Showing papers on "Reflective array antenna published in 1993"

Active transmit phased array antenna.

Abstract: An active transmit phased array antenna system for generating multiple independent simultaneous antenna beams to illuminate desired regions while not illuminating other regions. The size shape of the regions is a function of the size and number of elements populating the array and the number of beams is a function of the number of beam forming networks feeding the array. All the elements of the array are operated at the same amplitude level and beam shapes and directions are determined by the phase settings. The active transmit phased array antenna includes a plurality of antenna elements disposed in a hexiform configuration. Each antenna element is identical and includes a radiating horn capable of radiating in each of two orthogonal polarizations. The horn is fed by a multi-pole bandpass filter means whose function is to pass energy in the desired band and reject energy at other frequencies. The filter means is coupled into an air dielectric cavity mounted on substrate. The air dielectric cavity contains highly efficient monolithic amplifiers which excite orthogonal microwave energy in a push-pull configuration by probes in combination with amplifiers placed such that they drive the cavity at relative positions 180 degrees apart. Phase shift means and attenuator means in the substrate are connected to the amplifiers in the cavity to determine beam and direction and for maintaining the signal amplitudes from each of the antenna elements at an equal level.

Wide band bunny-ear radiating element

Abstract: A low-cost wideband radiating element for EW (electronic warfare) and radar array antenna applications is reported. This printed end-fire bunny-ear element is fed by a balanced slot line, and it can operate over 0.5 to 18 GHz with very low loss in an isolated environment. The input transition, the feed line, and the launching section of this element are essentially TEM (transverse electromagnetic) structures. The element was scaled and used in an L-band array with 50% instantaneous bandwidth. >

Comparison of three series fed microstrip array geometries

Abstract: The authors describe three different design approaches for series-fed broadside microstrip arrays having a center feed point. The first array uses a standard standing-wave feed design, but with the novel feature that the patch width is varied in order to obtain the desired amplitude taper. The second design also uses patches of varying widths, but the main feed line is designed to be matched at each patch tap point. The third array uses a center-fed feed network with each half of the array designed as a traveling-wave array with a main beam angle slightly off broadside. As a comparative example, the authors have designed and tested a 16-element array with a 22-dB sidelobe level for each of the above designs. Patterns, bandwidth, gain, and directivity have been compared for the three designs. >

Beam space constant modulus algorithm adaptive array antennas

Abstract: A constant modulus algorithm (CMA) adaptive array antenna is based on the fact that interference causes a constant modulus signal to undergo amplitude fluctuations. The authors proposed a beam space CMA (BSCMA) adaptive array antenna. In the BSCMA adaptive array, first, multiple beams are formed in the multibeam former. Next, those beams whose received signals have sufficient level are selected. The weights of only these selected beams are optimized in an adaptive loop. The BSCMA adaptive array antenna is useful in mobile satellite communications, because the number of interferences that need to be considered is smaller than the number of elements. >

Characterization of Vivaldi antennas utilizing a microstrip-to-slotline transition

Abstract: To take maximum advantage of integrated circuit techniques, completely planar geometry should be chosen for tapered slot antennas. This is the reason that the transition used in the present study is microstrip-to-slotline instead of finline to slotline or some other nonplanar transition. The authors investigate the microstrip-to-slotline transition and report on experimental results for Vivaldi antennas of various lengths and output widths. The Vivaldi antennas were designed to operate at 10 GHz and fabricated on Duroid 5870. The directivity in the E- and H-plane for the optimized antenna is shown. The values for the directivity compared favorably to the curves produced by F.J. Zucker (1961) which are the standards for determining whether tapered slot antennas behave as well as optimized traveling-wave antennas. >

Adaptive pattern nulling utilizing the elevations of the antenna array elements

Abstract: The authors describe a simple method for adjusting the elevations of the antenna elements to suppress interferences coming from certain directions. The effect of changing the elevation of the antenna array elements is to add additional phase to the antenna pattern according to the locations of the nulls with respect to the broadside direction. As an illustration, a linear array with N=20 elements and d=/spl lambda//2 is considered. >

Characteristics of stacked rectangular and triangular patch antennas for dual band applications

