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Millimeter wave antennas are typically small in physical cross-section, and thus require only a small quiet or test zone illumination area when undergoing standard antenna tests. Lockheed Martin Missiles and Fire Control had a requirement for a test zone diameter of less than 1 foot in order to test millimeter wave antennas required as part of research and development programs. ORBIT/FR developed a unique portable test facility that is inclusive of a “minicompact range” reflector system featuring a rolled edge design with a nominal 12 inch diameter quiet zone. The compact range is integrally mounted into a portable anechoic chamber assembly that measures 60”H x 52”W x 84”L. The chamber features a “hatch” type opening that allows easy access inside the chamber interior, and the entire assembly is easily relocated using a built-in set of casters. An AL-060-1P miniature positioner allows for feed polarization adjustment, and an AL-160-1 provides azimuth rotation for the antenna under test. Corrugated feeds allow precise control of the reflector illumination within the small chamber assembly, allowing excellent quiet zone performance to be realized. Although the primary frequency band of operation is Ka band, the reflector exhibits excellent performance at Ku band, and is capable of operating down to X band as well. The integrated facility is utilized with the Agilent Performance Network Analyzer (PNA) and the 959Spectrum Antenna Measurement Workstation to provide a complete small antenna, high frequency measurement solution. A detailed description of the system, as well as performance results, are presented in this paper.
This paper presents an evaluation of the suitability of the 65-foot range for the measurement of the far-field radiation characteristics of antennas located above a sea water half space. The 65-foot range corresponds to the measurement distance of the Overwater Antenna Measurement Facility (Arch) at the Naval Undersea Warfare Center (NUWC) Division, Newport, RI. Four antennas are investigated at the 200- to 400-MHz frequency range for antenna base heights ranging from 0 to 20 feet above sea water. The results presented are based on thin-wire model representations of the antennas using the Numerical Electromagnetics Code (NEC), version 4.1. The radiation parameters investigated are the directive gain, axial ratio, direction of maximum gain, and the location and depth of the first null above the horizon. For each antenna, plots of the differences of the computed radiation parameters at the 65-foot and far-field ranges are given as functions of frequency for various antenna base height above sea water. It is anticipated that the results presented in this paper may be helpful for determining at what frequencies and heights the NUWC Arch will provide accurate far-field measurements for a given type of antenna.
In order to reach the desired degree of confidence in verifying the required aircraft flight clearances, according to military and civil international standards, Alenia Aeronautica have developed test facilities and EMC test areas which are suitable to perform conducted and radiated tests on fighter and transport aircraft seen as a whole system. Up to now, all tests performed at Alenia’s facilities are intended to be performed in open space, due to several constraints and limitations such as weather conditions effects and future higher EMC certification field level Alenia Aeronautica are designing and implementing a shielded/anechoic chamber, suitable for both HIRF/EMC testing on fighters without engines running and measurement of patter of the antennas mounted on aircraft. This paper includes the modern techniques and the new facility that Alenia Aeronautica are studying and developing at our division of Caselle South (Turin, Italy) are described.
A problem of determination of an antenna phase center (PhC) usually is solved by different ways from a theoretical calculation to the near-field measurements of complex characteristics in the aperture of an antenna or the far-field measurements of the radiation-pattern phase. The present paper is devoted to a general technique of an antenna PhC determination by use of the known (or the measured) distribution of the complex characteristics in the antenna near zone or the phase pattern in the far zone. An algorithm of determination of the phase pattern evolute, based on the lowest moments of distribution, as well as a criterion for PhC existence, which is independent on the observation angle, are offered. A simple expression of PhC for an antenna with a quadratic phase distribution in the aperture is obtained. An error of PhC determination depending on both the error of observation angle and the error of measurement of the phase pattern is considered.
