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.)
Crystallographic sample design of complex media influences material tensor properties. These properties offer amplitude, phase and polarization control of the electromagnetic (EM) fields. Previous works have evaluated crystallographic sample designs for isotropic, uniaxial and biaxial anisotropic media, each respective design offering more ways to control the fields. The tensor elements for these designs are all aligned along the main diagonal of the permittivity and/or permeability tensors. Additional field control can be obtained by producing materials that have off-diagonal tensor elements in addition to the aforementioned main diagonal elements. A monoclinic crystal sample design supports the existence of two off-diagonal elements and offers more field control than biaxial anisotropic media. In this work, field analysis is performed on media that possesses a monoclinic tensor element arrangement, demonstrating the additional control over EM fields as compared to biaxial anisotropic media. A monoclinic sample is then constituted using crystallographic symmetry. Future work will yield the development and analysis of a monoclinic sample material measurement capability.
Open-area test site (OATS) is a basic range for measuring omni antennas at VHF/HUF band. Reflections from the trees nearby, from the edge of the metal ground plane of an OATS are researched with the aid of ultra-broadband calculable dipole antennas (CDAs). Usually, these reflections are detrimental to precise antenna measurements from 20 MHz to 1 GHz; however they are very difficult to analyze accurately, since no rigorous theory exists on the relationship between the reflections and the configurations of an OATS. For this difficulty, a pair of very accurate and broadband CDAs are manufactured and verified with a slightly modified near-field method, whose site-insertion-loss deviation (?SIL) between measurements and simulation is less than 0.3 dB over 10 MHz to 340 MHz for a single pair of dipole elements resonated at 90 MHz. Based on the optimized CDAs, the effects of ground plane sizes, wire mesh shapes around the edge of the metal ground plane, trees nearby and especially masts are researched. The research shows that the reflections from the edge of an optimized ground plane is less than 0.1 dB at 10 m range. Finally, the performance of an OATS with these optimizations is verified: for 10 m separation, ?SIL is within 0.26 dB at horizontal polarization (HP) and within 0.34 dB at vertical polarization (VP) for the typical 24 frequencies from 30 MHz to 1 GHz; at 20 m separation, ?SIL is within 0.59 dB (HP) and 0.85 dB (VP) from 20 MHz to 500 MHz. An example for the uncertainty of calibration the free-space antenna factor of tuned dipole antennas are provided, too.
Flexibility and reconfigurability technologies for antenna designs are presented, investigated and merged in this paper to design a flexible and reconfigurable antenna. Prior to designing the proposed antenna, a review was undertaken to choose the best antenna configuration and flexible substrate that meet the flexibility and reconfigurability objectives. It is concluded that planar printed antennas with coplanar waveguide (CPW) feeding are the most attractive designs due to the ease of fabrication for flexible antennas and the ease of integration of active devices for reconfigurability. This paper presents a flexible reconfigurable antenna, which is designed based on the concept of printed folded slot antennas with CPW feeding technique. The High Frequency Structure Simulator (HFSS) is used to design and simulate the proposed antenna. It is designed on a very thin flexible substrate, Polyethylene terephthalate (PET) film, which is chosen since it has a low loss compared to other flexible substrates, such as paper type substrates. Moreover, it is less fragile than other substrates when it is used for high bending applications. From the literature, slot antennas and folded slot antennas are reconfigured by altering the length of the slot to tune the resonant frequency. Here we present an alternate technique to reconfigure folded slot antennas. One PIN-diode is used to redirect the current on the internal stub inside the slot, which results in a radiating stub, acts as a dipole for a second resonant frequency. When the PIN-diode is forward biased (ON), the proposed antenna has a single band due to the slot at 2.42 GHz for Wireless Local Area Network (WLAN) applications. When the PIN-diode is reversed biased (OFF), the proposed antenna is dual-band, linearly polarized with different orientations, one polarization due to the slot at 2.4 GHz and the other due to the stub inside the slot at 3.62 GHz. This provides WLAN and Worldwide Interoperability for Microwave Access (WiMAX) for wireless systems. The proposed flexible reconfigurable antenna is designed and simulated for both curved and flat configurations to ensure that the antenna maintains its radiation characteristics when it is used for wearable conformal applications.
