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Highly integrated radar systems are becoming widely used, such as in automotive radars. To cope with the challenges of signal attenuation at millimeter-waves, antennas are placed directly on the circuit board of the chip or even integrated in the chip package. However, this complicates or even prevents conventional passive antenna measurements, as additional connectors or detached antennas will have severe impact on the antenna’s performance. We propose a measurement setup, that does not require physical connection to the antenna ports nor a phase reference from the transceiver chip. It allows for veritable measurements of a radar-module’s transmit antennas, while it is fully operational including beam-forming and beam-steering. The setup is built up in the Compact Antenna Test Range at the Institute of High Frequency Technology at RWTH Aachen University with a state-of-the-art 85 GHz spectrum analyzer. The propagation direction inside the chamber is reversed, so that the actively transmitting DUT can be mounted on top of the roll-over-azimuth positioner. The method is fully incoherent and therefore only suitable for phaseless measurements. It is tested with different antenna types and arrays mounted to an in-house designed evaluation board, based on the TI AWR automotive radar chipset, which operates at frequencies from 76 to 81 GHz. The results are compared against standard spherical near-field measurements, used as reference. Benchmarking the setup’s performance, dynamic range and uncertainty analysis are carried out with respect to the used spectrum analyzer mode, which allows for generic sweep-mode operation, pulse- and chirp-analysis with up to 5 GHz real time bandwidth. The transceiver’s power drift needs to be considered as well as timing constraints given by the chosen chirp mode and duty cycle. Contemplating the challenges of the proposed method, it can serve an emerging market for carborne radar systems, which cannot be appropriately measured by network-analyzer-based setups only.
In recent years, many activities have been carried out within the European Association on Antennas and Propagation (EurAAP) and the working group (WG) on measurements in particular. This group constitutes an important framework for collaboration to advance research and development of antenna measurements. The activities are divided in different tasks comprising measurements and comparison of reference antennas, contributions in the revision of IEEE standards on antenna measurements, self-evaluation measurements for facilities and new and emerging technologies for antenna OTA measurements. Special attention is dedicated to the activity on international comparison campaigns and evaluation that span more than 10 years of dedicated work by the WG. This task constitutes a crucial foundation for facilities to document and validate measurement accuracy among participants and provide an important prerequisite for certification of facilities and inputs to standards and research on measurement uncertainties. As regular inter-comparisons are a precious tool for traceability and quality maintenance, the campaigns have become a useful instrument for facilities to obtain and/or maintain an ISO17025 accreditation. International intercomparison campaigns within the WG span the frequency range from UHF-V band using different antennas: a mm-VAST antenna, a set of MIMO PIFA antennas, a SH800 ultra-wideband horn, a BTS1800 base station antenna, a SR40-A offset reflector and a set of chip reference antennas. This paper gives an overview and status on current campaigns within the working group, focusing on the useful criteria for comparing and evaluating large amount of measured antenna data. Updated results on running campaigns and proposed future initiatives will be discussed including an interesting synergy between measurement and simulation modelling tools.
This paper reports the look through losses witnessed for four hygroscopic indoor material groups, namely, wood, paper, brick, and leather employing the VNA-based Swissto12 MCK terahertz transmission waveguide measurements system. This study focuses on materials encountered widely in the interior of indoor environments. The hygroscopic nature of the chosen materials is studied by measuring the look through losses (i.e., penetration losses) for the dry materials followed by the wet ones in the 0.75–1.1 THz frequency range. The moisture or water content may significantly influence the terahertz wave propagation depending on the free and/or bound water percentage. In addition, this acquired knowledge facilitates the characterization as well as localization of these materials precisely and hence, demands thorough investigations. The chosen material samples along with their frequency-dependent material parameters, thicknesses, and roughness are modeled in CST, which gives a further probe into the interesting hygroscopic effects on penetration losses witnessed for the chosen material groups. Utilizing well-known models such as Bruggeman and Landau-Lifshitz-Looyenga, a 1–60 percent moisture content range is employed in the CST simulations. This paper, however, is the first-ever to investigate the characterization of propagation in hygroscopic indoor materials at THz frequencies. Preliminary measurement results exhibit that the look through losses unexpectedly decline for the chosen material groups in the wet state. These unusual effects on look through losses signify that the bound water molecules as compared to free water content manifest less influence on the THz wave attenuation. All details about the measurement setup and material samples along with both measurement as well as simulation parameters are revealed in the full paper to be presented at the upcoming AMTA symposium.
