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Recently, due to rapid technological changes and the global economic system, conformity assessment for products has become international issue. Major countries have established and implemented standardization and management systems for electrical, electronic, and communication devices, including broadcasting and communication equipment, and manufacturers and consumers who use products and parts demand guarantees that they meet international regulations and required global standards. The Korea Radio Research Agency(RRA)'s Communications Conformity Assessment Center(CCAC) has been conducting performance tests on radio wave test antennas owned by domestic test agencies, but since December 2019, the Korea Accreditation Organization (KOLAS) calibration report issued by the domestic antenna calibration agency has been recognized as a performance test report, and indirect management has been carried out by document inspection of the measured value of the antenna for conformity assessment. Accordingly, a proficient test of antenna performance between the CCAC and the antenna accreditation calibration agencies is promoted to get the measurement reliability of the antenna for radio wave test owned by the designated test agency and maintain the same performance test. The test materials for the proficiency test were sequentially tested by four accreditation calibration agencies for three years using several standard antennas mainly used to measure electromagnetic wavelength, resistance and emission characteristics, and field strength characteristics. The En-Score method, an international standard statistical method used to evaluate proficiency test in the calibration field, was applied to the measurement results between the CCAC and antenna accreditation calibration agencies, and it was determined to be meet in all bands of antenna characteristics. Proficiency test promotes the improvement of test capabilities by verifying and correcting the own test capabilities of designated testing agencies through the development and application of test samples. In this paper, we would like to conduct a proficiency test and analyze the identity of the performance test for indirect management of the antenna performance for the conformity assessment.
The Low-temperature Near-field Terahertz Chamber (LORENTZ) is a novel facility recently installed and commissioned at ESTEC, ESA. This facility has the unique ability to characterize the antenna performance off full submillimeter instruments in operational environments down to 80k. We provide an overview on the various design and commissioning steps that were required to ensure all parts of the test facility would operate reliability in such challenging conditions. We also present how the facility performed during the first full measurement run of flight hardware and a roadmap for future developments.
As 5G mobile services keep pursuing higher speeds of data transmission based on the use of mm-Waves, they run across problems. The strength of the mm-Wave signal becomes weak very rapidly as the receiver moves away from the transmitter. To overcome the shortcoming, the antenna takes the form of an array of a large size and is fed by amplifiers along the branches of the power divider. It ends up with growth in size and cost. Metamaterials such as transmitarrays have been proposed to increase the antenna gain avoiding the conventional feed circuitry. A metasurface can play a role of the planar lens which is positioned over the primary source. It leads to enhanced antenna gain and reduction in cost and loss. The antenna performances of the metasurface working for 5G and 6G wireless communication are characterized by measuring the radiated field patterns based on the near-to-far field test method and compact range chamber setup (CATR). The measurements present the results of the two methods are in good agreement and the gain improvement.
This paper presents fully 3D printed patch antennas with varying infill densities. Both the substrate, as well as the metallic layer of these antennas, were manufactured using additive methods. We have used the linear approximation method derived from our previous study to estimate the effective relative permittivity values for lower infill densities for these antenna substrates and tested the validity of that approximation with these 3D printed antennas. Additionally, we demonstrated a parameter optimization technique to accommodate the changing infill densities, ensuring that antennas with lower infill density substrates can still function within the desired frequency range. The measured results were compared to the simulated data, and the influence of solid layers on the substrate was investigated. The study validates the linear approximation method and highlights the potential of 3D printing in antenna design, offering researchers greater flexibility and control over custom antenna development for specific applications.
Measuring the radiation behavior of antennas in an anechoic environment with far-field (FF) conditions requires large measurement sites resulting in high costs. To overcome this problem, near-field (NF) measurement techniques and nearfield to far-field (NFFF) transformation are used to derive the FF of an antenna under test. Thus, evaluating the accuracy and reliability of the NFFF transformation is highly important. The first step for this evaluation process is creating a valid and accurate reference data library consisting of NF and FF data. NF data is used as input to the NFFF transformation, whereas FF data is used as a reference for comparison to the FF obtained after the transformation. This paper explores analytical studies for different antenna models, namely a pyramidal horn antenna and an open-ended waveguide. Simulations of the models are carried out in a commercial full-wave electromagnetic software, considering the various input parameters influencing the FF results. The NF and FF data from the parameterized simulation model is used to evaluate the NFFF transformation methods. After optimization of the simulation parameters, the required accuracy levels of −30 dB and −40 dB for two different accuracy metrics defined throughout the paper are achieved.
