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.)
A sophisticated software package FARANA (FAR-field ANAiysis) is presented for transforming planar near-field test data to far-field antenna patterns, including enhanced analysis of far-field results. FARANA is coded in MATLAB version 5.0. MATLAB (MATrix LABoratory) is an interactive mathematical modelling tool based on matrix solutions without dimensioning. Using MATLAB, numerical engineering problems can be solved in a fraction of time of time required by programs coded in FORTRAN or C. FARANA operates with a state-of-the-art graphical user's-interface, is intuitive to use and features high speed and accuracy. This paper addresses an assessment of the program, discusses its use and enhanced far-field analysis capabilities.
We describe a technique which uses field intensity patterns formed by the interference of an unknown test antenna and a known referenceantenna - holograms in the classical optical sense - for determining the far-field pattern of the unknown antenna. The field intensity is measured by acquiring an infrared picture of the tem perature distribution on a resistive screen heated by incident microwave energy. The output of the camera is processed to yield the electric field intensity on the surface of the resistive screen. Required measurements are the field patterns of the unknown antenna and two holograms taken with relative phase differences between the reference and unknown antennas of 0° and 90°. In addition, the amplitude and phase of the reference field at the measurement plane are needed. These can be obtained from a separate measurement of the reference using standard near-field techniques. The algorithm gives the complex near field of the antenna under test which can then be processed to obtain the far-field pattern of the antenna under test. We present results showing far-field patterns which acceptably reproduce the main beam and near sidelobes. Such techniques will allow rapid testing of certain antenna types.
The mechanical rotator must be correctly aligned and the probe placed in the proper location when performing spherical near-field measurements. This alignment is usually accomplished using optical instruments such as theodolites and autocollimators and ideally should be done with the antenna under test mounted on the rotator. In some cases it may be impractical to place the alignment mirrors on the AUT or optical instruments may not be available. In these and other cases, it is desirable to check alignment with electrical measurements on the actual AUT and probe. Such tests have recently been developed and verified. Appropriate comparison and analysis of two near-field measurements that should be identical or have a known difference yields precise measures of some rotator and probe alignment errors. While these tests are independent of the AUT pattern, judicious choice or placement of the antenna can increase the sensitivity of the test. Typical measurements will be presented using analysis recently included in NSI software.
When a planar near-field measurement is done, errors are introduced due to imperfections in the mechanical and electrical parts of the measurement equipment. In order to identify the characteristics of different types of errors, a MatLab program that simulates the near-field from an antenna has been developed. The near-field is transformed to far-field and the errors are evaluated. This paper looks into four different error types: 1) Truncation errors (if the measurement surface is to small the near-field will be truncated before it reaches adequately low levels), 2) Probe-AUT distance errors (fluctuations in the probe AUT distance over the measurement surface), 3) Zigzag errors (due to data being acquired during both travel directions of the probe), 4) I,Q amplification errors (different amplification for the I and Q channels in the receiver). The results are presented in plots which illustrate where in space the largest antenna pattern errors occur.
A series of measurements to validate the performance of a Vertical Planar Near-field Antenna Test Range located at the Hughes Space and Communications Company (HSC) was performed. These measurements were made as part of a task to provide validation of this particular range for detailed Production Antenna Testing. This validation was required in preparation for measuring a particular flight antenna. The range validation consisted of a series of self comparison tests and far-field range pattern comparison tests using an offset reflector antenna as the validation antenna. This antenna had been previously measured on a far-field antenna range which is in constant use to test flight antennas. This paper describes the range validation tests and presents some of the results. Comparisons of some far-field patterns measured on the validation antenna at both the far-field and near-field ranges is presented.
NSI recently delivered a Turnkey Near-field Antenna Measurement System (TNAMS) to the Naval Surface Warfare Center - Crane Division (NSWC-CD) in Crane Indiana. The system supports characterization and calibration of the Navy's active array antennas. TNAMS includes a precision 12' x 9' vertical planar near-field robotic scanner with laser optical position measurement system, dual source microwave instrumentation for multiple frequency acquisition, and a wide PRF range pulse mode capability. TNAMS is part of the Active Array Measurement Test Bed (AAMTB) which supports testing of high power active arrays including synchronization with the Navy's Active Array Measurement Test Vehicle (AAMTV), now under development. The paper summarizes the hardware configuration and unique features of the pulse mode capability for high power phased array testing and the TNAMS interface to the AAMTV and AAMTB computers. In addition, range test data comparing antenna patterns with various pulse characteristics is presented.
A new edge treatment approach using resistive cards (R-cards) for compact range reflectors is introduced in this paper. This new treatment has proven to be successful in achieving the design goal of reducing the diffracted fields from the reflector edges in the quiet zone. The design key of this new treatment relies on the proper choice of both the resistance distribution and placement of the R-cards in front of the reflector edge. Preliminary analysis and design studies show the potential of this new treatment in reducing the ripple level in the target zone over a wide range of frequencies. The simplicity, flexibility and the low cost of this new approach provide a viable alternative approach to the other edge treatments, such as serrated or blended rolled edges.
