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For future applications telecommunication satellites are built with increasing antenna sizes thus having high demands on the test volumes in antenna measurement facilities. AIRBUS Defence & Space provides highly accurate Compensated Compact Range facilities (CCRs) for antenna and payload testing. Mainly facilities of type CCR 75/60 with a quiet zone of 5 m diameter and facilities of type CCR 120/100 with a quiet zone size of 8 m diameter are installed in various countries. A quiet zone size of 5 m might become a limiting factor for test campaigns of future satellite generations. Since numerous CCR 75/60 facilities are installed worldwide, a quiet zone extension upgrade has been developed which allows enhancing the performance of existing facilities with relatively little effort. Lightweight extension panels are installed on upper and lower edges of sub and main reflector increasing the vertical quiet zone dimension. The possible enlargement of the quiet zone can be optimized to customer needs and is mainly driven by the available chamber dimensions. Besides the extension of the quiet zone dimension also the performance in the existing quiet zone will improve due to the larger reflector surfaces. The cross-polar purity goes down up to -60 dB. The first quiet zone extension upgrade has been recently performed at the facility of Thales Alenia Space in Cannes. The quiet zone has been extended from 5 m to 6 m in the vertical direction. A potential extension of the quiet zone up to 1.8 m has been analyzed and is feasible. The design, installation, and verification of the quiet zone extension will be presented in this paper. Quiet zone probing measurement results in C- and Ku-band will be shown.
Active S-parameters represent reflection coefficients of elements in an active phased array antenna under various element excitations. Active S-parameters can be calculated for any array excitation if the S-parameter matrix is fully characterized. In practice, the entries of this matrix can usually be gathered through measurements with a 2-port vector network analyzer (VNA). However, depending on the number of elements in the phased array, the number of measurements can be extremely large in order to obtain a full S-matrix. For a phased array consisting of N elements, N(N-1)/2 measurements with a 2-port VNA are required to obtain N-by-N S-matrix, assuming the antenna elements are reciprocal. In order to avoid large number of measurements, a scenario consisting of S-parameter measurements for the center element and also some elements located at the edges and corners of the array is proposed under a flexible predefined error criterion. Then, measured S-parameters are used to obtain N-by-N S-matrix via exploitation of the array symmetry and periodicity which is required to calculate the active S-parameters of the whole array. A fabricated uniform planar Vivaldi array with 112 elements is measured with the proposed scenario and calculated active S-parameters are compared with those obtained from full-wave analysis.
Measurement uncertainty is a vital parameter when assessing the performance of an antenna. Common measurement procedures such as field-probing give performance parameters of the quiet zone, such as amplitude-taper and ripple. However, relating these measurements to the actual measurement uncertainty is difficult at best. Furthermore the gain of the used probe has large influence on the outcome of the performance parameters, making measurement chamber intercomparison based on these parameters difficult. Quiet zone spherical near-field scanning fully describes the field distribution inside the quiet zone. Probe correction can be applied to compensate for the probe influence on the spherical modes. The mode spectrum consists of all electric waves propagating into the quiet zone. From the mode spectrum several performance parameters of the quiet zone can be derived. As an example the main beam power is concentrated in the m=±1 spectrum when aligned with the z-axis. Since other sources, having a different angle, have their mode spectrum spread over the m-spectrum, the power in m=±1 can be divided by the power in m?±1. This provides a signal-to-noise ratio which can be directly related to measurement uncertainty. Using the signal-to-noise ratio a new determination of the measured pattern uncertainty is found. In contrast to parameter derived from field-probing the new parameter is more general and comprehensive. In the paper we will derive new performance parameter and apply them to measured data in a CATR.
