here with which one can produce a main beam and a sidelobe suppression region that can be independently positioned anywhere in a hemisphere provided they do not coincide     

Scanning of cosecant beams generated by a tilted planar array ofnonisotropic radiators

A method of scanning a one-dimensional shaped pattern generated by a tilted circular planar array of nonisotropic elements is presented. A method of synthesis of phase function for a desired cosecant pattern and specified amplitude distribution for excitation of the elements of the array is presented. The phase distribution required in the perpendicular direction for retaining the beam shape in the scanned plane is determined. Computed results on the phase distribution and radiation pattern are presented. The appropriate correction is applied to get a better agreement between the realized and desired patterns in this scanned position of the beam     

A Self-Steering Two-Dimensional Planar Array for Nonsinusoidal Waves

The principle of a one-dimensional self-steering array system for beam forming with nonsinusoidal waves has been developed previously. In this paper, an adaptive antenna system consisting of a two-dimensional planar array of sensor elements and a real-time adaptive receiver processor is described. The sensor elements of the planar array are arranged into rows and columns so that the steering commands for the azimuth ald elevation directions can be generated separately. The array system electronically steers a beam in the direction of the source from which the waves are arriving without prior knowledge of the source location.     

Experimental evaluation of an array technique for zenith to horizon coverage

An experimental study of a new array concept with application to providing low cost efficient antennas with hemispherical coverage for aircraft to satellite communication links is described. The combined array-surface wave antenna consists of 64 waveguide elements scanned conventionally except at endfire. At endfire the array is shorted to become a corrugated surface-wave antenna and excited by an eight-element feed to provide a directional beam near the horizon. The array is rotated to give hemispherical coverage.     

阵列方向图综合的一些方法

介绍了几种常用的阵列方向图综合方法。切比雪夫阵列在指定的副瓣电平下主瓣宽度最窄,在指定的主瓣宽度下副瓣电平最低;相位控制技术通过控制阵列各单元的相位实现波束的指向变化;最后介绍了遗传算法并利用遗传算法优化了8元线阵,将其相对副瓣电平抑制到了-50dB。