Previous researchers have demonstrated the ability to probe the range field illuminating an antenna under test (AUT) on the surface of a sphere and to calculate the spherical wave coefficients from these measurements. This paper, describes a technique for obtaining a plane wave model of the range using these spherical wave coefficients. An algorithm for creating this plane wave model is presented and a plane wave model for a measured range field is shown. A plane wave spectrum of the range field is calculated and the directions of the largest peaks of this plane wave spectrum are used as initial guesses for the direction of plane waves. The directions of incidence of these plane waves are optimized such that the least square error between the range spherical wave coefficients and plane wave model spherical wave coefficients is minimized. An example of a measured range is presented which consists of a horn range antenna and a smaller horn as an extraneous source located approximately 20 degrees off the range axis. The plane wave model is used in a range compensation algorithm described in a companion paper.
Leader in the field of space environment simulation (vibrations, thermal vacuum, acoustics, EMC), INTESPACE company has built a new compact range for antenna measurement called MISTRAL with a view to providing an overall satellite test service. The purpose of this new full-scale test facility is to determine the radioelectric characteristics of integrated satellite antennas covering : - classic antenna tests such as radiation pattern and gain measurement, - payload-specific end-to-end tests such as EIRP, SFD, GIT, Gain/Frequency, etc. The aim of this paper is : - first, to present the main and extra features of the MISTRAL compact range, - second, to show the major improvements and system optimization achieved through the study and development phases of MISTRAL, - third, to present the results of the intensive acceptance tests (quiet zones probing and antennas measurements) confirming the high quality of the test facility.
This paper presents a design of dual shaped reflector feed system suppressing cross polarized components for compact antenna test range(CATR). This system consists of a parabolic main reflector, two shaped reflectors and primary horn. As for co-polarization characteristics, these subreflectors are shaped to achieve a plane wave with uniform amplitude in a test zone. As for cross polarization characteristics, cross polarized components are eliminated in following way. An initial reflector system before shaping is satisfied with a condition of eliminating cross polarized components based on a beam mode expansion technique. This condition needs more than three quadratic reflectors, and frequency independent design can be derived. In this paper, the effect of higher order modes are considered. When shaping reflectors, however, additional cross polarized components are generated and the condition of eliminating cross polarized components is not satisfied. In this paper, a correction method of the cross polarization is also presented. A design result shows that the system has a test zone of 2.5m diameter and in test zone, lower ±0.5dB amplitude ripple, ±4.5° phase ripple and lower -44dB are achieved.
Scientific-Atlanta has recently begun work on a large 55 ft.(W) x 45 ft.(H) compact range reflector. The reflector is a Model 5738 with a 45 ft. focal length and a 38 ft. diameter by 38 ft. long cylindrical quiet zone. Due to the large size of the reflector, it is necessary to form the surface as several large, independent sections and assemble and align the reflector at the installation site. The 5738 reflector is shown in Figure 1 with the 38 ft. quiet zone superimposed. Figu re 1. Front View of 5738 Reflector Showing Sections The independent and predictable behavior of large sections proves to be very beneficial for performing an electrical alignment of the reflector based on field probe phase data. This paper discusses the required alignment tolerances and analytic tools developed to predict the effects on quite zone performance due to alignment errors in the sections of the reflector.
The ESA Compact Payload Test Range (CPTR) has been designed to allow scanning of the range axis by means of the movement of the feed in the focal region. This capability has been applied to the verification of the performance of the Inter Orbit Link Antenna (IOLA) signal acquisition and tracking system, known as the IAPS, of the ARTEMIS communication satellite. The feed of the CPTR was used to simulate the Ka band signal transmitted from a low earth orbit satellite. The paper describes the test scenario and requirements, as well as presenting the scan performance of the ESTEC CPTR. The scan performance was verified by comparing azimuth scanned patterns of the main beam with those made translation of the feed in the focal region.
This paper presents a new technique for performing range compensation of full sphere antenna patterns measured on fixed line-of-sight antenna ranges where pattern measurements are made over a spherical surface. Such ranges include far-field, compact, and spherical near-field ranges. A plane wave model of the range field illuminating the antenna under test (AUT) is determined as described in another paper. This plane wave model consists of a small, selectable number of plane waves. Equations are given describing the transformation of range coordinates to AUT coordinates. This allows the response of an AUT to a plane wave from an arbitrary direction to be defined using only the far-field pattern of the AUT. The error pattern added to the pattern measurement by the extraneous plane waves is then estimated using the plane wave model and the measured pattern. This error pattern is subtracted from the antenna pattern measurement to obtain a compensated pattern. The compensated pattern and error pattern are improved iteratively. This paper demonstrates the technique using simulated data. The rotation of the spherical AUT grid with respect to the range grid during the measurement requires an interpolation of the measured fields to estimate the error pattern. Investigations of interpolation error are presented. The computational complexity of the compensation algorithm, excluding the plane wave model, is on the order of the number of measurement points on the spherical measurement grid. K
Cellular and PCS basestation antennas are basically arrays with highly directive elevation patterns and broad azimuth patterns. This causes measurement problems because they are large but not directive in both principal planes. As a result, the pattern measurements of these antennas that have been performed outside have been unreliable in many cases because they are very receptive to interference and range clutter. Thus, one wants to move inside but the antenna size can significantly impact the overall range cost. This paper describes a very practical solution to this problem. Since basestation antennas are long and narrow, one can use a near field scanner approach to deal with the length. In fact by using a sectorial horn probe, the narrow dimension of the antenna-under-test is illuminated by a cylindrical wave. Thus, the scanner need only probe the field along the antenna length. This linear scan data can then be transformed to generate the desired far field elevation pattern. The details of this novel design will be described as well as the results, to illustrate the system capability and accuracy.