Recent advancements in 3D printing technology have enabled the creation of more precise and accurate antennas, allowing for more complex and innovative designs. With the use of new printers and materials, the cost of producing prototype and customized antennas for specific frequency bands has also decreased. Additionally, 3D printing allows for the creation of single-unit devices to replace traditionally multi-part devices. However, challenges still exist, such as the permittivity of printable materials and the surface roughness of the final prints. In this study, standard gain horns and coaxial adapters were printed and coated to explore these challenges. The gain of the resulting horns has been estimated and compared to derive the performance of different printing materials.
In the past few years, the working group (WG) on antenna measurements, being part of the European antenna and propagation association (EurAAP), has spent a great deal of effort in carrying out a whole range of antenna measurement related activities and projects. These activities cover various areas of antenna measurements and are sub-divided into different tasks, such as measurements and comparisons of reference antennas, revisions of IEEE antenna measurement standards, self-assessment measurements of facilities, and emerging techniques for antenna over-the-air (OTA) measurements. This paper gives an update of the status of these activities carried out by the EurAAP WG on antenna measurements including the initial of a new campaign based for a first time on a low directive antenna, an MVG SMC2200 monocone antenna on a circular ground plane. Moreover, the new activities in collaboration with the EurAAP WG on software and modeling tools will be presented with the aim of promoting the benefits of the synergy between measurement and simulation modeling tools.
In 6G wireless communication systems, the use of array antennas and metamaterial reflectors above 100 GHz is being considered to expand the communication area, and there is an urgent need to establish a high-precision evaluation system for array antennas and metamaterial reflectors, which are key components for 6G wireless systems. To meet these demands, we have developed a compact antenna test range (CATR) system using offset Gregorian antennas, which consists of a parabolic mirror and an ellipsoidal mirror, to evaluate the radiation patterns of antennas and RCS patterns of metamaterial reflectors in the 100 GHz to 300 GHz band. The double-mirror configuration has the advantage of shortening the distance between the parabola and the antenna to be evaluated, since a long focal length can be achieved in a small space. In this presentation, we report on the performance of the developed offset Gregorian compact range system and the evaluation results of the antenna and reflector. So far, we have succeeded in generating a uniform plane wave at a distance of about 1 m from the parabolic surface in an area including a circle with a radius of 400 mm. The amplitude difference is less than 0.7 dB compared to the antenna radiation pattern measured by the planer near-field measurement system. The amplitude uniformity and phase variation of the generated plane wave are reported.
Absorber fences have been used on compact ranges since their first implementations. The purpose of this fence is to hide the feed positioner and reduce the direct coupling between the feed and the device under test (DUT). A known problem caused by such a fence is that it diffracts the plane wave generated by the reflector, creating an interfering ripple on the illumination of the DUT in the quiet zone. Traditionally, fences have serrated edges to direct this diffracted signal away from the quiet zone. However, this redirection is not always achievable or even repeatable from one facility to the next. Often low frequency requirements drive absorber physical size, leading to very large absorbing surfaces that cannot be optimized to reduce this interfering signal. In this paper, the fence design presented in a recent publication [1] is further optimized by modifying its shape and absorbing material parameters. The performance of this new design is compared with traditional fences.
The Naval Surface Warfare Center Indian Head Division (NSWC IHD) EOD Technology Center is a United States Navy facility with the urgent mission of supporting the Department of Defense (DoD) warfighter in the detection and neutralization of unexploded ordnance (UXO) and improvised explosive device (IED) threats. The Radio Frequency (RF) Laboratory at NSWC IHD, is centered around its 24’ by 12’ by 12’ anechoic chamber, which was designed mainly for antenna measurement. However, the unique challenges this department was tasked to resolve has resulted in varied and uncommon uses of the chamber. The chamber, RF test equipment and staff of electrical engineers, mechanical engineers and computer scientists, have participated in the automated RF testing of X-ray equipment, bomb suits, radars, electronic jammers and IEDs, to provide just a partial listing of test events. This paper will detail recent unique assignments that required the rapid research, design, development and implementation of automated RF test and measurement systems providing solutions for the EOD community. The anechoic chamber’s system uses, from antenna design and measurements, materials testing, electromagnetic compatibility (EMC) testing to electronic warfare (EW) testing of radars and jammers, will be discussed along with the examination of the software algorithms that enabled fast, repeatable and reliable RF measurements. Focus will be on the roles electromagnetic (EM) measurement has for EOD robotics, EW system development and IED threat understanding. The authors speak from the diverse backgrounds of electrical and mechanical engineering and computer science.
The IEEE Std 1720™, "Recommended Practice for Near-Field Antenna Measurements," serves as a dedicated guideline for conducting near-field (NF) antenna measurements [1]. It serves as a valuable companion to IEEE Std 149-2021™, "IEEE Recommended Practice for Antenna Measurements," which outlines general procedures for antenna measurements [2]. IEEE Std 1720 was originally approved in 2012 as a completely new standard by the IEEE Standards Association Standards Board. It holds significant importance for users engaged in NF antenna measurements and contributes to the design and evaluation of NF antenna measurement facilities. With its tenyear term coming to an end in 2022, the standard will no longer remain active. Nonetheless, a "minor revision" of the existing standard is in progress and is expected to be completed in 2023. The objective of this paper is to provide insights into the ongoing activities surrounding the revision and to explore the proposed changes. It aims to facilitate a discussion on the modifications to and their implications for modern NF antenna measurements.
