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Recent enhancements in military telecommunication systems for monitoring and tracking in low VHF range (30-80MHz) imply the use of specific antenna measurement facilities to characterize either the antenna alone or the antenna mounted on a supporting structure which can be heavy and bulky. The indoor Near-Field approach shows benefits in terms of compactness. However this approach involves issues due to high levels of reflectivity of the anechoic chamber, the antenna under test positioner and the measurement probe structure at these larges wavelengths. Studies and simulations of each contribution have been performed in a previous paper. The proposed paper focuses on the improvement of measurement results using post-processing techniques and associated uncertainty analysis of the mono-probe near-field system at the CNES. First the new 50-400 MHz dual polarized probe and the measurement system are briefly presented. Then the estimation of each error term is detailed providing a global error budget in order to appreciate the benefit of post-processing technique. All the considered errors terms are all of those included in the well-known 18 NIST terms. Each of them is evaluated using the most appropriated approaches (specific measurement, simulation).
Legacy methods for testing the performance of radome panels and finished radomes have always been in isolation from the system antenna, for many reasons. The legacy method of testing employed horn antennas at relatively close distances, a fixed-frequency signal source, and primitive receivers. More modern systems used much better receivers capable of measuring both phase and amplitude, and these gave way to automatic network analyzers. The network analyzer system also replaces the fixed-frequency source, because it has its own step-frequency source. The rest of the setup remains the same. A network analyzer can itself be calibrated, but that calibration cannot include the probe antennas, nor can it account for interactions, particularly at normal incidence. With increasing demands on performance, it is essential that the interaction effects of the probe antennas with the radome be removed. The micorwave integrated circuit industry has the identical problem. The circuit probes that are used to reach into the circuit assemblies have very small tips, and the internal elements to accomplish this size reduction make probe mataching difficult. Thus the probe parameters become embedded into the overall measured response. The circuit testing community has developed a process to de-embed these probes, yielding the S-parameters of the circuit under test in isolation from surroundings. This paper investigates a method for applying this closed-system technique to open-system testing, such as panel-measuremsnt tables, by using a secondary calibration technique that is adapted to open systems. This effectively extends the calibration of the analyzer system to encompass the probes, thus improving accuracy.
A technique is presented for determining the pattern of an antenna in the focused near-field from cylindrical near-field measurements. Although the same objective could be achieved by conventional near-field to far-field transformation followed by a back projection, the proposed technique has an intuitive appeal and is considerably simpler and faster. The focused near-field antenna pattern is obtained by applying Huygens’ principle, as embodied in the field equivalent principle, directly to near-field measurements and by including an “obliquity factor” to suppress backlobe radiation. The technique was experimentally verified by comparison with far-field patterns obtained by conventional cylindrical near-field to far-field transformation and by EM simulations. Excellent agreement in sidelobe levels and beamwidth was achieved. The technique was applied to the 25 in diameter reflector antenna of a harmonic radar operating at 5.8 GHz and 11.6 GHz. Since the operating range of this radar is less than 40 ft, the reflector is the near-field at both frequencies. By defocusing the reflector at the harmonic frequency the beamwidths and gains at both frequencies can be made the same. The defocusing is accomplished by exploiting the frequency dependent phase center displacement of a log-periodic feed.
There are many methods of aligning feeds on a dual cylindrical parabolic sub-reflector compact range. Presented in this paper is a laser tracker and Field probe method that was used to align the RF feed to the sub-reflectors. The laser tracker provides real time positional error measurements that are mapped and these results are used to fine tune the alignment of RF feed to the phase centers of the dual cylindrical parabolic sub-reflectors. Field probe test scans are performed to verify QZ performance of various alignment positions measured comparing scans of amplitude, phase and taper. The laser tracker alignment method provides an efficient and a highly accurate method to achieving precision alignment of the RF feed to the sub-reflector system installed into the dual reflector compact range. High accuracy antenna measurements in a compact range require precision alignment of the RF feed to the sub-reflectors phase center. The quality and size of the RF plane wave field of the quiet zone (QZ) performance is affected by the alignment of the RF feed and sub-reflector system combination. This alignment is accomplished through mechanical adjustments of the x-y-z axis RF feed positioning system. Measurements of both mechanical and electrical bore site is performed and compared across the full measurement spectrum to verify the compact antenna test range (CATR) system positioning accuracy.