This paper presents background information and experiment procedures for an antenna measurement laboratory course to be held in a new anechoic chamber at California Polytechnic State University. The lab consists of five experiments and one design project intended to give students practical experience with antenna measurement techniques and to creatively apply analytical skills to design, construct, and test antennas that meet given specifications. The experiments reinforce antenna principles including E-field polarization, antenna gain, radiation patterns, image theory, and frequency response. In addition to the experiment procedures, this paper presents the design and characterization of Helical Beam (RHCP and LHCP) and Discone antennas, a Dipole Antenna near Planar and Corner Reflectors, and Dipoles with and without a balun. These antennas demonstrate polarization, antenna gain, broadband matching characteristics, image theory, and feedline radiation due to unbalanced currents. Measured radiation patterns, gain, and axial ratio (helical only) show excellent correlation to theoretical predictions.
Rapid characterization and pre-qualification measurements are becoming more and more important for the ever-growing number of small antennas, mobile phones and other wireless terminals. There is a need driven by the wireless industries for a smart test set-up with reduced dimensions and capable of measuring radiating devices. Satimo has developed a compact, mobile and cost-effective test station called StarLab which is able to perform rapid 3D measurements of the pattern radiated by wireless devices. The StarLab equipment is derived from Satimo’s StarGate systems which are now well established spherical near field test ranges. StarLab uses a circular probe array to allow for real time full elevation cuts and volumetric 3D radiation pattern measurement within a few minutes. It is operating between 400MHz and 6GHz and can be configured for passive measurements and also cable less-active measurements. This paper describes in detail the multi-probe antenna test station and its different configurations for passive and active measurements. The accuracies for gain and power measurements are also presented as well as considerations on the total radiated power measured by the equipment. Additionally, calibration issues are discussed. Finally, measurements performed with the StarLab test station at Satimo are shown and illustrate the capabilities of the system. The measurement results are validated by comparison to the results obtained in other test ranges.
Since the early days of spherical near-field far-field transformations a recommendation for the necessary number of polar modes has been given by , being the wavenumber and or the radius of the minimum sphere. The almost explosive development in computer speed and storage capacity witnessed during the last two decades has made trans-formations of fields from antennas exceeding thou-sands of wavelengths feasible, and a closer investiga-tion of the above expression seems to be appropriate. An improved expression for the number of modes, N, related to the antenna size and the required accuracy will be developed. The impact of truncation of the modal expansion at a given level will be illustrated. This is especially important for measurements where noise is present, or where there is undesirable scatter-ing from objects.
The David Florida Laboratory (DFL) was contacted by the Canadian Department of National Defense (DND) to develop an accurate, reliable, more cost effective method of characterizing existing nose cone mounted radomes for the radar systems aboard aircraft such as CF-18. Traditionally, these measurements have been performed in a far-field (FF) [1] range using conventional positioning and measurement systems and specialized instruments such as a null seeker. Recently, the use of near field methods has been incorporated in radome measurement practices [2]. This paper describes one such adaptation of a cylindrical near-field facility (CNF) for radome measurements.
Geometries for measuring radome characteristics can usually be split into two categories. The first category always has the antenna inside the radome pointing along the range axis. The second category has the antenna maintaining a fixed relationship with respect to the radome during each scan of data. A facility can generally be designed to minimize measurement errors in one of the two geometries, but not both. Many facilities that permit collection of data in both geometries would benefit from the ability to dynamically capture data that lead to measurement errors, then compute and remove the associated errors. This paper discusses some of the primary error contributors in a dual-geometry radome measurement system, and suggests some mechanisms for capturing and potentially removing those errors.
ORBIT/FR is presently under contract to provide Alenia Aeronautics with the HIRF – EW test facility to perform radiated field immunity testing of aerospace vehicles with high electromagnetic field intensity: radiated emission measurements, which belong to EMC testing; electronic warfare and antenna pattern tests. This unique facility will combine specific EMC, EME, EW measurements as well as specific antenna measurements. An anechoic-shielded chamber therefore, represents the ideal solution to perform these tests, because it provides the electromagnetic shielding and protection against the internal and external electromagnetic environments. While in many cases as little as -10 dB of round trip reflection may be adequate for EMC testing applications, in the EW tests to be performed at frequencies higher than 500 MHz, is required a fairly lower level of reflectivity. The facility will include an anechoic-shielded chamber (ASC) where the System under Test (SUT) is installed and operated in its functional modes to perform susceptibility tests and emission tests. The ASC will be equipped with a turntable having the capability of arranging the System Under Test (SUT) in front of the radiating antennas at different aspect angles. The ASC will provide internal size of 30 x 30 x 20 (H) m. The pyramidal absorber material shall be permanently installed on ASC ceiling, vertical walls and doors. As far as the floor is concerned two configurations are possible: proposed facility. The model will be described and the effort to scale the performance of the full size absorbers. The development and fabrication of scale model antennas. The establishment of measurement techniques, which will allow the correlation of the scale model measurement to the computer model performance predictions and the potential performance of the completed full size chamber.
