Diagnostics of the SMOS radiometer antenna system at the DTU-ESA spherical near-field antenna test facility

2007 ◽  
Author(s):  
C. Cappellin ◽  
A. Frandsen ◽  
S. Pivnenko ◽  
G. Lemanczyk ◽  
O. Breinbjerg
Keyword(s):  
Near Field ◽  
Antenna System ◽  
Test Facility

Simultaneous Noise and Performance Measurements for High-Speed Jet Noise Reduction Technologies

2009 ◽  
Author(s):  
Dean Long ◽  
Steven Martens
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Near Field ◽  
Jet Noise ◽  
Source Distribution ◽  
Test Facility ◽  
Wave Radiation ◽  
Far Field ◽  
Shock Cell ◽  
Field Noise

Model scale tests are conducted to assess the Noise/Performance trade for high speed jet noise reduction technologies. It is demonstrated that measuring the near field acoustic signature with a microphone array can be used to assess the far field noise using a procedure known as acoustic holography. The near field noise measurement is mathematically propagated producing an estimate of the noise level at the new location. Outward propagation produces an estimate of the far field noise. Propagation toward the jet axis produces the source distribution. Tests are conducted on convergent/divergent nozzles with three different area ratios, and several different chevron geometries. Noise is characterized by two independent processes: Shock cell noise radiating in the forward quadrant is produced when the nozzle is operated at non-ideally expanded conditions. Mach wave radiation propagates into the aft quadrant when the exhaust temperature is elevated. These results show good agreement with actual far field measurements from tests in the GE Cell 41 Acoustic Test Facility. Simultaneous performance measurement shows the change in thrust coefficient for different test conditions and configurations. Chevrons attached to the nozzle exit can reduce the noise by several dB at the expense of a minimal thrust loss.

Characterizing a GPR antenna system by near-field electric field measurements

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. A51-A55 ◽  
Author(s):  
Rita Streich ◽  
Jan van der Kruk
Keyword(s):  
Electric Field ◽  
Field Data ◽  
Near Field ◽  
Field Measurements ◽  
Input Voltage ◽  
Antenna System ◽  
Inversion Method ◽  
Migration Imaging ◽  
Imaging Algorithms ◽  
Electric Field Measurements

A method to determine current distributions on resistively loaded Wu-King-type antennas from sparse near-field measurements of the electric field is introduced. We use a parametric formulation of current flow and invert the measured data to determine the characteristic antenna parameters and input voltage wavelets that best explain the measured electric-field data. We compare modeled and measured electric-field data to show that our inversion method yields reasonable results and that our antenna model provides a means to correct for the effects of an antenna’s finite length in migration/imaging algorithms. By modifying the description of the current distribution, our method may be adapted for various antenna types.

scholarly journals DEVELOPMENT OF CONCEPT OF HARDWARE-SOFTWARE COMPLEX OF MODULAR DESIGN FOR DETERMINATION OF ANTENNA SYSTEMS׳ CHARACTERISTICS BASED ON MEASUREMENTS IN THE NEAR FIELD

2017 ◽  
Vol 8 (2) ◽  
pp. 151-159 ◽  
Author(s):  
A. G. Buday ◽  
A. P. Grinchuk ◽  
A. V. Gromyko
Keyword(s):  
Radiation Field ◽  
Modular Design ◽  
Phase Distribution ◽  
Near Field ◽  
Antenna System ◽  
Directional Diagram ◽  
Spherical Coordinate ◽  
Software Complex ◽  
Wide Range ◽  
Antenna Systems

Measuring the amplitude-phase distribution of the radiation field of complex antenna systems on a certain surface close to the radiating aperture allows solving the problem of reconstructing the free-space diagram in the far field and also helps in determining the influence of various structural elements and defects of radiating surfaces on formation of directional diagram. The purpose of this work was to develop a universal hardware-software complex of a modular design aimed for determining the characteristics of wide range of antenna systems in respect of measurements of the amplitude-phase distribution of the radiation field in the near zone.The equations that connect the structure of radiation fields of the antenna system at various distances from it in planar, cylindrical and spherical coordinate systems as well as structural diagrams of the hardware part of measuring complexes have been analyzed.As a result, the concept of constructing a universal hardware-software complex for measuring the radiation field of various types of antenna systems with any type of measurement surface for solving a wide range of applied problems has been developed. A modular structure of hardware and software has been proposed; it allows reconfiguring the complex rapidly in order to measure the characteristics of any particular antenna system at all stages of product development and testing, and also makes the complex economically accessible even for small enterprises and organizations.

scholarly journals A Rigorous Method for Synthesis of Offset Shaped Reflector Antennas

2006 ◽  
Vol 2 (1-2) ◽  
pp. 29-49 ◽  
Author(s):  
Vladimir I. Oliker
Keyword(s):  
High Efficiency ◽  
Near Field ◽  
Nonlinear Partial Differential Equations ◽  
Reflector Antenna ◽  
Antenna System ◽  
New Method ◽  
Reflector Antennas ◽  
Strongly Nonlinear ◽  
The Subject ◽  
Over 40 Years

In this paper the problem of synthesis of offset shaped single reflector antenna is considered. This problem has to be solved when a reflector antenna system is required to control the field amplitude and/or phase on the far-field or on the output aperture in the near-field. Achieving high efficiency is a very important objective of the design and shaped reflector antennas are used for that purpose.The equations of the problem are strongly nonlinear partial differential equations which can not be analyzed by standard techniques. Though the problem has been the subject of study by many authors for over 40 years, up until recently, there were no rigorous theoretical results resolving completely the questions of existence and uniqueness. With few exceptions, authors have attacked the problem with heuristic numerical procedures, and, depending on the specific formulation, obtained different results not always in agreement with each other.In this paper a new method for solving the single reflector problem is presented. The new method allows a complete and mathematically rigorous investigation of this problem. Furthermore, the proposed method lends itself to a numerical implementation and we present here several examples.

Sign in / Sign up

Export Citation Format

Share Document