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Abstract: In order to characterize the Boeing 9-77 compact range, the empty chamber background was measured as a function of frequency, polarization, and the azimuth angle of the upper turn-table (UTT). The results exhibited a near-field diffraction pattern with enlarged hot-spots on a 4-fold symmetry [1]. A 2-D FFT on the diffraction pattern yielded a mapping on the relative arrangement of the absorbers on the UTT [2]. In this paper, we take a closer look at the scattering geometry of the UTT as illuminated by the residual field above and beyond the quiet zone (QZ). The different responses in VV and HH are discussed. The enhanced diffraction due to a “blazed grating” condition is identified and analyzed.
Abstract—In order to optimize accuracy of near field measurements, it is required not only to acquire data for two orthogonal polarizations, but the relative amplitude and phase balance between the two channels must also be accurately matched. This can be difficult at millimeter wave frequencies because of the transmission lines and other components involved. ORBIT/FR has explored multiple methods of achieving optimum vertical and horizontal polarization matching and found a very simple solution to achieve acceptable results. Some of the methods investigated included the use of dual-polarized feeds, dual single-polarized feeds mounted adjacently, waveguide rotary joints with a mechanically rotated feed, and a mechanically-rotated feed using a 1.0 mm coaxial-based cable. Interestingly, the mechanically-rotated feed with coaxial cable provided acceptable results on par with or better than the other methods, which moreover results in a very simple implementation in the measurement system. Measured results are presented for the chosen implementation demonstrating the near field data quality is adequate for a variety of antennas.
Abstract— Measurements and strategies for the calculation of radar cross-sections in the shorter millimeter wave region, especially of objects that include rough surfaces, are discussed. Because of decreasing wavelength, roughness becomes more significant in this spectral region, but also more difficult to characterize. A tabletop radar cross-section measurement system was set up to measure scattering from canonical objects and rough objects with regular or random patterns using a swept frequency continuous wave system. Random, rough objects of different surface roughnesses were measured and fit to statistical distributions governed by optical speckle theory. In this paper we consider the inclusion of optical speckle theory in the electromagnetic codes to address both issues associated with the characterization of target surfaces and the time required for numerical calculations.
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Abstract— In this study we analyze a canonical outdoor antenna measurement environment from automotive industry’s perspective, with the goal of identifying relevant parameters related to range design and analysis. Specifically, we examine to what extent simple ray tracing models are able to describe range behavior. Comparisons were made between simple ray tracing models, free space scenario, and full wave calculations were presented. This is further put into context by incorporating common environmental factors into the analysis, such as asphalt driveway, grass, antenna supporting structure, and control room’s nearby presence. We examine the differences between outcomes generated by different models, while taking into account common frequency bands of interest for the automotive industry, including FM, RKE, DAB, TV, and higher frequency applications. Field distribution around AUT location is profiled and presented for multiple scenarios, as well as for different transmit/reference antennas.
Abstract— A special X-band PEC-backed dipole with integrated split coaxial balun was designed, fabricated, and tested for feeding a low-profile parabolic reflector. The aperture size and height of the reflector is 7.876” and 2.0315”, respectively. The reflector is covered with a 1/16” Teflon sheet radome for weather protection. The antenna has a measured peak gain of 23.72dB and first side lobe level of less than –25dB at 10.2GHz in both E and H planes. The worst case 3dB beamwidth is 11.09o in the H-plane. The -10 dB reflection coefficient bandwidth of this design is from 9.5 to 11 GHz. The E and H plane patterns were designed to have similar tapering and minimum coupling between TX and RX reflector antennas in an array configuration. Within an array configuration the measured coupling level is less than -66dB from 9.5 to 11 GHz.
Abstract— In order to achieve precise antenna pattern measurement in mm-wave frequency region, we propose a cylindrical near-field antenna measurement system using photomixing technique with UTC-PD. Due to this system, we can use an optical fiber as the transmission line of mm-wave signal and downsize the mm-wave signal source. Accordingly, we can achieve flexible cable movement and suppress the disturbance from the waveguide components. In this paper, we will show the measured near-field distribution on cylindrical coordinate by the proposed system and calculated far-field antenna pattern of standard gain horn antenna in W-band.
