AMTA Paper Archive
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Tunable Cellular Desensitization using SD Card Data Transfer
For some time now the CTIA W-IoT OTA Reverberation Chamber Ad-Hoc Group has been looking for an OTA test artifact that exhibited repeatable narrow band cellular desensitization so that it could be used to perform round-robin testing between labs and investigate the impact of different test methodologies (e.g. reverberation chamber vs. spherical antenna pattern measurement in an anechoic chamber) on intermediate channel desense testing. Since device manufacturers aren't eager to provide devices with known problems, some alternative was required. Attempts were made to modify a device by removing shielding cans, only to completely degrade device performance across the entire spectrum. Using an external signal generator feeding a coupler at the DUT was also considered, but cable effects and equipment variations would have impacted repeatability in the variety of anticipated test environments. Creating a custom device with an embedded interference source met with cost and other practical limitations that stalled progress along that avenue. A member of the working group related anecdotal evidence suggesting that SD card communication within the phone was known to be a problematic noise source that could cause cellular desensitization. Initial investigation centered on the use of an off-the-shelf SD card testing app to try to generate uniform traffic, but none of the evaluated tools had an option for continuous testing. Focus then turned to developing a custom app for the purpose, but later changes to the Android operating system have deprecated the use of external SD cards, removing standardized support and making the development of a custom application impractical. Another possible solution for long duration interference would be to just play a video from the SD card, but the variability of a typical compressed MPEG video, both in content and compression level, would likely cause surges of data transfer with pauses in between. What was needed was a solution to cause continuous data transfer with a constant signature (i.e. sending the same data constantly) to ensure stability and repeatability. Thus investigation turned to creating a customized video file in an uncompressed format to address these limitations. This paper will show the results of this effort.
Optimization of In-Vehicle Connectivity through Simulation-Augmented Antenna Measurements
As radiocommunications and internet-based services have become ubiquitous, customer expectations for infotainment capabilities and reliability in vehicles have largely increased. As such, the optimization of the distribution and orientation of antennas within the car is required to deliver the adequate connectivity performance. Yet, making direct measurements of electromagnetic field distributions radiated by structure-integrated radiofrequency transceivers is extremely tedious, if not practically and economically impossible. Recent papers introduced the approach of simulation-augmented measurements, appearing as a relevant solution to that problem. This method relies on a three-step approach: (i) measure the phasor electric field radiated by the standalone or part-integrated antenna module around the test sample; (ii) use an algorithm to calculate equivalent electric and magnetic currents over a surface closely encompassing the device under test (DUT); (iii) inject these currents as a Huygens source into a full-wave solver, where the complete scattering and absorbing environment is then taken into account. This paper presents the concrete application of this approach to the evaluation of the electric field inside a vehicle, based on separate measurements of WiFi and Bluetooth antennas. These measurements are performed using a spherical near-field system, with either the standalone antennas as DUT or the antennas embedded into the physical middle console of a car. The equivalent sources generated from experimental data are then imported into the virtual car model, and interior electromagnetic fields are computed using the Finite-Difference Time-Domain technique. The assessment is realized for various conditions without and with driver and passengers. The results are analyzed and limitations, as well as uncertainties of the technique are discussed.
Acceleration of Over-The-Air Measurements Under Extreme Temperature Conditions Through Optimization of Air Flow and Thermal Efficiency
5G communications have supported the deployment of millimeter-wave beam-steering technologies at an unprecedented commercial scale. Mobile phones operating in frequency ranges above 20 GHz integrate antenna arrays and radiofrequency front-ends which control magnitudes and phases of signals to enable adaptive beam-steering. As per the 3GPP Test Specifications, a large number of tests covering the various operational modes of such devices are required in order to establish that the performance is adequate for guaranteeing the integrity of the mobile network. The defined measurement methodology relies on Over-The-Air (OTA) evaluations in Compact Antenna Test Ranges (CATR). As mobile wireless user equipment are practically utilized in diverse environmental conditions, a part of the test plan imposes spherical OTA measurements at extreme temperature conditions ranging from -10 to +55° C. Such temperatures indeed influence the active electronics in the device under test (DUT) and hence the beam-forming performance. This paper presents an innovative realization of a CATR with embedded thermal chamber supporting the above-described test capabilities. Inventive steps are introduced to solve the complex engineering problem of allowing fast temperature ramps to go through the complete range in a few minutes, while allowing two-axis rotations of the DUT, and all of this with preventing damages from the anechoic chamber and positioner and limiting the radiofrequency impact of the thermal testing chain. Thermal and air flow simulation and measurement results are presented, establishing how the design allows sustaining high pressure with low air leakage. Measurements of the quality of quiet zone with and without thermal enclosure demonstrate the limited RF impact of the introduced materials encapsulating the DUT. The derived solution is applied to measurements of a commercial 5G mobile phone, illustrating the influence of the environment on the DUT operation and corroborating the need for such test scenarii.
