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In order to reduce the cost of building compact range reflectors, a combination of a circular rim reflector and R-card fence can be used. Circular rim reflectors are commercially available at reasonable prices. The R-card sheets are also inexpensive. Since the R-card works as a fence to block/reduce the reflector edge diffraction from degrading the plane wave in the test zone, the manufacturing cost is very low. However, the design is much more difficult since the convex nature of the circular reflector rim diffracts more stray signal into the test zone. Thus, the R-card fence should be carefully designed all around the reflector rim. The optimum continuous resistance distribution is replaced by a discretized one to result in lower cost. The R-card design, that reduces the variations in the test zone for a reflector with a circular rim, will be presented in this paper. Calculated and measured results will be shown for the proposed design.
This paper is focused on a recent installation of a probe array for direct far-field. measurement. Such an array has been installed in a well-established compact antenna test range at CNES called BCMA in Toulouse, France. It describes the interests of using such multi-sensor approach for characterizing directive antennas within far-field conditions without any mechanical movements. The paper shows how this facility has been dimensioned for operating over frequencies ranging from 7 GHz up to 15 GHz. Performances and general descriptions of both the probe array and its associated instrumentation will be given. A specific calibration procedure that has been studied and implemented is discussed and finally preliminary results are shown.
Modern Satellite Antennas and Payloads are characterized by a lot of physical parameters like e.g. Radiation Pattern, Gain, EIRP, Flux Density, Gff and PIM, whereas the available time frame for measurements is getting shorter and shorter. The DSS Compensated Compact Range (CCR) allows a time efficient measurement of all payload parameters with high accuracy under controlled environmental conditions. The CCR consists of two doubly curved reflectors, which prevent inherent cross-polarization and create a very high constant amplitude and phase distribution in the quiet zone with a very good scanning performance. Most of the payload parameters can be measured directly or have to be calculated from a set of measurement values. For the G/T measurement of active antennas a new method for the noise power measurement was established. This paper describes the principle test set-ups with the corresponding measurement techniques to improve the measurement accuracy. Error budgets will be presented for pattern and gain measurement.
A compact range based measurement system for automotive radars is presented. The design driver for the system was production testing. Key characteristics of the system are: compact size, short test times, no need for an anechoic chamber, ease of operation, mobility and ruggedness. The measurement system is based on electronic equipment from Dornier GmbH, the company who developed the automotive radar for the new Mercedes S-Class. It uses a small rolled edge millimeter wave compact range from ORBIT/FR Europe GmbH. Some general characteristics of automotive radars are presented, followed by a more detailed description of the key subsystems of the measurement system: Simulator, Compact Range and Processing Control Unit. Finally some measurement results are presented and discussed.
Uncertainty analysis for fundamental standards is mature, but the cost overhead has, until recently, prevented much of this work being taken up by the UK RCS measurement community. The requirement to verify the radar signature of new equipment has made it necessary to examine in detail the RCS measurement process and to create a methodology for error budgeting. The paper reviews some basic concepts in estimating uncertainties, and describes work on 'squat' cylinder calibration standards that have been manufactured following designs proposed at previous AMTA conferences. The moment method code CLASP has provided the basic theoretical solutions which have been verified on a compact range through reference to a precise 100mm spherical standard. The concept of multiple standard calibrations is discussed, and recommendations are made for overall error budgeting and the intercomparison of range types.
A nonparametric, two-dimensional spectral estimation algorithm, based on adaptive decomposition using the reweighted minimum norm method, is applied to ISAR imaging. This paper will describe the algorithm and demonstrate its performance using numerical simulations and compact range measurements. It will be shown that the technique can provide robust isolation and extraction of target and/or contamination returns in situations where these returns would not be resolvable using conventional Fourier imaging techniques.
Time domain (TD) antenna measurements have been successfully implemented in far field ranges [1,2]. The short acquisition times and the wide-band nature of the measurements make this regime a potential alternative to classical frequency domain measurements. Due to the measurement versatility offered by compact ranges, the implementation of TD measurements becomes especially attractive. This paper presents the modelling of the compact range performance in TD. In addition, a statistical evaluation criterion to assess the quiet zone quality is formulated. The results obtained show that this type of measurements can be successfully implemented in compact ranges.
Compact antenna test ranges intended for low cross polarization antenna measurements require the use of feeds with polarization ratios typically greater than 40 dB across the included angle of the quiet zone as well as across the frequency band of interest. The design for a series of circular corrugated aperture feeds to meet these requirements is presented. The feeds are based on a circular waveguide OMT covering a full waveguide frequency band with interchangeable corrugated apertures to cover three sub-bands. In order to validate the design of this series of scalar feeds, high accuracy cross-polarization data was collected. The primary limiting factor in the measurement of the polarization ratio was the finite polarization ratio of the source antennas. A technique for correcting for the polarization ratio of the source is presented along with measured data on the feeds. The technique begins with the accurate characterization of the linear polarization ratio of the standard gain horns using a three antenna technique, followed by pattern measurements of the feeds, and ends with the removal of the polarization error due to the source antenna from the measured data. Measured data on these feeds is presented before and after data correction along with data predicted using the CHAMP® moment method software.