End-of-the-line over-the-air (OTA) testing of fully assembled wireless devices is one of the most important tests done in factories. It is designed to detect defective devices to avoid them being shipped out to the end customers. There are many requirements in designing over-the-air test systems for factory testing, including small factory real estate, measurement repeatability, and fast test time. These requirements prompt to challenges in OTA test system designs. Few existing widely-used test systems exist: near-field coupling systems where the test antenna is located very near the device’s antenna under test, small TEM cells, and shielded enclosures with one or several test antennas. Each technology has advantages and disadvantages, such as system size, defect detection capabilities/limitations, and performance measurement correlation to that from a far-field method. However, they all lack in dealing with improving test time with devices having technologies working with multiple simultaneous antennas/streams. For example, the current test time for a 2-antenna device (MIMO or received diversity capable devices) is doubled because each antenna chain is tested sequentially. Furthermore, possible coupling effect between antennas is not typically tested. The newly proposed OTA test system is an adaptive system with an array of test antenna elements inside a shielded enclosure. It takes advantage of the multi-path environment inside the enclosure to adapt itself and create a static channel environment with the specified requirement needs. For example, to improve test time for a 2-antenna device, the system groups the antenna elements of the system into two arrays to create two signal streams creating a 2x2-matrix channel with the cross-coupled matrix values minimized (e.g. minimization of the matrix condition number). This created static channel environment with optimized isolation between the two direct signal paths enables testing of the two antenna streams concurrently with minimized perturbation between the streams, hence reducing test time by almost half. The system will reconfigure the antenna elements for each test channel. This proposed new method of an adaptive over-the-air test system opens up to new ways of testing fully-assembled wireless devices in factories and also enables testing of certain performance qualities that current existing OTA test systems cannot perform.
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.
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.
In 2015, the Space Communications and Navigation (SCaN) Testbed project completed an S-Band ground station located at the NASA Glenn Research Center in Cleveland, Ohio. This S-Band ground station was developed to create a fully characterized and controllable dynamic link environment when testing novel communication techniques for Software Defined Radios and Cognitive Communication Systems. In order to provide a useful environment for potential experimenters, it was necessary to characterize various RF devices at both the component level in the lab and at the system level after integration. This paper will discuss some of the lab testing of the ground station components, with a particular focus / emphasis on the near-field measurements of the antenna. It will then describe the methodology for characterizing the installed ground station at the system level via a TDRS satellite, with specific focus given to the characterization of the ground station antenna pattern, where the max TDRS transmit power limited the validity of the non-noise floor received power data to the antenna main lobe region. Finally, the paper compares the results of each test as well as provides lessons learned from this type of testing methodology.
Within the standard scheme for probe-corrected spherical data-processing, it has been found that for an efficient computational implementation it is necessary to restrict the characteristics of the probe pattern such that it contains only azimuthal modes for which µ = ±1 [1, 2, 3]. This first-order pattern restriction does not however extend to placing a limit on the polar index mode content and therefore leaves the directivity of the probe unconstrained. Clearly, when using this widely utilized approach, errors will be present within the calculated probe-corrected test antenna spherical mode coefficients for cases where the probe is considered to have purely modes for which µ = ±1 and where the probe actually exhibits higher order mode structure. A number of analysis [4, 5, 6, 7, 8] and simulations [9, 10, 11, 12] can be found documented within the open literature that estimate the effect of using a probe with higher order modes. The following study is a further attempt to develop guidelines for the azimuthal and polar properties of the probe pattern and the measurement configuration that can be utilized to reduce the effect of higher order spherical modes to acceptable levels. ? [1] P.F. Wacker, ”Near-field antenna measurements using a spherical scan: Efficient data reduction with probe correction”, Conf. on Precision Electromagnetic Measurements, IEE Conf. Publ. No. 113, pp. 286-288, London, UK, 1974. [2] F. Jensen, ”On the probe compensation for near-field measurements on a sphere”, Archiv für Elektronik und Übertragung-stechnik, Vol. 29, No. 7/8, pp. 305-308, 1975. [3] J.E. Hansen, (Ed.) “Spherical near-field antenna measurements”, Peter Peregrinus, Ltd., on behalf of IEE, London, 1988. [4] T.A. Laitinen, S. Pivnenko, O. Breinbjerg, “Odd-order probe correction technique for spherical near-field antenna measurements,” Radio Sci., vol. 40, no. 5, 2005. [5] T.A. Laitinen, O. Breinbjerg, “A first/third-order probe correction technique for spherical near-field antenna measurements using three probe orientations,” IEEE Trans. Antennas Propag., vol. 56, pp. 1259–1268, May 2008. [6] T.A. Laitinen, J. M. Nielsen, S. Pivnenko, O. Breinbjerg, “On the application range of general high-order probe correction technique in spherical near-field antenna measurements,” presented at the 2nd Eur. Conf. on Antennas and Propagation (EuCAP’07), Edinburgh, U.K. Nov. 2007. [7] T.A. Laitinen, S. Pivnenko, O. Breinbjerg, “Theory and practice of the FFT/matrix inversion technique for probe-corrected spherical near-field antenna measurements with high-order probes”, IEEE Trans. Antennas Propag., vol. 58,, No. 8, pp. 2623–2631, August 2010. [8] T.A. Laitinen, S. Pivnenko, “On the truncation of the azimuthal mode spectrum of high-order probes in probe-corrected spherical near-field antenna measurements” AMTA, Denver, November 2012. [9] A.C. Newell, S.F. Gregson, “Estimating the effect of higher order modes in spherical near-field probe correction”, AMTA 34th Annual Meeting & Symposium, Seattle, WA, October. 2012. [10] A.C. Newell, S.F. Gregson, “Higher Order Mode probes in Spherical Near-Field Measurements”, EuCAP, Gothenburg, April, 2013. [11] A.C. Newell, S.F. Gregson, “Estimating the Effect of Higher Order Modes in Spherical Near-Field Probe Correction”, AMTA 35th Annual Meeting & Symposium, Seattle, WA, October. 2013. [12] A.C. Newell, S.F. Gregson, “Estimating the Effect of Higher Order Azimuthal Modes in Spherical Near-Field Probe Correction”, EuCAP, The Hague, April, 2014.
