Showing papers on "Reflective array antenna published in 1996"

Integrated active antennas and spatial power combining

Abstract: Oscillators and Synchronization. Antennas and Arrays. Power Combining. Integrated and Active Antenna Testing. Active Antennas: Early Work Before 1987. Active Microstrip Patch Antennas and Power Combining. Integrated and Active Grids. Endfire Notches and Other Slotline Active Antennas. Integrated and Active Inverted Stripline Antennas and Other Active Antenna Configurations. Integrated Antennas with Passive Solid-State Devices. Beam Steering for Active Antenna Arrays and Spatial Power Combiners. Index.

Multiband phased-array antenna with interleaved tapered-elements and waveguide radiators

Abstract: Multiband, multibeam, phased array antennas are required for today's multi-function radar and communication applications. These types of antennas play a major role in the shipboard and airborne environment, where space is limited. A single antenna is now asked to perform multiple functions, including long-range surveillance, navigation, weapons control, tracking and recognition, and electronic warfare support measures. A phased array antenna capable of covering several different frequency bands in a common aperture is highly desirable, and is currently being pursued for many of these applications. A number of multiband radar antenna configurations have been proposed in the past. An ultra-wideband phased array antenna design using interleaved waveguide elements and wideband tapered elements is presented. This phased array antenna can operate over at least three frequency bands. Numerical results of the aperture match for both types of radiators, including mutual interaction, are presented.

Optical processor for multibeam microwave array antennas

Abstract: A new optical processor for multibeam microwave transmitting array antennas is proposed by using a spatial optical processing approach. The system is based on the generation of overlapping multiple beams. A two beam experimental optical processor for producing RF signals with different phase distributions and with feeds to array antennas is demonstrated.

Performance predictions for cellular switched-beam intelligent antenna systems

Abstract: This article presents simple formulas which are helpful in predicting interference reduction and capacity increase provided by switched-beam intelligent antenna systems for cellular telecommunications. The key element of this type of intelligent antenna system is an m/spl times/M switching matrix where m is the number of beams and M is the number of radio channel units. The system capacity is related to the complexity of the switching matrix. A 12-beam switched-beam antenna system can provide 100 percent capacity increase over a conventional three-sector (three-beam) antenna system.

Characteristics of switchable ferrite microstrip antennas

Abstract: Switchable antennas consisting of microstrip elements with an in-plane biased ferrite cover layer are introduced. Their radiation and radar cross section (RCS) properties are examined through a full-wave moment-method analysis. For microstrip antennas with a ferrite cover layer, the presence of a decaying extraordinary wave in the ferrite layer can reduce or prohibit incident fields from reaching the antenna resulting in significant RCS reduction. For antenna radiation, most of the power will be converted into magnetostatic waves and little radiates into the air. Under such circumstances, the antennas are "off," in the sense that they are effectively absent as radiators or scatterers. The aim of this paper is, through the use of an accurate full-wave analysis, to investigate the properties of the switchable microstrip antennas. Both the cases of strip dipoles and rectangular patches are analyzed. The effects of the cover-layer thickness, bias-field strength, and the existence of both ordinary and extraordinary waves on the switchable antenna properties are discussed.

Matrix method for near-field diagnostic techniques of phased arrays

Abstract: Near-field measurements can be used as diagnostic tools to reconstruct the aperture field distribution of planar array antennas and to locate their possible defective elements. A method for obtaining the individual element excitation of an array antenna from measured near-fields is presented. A computer simulation is performed to evaluate the effect of various near-field parameters such as the measurement distance and the sample spacing on the reconstruction of the excitation. The validity of the approach has been verified using both synthetic and actual measurements data. Good results have been obtained.

Two low-cost phased arrays

Abstract: One of the most versatile antennas used in radar is the phased array. In a phased array antenna, the phase shifters (or T/R modules in an active aperture phased array) with their beam-steering control circuitry along with the feed network account for the major hardware cost. This paper presents two antenna array configurations that use simpler feed, simpler phase-shifting and beam-steering control circuitry for realizing low-cost phased arrays. Both are lens configurations. The first one uses a Radant lens, which provides a medium that is loaded with diodes and provides the needed phase shift by switching the diodes on and off. The other configuration employs a ferroelectric dielectric material whose dielectric constant can be varied with an applied DC bias voltage. It is shown that the ferroelectric lens may have further advantages of smaller thickness, simpler beam-steering controls and lower cost.