The Ohio State University ElectroScience Laboratory participated along with the Center for Intelligent Transportation Research as one of six teams to demonstrate an automated highway concept at the National Automated Highway Demo at San Diego in August, 1997. The forward looking radar concept which was demonstrated used the FSS highway stripe which was presented at the 1995 AMTA Meeting. This paper describes the radar system as implemented for automated guidance, and presents measured results on the system antenna array and on the system itself. In addition, results of the demonstration in San Diego will be discussed. The radar used a monopulse guidance architecture, where the amplitude from left and right receive antennas are subtracted, and then divided by the sum of the left and right antennas in order to provide a normalized steering error signal. The antenna array used a single transmit horn, and a matched pair of receive horns, all vertically polarized. All three antennas were nestled into the composite front bum per beam, looking out through a foam radome panel about the size of a license plate. Performance data on the antennas and the steering sensing information will be presented. The radar system was a chirp radar covering a frequency spectrum of 10 to 11 GHz. The narrow frequency of the FSS radar stripe occu rred at 10.95 GHz, allowing its signature to be distinguished from the return of vehicles and other objects out in front of the vehicle. Radar system measured results in the highway situation will be presented, and its performance in San Diego will be discussed.
In this paper we will compare different techniques that can be used to measure the performance of automobile antennas. The use of indoor scale-model and outdoor full-scale range measurements will be discussed. These rangetype techniques characterize the engineering parameters of the antenna using signals with well defined polarizations and angles of arrival. These techniques are important in the initial stages of the antenna development. In the final stages of automobile antenna development, it is important to know how well the antenna will perform in the "real-world". We have developed mobile measurement techniques that use commercial off-the-air signals to characterize the performance of the automobile antenna in the real-world environment. We will describe three different systems that were developed to measure the performance of AM/FM, cellular, and GPS antennas.
Until now the mobile phones have been qualified by power measurement at the RF-connector of the handset without any regard to the antenna characteristic and the losses caused by the mismatch of the impedance matching network. IMST is exammmg, via measurements, the user's influence on the antenna pattern of the mobile phone. These measurements were performed in the transmit situation and in the receive situation of the mobile phone at different elevation angles and for different channels of the German E Plus-Network. Due to the differences between human bodies and due to the body's movement during a measurement, the emphasis of this investigation was on the development of a model with dimensions and electromagnetic characteristics similar to those of the average human body. By comparing measurement results using different test persons and the model, the validity of the model has been evaluated.
A technique was developed to recover the near-field function on a larger data set than the one that is measured. It requires the preliminary determination of functions containing the information relating the two data sets. The simplest way of obtaining such a function is to measure the near-field function on the larger and the smaller data set. This seems to be a drawback to the technique. However. after making one such pair of measurement it is therefore non necessary to do so again and the field of the antenna can be obtained, from the smaller data set measurement, with comparable accuracy. The technique is somewhat different when compensating for a sampling rate reduction. However, in both cases an analytical extension is required to fill the desired domain of definition, followed by a division. In the case of the sampling area the division of the spectral functions f2 by f1 is made in the spectral domain while in the case of the sampling rate the division of the near-field functions E' by E is made in the near-field domain. An experiment was performed to demonstrate the applicability of the above technique. A full near-field measurement of a linear array antenna was performed and processed, then after displacement of the antenna, measurements were done, in one case, on a truncated smaller scan area, and in another case with a larger sampling interval. The technique was applied to recover the complete far-field characteristics of the antenna from the smaller data set. The far-field characteristics of the antenna obtained by this technique were shown to be very similar to the results obtained from a more complete near field measurement.
A method is presented for computing far field antenna patterns from spherical near field antenna measurement data. The new method utilizes a novel Uniform Geometrical Theory of Diffraction (UTD) based transformation of spherically scanned antenna tangential electric (or magnetic) near field measured values to more efficiently obtain the antenna far field. Examples illustrating the accuracy and speed of UTD based spherical near to far field transformations for large to moderately large antennas are presented.
Phase space representation (PSR) is introduced as a diagnostic tool for near-field antenna measurements. The PSR of a linear scan is defined as a two dimensional function of position and wavenumber. This combined spatial-wavenumber distribution can reveal features which are not directly visible in either spatial- or wavenumber-domains. It is shown that PSR is useful for both error diagnostic and compensation of certain errors. In particular, the benefits of PSR in identifying aliasing, spatial errors, multiple AUT-probe reflections, and random errors in amplitude and phase will be demonstrated. The capability of the PSR in compensation of contaminated measurements is demonstrated by examples.