Experimental measurement plays a key role for technology maturation in an R&D environment. In this paper we highlight the versatility of a new compact range at the Air Force Research Laboratory (AFRL), Sensors Directorate. In its first year of operation, the OneRY Range supported a wide variety of projects ranging from electrically small antennas to 20’ structures, spanning frequencies of 400 MHz to 45 GHz, and involving applications covering land, airborne, and space-based platforms. Here we present measured results from three different antenna development efforts for the Air Force. The first effort involves a UHF meta-material inspired antenna developed for an airborne application. In addition to successfully demonstrating relatively low frequency capability for a compact range, this effort met the challenge to measure antenna patterns from a physically large target. Results from OneRY are compared to those collected from a tapered chamber. Next we show experimental measurement of digital beam forming (DBF) in a large conformal phased array antenna operating at L and S bands. The DBF experimental testing is part of a follow-on effort to an Advance Technology Demonstration conformal array supporting satellite tracking, telemetry and command (TT&C). Finally, we present results from a “quick look” investigation into the operability of a COTS antenna system matched to a third party radome. The project supports airborne satellite communications at K, Ka, and Q bands. Performance of a high frequency extension (18-50 GHz) to the compact range is examined to include an inter-range comparison to planar near-field measurements. A description of the OneRY Indoor Range is also provided.
The outdoor range at the U. S. Army’s Electronic Proving Ground Antenna Test Facility features a large reflector in order to facilitate radar cross-section and antenna performance evaluation with large targets. Constructed during the late 1980s and early 1990s, this range features a 67-foot diameter reflector to satisfy quiet zone size specifications. The reflector is composed of 138 individual panels with nominal panel separation of 0.06 inches. This research investigates the impact of these gaps between reflector panels on the field received at the quiet zone. GTRI’s physical optics computational code was used to analyze the existing range design at the frequencies of interest, from C- through Ka-band, taking into account edge diffraction from the panels. In research presented at AMTA 2013, a range modification of the ground between the range source antenna and the reflector was performed to minimize ground reflections. This range modification has been incorporated with current research to provide quiet zone field analysis which includes reflector gaps as well as ground reflections.
A popular method for microwave characterization of materials is the free-space focused beam technique, which uses lenses or shaped reflectors to focus energy onto a confined region of a material specimen. In the 2-18 GHz band, 60 cm diameter lenses are typically spaced 30 to 90 cm from the specimen under test to form a Gaussian focused beam with plane-wave like characteristics at the focal point. This method has proved popular because of its accuracy and flexibility. Another free-space measurement technique that has been employed by some is the use of dielectrically loaded antennas that are placed in close proximity to a specimen. In this alternate technique, the dielectrically loaded antennas are smaller than lenses, making the hardware more compact and lower cost, however this is done at the expense of potentially reduced accuracy. This paper directly compares a standard laboratory focused beam system to a measurement system based on some recently developed RF spot probes. The spot probes are specially designed antennas that are encapsulated in a dielectric and optimized to provide a small illumination spot 3 to 8 cm in front of the probe. Experimental measurements of several dielectric, magnetic, and resistive specimens were measured by both systems for direct comparison. With these data, uncertainty analysis comparisons were made for both fixtures to establish measurement limits and capability differences between the two methods. Understanding these uncertainties and measurement limits are key to implementing compact spot probes in a manufacturing setting for quality assurance purposes.
Although highly accurate relative position data can be achieved using laser tracking systems which are suitable for millimeter wave antenna characterization, a considerable gap exists in the ability to absolutely align antennas to laser tracker target coordinate systems. In particular this scenario arises in millimeter wave near-field measurements where probe antenna aperture dimensions are on the order of a millimeter, and the position of its origin must be known to better than 1/20th of a wavelength, and orientation known to fractions of a degree. The fragile nature and dimensions of such antenna negate the use of coordinated metrology measurement systems and larger touch probes typically used for accurate spatial characterization. The Antenna Metrology Laboratory at NIST in Boulder, Colorado is developing a new machine vision based technique for measuring the absolute position of small (~1 mm) millimeter wave antenna apertures relative to a laser tracker target coordinate system. A synergy with existing laser tracking systems, this approach will provide a non-contact method for determining the absolute position and orientation coordinate frame of the probe antenna aperture in all six degrees of freedom to within 30-60 microns. This alignment system technique is demonstrated using the CROMMA Facility at NIST in Boulder, CO.
The development of the Configurable Robotic Millimeter-Wave Antenna facility (CROMMA) by the antenna metrology lab at the National Institute of Standards and Technology in Boulder Colorado has brought together several important aspects of 6-degree-of-freedom robotic motion, positioning and spatial metrology useful for high frequency antenna characterization. In particular, the ability to define a unified coordinated metrology space, which includes all the motion components of the system is at the heart of this facility. We present the details of integrating robotics that have well defined kinematic models, advanced spatial metrology techniques, and millimeter wave components which make up the CROMMA facility. From this, a high level of precision, accuracy, and traceability that is requisite for performing high frequency near-field antenna pattern measurements can be achieved. Emphasis is placed on the ability to precisely characterize and model the movement patterns of the robot positioners, and probe and test antenna apertures using state-of-the-art full 6-degree-of-freedom spatial metrology, while being able to manipulate this information in a unified measurement space. The advantages of using a unified coordinated metrology space as they pertain to complex antenna alignments, scan geometry, repeatability analysis, traceability, and uncertainty analysis will be discussed. In addition we will also discuss how the high level of positioning, and orientation knowledge obtainable with the CROMMA facility can enable the implementation of sophisticated near-field position correction algorithms and precisely configurable scan geometries.