In the automotive sector, driver assistance systems are playing an increasingly important role in automated driving, with radar sensors being a critical component for environmental perception. The implementation of safety-relevant functions places ever higher demands on sensor technologies in order to provide high-quality and reliable data. For radar sensors the radiation pattern of the antennas is a crucial factor for the performance of the overall system. As the technology moves towards highly integrated systems, the antennas are integrated directly on the circuit board or even the radar chip package. This complicates or even eliminates the possibility for classical antenna measurements, as there is no access to the antenna feed line. Here the integrated receiver and transmitter module of the radar system are used to measure the two-way radiation pattern with a reflector. However, this leads to a lot of unknown factors and influences that differ from classical antenna measurements. Within this study the formal built up radar measurement setup for the robot-based antenna measurement system of the Institute of High Frequency Technology of RWTH Aachen University is used for accurate two-way pattern measurements based on the sampled raw data of the radar system. A modular frequency modulated continuous wave radar setup with high configurability is used to build up measurements on well-known antennas. The flexibility of the modular radar allows for measurements on different antenna types as scalar feed horn and travelling wave antennas. Different parameters like the choice of the reflector, the measurement distance and repeatability of the measurements are examined on their influence on the measured two-way-patterns of these antennas. The radiation patterns are resolved over the frequency bandwidth of the chirps using the intermediate frequency signal of the radar sensor to investigate the influences on their frequency dependence. The possibility on measuring the co and cross polarization components of the patterns is studied.
The three-antenna method is a way of calculating antenna gain without the need for a gain standard. Unlike the comparison or direct methods, the three-antenna method calculates antenna gain solely from measured data and does not require the gain of any of the antennas to be known in advance. As a result, it’s the most favored method in applications where accuracy is of chief concern, like in calibration measurements. However, implementing this method presents additional challenges related to the equipment required, test procedures, and analysis of the resulting data. In this paper, these challenges are addressed with a new methodology used to create a custom script and user interface within the NSI2000 software environment. The script itself is described with the aid of flow charts and then the validation process involving two test campaigns, using both calibrated and non-calibrated standard gain antennas, is given. Following these efforts, the three-antenna method was successfully implemented for the first time in a facility that traditionally only used the gain comparison method. The lessons learned from this project could also prove valuable in understanding the practical considerations concerning the implementation and use of the three-antenna method in any other near-field test range.
As the 5G system becomes today’s main wireless communication service, a MIMO(Multiple-In Multiple-Output) configuration has been considered as an essential feature to provide an unprecedented high date-rate transfer for the wireless service users. Therefore, it is a big concern to design best diversity antennas for a mobile station and base station which are supposed to operate in mm-Wave frequency bands. In addition to the diversity antenna design, optimally deploying the 5G radio frequency system consisting of the MIMO configuration is another big concern to the 5G wireless service providers, because the millimeter Wave (mm-Wave) is expected to lose its transmitting power more abruptly than the previous wireless services. In this paper, the deployment parameters related to the base-station antennas are studiedfor better 5G networkperformance by applying machine learning algorithm. At first, MIMO antennas based on a printed dipole pair are designed both for a mobile platform and a base-station platform by taking into account the MIMO performance factors: envelope correlation coefficient (ECC) and mean effective gain (MEG) at one of the 5G frequency bands (26.5~29.5 GHz). Secondly, the designed antennas are deployed into a urban wireless communication scenario mainly composed of mobile stations, base stations, and buildings. In the urban scenario, the 5G system performance are estimated in terms of received power, signal-to-noise-and-interference ratio, and maximum data rate. Finally, the 5G base-station system is studied to aim at the better system performance by using a machine learning technique which especially suggests optimum antenna parameters for the base-station deployment.