The National Institute of Standards and Technology (NIST) has developed computationally efficient algorithms for probe location and polarization compensation in near- to far-field transformations for use when measurements are not made on the standard canonical grids. A major application of such methods is at higher frequencies, where it is difficult or impractical to locate a probe to required tolerances for the standard transforms. Our algorithms require knowledge of the actual position of the probe at the measurement points. This information can be furnished by state-of-the-art optical tracking devices. Probe position information is routinely obtained by the NIST CROMMA (Configurable Robotic MilliMeter-wave Antenna) Facility. Even at lower frequencies, probe-location compensation techniques allow in principle, the use of less precise and therefore, less expensive scanning hardware. Our approach also provides the flexibility to process data intentionally collected on nonstandard grids (plane-polar, spiral, etc.) or with mixed geometries (such as a cylinder with a hemispherical or planar end cap). We present simulations and actual probe position compensation results at 183 GHz. The possibility of compensating for known variations in the probe pointing is considered.
Mars rover Direct-to-Earth (DTE) communication is an exciting new development that can maintain transfer of high volumes of scientific data from Mars to Earth. Currently, large orbiting assets are used as a relay to return scientific data, often containing higher data rates than current DTE systems. Therefore, the goal of this paper is to investigate antenna array topologies to augment DTE systems to support high data rates. The antenna design is complex, having to simultaneously support dual-band, high gain, high power handling, and circular polarization capabilities. An exhaustive study of patch elements in literature shows that current geometries are infeasible for a Mars rover DTE system. A CP Half E-shaped patch element is developed, containing important dual band S11/AR performance in the required RX and TX bands while featuring a single-feed single-layer design. Moreover, various subarray architectures are evaluated to determine if the gain requirements can be achieved. To meet this gain requirement, a 4x4 subarray topology is designed which allows a modular, scalable, and high gain design. To feed each of the 4x4 element subarrays, a stripline feed network is developed, consisting of a binomial impedance transformer and a four stage 1:2 power divider. This feed network supported a broadside radiation pattern for the subarray topology. These components are then integrated, first through a full wave simulation in HFSS. This rigorous study showed support for Mars rover DTE communications systems. The integrated subarray design is then fabricated and measured using a spherical near-field chamber in the UCLA Center for High Frequency Electronics (CHFE) facilities where measurements showed a very good comparison to the simulation results. Overall this integrated subarray design was successful, showing dual-band, high gain, high power handling, and CP performance.
Antenna range calibration is commonly performed with the goal of obtaining the gain of an antenna under test. The most straightforward calibration procedure makes assumptions about the polarization properties of the range illumination, which can lead to both polarization and gain errors in the measured patterns. After introducing the concept of polarization correction we describe three published range polarization correction techniques and provide an example of polarization correction applied to a compact antenna test range measurement. We then discuss the practical aspects of incorporating polarization correction into the range calibration workflow.
Comparisons are made between far-field patterns of an X-band polarization reference horn obtained using the equally-spaced, latitude, and uniform near-field measurement grids. All of the far-fields were obtained by transforming the measured near-field data. Measurement and data processing times are also presented, such that the reader can understand the benefits and drawbacks of the equally-spaced, latitude, and uniform grids. In addition to these comparisons, the sampling requirements of the latitude grid are investigated. In the past, it has been recommended to thin the uniform grid near the poles of the measurement sphere, which is referred to as latitude sampling. The typical method is to multiply the number of sample points required on the equator by a sin(theta) weighting function to obtain the number of sample points required near the poles. However, it will be shown that the sin(theta) weighting function may lead to aliasing in certain cases, and a new method is proposed which is guaranteed to minimize aliasing for any antenna-under-test. We refer to this new grid as the Maximum Fourier Content (MFC) latitude grid.
A single reflector CATR exhibits certain depolarizing properties, as any other offset reflector antenna, when illuminated by a linearly polarized feed in its focal point. One way to improve the polarization purity in the Quite Zone (QZ) is to use a feed antenna which aperture fields provide a conjugate match to the electric-field distribution in the reflector’s focal plane when illuminated with a linearly polarized plane wave. MVG developed and built a proof-of-concept demonstrator in the form of a 3x1 array of linearly polarized elements, exited to match the focal plane distribution as predicted by a full-wave simulation of the specific range. This demonstrator has been installed in the CATR at RWTH Aachen University, which is a corner-fed serrated edge reflector system with a 1.2 m diameter QZ and a specified maximum cross polarization level of -30 dB (edge of QZ) due to the offset geometry. In this paper we will show measurement results for planar co- and cross-polar probing of the QZ in X-band, using the demonstrator and compare it to the respective results using the range’s conventional, low cross polarization, corrugated feed horn. The measured data will also be cross-checked against the full-wave simulation results for the fields in the QZ. Furthermore, we will compare 0°, 90°, ±45° pattern cuts of a demanding Antenna Under Test, a 40 cm x 40 cm offset reflector antenna with a wide band dual ridge horn as a feed, again using the demonstrator and the conventional feed. This is to show the potential improvement in measurement quality by using a matched feed in a single reflector CATR.