Abstract Antenna far field phase pattern is important for some applications. It can be directly obtained in pattern measurement by far field test range (FFTR) or compact range (CR). However, it is found that the antenna far field phase pattern measured by current near field test range (NFTR) is not correct. For a uniform phase feeding plane array, its far field phase pattern should be near constant in 3dB beam width. However, the antenna phase pattern measured by current NFTR looks square curve vs angle. This paper found out that the root cause of the error is due to different reference planes. Both the amplitude pattern and the phase pattern obtained by current NFTR, in fact, refer to the probe scanner plane, not the antenna plane. This shifting of the reference plane has no effect on amplitude pattern, but has effect on phase pattern. After that, a correction method is proposed. One example is used for the root cause finding and correction technique explanation. According to this paper, if one wants to get phase pattern using NFTR, it is necessary to measure the distance between AUT and probe aperture accurately so as to correct it accurately after measurement and obtain accurate phase pattern.
The Space Communications and Navigation (SCaN) Testbed project completed installation and checkout testing of a new S-Band ground station at the NASA Glenn Research Center in Cleveland, Ohio in 2015. As with all ground stations, a key alignment process must be conducted to obtain offset angles in azimuth (AZ) and elevation (EL). In telescopes with AZ-EL gimbals, this is normally done with a two-star alignment process, where telescope-based pointing vectors are derived from catalogued locations with the AZ-EL bias angles derived from the pointing vector difference. For an antenna, the process is complicated without an optical asset. For the present study, the solution was to utilize the gimbal control algorithm’s closed-loop tracking capability to acquire the peak received power signal automatically from two distinct NASA Tracking and Data Relay Satellite (TDRS) spacecraft, without a human making the pointing adjustments. Briefly, the TDRS satellite acts as a simulated optical source and the alignment process proceeds exactly the same way as a one-star alignment. The data reduction process, which will be discussed in the paper, results in two bias angles which are retained for future pointing determination. Finally, the paper compares the test results and provides lessons learned from this activity.
The single-offset compact antenna test range (CATR) is a widely deployed technique for broadband characterization of electrically large antennas at reduced range lengths [1]. The nature of the curvature and position of the offset parabolic reflector as well as the edge geometry ensures that the resulting collimated field is comprised of a pseudo transverse electric and magnetic (TEM) wave. Thus, by projecting an image of the feed at infinity, the CATR synthesizes the type of wave-front that would be incident on the antenna under test (AUT) if it were located very much further away from the feed than is actually the case with the coupling of the plane-wave into the aperture of the AUT creating the classical measured “far-field” radiation pattern. The accuracy of a pattern measured using a CATR is primarily determined by the phase and amplitude quality of the pseudo plane-wave with this being restricted by two main factors: amplitude taper (which is imposed by the pattern of the feed), and reflector edge diffraction, which usually manifests as a high spatial frequency ripple in the pseudo plane wave [2]. It has therefore become customary to specify CATR performance in terms of amplitude taper, and amplitude & phase ripple of this wave over a volume of space, termed the quiet-zone (QZ). Unfortunately, in most cases it is not directly apparent how a given QZ performance specification will manifest itself on the resulting antenna pattern measurement. However, with the advent of powerful digital computers and highly-accurate computational electromagnetic (CEM) models, it has now become possible to extend the CATR electromagnetic (EM) simulation to encompass the complete CATR AUT pattern measurement process thereby permitting quantifiable accuracies to be easily determined prior to actual measurement. As the accuracy of these models is paramount to both the design of the CATR and the subsequent determination of the uncertainty budget, this paper presents a quantitative accuracy evaluation of five different CEM simulations. We report results using methods of CATR modelling including: geometrical-optics with geometrical theory of diffraction [3], plane-wave spectrum [4], Kirchhoff-Huygens [4] and current element [3], before presenting results of their use in the antenna pattern measurement prediction for given CATR-AUT combinations. REFERENCES [1]C.G. Parini, S.F. Gregson, J. McCormick, D. Janse van Rensburg “Theory and Practice of Modern Antenna Range Measurements”, IET Press, 2014, ISBN 978-1-84919-560-7. [2]M. Philippakis, C.G. Parini, “Compact Antenna Range Performance Evaluation Uging Simulated Pattern Measurements”, IEE Proc. Microw. Antennas Propag., Vol. 143, No. 3, June 1996, pp. 200-206. [3]G.L. James, “Geometrical Theory of Diffraction for Electromagnetic Waves”, 3rd Edition, IET Press, 2007, ISBN 978-0-86341-062-8. [4]S.F. Gregson, J. McCormick, C.G. Parini, “Principles of Planar Near-Field Antenna Measurements”, IET Press, 2007.
