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The KRISS is in the process of completing the construction and installation of a planar near-field antenna test facility in the frequency range of 2 GHz to 50 GHz. This paper describes the planar near-field antenna test facility. Comparison of the far-field pattern, for verifying the antenna test facility, using a parabola antenna as artifact is also described. The patterns were measured by using the installed antenna test facility and a method developed by our group and showed good agreement.
In this paper two planar near-field scan plane reduction techniques are considered and results are presented. It is shown how truncation based on field intensity contours, instead of simple geometric truncation can in some cases improve the efficiency of the truncation process. Both techniques are applied to measured data sets and it is shown how these methods can be used to reduce data acquisition times while also assessing the impact of the total acquisition surface reduction on the far-field radiation pattern integrity.
This paper presents the results of a laboratory simulation of an outdoor telematic antenna test site that employs spherical near-field scanning to determine the far fields of telematic antennas mounted on vehicles.
This paper describes a Composite Near-Field Scanning Antenna Range for frequency bands that extend from X- Band in the microwave frequency regime through W- Band in the millimeter-wave regime – i.e. 8.2 through 110 GHz. We show some of the initial checkout data using pyramidal standard gain horns and compare the patterns to theory.
It is well known that a microstrip transmission line can radiate if it is excited in its first higher order mode (with the fundamental or dominant mode suppressed). A new microstrip configuration is proposed that supports the first higher order mode while suppressing the fundamental mode. To quantify the leakage constants in the two cases for comparison purposes, several experimental means are considered to determine the source amplitude distribution from which the leakage constants may be deduced. First, an approximation to the source distribution is determined from the far field patterns themselves. Second, the source distribution is determined by carefully probing the near field. This paper uses these techniques to verify the performance of a new leaky wave antenna design.
In this paper, we present an analysis of the impact of positioning errors on the performance of the GDAIS circular image-based near field-to-far field RCS transformation (CNFFFT). The analysis is part of our continuing investigation into the application of near fieldto-far field transformations to ground-based signature diagnostics. In particular, the analysis focuses on the errors associated with ground-to-ground, near-field, whole-body measurements where the radar moves on a nominally circular path around the target. Two types of positioning errors are considered: slowly-varying, long term drift and rapidly-varying, random perturbations about the nominal circular path. The analyses are conducted using simulated data from a target comprised of an array of generalized point scatterers which model both single and multiple interactions on the target. The performance of the CNFFFT was evaluated in terms of the angle sector cumulative RCS statistics. The analyses were performed as a function of frequency for varying amounts of position error, both with and without (approximate) motion compensation. As expected, the results show that the CNFFFT is significantly more sensitive to rapidly-varying position errors, but that acceptable performance can be achieved with motion compensation provided an accurate estimate of the errors is available.
In this paper, we present an analysis of the impact of positioning errors on the performance of the GDAIS circular image-based near field-to-far field RCS transformation (CNFFFT). The analysis is part of our continuing investigation into the application of near fieldto-far field transformations to ground-based signature diagnostics. In particular, the analysis focuses on the errors associated with ground-to-ground, near-field, whole-body measurements where the radar moves on a nominally circular path around the target. Two types of positioning errors are considered: slowly-varying, long term drift and rapidly-varying, random perturbations about the nominal circular path. The analyses are conducted using simulated data from a target comprised of an array of generalized point scatterers which model both single and multiple interactions on the target. The performance of the CNFFFT was evaluated in terms of the angle sector cumulative RCS statistics. The analyses were performed as a function of frequency for varying amounts of position error, both with and without (approximate) motion compensation. As expected, the results show that the CNFFFT is significantly more sensitive to rapidly-varying position errors, but that acceptable performance can be achieved with motion compensation provided an accurate estimate of the errors is available.
This paper presents a Radar Crossed Section (RCS) time-domain near-field measurement and its Inverse Synthetic Aperture Radar (ISAR) imaging. The target includes a pyramidal horn and a metallic aircraft scale model. A pulse generator excites the transmit antenna and a digital sampling unit collects the data at the receiving side. A time gating window is subsequently applied to reject the multiple reflections. An efficient 3-D algorithm for ISAR based on time-domain near-field data is presented. The test results for six cases demonstrate excellent ISAR images. In particular the geometry of 3-D reconstructed target can be displayed in perspective manner. The advantage of using time-domain near-field measurements is three-fold. First, it reduces measurement time in the order of one-tenth compared to frequency-domain measurements. Second, it mitigates the multiple reflection effects via time gating. Third, near-field measurements require relatively little real estate which reduces the cost tremendously since a compact range is not needed.
