Showing papers on "Antenna array published in 1985"

The MU radar with an active phased array system: 1. Antenna and power amplifiers

Abstract: The MU (middle and upper atmosphere) radar of Japan is a 46.5-MHz pulse-modulated monostatic Doppler radar with an active phased array system. The nominal beam width is 3.6° and the peak radiation power is 1 MW with maximum average power of 50 kW. The system is composed of 475 crossed three-subelement yagi antennas and an equivalent number of solid state power amplifiers (transmitter-receiver modules). Each yagi antenna is driven by a transmitter-receiver module with peak output power of 2.4 kW. This system configuration enables very fast and almost continuous beam steering that has not been realized by other mesosphere-stratosphere-troposphere radars. Also, a variety of sophisticated operations are made feasible by dividing the antenna array into several independent subarrays. A brief description of the system, particularly its antenna and power amplifiers, is presented herein.

Optimising the synthesis of shaped beam antenna patterns

Abstract: A technique is introduced which uses the conventional polynomial representation of the antenna pattern produced by an equispaced linear array. Certain roots are displaced from the unit circle radially, to fill a portion of the pattern, which before this displayed lobes interspersed by deep nulls. The angular and radial positions of all the roots are simultaneously adjusted so that the amplitude of each ripple in the shaped region and the height of each sidelobe in the nonshaped region are individually controlled. Applications to a cosec 2 θ × cos θ pattern and to a flat-topped beam are presented. Experimental validation is also offered.

Broadband circularly polarised planar array composed of a pair of dielectric resonator antennas

Abstract: A new type of planar array composed of a pair of dielectric resonator antennas has been devised and tested. Both the radiation patterns and ellipticity properties are presented. The 2 dB ellipticity bandwidth obtained was approximately 15% at X-band.

The effect of phase-shifter errors on the performance of an antenna-array beamformer

Abstract: The paper considers the random phase errors in the phase shifters which are used in an antenna array to steer the beam in the look direction, and analyzes the effect of these errors on the performance of the optimal processor which maximizes the output SNR by deriving the expressions for the output signal power, residual interference power, output SNR, and the array gain as a function of the variance of these errors. The paper also considers the phase quantization error which arises in the digital phase shifters and shows how the performance of the optimal processor depends on the number of bits of the digital phase shifters.

Analysis of constrained LMS algorithm with application to adaptive beamforming using perturbation sequences

Abstract: Adaptive antenna array processing employing a constrained least mean square (LMS) algorithm requires an unbiased estimate of the gradient of the output power with respect to the array weights. There are a number of schemes for obtaining an unbiased estimate of this gradient. Though in each case the estimated gradient is unbiased, the covariance of the estimated gradient with each method is different and thus the transient and the steady state behavior of the constrained algorithm is different in each case. The transient and the steady state behavior of the weight covariancc matrix is analyzed, exact expressions for the misadjustment are derived, and a comparison of the performance of the algorithm is presented when the required gradient is estimated by different schemes. The schemes considered include gradient estimation when all the array signals are accessible as well as gradient estimation using perturbation sequences for eases when the array signals are inaccessible. The necessary and the sufficient condition for the diagonlization of the weight covarience matrix is also derived.

Correction of error in reduced sidelobe synthesis due to mutual coupling

Abstract: Standard Chebyshev and Taylor reduced sidelobe synthesis techniques ignore mutual coupling, and so can lead to pattern errors where the resulting array pattern departs significantly from the desired pattern. Two methods for correcting this error are described and examples of their application to eight-element dipole arrays are presented. One approach uses characteristic modes, while the other method employs a simpler array mode and point matching. The techniques can also be applied to synthesis of nonuniform arrays.

Design of error tolerance of a phased array

Abstract: In the letter we present a set of universal probability curves that relate the array error tolerance, illumination function, achievable sidelobe level and the designed sidelobe level. We show that this set of probability curves can be used to find a lower designed sidelobe level to achieve a better error tolerance. The relations of array directivity gain and beamwidth with respect to illumination function are also discussed. These parameters can be conveniently used for this design procedure without detailed knowledge of the array illumination.