In the near future, we will begin adorning our bodies with wearable devices, and the ubiquitous computing society will dawn. Personal area network (PAN), which uses the human body as a transmission channel, has been proposed by T. G. Zimmerman as a solution for networking these personal devices. The social concern regarding PAN's use for biomedical engineering has been growing due to Japan's low birthrate and longevity. ?Studies have focused on developing PAN applications, such as real-time healthcare sensing devices, following the trend of medicine-engineering cooperation. Since applications are still in their initial phase, a trial-and-error method is applied to device development. There are still many opaque areas regarding a transmission mechanism. ?So far, we have clarified that the electromagnetic wave generated from a 10 MHz PAN device propagates through the surface of the human body. If the frequency band of the surface wave, instead of radiation, becomes clear in air, it excels in privacy, and we can expect lower energy consumption. Transmission efficiency can also be expected to increase due to the adoption of the electrode structure, which excites a surface wave. ?In this paper, we clarify the propagation characteristics of the surface wave and advantageous frequency band for PAN. First, we constructed an experimental device like the Fabry-Perot resonator using the periodic structure of Yagi-Uda antenna directors with reflectors in both ends for the measurement of surface waves. Next, "solid phantom," which is equivalent to biological tissue, was installed in the device. Moreover, in order to demonstrate measurement validity, we conducted numerical analysis using the finite-difference time-domain method.
It is well known that a field probe acts as a filter for the measured antenna under test (AUT) fields, whose influence can be either described in spatial or in spectral domain. Directive probes, for instance, serve to filter out signals that originate far away from the boresight axis. However, there are several drawbacks to the use of such directive probes including the possibility of multiple reflections and probe nulls. This contribution discusses the application of beamforming techniques to suppress unwanted echo signals in planar near-field antenna measurements. The AUT is measured with a small probe antenna such as is normally used for such measurements. Neighboring measurement signals are thereafter combined in a moving average manner in order to generate the signal as would be measured by a probe array. Successive filter lengths, such as 3x3, 5x5, etc., are utilized such that the valid angle is preserved without extending the measurement plane. The generated near-field signals are then transformed using a flexible plane wave based near-field far-field transformation algorithm. Probe correction does not reverse the reduction in multipath signals achieved by the use of a directive probe or beamforming since sources are assumed only within the minimum sphere enclosing the AUT. Results are presented for simulated data with substantially improved results of the far-field pattern of the AUT.
In classical probe-corrected spherical near-field measurements, one source of measurement errors, not often given sufficient consideration is the probe [1-3]. Standard near-field to far-field (NFFF) transformation software applies probe correction with the assumption that the probe pattern behaves with a µ=±1 azimuthal dependence. In reality, any physically-realizable probe is just an approximation to this ideal case. Probe excitation errors, finite manufacturing tolerances, and probe interaction with the mounting interface and absorbers are examples of errors that can lead to presence of higher-order spherical modes in the probe pattern [4-5]. This in turn leads to errors in the measurements. Although probe correction techniques for higher-order probes are feasible [6], they are highly demanding in terms of implementation complexity as well as in terms of calibration and post-processing time. Thus, probes with high azimuthal mode purity are generally preferred. Dual polarized probes for modern high-accuracy measurement systems have strict requirements in terms of pattern shape, polarization purity, return loss and port-to-port isolation. As a desired feature of modern probes the useable bandwidth should exceed that of the antenna under test so that probe mounting and alignment is performed only once during a measurement campaign. Consequently, the probe design is a trade-off between performance requirements and usable bandwidth. High performance, dual polarized probe rely on balanced feeding in the orthomode junction (OMJ) to achieve good performance on a wide, more than octave, bandwidth [5-7]. Excitation errors of the balanced feeding must be minimized to reduce the excitation of higher order spherical modes. Balanced feeding on a wide bandwidth has been mainly realized with external feeding network and the finite