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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.
Antennas fully integrated in radar systems or even on the chip packages cannot be measured with a conventional antenna measurement system as there is no access to the antenna feed point. The two-way radiation pattern of a frequency modulated continuous wave (FMCW) radar system can be measured using the transmit and receive module of the radar itself while measuring against a reflector. Still, the measurement uncertainty differentiates from conventional antenna measurements, and detailed studies are missing. The uncertainty factors introduced by the mechanical system and the reflectors themselves like the size of the reflector and the mechanical misalignment of the reflector and antenna under test (AUT) are investigated within this study on the basis of simulations. As reference antenna the simulation model of a scalar feed horn antenna and a plate, a dihedral and a trihedral reflector are used. The results show an overall stable behavior and a low error for the evaluated mechanical misalignments.
First realizations of reconfigurable intelligent surfaces (RIS) are becoming available as research on 6G advances. Consequently, prototypes have to be characterized by means of radiation pattern measurements to confirm the design properties. The main challenges here are the degrees of freedom from independent receiver and transmitter location in combination with surface configurations. We propose a far-field to nearfield measurement setup to conduct first full-sphere CATR measurements of a 5 GHz RIS at RWTH Aachen University. In order to cope with parasitic effects of the near-field probe, applicable post-processing methods including time gating and reconstructed equivalent currents are applied and evaluted.
In this paper, we thoroughly test and validate the complete active signaling measurement setup using a Plane Wave Generator (PWG), Radio Communication Tester (RCT), and a well-known antenna standard. The results of our study demonstrate excellent agreement between the Equivalent Isotropic Radiated Power (EIRP) measurements obtained using the active setup with the PWG, and those obtained using a passive measurement system employing the multiple probe spherical near-field technique. Furthermore, the Total Radiated Power (TRP) values derived from the active setup with the PWG are within expected uncertainty to the measured conducted power at the Horn input port. The measurements are done at 28GHz. The measured TRP using active OTA and conducted measurements are within 0.31 dB (6.9%) difference. This robust comparison illustrates the reliability and confidence in utilizing the PWG-based active measurement system.
We propose a compact bistatic radar cross section (RCS) measurement system using a new 2D plane-wave synthesis (PWS) employing 2D propagating plane-wave expansion and a single-cut near-field far-field transformation (SCNFFFT). Our system has been successfully applied to the bistatic RCS measurements of a metasurface (100 mm width, 50 mm height, and 0.127 mm thickness) at 60 GHz where two horn antennas are used for the PWS (Tx) and the SCNFFFT (Rx) and placed at the circular distances of 1.735 m and 0.35 m respectively. The peak and pattern errors of the RCS are 0.4 dB and below -25 dB respectively. Using the proposed 2D PWS and SCNFFFT, the compact 2D bistatic RCS measurement system is realized without large equipment such as CATR.
Challenges and limitations of off-normal reflectivity measurements of microwave anechoic chambers are presented. The NRL-Arch technique has been investigated for measurement of WAVASORB® VHP-26 for extreme incident angles; e. g. 80° for the frequency range of 1-20 GHz. It has been shown that the standard test techniques such as NRL-Arch have limitations and for extreme incident angles, simulation values are more reliable in most of the cases. In some rare cases some advanced techniques are available in the literature which are expensive and can be recommended for special projects only
The application of multi-probe (MP) technology in near-field (NF) measurement scenarios is well-known for its ability to significantly reduce test time. This is achieved by electronically sampling the radiated field using different probes in the array, eliminating the need for mechanical probe movement. However, in planar near-field (PNF) measurements, the accuracy is contingent on probe correction (PC) during post-processing. Characterizing the pattern of each individual sensor in a PNF MP system presents an additional challenge, often being impractical or impossible. Previous publications have explored various approaches to address this challenge and achieve an accurate characterization of the MP equivalent pattern. In this paper, we focus on the average probe pattern (APP) technique, which involves the experimental determination of the MP pattern. To validate the effectiveness of the APP technique, we conducted experiments on a large PNF MP system equipped with a 4.65m probe array. Our measurements focused on an electrically large 1.5m diameter reflector antenna (MVG SR150 reflector, fed by a quad-ridge horn) operating in the 1.8–6.0 GHz frequency range. The validation process involved the comparison of MP measurements processed with the APP technique and conventional open-ended waveguide (OEW) PNF measurements. To ensure the reliability of the validation, we conducted the comparative tests within the same frequency range and test setup. This minimized the impact of measurement errors, enabling a robust and accurate comparison between the techniques. By validating the APP technique's effectiveness, we aim to establish its suitability for improving accuracy in PNF MP system measurements.