On an adaptive antenna array under directional constraint

Abstract: It is shown that for narrowband applications, the number of linear constraints needed for an adaptive array to achieve a fixed look direction response can be reduced from two to one. The result is useful since it can be exploited to reduce the computational complexity required to determine the optimal weight vector.

A new approach to the design of broad-band element space antenna array processors

Abstract: In this paper, a new approach to the design of broad-band time-domain element space antenna array processors is presented. The basic approach is based on the idea of minimizing the mean-square deviation between the desired look-direction response and the response of the processor over a frequency band of interest. With this approach, three types of presteering can be handled: no presteering, coarse presteering, and exact presteering. The elimination of presteering lime delays is important in a digital implementation of antenna array processors. The relationship that the new processor has to other broad-band processors is explored and the significance of the parameters associated with the new processor is established. Furthermore, the approach presented enables various types of errors and mismatches between signal model and actual scenario to be incorporated in the problem formulation.

Millimeter wave monolithic schottky diode imaging arrays

Abstract: Planar Schottky diodes are integrated with bow-tie antennas to form a one-dimensional array. The energy is focused onto the antennas through a silicon lens placed on the back of the gallium-arsenide substrate. A polystyrene cap on the silicon lens reduces the reflection loss. A self-aligning process with proton isolation has been developed to make the planar Schottky diodes with a 1.1-THz zero-bias cutoff frequency. The antenna coupling efficiency and imaging properties of the system are studied by video detection measurements at 94 GHz. As a heterodyne receiver, a double-sideband mixer conversion loss of 11.2 dB and noise temperature of 3770°K have been achieved at a local oscillator frequency of 91 GHz. Of this loss, 6.2 dB is attributed to the optical system and the antenna.

A Numerical Method for Near-Field Array Synthesis

Abstract: A numerical method for near-field array synthesis is developed for arbitrary array geometries. The intended application is for generating a planar field in a test volume for electromagnetic susceptibility testing, but the method is valid for arbitrary field distributions. A uniqueness theorem is utilized to allow the field conditions to be enforced on the surface of the test volume rather than throughout the volume. The synthesis method is a least-squares solution with a constraint on the source norm; the constraint keeps the field small outside the test volume. Numerical results are shown for the case of synthesizing a plane wave in the near field of an array of line sources.

Theoretical and experimental study of monopole phased array antennas

Abstract: A theoretical and experimental investigation of the mutual coupling in large two-dimensional periodic planar phased arrays of thin cylindrical monopoles is addressed. A plane wave representation of the active input impedance is used to analyze an infinite array of monopoles. A finite array analysis is used to compute the center element gain pattern and input impedance as a function of the array size and element position. The center element gain pattern is shown to have omnidirectional vertical polarization with a null on-axis and peak gain in the vicinity of 50\deg from broadside. Measurements of the element gain pattern and mutual coupling for a 121-element passively terminated monopole square lattice array are shown to be in good agreement with the theory. The results of the infinite array analysis are compared to theoretical and experimental data in the literature for hexagonal lattice arrays.

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

Abstract: 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.