MI Technologies has developed a technique to achieve very high accuracy cross-polarization measurements using a single reflector compact range. The technique, known as the "Error Correction Code Algorithm" (ECCA) leverages the "ideal" performance of a single parabolic reflector when the feed axis is aligned to the parabola axis. ECCA mathematically corrects for the amplitude taper induced by the feed axis alignment. Historically, 'conventional' compact range polarization purity has been limited to »-30 dBi. The ECCA technique, however, lowers the cross-polarization error to »-48 dBi. This performance has been verified in two separate inter-range measurement comparisons with the National Institute of Standards and Technology. The results of these tests prove ECCA is an extremely accurate technique for low cross polarization measurements and provides a lower cost, superior performance alternative to dual reflector systems when low cross-polarization measurements are required.
The DSS/DASA Compensated Compact Range CCR75/60 is a very accurate measurement facility to measure the RF antenna performance. A special feature of this compact range is the creation of scanned quiet zones with defocused feeds, which allow accurate antenna measurements with tilted plane waves. Even there is a straight forward and accurate method to determine the tilting angle or boresight. The boresight of the facility can be derived from the geometrical configuration using optical references. The agreement between geometrically and RF determined boresight is shown in this paper. The geometrical boresight has been measured optically using only geometrical references. The tilting angle for the scanned quiet zones has been predicted by the antenna design program GRASP. The RF boresight has been determined by plane wave probing.
Modelling of the field in the quiet zone (QZ) of a compact range is a difficult task since the edges of the range reflectors are designed not to radiate into the quiet zone. As a consequence the edges of the range reflectors are complicated to model electromagnetically. In the present paper we compare modelling by physical optics (PO) with modelling by the uniform geometrical theory of diffraction (GTD). The investigation is carried out on a double reflector range with rectangular serrated reflectors. It is found that the range far field determined by PO is best explained by a ray model for reflectors having a double straight edge, which suggests to apply a GTD model on reflectors with straight edges but with attenuated diffraction contribution. Both PO and GTD results are shown and compared to measurements.
Compact Antenna Test Ranges are eminently suitable for obtaining the far-field patterns of various types of antennas provided that the frequency is not too low. Typically, a low frequency limit of 1 or 2 GHz is realizable. There are, however a number of important applications between 500 and 1000 MHz for antenna diameters between 1 and 3 meters. The far field distance R = 2D2/l is just too large for an indoor far field range. It is generally accepted at present that a good solution for an indoor range for these kind of measurements is very difficult to realize. In this paper the low frequency performance of single and dual-reflector Compact Antenna Test Ranges will be investigated. It will be shown that with carefully designed serrations and feeds, excellent antenna measurements can be carried out at frequencies below 1.0 GHz for a large number of applications. For purposes of comparison, low frequency performance of a compact range with so called blended rolled edges will be presented as well.
The theoretical study of scattering by various objects inside a circular hollow dielectric waveguide (HDW) is important to analyze the overall accuracy of the method in which this guiding structure plays a role of the main component of a micro-compact compact range. Here, we propose an theoretical approach to the solution of the problem of electromagnetic scattering from a spherical object inside a circular HDW based on the well-known method of separation of variables and the concept of recursive T-Matrix algorithm. Owing to the approach, we studied electromagnetic properties of a spherical scatterer inside a circular HDW as well as obtained basis to develop an approach for calculations of scattering by objects of other shapes. The results calculated for metallic spherical scatterers inside circular HDW were compared with corresponding measurements data of backward and forward scattering characteristics at 4-mm wave band.
Compact range collimating reflectors provide far-field conditions for radar signature measurements. Traditionally, the quiet zone is presented uniformly about the collimator boresight and depends upon both the size of the reflector and the beamwidth of the illuminating antenna, with a maximum determined by the reflector dimensions. Targets are placed in the center of the quiet zone and rotated about the center of gravity (cg) during measurement. Limitations on target size are defined by the quiet zone bounds. For large targets with a non-central cg location, a portion of the target may extend beyond the quiet zone boundary. A technique for synthesizing a larger quiet zone uses displacement of the collimator beam by means of feed point offset to allow far-field measurement of an asymmetrically-mounted extended target. Simultaneous measurements for each offset are then combined to produce the complete measurement. This technique was implemented for measurements of an ARIES ballistic missile target.