The spherical wave expansion-based transmission formula allows to accurately evaluate the coupling (or S21 parameter) between a transmitting and a receiving antenna. Its use as tool for probe corrected spherical near-field to far-field transformation is well accepted and documented. On the other hand, its direct use in the evaluation of antenna measurement performance has been exploited only in recent years. In this paper we will show how measurement performances predicted with the transmission formula compare with actual measurements. Taking as examples relatively complex antenna measurement systems like spherical near-field, plane wave generators and CATR, we will focus on the prediction of the accuracy of the measured radiation patterns, also including the approximation of reflections from the test environments, and on the evaluation of link budgets.
Spherical Near Field (SNF) measurement systems are
primarily limited in usable bandwidth by the probe frequency
coverage. This limitation mainly arises from the presence of
higher-order azimuthal modes in the probe pattern [1]. In case of
electrically large or offset AUTs, such a limitation may be
overcome by a full probe correction algorithm for the NF/FF
transformation [2]. However, probes approximating first order
performance over the full bandwidth are generally preferred.
Traditionally, first-order probes based on geometrically
symmetric Ortho-Mode Junctions (OMJ) with externally
balanced feeding have been widely accepted. These probe designs
rely on couplers that provide equal amplitude and opposite phase
distribution at their output ports [3]. In this paper, the design
and validation of a novel 3dB/180° coupler is presented. The
concept is based on the natural anti-symmetric properties of the
electric field within the component, providing a quasi-perfect
amplitude and opposite phase distribution. To achieve these
properties, an architecture based on slot coupling is selected. The
design has been implemented in several frequency bands, from
UHF to Ku-band, as stand-alone cased components.
Experimental data at L/S-band is presented in this paper,
showing excellent performance in terms of matching, balance,
and isolation between output ports, well in-line with full-wave
electromagnetic predictions. In addition, the impact of the
coupler accuracy is also assessed on a relevant SNF test case.
A new compact range for RCS measurements has been installed and qualified by Orbit/FR Engineering Ltd. MVG. It has a Quiet Zone of 3m diameter, 3m length and operates from 0.7 to 50 GHz, with a feed carousel that allows for fully automated feed change. The RF design is not intended for antenna measurements in its current configuration, but mainly dedicated to RCS. The operational frequency band is split into three sub-bands: each of the lower two bands have a monostatic operated dual polarized feed, while the higher band has a quasimonostatic operated feed configuration with two dual polarized feeds. Pulsed Tx/Rx modules are directly integrated into the feed assembly. Also, the RF band switching equipment, as well as the network analyzer, are integrated in the feed carousel, so that there are no flexing cables or any other relative movement of RF components when the relevant feed is moved into the focus. Together with tight temperature control, this leads to the best possible RF stability. Since all measurements are time gated, there is no need for an absorber baffle wall to prevent feed direct leakage into the quiet zone. Thus, all feeds are mounted on a clean absorber disk without any absorber blockage and unwanted primary pattern distortion down to a conical angle of 90deg. This allows to obtain an exceptionally good QZ performance even at the lowest frequencies, with an outstanding comparison with the predictions based on Physical Optics. The paper will describe the range design fundamentals, the feed carousel concept and the relevant RF instrumentation. The Quiet Zone performance evaluated by field probing with a Shorted Antenna located in the Quiet Zone will be extensively presented, demonstrating full compliance with the specifications.
A new compact range for RCS measurements has been qualified. It has a quiet zone of 3m diameter, 3m length and operates from 0.7 to 50 GHz. The range is oriented for RCS measurements, whereas antenna measurements are not foreseen. All RF equipment is integrated close to the feeds with highly integrated pulsed Tx/Rx-modules. Therefore, classical field probing by moving a probe antenna along a linear slide would require significant modification of the RF system. If one measures the RCS of a target on the linear slide, it is difficult to distinguish the target down range reflection from the reflection of the linear slide structure. A long stand-off between target and slide is not practical for mechanical reasons in regard to accuracy requirements at 50 GHz. More important, simply measuring a reflective plate will not give any cross-polarization information. A more advanced target is created by using an antenna with a short circuit after an RF cable to locate the reflection of the short well behind the scanner in down range. In addition, the antenna receives only nominal quiet zone co-polarization, consequently, only reflects co-polarization from the short, and the feed receives the compact range induced cross-polarization at the feed (oneway). The method has shown to be extremely effective. More important, it uses the RF instrumentation and RCS measurement methods as designed for regular operation without any modification, thus is the most realistic system level quality representation of the quiet zone, can be repeated at any time without elaborate range reconfiguration requirements and can serve as part of the commissioned RF system performance qualification. The paper will present the quiet zone field probe test setup, a calculation of antenna and RF cable requirements, an analysis of the down range profile of scanner and reflective antenna and field probing results.