Abstract: Multi-band antennas have applications in radars and communication systems. For their light-weight low-cost properties, stacked microstrip patch antennas have recently gained increasing support as dual frequency antennas. The paper presents a general technique for the theoretical determination of the input impedances and the radiation patterns of stacked microstrip patch antennas of arbitrary shapes. It then investigates various cases of stacked rectangular and triangular patch antennas. For these antennas, some approximations are introduced in the modelling technique in order to make it efficient on personal computer. The investigations on the stacked rectangular patch antenna focus on antennas with dissimilar substrates, non-aligned patches or unequal patch sizes. The effects of some radomes on the characteristics of the stacked rectangular patch antennas are also included. As far as the stacked triangular patch antenna is concerned, its analysis is presented and its performance is compared against that of the rectangular counterpart. Some experimental results are also reported.

A comparison of switched pattern diversity antennas

Abstract: Switched pattern diversity reception is implemented by using antenna elements with different directional radiation patterns and switching the receiver to the element providing the best output. The use of pattern diversity can improve system performance. The performance of various ideal pattern diversity antennas is simulated. The results are compared with an ideal omnidirectional antenna and with energy density antennas. Significant improvements are shown for diversity antennas in multipath environments characterized by Rayleigh and Rician amplitude distributions.

Compact electromagnetic test range using an array of log-periodic antennas

Abstract: The design of an array of seven log-periodic dipole antennas is described: this is intended to generate an approximate plane wave in the near field The array is used as an illuminating antenna for a compact range primarily intended for electromagnetic susceptibility or emission measurements, but is also potentially usable for antenna measurements It is capable of operation at lower frequencies than reflector antennas, and achieves good-quality plane waves in the near-field region The design procedure was based on a numerical near-field synthesis technique that produced a set of complex excitations for the seven elements The magnitude-only synthesis technique was found to give better results than alternative methods The resulting computed field distributions showed that acceptable approximations to a plane wave could be generated over a substantial quiet zone, and an experimental test of an array constructed in accordance with the design algorithm showed good agreement with the predicted performance >

Design of aperture-coupled patch antenna arrays with multiple dielectric layers

Abstract: Using inexpensive foam materials in the design of aperture-coupled patch antennas, large bandwidth and excellent cross polarisation properties can be achieved. This paper shows the mathematical treatment of such antennas using a spectral domain approach and the exact Green's functions for multiple dielectric layers. The performance of a 16 × 16 element array for 12.625 GHz will be demonstrated.

Microstrip patch array for an active SAR demonstrator

Abstract: Reviews the development work carried out on the antenna for a microstrip patch array operating at 5300 MHz for an active SAR antenna. The work, carried out by Matra Marconi Space, covers the initial design leading up to the present working array. Details of the array and measured results are also presented. >

Antenna device having low side-lobe characteristics

Abstract: There is disclosed an antenna device having low side-lobe characteristics comprising a pair of array antennas having the same construction. Each array antenna has array elements equidistantly arranged. The center-to-center distance between the array antennas is so determined that the angle of the first zero point of the array factor determined by the center-to-center distance equals the angle of the first side lobe point of the pattern of each array antenna. The array antennas are electrically connected so as to become excited in phase.

FLAPS reflector antennas

Abstract: A flat parabolic surface (FLAPS) reflector is a thin (planar or conformal) surface consisting of an array of elements, each functioning as a radiator and phase shifter. Unlike a conventional planar array, however, the elements on the FLAPS surface are spatially fed using a feed assembly, as in a conventional reflector system. This results in an antenna technology that offers the advantages of both planar arrays and reflector systems. Additionally, FLAPS technology offers packaging and deployment ease and is suitable for a variety of manufacturing processes and procedures using low-cost materials. Other features, such as polarization control, large apertures with low windloading, and low-cost electronic beam switching, are also possible. Initially developed for defense microwave and millimeter-wave radar applications, FLAPS antennas are now being developed and fielded in many defense as well as commercial radar and communications systems. >

