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Emerging wireless technologies with Gbps connectivity, such as the 5th generation (5G) and 6th generation (6G) of mobile networks, require improved and substantiating documentation for the wireless standards concerning the radio signals, systems, transmission environments used, and the radio frequency exposures created. Current challenges faced by the telecommunications sector include the lack of accurate, fast, lowcost, and traceable methods for manufacturers to demonstrate 5G/6G product verifications matching customers’ specifications. This paper gives an update on the recent research and development activities from an EU Joint Research Project entitled “metrology for emerging wireless standards” (MEWS) in support of the above.
The reflectivity of foam absorber materials is governed by the correct loading and mixture of carbon and other supplicants such as fire retardants. In order to assess the reflectivity of the absorbers various measurement setups are applied, each having different advantages and disadvantages in terms of frequency coverage and RF performance. The measurement setups are used both in the quality control (QC) as well as for product development. Especially for the product development case, it is important to understand limits of these setups as the lower the reflectivity gets, the more difficult it becomes to detect minute differences between different variants of the absorbers. For reflectivity measurements of microwave absorbers, the available dynamic range and calibration-quality of the setup plays a vital role in this respect. By determining the uncertainty of the measurement setups, a clear assessment can be made to the quality of the measurement and the product to insure consistent QC, as well as plan for the product development.
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.
There are several applications that require the Fourier transformation from data obtained on a regular polar grid to a regular sine-space grid, and one of these is the processing of plane-polar near-field data. The most common approach to this task is to interpolate from the polar grid to an X-Y grid and then use the conventional 2D Fourier transform. This paper revisits an alternative algorithm, referred to herein as the polar-coordinate Fourier transform (PCFT), for doing the same transformation from polar input to a regular sine-space output grid. This PCFT has some advantages when processing data undersampled in their angular phi spacing, and appears to offer the possibility of probe correction without having to counter-rotate the probe. The process of the PCFT is similar to that of the conventional 2D Fourier transform. These two processes are compared. Rather than interpolating the polar data to the X-Y grid, the PCFT starts with a 1D transform along each diametric spoke of the polar wheel. Each spectral output is then rotated by the corresponding phi angle and interpolated to a common sine-space output grid. If probe-pattern correction is needed for a probe with no extra roll axis, then a notional approach is also described.
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.
In this work, a tunable frequency-selective surface is designed with a center frequency that can be varied with an applied DC voltage. An equivalent circuit representation of the FSS is derived from a finite-difference time-domain (FDTD) simulation of the passive FSS, allowing tuning circuits for the FSS to be designed in common circuit simulation tools such as SPICE. A comparison between the spectral response obtained from FDTD and equivalent circuit modeling (ECM) in SPICE shows that under certain conditions, ECM provides good agreement with full-wave analysis, is less computationally intensive, and provides physical insight. The ECM technique enables rapid design and analysis of various trade-offs, such as those between resonant frequency tunability and bandwidth. The ECM-designed circuit is then validated with full-wave analysis of the designed structure with active components using an FDTDSPICE hybrid co-simulator. Finally, applicability of the chosen active FSS topology as a metasurface for free-space dielectric material characterization is discussed.
The IEEE Std P2816 recommended practice for computational electromagnetics applied for the modeling and simulation of antennas is currently being developed by the IEEE Antennas and Propagation Standards Committee (APS/SC), sponsored by the IEEE Antennas and Propagation Society (APS). The document provides guidance on the numerical modeling of antennas deployed in free space using commonly adopted computational electromagnetics (CEM) techniques such as the finite element method (FEM), the finite difference time domain (FDTD) method, the Method of Moments (MoM), the finite integral technique (FIT) and the transmission line matrix (TLM) method. Benchmark models and comparisons of numerical simulation results are included for potential users of the standard to better understand the uncertainties and limitations of these techniques. A biconical antenna was previously proposed as a benchmark model. The numerical simulation results showed a good overall agreement among the participating laboratories and against the analytical solution. Herein, a 5G New Radio (NR) FR1 ultrawide band (UWB) antenna is proposed as another benchmark model for the development of IEEE Std P2816. In addition to the comparison of the numerical simulation results obtained from the participating laboratories, the simulation results are confronted with preliminary measurement results.
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.
This paper presents antenna design and measurements for wireless audio applications in the 470-600 MHz frequency range. Simulation and measurement results show that going from an external whip antenna to an internal helix antenna, realized gain was reduced between 2-4 dB across the desired frequency band, agreeing with or better than theoretical maximum gain calculations.
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.
A free-space material measurement for a small dielectric plate using a truncated Gaussian beam whose beam width is smaller than the material under test (MUT) is described. Measurement results of two glass plates of different thicknesses at W-band (75-110 GHz) show its validity and the minimum beam width of the truncated Gaussian beam for the reliable material property measurement of a small planar MUT.
In 5G O-RAN, a radio unit (RU) is connected to an upper-layer network element through an eCPRI interface, relying on digital modulation for data transmission. Therefore, unlike conventional 4G antenna system verification processes, RU radiation pattern testing in this data transmission mode necessitates novel testing approaches. Moreover, millimeter-wave signals in 5G undergo severe transmission losses and lack effective multipath channel characteristics, leading to poor base station coverages in this frequency range. The reconfigurable intelligent surfaces (RIS), an emerging technology that exploits the channel properties for the dynamic manipulation of the propagation environments, is a promising solution to the abovementioned problem. However, evaluating the effectiveness of the dynamic energy transfer for the RIS is a crucial challenge in the development of this technology. This paper presents the novel configuration based on the combined near-field and bistatic measurement systems at Taiwan Tech for RU and RIS performance verifications. We propose a near field measurement system to verify the radiation pattern of the RU in data transmission operation. Also, we integrate a compact antenna test range (CATR) and the planar near field scanner to form the bistatic measurement system and conduct performance evaluation of the scattering characteristics of the object under test. Those testing approaches can more accurately evaluate, verify, and optimize RF coverages of the network deployment for 5G and beyond.