Inter-comparisons of antenna test ranges serve the purpose of validating the measurement accuracy of a given range before it can be qualified to perform certain measurements, which is particularly important for space applications, where antenna specifications are very stringent. Moreover, by verifying the measurement procedures and identifying sources of errors and uncertainties, inter-comparison campaigns improve our understanding of strengths and limitations of different measurement techniques, which, in turn, leads to further improved measurement accuracies. The lesson learned from early comparison campaigns executed by the Technical University of Denmark (DTU) in early 80s on some readily available antennas says that proper inter-comparisons can only be done on dedicated antennas, whose design is driven by stringent requirements on their rigidity and mechanical stability. Furthermore, well-defined reference coordinate systems are essential. These principles have convincingly been proven valid by the VAST-12 antenna designed by DTU in late 80s, which in more than 20 years has demonstrated its usefulness and a long-term value. Currently, the satellite communication industry is actively commercializing the mm-wave frequency bands (K/Ka-bands) in its strive for wide frequency bandwidth and higher bit-rates. The next step is the exploration and exploitation of the Q/V-band. In this scenario, the European Space Agency (ESA) is expanding its portfolio of VAlidation STandard antennas (VAST) into mm-waves to ensure accurate measurements of the next generation communication antennas. This time, ESA demands all four bands (K/Ka/Q/V-bands) to be covered by a single VAST antenna. In this contribution, we report our efforts in designing, fabricating, and testing a new precision tool for antenna test range qualification and inter-comparisons at mm-waves -- the mm-VAST antenna. In particular, we present the details of the antenna mechanical design, fabrication and assembling procedures. The performance verification test plan as well as first measurement results will also be discussed.
The Space Communications and Navigation (SCAN) Testbed was a Software Defined Radio (SDR)-based payload launched to the International Space Station (ISS) in July of 2012. The purpose of the SCAN Testbed payload was to investigate the applicability of SDRs to NASA space missions in an operational space environment, which means that a proper model for system performance in said operational space environment is a necessary condition. The SCAN Testbed has line-of-sight connections to various ground stations with its S-Band Earth-facing Near-Earth Network Low Gain Antenna (NEN-LGA). Any previous efforts to characterize the NEN-LGA proved difficult, therefore, the NASA Glenn Research Center built its own S-Band ground station, which became operational in 2015, and has been successfully used to characterize the NEN-LGA’s in-situ pattern measurements. This methodology allows for a more realistic characterization of the antenna performance, where the pattern oscillation induced by the complex ISS ground plane, as well as shadowing effects due to ISS structural blockage are included into the final performance model. This paper describes the challenges of characterizing an antenna pattern in this environment. It will also discuss the data processing, present the final antenna pattern measurements and derived model, as well as discuss various lessons learned.
We present experimental results for on platform (in-situ) calibration of an antenna array with signals that are treated as signals of opportunity. In-situ calibration is required for antenna arrays installed on vehicles as platform scattering significantly perturbs the radiation patterns of the antenna elements. In-situ measurement of the array response requires: determining location of the unknown signals; determining the array’s response in the direction of the signals; and synthesizing the array pattern from the measured data. For this work, a seven element L-band antenna array was mounted on a generic aircraft platform. The platform was mounted on a dual rotator setup and emitters were placed nearby. The platform was then rotated while the emitters transmitted, and the signals received by the antenna elements were digitized. The collected data was then post processed to obtain the array calibration. We found that the calibrated array manifold enables more accurate direction of arrival estimation and provides additional gain in direction constrained beamforming. The present work serves as experimental verification of earlier simulation studies on in-situ array calibration.
