AMTA Paper Archive


Welcome to the AMTA paper archive. Select a category, publication date or search by author.

(Note: Papers will always be listed by categories.  To see ALL of the papers meeting your search criteria select the "AMTA Paper Archive" category after performing your search.)


Search AMTA Paper Archive
    
    




Sort By:  Date Added   Publication Date   Title   Author

Near Field

MEASURING LOW CROSS POLARIZATION USING A BROAD BAND, LOG PERIODIC PROBE
Allen Newell,Nearfield Systems Inc., November 2012

There are a number of near-field measurement situations where it is desirable to use a broad band probe to avoid the need to change the probe a number of times during a measurement. But most of the broad band probes do not have low cross polarization patterns over their full operating frequency range and this can cause large uncertainties in the AUT results. Calibration of the probe and the use of probe pattern data to perform probe correction can in principle reduce the uncertainties. This paper reports on a series of measurements that have been performed to demonstrate and quantify the cross polarization levels and associated uncertainties that can be measured with typical log periodic (LP) probes. Two different log periodic antennas were calibrated on a spherical near-field range using open ended waveguides (OEWG) as probes. Since the OEWG has an on-axis cross polarization that is typically at least 50 dB below the main component, and efforts were made to reduce measurement errors, the LP calibration should be very accurate. After the calibration, a series of standard gain horns (SGH) that covered the operating band of the LP probe were then installed on the spherical near-field range in the AUT position and measurements were made using both the LP probes and the OEWG in the probe position. The cross polarization results from measurements using the OEWG probes where then used as the standard to evaluate the results using the LP probes. Principal plane patterns, axial ratio and tilt angles across the full frequency range were compared to establish estimates of uncertainties. Examples of these results over frequency ranges from 300 MHz to 12 GHz will be presented.

Estimating the Effect of Higher Order Modes in Spherical Near-Field Probe Correction
Allen Newell,Nearfield Systems Inc, November 2012

The numerical analysis used for efficient processing of spherical near-field data requires that the far-field pattern of the probe can be expressed using only azimuthal modes with indices of µ = ±1. (1) If the probe satisfies this symmetry requirement, near-field data is only required for the two angles of probe rotation about its axis of . = 0 and 90 degrees and numerical integration in . is not required. This reduces both measurement and computation time and so it is desirable to use probes that will satisfy the µ = ±1 criteria. Circularly symmetric probes can be constructed that reduce the higher order modes to very low levels and for probes like open ended rectangular waveguides (OEWG) the effect of the higher order modes can be reduced by using a measurement radius that reduces the subtended angle of the AUT. Some analysis and simulation have been done to estimate the effect of using a probe with the higher order modes (2) – (6) and the following study is another effort to develop guidelines for the properties of the probe and the measurement radius that will reduce the effect of higher order modes to minimal levels. This study is based on the observation that since the higher order probe azimuthal modes are directly related to the probe properties for rotation about its axis, the near-field data that should be most sensitive to these modes is a near-field polarization measurement. This measurement is taken with the probe at a fixed (x,y,z) or (.,f,r) position and the probe is rotated about its axis by the angle .. The amplitude and phase received by the probe is measured as a function of the . rotation angle. A direct measurement using different probes would be desirable, but since the effect of the higher order modes is very small, other measurement errors would likely obscure the desired information. This study uses the plane-wave transmission equation (7) to calculate the received signal for an AUT/probe combination where the probe is at any specified position and orientation in the near-field. The plane wave spectrum for both the AUT and the probe are derived from measured planar or spherical near-field data. The plane wave spectrum for the AUT is the same for all calculations and the receiving spectrum for the probe at each . orientation is determined from the far-field pattern of the probe after it has been rotated by the angle .. The far-field pattern of the probe as derived from spherical near-field measurements can be filtered to include or exclude the higher order spherical modes, and the near-field polarization data can therefore be calculated to show the sensitivity to these higher order modes. This approach focuses on the effect of the higher order spherical modes and completely excludes the effect of measurement errors. The results of these calculations for different AUT/probe/measurement radius combinations will be shown.

