Sergey Pivnenko

Theory and Practice of the FFT/Matrix Inversion Technique for Probe-Corrected Spherical Near-Field Antenna Measurements With High-Order Probes

A complete antenna pattern characterization procedure for spherical near-field antenna measurements employing a high-order probe and a full probe correction is described. The procedure allows an (almost) arbitrary antenna to be used as a probe. Different measurement steps of the procedure and the associated data processing are described in detail, and comparison to the existing procedure employing a first-order probe is made. The procedure is validated through measurements.

Coupling Reduction Between Dipole Antenna Elements by Using a Planar Meta-Surface

The mutual coupling between dipole antenna array elements using a planar meta-surface as superstrate is experimentally investigated. The meta-surface is based on grids of short metal strips and continuous wires. A comparison between the mutual coupling when the dipoles are radiating in free space and in presence of the superstrate is presented. On average, between 3 to 14 dB reduction of the mutual coupling is achieved when the superstrate is used. The effect of the mutual coupling on the radiation performance of the array is studied by spherical near-field measurements of the radiation pattern when one driven dipole is fed and the others are matched with 50 Omega loads. The back-projected field on the aperture and on the E-plane is shown.

Comparison of Antenna Measurement Facilities With the DTU-ESA 12 GHz Validation Standard Antenna Within the EU Antenna Centre of Excellence

The primary objective of many antenna measurement facilities is to provide a specified high accuracy of the measured data. The validation of an antenna measurement facility is the process of proving that such a specified accuracy can be achieved. Since this constitutes a very challenging task, antenna measurement accuracy has been the subject of much research over many years and a range of useful measures have been introduced. Facility comparisons, together with antenna standards, error budgets, facility accreditations, and measurement procedure standards, constitute an effective measure towards facility validations. This paper documents the results of a comparison between 8 European antenna measurement facilities with a specially designed reference antenna, the DTU-ESA 12 GHz validation standard antenna (VAST-12). The electrical and mechanical properties of the VAST-12 antenna are presented and its three different coordinate systems are defined. The primary objective of the comparison is to obtain experience and results that can serve to develop standards for validation of antenna measurement facilities. The paper focuses on the comparison of the radiation pattern and presents not only the measurement data obtained at the facilities, but also investigates several procedures for comparing these data. This includes various definitions of pattern difference and statistical measures as well as a reference pattern. The comparison took place in 2004-2005 as part of the European Union network of excellence called ACE-Antenna Centre of Excellence.

Superdirective Magnetic Dipole Array as a First-Order Probe for Spherical Near-Field Antenna Measurements

The theory as well as numerical and experimental results are presented for a superdirective array composed of closely spaced electrically small resonant magnetic dipole elements. The array operates on a metal ground plane and can exhibit a maximum directivity of 11.5 dBi, 15.2 dBi, and 17.8 dBi (including 3 dB due to the ground plane), for 2, 3, and 4 magnetic dipoles, respectively. The array is self-resonant and is directly excited by a 50-ohm coaxial cable through the ground plane. The array radiates essentially the |μ| = 1 spherical modes, which, despite a narrow bandwidth, makes it an excellent first-order probe for spherical near-field antenna measurements at low frequencies.

Iterative probe correction technique for spherical near-field antenna measurements

An iterative probe correction technique is presented to correct for the errors caused by the application of the traditional first-order probe correction for nonideal first-order probes in spherical near-field antenna measurements. The technique may be applied, with certain restrictions, for more general probes as well.

Application of the iterative probe correction technique for a high-order probe in spherical near-field antenna measurements

An iterative probe-correction technique for spherical near-field antenna measurements is examined. This technique has previously been shown to be well-suited for non-ideal first-order probes. In this paper, its performance in the case of a high-order probe (a dual-ridged horn) is examined

Antenna measurement facility comparison within the European Antenna Centre of Excellence

This paper gives an overview of the ongoing activities under the antenna measurement techniques and facility sharing activity of the Antenna Centre of Excellence (ACE) within the EU 6th framework research program. In particular, the activities involving antenna measurement facility comparisons are discussed in detail. These activities are important instruments to verify the measurements accuracies for each range and investigate and evaluate possible improvements in measurement set-up and procedures. Facility comparisons involving high accuracy reference antennas are key instruments for the evaluation, benchmarking and calibration of antenna measurements systems. Regular inter comparisons between accredited measurement facilities are also an important instrument for the measurement traceability and quality maintenance.

Comparative analysis of approximate and exact solutions of transient wave radiation problems

The problem of transient wave radiation from open end of a coaxial waveguide is solved by means of the modal basis method in time domain. The analytical expressions of fields radiated into free space and reflected inside the waveguide are obtained for step-wise time dependence of amplitude of the exciting TEM-wave. The solution for exciting TEM-wave with arbitrary time dependence of amplitude is obtained by calculation of Duhamels integral. The exact solution of the problem is compared with the same one obtained in Kirchhoff approximation. The spatial and time dependencies of the field radiated from the coaxial aperture are obtained experimentally to examine theoretical results. A comparative analysis of the theoretical and experimental results is made.

Phase radiation characteristics of an open-ended circular waveguide

Analytic expressions for phase radiation characteristics of a semi-infinite open-ended circular waveguide regardless of its aperture size and operating frequency have been obtained by making use of the rigorous Weinstein theory. The analysis of phase radiation patterns has been carried out for the dominant mode (TE/sub 11/) as well as for the high order modes TM/sub 01/ and TE/sub 01/, both for single and multimode propagation. The measurement of radiation characteristics of an open-ended circular waveguide has been carried out at the DTU-ESA Spherical Near-Field Antenna Test Facility. Theoretical results are in good agreement with the experimental ones.

Recent advances in antenna measurement techniques at the DTU-ESA spherical near-field antenna test facility

This paper reports recent antenna measurement projects and research at the DTU-ESA Spherical Near-Field Antenna Test Facility at the Technical University of Denmark. High-accuracy measurement projects for the SMOS, SENTINEL-1, and BIOMASS missions of the European Space Agency were driven by uncertainty requirements of a few hundredths of dB for the directivity and correspondingly strong requirements for gain and/or phase. Research and development of 1:3 bandwidth range probes, and the near-field to far-field transformation algorithm accounting for the higher-order azimuthal modes in the spherical wave expansion of such probes, are also reported. Also, a metamaterial-inspired super-directive first-order probe enabling small-sized probes at low frequencies, such as P-band, is reviewed.