AMTA Paper Archive


Welcome to the AMTA paper archive. Select a category, publication date or search by author.

(Note: Papers will always be listed by categories.  To see ALL of the papers meeting your search criteria select the "AMTA Paper Archive" category after performing your search.)


Search AMTA Paper Archive
    
    




Sort By:  Date Added   Publication Date   Title   Author

AMTA Paper Archive

Spherical Coordinate Systems for Defining Directions and Polarization Components in Antenna Measurements
A.C. Newell, November 1998

The results of theoretical calculations or measurements for antennas are generally given in terms of the vector components of the :radiated electric field as a function of direction or position. Both the vector components and the direction parameters must be defined with respect to a coordinate system fixed to the antenna. Along the principal planes there is no ambiguity about the terms such as vertical or horizontal component, but off the principal planes the definition of directions and vector components depends on how the spherical coordinate system is defined. This paper will define four different spherical coordinates that are commonly used in measurements and calculations, and propose a terminology that is useful to distinguish between them, and define the mathematical transformations between them. These concepts are essential when the results of different measurements or calculations are compared or when an antenna's orientation is changed. Both mathematical and graphical representations will be presented.

ERP Measurement Issues
R.B. Dybdal, November 1998

Measurements of the ERP radiated by an antenna and the ERP received from a distant antenna are addressed. Alternative measurement techniques are described and correction for polarization mismatch loss, pointing error and propagation loss is discussed. The statistics of the measurement errors are presented for error budget projections of measurement accuracy.

Precision Boresight Measurements for Doppler Radar Systems Measured on a Near-Field Range
V. Moore,B. Schluper, November 1998

Airborne Doppler Velocity Sensors require precise boresight information in determining a Doppler solution. Far-field ranges have been extensively used to provide this boresighting capability. This paper discusses an empirical investigation to determine the feasibility of using near-field techniques to fulfill the boresighting requirement.

Fresnel-Zone Measurement and Analysis of a Dual-Polarized Meteorological Radar Antenna
D.B. Hayman,G.C. James, T.S. Bird, November 1998

The use of dual polarization in meteorological radars offers significant advantages over single polarization. Recently a standard single-polarization Cuband radar was upgraded to operate in dual-polarization mode. The antenna has a 4.2m diameter parabolic reflector with a prime-focus feed. A spherical Fresnel-zone holographic technique was used to obtain the radiation pattern for the upgraded antenna. The sidelobes were higher than predicted and so the data was analyzed to identify the relative contributions of shadowing from the feed crook and surface errors in the dish. This paper describes practical considerations in the measurement of this antenna and the analysis of the results.

Normalized Impluse Patterns for Several UWB Antennas
J.D. Young,J.S. Gwynne, November 1998

Two normalized pattern functions appropriate to Ultra-Wideband (UWB) antennas were discussed at the 1992 AMTA meeting [1]. The normalized pattern spectrum is an image showing radiated signal intensity as a function of azimuth or elevation angle and frequency. The spectrum is complex, and thus requires both an amplitude spectrum image and a phase spectrum image to be complete. It is normalized by dividing by the complex radiated signal at the defined boresite angle for the designated antenna. Therefore, on boresite, the normalized pattern spectrum is unity. The normalized impulse response pattern function is the Fourier Transform of the normalized pattern spectrum. This image plots intensity(and polarity) of the real impulse response of the antenna vs time and angle. On boresite, it is a band-limited impulse corresponding to the normalized pattern spectrum. This paper will discuss measurements of seven UWB antennas, and present normalized pattern results of these antennas. The antennas include both off-the-shelf products and experimental prototypes. Included are antennas which have been used for wide-angle UWB SAR imaging, a coherent UWB application where both signal attenuation and dispersion vs angle are important. The results show how pattern behavior can be separated from boresite transfer function information, and how antennas compare in this compact image format.