Using Spherical Near-field Transforms to Determine the Effects of Range Length on the Measurement of Total Radiated Power
James Huff,The Howland Company, Inc., November 2012

Total radiated power (TRP) and total isotropic sensitivity (TIS) are two metrics most commonly used to characterize the performance of a wireless device. These integrated measurement parameters are not as sensitive to the measurement distance as a single point measurement such as an antenna gain measurement, but it is difficult to accurately quantify the effects of measurement distance on these two parameters. This paper presents a simple approach to quantifying the effects of measurement distance using spherical near-field transforms. Data is taken on a typical wireless device at different range lengths and transformed to the far-field using a spherical near-field transform. The total radiated power is then calculated for both the measured data and the transformed data. The difference in the two calculations shows the effect of a finite range length on the measurement. Measured results are presented for three different range lengths. For each of these range lengths the data is transformed to the far-field and the TRP is calculated.

Challenges and solutions for quasi-planar near-field measurements in reactive zone applied for EMC purpose
Anders Pilgaard Mynster,DELTA - Danish Electronics, Lights and Acoustics, November 2012

In this paper application of quasi-planar near-field measurements to characterize the radiation from a test object with the purpose of electromagnetic compatibility (EMC) will be described. First a brief description of an EMC radiated emission Open Area Test Site (OATS) and the setup of a typical EMC quasi-planar table top near-field scanner will be presented. Then the challenges of adapting the near-field scanning technology used for antennas to near-field scanning of EMC test objects will be discussed. Specifically the challenges of 1) Obtaining phase from active equipment under test (EUT) with a radiation caused by quasi stationary random processes. 2) Challenges in probe design and construction that yields satisfactory sensitivity, cross polarization rejection and field disturbance. 3) Measurement in the reactive near-field region and analysis of the probe impact on the measured data. 4) The problems of characterization of non-planar EUT geometry that violates the equivalent surface theorem due to cables leaving the box enclosed by the surface. 5) Near-field measurements on non-directionally radiating test objects 6) Post processing of EMC near-field data: combining of several measurement data sets and taking multiple reflections into account when inserting measured near-field in a CAD model of the full apparatus. 7) Current status in predicting the absolute radiation level in dBuV/m, as measured in OATS, from a near-field measurement

ADAPTIVE ACQUISITION TECHNIQUES FOR PLANAR NEAR-FIELD ANTENNA MEASUREMENTS – PART 2
Daniel Janse van Rensburg,Nearfield Systems Inc, November 2012

The use of adaptive acquisition techniques to reduce the overall test time in planar near-field antenna measurements was presented in [1] & [2]. In those publications the concept of a decision function to track the uncertainty of a measurement as the data acquisition proceeds and also to adapt the acquisition region dynamically, was introduced. In this publication we build upon that work and present the concept of near-field array initialization. This is tested on different antennas and simulation results are presented. We also present actual measurement results to validate simulations that have to date been used to demonstrate advantages of the adaptive techniques.

A Cone Shaped Taper Chamber For Antenna Measurements Both In Near Field And Far Field In The 200 Mhz To 18 Ghz Frequency Range
Vicente Rodriguez, November 2012

Traditionally Taper chambers are constructed using a square based pyramidal shaped taper. The taper is then shaped into an octagon and finally transformed into a cylindrical launch section. This approach is related to the manufacturability of different absorber cuts. This presentation introduces a chamber where the conical shape of the launch in continued through the entire length of the taper chamber. The results are of the free space VSWR test over a 1.5m diameter quiet zone are presented at different frequencies. The conical taper appears to have a better illumination wave front and better QZ levels even at frequencies above 2GHz than the standard traditional approach. The implementation of this design was done in Singapore and the actual chamber was designed to have a secondary Near Field range for Planar and spherical scans.

Adaptive Sampling In Spherical And Cylindrical Near-Field Antenna Measurementsadaptive Sampling In Spherical And Cylindrical Near-Field Antenna Measurements
M. Ayyaz Qureshi, Carsten H. Schmidt, and Thomas F. Eibert, November 2012

An adaptive approach for optimized sampling in cylindrical and spherical near-field antenna measurements is described. The presented technique applies higher sampling density in rapidly varying near-field regions and skips data points in the smoother regions. Abrupt changes in the near field are detected by comparing the extrapolated and the measured near-field values at coarser sampling points during the measurements. A decision function based on signal-to-noise ratio of the measured value is used to determine the threshold difference between the extrapolated and the measured near-field value for skipping the sampling point. The reduced near-field data collected is processed using the fast irregular antenna field transformation algorithm (FIAFTA). FIAFTA is computationally efficient and capable of handling data on irregular grids with full probe correction. Several test cases are then presented on the applicability of the given approach and significant reduction in the number of measurement points is observed, thereby reducing measurement time and the computational effort.