EMF simulation of base station antennas in real sites using Spherical Wave Expansion and diffracted fields
Base station antennas for mobile communications (BTS) emit high levels of electromagnetic radiation in their vicinity. These antennas are usually located on the top of a building, and it is critical to determine those areas where the total power density surpasses the levels dictated by the regulators of the corresponding country. This estimation allows mobile operators to optimize the performance of the cellular network while keeping safe EM emission levels in occupational and public areas. The power density on a given region depends not only on the total radiated power but also the radiation pattern of the antenna and the influence of the environment. As a result, antenna measurements become useful to perform these calculations. This paper presents a simulation tool which computes EMF exposure values of BTS antennas considering the influence of the building roof. The tool uses analytical calculations to obtain a fast evaluation of the fields radiated by all the antennas of a given cell site. The calculations are performed considering the radiation of the antenna as a contribution of three different propagation phenomena: a free space direct radiation component, a reflected component due to the presence of the ground and a diffracted field due to the roof corners. Both direct and reflected rays are computed using the Spherical Wave Expansion (SWE) of the BS antenna assuming PEC boundary. The diffracted ray is computed using ITU 526-8 recommendation. The proposed software requires a measurement of the BTS antenna radiation pattern in anechoic chamber. Spherical near-field measurements are proposed to retrieve all antenna parameters needed for the calculations (SWE, efficiency, electrical steering configurations). Full details of all performed calculations will be disclosed on the paper, as well as some simulation examples with measurement data of real antennas to demonstrate its capability and computational efficiency.
Using a VNA Based Spherical Near Field Antenna Measurement System for Active Antenna System Performance Verifications
Nowadays, 5G new radio and commercial networks have been widely developed and deployed by many communication service providers around the world. State-of-the-art techniques such as massive multiple input multiple output systems, 3D beamforming technologies, etc. are utilized to enhance spectral efficiencies and system capacities within cellular coverage areas. Additionally, 5G base stations with active antenna systems (AAS) are comprised of the passive antenna array, transceiver frontend and base band units, all integrated into one module, so that the traditional antenna RF ports are replaced with ethernet-based interfaces. Consequently, different from conventional 4G antenna system verification processes, to ensure the optimal cellular signal coverages of the 5G AAS base stations, new measurement methods to verify the radiation properties at RF carrier frequencies of the AAS need to be employed. The radiation pattern test method of the AAS by using a vector network analyzer (VNA) based spherical near field antenna measurement system through over-the-air (OTA) to obtain the magnitude and phase distributions of the electromagnetic fields from the antenna under test (AUT) with single-tone transmitting will be presented in this paper. In order to verify the above mentioned concepts, a signal generator is used to provide the single-tone source into a commercial passive base station antenna. Also, two received channel connections to the VNA are included, where a reference antenna placed adjacent to the back of the AUT for phase recovery is added together with the existing probe of the spherical near field antenna measurement system for reconstructing the near-field amplitude and phase of the fields during scanning. Thus, the near-field to far-field transformations and back projections can be performed for active antenna performance verifications. Radiation patterns obtained by the above OTA near field measurement method demonstrate good agreements with those from conventional near field tests at 3.5 GHz for 5G FR1 AAS performance verifications.