Uncertainties in Measuring Circularly Polarized Antennas
P.R. Rousseau, November 1998

Three common methods of measuring circularly antennas on a far-zone range are: using a spinning linear source antenna (SPIN-LIN), measuring the magnitude and with a linearly polarized source antenna in two orthogonal positions (MAG-PHS), and using a circularly polarized source antenna (CIRC-SRC). The MAG-PHS and CIRC-SRC methods are also used in a near-field or com­ pact range. The SPIN-LIN method is useful because an accur te measurement of the axial ratio and gain can be made without the need to measure phase. The MAG-PHS method is the most general method and can also completely characterize the polarization of the test antenna. The CIRC-SRC method is the simplest and least time-consuming measurement if the antenna response to only one polarization is needed. The choice of measurement method is dictated by schedule, accuracy requirements, and budget. An analysis is presented that provides errors in the measured gain, relative gain pattern, and phase of the test antenna depending on the polarization characteristics of the source and test antennas. These results are useful for deciding which measurement method is the most appropriate to use for a particular job. These results are also useful when constructing more complete error budgets.

Quantifying the Effect of Position Errors in Spherical Near-Field Measurements
A.C. Newell,G. Hindman, November 1998

Concise mathematical relations have been derived for Planar Near-Field measurements that quantify the effects of x, y and z-position errors on antenna parameters such as gain, sidelobe level, pointing, and cross polarization. Because of the complexity of the theory, similar relations for spherical near-field measurements have not been developed. The requirements for the spherical coordinate system are generally defined in terms of the alignment parameters such as orthogonality and intersection of axes, q-zero, x­ zero and y-zero rather than individual errors in q , f and r. Mechanical, optical and electrical techniques have been developed to achieve these alignments. This paper will report on the development of methods to estimate the antenna parameter errors that will result from spherical alignment errors for typical antennas.

DATE - Depot Aperture Tuning Equipment for the ERIEYE Airborne Early Warning System
H. Eriksson, November 1998

DATE is a portable, rapid assembled, planar near field measurement system for ERIEYE Airborne Early Warning System. DATE shall be used both as a production range at Ericsson Microwave Systems (EMW) and as a maintenance equipment delivered with the ERIEYE AEW System. Up to now ERIEYE has been measured and phase aligned at EMW's large nearfield range. The active antenna is interfaced through a Beam Steering Computer (BSC) and hardware interface. The disadvantages with this approach is a slow communication speed and reduced Built In Test. Since the large nearfield range is designed to meet the requirements from many different antenna types the transport, mounting, alignment and range error analysis are very time and personnel consuming. The DATE-scope is to provide a portable planar near field test system that's custom-made for ERIEYE. The time from stored system to completed measurement shall be very short and performed by a "non antenna test engineer". This is done by: • Incorporate the BSC as a radar-mode. • Use the radar receiver and transmitter for RF­ measurement. • Reduce alignment time and complexity by a common alignment system for antenna and scanner. Scanner alignment for very high position accuracy. • Automatic Advanced Data Processing: Transformation from near field to far field to excitation to new T/R-module setting-up-table in one step.

Low-Cost Portable Near-Field Antenna Measurement System
D.P. Woollen,A.R. Tillerson, G. Lear, J.M. Snow, W. Slowey, November 1998

The Marine Corps desired a portable test system for the AN/TPS-59 radar antenna (a large, 15.2 feet by 29.1 feet, L-band phased array antenna) to verify on site performance. The test system was also required to be capable of antenna acceptance testing at the overhaul depot. An innovative mechanical design using commercial off-themshelf (COTS) products paved the way for the development of this low-cost system. The low-frequency, moderate-sidelobe antenna characteristics allowed for flexibility in mechanical scanner design. The near-field scanner attaches directly to the antenna and is aligned in place. The Hewlett-Packard 8530 Antenna Measurement System is employed for data collection. An interface from the computer to the antenna was designed for beam­ steering control (BSC). LabVIEW software controls the HP8530, the near-field scanner, BSC, and other miscellaneous RF hardware. Digital Visual Fortran 5.0 and Matlab are used to run the National Institute of Standards and Technology (NIST) near­ field programs.

Probe Calibration Using Time Domain Gating and Off-Bench Optical Alignment
A. Haile,J.C. Nichols, S.A. Marschke, November 1998

Probe correction is required to accurately determine the far-field pattern of an antenna from near-field measurements. At Raytheon Primary Standards Laboratory (PSL) in El Segundo, CA, data acquisition hardware, instrument control software, and a mechanical positioning system have been developed and used with an HP Network Analyzer/Receiver system to perform these measurements. Using a three antenna technique, the on-axis and polarization parameters of a linearly (or circularly) polarized probe are calibrated. The relative far-field pattern of the probe is then measured utilizing the two nominal, orthogonal polarizations of the source antenna. All measurements are stepped in frequency and use a time domain gating technique. The probe and the source antenna are optically aligned to the interface and unique, kinematic designed interface flanges allow repeatable mounting of the antennas to the test station.