Measurements of antenna prototypes are a critical component of the development cycle for antennas, arrays, and other radiating structures. Benchtop tests to characterize the circuit performance of such devices are generally available to engineers and scientists, but the ability to capture the space (radiating) characteristics is often lesser available. This is not only due to the need for a vector network analyzer but also the necessity for mechanical infrastructure to sample the fields in a scan volume around the antenna (i.e., antenna range). Moreover, the software capable of any data manipulation is needed to obtain the far-fields either directly or from the sampled near-fields. Herein, we describe the initial exploratory development of a low-cost, bench-top, custom spherical range. The system consists of a phi-stage turntable where the antenna under test (AUT) is mounted, a theta-stage swing arm that sweeps the probe antenna in an arc about the center of rotation, and a polarization stage turntable on the probe antenna side. An adjustable scan radius of 30-40 cm is built into the theta-stage. The bulk of the range is fabricated using standard fused deposition modeling (FDM) 3D printing and inexpensive commercial off-the-shelf (COTS) components are used for the motors and controllers to keep cost of the system (excluding the network analyzer and RF cables) to around 500 US dollars, in accordance with the restrictions for an advanced antennas course class project. Development, fabrication, and assembly took place over the course of approximately a month. The drawbacks of the utilized materials, however, primarily manifest in the oscillations of the theta-stage due to the low-infill ratio (~10%) of the 3D printed plastic in conjunction with the weight of the probe antenna. Additionally, a basic spherical near-field to far-field transform code is developed. The measurement results of a wideband horn antenna are performed to validate the range performance and will be shown and discussed at the conference. Thoughts on future development and potential are also shared.
In this article, a method is presented which describes how to measure the separate performance parameters of an antenna-receiver system after they have been integrated into one system. The integrated receiver may perform different than the cascaded prediction of the pieces that make up the system due to component interaction. This article develops a method that allows the integrated performance of the individual components (an antenna and a receiver for this discussion) to be measured without disassembly. Using the described method, parameters such as, antenna gain, receiver gain, and receiver effective input noise temperature (correspondingly, receiver noise figure) can be measured. Once the receiver effective input noise temperature is measured, then it is possible to determine the remaining parameters. In the past, the difficulty has been separating out the two noise temperature terms (sky noise and receiver effective input noise). The presented method develops multiple equations which essentially separates out the two terms. Once the two terms have been separated, solving for the others is now possible.
Unmanned Aerial Systems (UAS), colloquially known as drones, offer unparalleled flexibility and portability for outdoor and in situ antenna measurements, which is especially convenient to assess the performance of systems in their realworld conditions of application. As with any new or emerging measurement technology, it is crucial that the various sources of error must be identified and then estimated. This is especially true here where the sources of error differ from those that are generally encountered with classical antenna measurement systems. This is due to the larger number of mechanical degrees of freedom, and to the potentially less repeatable and controllable environmental conditions. In this paper, the impact of some of these various error terms is estimated as part of an ongoing measurement validation campaign. A mechanically and electrically time invariant reference antenna was characterized at ESAESTEC’s measurement facilities which served here as an independent reference laboratory. The reference results were compared and contrasted with measurements performed outdoors at Quad- SAT’s premises using QuadSAT’s UAS for Antenna Performance Evaluation (UAS-APE). While a direct comparison between the measurement results from ESA-ESTEC and QuadSAT delivers information about the various uncertainties within a UAS-APE system in comparison to classical measurement facilities’ and the validity of such a system for antenna testing, other tests aim at providing an estimation of the impact of each error source on the overall uncertainty budget, thus paving the way towards a standardized uncertainty budget for outdoor UAS-based sites.