The stabilisation of phased array antennas

Abstract: A method of stabilizing the action of a phased array antenna system in which the amplitudes and phases of signals applied to, or produced by, elements of the antenna are monitored, differences are detected and suitable weighting factors are determined and applied to remove the differences between the amplitudes and phases of the said signals. Transmitting and receiving antenna systems are described.

T/R module architecture tradeoffs for phased array antennas

Abstract: Active phased array radars typically require solid state T/R modules with high output power, low noise figure, high third order intercept (TOI), and sufficient gain in both transmit and receive. Since the T/R module cost is 40-60% of the antenna cost, it is imperative to use an architecture that meets all requirements with a minimum number of MMIC chips. In this paper we examine several T/R module architectures, analyze their performance, provide a tradeoff between different performance parameters, and recommend an architecture for a given set of requirements.

CPW-fed oscillating microstrip antennas

Abstract: Operating with a low-cost FET, oscillating CPW-fed microstrip antennas working at /spl sim/4 GHz have been presented. Because the design is based on slot or slot loop apertures, no via holes are required, These oscillating antennas are compact, easy to fabricate while providing uniform radiation patterns with cross-polarisation levels below -17 dB. Active integrated power combining arrays or active integrated phased arrays are possible future applications of these radiating elements.

Scattering from a cylindrically conformal slotted-waveguide array antenna

Abstract: Slotted-waveguide array antennas are widely used on modern airborne radar. However, conventional planar slotted-waveguide antennas have a significant contribution to the overall radar cross section (RCS) of the host vehicle. Reduction of the antenna's RCS is one of important aspects for the stealth technology. It is well known, the RCS of a flat plate is generally higher than that of a smooth curved surface. Therefore, it is possible to reduce the RCS by replacing a planar slot array with a curved slot array. Because of a large number of slots and the mutual coupling between slots and between slots and the waveguide, the analysis of the scattering from a slotted waveguide array is very difficult. As a result, only planar slot antennas have been considered in the past. Fan (see Ph.D. thesis, Tsinghua University, Beijing, China, 1995) presented the theory of analysis and design of cylindrically-conformal slotted-waveguide array antenna with a curved waveguide as the main guide and sectoral guides as the branch guides. We analyse its scattering properties, and to simplify the analysis, we neglect the coupling between the main guide and the branch guides.

UHF/VHF multifunction ocean antenna system

Abstract: A multifunction antenna system is selectively operative over the UHF and VHF frequency ranges using a novel arrangement of symmetrically disposed phased radiating elements that function as a dipole turnstile type array at UHF and as a monopole at VHF. At VHF the UHF radiating elements and feedlines are fed in parallel against ground to produce a pattern similar to that of a short vertical monopole. VHF and UHF coupling networks offer low VSWR and minimize circuit losses when utilized with a folded dipole array. The compact, lightweight structure is adaptable to oceanic communications by installing in a towed radome adapted for water flotation, and provides low angle hemispherical UHF radiation without pattern switching, with the water surface providing a reflective ground plane.

Helical antennas for multi-mode mobile phones

Abstract: The use of helical antennas in handsets for multi-frequency operation has been studied. It is shown that it is possible to obtain very wideband operation or two separate frequency bands of operation by using two helical antennas attached on the top edges of the conducting case of a handset. The presence of the second antenna has relatively small effect on the operation. If one of the single helical antennas is replaced with two helical antennas one within the other three separate frequency bands of operation can be obtained.

A microstrip array antenna with omnidirectional pattern fed by CPW

Abstract: Colinear array antennas constructed from coaxial elements such as sleeve dipoles or patch antennas using parasitic cylinders are employed as omnidirectional antennas in mobile communication. In microcellular and wireless LAN systems, simple, small-size, and low-cost antennas for base stations are desired. The paper proposes a base station antenna that satisfies these requirements. The proposed antenna configuration is a back-to-back narrow-width rectangular patch fed by a CPW. The experimental results for an element antenna and an array antenna are described. Good omnidirectional radiation pattern characteristics have been obtained.

Antenna array configuration

Abstract: A base station arrangement for a cellular radio system comprising an antenna array, is disclosed. The downlink signals transmitted from antennas have a spacing which is scaled in proportion to the transmitted and received wavelengths. A method of operation is also disclosed.