Backscattering responses of range-extended objects include those attributed to traveling-wave effects, typically caused by the termination of the object. Diagnosing the nature of scattering mechanisms contributing to the composite response is essential to modifying the object's radar signature. ISAR images reveal essential information on the location and nature of scattering features by decomposing the frequency/angle data into basis functions corresponding to independent point scatterers. When applied to responses of objects exhibiting other basis functions, such as those for traveling-wave scattering, ISAR images reveal unexpected results that can obscure proper interpretation of the scattering mechanisms. Because traveling-wave lobes are restricted to limited ranges of grazing angles and are frequency dependent, however, localizing their effects from high-resolution images can be elusive. Specifically, the traveling-wave responses are not readily distinguished from direct or diffracted responses. The paper deals with backscattering data collected on a slender cylindrical rod of 183cm length and 0.635cm diameter for aspect angles 0-180 degrees over a frequency range of 2-10GHz with polarization parallel to the plane of incidence, intended to emphasize effects of traveling waves at the rod's grazing angles. In spite of its relatively simiple geometry, the linear rod object presents complicated responses owing to the combined effects of traveling waves and multiple diffractions. Although ISAR images properly locate point scatterers, an understanding of the imaging process provides clues on the expected location of image elements corresponding to more complicated scattering features. The angle and frequency dependence of each scattering mechanism is illustrated in the paper by frequency responses, range responses, and ISAR images. The total scattering resonse of the rod for grazing incidence is characterized by at least 5 distinct scattering mechanisms, each interacting with the others as a function of viewing angle. Because images of traveling- and diffracted-wave components overlap for some grazing angles, their relative responses preclude separation. The results provide an example of the complex nature of scattering from a simple shape subject to traveling-wave effects.
The boresight roll scan is a simple yet powerful tool for antenna range characterization and diagnostics. In this type of measurement a linearly-polarized antenna with high axial ratio (such as a standard gain horn) is rotated about its mechanical boresight axis while magnitude and phase data are collected. Post-processing of these data provides a wealth of information about the source polarization characteristics, and can also be used to diagnose common problems such as receiver compression, mechanical misalignment, drift, and flexing cables. This paper describes the theory and implementation of the boresight roll scan, and provides examples of how different types of range errors manifest in the processed data.
Performance requirements for compact ranges are typically specified as metrics describing the quiet zone's electromagnetic-field quality. The typical metrics are amplitude taper and ripple, phase variation, and cross polarization. Acceptance testing of compact ranges involves phase probing of the quiet zone to confirm that these metrics are within their specified limits. It is expected that if the metrics are met, then measurements of an antenna placed within that quiet zone will have acceptably low uncertainty. However, a literature search on the relationship of these parameters to resultant errors in antenna measurement yields limited published documentation on the subject. Various methods for determining the uncertainty in antenna measurements have been previously developed and presented for far-field and near-field antenna measurements. An uncertainty analysis for a compact range would include, as one of its terms, the quality of the field illuminating on the antenna of interest. In a compact range, the illumination is non-ideal in amplitude, phase and polarization. Error sources such as reflector surface inaccuracies, chamber-induced stray signals, reflector and edge treatment geometry, and instrumentation RF leakage, perturb the illumination from ideal.