accuracy of the external components constitutes the upper limits on the achievable performance. In this paper, a new OMJ designed entirely in waveguide and capable of covering more than an octave bandwidth will be presented. The excitation purity of the balanced feeding is limited only by the manufacturing accuracy of the waveguide. The paper presents the waveguide based OMJ concept including probe design covering the bandwidth from 18-40GHz using a single and dual apertures. The experimental validation is completed with measurements on the dual aperture probe in the DTU-ESA Spherical Near-Field facility in Denmark. References: [1]Standard Test Procedures for Antennas, IEEE Std.149-1979 [2]Recommended Practice for Near-Field Antenna Measurements, IEEE 1720-2012 [3]J. E. Hansen (ed.), Spherical Near-Field Antenna Measurements, Peter Peregrinus Ltd., on behalf of IEE, London, UK, 1988 [4]L. J. Foged, A. Giacomini, R. Morbidini, J. Estrada, S. Pivnenko, “Design and experimental verification of Ka-band Near Field probe based on wideband OMJ with minimum higher order spherical mode content”, 34th Annual Symposium of the Antenna Measurement Techniques Association, AMTA, October 2012, Seattle, Washington, USA [5]L. J. Foged, A. Giacomini, R. Morbidini, “Probe performance limitation due to excitation errors in external beam forming network”, 33rd Annual Symposium of the Antenna Measurement Techniques Association, AMTA, October 2011, Englewood, Colorado, USA [6]T. Laitinen, S. Pivnenko, J. M. Nielsen, and O. Breinbjerg, “Theory and practice of the FFT/matrix inversion technique for probe-corrected spherical near- eld antenna measurements with high-order probes,” IEEE Trans. Antennas Propag., vol. 58, no. 8, pp. 2623–2631, Aug. 2010. [7]L. J. Foged, A. Giacomini, R. Morbidini, "Wideband dual polarised open-ended waveguide probe", AMTA 2010 Symposium, October, Atlanta, Georgia, USA. [8]L. J. Foged, A. Giacomini, R. Morbidini, “ “Wideband Field Probes for Advanced Measurement Applications”, IEEE COMCAS 2011, 3rd International Conference on Microwaves, Communications, Antennas and Electronic Systems, Tel-Aviv, Israel, November 7-9, 2011.
Fieldprobing is often the tool of choice for validating the characteristics of a quiet zone (QZ). Some of the main disadvantageous of fieldprobing are the expense and stability of the setup, e.g. a stable non-reflective linear axis has to be build. Furthermore regular 1-dimensional fieldprobing is not very suited for detecting extraneous reflections in the measurement chamber. Former work has shown that using a second linear axis below the AUT positioner (which is sometimes present for Antenna Pattern Comparison (APC) measurements) can improve the detection, but further increases the cost factor. Using Spherical Near-Field scanning [FRANCIS,WITTMANN,BLACK,JOY] most of these disadvantageous are solved, only a rather simple, although sturdy, beam is built on top of the roll-over-azimuth positioner, placing the antenna on a sphere surrounding the QZ. Using only one measurement, for each frequency, a complete analysis of the measurement chamber can be performed. It can be used for both looking inside the QZ, i.e. chamber reflectivity and outside on extraneous reflections. This paper will show both actual spherical near-field and fieldprobing measurements of the CATR at the Institute of High Frequency Technology (IHF) of the RWTH Aachen, and compare both results.
In Compact Antenna Test Range (CATR) applications, better cross polar discrimination is often the main motivation for choosing the more complex and expensive compensated dual reflector system as opposed to the simpler and cheaper single reflector system. Other than reflector geometry adjustment, different options have been presented in the literature to improve the cross polar performance of the single reflector CATR [1-4]. One solution is the insertion of a polarization selective grid between the feed and the reflector. The shape of the grids curved strip geometry is determined from the geometry of the reflector and each polarization has a different shape. This approach has been demonstrated to provide Quit Zone (QZ) cross polar performances similar to the dual reflector system on a decade bandwidth. The drawback of this solution is that orthogonal polarizations components cannot be measured simultaneously since a different polarizer grid is required for each polarization [1-2]. Other techniques aim at improving both amplitude/phase taper and cross polarization are based on measurement post processing. Processing techniques have been proposed based on numerical modelling of the range [3] or by de-convoluting the measured pattern with a predetermined range response based on QZ probing [4]. The drawback of these methods are the finite accuracy of the post processing, increased measurement complexity and the difficulty to measure active antenna systems. Recently, the application of conjugated matched feeds for reflector systems aimed at cross