Frequency-Modulated Continuous-Wave (FMCW) Radar has traditionally been used in short range applications. Conventional FMCW radar requires the use of expensive microwave mixers and low noise amplifiers. A uniquely inexpensive solution was created, using inexpensive Gunn oscillator based microwave transceiver modules that consist of 3 diodes inside of a resonant cavity. However these transceiver modules have stability problems which cause them to be unsuitable for use in precise FMCW radar applications, when just one module is used. In order to overcome this problem, a unique radar solution was developed which uses a combination of 2 transceiver modules to create a precise FMCW radar system. This unique solution to FMCW radar is proven to be capable of determining range to target, and creating Synthetic Aperture Radar images.
This paper describes the development, testing and evaluation of a new, automated system for calibration and AUT alignment of a planar near-field scanner that allows the calibration system to remain in place during AUT measurement and which can be used to support AUT alignment to the scan plane. During scanner calibration, probe aperture position measurements are made using a tracking laser interferometer, a fixture that positions the interferometer retro reflector at a precise location relative to the probe aperture and a probe roll axis that maintains the proper orientation between the retro reflector and the interferometer as the probe position is moved. Aperture scan path information is used to construct a best-fit scan plane and to define a Cartesian, scanner-based coordinate system. Scan path data is then used to build a probe position error map for each of the three Cartesian coordinates as a function of the nominal position in the scan plane. These error maps can be used to implement software-based corrections (K-corrections) or they may be used for active Z-axis correction during measurements. By using a set of tooling points on the antenna mount, an AUT coordinate system is measured with the interferometer. The system then directs an operator through a set of AUT adjustments that align the AUT with the planar near-field scanner to a desired accuracy. This paper describes the implementation and testing of the system on an actual planar scanner and AUT test environment, showing the improvement in effective scanner planarity.
Accurate near-field calibration of a large 60 ft. diameter reflector can be accomplished with a minimal sampling technique. Near-field amplitude and phase is collected as the reflector scans across a receiving calibration tower. The near-field data is then transformed to a far-field pattern using a Fourier transform technique. Information on far-field EIRP, directivity, pointing, axial ratio and tilt, as well as encoder timing is obtained with accuracies comparable to anechoic chamber measurement techniques. The system was analyzed for sampling and multipath effects, as well as the effects of phase and amplitude stability. A spherical wave expansion technique was compared to a straight-forward summation technique for the Fourier transform.
Abstract — A technique for near-field measurements over a digital PCB is presented. Phase measurement with a vectorial network analyzer (VNA) is possible with antennas but it is in principle not possible when the DUT has its own free-running oscillator. In order to get around this problem, a two-probe approach is proposed. While one of the probes is mobile the other one is fixed and collect the reference signal. An analogue circuit must be used to obtain the specifications in power and phase of the reference signal of the VNA. The collected near field above the test circuit allows us to clearly identify the hot spots and the constant phase areas. These results could be used to find problematic spots on a board or to extrapolate the far-field. This is of practical interest in EMC testing of digital devices.
ABSTRACT This paper describes a novel optical boresighting and alignment system used to mechanically align antennas on a compact antenna range at the North Island Naval Air Depot in San Diego, CA. The antenna range has a 5-axis (roll/upper slide/azimuth/elevation/lower slide) positioner used to measure various airborne antennas for production testing. The video alignment system implemented on this range uses two video cameras outfitted with telephoto lenses, one on the roll stage and the other on an antenna-mounting fixture. The system has been demonstrated to yield an accuracy of ±0.005 degrees. Prior to the start of testing the positioner is commanded to a “0” position and the cameras focus on a fixed optical target to provide the operator with a quick visual confirmation that the positioner is accurately aligned prior to testing. The video alignment system described has numerous advantages over other mechanical alignment techniques, is low cost, easy to use, and can be adapted to a variety of testing configurations.
