AMTA Paper Archive


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AMTA Paper Archive

Ultra-wideband transient antenna measurement techniques
W.R. Fayne,C. Courtney, D. Slemp, November 1995

In the past few years there have been new application of transient, ultra-wide band microwaves include cooperating aircraft identification and ground penetration Radar's, high power microwave weapons and others. These applications typically require the use of ultra-wideband antennas with characteristics suitable to radiate transient pulses. This paper describes the capabilities of the USAF Phillips Laboratory's new Transient Antenna Range. The antenna range can measure the radiated characteristics of sources/antennas wave forms with risetimes in the 75 ps regime, and with greater than 50 ns pulse width. The antenna range incorporates a hardware suite controlled by a powerful software data acquisition system that runs on a PC. Automatic data reduction can yield values of wave form peak electric field, risetime and waveform spectrum at a single point, or across an azimuthal scan. This paper will also describe a unique wave form splicing technique used in the data processing algorithms of the Transient Antenna Range. This splicing technique allows test personnel to record the (typically) very fast early time history of the radiated waveform with an SCD-5000 scan converter (operating at a maximum bandwidth, 5 ns of record available), and the long time history of the waveform with a DSA-602 transient digitizer.

Deconvolution method for correcting antenna measurement errors in compact antenna test ranges, A
P.L. Garcia-Muller,J-L. Cano, R. Torres, November 1995

High performance antennas require very accurate measurements which are difficult to meet in the conventional compact antenna test ranges. This measurement errors are produced by the non perfect plane wave synthesized by the compact range system. By the application of the reaction between the antenna under test true pattern and the compact range incident field, a closed form relation is found for the measured radiation pattern. Under certain conditions, this measured pattern can be approximated by the convolution of the two diagrams. In this paper it is presented the inverse procedure: the deconvolution to numerically calculate either the true radiation pattern of the antenna under test or the plane wave spectrum of the compact range incident field . The effectiveness and limitations of the method are discussed by numerical simulations and tested by measurements.

Millimeter-wave RCS measurement technology
R. Dezellem,D. Mensa, K. Vaccaro, November 1994

Modifications to commercial millimeter-wave receiver and target positioner systems produced significant improvements in recent W-band experiments at NAWC, Point Mugu. This paper discusses difficulties encountered in millimeter-wave measurements and presents novel methods for their resolution. Results from wideband W-Band experiments, including ISAR images, are presented.

Proposed analysis for RCS measurement uncertainty
R.C. Wittmann,L.A. Muth, M.H. Francis, R. Lewis, November 1994

From a study of several radar cross section (RCS) measurement facilities, we identify significant sources of uncertainty and develop methods for estimating their effect. Out goal is to provide a "reasonable" and uniform formalism for evaluating RCS measurements which can be used on a variety of test ranges to produce comparable estimates of uncertainty.

Study of simple geometric shapes by polarimetric radar
P.S.P. Wei,A.W. Reed, B.Z. Shaw, C.F. Suter, D.C. Bishop, November 1994

New results from complete scattering matric measurements on string-suspended simple geometric shapes - from the Boeing 9-77 compact range - are presented for the first time.

Cross-polarized pattern measurement on point-source compact ranges
D.W. Hess, November 1994

Earlier measurement results are reviewed to understand the result that cross -polarized patterns agree well when compared between a point-source compact range and spherical near-field scanning. By taking account of the symmetry of the aperture distribution, one can see how the cross-polarized pattern can be affected only moderately by the classic polarization feature of an offset reflector geometry.

Anechoic chamber evaluation
K. Haner, November 1994

This paper details the evaluation of a major aerospace company's tapered anechoic chamber. Using an NSI 3' x 3' near-field scanner and software, the chamber was evaluated at 11 frequencies and two polarizations. SAR imaging techniques were used to map the chamber reflections. A new addition to the software provided the ability to map the difference between the measured phase front and the theoretical spherical phase front; the software also derives the x,y,z phase centers of the source. Error estimates for all aspects of the evaluation will be discussed.

CASA space division test range evaluation
A. Montesano,C. Montesano, L. de la Fuente, R. Torres, November 1994

In this paper it is presented the measurements performed on the prototype of the ERS-1 SAR antenna to verify the behaviors of the CASA-Space Division test range described during 1992 AMTA Symposium [1]. The prototype was provided by European Space Agency for this purpose and it has been measured in three different modes supported by the test range (spherical near field, planar near field and fresnel zone field). Results are compared with previous measurements available from other laboratories (TUD, ERICSSON).

Probe compensation characterization and error analysis in cylindrical near-field scanning
Z.A. Hussein, November 1994

A novel computer simulation methodology to properly characterize the role of probe directivity/pattern compensation in cylindrical near­ field scanning geometry is presented. The methodology is applied to a linear test array antenna and the JPIJNASA scatterometer (NSCA1) radar antenna. In addition, error analysis techniques of computer simulation and measured have been developed to determine the achievable accuracy in pattern measurements of the NSCAT antenna in cylindrical near field.

Analysis of amplitude dispersion in radar scattering using preconditioned linear prediction
M.J. Gerry,E. Walton, November 1994

Radar scattering can be modeled as a sum of contributions from a finite number of canonical scattering centers. These canonical scattering centers (edges, corners, specular points) all have different amplitude behavior as a function of frequency. We completely characterize this behavior with a single parameter in a parametric model of the scattering data. The estimation of this amplitude dispersion parameter along with down range location and rela­ tive amplitudes is presented.