Among the near-field – far-field (NF–FF) transformation techniques, the one employing the plane-polar scanning has attracted a considerable attention [1]. In this framework, efficient sampling representations over a plane from a nonredundant number of plane-polar samples, which stays finite also for an unbounded scanning plane, have been developed, by applying the nonredundant sampling representations of the EM fields [2] and assuming the antenna under test (AUT) as enclosed in an oblate ellipsoid [3] or in a double bowl [4], namely, a surface formed by two circular bowls with the same aperture diameter but eventually different lateral bends. These effective representations make possible to accurately recover the NF data required by the plane-rectangular NF–FF transformation [5] from a nonredundant number of NF data acquired through the plane-polar scanning. A remarkable reduction of the number of the needed NF data and, as a consequence, of the measurement time is so obtainable. However, due to an imprecise control of the positioning systems and their finite resolution, it may be impossible to exactly locate the probe at the points fixed by the sampling representation, even though their position can be accurately read by optical devices. Therefore, it is very important to develop an effective algorithm for an accurate and stable reconstruction of the NF data needed by the NF–FF transformation from the acquired irregularly spaced ones. A viable and convenient strategy [6] is to retrieve the uniform samples from the nonuniform ones and then reconstruct the required NF data via an accurate and stable optimal sampling interpolation (OSI) expansion. In this framework, two different approaches have been proposed. The former is based on an iterative technique, which converges only if there is a biunique correspondence associating at each uniform sampling point the nearest nonuniform one, and has been applied in [6] to the uniform samples reconstruction in the case of cylindrical and spherical surfaces. The latter, based on the singular value decomposition method, does not exhibit this constraint and has been applied to the nonredundant plane-polar [7] scanning technique based on the oblate ellipsoidal modelling. However, it can be conveniently used only when the uniform samples recovery can be split in two independent one-dimensional problems. The goal of this work is to develop these two techniques for compensating known probe positioning errors in the case of the nonredundant plane-polar scanning technique using the double bowl modelling [4]. Experimental tests will be performed at the UNISA Antenna Characterization Lab in order to assess their effectiveness. [1] Y. Rahmat-Samii, V. Galindo Israel, and R. Mittra, “A plane-polar approach for far-field construction from near-field measurements,” IEEE Trans. Antennas Prop., vol. AP-28, pp. 216-230, 1980. [2] O.M. Bucci, C. Gennarelli, C. Savarese, “Representation of electromagnetic fields over arbitrary surfaces by a finite and nonredundant number of samples,” IEEE Trans. Antennas Prop., vol. 46, pp. 351-359, 1998. [3] O.M. Bucci, F. D’Agostino, C. Gennarelli, G. Riccio, and C. Savarese, “NF–FF transformation with plane-polar scanning: ellipsoidal modelling of the antenna,” Automatika, vol. 41, pp. 159-164, 2000. [4] O.M. Bucci, C. Gennarelli, G. Riccio, and C. Savarese, “Near-field–far-field transformation from nonredundant plane-polar data: effective modellings of the source,” IEE Proc. Microw. Antennas Prop., vol. 145, pp. 33-38, 1998. [5] E.B. Joy, W.M. Leach, Jr., G. P. Rodrigue and D.T. Paris, “Application of probe-compensated near-field measurements,” IEEE Trans. Antennas Prop., vol. AP-26, pp. 379-389, May 1978. [6] O.M. Bucci, C. Gennarelli, G. Riccio, C. Savarese, “Electromagnetic fields interpolation from nonuniform samples over spherical and cylindrical surfaces,” IEE Proc. Microw. Antennas Prop., vol. 141, pp. 77-84, 1994. [7] F. Ferrara, C. Gennarelli, G. Riccio, C. Savarese, “Far field reconstruction from nonuniform plane-polar data: a SVD based approach,” Electromagnetics, vol. 23, pp. 417-429, July 2003
The source reconstruction or equivalents source method provides an accurate near-field representation of any radiating device in terms of equivalent electric and magnetic currents. The equivalent currents can be determined from measured near or far field data through a post-processing step involving the solution of an integral equation. The currents constitutes an accurate 3D electromagnetic model, maintaining near and far field properties of the measured device. A newly created link, enable the export of the model to a number of commercial computational electromagnetic (CEM) solvers in the form of a near-field Huygens box. Of special interest to the EMC community, equivalent current representation of measured devices are directly applicable in diagnostics/hot-spot finding and in the determination of radiated emission at any distance. The Huygens box, derived from measurements, is applicable in the simulation of emission in different scenarios when the device is in vicinity of different objects such as shielding, cables etc. This papers shows examples of diagnostics and emission analysis of a representative printed circuit board (PCB) based on commercially available near field measurement systems, post-processing and CEM tools.