Antenna patterns for prototype two-dimensional digital beamforming array

Abstract: The US Army Missile Command has conducted experiments on a two-dimensional, C-band, digital beamforming (DBF) array. The 8 /spl times/ 8 array has been tested both as a traditional DBF array and as a feed for a larger microwave lens. The multiple beam capability and flexibility in the beamforming process were demonstrated for both the conventional planar and the space fed configurations during tests on the prototype DBF hardware. >

A low-profile single-layer leaky wave slotted waveguide array for mobile DBS reception

Abstract: The authors propose a low-profile single-layer leaky-wave slotted waveguide array for mobile DBS (direct broadcasting satellite) reception, which is specially designed for a portable TV set. The 52/spl deg/ beam-tilted model antennas with a size of 25 cm by 20 cm and a height of 0.5 cm have been designed and fabricated. The efficiency is 66% in the peak and more than 57% in DBS band. A good axial ratio of 1.0 dB in the main-beam direction and small reflection at the feed point below -17 dB in DBS band have been obtained. The gain is about 24 dBi, which is sufficient for a portable TV set with a liquid-crystal screen. >

Phased-array-antenna control using liquid crystals

Abstract: A novel optical control system using nematic liquid crystals and acoustooptic devices is introduced that can provide compact, lightweight, low cost, transmit/receive mode, high performance (greater than 8 bits), truly analog, amplitude and phase control for large phased array antennas. The system provides independent amplitude and phase calibration and control capabilities across the array.

Wide null and low sidelobe pattern synthesis for phased array antennas

Abstract: The general expression for phased array antennas with wide null and low sidelobe pattern are described. The pattern synthesis algorithm/sub /is based on the adaptive array theory and Gram-Schmidt orthogonalization and can be applied to antennas on arbitrary convex surface arrays. Finally, some numerical results for linear array, circular array and elliptical array are given. >

Conformal on-glass vehicle antennas at VHF

Abstract: Previous work by the authors (see IEE Internat. Conf. on Antennas and Propag., vol.2, p.950, 1991) described the requirements for modelling a passenger vehicle and its rear-window heater when used as an unconventional receiving antenna for VHF broadcast reception. The complexity of the current distribution which results, both on the heater element as well as on the vehicle bodywork was discussed and the effects of this on the radiation patterns of various antennas were computed using the NEC 2 Moment Method code. Whereas it was realised that the glass substrate on which the antenna is mounted would alter its characteristics this effect was not quantified in that earlier study. Here they present the results of further research which, amongst other things, considers the effects of the glass on the performance of these antennas and includes comparative results from both the computer simulations and from an extensive measurement programme. >

A phased array error correction scheme

Abstract: A new method intended for use with digital beamforming array control is presented. It consists of replacing the signals from failed array elements using reconstructed signals from other elements in the array. The method can be applied in the presence of a multiplicity of external noise or jamming signals to provide low sidelobe control for each signal. It involves only linear processing that must be performed at a rate compatible with the information bandwidth. The procedure can improve sidelobe against interfering signals at the expense of reduced signal-to-noise ratio compared to an error-free array. >

Study of stacked microstrip phased arrays

Abstract: A study of phased arrays of rectangular stacked microstrip patch antennas is presented. Two theoretical methods are discussed, i. e., a finite array theory and an infinite array theory. Both theories give almost the same results for a 7 × 7 array, except for edge array elements and for large scan angles. Measured coupling coefficients of a 7 × 7 array are compared with calculations and agree fairly well. © 1993 John Wiley & Sons, Inc.

A novel high efficiency, dual polarised, flat plate array

Abstract: With the increasing use of array antennas in many applications, the design of low profile, high performance, lightweight arrays is of considerable interest. The authors describe a flat plate array development which has been carried out at ERA Technology under ESA funding, the aim of which has been to provide an ultimately space qualifiable, dual linearly polarised antenna operating at Ku-band. The key performance requirements were cross-polarisation levels similar to conventional horn antennas, and high efficiency.

Phased array antennas

Abstract: This chapter is a comprehensive treatment of phased arrays, including (1) array theory, analysis and synthesis techniques; (2) the detailed treatment of array elements and mutual coupling effects; and (3) active arrays - architectures, transmitter-receiver (T/R) modules, feed and control, design criteria and low-sidelobe techniques.