Antenna and Radar Cross Section (RCS) measurements are often required for orientation sets (cuts) that are difficult or impossible to produce with the positioning instrumentation available in a given lab. This paper describes a general coordinate transform, combined with a general polarization rotation to correct for these orientation differences. The technique is general, and three specific examples from actual test programs are provided. The first is for an RCS measurement of a component mounted in a flat-top test fixture. The component is designed to be mounted in a platform at an orientation not feasible for the flat-top fixture, and the test matrix calls for conic angle cuts of the platform. The transforms result in a coordinated, simultaneous two-axis motion profile and corresponding polarization rotations yielding the same information as if the component had been mounted in the actual platform. The second example is for a pattern measurement of an antenna suite mounted on a cylindrical platform (such as a projectile). In this case, the test matrix calls for a roll-cut, but the range positioning system does not include a roll positioner. The transforms again result in a coordinated, simultaneous two-axis motion profile and corresponding polarization rotations to provide the same information as the required roll-cut but without the use of a roll positioner. Finally, the third example is for an antenna pattern measurement consisting of an extremely large number of cuts consisting of conic yaw cuts, roll cuts and pitch cuts. The chosen method involves the use of the Boeing string suspension system to produce great-circle cuts at various pitch angles combined with the use of the coordinate and polarization transforms to emulate, off-line, any arbitrary cut over any axis or even multiple axes. Keywords: Algorithm, Positioning, Polarization, Coordinates, RCS
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.
Broad band, dual polarized probes are becoming increasingly popular options for use in near-field antenna measurements. These probes allow one to reduce cost and setup time by replacing several narrowband probes like open-ended waveguides (OEWG) with a single device covering multiple waveguide bands. These probes are also ideal for production environments, where chamber throughput should be maximized. Unfortunately, these broadband probes have some disadvantages that must be quantified and corrected for in order to make them viable for high accuracy near-field measurements. Most of these broadband probes do not have low cross polarization levels across their full operating bandwidths and may also have undesirable artifacts in the main component of their patterns at some frequencies. Both of these factors will result in measurement errors when used as probes. Furthermore, the use of a dual port RF switch adds an additional level of uncertainty in the form of port-to-port channel balance errors that must be accounted for. This paper will describe procedures to calibrate the pattern and polarization properties of broad band, dual polarized probes with an emphasis on a newly developed polarization correction algorithm. A simple procedure to measure and correct for amplitude and phase imbalance entering the two ports of the near-field probe will also be presented. Measured results of the three calibration procedures (pattern, polarization, channel balance) will be presented for a dual-polarized, broad band quad-ridged horn antenna. Once calibrated, this probe was used to measure a standard gain horn (SGH) and will be compared to baseline measurements acquired using a good polarization standard open-ended waveguide (OEWG). Results with and without the various calibration algorithms will illustrate the advantage to using all three routines to yield high accuracy far-field pattern data.
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.
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.
Abstract: A novel Inset fed microstrip patch antenna is designed on defected ground structure (DGS) to reduce the higher order harmonics and cross polarized radiations. Square rings, and square shaped slots are placed on the ground plane of the microstrip patch antenna to get the desired operation. These annular ring and arc DGS appears to be highly efficient in terms of suppressing the cross polarization. Relative suppression of radiated field is observed by placing and without placing the defected ground structures. The stop band property exhibited by the DGS is used to filter out the harmonics. The current model successfully reduced the DGS size and by comparing with the well known design, size reduction of 20% is achieved. Instead of normal square patch, a slotted aperture patch model is considered in the current design to reduce the overall size of the antenna.
Phase variation = +/-10 deg. 18 to 40 GHz Phase variation = +/-20 deg. 40 to 110 GHz Cross Polarization = -30 dB III. MAXIMUM AVAILABLE SPACE Consistency of performance across a waveguide band levies demands on compact range feeds. Because of the constraint of the room size, the design starts with determining the maximum space available for the This paper addresses a recent compact range development by MI reflector. The next step will be to determine the combination of Technologies that achieves desired extended low frequency and reflector body and edge treatment size within that space to millimeter wave performance (1 to 110GHz) while maintaining a deliver the desired performance. To determine the space cost effective reflector size and a small range footprint. The paper available for the reflector a chamber layout analysis is will explore the conventional rule-of-thumb relationships performed. Appropriate absorber is selected and, allowing for between feed, reflector, edge treatments and range geometries an air gap of at least 2 wavelengths at the lowest desired while contrasting them to the resultant design. The paper will frequency between the absorber and the reflector, and allowing highlight an impressive new family of compact range feeds and advancements in cost effectively achieving a superior reflector height for the compact range feed positioner yields the surface. allowable reflector dimensions to be 194 inches high and 222 inches wide as shown in Table 2. The combination of reflector
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.