Adaptive Sampling In Spherical And Cylindrical Near-Field Antenna Measurementsadaptive Sampling In Spherical And Cylindrical Near-Field Antenna Measurements
M. Ayyaz Qureshi, Carsten H. Schmidt, and Thomas F. Eibert, November 2012

An adaptive approach for optimized sampling in cylindrical and spherical near-field antenna measurements is described. The presented technique applies higher sampling density in rapidly varying near-field regions and skips data points in the smoother regions. Abrupt changes in the near field are detected by comparing the extrapolated and the measured near-field values at coarser sampling points during the measurements. A decision function based on signal-to-noise ratio of the measured value is used to determine the threshold difference between the extrapolated and the measured near-field value for skipping the sampling point. The reduced near-field data collected is processed using the fast irregular antenna field transformation algorithm (FIAFTA). FIAFTA is computationally efficient and capable of handling data on irregular grids with full probe correction. Several test cases are then presented on the applicability of the given approach and significant reduction in the number of measurement points is observed, thereby reducing measurement time and the computational effort.

Comparative Probe Parameter Error Analysis For Planar Near-Field Measurements With A Novel Approach For Reduced Probe-Aut Interaction
M. Ayyaz Qureshi, Carsten H. Schmidt, and Thomas F. Eibert, November 2012

Far-field uncertainty due to probe errors in planar near-field measurements is analyzed for the fast irregular antenna field transformation algorithm. Results are compared with the classical technique employing two dimensional Fast Fourier Transform (2D FFT). Errors involving probe's relative pattern, alignment, transverse and longitudinal position, interaction with AUT etc. have been considered for planar measurements. The multiple reflections error originating from the interaction of the probe and the AUT tends to deteriorate the radiation pattern to a greater extent. Therefore, a novel technique which utilizes near-field measurements on two partial planes is presented to reduce the multiple reflections between the probe and the AUT.

Range Multipath Reduction In Plane-Polar Near-Field Antenna Measurements
Stuart Gregson, Allen Newell, Greg Hindman, Pat Pelland, November 2012

This paper details a recent advance that, for the first time, enables the Mathematical Absorber Reflection Suppression (MARS) technique to be successfully deployed to correct measurements taken using plane-polar near-field antenna test systems with reduced AUT-to-probe separation. This paper provides an overview of the measurement, transformation, and post-processing. Preliminary results of range measurements are presented and discussed that illustrate the success of the new planepolar MARS technique by utilising redundancy within the near-field measured data that enables comparisons to be obtained and verified by using two existing, alternative, scattering suppression methodologies.

Echo Suppression By Spatial Filtering Techniques In Advanced Planar And Spherical Nf Antenna Measurements
L. J. Foged, L. Scialacqua, F. Mioc, F. Saccardi, P. O. Iversen, L. Shmidov, R. Braun, J. L. Araque Quijano, G. Vecchi, November 2012

This paper presents a comparative investigation of two versatile error mitigation techniques applicable to general antenna near field measurement scenarios with echo signals of unknown origin. Both techniques are based on spatial filtering of the measured field taking advantage of the apriori knowledge of the antenna size. The first approach takes advantages of the spatial filtering properties of the spherical waves expansion of the measured field. The second approach is based on the reconstruction of equivalent currents and implements the spatial filtering as a direct consequence of the selected size and shape of the reconstruction surface. The investigation is performed using measured data on two different horns in both planar and spherical near field scanning geometries. The presence and levels of echo pollution in the measurements are controlled by introducing known scattering objects in the anechoic chambers and comparing to reference situations without disturbance.

An Experimental Validation Of The Near-Field - Far-Field Transformation With Spherical Spiral Scan
F. D'Agostino , F. Ferrara , J.A. Fordham, C. Gennarelli, R. Guerriero, M. Migliozzi, November 2012

This work concerns the experimental validation of a probe compensated near-field – far-field transformation technique using a spherical spiral scanning, which allows one to significantly reduce the measurement time by means of continuous and synchronized movements of the positioning systems of the probe and antenna under test. Such a technique relies on the nonredundant sampling representations of the electromagnetic fields and makes use of a two-dimensional optimal sampling interpolation formula to recover the near-field data needed to perform the classical spherical near-field – far-field transformation. The good agreement between the so reconstructed far-field patterns and those obtained via the classical spherical near-field – far-field transformation assesses the effectiveness of the approach.