This communication provides an effective two-steps strategy to compensate for known 3-D probe positioning errors occurring in the non-redundant (NR) cylindrical near-to-far-field (NTFF) transformations. As first step, a phase correction, here denoted as cylindrical wave correction, is employed to perform the correction of the positioning errors relevant to the deviations of the measured NF samples from the nominal scanning cylinder. Then, an iterative procedure will be applied to retrieve the NF samples at the points specified by the adopted sampling representation from those obtained at the previous step and affected by 2-D positioning errors. Finally, after properly reconstructing the correctly distributed cylindrical samples, the data necessary to apply the classical cylindrical NTFF transformation can be restored in accurate way by employing a 2-D optimal sampling interpolation (OSI) formula. It should be noticed as, to derive the NR sampling representation, as well as the OSI scheme, it is necessary to provide a proper modeling of the antenna under test. This modeling has been got by shaping the source with a prolate spheroid. Numerical tests will show the capability of the procedure to compensate these 3-D positioning errors.
This work aims to propose and optimise a non-redundant spherical spiral near-to-far field (NTFF) transformation for elongated AUTs from spiral near-field (NF) data acquired over the upper hemisphere due to the presence of an infinite perfectly electric conducting (PEC) ground plane. Such a technique properly exploits the principle of image and the theoretical foundations of spiral scan for non-volumetric AUTs to develop the non-redundant representation along the sampling spiral in presence of PEC ground plane and to synthesise the voltage NF data which would be acquired over the spiral wrapping the lower hemisphere. Once these voltage NF data have been synthesised, then an efficient 2-D optimal sampling interpolation scheme allows the recovering of the NF data required by the classical NTFF transformation. In the hypothesis that the AUT and its image exhibit a predominant dimension as compared to the other two ones, a prolate spheroidal source modeling is here adopted. Numerical tests show the accuracy of the developed non-redundant spherical spiral NTFF transformation.
Demand for broadband connectivity in moving platforms on land, sea, and air has opened the mass market for low-cost mobile ground-station terminals that employ electrically steerable antennas. The antennas of these terminal units need to be tested in a production line environment. Planar near-field scanning is considered as a convenient measurement method, but the time needed for conventional scanning may be prohibitive. In this paper, the design of a multiprobe planar near-field scanner for rapid antenna testing at Ku-band is presented. A probe array is moved along a spiral path to avoid large accelerations and decelerations of the probe array, and the near-field sampling is done simultaneously with multiple of respective receivers. Thus, the data acquisition time is significantly reduced compared to the single probe or receiver measurement. A preliminary antenna testsystem design for the mobile ground-station terminal antennas operating at Ku-band is presented. The numerical results for simple representative antenna models suggest good performance of the system.
—Cylindrical hubs with fan blades are inserted into a pipe inside a modified camera box—a recently introduced structure intended to host differently-shaped ducts behind an aperture. The resulting structures increase the reproducibility of commonly used simplified jet-engine inlet models and are designed to serve as precisely-defined radar cross section (RCS) benchmarks with reliable reference results. The design, manufacturing, and assembly of the measured structures are detailed; the RCS measurement setup, data collection, and post processing are documented; and the uncertainty in measured RCS data is quantified with the help of simulations. Results show that the fields scattered by the structures, while highly sensitive to geometric and material perturbations, can be both measured and simulated accurately even at frequencies with many propagating modes inside the pipe.
A prototype of a previously presented design of a microwave oil/water ratio measurement system for geological applications was built and tested in a commercial flow loop. The prototype used a vector network analyzer to measure the reflection (S11) and transmission (S21) coefficients of the fluids under test. The fluids tested had different compositions of dearomatized oil, low salinity water and methane. This paper presents results from the flow loop evaluation of the present oilbrine- ratio (OBR) meter prototype. Transmission and reflection spectrums were obtained for different oil, water, and methane combinations. Transmission data shows good sensitivity and accuracy for most water volume fractions (WVF) below 70%. Transmission in WVF above 70% could be inverted by using a different frequency band and results could also be combined with S11 data to improve accuracy. In addition, the effect of gas volume fraction (GVF) above 50% is seen as a significant increase in transmission, for high WVF, relative to the de-gassed case. In the case of WVF less than 45%, the effect of gas can be measured by a shift in the cut-off frequency. Thus, the measuring system could also be used for gas kick detection.