20 GHz active phased array characterization
J.P. Kenney,E. Martin, L.D. Poles, November 1994

The radiation characteristics for an active phased array receive antenna operating at K Band were measured at the Ipswich Research Facility. On-pole and cross-pole radiation patterns were measured for several scan angles. In this paper we'll discuss the general design of the antenna and the instrumentation ensemble used to perform the far field and near field characterization of this antenna. Measurements taken on a 2600 foot far field range vs. a near field planer scanner are compared.

Joint STARS phased array antenna measurements at IF
J., III. Pantalone, November 1994

Norden Inc. has developed and instrumented its JSTARS 1000' Outdoor Antenna Range with a multi-port antenna measurement system designed to acquire antenna data (patterns and other related signals) at the antenna's respective radar system's intermediate frequency (IF). The measurement system utilizes the JSTARS RF microwave receivers attached to the multiple channels of the JSTARS antenna. These receivers obtain the RF signal from these multiple channels and provide the IF signals to the measurement system.

High speed multi-frequency antenna measurements in the MDTI radar measurement center
J.D. Weatherington, November 1994

This paper demonstrates a high speed antenna measurement capability recently developed in the MDTI Radar Measurement Center. Originally constructed as a Radar Cross Section facility, the RMC has added the capability to measure antenna patterns on apertures up to 40-feet in length in the far field. Data will be presented to demonstrate system performance through the use of modern output formats, such as global plots and videotape presentations.

Three-dimensional radar cross section imaging
R. Harris,B. Freburger, C. Zappala, M. Lewis, November 1994

Three-dimensional imaging capability has recently been added to METRATEK's Model 200 RCS Diagnostic Radar. This paper describes the rationale and methodology for producing three­ dimensional images and gives sample images taken with the system.

Enhanced high resolution radar imaging
J.W. Odendaal,E. Walton, I.J. Gupta, November 1994

Radar with the 2-D Fourier trans- form of the scattered field data in frequency and/or have poor resolution. A modified brid method and a modified 2-D AR technique are proposed to high radar images us- limited backscattered field data. The final image presents the scattering properties of the target in a quantitative way. The peaks in the image represents the positions of centers contributing to the backscattered field. Furthermore, the amplitudes of the peaks correspond to the intensities of the scattering centers.

Characterization of a dual circularly polarized, dual plane monopulse, millimeter wave antenna
J.B., Jr. Johnson,W.S. Albritton, November 1994

The characteristics of dual circularly polarized, dual plane monopulse, millimeter wave antennas are being measured at the U.S. Army Redstone Technical Test Center. This paper will describe the instrumentation suite which allows for simultaneous collection of sum and differenee data in both planes. Also discussed is special antenna under test interfacing requirements, and compact antenna test range facilities

Database program for organization, presentation and distribution of measured antenna and RCS pattern data, A
S. Mishra,C.L. Larose, C.W. Trueman, M. Flynn, November 1994

Details of a public domain Microsoft Windows-based database program to organize and distribute measured antenna pattern and RCS data are described. Tools for editing, viewing and plotting data are also included.

Design aspects of cylindrical near-field measurement system
S. Christopher,A. Kaul, K.U. Limaye, S.S. Rao, V.V.S. Prakash, November 1994

This paper presents the various aspects involved in the design, development and establishment of Cylindrical Near-Field Measurement(cnfm) facility. A brief description of the hardware and the method of data acquisition are outlined. The capabilities of the CNFM system are brought into focus. The effects of alignment errors are presented. The patterns of various test antennas are presented over different frequency bands.

A Dual-frequency millimeter-wave radiometer antenna for airborne remote sensing of atmosphere and ocean, A
M.H. Francis,D. Kremer, D.A. Hazen, L.S. Fedor, M.D. Jacobson, W.B. Madsen, November 1994

Accurate multiwavelength radiometric remote sensing of the ocean and the atmosphere from an aircraft requires antennas with the same beamwidth at the various frequencies of operation. Scientists at the National Oceanic and Atmospheric Administration designed an offset antenna with a pressure-compensating corrugated feed horn to meet this criterion. A specially designed fairing was incorporated into the antenna to optimize the aerodynamics and minimize the liquid buildup on the antenna surfaces. The antenna has two positions: the zenith (up) position and the nadir (down) position. The planar near-field facility at the National Institute of Standards and Technology was used to determine the far-field pattern of the antenna. The results show that the antenna beamwidths at 23.87 and 31.65 GHz are nearly the same as expected from the design criterion. This antenna was recently used in an ocean remote-sending experiment and performed according to expectations.

Ultra low sidelobe antenna measurement error correction technique, An
W.D. Burnside,I.J. Gupta, November 1994

Ultra low sidelobe antenna measurements are very difficult to perform even in the best of ranges. This problem results from the fact that small stray signal errors within the range can be amplified by the antenna main beam gain and result in a error term that is larger than the desired ultra low sidelobe level. With this in mind, one can attempt to reduce the range stray signals, but it is only practical to reduce them so far. However, one can always desire to measure a lower sidelobe level than is feasible for the range. To correct this problem, a new measurement method has been developed that can significantly reduce these. It involves taking two measurements and properly processing the results. It has been shown that one can reduce complex range errors by as much as 35 dB in a real range environment.







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