Application of Phase-Space Filters to Planar Near-Field Antenna Measurements
A. Moghaddar, November 1998

Phase-space expansion of spatial near-field data is an expansion into functions that are spatially and spectrally localized. We have previously shown that such a phase-space representation (PSR) can be useful for both antenna radiation phenomenology and evaluating the quality of planar near-field measurements. In this paper, we use the coefficient of a phase-space expansion for filtering. It will be shown that the contribution of some error components is stronger in a particular region of the phase-space. One can take advantage of this fact for phase-space filtering. Two sources of error, namely staggered data grid, and.AUT-room interaction; are considered in this paper. For imperfect probe spacing, we shall show that this technique is particularly attractive when the true probe location is unavailable. In the second example, we shall show that the PSR filtering can reduce the side lobe contamination due to AUT/room interactions.

Phase Correction of Volumetric Antenna Pattern Measurements with Validation by Computer Analysis
T-H Lee,C.W.D. Chuang, W.D. Burnside, W.H. Theunissen, November 1998

Practical antenna applications require accurate characterization of the antenna, including both the amplitude and phase performance. Recent advances in antenna measurement technologies allow the antenna to be measured in various indoor facilities with a well controlled environment. However, measurements that take a long time to complete can still suffer phase drift and variation due to the movement of RF cable as well as changes in the chamber environment. Without proper phase correction, the measured antenna pattern performance may not satisfy the desired requirement. Consequently, it is very important to have appropriate methods for phase correction in order to obtain more accurate results. In this paper, a simple procedure for phase correction of volumetric spherical near field antenna measurement is presented. In this method, only a few additional measurements are needed for correcting the phase variation observed in the original volumetric pattern. Application of the phase corrected pattern has been found to satisfy the desired antenna performance.

Experimental Validatoin of a New Technique to Reduce the Truncation Error in Near-Field Measurement Techniques
O.M. Bucci,G. D'Elia, M.D. Migliore, November 1998

The technique is based on a non-redundant and non-uniform representation of the near-field on the measurement plane and performs an estimation of the fields samples outside the measurement region. Thanks to the non-uniformity distribution of the samples, also the estimation of a limited number of them allows a significant improvement in the far field reconstruction. The numerical and experimental investigation presented in this paper confirms the effectiveness and flexibility of the technique, which requires a low computational effort.

Locating Defective Array Modules Using Planar Near-Field Measurements
M.H.A. Paquay, November 1998

The backtransformation in (planar) Near Field processing is often claimed to be a very powerful tool for antenna diagnostics. Less known is a kind of defocusing effect which is introduced by the processing. Selecting the visible space in the Far-Field domain has a similar effect as a bandfilter in the frequency domain of an electric signal. In that analogous case it is better known that after the transform to the time domain, one has to deal with sin(x)/x behavior, limiting the resolution. The mathematics and convolution effects of both the one­dimensional time-frequency transform as the two­ dimensional Near-Field Far-Field transform will be explained. Some measurement procedures are proposed, including S/N requirements. It turns out that the back­ transformation technique has some nasty properties which limit the use for alignment purposes. Some alternatives are discussed.

Diagnosis of Aperture Antennas from Measured Near Field Data Using ESLEST Software
F. Las-Heras,B. Galocha, J.L. Basada, P. Caballero, November 1998

A microwave holographic technique based on equivalent magnetic sources reconstruction is presented. This technique, initially used as a main plane near-field to far-field (NF-FF) transformation, can also be used to detect defective elements in arrays as well as to detect irregularities in the surface of reflector antennas.

Measurement of the Sirius 2 Telecommunication Satellite Antenna
H.E. Gram,J. Karlsson, M. Dich, November 1998