A simple cosec/sup 2/-microstrip array: the shovel-microstrip array

Abstract: A novel application of a microstrip array is presented. Although microstrip arrays are often made on mechanically flexible substrates for conformal applications, this approach uses such flexibility to achieve cosecant-squared beam shaping. The antenna developed is the shovel-microstrip array antenna. >

Comparison of reconfigurable methods of active phased array antenna

Abstract: The biquadratic programming method is shown to be advantageous in reconfiguring an active phased array antenna by changing the phase of each remaining active element. Numerical results for a 13-element linear array are discussed to highlight this algorithm. The reconfigured results are compared against the eigenvalue and cophasal methods. It is concluded that, from both the theoretical and the practical viewpoint, the phase-only beam shaping technique provides the most suitable method for the optimum reconfigured phased array. >

Device for operating a wideband phased array antenna

Abstract: The invention relates to a circuit arrangement for operating a wideband phased array antenna. In this case, the associated individual antennas are driven by mixer arrangements which enable highly accurate, reliable and cost-effective phase changing.

Optimized planar array antenna nulling with phase only control

Abstract: A new theoretical method is derived by which a planar array antenna can provide maximum antenna gain in a specified pointing or look direction while simultaneously imposing J nulls in J directions. This is all accomplished by only varying the phase setting at each element of the array. Thus any amplitude taper can be applied to the array. In the transmit mode unity amplitude weighting is desired so that all elements transmit the same power, In the receive mode a taper is desired for the generation of lower sidelobes. The required nulls in the transmit and receive antenna patterns can be provided with this method. Typical examples are presented for this method and the degradation with system errors (i.e. phase errors in each channel) is evaluated. Antenna pattern plots are presented for a planar array composed of several thousand elements spaced on a triangular grid.

Fast synthesis of shaped reflector antennas for contoured beams

Abstract: The author describes and exemplifies a technique for aperture synthesis and shaped reflector design which has most of the accuracy and flexibility of the analysis-in-an-optimisation-loop design method, while being many times faster. The algorithm is a version of the Method of Successive Projections. The author emphasises practical applications for satellite antennas; discussion focusses on single offset reflectors and on the application of the algorithm to multiple simultaneous requirements, such as multiple beams or multiple frequencies. An example is shown of the synthesis of a C-band transmit/receive antenna exhibiting true dual-band performance with a coverage specification including isolation as well as in-coverage gain requirements.

Automatic diagnostic and localization of defective elements in phased array antennas

Abstract: A novel method for the diagnosis and localization of defective elements of feed network branches in large phased array antennas has been proposed and experimentally validated. A passive microwave comparer circuit is introduced which can be permanently integrated, in large numbers, in the phased array and will then be able to perform the functions of fault diagnostic and defective element localization. To validate the feasibility of the proposed technique, the complex ratio of two independent signals exciting two loads with the aid of a comparer circuit was measured. >

Azimuthal distribution of noise and interface at HF

Abstract: The predictions of atmospheric and man-made noise in CCIR Reports 322 and 258 are for short lossless, grounded, single vertical monopole antennas, but practical antennas may differ from the CCIR reference antenna in many respects. The antenna directivity may be expected to affect both noise and spectral occupancy statistics. Experimental information on the effects of directivity on noise is scarce, and in some respects conflicting. Most previous spectrum occupancy studies have used omnidirectional antennas, but some results with directional antennas have recently been reported. The paper reports further measurements at a site in Southern England.

New guided-wave optical beam former for phased array antennas

Abstract: In this paper we present the theoretical investigation and design of a guided-wave optical processor suitable for beam forming of a linear phased array antenna and based on a planar structure involving two acousto-optic transducers (AOT) having contra-directional surface acoustic wave (SAW) propagation. By applying two different periodic microwave signals to the transducers, the phase content of the output field distribution in the transverse direction with respect to the propagation one is a linear function of the applied frequency difference and can be used to drive a photodiode array connected to the phased array antenna by a RF circuit. The performance of the circuit has been also defined with respect to the resulting beam forming and to the radiation pattern characteristics of the driven microwave array. In this study, acousto-optic interaction on a lithium niobate planar-waveguide has been considered.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.