This paper aims to compare the capabilities and advantages of Plane Wave Generators (PWG) and Compact Antenna Test Ranges (CATR) of similar physical size, operating in the VHF/UHF frequency range. The primary focus of this study is on the benefits of utilizing the PWG at such low frequencies for antenna and device characterization. We demonstrate that the PWG offers a superior approximation to the far-field (FF) plane wave condition in the quiet zone (QZ) compared to similar sized CATR systems. The better performance of the PWG at these frequencies is expected, as this is an unusual frequency range for an optical system such as CATR. Due to the efficient focusing properties of the array, the PWG exhibits significantly reduced side wall illumination and thus resulting reflections within the anechoic chamber. This translates into a substantial improvement in overall measurement uncertainty. The CATR system requires specific edge treatment, such as serrations or rolled edges, which increase the overall system's size and associated cost while reducing the effective area of the reflector. Our findings suggest that at low frequencies such as VHF/UHF, a PWG-based solution can be designed to comparable performance to the CATR system while maintaining a considerably smaller size and lower cost, making it an attractive alternative for low frequency antenna testing at in anechoic environments.
This paper provides an overview of measurement uncertainties associated with a planar near-field test methodology for measuring typical system level characteristics of transceiver payloads. We describe a framework for analyzing the uncertainties when measuring these system level RF parameters in a near-field range. More specifically, saturating flux density (SFD), equivalent isotropic radiated power (EIRP), gain-to-noise temperature (G/T) and end-to-end gain vs. frequency are addressed. Results from a set of validation measurements, performed on a frequency converting simulated payload are used as baseline. A combination of analysis and direct measurements are presented to validate the measurement methodology for each parameter and estimate corresponding uncertainties. The contribution of this paper is the presentation of these methodologies and establishing an initial set of uncertainty boundaries to qualify the near-field test approach for this purpose.
In this contribution a simple algebraic approach is discussed on the minimum of required sample points for either a nearfield or a farfield configuration to calculate the antenna’s current distributions to accurately reconstruct the antenna’s radiation pattern anywhere in space. The proposed algebraic approach comprises a Gaussian quadrature sampling scheme for a set of Hertzian dipoles with unkown amplitudes representing the antenna current distribution. The algebraic equation system with the number of unknown amplitudes then suggests the minimum of required sample points in the radiated field. In this initial study simulation examples of a dipole antenna and a horn antenna are presented validating the proposed algorithm.
Additive manufacturing methods, also known as 3D printing, have proven to offer many advantages in manufacturing a wide range of products. These methods have advantages of rapid prototyping, rapid production, and the ability to produce mechanical parts that cannot be realized with traditional machining or casting methods. Various methods have been developed which use a wide variety of raw materials and methods. For example, the Selective Laser Sintering (SLS) method has been used in 3D printing of antennas [1], where metal conductivity is required along with accurate mechanical tolerancing. Other methods using plastic such as stereolithography (SLA) where a liquid photopolymer resin is cured using an ultraviolet laser and Fused Deposit Modeling (FDM) material extrusion where a plastic wire is melted and deposited layer by layer to construct the part are being used to produce RF components and antennas. In the case of plastics, a conductive layer must be deposited onto the plastic to ensure conductivity. Recent work toward the development of horn antennas produced using SLS, SLA and extrusion methods has been accomplished. The methods have been shown to produce horn antennas capable of meeting a variety of applications in the test and measurement industry where accuracy and repeatability are key metrics. A comparison of methods is presented along with advantages and disadvantages. Performance data will be presented for some horns showing the capabilities of the various methods.
Vehicular wireless power transfer (WPT) systems conforming to the SAE J2954 standard are thought to operate as inductive WPT systems. As such, they should be able to be accurately represented by a magnetic multipole source. For example, the magnetic field of the “circular” coupler, which is described in the SAE standard, can be represented by a combination of a vertical, linear magnetic quadrupole and a horizontal magnetic dipole. However, it has been recently shown that a significant conservative electric field exists in such a WPT system due to the multi-turn windings. This can lead to a significant electric multipole contribution, predominantly a vertical linear electric quadrupole for the circular coupler. In fact, the circular coupler electric field (not the magnetic field) is somewhat similar to that of a coaxial aperture. Here, we carry out a detailed analysis of the electric multipole representation of the “DD” coupler which is also described in the SAE standard. The analysis of the electric multipole of the DD coupler is more complex than that of the circular coupler. Because the DD coupler is composed of two side-by-side spiral windings, it is possible to obtain two different electric multipoles from configurations that produce nominally the same magnetic multipole and the same magnetic performance. Fortuitously, the configuration used in the DD coupler very nearly cancels the conservative electric field, the associated electric multipole, and the attendant emissions.
We have newly developed an optical fiber link millimeter wave band vector measurement system. The system consists of an optical fiber link millimeter wave transmission system, an optical fiber link millimeter wave receiving system, and the IF substitution method configuration using a lock-in amplifier (without a vector network analyzer). In this paper, we show the developed millimeter wave measurement system configuration and the millimeter wave measurement performance using the IF frequency measurement results.
This paper explores the impact of varying infill densities for various infill patterns on the effective relative permittivity of 3D printed waveguide slabs. Previous studies have highlighted the substantial influence of infill patterns on the relative permittivity of substrates. The study aims to investigate the disparities in effective relative permittivity when diverse infill patterns are employed at various infill densities for multiple antenna substrates printed with identical parameters. Furthermore, this study examines the relationship between effective permittivities and infill densities for various infill patterns to identify suitable patterns for accurately estimating permittivity at lower densities. To accomplish this objective, dielectric slabs were 3D printed with a range of infill patterns and densities while maintaining consistent manufacturing parameters. The relationship between infill density and effective permittivity was analyzed for samples without the use of solid layers. The results revealed a linear behavior when solid layers were omitted during manufacturing. These findings underscore the critical role of infill pattern selection in determining material density and permittivity for antenna design and related applications.