The Sirius 2 telcommunication satellite was build in France by Aerospatiale. As a subcontractor Saab Ericsson Space (SES) developed the telecommunication antenna for direct television broadcast. The satellite was successfully launched November 13, 1997. Three antennas were manufactured by SES: a quality model (QM), a flight model (FMl) and a flight spare (FM2). Each antennas consists of a 1.4 meter in diameter shaped main reflector fed by a shaped subreflector and a dual polarized feed horn. For the test of the antennas, spherical near-field antenna test ranges located at Ericsson Microwave System (EMW)/SES in Sweden and at the Technical University of Denmark (DTU) were used. Each of the three antennas was measured twice. Between the two measurements mechanical and thermal tests were performed. The paper presents the measurements on the satellite antennas together with a discussion of the advantages of using the spherical near-field technique for this type of measurements. Compared to a far-field range the advantages are evident: At both SES and DTU a measurement distance of ten and six meters respectively were used on the indoor ranges. On a far-field range a measurement distance in the excess of 250 meters must be applied. To decrease the measurement time the near fields were only measured in a certain region on the near field sphere. The influence of this truncation will be discussed. Coordinate systems for the antennas were defined using mirror cubes. The RF measurements as well as the optical measurements on the cubes were performed without dismounting the antenna from the antenna positioner. The radiation patterns are therefore precisely decined with respect to the coordinate systems of the cubes.

Design and Validation of a General Purpose Near-Field Antenna Measurement Facility for the Royal Netherlands Navy
M. Hagenbeek,D.J. van Rensburg, November 1998

This paper describes a new multi-purpose planar & cylindrical near-field antenna test facility installed at the Royal Netherlands Navy (RNN). In this paper an overview is given of the initial list of requirements that was generated and the process of selecting the best type of measurement facility to address these. A description of the facility is given and an outline of the accuracy of the planar/cylindrical near-field scanner is presented. The paper contains details of the extensive validation program and measured data demonstrating the performance of the system.

Development and Applications of a 16 Channel UHF/L-band Noise Radar
E.K. Walton,S. Gunawan, November 1998

In this paper, we will demonstrate a 16 channel multi-antenna UHF/L-band noise radar system. We will show applications to building penetration and ground penetration. We will show noise radar responses for humans walking on the other side of building walls, and buried objects, including land mines. We will discuss classification techniques, and show some techniques that yield initial success.

Results from Inter-Laboratory Comparison Measurements at the Boeing 9-77 Range
M.D. Bushbeck,A.W. Reed, C.N. Eriksen, P.S.P. Wei, November 1998

Recently, RCS measurements were made of several common calibration objects of various sizes in the Boeing 9-77 Range. A study was conducted to examine the accuracy and errors induced by using each as a calibration target with a string support system. This paper presents the results of the study. Two of the objects, i.e., the 14"-ultrasphere and the 4.5"-dia. cylinder, are found to perform the best in that they exhibit the least departures (error) from theory. The measured departures of 0.2 to 0.3 dB are consistent with the temporal drift of the radar in several hours.

Full Scattering Matrix Calibration with Error Analysis
R.J. Jost,R.F. Fahlsing, November 1998

Calibration of monostatic radar cross section (RCS) has been studied extensively over many years, leading to many approaches, with varying degrees of success. To this day, there is still significant debate over how it should be done. It is almost a certainty, that if someone proposes a way to calibrate RCS data, someone else will come up with reasons as to why the "new" approach will not yield results that are "good enough." In the case of full scattering matrix RCS measurements, the lack of information concerning calibration techniques is even greater. The Air Force's Radar Target Scattering Facility (RATSCAT) at Holloman AFB, NM,has begun an effort to refine monostatic and bistatic cross polarization measurements at various radar bands. For the purposes of this paper, we have concentrated on our monostatic cross polarization developments. Such issues as calibration targets and techniques, system stability requirements, etc. will be discussed. During several programs we have attempted to collect sufficient data to do full scattering matrix corrections. In a previous paper, "Bistatic Cross-Polarization Calibration," our collected data had a high background which obscured much of the cross polarized return. The data presented here is from a program conducted at RATSCAT recently which utilized the Ka band. Because of the sensitivity of measurements at Ka to many effects, an error estimate was required. This paper presents this error estimation and some results of full scattering matrix correction of RCS data. This analysis is based upon "The Proposed Uncertainty Analysis for RCS Measurements", NISTIR 5019, by R. C. Wittmann, M. H. Francis, L. A. Muth and R. L. Lewis. This paper was aimed at principle pole measurements, e.g. HH and VV. The tabular data presented in the paper are from this paper with additions for errors associated with cross polarization and cross polarization correction.







help@amta.org
2024 Antenna Measurement Techniques Association. All Rights Reserved.
AMTA_logo_115x115.png
 
 

CONNECT WITH US


Calendar

S M T W T F S
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31