A two-dimensional retrodirective array using slot ring FET mixers

Abstract: A printed 4-by-4 retrodirective antenna array has been developed, which employs the heterodyne phasing technique at 6 GHz. Each array element comprises a balanced FET resistive mixer, integrated in a ring slot which serves as both an antenna and hybrid. Driven by a reference signal at twice the incident frequency, the mixers receive and reradiate incident signals while imparting a conjugate phase shift onto them. The result is retrodirective radiation that is not critically dependent on either the array geometry or the planarity of the wavefront. This makes conformal retrodirective arrays possible. The backscatter pattern of the array exhibits a wide-angle response (>100 degree scan range) in both planes.

Integrated antenna system for satellite terrestrial television reception

Abstract: An integrated antenna system for satellite and VHF/UHF reception is provided. The elements of a VHF/UHF antenna are embedded in a satellite antenna. The satellite and VHF/UHF signals are combined and transmitted on a single cable to the receiver. The receiver splits the signals. A switch within the receiver unit for displaying either the VHF/UHF or satellite transmissions is provided. The receiver also powers amplifiers at the antenna using the single cable.

Shaped beam synthesis and conditional thinning for planar phased array

Abstract: A design procedure for a planar phased array pattern is presented. The array is designed to produce a cosecant squared beam along the elevation plane and a pencil beam along the azimuth plane. This design procedure relies on two orthogonal linear array distributions. The linear array distributions are obtained via the use of the Taylor distribution. For the azimuth pattern, a pencil beam distribution is obtained by sampling a 30 dB Taylor distribution. On the other hand, for the elevation pattern, a low side lobe Taylor distribution is used in conjunction with a Woodward type synthesis method to fill the nulls and shape the main beam to the desired beam characteristics. The resulting continuous complex aperture distribution is sampled to obtain the linear elevation discrete array distribution. This technique produces a single continuous complex aperture distribution. The separable rectangular array distribution is formed by the product of two orthogonal linear array distributions. Since the resulting amplitude distribution of the planar array is the product of two sampled linear edge tapered symmetric distributions, corner elements are highly underutilized. Hence, the corners could be lopped off and peripheral elements at the edges be eliminated through a conditional array thinning process. This resulted in an array with a circular boundary, allowing the array to fit conveniently into a circular configuration. The thinned array is physically smaller and reduces the overall cost, size and weight of the antenna. Such an array pattern still maintains its shaped main beam characteristics and well behaved side lobe levels.

Compensation of mutual coupling effects in array antennas

Abstract: The possibilities of compensating for the mutual coupling in array antennas are discussed. An alternative method of viewing the matrix multiplication technique used to compensate for these effects is presented. The signals applied to the antenna ports are modified in order to neutralize the mutual coupling effects.

Phased array antenna systems for commercial applications in Japan

Abstract: This paper will review research-level phased array activities and developed phased array systems in Japan. Two basic technologies for the beamforming networks are discussed, one is microwave processing technology using MMICs and the other is optical processing. Optically controlled phased array antennas utilizing optical components are described. As the commercial available systems, the airborne phased array antenna for INMARSAT-M, and the beam-switching train antenna on the Shinkansen are described. Several systems which have been investigated and not used for the commercial systems are also discussed. These are the S-band beamforming network for inter-satellite links (ISL), the secondary surveillance radar antenna, the multibeam forming network for future mobile satellite systems, and the mechanically steered planar antenna installed on the Shinkasen for DBS.

Integrated active antennas with simultaneous transmit-receive operation

Abstract: This paper discusses two novel active integrated antennas with same frequency transmit-receive operation. Firstly, results are presented for a two element active transmit-receive array using dual linear polarisation and sequential rotation. Each element includes an integrated oscillator and amplifier mounted on orthogonal edges of a square patch, such that transmit and receive paths are isolated and polarisation duplexed. The array gives in excess of 45dB transmit-receive isolation with an output power of 5.4dBm and a receive gain of 8.2dBi at 4.05GHz. Link budget calculations are used to show expected system performances. Secondly, an active circulator is integrated with a patch antenna to produce a same polarisation fully duplexed transceiver. The active circulator antenna is shown to have 14dBi transmit gain and 7.4dBi receive gain with a transmit-receive isolation of 26.9dB at 3.74GHz. These active antennas have potential uses in both short range communication and radar systems.

Active phased array architectures for high reliability

Abstract: This paper presents the design of active phased array antenna architectures for high reliability that does not require replacement of active components for an extended period of time. The reliability of the antenna is defined in terms of the mean-time-between-failure (MTBF), and design of phased array architectures is discussed for maximizing the antenna MTBF.