Consolidated methodologies have long been established to assess measurement uncertainties in near-field antenna measurements. More recently, similar detailed approaches have been developed for compact ranges and adopted as standard practice. However, currently there is no analogous methodology for outdoor far field measurement facilities. This paper presents a framework for assessing the measurement uncertainties on an outdoor far-field elevated range. Various sources of uncertainty in an outdoor far-field range are identified, using the industry standard 18 term analysis for nearfield range assessment as a baseline. An example analysis based on an actual outdoor far-field range is presented. The uncertainty terms are quantified by analysis, observation, or measurement, and finally combined by the root sum squared method to arrive at the gain uncertainty and the -30 dB sidelobe level uncertainty.
This paper presents the design of an ultrawideband (UWB) open-boundary dual-polarized quad-ridged horn antenna (QRHA) having an impressive 3-decades bandwidth from 1 to 32 GHz, making it an ideal choice for a wide range of applications in radars and communication systems. Its unprecedented bandwidth performance in a single and compact antenna geometry covers various frequency bands including L, S, C, X, Ku, and K. The ridge tapering profile of the proposed QRHA ensures excellent impedance matching, while the aperture matching prevents any phase distortion. The back-cavity design as well as cavity flaring is carefully optimized to achieve wideband performance along with no presence of pattern degradation specifically at the higher end of the frequency band. The antenna design exhibits a favorable impedance matching below -10 dB, well-matched copolar antenna patterns in the principal planes, and good crosspolarization (exceeding -20 dB) over a 3-decades bandwidth.
This paper discusses the novel development of a lightweight RF front-end system aimed at enhancing airborne antenna measurements in the far-field. The proposed system leverages advancements in software-defined radio (SDR) technology and high-performance RF front-end systems. While there are instances of SDR applications in UAS measurements, these systems are predominantly designed for anti-UAS and communication purposes, lacking focus on antenna and radar characterization. In contrast, the proposed system is purposefully tailored for RF applications, completely self-contained and airborne, possessing both RX and TX capabilities, and minimizing reliance on ground-based components. The system facilitates transmission and reception in both H- and V-polarization, employing two independent channels. Consequently, it allows for the simultaneous measurement of antenna or radar properties in both copolar (Cp) and cross-polar (Xp) orientations. The comparison between antenna measurements conducted within an anechoic chamber and those carried out utilizing the proposed UAS system demonstrates a substantial level of agreement.
This paper discusses the novel development of a lightweight RF front-end system aimed at enhancing airborne antenna measurements in the far-field. The proposed system leverages advancements in software-defined radio (SDR) technology and high-performance RF front-end systems. While there are instances of SDR applications in UAS measurements, these systems are predominantly designed for anti-UAS and communication purposes, lacking focus on antenna and radar characterization. In contrast, the proposed system is purposefully tailored for RF applications, completely self-contained and airborne, possessing both RX and TX capabilities, and minimizing reliance on ground-based components. The system facilitates transmission and reception in both H- and V-polarization, employing two independent channels. Consequently, it allows for the simultaneous measurement of antenna or radar properties in both copolar (Cp) and cross-polar (Xp) orientations. The comparison between antenna measurements conducted within an anechoic chamber and those carried out utilizing the proposed UAS system demonstrates a substantial level of agreement.
Compact Ranges are widely used for antenna measurements across wide frequency ranges spanning frequencies as low as 350MHz to as high as 60GHz and above. Advances in electromagnetic (EM) simulations have significantly improved the design process for compact ranges, resulting in reduced costs. Characterizing compact range including the anechoic chamber is computationally very challenging in terms of computer memory and time. In this paper, we will present the full wave method, MLFMM for characterizing compact range without the chamber and application of asymptotic method, RL-GO to characterize the compact range inside the anechoic chamber.
This paper addresses the circularly-polarized (CP) gain uncertainty when using linearly-polarized feeds to obtain circular polarization in Compact Antenna Test Ranges. In particular, our emphasis is placed on quantifying the inaccuracy caused by deviations in amplitude and in phase of the two orthogonal linear measurements. This is of paramount importance especially for highly directive CP antennas operating at high frequencies in that the CP gain will be adversely impacted even by a small deviation from an ideal 90- degree rotation, as well as by a situation when the rotation may cause a slight boresight misalignment. To characterize the gain uncertainty, we look at ratio differences between the peak amplitude of the linear measurements, as well as cases when the phase shift of the two orthogonal linear measurements is no longer 90 degrees. The former is done through mechanical and electrical boresighting technique in the initial setting. The latter, which is the focus of this paper, is carried out through several case studies in practice mimicking some non-ideal 90- degree rotation settings.