This paper presents a Radar Crossed Section (RCS) time-domain near-field measurement and its Inverse Synthetic Aperture Radar (ISAR) imaging. The target includes a pyramidal horn and a metallic aircraft scale model. A pulse generator excites the transmit antenna and a digital sampling unit collects the data at the receiving side. A time gating window is subsequently applied to reject the multiple reflections. An efficient 3-D algorithm for ISAR based on time-domain near-field data is presented. The test results for six cases demonstrate excellent ISAR images. In particular the geometry of 3-D reconstructed target can be displayed in perspective manner. The advantage of using time-domain near-field measurements is three-fold. First, it reduces measurement time in the order of one-tenth compared to frequency-domain measurements. Second, it mitigates the multiple reflection effects via time gating. Third, near-field measurements require relatively little real estate which reduces the cost tremendously since a compact range is not needed.
In this paper the electrical displacement of phased array elements along the axis of a linear array, and in the direction normal to the array are examined. A closed-form solution is presented for determining the location of phased array elements from the first and second derivatives of the phase measured on a near-field antenna range. The technique is applied to swept CW measurement patterns of a 20-element, S-band array of open-ended waveguides. It is shown that the electrical location of edge elements differs significantly from the physical location in both x-dimension and z-dimension. The effects of wide array bandwidth on the phase center displacement are illustrated.
For enhancing the performance of existing near field antenna test facilities it is quite reasonable to use both conventional (the amplitude and phase measurements) and the phaseless measurements techniques during electrically scanning phased array antennas (PAA) testing. This simple yet critical approach helps to improve the quality of PAA alignment and testing reducing measurement errors and saving costs. In this way many difficulties related to precise phase measurements are overcome. Both simulation and measurement results will be presented to demonstrate the utility of such approach to PAA alignment and determination of its parameters. Comparison will be made between the PAA patterns for electrically scanned beams calculated using traditional near field - far field (NF/FF) transformations, the phaseless methods and the results obtained applying both measurement techniques.
This paper discusses the use of a laser-tracking device to provide position information in x, y, and z that can be used in position correction algorithms to correct for any displacement error in the actual measurement. Planar near-field measurements require taking amplitude and phase information at accurate and equal point spacing on a plane in front of the antenna under test. The required position accuracy on this plane has been determined to be approximately ./50. As frequencies increase higher, the accuracy in point spacing position on the planar grid becomes more difficult to achieve.
This paper presents a novel variable width time gating technique, which is applied to planar and cylindrical near-field data in impulse time-domain antenna near-field measurements. Due to the changing distance between the probe and the antenna under test (AUT) in planar and cylindrical scans, the conventional fixed time gating technique causes problems to remove multiple reflections from the desired AUT response. It further limits the application of time-domain measurement to planar and cylindrical scans. The new variable width time gating technique provides a flexible way to solve these problems. Test results for both planar and cylindrical near-field measurements are presented. The difference of far-field patterns between time-domain and frequency-domain near-field measurements is noticeable. We also show the effects on the far field patterns due to fixed and variable time gating windows. We further conclude that the time-domain technique also works for planar and cylindrical near-field measurements by using variable width time gating technique.
This paper presents a novel variable width time gating technique, which is applied to planar and cylindrical near-field data in impulse time-domain antenna near-field measurements. Due to the changing distance between the probe and the antenna under test (AUT) in planar and cylindrical scans, the conventional fixed time gating technique causes problems to remove multiple reflections from the desired AUT response. It further limits the application of time-domain measurement to planar and cylindrical scans. The new variable width time gating technique provides a flexible way to solve these problems. Test results for both planar and cylindrical near-field measurements are presented. The difference of far-field patterns between time-domain and frequency-domain near-field measurements is noticeable. We also show the effects on the far field patterns due to fixed and variable time gating windows. We further conclude that the time-domain technique also works for planar and cylindrical near-field measurements by using variable width time gating technique.
A new method to avoid the truncation error in antennas near-field measurements is presented. The truncation problem is solved by picking up the information that is lost due to the finite size of scanning area, in points of the space reachable by the measurement system. The points are chosen in order to obtain a stable reconstruction of the field falling outside the available scanning area. The method can be applied to any scanning geometry, including the planar and cylindrical ones, whenever the set-up allows to vary the distance between the antenna under test (AUT) and the probe during the scanning procedure. Application of the method to cylindrical near-field scanning is numerically investigated, assessing the effectiveness of the proposed technique.
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.
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.
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.