polar reduction in space application have received attention in the literature [5-10]. Recognizing, that the cross polar contribution induced by the offset reflector geometry has a focal plane distribution very similar to the higher order modes in feed horns, various techniques have been devised to excite compensating feed modes. Although a very elegant technique, the achievable bandwidth is limited and only single polarized solutions have been presented. A different concept of conjugated matched excitation, overcoming the dual polarization limitation has been introduced in [11-12] based on a patch array feed system. However, this implementation is aimed at applications with different beam-width in the principle planes. In this paper we will introduce a new feed horn concept, based on conjugate matched feeding, aiming at cross polar cancellation in single reflectors CATR systems. The proposed feed system is dual polarized and has an operational bandwidth of 1:1.5. The feed concept is introduced and the demonstrator hardware described. The target QZ <40dB cross polar discrimination is demonstrated by QZ probing of a standard single reflector CATR. References: [1] C. Dragone, "New grids for improved polarization diplexing of microwaves in reflector antennas," Antennas and Propagation, IEEE Transactions on , vol.26, no.3, pp.459-463, May 1978 [2] M.A.J. Griendt, V.J. Vokurka, “Polarization grids for applications in compact antenna test ranges”, 15th Annual Antenna Measurement Techniques Association Symposium, AMTA, October 1993, Dallas, Texas [3] W. D. Burnside, I. J. Gupta, "A method to remove GO taper and cross-polarization errors from compact range scattering measurements," ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM (APSURSI), June 1989, San Jose, California [4] D. N. Black and E. B. Joy, “Test zone eld compensation,” IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. 43, no. 4, pp. 362–368, Apr. 1995. [5] K. K. Shee, and W. T. Smith, “Optimizing Multimode Horn Feed Arrays for Offset Reflector Antennas Using a Constrained Minimization Algorithm to Reduce Cross Polarization”, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 45, No. 12, December 1997, pp. 1883-1885. [6] S. B. Sharma, D. Pujara, Member, S. B. Chakrabarty,r. Dey, "Cross-Polarization Cancellation in an Offset Parabolic Reflector Antenna Using a Corrugated Matched Feed", IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 8, 2009, pp. 861-864. [7] S. B. Sharma, D. A. Pujara, S. B. Chakrabarty, and V. K. Singh, “Improving the Cross-Polar Performance of an Offset Parabolic Reflector Antenna Using a Rectangular Matched Feed”, IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 8, 2009, pp. 513-516. [8] S. K. Sharma, and A. Tuteja, “Investigations on a triple mode waveguide horn capable of providing scanned radiation patterns”, ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM (APSURSI), July 11-17, 2010 [9] K. Bahadori, and Y. Rahmat-Samii, “Tri-Mode Horn Feeds Revisited: Cross-Pol Reduction in Compact Offset Reflector Antennas”, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 57, No. 9, September 2009. [10] Z. Allahgholi Pour, and L. Shafai, “A Simplified Feed Model for Investigating the Cross Polarization Reduction in Circular- and Elliptical-Rim Offset Reflector Antennas”, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, No. 3, March 2012, pp. 1261-1268. [11] R. Mizzoni, G. Orlando, and P. Valle, “Unfurlable Reflector SAR Antenna at P-Band”, Proc. of EuCAP 2009, Berlin, Germany. [12] P. Valle, G. Orlando, R. Mizzoni, F. Heliere, K. van ’t Klooster, “P-Band Feedarray for BIOMASS”, Proc. of EuCAP 2012, Prague, Czech Republic.
Numerical modeling within Computational Electromagnetics (CEM) solvers is an important engineering tool for supporting the evaluation and optimization of antenna placement on larger complex platforms. While measurements are still required for final validation due to the conclusiveness and high reliability of measured data, numerical modeling is increasingly used in the initial stages of antenna placement investigation, optimization and to ensure that final testing, often a complex procedure, has a positive outcome. In some cases, the full-wave representation of the source antenna is unavailable to the designer in the format required by the CEM solver. This is often the case if the source antenna is from a third party. To overcome this problem, an equivalent computational model of the antenna must be constructed, bearing in mind that CEM solvers require an accurate source representation to achieve reliable results. Equivalent sources or currents implemented in the commercial tool INSIGHT have been adopted as an efficient diagnostics and echo reduction tool in general antenna measurement scenarios as discussed in [1-6]. The INSIGHT processing of measured antenna data was initially developed as a numerical representation of antennas in complex environment analysis for CEM solvers [7-10]. The main