Adaptive methods in underwater acoustics

Abstract: 1. Acoustical Background of Signal Processing.- Twenty years of signal processing.- Ambient noise: characteristics of the noise field.- An analytical method to predict the statistical characteristics of ambient shipping noise.- Statistical aspects of sound propagation in the ocean.- Towed array response to ship noise: a near-field propagation problem.- Three-dimensional FFP model of acoustic- and elastic wave propagation in horizontally layered media.- Seismic sensors in underwater acoustics: results from sea-floor measurements in areas of different geology.- Underwater acoustics in the Arctic Ocean.- A new theory for the transmission and reflection coefficient of layered systems.- Second moments of the pressure field near a smooth caustic.- Stochastic systems theory of the scattering of waves from a random medium.- Hydrodynamic flow noise in hydrophones.- Wavevector structure of turbulent wall pressure and its filtering by normal transmission and spatial averaging in sensor arrays.- Target strength and echo structure.- 2. Theoretical and Practical Aspects of Signal Processing.- Time delay estimation.- Time delay estimation in the presence of multipath propagation.- Constrained time delay estimation via zero-crossing methods.- Range and bearing determination: Maximum Likelihood and Kalman-Bucy techniques.- Delay estimation with nonstationary signals and correlated observation noises.- Source parameter estimation by approximate Maximum Likelihood.- On the use of focused horizontal arrays as mode separation and source location devices in ocean acoustics.- High-resolution source-depth estimation in ice covered shallow water.- Spectrum analysis: overview of classical and high resolution spectral estimation.- Application of high resolution spatial processing methods to real data of a fixed array in shallow water.- Experimentation of spatial processing methods.- Simultaneous estimation of spectral lines and of a superimposed continuous spectral density.- Fitting sinusoids to sampled data and correlation sequences.- An extended maximum entropy method for high resolution spatial processing.- Spectral and interspectral analysis of low frequency submarine acoustic signals received on an array of sensors.- Overview of adaptive array processing.- New approaches in the adaptive array processing field.- Multiple detection using eigenvalues when the noise spatial coherence is partially unknown.- Theoretical and experimental comparisons of optimum element, beam and eigen space array processors.- Applications of some statistical measures to spatial signal processing.- The cross correlation matrix in spatial processing.- The effect of bandwidth on the performance of a postbeamformer interference canceller.- A new approach to the design of broadband element space antenna array processors.- On the role of prior information in nonlinear bearing estimation.- Beamforming by the cross-correlation analysis of received spectra.- Applications of adaptive array processing.- Adaptive active sonar reception in shallow water using vertical array outputs covariance matrix eigenvalues: experimental results.- Beamforming with a distorted towed array.- Influence of hydrophone position errors on spatial signal processing algorithms.- A tutorial introduction to nonlinear filtering.- Detection with uncertainty: Nonparametric, robust or adaptive approaches.- The design of optimal processors for arrays with non-Gaussian noise inputs.- Adaptive processing of underwater acoustic signals in non-Gaussian noise environments: I. Detection in the space-time threshold regimes.- Detection and classification phenomena of biological systems.- Detection and recognition of moving or randomly scaled objects.- Iterative algorithms for deconvolution and reconstruction of multidimensional signals from their projections.- 3. Techniques and Applications.- Digital signal processing for sonar.- Optical signal processing.- Beamforming for sonar signals by means of an incoherent acousto-optical processor: experimental results.- Adaptation of fiber optics to hydrophone applications.- Ceramic elastomer composite hydrophone.- Expert systems for ship noise interpretation.- Comparison of the statistical and the expert system approach for the interpretation of ship noise.- Signal processing techniques to analyse and simulate radiated underwater ship propeller noise.- Signal processing in ocean tomography.- New advances towards ocean, acoustics and space integration.- Passive synthetic aperture sonar - an analysis of the beamforming process.- Techniques for measuring backscattering from the sea floor with an array.- AEON - adaptive time-space array processing.- Summaries of Workshops.

Monitoring techniques for phased-array antennas

Abstract: The problem of monitoring phased-array antennas in general and microwave landing system (MLS) in particular is considered. Various methods of monitoring phased-array antennas are suggested. One is based on changes in the far-field radiation pattern arising from defects in the array. Another method uses the near-field to far-field transformation, based on the concept of the plane-wave spectrum, for the detection of defects in the antenna. A third method is based on near-field measurements and uses the properties of the Fresnel integral. The methods were simulated on the computer and, where possible, were tested by experiment. A comparative assessment of the methods is given, and an operational monitoring system is suggested for the MLS phased army.