This paper presents a reliable design and measurement methodology of using various feeding networks for mmWave/Sub-THz SoP/SoC/SoD antennas in 5G and 6G communication. In order to achieve reliable and precison testing results, the electrical, mechanical, and thermal consideration have been precendently investigated and discussed through various examples of feeding network based on lots of the advanced materials and fabrication process. First, for a realization of the minimized discrepancy between simulation and measurement without any calibration kit and resistive films for 50-Ω termination load, two examples have been presented. In other words, a symmetrical power divider with back-to-back transition structures and a leaky wave antenna design topology featuring high attenuation constant have been demonstrated. Finally, despite challenging fabrication condition resulting in performance degradation, a low-loss transition structure in mmWave SoD antenna and its design methodology is also presented and discussed.
Electrical properties of materials are requisite to analyze and design electromagnetic (EM) devices and systems. Free-space material measurement method, where the measurand is the free-space scattering parameters of an MUT (material under test) located at the middle of transmit (Tx)/receive (Rx) antennas, is suitable for non-destructively testing the MUT without prior machining and physical contact in high frequency ranges. This paper proposes a free-space two-tier one-port calibration method using three planar offset shorts with the respective offset of ???????? for the measurement of the full scattering parameters of a reciprocal planar MUT from two successive oneport calibrations. Measurement results of a glass plate of 4.775 mm thickness are shown in W-band (75-110 GHz).
We present a new method for measuring thin, polymer sheets using a slotted rectangular coaxial transmission line (RCoax). This method allows a sheet of material to be inserted into the R-Coax slot, greatly simplifying the measurement procedure over traditional waveguide methods. The permittivity inversion is performed with the aid of computational simulations of the RCoax conducted across a range of expected dielectric properties. In particular, the slotted R-Coax device was optimized to enhance signal strength but has no simple analytical solutions for inversion. This new measurement technique is demonstrated on several thicknesses of commercial polyethylene terephthalate (PET) films, with a maximum thickness of 10 mils (0.254 mm). Due to the coaxial geometry, this technique does not have an intrinsic lower frequency cutoff and has an upper frequency cutoff near 3 GHz from over-modeing within the transmission line, though this frequency range could be extended by shrinking the fixture. However, the signal strength and calibration stability limit the useful range of permittivity measurement to 0.5-3 GHz for 10 mil thick specimens (and a range of ~1 GHz-3 GHz for 0.5 mil thick specimens). Repeatability for the real part of the permittivity ranged between 2-5% and loss tangents of ~0.006 were measured. Thus, this paper demonstrates the R-Coax measurement technique as a potential QA tool for microwave frequency electrical properties of thin polymer films.
This paper presents comparison of planar near field (PNF), cylindrical near field (CNF) and compact antenna test range (CATR) measurements for Standard Gain Horn (SGH) at K (18-25 GHz) and Ku-band (10-15 GHz) and metamaterial based high gain flat panel antenna at Ku-band. The effect of azimuth step size, number of cylindrical modes and radial distance error on CNF measurement accuracy are presented. The advantage of CNF for wide/large scan angles is discussed and measured results for metamaterial antenna at high scan angles are compared with those of CATR. Measurement time comparison between PNF and CNF is presented. One of the limitations of CNF compared to PNF is angular coverage in the elevation plane and this aspect is tried to be addressed supported by measured results.
This contribution presents a way to manufacture antennae, which allows to both effectively simplify the production and reduce associated costs as well as the weight. Amongst other examples for aperture antennae this is shown for a configuration given by the slotted waveguide antenna toolkit presented in [1]. In simplified terms the procedure consists of shaping the HF-transparent rigid foam to the size of the antenna’s cavity, attaching the connector(s) and electroplating it with copper. The manufacturing steps are shown in detail, which is followed by a characterization including the weight as well as the antenna performance such as S11 and the antenna pattern for horizontal polarization. These results validate the applicability of the presented method and open windows of opportunities especially in contexts in which intricate cavities and weight pose critical issues.