obstacle for widespread use of this method was the handling of the proprietary format of the equivalent currents. Commercial CEM providers are currently investigating and implementing domain decomposition techniques based on the near field description of the local domain. This development also provides a direct link between INSIGHT processing of measured antenna data and numerical simulation opening a range of interesting applications for using measured antennas in commercial numerical simulation tools as discussed in [11-12]. In flush-mounted antenna applications the measurement and subsequent INSIGHT processing has to be carefully performed. This paper discusses guidelines for the correct source antenna measurement, post processing and successive link to the commercial numerical tools for simulation. Application examples of the link using CST STUDIO SUITE® software [14-17] with flush mounted antennas and comparison with measurements of the full structure will be provided. [1] http://www.satimo.com/software/insight [2] J. L. Araque Quijano, G. Vecchi. Improved accuracy source reconstruction on arbitrary 3-D surfaces. Antennas and Wireless Propagation Letters, IEEE, 8:1046–1049, 2009. [3] J. L. A. Quijano, G. Vecchi, L. Li, M. Sabbadini, L. Scialacqua, B. Bencivenga, F. Mioc, L. J. Foged "3D spatial filtering applications in spherical near field antenna measurements", AMTA 2010 Symposium, October, Atlanta, Georgia, USA. [4] L. Scialacqua, F. Saccardi, L. J. Foged, J. L. Araque Quijano, G. Vecchi, M. Sabbadini, “Practical Application of the Equivalent Source Method as an Antenna Diagnostics Tool”, AMTA Symposium, October 2011, Englewood, Colorado, USA [5] J. L. Araque Quijano, L. Scialacqua, J. Zackrisson, L. J. Foged, M. Sabbadini, G. Vecchi “Suppression of undesired radiated fields based on equivalent currents reconstruction from measured data”, IEEE Antenna and wireless propagation letters, vol. 10, 2011 p314-317. [6] L. J. Foged, L. Scialacqua, F. Mioc,F. Saccardi, P. O. Iversen, L. Shmidov, R. Braun, J. L. Araque Quijano, G. Vecchi" Echo Suppresion by Spatial Filtering Techniques in Advanced Planar and Spherical NF Antenna Measurements ", AMTA Symposium, October 2012, Seattle, Washington, USA [7] E. Di Giampaolo, F. Mioc, M. Sabbadini, F. Bardati, G. Marrocco, J. Monclard , L. Foged, “Numerical modeling using fast antenna measurements”, 28th ESA Antenna Workshop on Space Antenna Systems and Technologies, June 2005 [8] L. J. Foged, F. Mioc, B. Bencivenga, E. Di Giampaolo, M. Sabbadini “High frequency numerical modeling using measured sources”, IEEE Antennas and Propagation Society International Symposium, July 9-14, 2006. [9] F. Mioc, J. Araque Quijano, G. Vecchi, E. Martini, F. Milani, R. Guidi, L. J. Foged, M. Sabbadini, “Source Modelling and Pattern Enhancement for Antenna Farm Analysis”, 30th ESA Antenna Workshop on Antennas for Earth Observation, Science, Telecommunication and Navigation Space Missions, May 2008 ESA/ESTEC Noordwijk, The Netherlands [10] L. J. Foged, B. Bencivenga, F. Saccardi, L. Scialacqua, F. Mioc, G. Arcidiacono, M. Sabbadini, S. Filippone, E. di Giampaolo, “Characterisation of small Antennas on Electrically Large Structures using Measured Sources and Advanced Numerical Modelling”, 35th Annual Symposium of the Antenna Measurement Techniques Association, AMTA, October 2013, Columbus, Ohio, USA [11] L. J. Foged, L. Scialacqua, F. Saccardi, F. Mioc, D. Tallini, E. Leroux, U. Becker, J. L. Araque Quijano, G. Vecchi, “Bringing Numerical Simulation and Antenna Measurements Together”, 8th European Conference on Antennas and Propagation, EuCAP, April 2014, Den Haag, Netherlands [12] L. J. Foged, L. Scialacqua, F. Saccardi, F. Mioc, D. Tallini, E. Leroux, U. Becker, J. L. Araque Quijano, G. Vecchi “Innovative Representation of Antenna Measured Sources for Numerical Simulations”, IEEE International Symposium on Antennas and Propagation and USNC/URSI, July 2014, Memphis, Tennese, USA [13] L. J. Foged, B. Bencivenga, F. Saccardi, L. Scialacqua, F. Mioc, G. Arcidiacono, M. Sabbadini, S. Filippone, E. di Giampaolo, “Characterisation of small Antennas on Electrically Large Structures using Measured Sources and Advanced Numerical Modelling”, 35th Annual Symposium of the Antenna Measurement Techniques Association, AMTA, October 2013, Columbus, Ohio, USA [14] CST STUDIO SUITE™, CST AG, Germany, www.cst.com [15] T. Weiland: "RF & Microwave Simulators - From Component to System Design" Proceedings of the European Microwave Week (EUMW 2003), München, Oktober 2003, Vol. 2, pp. 591 - 596. [16] B. Krietenstein, R. Schuhmann, P. Thoma, T. Weiland: "The Perfect Boundary Approximation Technique facing the big challenge of High Precision Field Computation" Proc. of the XIX International Linear Accelerator Conference (LINAC 98), Chicago, USA, 1998, pp. 860-862. [17] D. Reinecke, P. Thoma, T. Weiland: "Treatment of thin, arbitrary curved PEC sheets with FDTD" IEEE Antennas and Propagation, Salt Lake City, USA, 2000, p. 26.