The core technology to this innovative chamber design is the invention of a new feed structure which integrates the design of the chamber’s wall, and reduces the multipath effects from the walls. In this design, the absorbing materials are integrated as a part of its feeding wall thereof to produce a homogeneous property on the plane, i.e., the plane parallel to the feeding wall. The material attached to the other walls has a non-homogeneous property on the plane parallel to its corresponding attached wall, which allows the scattering of incident field in a widely spread fashion.
Abstract— This paper presents an original way for the design simulation, implementation, and measurement of a multiband flexible textile antenna. The aim is to realize an antenna with a dipolar radiation at several resonance frequencies. The radiating element is a monopole antenna. This antenna naturally exhibits a dipole and a quadripole radiation pattern for the first and second resonance frequency respectively. This behavior is due to the current distribution on the antenna. To constrain the second mode to change into a dipolar radiation pattern, two decorrelated and non-radiating parasitic elements are added to the antenna. At this second resonance frequency, the current distribution is different from the one of the quadripolar mode by the parasitic elements. The dimensions of these parasitic elements are defined by electromagnetic simulations and measurements. To validate this method, the monopole antenna is studied. The radiating element of the antenna is sewn on the textile flexible substrate. This substrate was previously characterized in terms of relative permittivity and losses. The near-field magnetic field and the far-field radiation pattern are studied in simulations and measurements.
surfaces overagroundplane hasbeenusedfor anumber ofultra--wideband(UWB) applications.Thispaperdiscussespracticalchallenges associatedwithaccuratecharacterization andverificationofmultilayer UWBantennasdesignedfor highpowerapplications.Akeydesignconstraintforhighpowerantennasisanextremelylowimpedancemismatch atthefeedterminalsneededtoefficientlycoupleenergyintothe antenna.Carefuldesign and optimization oftheantennalayersandradiatingsurfacecantheoreticallyachievetherequiredefficiencies.However,verificationofthedesignischallengingduetopracticallimitations ofboththeantennafabricationprocessand measurementmethodologies.Analysisoftheantennaarchitecturefromatestandevaluationperspective isusedtoidentify potentialmeasurementriskareasandguidethedevelopmentofanincremental testmethodologydesignedtomitigateorbetter understand therisks.Laboratory testcouponswere fabricatedandmeasuredtodetermineconstitutivelayerandcompositestack--up performance.Throughtheincrementaltestingmethodology,developerswereabletodeterminethat prototypeperformancewas limitedduetothevariabilityofetchedresistor valuesonthe drivenlayer.Thepaperconcludes withashortdiscussionoffrequencyscalabilityandsummaryofplansforfuturetests.
Abstract— Antenna arrays works at their peak performance when they are well calibrated at the factory. Once they are employed in a real environment, they might be subject to unpredictable disturbances. That’s why recalibration after operational deployment is required but is usually not done due to practical difficulties. In some applications such as Direction Finding (DF), direction of arrival estimation is susceptible to the antenna model errors. However, the evolution of Direction finding antenna, as the strong integration of an antenna array mounted on a vehicle and the use of more efficient antennas tend to increase this type of disturbances. This paper proposes to evaluate the benefit of an in-situ measurement system for detecting and compensating the disturbance of antenna radiation. The influence of permanent scatters on one hand and variables (open door…) on the other hand in the vicinity of antenna array is investigated. We present a quantitative study of a biased calibration using a model combining 3D electromagnetic simulation, a complete receiver model and a MUSIC direction of arrival algorithm characterization. Two antennas arrays with same height are compared: a standard dipole array and an electrically small UWB antenna array.
