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This paper describes a novel planar near-field measurement system designed to test a beam-steered flat face phased array antenna. This system is unique in its ability to measure multiple beams during a single scan of the aperture. The system utilizes a very fast planar scanner with six foot by six foot of travel combined with fast beam-steering commands to significantly reduce the test time of multiple-beam phased array antennas. These features combined with software based on algorithms developed by the National Institute of Standards and Technology provide state of the art measurements of planar phased array antennas.
A dual-linearly polarized probe developed for use in planar near-field antenna measurements is described. This probe is based upon Scientific-Atlanta's Series 31 Orthomode Feeds originally developed for spherical near-field testing. The unique features of this probe include dual orthogonal linear ports, high polarization purity, excellent port-to-port isolation, an integrated coordinate system reference, APC-7 connectors, and a thin-wall horn aperture to minimize probe AUT interactions. The probe was calibrated at the National Institute of Standards and Technology (NIST) and the calibration data consisting of the probe's complete plane-wave spectrum receiving characteristic s'02(K) were imported directly into the Scientific-Atlanta Model 2095/PNF Microwave Measurement System. This paper describes the dual-ported probe and its application in a planar near-field range.
A series of measurements to validate the performance of a Planar Near-Field (PNF) Antenna Test Range located at the Satellite and Aerospace Systems Division at Spar Aerospace Limited were made by Scientific-Atlanta during the month of February 1992. These measurements were made as a part of a contract to provide Spar with a Model 2095 Microwave Measurement System with planar near-field software options and related instrumentation and hardware. The range validation consisted of a series of self-tests and far-field pattern comparison tests using a planar array antenna provided by Spar that had been independently calibrated at another range facility. This paper describes the range validation tests and presents some of the results. Comparisons of far-field patterns measured on the validation antenna at both the Spar PNF facility and another antenna range are presented.
A novel planar near-field antenna measurement and diagnostic system is described. This bi-polar near-field system offers a large scan plane size with reduced "real estate" requirements and a simple mechanical implementation resulting in a highly cost effective antenna measurement system. A brief description of the bi-polar near-field range and its associated data processing methods are given. Measured results are compared with those obtained on a far-field range and a plane rectangular planar near-field range. It is shown that the UCLA facility produces highly accurate results which rival those of modern production antenna measurement facilities. Holographic images produced from measured data are provided to demonstrate the diagnostic capabilities of the antenna range and to provide electromagnetic field visualization for educational purposes.
Rapid data acquisition is crucial in making comprehensive near-field scanning tests of electronically-steered phased array antennas. Multiplexed data sets can now be acquired very rapidly with high speed automatic data acquisition. To obtain high speed without giving up accuracy in probe position a feature termed subinterval triggering has been devised. To obtain simultaneously reliable thermal drift or tie scan data a feature termed block tie scans has been devised. This paper describes these two features that yield speed and accuracy in planar near-field scanning measurements.
Increasing demands on antenna design characteristics have led to corresponding increases in test requirements, particularly in the need for high speed multi-frequency or multi-beam measurements. Special steps are required in the data acquisition process to maintain synchronization of the data to insure accurate results are achieved. This paper will describe techniques used by NSI for a planar near-field measurement system using a Hewlett Packard 8530A with multiple frequencies and multiple beams acquired in the inner loop of the scan pattern.
This paper presents the feasability (sic) to explore the Focal Plane (FP) of a Compact Antenna Test Range (CATR). We first introduce the interest of getting very fast the Far Field Pattern of an antenna with a 2D modulated scattering array located at the focus of a CATR. Then, we discuss the geometric, electrical and optical constraints involved when using this technique. A comparison with a classical measurement performed at ESA-ESTEC is shown and we conclude by emphasizing the potentialities of this technique.