In this paper the inverse-source technique or source reconstruction technique has been applied as diagnostic tool to determine the complex excitation at sub array and single element level of a measured array antenna [1-5]. The inverse-source technique, implemented in the commercially available tool “INSIGHT” [5], allows to compute equivalent electric and magnetic currents providing exclusive diagnostic information about the measured antenna. By additional processing of the equivalent currents the user can gain insight to the realized excitation law at single element and sub-array level to identify possible errors. The array investigated in this paper is intended as part of the European Navigation System GALILEO and is a pre-development model flying on the In-Orbit Validation Element the GIOVE-B satellite. The antenna, developed by EADS-CASA Espacio, consists of 42 patch elements, divided into six sectors and is fed by a two level beam forming network (BFN). The BFN provide complex excitation coefficients of each array element to obtain the desired iso-flux shaped beam pattern [6-7]. The measurements have been performed in the new hybrid (Near Field and Compact Range) facility in the ESTEC CPTR as part of the installation and validation procedure [8]. The investigation has been performed without any prior information of the array and intended excitation. The input data for the analysis is the measured spherical NF data and the array topology and reference coordinate system. References [1] J. L. Araque Quijano, G. Vecchi. Improved accuracy source reconstruction on arbitrary 3-D surfaces. Antennas and Wireless Propagation Letters, IEEE, 8:1046–1049, 2009. [2] L. Scialacqua, F. Saccardi, L. J. Foged, J. L. Araque Quijano, G. Vecchi, M. Sabbadini, “Practical Application of the Equivalent Source Method as an Antenna Diagnostics Tool”, AMTA Symposium, October 2011, Englewood, Colorado, USA [3] J. L. Araque Quijano, L. Scialacqua, J. Zackrisson, L. J. Foged, M. Sabbadini, G. Vecchi “Suppression of undesired radiated fields based on equivalent currents reconstruction from measured data”, IEEE Antenna and wireless propagation letters, vol. 10, 2011 p314-317. [4] L. J. Foged, L. Scialacqua, F. Mioc,F. Saccardi, P. O. Iversen, L. Shmidov, R. Braun, J. L. Araque Quijano, G. Vecchi " Echo Suppresion by Spatial Filtering Techniques in Advanced Planar and Spherical NF Antenna Measurements ", AMTA Symposium, October 2012, Seattle, Washington, USA [5] http://www.satimo.com/software/insight [6] A. Montesano, F. Monjas, L.E. Cuesta, A. Olea, “GALILEO System Navigation Antenna for Global Positioning”, 28th ESA Antenna Workshop on Space [7] L.S. Drioli, C. Mangenot, “Microwave holography as a diagnostic tools: an application to the galileo navigation antenna”, 30th Annual Antenna Measurement Techniques Association Symposium, AMTA 2008, Boston, Massachusetts November 2008 [8] S. Burgos, M. Boumans, P. O. Iversen, C. Veiglhuber, U. Wagner, P. Miller, “Hybrid test range in the ESTEC compact payload test range”, 35th ESA Antenna Workshop on Antenna and Free Space RF Measurements ESA/ESTEC, The Netherlands, September 2013
For the purposes of antenna or radome measurement, a gimbal may be thought of as a compact, two or three axis antenna positioner with mutually orthogonal, intersecting axes. The unrelenting demand for higher accuracy in positioners of this type is driving innovation in mechanical architecture and design. A new position feedback technique, reflecting an enhanced understanding of position errors, and delivering unprecedented native encoder accuracy, has been developed and tested. New mechanical architecture has been created that allows for fully-featured two-axis gimbals to exist in the restricted confines behind an aircraft radome. The principal result of these developments is increasingly accurate and capable systems, particularly in the field of radome measurements. These new applications, techniques, architectures, and their results are explored in the following pages.
Abstract- Quality control is critical for all industrial processes, but often times defect detection is labor intensive. A novel approach to industrial defect detection is to use a random noise radar (RNR), coupled with Radio Frequency "Distinctive Native Attributes (RF-DNA)" fingerprinting processing algorithms to non-destructively interrogate microwave devices and classify defective units from properly functioning units. Example applications include assembly line inspection of automotive collision avoidance systems, wireless or cellular antenna defect detection during manufacture, and phased array element defect detection prior to RF system assembly. The RNR is uniquely suitable since it uses an Ultra Wideband noise waveform as an active interrogation method that will not cause destructive damage to microwave components. Additionally, it has been demonstrated that multiple RNRs can operate simultaneously in close proximity, allowing for significant parallelization of defect detection systems resulting in increased process throughput. Using this method, 100% sampling for quality control may be attainable in many cases. RF-DNA has previously demonstrated “serial number” discrimination of Orthogonal Frequency Division Multiplexed (OFDM), Direct Sequence Spread Spectrum (DSSS) network signals, GSM, WiMAX signals and others with classification accuracies above 80% using Multiple Discriminant Analysis and Generalized Relevance Learning Vector Quantification classification algorithms. Those cases all involved discrimination of passive emissions. This approach proposes to couple the classification successes of the RF-DNA fingerprinting with a non-destructive active interrogation waveform.
