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Two useful approaches that allow noticeable reduction of the overall measurement time both in the far-field measurements and in the spherical near-field technique, while minimally compromising on the measurement accuracy, are presented and discussed.
In this paper, applicability of using a single probe correction file for processing of multi-frequency results from spherical near-field antenna measurements is investigated. The investigation is carried out for typical probes, an open-ended rectangular waveguide and an open-ended chocked circular waveguide, and for aperture-type antennas under test of various electrical sizes with several distances...
In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission of the European Space Agency. The measurement has been performed with the planar near-field technique in which the...
The 3D reconstruction algorithm of DIATOOL is applied to the BTS1940 antenna, recently measured at the DTU-ESA Spherical Near-Field Antenna Test Facility in Denmark. The antenna was measured mounted on the antenna tower through a custom support structure. The purpose of this paper is to investigate the effect of the support structure on the measured field, by reconstructing the currents induced on...
The 3D reconstruction algorithm is applied to the prototype feed array of the BIOMASS synthetic aperture radar, recently measured at the DTU-ESA Spherical Near-Field Antenna Test Facility in Denmark. Careful analysis of the measured feed array data has shown that the test support structure of the array has a dominant influence on the measured feed pattern. The 3D reconstruction is then applied to...
In this paper, a technique for fast and accurate measurement of on-axis gain and on-axis polarization characteristics of antennas, such as Standard Gain Horns, compact range feed horns, and near-field probes, is described. The proposed gain determination procedure is a modification of the far-field substitution technique in which the measurement distance is defined between the phase centres of the...
In this paper, an electrical performance verification methodology for large reflector antennas is proposed. The verification methodology was developed for the BIOMASS P-band (435 MHz) synthetic aperture radar (SAR), but can be applied to other large deployable or fixed reflector antennas for which the verification of the entire antenna or payload is impossible. The two-step methodology is based on...
Different time-saving scanning schemes for measurement of electrically large antennas by spherical near-field technique are considered and analyzed. Significant time reduction is achieved through thinning of the scanning grid, which still allows obtaining accurate results for typical aperture-like antennas such as reflectors and antenna arrays. The considered scanning schemes were tested on experimental...
The paper presents a design of an open-boundary quad-ridged horn to be used as a wideband scalable dual-linearly polarized probe for spherical near-field antenna measurements. With a new higher-order probe correction technique developed at the Technical University of Denmark, the probe will enable high-accuracy wideband antenna measurements at the DTU-ESA Spherical Near-Field Antenna Test Facility...
The field of antenna measurements is lacking a Golden Standard, i.e. an antenna of which the pattern is known by definition. To gain confidence in the performance of a range, including the procedures and skills of the operators, range comparison has been a popular tool for over three decades. In the beginning, ad-hoc available antennas were shipped around the various ranges. Soon it became clear that...
A new and effective method for reduction of truncation errors in partial spherical near-field (SNF) measurements is proposed. The method is useful when measuring electrically large antennas, where the measurement time with the classical SNF technique is prohibitively long and an acquisition over the whole spherical surface is not practical. Therefore, to reduce the data acquisition time, partial sphere...
The DTU-ESA facility has since the 1980es provided highly accurate antenna radiation pattern measurements and gain calibration by use of the probe corrected spherical nearfield technique, both for ESA (the European Space Agency) and other customers and continues to do so. Recent years activities and research carried out at the facility are presented in the article. Since 2004 several antenna test...
In this paper, a novel near-field cable-free impedance and gain measurement technique for electrically small antennas is proposed. In this technique, with the electrically small antenna placed in the near-field region of the probe, the properties of this antenna are extracted by measuring the signal scattered by it when it is loaded in turn with three known loads. The determination of the antenna...
In this paper, the relatively recently introduced double phi-step theta-scanning scheme and the probe correction technique associated with it is examined against the traditional phi-scanning scheme and the first-order probe correction. The important result of this paper is that the double phi-step theta-scanning scheme is shown to be clearly less sensitive to the probe misalignment errors compared...
In this paper, a simple and efficient electrical alignment procedure known as flip-test is adapted and applied to check and correct two errors in the mechanical setup of a planar near-field system: the mis-pointing of the z-axis of the antenna coordinate system with respect to the scan plane and the displacement of the center point of the scan plane with respect to the z-axis of the antenna coordinate...
Characteristics of electrically small loop antennas were measured by different techniques and the results were compared in-between. The techniques employed were: a single-probe spherical near-field technique, a multi-probe spherical near-field technique, a reverberation chamber, and a Wheeler cap technique. The results were compared with regard to the measurement accuracy, measurement speed, and applicability...
In wireless communication systems, multipath interference has a significant impact on system design and performance. Fast fading is caused by the coherent summation of one or more echoes from many reflection points reaching the receive antenna. Antenna diversity can be used to mitigate multipath fading. The main challenge of antenna diversity in practical application is the integration of multiple...
Measurement of radiation efficiency for ultra small antennas represents a great challenge due to influence of the feeding cable. The Wheeler cap method is often used to measure the radiation efficiency of small antennas. However, it is well applicable for antennas on a ground plane, but not for balanced antennas like loops or dipoles. In this paper, a modified Wheeler cap method is proposed for the...
A computationally efficient probe-corrected electromagnetic theory is presented for computing the field of an arbitrary source of finite extent (test antenna) from measurements with a known symmetric probe on a surrounding spherical surface. The new theory, which can deal with higher-order probes, has exactly the same computational complexity as the standard theory, which can deal only with first-order...
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