Exact Solutions In Antenna Holography Using Planar, Spherical, Or Cylindrical Near-Field Data
George G. Cheng, Yong Zhu, and Jan Grzesik, November 2012

We present exact solutions to antenna holography problems based on planar, spherical, or cylindrical nearfield data. Full field distribution information in the source region is determined exactly, from two tangential field components over a planar, spherical, or cylindrical surface. Stated in so many words, all three components of both electric and magnetic fields in the antenna aperture are obtained exactly from two-component near-field data. Conventional antenna holography relies upon back transformation for planar near-field data, and upon optimization schemes for both spherical and cylindrical near-field data. It is both acknowledged and accepted that the back transform is only an approximate solution due to its far-field nature, whereas optimization algorithms are vulnerable to convergence instability and, moreover, are computationally intensive. Our approach tackles holography by solving an inverse scattering problem, with exact solutions derived on the basis of three common types of near-field data. A mapping algorithm is proposed herein which determines the field everywhere, in both interior and exterior regions, based on a single-slice nearfield data capture. It provides exact antenna holography solutions analytically, with the full electric and magnetic fields disclosed throughout the source region. The field mapping algorithm is a direct, closed-form solution which is numerically straightforward and efficient. Verification is carried out and demonstrated by analytic examples and numerical simulations, as well as by hardware measurements. Nine test examples are given. Analytic examples include dipole arrays deployed across planar, spherical, and cylindrical regions, and a narrow azimuthal slot on a conducting sphere. The simulation example exposes the structure of a slotted array antenna based upon its near-field data as generated by a commercial software package. The hardware measurements address themselves to a concrete embodiment of that same slotted array antenna, an elongated sector antenna, and to a patch antenna. Excellent agreement is found in all test cases.

3D Image Generation From Arbitrary Antenna Measurement Data By Solving The Full Vectorial Inverse Source Problem
Georg Schnattinger, and Thomas F. Eibert, November 2012

A fast algorithm is presented for the generation of 3D current density images of antennas utilizing arbitrary antenna measurement data. The images represent a broadband equivalent current distribution which radiates the same fields as the true current distribution on the antenna structure in a broad frequency band. These equivalent currents convey important information about the antenna. The imaging algorithm can efficiently handle arbitrary measurement geometries and probe characteristics. It is inspired by the Multi-Level Fast Multipole Method (MLFMM). The near-field compensation and probe correction is realized using a modified adjoint operator based on adaptive fast multipole translations. Due to the modifications, a priori knowledge about the field observation density can be exploited and the generated image becomes more accurate. The complexity of the proposed approach is identical to a fast Fourier transform (FFT) based imaging algorithm. Numerical examples are given to prove

Dynamic Rcs Measurement With A Network Analyzer
Luca Fiori, Antonio Sarri, Riccardo Cioni, Stefano Sensani, Domenico A. Fittipaldi, November 2012

IDS has developed a RCS measurement solution capable to operate both in indoor and outdoor test ranges. The solution is based on the Agilent PNA series of network analyzers, whose performance are enhanced by a dedicated RF front end (named "Pulser"), resulting in a low-cost, compact and flexible system covering the frequency band from 2GHz to 18GHz. At first, the capability of the measurement solution was verified in a near field test range, demonstrating sensitivity compliant with low observable platform requirements (typical values of Noise Equivalent RCS can be in the order of -50 dBsm indoor at 30 m). Recently the RF front end has been upgraded to be usable for outdoor dynamic RCS measurements as well, being the upgraded solution named "Pulser_EV". This paper describes the performance of the Pulser_EV, its application field and possible developments.

Focused Beam Measurement Of Antenna Gain Patterns
James G. Maloney, John W. Schultz, James Fraley, Matthew Habib, Kathleen Cummings-Maloney, November 2012

The focused beam measurement technique has proven to be a solid technique for free space measurement of electromagnetic material properties. This paper presents the use of the focused beam method to measure swept frequency antenna gain as well as antenna patterns. A calibration and signal processing procedure has been developed to properly handle the range of incident waves inherent in the Gaussian beam illumination. One disadvantage of this technique is that the size of the antenna under test is limited by the spot size of the focused beam. However, the GTRI focused beam system uses lenses that are easily reconfigured to realize various spot sizes. The advantage of the focused beam illumination is that the number of measurements and thus measurement time is reduced by roughly an order of magnitude when compared to spherical near-field scanning techniques. More importantly, focused beam systems can be used in a lab environment and do not require large dedicated chambers. We present both model/theory predictions and measured data of how a too-small spot size of the focused beam leads to systematically lower peak gain measurements and wider beam widths.