A compact cassegrain antenna has been designed for dual-band satellite communications, operating at 20GHz and 30GHz. The antenna consists of a parabolic reflector, a hyperbolic sub-reflector, and a dual-band choke feed. The cassegrain structure has been optimized considering theoretical and measured feed patterns using different software packages, for maximum antenna efficiency with minimum sidelobe levels for a compact design objective. Experimental studies have been carried out in the near-field chamber of the University of Manitoba. The knowledgenof the near-field is helpful in order to adjust different components of the cassegrain antenna. After adjustment, results in terms of gain and radiation patterns are computed by Fourier transform using near-field data, and compared to the measurements realized in the compact range of the University of Manitoba. Comparisons are also made with the results obtained by simulation.
Over the last ten years, MRC has designed, fabricated, and installed a number of compact range reflector systems. This paper presents such reflector programs illustrating a variety of alternatives for reflector composition. Such programs include the MRC Scattering Measurements Lab (SML), the Air Force Research Lab's Advanced RCS Measurements Range (ARMR), Honeywell's Antenna Measurements Range, the new GE/NT Compact Range, and the new TRW Compact Antenna Test Range. Variations within these programs include single or dual-reflector configurations, single piece to panelized designs, and all composite to all aluminum construction. All approaches present excellent alternatives for various compact range needs.
A fully-polarimetric compact range operating at 524 GHz has been developed for obtaining Ka-band RCS measurements on 1:16th scale model targets. The transceiver consists of a fast switching, stepped, C W , X-band synthesizer driving dual X 4 8 transmitmultiplier chains and dual X 4 8 local oscillator multiplier chains. Software range-gating is used to reject unwanted spurious responses in the compact range. A motorized target positioning system allows for fully automated sequencing of calibration and target measurements over a desired set of target aspect and depression angles. A flat disk and a dihedral at two seam orientations are used for both polarization and R C S calibration. Cross-polarization rejection ratios of better than 45 d B are routinely achieved. The compact range reflector consists of a 1.5m diameter aluminum reflector fed from the side to produce a 0. 5 m diameter quiet zone. Targets are measured in free-space or on a variety of ground planes designed to model most typical grou nd surfaces. A description of this 524 GHz compact range along with 30 ISA R measurement examples are presented in this paper.
The development and measured performance of a hologram type compact antenna test range (CATR) for submillimetre wavelengths are presented. A 60 cm diameter hologram has been designed for the 310 GHz CATR. The instrumentation used for the compact range performance verification is described. This includes a millimetrewave vector network analyzer with alternative source oscillator configurations. Finally, future improvements to the hologram CATR such as a dual-reflector feed system are discussed.
The collection of radar scattering data necessary for imaging targets with three-dimensional resolution requires frequency diversity, combined with angular diversity over two orthogonal axes fixed to the target. Although the necessary data can easily be collected using modern instrumentation systems when the target is outfitted with an embedded two-axis rotator, some applications preclude the intrusion of the rotator. This paper describes an alternative method for obtaining the required data which uses conventional target rotation in the azimuth plane, combined with a linear displacement of the compact range feed along the vertical axis of the collimator's focal plane. Frequency diversity is provided by a stepped-frequency radar and angular diversities in the horizontal and vertical directions are provided by the target rotation and vertical feed displacement, respectively. The data-collection scheme samples a wedge-shaped volume of the target spatial spectrum (k-space) with radial and angular extents de terminated by the bandwidth and target rotation relative to the radar axis. A three-dimensional image is formed by processing a three-dimensional array of data, typically consisting of 128xll8x128 data samples. The paper describes the experimental set-up used to collect Ku-band data and presents two- and three dimensional images obtained from the data. Considerations of the following issues are addressed in the paper. 1. Aberrations resulting from displacing the feed from the collimator focal point. 2. Control of the linear feed displacement, target rotation, and radar operation to automate the data collection. 3. Methods for calibrating and aligning the data. 4. Signal processing methods which combine wideband, ISAR and spotlight SAR processing for three-dimensional applications. 5. Clutter suppression using zero-Doppler filtering.
This paper is concerned with the measurement and analysis of a circularly polarized, flat plate patch array receiving antenna at 12.5 GHz. Input impedance and far field pattern measurements of the antenna over the frequency band from 10 to 15 GHz were performed. The small Compact Range (CR) facility of the Ohio State University Electro Science Laboratory OSU/ESL was used to measure the gain pattern. Gain pattern measurement of the antenna was done by using the gain comparison method. A broadband (2-18 GHz), constant phase pyramidal horn antenna was used as a reference. The data were analyzed to determine the radiation efficiency of the antenna.