Measurement post-processing techniques based on spatial filtering have been presented as promising tools for the mitigation of echo’s deriving from the measurement environment in regular Near Field (NF) measurement scenarios [1]. The adaptation of these tools into standard measurement procedures depends on the possibility to demonstrate the real effectiveness in a given measurement scenario. The standard validation approach is to introduce a known disturbance into a measurement scenario and show the efficiency of the techniques in attenuating this disturbance. While highly effective as a functional demonstration of this approach the benefit of the echo reduction on an actual measurement scenario should still be evaluated on a case by case basis. A hybrid Near Field (NF) system has recently been installed in the existing dual reflector Compact Payload Test Range of ESTEC [2-3]. The installed system has been designed to perform spherical, cylindrical and planar NF measurements. Despite the design effort to optimize the NF system position in the chamber some interaction with the dual reflectors in the range were expected and for the PNF system in particular [4]. During the hybrid system acceptance measurements have been performed on the space array antenna intended as part of the European Navigation System GALILEO. The antenna is a pre-development model flying on the In-Orbit Validation Element, GIOVE-B satellite, developed by EADS-CASA Espacio [5-6]. This L-band antenna is particularly important test case for ESTEC since the PNF system will later be used in the final testing at space craft level on the GALILEO Satellites. This paper presents the preliminary finding of the MV-Echo post processing validation for PNF measurements in the hybrid range. The GALILEO array antenna has been measured in different configuration, with and without echo reduction processing and the results compared. The purpose of the activity was to quantify the benefits of the MV-Echo processing. Since the array is working in circular polarization it was possible to identify the major echo contributions as 2’nd order reflections. References [1] L. J. Foged, L. Scialacqua, F. Mioc, F. Saccardi, P. O. Iversen, L. Shmidov, R. Braun, J. L. Araque Quijano, G. Vecchi, “Echo Suppression by Spatial Filtering Techniques in Advanced Planar and Spherical NF antenna Measurements”, 34th Annual Symposium of the Antenna Measurement Techniques Association, AMTA, October 2012, Seattle, Washington, USA [2] S. Burgos, M. Boumans, P. O. Iversen, C. Veiglhuber, U. Wagner, P. Miller, “Hybrid test range in the ESTEC compact payload test range”, 35th ESA Antenna Workshop on Antenna and Free Space RF Measurements ESA/ESTEC, The Netherlands, September 2013 [3] S. Burgos, P. O. Iversen, T. Andersson, U. Wagner, T. Kozan, A. Jernberg, B. Priemer, M. Boumans, G. Pinchuk, R. Braun, L. Shmidov, “Near-Field Hybrid Test Range from 400 MHz to 50 GHz in the ESTEC Compact Payload Test Range with RF upgrade for high frequencies”, EUCAP 2014 [4] Paper on position of NF system in the range – was it astrium that did it? [5] L.S. Drioli, C. Mangenot, “Microwave holography as a diagnostic tools: an application to the galileo navigation antenna”, 30th Annual Antenna Measurement Techniques Association Symposium, AMTA 2008, Boston, Massachusetts November 2008 [6] A. Montesano, F. Monjas, L.E. Cuesta, A. Olea, “GALILEO System Navigation Antenna for Global Positioning”, 28th ESA Antenna Workshop on Space [7] J. E. Hansen, Spherical Near-Field Antenna Measurements, Peter Peregrinus Ltd. On behalf of IEE, London, United Kingdom, 1988. [8] F. Jensen, A. Frandsen, “On the number of modes in spherical wave expansion”, AMTA Symposium, October 2004, Stone Mountain, GA, USA.
The modelling and simulation of a modified bow tie antenna optimized for radar cross section measurement is described. The bow tie antenna shows improved transient response for radiating Ultra Wide Band pulses with decreased late time ringing. In applications such as radar cross section measurement, late time ringing caused by reflections at the open ends can mask objects of interest in close proximity. The antenna reduces reflections by resistive loading based on works by Lestari and Wu-King. Full wave modelling and simulation is done using CST Microwave Studio. S-Parameter and VSWR optimization by modification of the conductivity profile is demonstrated. Experimental verification of the model has been carried out and confirms both the properties of the antenna and the simulation.