Cylindrical Near-Field Measurement and Far-Field Characterization of 300-GHz Band Antenna Based on an Electrooptic Measurement Technique
We demonstrate cylindrical near-field measurement and far-field characterization of 300-GHz band antennas using photonics-based technologies. The measurement system is based on a self-heterodyne technique and non-polarimetric frequency down-conversion technique in which an electrooptic (EO) sensor was used. An optical beat signal generated using two 1550 nm laser diodes with the difference frequency of 300 GHz was EO converted by a uni-traveling-carrier photodiode (UTC-PD) to generate 300 GHz RF signal. The material of the EO crystal was a DAST (4-N,N-dimethylamino-4-N-methyl stilbazolium tosylate) and the dimension was approximately 0.5 mm x 0.5 mm x 1 mm. The EO probe was composed entirely of dielectric material, thus the scattering by the probe was minimized. In addition, the use of optical fiber significantly reduces scattering compared to conventional probe antennas that use metal cables or waveguides. As an optical local oscillator signal (LO signal), a coherently frequency-shifted optical beat signal generated based on the self-heterodyne technique was used. By tuning the frequency of one laser diode, the frequency of the RF signal can be swept. The system bandwidth is limited by the bandwidth of the UTC-PD, which covers WR-3.4 band (220-330 GHz). The RF signal up-converted to the optical domain in the EO crystal was coherently detected by a low-speed photodiode to generate intermediate (IF) frequency signal. The amplitude and phase of the IF signal, which are copies of those of the RF signal, were detected with a lock-in amplifier. The antenna under test (AUT) was a rectangular-type horn antenna (WR-3.4) with an antenna gain of approximately 25 dBi. The AUT was rotated by ±45° horizontally and the EO probe mounted on a 4-axis robotic arm was linearly moved vertically by ±15 mm to measure the cylindrical near-field distribution. The far-field distribution was estimated by transforming the measured cylindrical near-field distribution without probe correction. The simulation results and measured results were agreed very well. In E-plane, the first to third sidelobe levels agreed within 1 dB. The 3dB beamwidths of the measured result were 10.3° and 9.5°, whereas those of the simulated results were 9.5° and 9.7°, in the E- and H- plane, respectively.
Investigation of Inhomogeneity of Material Characteristics on the Hybrid-Absorber Performance
With the growing applications of wireless systems in different aspects of everyday life, from the consumer-electronic devices to internet-of-thing applications to wireless health-monitoring systems, there is an expanding need for reliable measurement of the radiating performance of these devices. The electromagnetic compatibility (EMC) tests, including immunity and interference tests, are normally done in shielded rooms the walls of which are covered by the so-called hybrid absorbers. These absorbers are made of a magnetic lossy layer giving absorption at low frequencies and a dielectric lossy geometrical absorber which is mainly responsible for the electromagnetic absorption at higher frequency range. The heart of hybrid-absorber design, which can be reduced to a wide-band matching problem, is to match the dielectric lossy part to the magnetic lossy layer. The magnetic layer which is mostly made up of a ferrite material, is a relatively thin layer, i. e. less than 1 cm thick, which is supposedly homogeneous. The dielectric geometrical absorber part has a relatively large thickness, e.g. 30 inches, and incorporates geometries like a pyramid to make a tapering against the wave which is going to be absorbed by the absorber. Because of the relatively large thickness of the dielectric lossy part and the production-process techniques used to make these parts, there are inhomogeneities in this part. In the current paper, the impact of the inhomogeneity of the dielectric part on the matching performance of the hybrid absorber is investigated in details. In the 1st stage, a 30-ich absorber is chosen and sliced in 15 different layers the permittivity is of each measured separately. Using these permittivity values, a complex model is made and simulated to get an expected reflectivity value on the ferrite layer. In the 3rd step, the absorbers of the same production batch are chosen to be measure in real-scale measurement setup and the reflectivity values are measured. Finally, the measurement and simulation results are compared and the impact of inhomogeneity of the dielectric absorber on the hybrid-absorber performance in concluded.
Numerical and Experimental Validation of Near-Field Power Density Reconstruction from Radiative Field Measurements
For millimeter-wave wireless devices used in the close proximity to the human head or body, the compliance evaluation to regulatory exposure limits is determined from near-field free-space power density measurements. For mobile phones and other portable equipment, the standard assessment technique involves the characterization of the power density on planes, as close as 2 mm from each facet of the device under test (DUT), as well as on anthropomorphic surfaces. These measurements are typically realized by means of a pseudo-vector diode-detected probe, acquiring the electric field magnitude and polarization ellipse at multiple locations over the scanning area. Phaseless techniques have been employed to deduce the required phase and magnetic field information for the calculation the Poynting vector. Although accurate, this technique presents some limitations: prohibitive test times; the inability to distinguish between various frequency contributions of the electric field due to the detection process; or the necessity to implement specific test modes in the DUT to fix the radiated beam in a given state. A recent paper proposed an alternative method which overcomes these listed limitations. The approach relies on the use of spherical antenna / over-the-air (OTA) phasor electric field acquisitions in an anechoic chamber environment, performed in the radiative field region and combined with near-field processing through equivalent currents reconstruction. This paper proposes an extensive validation of this method based on simulations and measurements of reference antennas, as defined in the IEC 63195. The reference measurements are realized with a standard-compliant 6-axis robot assessment system. The uncertainty contribution coming from probing at distances where reactive field components cannot be captured is investigated, demonstrating a negligible influence on reconstructed field distributions down to a third of the wavelength from the reference antenna, for which a theoretical interpretation is provided. It is also shown that characterizing the detailed changes in the reactive field is not necessary to obtain an accurate peak spatial-average power density value, which is the relevant metric for compliance assessment. A systematic analysis of the error affecting this specific quantity is also provided.