The idea of developing a large compact range with scanned quiet zone has been adopted by several international organizations (ESTEC, MBB, Ford Aerospace, etc.) and is expected to be an useful (sic) measurement tool. The Front-Fed Cassegrain configuration is likely to present good scanning capabilities due to its long equivalent focal length and the small curvature of both reflectors. However, some kind of degradation in the test zone is expected in the form of phase aberrations as a function of the lateral feed displacement and frequency, as well as an increase of the Xpolar level. In this paper, the phase aberration and the Xpolar component introduced by a non-centered Front-Fed Cassegrain configuration is analyzed in a GO-GO basis. It is found that the scanning concept can be applied up to a certain frequency limit in which a gradual reduction of the quiet zone dimensions is observed as the feed displacement (plane wave scanning angle) is increased.
A Planar Near Field to Far Field (PNF/FF) Transformation Program has been developed. This PNF/FF package includes probe correction, spectral filtering, position errors correction and sampled data expansion. In order to evaluate how measurement system errors affect PNF/FF transformation results, a whole set of simulation routines have also been implemented. In this paper, main modules of the PNF/FF package are discussed and error simulation models together with correction routines are described.
The measurements of an antenna at FM frequencies integrated in the bodywork of a terrestrial vehicle is a extremely (sic) delicated (sic) problem that will be larger if a ground plane must be simulated. An algorithm based on two measurements (magnitude and phase of the field components E() and E (1) on a scale model made in an anechoic chamber, has been developed to solve this problem. These measurements correspond to the value of the desired conical cut (only a narrow range of angles above the horizon is significant), and the associated cut needed to measure the specular reflection on the simulated ground plane.
A new near-field far-field transformation procedure, based on only amplitude measurement, is tested from both simulated and measured data. The measurements have been collected at Marconi Research Center and refers to a parabolic reflector working at 9 Ghz. This first experimental validation of the procedure fully support (sic) the feasibility of phaseless near field measurement in the antenna testing.
The paper describes the high frequency measurements of the fields diffracted at the edges of an obstacle. The measurements are performed in an ordinary room, by using the time-domain filtering and frequency smoothing options of a vector network analyzer. The field distribution on a cylindrical arc is measured without the obstacle, and with the metallic obstacle present. The measurement approach in both cases proves to be rather different: without the obstacle, a modified calibration method should be used together with frequency smoothing, while in the presence of the obstacle, the same calibration set needs to be used in conjunction with time domain filtering. In the latter case, however, the use of frequency smoothing is not allowed. The results of the two measurements sessions can be condensed into one parametric curve expressing the additional attenuation of the radio signal, which is caused by the presence of the object on the propagation path. Practical and theoretical curves are compared for several object dimensions, and very good agreement is obtained in all cases.
The anechoic chamber housing the TUD-ESA Spherical Near Field Far Field Antenna Test Facility at the Technical University of Denmark dates back to 1967 while the present RF and data collection and control systems were designed and installed in several stages between 1978 and 1985. This paper undertakes to describe the definition and realization of a refurbished and upgraded radio anechoic facility for antenna measurements given as a starting point the already existing facility. In a parallel effort, both the RF and data collection and control subsystems are being renewed and upgraded.
Some of the novel mechanical and electronic subsystems features on a recently installed high specification planar near-field scanner are described together with a discussion of the problems encountered during the commissioning period. The test facility incorporates a number of novel design concepts both in terms of its instrumentation, control and processing subsystems. Features of the facility are the speed of data acquisition and the accuracy of the acquired near-field data. Scan speeds of up to 0.8 m/s and positional accuracies of 30 microns in the Z-axis have been achieved, and the near-field data is acquired, displayed and measured on the fly, hence allowing a typical 3m x 3m scan to be executed and the measured near-field results to be displayed and processed within a period of thirty minutes.