Inverse Synthetic Aperture Radar (ISAR) measurements are used in this study to obtain images of full scale targets placed on a turntable. The images of the targets are extracted using compressed sensing methods. The extracted target images are edited and merged into measured Synthetic Aperture Radar (SAR) images. Airborne SAR field trials are complicated and expensive. This means that it is important to use the acquired data efficiently when areas with different background characteristics are imaged. One would also like to evaluate the signature of targets in these background scenes. Ideally, each target should then be measured for many orientations as well as illumination angles which would result in a large number of measurement cases. A more efficient solution is to use ground based ISAR measurements of the desired targets and then blend these images into the SAR scene. We propose a SAR blending method where a noise free image of the target is extracted from the RCS measurement by using the compressed sensing method Basis pursuit denoise (BPDN) and then solving for a model consisting of point scatterers. The target signature point scatterers are then merged into a point scatterer representation of the SAR background scene. The total point scatterer RCS is evaluated in the frequency-angle domain followed by using that RCS for back projection to form a seamless SAR image containing the target with the desired orientation and aspect angle. A geometrically correct shadow, constructed from a CAD-model of the target, is edited into the background. The process is completed by adding noise to the image consistent with the estimated SNR of the SAR-system. The method is demonstrated with turntable measurements of a full scale target, with and without camouflage, signature extraction and blending into a SAR background. We find that the method provides an efficient way of evaluating measured target signatures in measured backgrounds.
We have performed spherical and extrapolation scans of two antennas at 118 GHz using a commercial 6-axis robot. Unlike spherical scanning, linear extrapolations do not precisely conform to the natural circular movement about individual robot axes. To characterize the quality of the data, we performed dynamic position and orientation characterization of the robotic systems. A laser tracker is used to measure the probe antenna movement relative to the antenna under test, this information is used to continually update the position and posture of the probe during scanning. We correlated the laser tracker data with the mmWave insertion phase to validate dynamic measurement position results at speeds up to 11 mm/s. We previously demonstrated spherical measurements with this system. The extrapolation measurements presented here require more stringent accuracies for pointing that general pattern analysis
In this paper, a patch antenna has been designed based on the complementary split ring resonator (CSRRs), complementary rose curve resonators (CRCRs) and without using these inclusions. Complementary rose curve resonators (CRCRs) are used in design of patch antenna. The Patch antenna based on the complementary rose curve resonators (CRCRs) are achieved by patterning the ground plane under the conductor trace. The perimeter of the Rose curve can be adjusted by tuning the amplitude of the sine function and the radius of the base circle. With the order of CRCRs, the loading effect of the complementary resonators on the patch antenna is controlled. This works demonstrated that higher order CRCRs allows more compactness of the design and higher miniaturization factor. We proposed a compact patch antenna based on the complementary split ring resonator (CSRRs) and the complementary Rose curve resonator (CRCRs). The proposed patch antenna shows good performances which is designed to operate at 2.4 GHz. The results demonstrate the configurability of the design for a specific size. The results show the effectiveness of using metamaterials in microwave circuit can obtain from n to n+1 of the CRCRs order will result in 0.3 % miniaturization. IndexTerms: Patch Antenna, Metamaterial, Size Reduction, split ring Resonators, Rose Curve Resonators
In this paper, we propose a calibration method for monostatic radar cross section (RCS) of simple radar targets (e.g. trihedral corner reflectors and square flat-plate reflectors) using extrapolation method. By the proposed method, we can calibrate the monostatic RCS of radar targets from 1-port S-parameter measurements. In our system, the applicable size of radar targets are 75 mm to 125 mm for corner reflectors and 40 mm to 75 mm for square flat-plate reflectors, respectively. The nominal RCS of reflector targets calculated by physical optics ranges from +3 dBsm to +15 dBsm in W-band. The measured results are agree well with simulation results calculated by method of moment (MoM).