Numerical considerations to improve the Reduced-Order Model Approach for Antenna Measurements
The characterization of antennas is a time-consuming task. Its acceleration leads often to large and sensitive numerical problems. Therefore, special care must be taken of the choice of the parameters, the optimization, and the stability of the employed resolution methods. Based on Huygens’ principle, the radiation operator can be defined from an equivalent surface enclosing the Antenna Under Test (AUT). The discretization of this operator leads to the so-called radiation matrix. An expansion basis of the fields radiated from the equivalent to the measurement surface is constructed by the Singular Value Decomposition (SVD) of that matrix. The Reduced-Order Model (ROM) is the compressed representation of this basis obtained by truncating the SVD. The truncation order, T, is computed by inspection of the singular value distribution and is strongly linked to the number of degrees of freedom of the radiated fields. Several practical and technical aspects are studied in this article to provide a systematic, efficient and reliable procedure for the characterization of the radiated fields using the ROM. Analytical criteria are used to define the dimensions of the radiation matrix enabling a stable determination of the compressed basis. The truncation order, T, is the key-point of this method as it determines the size of this basis. Therefore, its variation is studied with respect to the discretization step and the geometry of both equivalent and measurement surface. Finally, the Randomized SVD (RSVD) is used in order to significantly reduce the computation time with negligible impact on the accuracy. To illustrate our procedure, it is applied to various scenarios and experimental results of spherical measurements. Estimations of the time savings by using the RSVD are also provided.
Ultra-thin EBG backed flexible antenna for 24 GHz ISM band WBAN
“A novel, ultra-thin, electromagnetic bandgap (EBG) backed antenna is presented for 24 GHz ISM band wearable applications. The via-less EBG unit cell shows both Artificial Magnetic Conductor (AMC) and EBG Characteristics. With dimensions of 0.254λ0× 0.254λ0, it is easy to fabricate at a millimeter-scale. The antenna has bow-tie slots, designed with an overall dimension of 0.91λ0 × 0.84λ0 × 0.01λ0, backed by a 5 × 5 element 0.01λ0 thick EBG/AMC structure; it is manufactured on a flexible Rogers 5880 substrate (thickness = 0.127 mm, = 2.2, tanδ = 0.0009). The proposed antenna is the thinnest (0.02λ0) EBG-backed antenna when compared to available K-band EBG-backed antennas. The performance of the EBG-backed antenna in terms of reflection coefficient and free-space radiation patterns is investigated in scenarios with and without structural bending. It is shown that the integration of the EBG enhances the antenna’s front-lobe gain by 2.63 dBi, decreases back-lobe radiation by 12.2 dB, and decreases 93% the specific absorption rate (SAR (1 g)) from > 28 W/kg to <1.93 W/kg, significantly reducing potential harm to the human body. Furthermore, the EBG-backed antenna was analyzed under a tough on-body and structural deformation measurement setup and the results show the performance of the EBG-backed antenna is highly insensitive to body proximity, and that its performance is preserved when bent along either axis. Therefore, Proposed EBG backed antenna structure demonstrates suitability for K band conformally mounted WBAN applications.”
Spectrum-analyzer-based Radar System Measurements in a Compact Antenna Test Range
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.
Activities within the EurAAP Working Group on Antenna Measurements
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.
Look Through Hygroscopic Indoor Materials at Frequencies from 750 GHz to 1.1 THz
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.
Radiation pattern measurements using an active radar module
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.
Methodology and Practical Considerations for the Implementation of the Three-Antenna Method in a Spherical Near-Field Range
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.
5G Base-station Network Optimization in Urban Wireless Scenario using Machine Learning
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.
Initial Development of Low-cost Custom Spherical Measurement Range
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.
Measuring Component Performance in an Integrated Antenna-Receiver System
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.
On the Uncertainty Sources of Drone-Based Outdoor Far-Field Antenna Measurements
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.
Consideration of the Feeding Networks for Measurement of mmWave/Sub-THz SoP/SoC/SoD Antennas in 5G and 6G
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.
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