Diagnostic techniques are crucial in antenna development and testing to enhance the Device Under Test (DUT) performances and identify the cause of possible failures in the qualification process. Among different approaches [1]-[8], it has been demonstrated that the equivalent currents method (EQC) [8]-[9], implemented in [10], is one of the most efficient for investigations in various application areas [11]-[13]. Indeed, the generality of the 3D reconstruction surface enclosing the DUT is a key feature, it ensures that this technique is unique and highly suitable for diagnostics, respect to traditional methods based on plane wave expansion. To handle electrically large problems, the EQC method has been initially based on a Fast Multipole Method (FMM) [14]. The recent advent of 5G technologies has led to an increasing need in terms of antenna electrical dimensions. Therefore, a novel technique based on a Nested Skeletonization Scheme (NSS) has been implemented to guarantee a further reduction of memory requirements and computational time. The new capability has been demonstrated in the past for a patch array antenna [15]. In this paper, the diagnostic capabilities of the EQC approach are applied to an early prototype of an electrically large array antenna for 5G antenna measurements applications [16].
An antenna measurement system at the Institute of High Frequency Technology at RWTH Aachen University is being established containing a six-axis robot arm allowing the realization of numerous measurement geometries. Room scattering is one of the most crucial uncertainty terms in every antenna measurement which becomes even more interesting in a dynamic scattering situation. To determine the scatteringinduced interference caused by the robot, a motion-capable model is developed and firstly simulated using the multi-level fast multipole method between 8GHz and 12GHz to qualitatively assess the surface currents. Secondly, asymptotic simulations are carried out using physical optics for the most important robot positions at 60GHz which is in the frequency range where the system is operated. For example, differences in the same simulation points of up to 20dB are shown for different robot positions. Based on the simulation results, the measurement sequences can be optimized by selecting a trajectory which reduces the scattering effects. In addition, the strongest scattering sources of the robot are identified in order to cover these parts by absorbers. Therefore, the knowledge gained from the simulations can be applied to the measurement system to improve the performance of antenna measurements.
Instrumentation radar metrology waveform techniques that simultaneously transmit two orthogonal sequences of orthogonal electromagnetic polarizations are explored for applicability toward both static and dynamic RCS signature and ultra-wideband imaging measurements using simultaneous H-pol and V-pol (SHV) waveforms. Static, pulsed measurements with independent transmit polarizations are modulated and radiated; reflections from a depolarizing target are measured where the return signals are coherently combined. Each transmit polarization is independently modulated using a diverse phase sequence, which leaves a unique “fingerprint” by which the orthogonal polarization separation is achieved. Using only the coherent combination and associated transmit and receive RF channel characterizations, the original measurements are reconstructed. Simulations serve as a baseline for measured results, from generating pure SHV waveforms and then providing simultaneous full scattering matrix (FSM) measurements, in order to achieve greater purity of FSM signatures, while reducing measurement times by a factor of two.
Radar sensors are an essential component in the automotive sector and take over safety-relevant functions in the field of autonomous driving. Therefore, the need for validation of automotive radar systems is increasing. Within this paper, a measurement setup for automated static and dynamic tests of integrated radar sensors is set up in the robot-based measurement chamber available at the Institute of High Frequency Technology, RWTH Aachen University. The system parameters two-way pattern, range and speed resolution as well as angular resolution and separation capability are measured and analyzed for an integrated automotive radar sensor. The measured results show the expected performance of the radar system and point out the high variability of the built setup.
The Plane Wave Generator (PWG) concept has recently been presented for millimeter wave applications [1-2]. The PWG has attracted interest, also because of its unique application in direct testing of 5G/6G enabled devices while in use by life people or mounted on suitable phantoms. This test feature is important to evaluate the shadowing effect by the user and the effectiveness of distributed array system on devices to overcome the shadowing. In this paper, we investigate the feasibility and achievable measurement accuracy in such scenarios. Using the measured performance of the PWG reported in [1-2], the measurement scenario is emulated accurately and compared to the reference case.
Reconfigurable antennas are very widely useful antennas, but they require extended measurement periods to characterize the range of specified beams. Time-saving measures typically come at the cost of measurement quality. The goal of this effort was twofold: 1) to investigate ways to improve all antenna measurements, including analyzing antenna positions within range spaces, absorber configurations, and mounting structures and 2) to investigate the procedure by which reconfigurable antennas are optimized and determine efficient measurement quality and time-cost tradeoffs.