On The Development Of 18-45 Ghz Antennas For Towed Decoys And Suitability Thereof For Far-Field And Near-Field Measurements
Matthew Radway, Nathan Sutton, Dejan Filipovic, Stuart Gregson, Kim Hassett, November 2012

The development of a wideband, high-power capable 18-45 GHz quad-ridge horn antenna for a small towed decoy platform is discussed. Similarity between the system-driven antenna specifications and typical requirements for gain and probe standards in antenna measurements (that is, mechanical rigidity, null-free forward-hemisphere patterns, wide bandwidth, impedance match, polarization purity) is used to assess the quad-ridge horn as an alternative probe antenna to the typical open-ended rectangular waveguide probe for measurements of broadband, broad-beam antennas. Suitability for the spherical near-field measurements is evaluated through the finite element-based full-wave simulations and measurements using the in-house NSI 700S-30 system. Comparison with the near-field measurements using standard rectangular waveguide probes operating in 18-26.5 GHz, 26.5-40 GHz, and 33-50 GHz ranges is used to evaluate the quality of the data obtained (both amplitude and phase) as well as the overall time and labor needed to complete the measurements. It is found that, for AUTs subtending a sufficiently small solid angle of the probe’s field of view, the discussed antenna represents an alternative to typical OEWG probes for 18-45 GHz measurements.

Antenna Measurements: Test & Analysis Of The Radiated Emissions Of The Nasa/Orion Spacecraft ~ Parachute System Simulator
John Norgard, November 2012

For future NASA Manned Space Exploration of the Moon and Mars, a blunt body capsule, called the Orion Crew Exploration Vehicle (CEV), composed of a Crew Module (CM) and a Service Module (SM), with a parachute decent assembly is planned for reentry back to Earth. A Capsule Parachute Assembly System (CPAS) is being developed for preliminary parachute drop tests at the Yuma Proving Ground (YPG) to simulate high-speed reentry to Earth from beyond Low-Earth-Orbit (LEO) and to provide measurements of landing parameters and parachute loads. The avionics systems on CPAS also provide mission critical firing events to deploy, reef, and release the parachutes in three stages (extraction, drogues, mains) using mortars and pressure cartridge assemblies. In addition, a Mid-Air Delivery System (MDS) is used to separate the capsule from the sled that is used to eject the capsule from the back of the drop plane. Also, high-speed and high-definition cameras in a Video Camera System (VCS) are used to film the drop plane extraction and parachute landing events. To verify Electromagnetic Compatibility (EMC) of the CPAS system from unintentional radiation, Electromagnetic Interference (EMI) measurements are being made inside a semi-anechoic chamber at NASA/JSC at 1m from the electronic components of the CPAS system. In addition, EMI measurements of the integrated CPAS system are being made inside a hanger at YPG. These near-field B-Dot probe measurements on the surface of a parachute simulator (DART) are being extrapolated outward to the 1m standard distance for comparison to the MIL-STD radiated emissions limit.

Controlling the Far-Field Resolution in Near-Field Antenna Characterization
A. Capozzoli,C. Curcioi, A. Liseno, November 2011
Adaptive Acquisition Techniques For Planar Near-Field Antenna Measurements
D. Janse van Rensburg,D. McNamara, G. Parsons, November 2011

The use of adaptive acquisition techniques to reduce the overall test time in planar near-field antenna measurements is described. A decision function is used to track the accuracy of a measurement as the data acquisition proceeds, and to halt such acquisition when this is considered sufficient for the measured quantity of importance. Possible decision functions are defined and compared. Several test cases are presented to show that significant test time reduction is possible when compared to traditional acquisition schemes.







help@amta.org
2024 Antenna Measurement Techniques Association. All Rights Reserved.
AMTA_logo_115x115.png
 
 

CONNECT WITH US


Calendar

S M T W T F S
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31