Short leaky-wave antennas of sum and difference patterns

Abstract: A set of differential feed short (~0.7 λ0) leaky-wave antennas with sum (Σ) and difference (Δ) patterns is presented. Rigorous field-theory analyses show that the radiation characteristics of these antennas agree well with the measurements. The performance of these antennas is well suited for direction finding applications.

Phased array antenna for tracking and communication with LEO satellites

Abstract: A ground receiving phased array antenna system is described for tracking and communication with satellites in low Earth orbit (LEO). Different active array antenna architectures and the minimum number of array elements for meeting the system G/T requirement are evaluated and compared. A general noise temperature model is also developed for evaluating any phased array antenna system. Moreover, this model is also useful for the design and planning of other receiving antenna systems on automobiles, ships, aircraft, satellites,..., etc.

An array of Franklin and Bruce antennas

Abstract: Franklin and Bruce antennas are composed of repeated radiation cells. These antennas belong to the category of travelling wave antennas. The radiation from these antennas is linearly polarized. This paper presents an array of Franklin and Bruce antennas, which realizes dual polarization. The radiation characteristics of this array are evaluated on the basis of current distributions, which are numerically obtained using the method of moments. The mutual effects between the Franklin and Bruce antennas are presented and discussed. The numerical results show that the array can form radiation beams of x- and y-directed polarizations.

A simple method for null steering in a circular array by perturbations of the radial locations of the elements

Abstract: A reliable communication link between two destinations in a microwave environment requires a propagation path clear of interference signals. An effective method of interference suppression is to form nulls in the antenna pattern in the directions of the interference. Steyskal (1983) proposed null steering in the antenna pattern by using the small phase perturbation. This paper extends the spatial phase perturbation methods used for null steering in a linear array to include a circular array. In this technique the array utilizes the phases obtained from perturbing the radial locations of a circular array to suppress the interference signals. This technique is applied to a Chebyshev-like circular array with 36 elements.

Nonplanar microstrip arrays

Abstract: Pattern synthesis using planar arrays was done extensively in the past, mainly in the context of radar antennas where a cosec/sup 2/ beam is required in the elevation plane. The synthesis leads to a set of coefficients for the array elements which may be difficult to realize and which, if realizable, may lead to a very narrow-band performance. In this paper, a new type of array is proposed. The shaped-beam nonplanar array is an array of microstrip elements, where the phasing is not generated through the feeding network, but by shaping the substrate. Microstrip arrays lend themselves well to a configuration similar to the one proposed, and as it is shown, the final thickness of the array does not exceed a few substrate thicknesses.

Low-profile, broadband, wide-scan, circular-polarized phased array radiator

Abstract: A wideband low-profile, circular-polarized CNBLCP) phased array radiator has been developed for broadband phased array applications. The radiator is capable of providing common-phase-center circular- or dual-linear polarization, and wide scan volume over an octave bandwidth. These are all desirable features in today's phased array antennas for multifunction radar and satcom applications. The design of a new WBLCP element is presented along with its predicted frequency and scan performance. These calculated results have been validated using waveguide simulator measurements. A comparison of the predicted and measured results is also presented.

Wide band flat antenna for mobile microwave terminals

Abstract: The article relates to lens antenna of reduced thickness and formed of a inhomogeneous dielectric It can be readily incorporated into microwave broadcast and communication systems, including portable satellite telephone and broadcast stations, and very attractive as a wide bandwidth antenna at 10-80 GHz This lens antenna can be used in microwave quasi-optical active arrays when active elements are located on a flat dielectric surface with high thermal conductivity Lens antennas could be utilized as receiving and transmitting antennas in many applications, but being formed of a homogeneous dielectric they have many practical disadvantages including high weight, complex surface form and thickness that have limited their implementation The problem of complex surface form can be addressed by forming the antenna lens from a flat piece of inhomogeneous dielectric material While such lenses have certain unique features that cannot be achieved with lenses formed of a uniform dielectric, they do not solve the problem of weight and thickness associated with lens antennas Lens antennas have some common and attractive advantages over reflector antennas Lens antenna production needs less precision Besides the phase mistakes are maximum in the center of reflector antennas and near the border of lens antennas Consequently, their influence is much smaller for lens antennas Lens antennas are extremely broadband and scan a beam inside a wider angle sector than is usual for reflector antennas

Dielectric resonator antennas as an alternative technology for PCS applications

Abstract: This paper examines the use of dielectric resonator antennas (DRAs) as alternative radiators in personal communication system (PCS), covering frequencies from the L-band to the Ka-band (1 to 40 GHz), applications. The advantages and benefits of DRAs over conventional antennas are discussed and several examples are described.