As many institutions and companies have constructed anechoic chambers in the past few years, there has been little work done to codify the specification requirements. Often chambers have been constructed from woefully inadequate specifications resulting in chambers that may be too costly, unable to meet the performance criteria, and in some cases, be unsafe. This paper shall present various model specifications and guidelines to properly specify a chamber complex. Compact ranges, tapered chambers, as well as traditional rectangular chambers will all be examined. How to specify absorbing materials and quiet zone sizes, as well as tradeoffs associated with them, will be discussed. Finally, a guide for coping with facility concerns such as civil, structural, RF shielding, HVAC, electrical, and fire protection will be presented. Examples of good specifications and inadequate specifications will be demonstrated and reviewed.
The remote capability of the ORBIT AL-8000-5 Microwave Receiver is described. The use of a high speed fiber optic link between the remote receiver and the control room unit allows range distances of up to 19,000 feet. With repeaters, the range distance limitation is removed. This eliminates many of the distance cable and EMI problems associated with receivers which use a remote LO. The small size and weight of the remote unit, allow the system to be mounted on the probe carriage of near-field scanner systems. This eliminates the high frequency phase errors as well as the phase error due to cable bending and temperature variation during the measurement. The result is a lower cost and more accurate measurement system. The advantages of this type of remote system are discussed for both near-field and far-field applications. Measurement data which show the performance of the fiber-optic system are presented. A description and pictures of recent installations are to be provided.
This paper describes the electrical and mechanical design of an outdoor bistatic RCS test range at the National Defence (sic) Research Establishment (FOA) in Linkoping, Sweden. Some experimental bistatic ISAR imaging results will also be discussed. The 100 m RCS test-range uses a curved rail system. The transmitter rail cart can be moved on a constant distance from the target. This can be illuminated in bistatic angles from 0 to 105 degrees. The measurement system uses fiber optic links for transferring reference signals for coherency. The system has an excellent phase stability that enables ISAR imaging and background subtraction techniques to be used.
Implementation of planar near-field (PNF) technology has become more practical in recent years due to the availability of turn-key measurement systems. McClellan AFT (SM-ALC) has developed an automated PNF measurement system by re-configuring a sonar immersion tank positioner. Modifications to the hardware and software have produced an integrated PNF scanner capable of accurate gain and diagnostic measurements. This paper describes the evolution of the SM-ALC near-field measurement system from proof-of-concept diagnostic scanner to a production tool capable of repeatable gain measurements. Analysis of accuracies, limitations, and processing capabilities is provided. Comparative analysis of data for a transfer standard antenna measured on the SM-ALC measurement system and the PNF measurement system at the National Institute of Standards and Technology is also included.
This paper describes the range design and measurement techniques used for acceptance of the TDRSS Flight 7 Single Access Antennas (SAAs) performed at Harris Corporation Government Aerospace Systems Divison. The TDRSS SAA is a dual-band, shaped, cassegrain antenna that utilizes a 4.9 meter deployable reflector made of a wire mesh fabric. Acceptance testing of the SAAs required a high quality test range and a measurement methodology that would account for the gravity effects in a terrestrial environment. The SAA flight feeds were integrated with a solid reflector that precisely emulates the on-orbit surface of the mesh reflector. Antenna measurements were carried out on a far0field range and the mesh loss and mesh reflector surface effects were subsequently factored into the measured data. Multi-path interference, the primary inhibitor to accurate measurements (gating) as well as conventional methods. The range design included automated data acquisition, data processing and control. The test range and measurement techniques described herein resulted in a successful and efficient evaluation of the TDRSS Flight 7 SAA performance.
The target support system at Boeing Defense & Space Group's 9-77 Compact Range includes a new string support system. The string support system consists of twelve string reels, six each of the High Capacity String Reels (HCSR). The string reel system is used to suspend and manipulate a target for radar cross section (RCS) measurements, primarily at frequencies below 1.5 GHz. The string reel system is capable of supporting targets up to 10,000 pounds and 40' in length and width. The manipulation and handling of targets, is a major consideration in a RCS measurement test plan. The following paper discusses the newly installed string reel system, enhancements to the 9-77 Range equipment which directly affect the use of the string support system, and future developments planned for the system.