This paper discusses the status of the RCS Measurement Standard, IEEE Standards Project P1502. This standard (actually a “recommended practice”) is sponsored by the Antenna Standards Committee of the IEEE Antennas and Propagation Society (Mike Francis, 2004 Chair). The title is “Recommended Practice for Radar Cross Section Test Procedures”. The standard is being generated by the Radar Cross Section Subcommittee of the IEEE AP-S Antenna Standards Society (Dr. Eric Walton, 2004 Chair). The RCS Measurement Practice Standard is being written for the personnel responsible for the operation of a test range, and not for the design of such a range. The purpose of this presentation is to give the community an update on our progress. The briefing will also review the contents and direction the document is heading. We solicit input from members of the community with a goal of getting the document released for general review within the IEEE and publication within the next year.
As antennas become more complex, their test requirements are also becoming more complex, requiring more data to fully evaluate the performance of today’s modern antennas. At the same time, competition and time-to-market concerns are driving the need to reduce the cost of test for most antenna test facilities. This places stringent demands on our test facilities, personnel, and resources. To be competitive, new and creative ways are needed to meet these new demands. Fortunately, technology is changing, and these advances in technology if properly applied, can provide a way to reduce total test times and increase the productivity of test ranges. This paper will look at this new technology and examine how it can be applied to antenna measurements to significantly reduce measurement times. This paper will describe new technology features applicable to antenna/RCS measurements, configuration diagrams, typical antenna/RCS measurement scenarios, and measurement time comparisons for the different measurement scenarios. This will allow antenna test professionals to determine the measurement time reductions and productivity gains that can be achieved for their specific measurement ranges and test scenarios.
Field level RCS measurements are difficult to perform in rugged, unimproved environments, even under the best of conditions. Recently, NASA tasked AFRL to measure the scattering characteristics of a Solid Rocket Booster (SRB) Booster Separation Motor (BSM) Plume at China Lake's "Skytop" Measurement Facility, as part of characterizations needed to return the Shuttle to safe flight. AFRL's Mobile Diagnostic Laboratory (MDL) was used to measure the RCS of six sequential BSM plume firings, a major technical challenge since each burn lasts only 0.8 seconds. The residual smoke plume RCS was also measured during the post firing period. The experimental set up and scattering results are described.
We present a first-order analysis of the RCS errors resulting from non-uniform ground-bounce illumination in mobile, ground-to-ground, diagnostic RCS measurements of aircraft. For the case of a non-planar ground surface, these errors are a function of both aspect angle and position on the target. We quantify the errors in terms of their impact on the sector mean RCS as a function of position on the target. For typical targets, we show that the mean RCS error increases significantly for points displaced (either horizontally or vertically) from the calibration point. Conversely, the sector mean RCS is relatively insensitive to small-scale variations in the height of the ground, even though the errors at a single frequency and aspect angle can be quite large.
The National RCS Test Facility (NRTF) has measured radar cross section (RCS) of fixed wing aircraft for many years. In order to expand our testing options at the NRTF Mainsite test facility, the NRTF has developed a rotorcraft measurement capability. The design is compatible for use with our 50-foot pylon, but unlike existing rotators, allows for RCS measurement of test articles that require significant forward and aft target pitches. Target mounting and positioning was not the only challenge. Our new capability required the control and collection of rotor blade position information, in addition to the control and collection of traditional target azimuth and elevation data. Modification of our existing acquisition software and command and control systems was also required. In order to maintain the integrity of the NRTF’s calibration processes and enable the use of existing calibration devices, hardware was constructed to enable mounting of these devices to the spindle system. Other important considerations that influenced the design and implementation of the spindle mount capability include cost effective mounting/dismounting of test articles (to include the targets and calibration devices) safety of the test articles and personnel, and the effective determination of backgrounds.