A Quasi-Optical Multiplying Slot Array

Abstract: A quasi-optical frequency-multiplying slot array for high-power millimeter-wave applications has been demonstrated Single slot conversion loss measured for X- and Ka -band models produced results that are similar to in-waveguide multipliers using the same type of diodes An eight-element multiplying array exhibited better than --12-dB sidelobe level at 70 GHz The simple planar structure makes millimeter IC fabrication of the slot array feasible

The effect of a finite distance source on an Applebaum array

Abstract: The effect of the finite distance of the signal source on the performance of a far-field steering Applebaum type adaptive array is examined. The output signal-to-noise ratio (SNR) is expressed in terms of 1) the distance between the signal and the array center, 2) the input SNR, 3) the element number and locations, and 4) the signal direction. From that expression a rule of thumb is drawn to determine the distance between the signal source and the array center at which the degradation of the output SNR is 1 dB. That distance is in general much larger than the far-field range of a conventional beam forming array.

Optimization with controlled null placement in antenna array pattern synthesis

Abstract: The optimal solution to the problem of minimizing the complex weight vector norm subject to a "look direction" and null constraints in array pattern synthesis is given. It is also shown that several constrained optimization problems in pattern synthesis, viz, constrained maximization of signal-to-noise ratio (SNR), constrained pattern gain maximization, and constrained least squares pattern synthesis are, in fact, equivalent. Reduction of the maximum gain in the look direction and the occurrence of main-lobe angular shifts which are inherent in constrained pattern synthesis are also investigated.

Phased array antenna

Abstract: An antenna feed network for forming and steering a phased array antenna beam. The feed network includes a plurality of dual parallel microwave transmission paths for each array element. To form and steer the beam at the correct spatial angle each pair of paths is shorted at the appropriate location to provide a time delay for the wave traversing the path. Each signal of the plurality of signals drives a different element of the antenna array with the proper phase to form and steer a beam from the array. The feed network is linear and reciprocal and can therefore be used in a transmit or receive antenna array. A ferrite circulator can be used to generate the time delayed signals on the short circuited transmission line. However, this antenna is not reciprocal and must be adjusted for either a particular receive or transmit beam position.

Multiple beam crossovers for a lens-fed antenna array

Abstract: Multiple beams from a linear antenna array can be formed using Ruze or Rotman lenses. A waveguide fed, parallel plate lens has been described, which provides beams with low sidelobes (⩽-20dB) and beam crossovers a≃ -10 dB. A microstrip version of this lens has also been described, with the additional feature of a beam port overlap network which doubles the number of beams and consequently raises the beam crossovers to ≃ -2dB, at the expense of a 3dB loss in the overlap network. In this paper two new networks are described, with 1.76 dB and 1.25 dB loss respectively, which increase the original number of beams from the lens fed array by 50%, and consequently provide beams with intermediate crossovers. Theoretical analysis predicts the beam crossovers as ≈ -4 or -44½ dB for the two networks.

Statistical analysis of EIRP degradation in antenna arrays

Abstract: Expressions are given for the expected value, variance, and worst-case degradation of the equivalent isotropically radiated power (EIRP) of an antenna array subject to random errors in the excitation coefficients. These expressions apply to passive as well as active arrays fed with several amplifiers. An example is presented that demonstrates the applicability of the analysis to active arrays.

Analysis of a horizontal two-element antenna array above a dielectric halfspace

Abstract: The mixed-potential integral equation is employed to compute the current distribution on two parallel wire antennas placed horizontally above an air/water interface. The Sommerfeld integrals incorporated in the kernel of the integral equation are evaluated by numerical integration along the steepest-descent path in the complex plane. Sample results are presented for several cases of interest and are compared with measured data.

Signal acquisition apparatus and method

Abstract: A novel radio receiver capable of simultaneously and instantaneously determining the frequency and azimuthal and elevational position of many radio signal sources is disclosed. The invention makes use of an antenna array and associated beamforming networks capable of producing an omnidirectional reference signal, and a directional signal in which amplitude depends upon the relative elevational position of the radio frequency source and complex phase depends upon the relative azimuthal position of a radio frequency source. The use of a two-dimensional compressive receiver in one embodiment provides a way for instantaneously and reliably producing the Fourier transform of these signals, allowing accurate and continuous measurement of phase and amplitude difference. The antenna geometries disclosed additionally provide such signals for a wide input bandwidth.