Abstract— A fully polarimetric compact radar range operating at a center frequency of 100 GHz has been developed for obtaining radar cross section, inverse synthetic aperture radar imagery and high range resolution profiles on targets and structures of interest. The 100 GHz radar range provides scale-model RCS measurements for a variety of convenient scale factors including W-Band (1:1 scale), C-band (1:16 scale), and S-band (1:26 scale). An overview of the radar range is provided in this paper along with measurement examples of ISAR scale-model imaging, scale-model through-wall imaging, and preliminary kHz sweep-rate Doppler that demonstrate a few of the diverse and unique applications for this system. The 100 GHz transceiver consists of a fast-switching, stepped, CW microwave synthesizer driving dual-transmit and dual-receive frequency multiplier chains. The stepped resolution of the system’s frequency sweep is sufficient for unambiguous resolution of the entire chamber. The compact range reflector is a CNC machined aluminum reflector edge-treated with FIRAM™-160 absorber serrations and fed from the side to produce a clean quiet zone. This range is the latest addition to a suite of compact radar ranges developed by the Submillimeter-Wave Technology Laboratory providing scale-model radar measurements at nearly all of the common radar bands.
In the literature, one can find a low scattering photodiode modulated-probe for microwave near field imaging. The frequency response of the probe is computed at 2.45 GHz. In this paper, however a new formulation for computing the scattered field for low frequencies (from 150 MHz) by a broadband near field probe based on the impedance matrix is developed. In addition, a method to increase the scattered power by controlling matching will be shown.
Abstract—It is well-known that a complete bistatic set of near-.eld scattering data is required to compute far-.eld radar cross section (RCS) quantities. In many practical applications, however, only monostatic scattering data is available. Almost all algorithms for the transformation of monostatic near-.eld data are based on the synthetic aperture radar (SAR) image representation.Since these algorithms are often acceleratedbythe fastFouriertransform(FFT),they usuallypose manylimitations on the measurement procedure such as regularly spaced grids and separate treatment of the different polarizations due to scalar processing. In this paper, a novel and .exible algorithm is presented which is not based on the FFT but on multi-level fast multipole method (MLFMM) principles. Therefore, it is similar to the fast irregular antenna .eld transformation algorithm (FIAFTA) which has been designed for the transformation of antenna .elds and measurements. Numerical results of different scenarios show that these principles can also be successfully applied to monostatic scattering data. In summary, this approach is superior to existing algorithms, because it provides more .exibility while it is still very ef.cient.
Key words: 900 Microstrip Coupler, Metamaterial, Size Reduction, Split Ring Resonators, Rose Curve Resonators
The use of pre-conditioning interpolation schemes, as a possible means of enhancing the performance of previously introduced adaptive acquisition algorithms for spherical near-field (SNF) test time reduction, is evaluated. Investigations have been carried out to establish whether the adaptive SNF approach is suited to test engineering practice are reported. The pre-conditioning method involving the acquisition of two orthogonal polar cuts on the near-field sphere and the separate linear interpolation of two complex spherical components of the NF data is shown to be the preferred scheme. This method is evaluated for three different antennas using specific acquisition rules, and decision functions related to directivity, amplitude error, and side lobe level.
Abstract—Cognitive Communications techniques are important for white space communications and spectrum sharing. Disaster recovery and green field communications could also be aided by such Context Aware systems. These networks could benefit from new compact, multi-band, active antenna implementations.
MI Technologies has delivered two new state of the art compact range measurement systems and has worked with Panasonic to develop automated test systems that have reduced the test time by more than a factor of 4. The range design includes significant automation, integration with the antenna’s built in up and down converters, and the ranges are reversible.
Abstract—Four arm Log-Periodic (LP) antennas are frequency independent antennas that are capable of producing dual circular polarizations from the same aperture and over the same bandwidth making them more versatile than commonly used spiral antennas. In this paper we present a four arm LP that is capable of being a high power radiator. Each pair of arms of the LP is fed with a microstrip line that functions as both an impedance transformer and a 180° balun, thereby greatly simplifying the required beamformer. The antenna is tested successfully up to 500W of input CW power. Post high power characterizations of the antenna (far-field gain, radiation patterns, and VSWR) for linear polarization are presented and the stable high power performance of the antenna is demonstrated. With an appropriate beamformer, good quality circular polarization can be expected. Presented results should pave the way for use of the LP in relevant wideband high power applications.
Implementation of a Novel Low-Cost Low-Profile Ku-Band Antenna Array for Single Beam Steering from Space TMM 4TMM 13i25mil 50mil 150mil 5° g Nicholas K. Host, Chi-Chih Chen, John L. Volakis