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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.
We present a test procedure and results that compare RF performance of traditional pyramidal absorber to that with latex coating. Measurements were performed from 5 to 15 GHz, but the same measurement methodology can be applied to other frequency bands. Absorber with protective coating is being used in place of traditional absorber for outdoor antenna measurement facilities to reduce degradation of the absorber performance in harsh environments. Knowledge of the RF performance characteristics of coated absorber is especially necessary when it is used to replace uncoated absorber in an operational antenna measurement facility. Measurements are performed with a simple measurement setup based on a vector network analyzer and broadband horn antennas. Results from bi-static and mono-static measurements are presented.
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.
Over-the-air performance testing of MIMO wireless devices requires the simulation of an RF environment similar to that experienced in the real world. There are a number of standardized spatial channel models that are considered acceptable for evaluating MIMO performance of LTE devices. A number of different methods have been proposed for generating MIMO test environments, but the ability of those methods to reproduce a target wireless channel, and the results they produce, vary. There are several methods for evaluating a spatial channel that are useful validation tools if the goal is to produce a specific known environment. This paper will present the results from several of those for different test cases. In addition, a set of reference device antenna systems have been developed to allow one MIMO radio to be tested with antennas designed for "good", "nominal", and "bad" performance. In this way, the ability of a MIMO test system to provide a relative distinction between different levels of device performance may be assessed. This presentation will show results of this comparison for different system configurations and channel models and provide an indication of the suitability of these systems for evaluating MIMO device performance."
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.
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.
A novel electromagnetic measurement technique using an active screen is presented. The main advantage of this technique is that it can remove contributions from non-stationary or fluctuating backgrounds, even if they are within the same measurement range gate of the target. This technique is particularly useful in cases where the beam width of the measurement antenna has to be wide enough to encompass the cross-range extent of the target. The technique is demonstrated for scattering measurement.
ABSTRACT
Scattered field . Escatt A profile reconstruction method using a surface acquisition domain inverse currents technique is presented. The method makes use of the internal fields radiated by an . equivalent currents distribution retrieved from scattered field information collected from multiple incident fields. The main advantage of this method with respect to other inverse source-based techniques . E is the use of surface formulation for the inverse problem, which reduces the problem dimensionality thus decreasing the computational cost
Two of the three algorithms require an estimate of the element pattern, which they assume to be common to all the elements. We describe our measurement of our array’s element pattern, as well as the use of the IsoFilter™ to center the element pattern and limit the edge effects.
A general, accurate, and efficient stand-alone commercial program for antenna diagnostics, DIATOOL, has been developed by TICRA. The software reconstructs the field or the equivalent currents on a plane or an arbitrary 3D surface enclosing the antenna. The fundamental properties of the underlying field-reconstruction techniques have been reported previously, and the paper therefore focuses on the capabilities of the developed software by considering two test cases where real measurement data are employed.
TESTING LARGE WIRELESS DEVICES IN SMALL ANECHOIC CHAMBERS 100_0967100_0973 James D. Huff -20.00-18.00-16.00-14.00-12.00-10.00-8.00-6.00-4.00-2.000.00050100150200Relative Power (dB) Theta Angle (deg) Uncorrected Dipole Patterns 0,0,00,0,120,0,18-20.00-18.00-16.00-14.00-12.00
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.
A spherical array designed for hemispherical coverage of satellite communications at S-band that is approximated by hexagonal and pentagonal planar panels. Ball Aerospace built a segment of a 10m diameter spherical array that has one center pentagonal panel and five surrounding hexagonal panels. This paper describes our efforts at testing one large hexagonal panel in a compact range.
Mobile applications of wireless devices require increasing network performance with high data rates and good quality of service. To address these requirements the Multiple-Input Multiple-Output (MIMO) techniques have recently been added to wireless standa
The DGA-MI and the CEA/CESTA collaborated to measure and compute the RCS of a specific target. It is an empty PEC cylinder with a rectangular aperture. Resonant frequencies are expected to appear when the frequency of the illumination signal increases. Th
While ripple on standard gain horn measurements utilizing harmonic mixing has long been recognized and compensated for with the use of attenuators and isolators another approach using high pass filters is examined.
This paper describes the behavior of the antenna radiation pattern for different planar near-field measurement errors superimposed on the near-field data. The disturbed radiating near field is processed using multilevel plane wave based near-field far-field transformation to determine the far-field. Errors like scan area truncation, transverse and longitudinal position inaccuracy of measurement points, and irregular sample spacing are analyzed for an electrically large parabolic reflector at 40 GHz. The error behavior is then compared with the standard transformation technique employing 2D Fast Fourier Transform (FFT) using the same near-field data. In order to exclude the effect of any other measurement or environmental error, electric dipoles with appropriate magnitude profile and geometrical arrangement are used to model the test antenna.