Multi-stage linear array antenna

Abstract: PURPOSE:To increase the beam tilting effect by setting the 1st phase shifter for each exciting element so as to give a beam tilting angle larger than a required value and obtaining a required beam tilting angle by the combined phase shift by the 1st and 2nd phase shifters so as to reduce a side lobe level produced during propagation. CONSTITUTION:An antenna array 10 consists of 16 exciting elements 21-216, the interval (d) of each antenna is selected as one wavelength and phase shifters 31-316 are inserted respectively to the exciting elements 21-216. Further, the antenna array 10 is divided into four groups as four elements each and phase shifters 41-44 are inserted of a combined terminal of each group. The exciting elements 21-216 are set to have an angle alpha larger than the required beam tilting angle. Since the phase shifters are incorporated with the exciting elements in advance, the antenna design is attained easily and the 1st upper side lobe level is reduced by using the 2nd phase shifter to restore the beam tilting angle only.

Maximizing jammer effectiveness for evaluating the performance of adaptive nulling array antennas

Abstract: A theory is developed which is used to find interference source distributions which maximize consumption of the degrees of freedom for N -channel adaptive nulling arrays with arbitrary element positions. For a given number of interference sources, after proper positioning, these sources represent a maximally stressed environment for the adaptive array degrees of freedom. The interference covariance matrix eigenvalues are shown to have a direct bearing on the number of degrees of freedom consumed as well on the adaptive cancellation. Numerical examples are given showing that certain source geometries produce the situation where little or no adaptive cancellation is possible due to the available degrees of freedom being severely taxed.

Dipole array with phase and amplitude control

Abstract: A bistatic VHF Doppler radar is utilized to detect and track one or more intruders crossing a large annular ring surveilance zone surrounding a central high security installation A central omni-directional transmitter radiates the surveillance zone with a continuous wave (CW) signal Predetermined ones of a plurality of receiver antennas circumferentially spaced around the surveillance zone receive a portion of the signal which is reflected by an intruder crossing the surveillance zone and a portion of the signal which is directly radiated from the transmitter antenna The reflected signal portion may be received by antenna arrays each of which is controlled to form a null in its pattern toward the transmitter antenna to overcome direct signal overload The direct signal portion may be received by stub antennas Each antenna array and each stub antenna is connected to a separate channel of a dual channel receiver An intruder moving across the surveillance zone causes signals representative of Doppler cycles of phase change to be generated The outputs of the two separate channels are compared and their relative phase changes measured A detected intruder causes an alarm signal at a central processing station and the Doppler information is processed to generate tracking data which is shown on a display device An automatic null control circuit may also be utilized to accommodate multipath conditions and static clutter due to environmental factors

Monopulse printed circuit dipole array

Abstract: The design and performance of a monopulse Ku-band planar array is described. The antenna is designed to provide 20 dB sidelobes sum pattern in the azimuth plane and an operating bandwidth of 1 GHz (16.25-17.25 GHz). The voltage standing-wave ratio (VSWR) of this array at the input is less than 2:1 over the bandwidth.

Millimeter-Wave Integrated-Circuit Antenna Arrays

Abstract: This thesis presents three different types of millimeter-wave integrated-circuit antenna array. They are a linearly polarized antenna array that can form polarization and intensity line images, a circularly polarized spiral antenna and a two-dimensional tracking antenna array. They are all integrated-circuit antennas with detectors on quartz substrates using quasi-optical systems to collect and focus the waves.

Antenna array and radar with a low jamming sensitivity

Abstract: Electronically scanned antenna array comprising memories (4, 33, 34) permitting storage of the values for digital control of the phase shifters which permit the aiming of the microwave energy beam. Furthermore, the device makes it possible to reduce the sensitivity of the antenna in the direction of jamming devices. The values contained in the memories (4, 33, 34) can be modified, either by changing the (PROM) memories themselves, or by reprogramming the (EPROM, EEPROM) memories. Thus, variations in behaviour of the phase shifters over time, or their replacement, can be taken into account.

Adaptive microstrip array using parasitic elements

Abstract: A plurality of strip-line elements are used as an antenna array. The direvity of the array is controlled by controlling the terminating reactance of the closely-coupled stripline elements.