AMTA Paper Archive
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Proposed Changes and Updates on IEEE Std 1128 - Recommended Practice on Absorber Evaluation
The last published version of the IEEE Std 1128 is the 1998 edition. It is titled "Recommended Practice for RF Absorber Evaluation in the Range of 30 MHz to 5 GHz". Over the years, the document has been used widely for absorber evaluations in electromagnetic compatibility (EMC) applications as well as in antenna and microwave measurement applications. Besides the obvious frequency range which needs to be expanded to satisfy today's applications, several areas are in need of an update. The proposed document will change the upper frequency limit to 40 GHz (with provisions in the document to potentially extend above 40 GHz based on test methods). Measurement uncertainties were not discussed in the IEEE Std. 1128-1998. In the new edition, measurement instrumentation and test methods are expected to be updated with guidance on estimating measurement uncertainties. In the proposed document, a section on absorber evaluations for high power applications is planned, and fire properties and test methods will be included.
Accurate Calibration of Truncated Spherical Near Field Systems with Different Ground Floors using the Substitution Technique
The calibration of the antenna measurements system is a fundamental step which directly influences the accuracy of any power-related quantity of the device under test. In some types of systems, the calibration can be more challenging than in others, and the selection of a proper calibration method is critical. In this paper, the calibration of the truncated spherical near-field ranges typically used for automotive tests is investigated, considering both absorbing and conductive floors. The analyses are carried out in a 12:1 scaled multi-probe system, allowing access to the "true", full-sphere calibration which is used as reference. It will be demonstrated that the substitution (or transfer) method is an excellent calibration technique for these types of systems, if applied considering the efficiency of the reference antenna.
Comparative Investigation of Spatial Filtering Techniques for Ground Plane Removal in PEC-Based Automotive Measurements
Radiating performances of vehicle-installed antennas are typically performed in large spherical near-field systems able to accommodate the entire car. Due to the size and weight of the vehicle to be tested, such spherical systems are often nearly hemispherical, and the floor is conductive or covered with absorbers. The main advantage of the first is the ease of the accommodation of the vehicle under test. Conversely, the latter is more time consuming in the setup of the measurements because the absorbers need to be moved in order to be placed around the vehicle. On the other hand, the absorber-covered floors emulate a free-space environment which is a key enabling factor in performing accurate measurements at low frequencies (down to 70 MHz). Moreover, the availability of the free-space response allows easy emulation of the cars' behaviors over realistic automotive environments (e.g. roads, urban areas etc.) with commercially available tools. Such emulations are instead much more challenging when a conductive floor is considered. Furthermore, the raw measurements over conductive floors are a good approximation of realistic grounds (such as asphalts) only in a limited number of situations. For these reasons, when PEC-based automotive measurements are performed, it is often required to retrieve the free-space response, or equivalently, to remove the effect of the conductive ground. In this paper two spatial-filtering techniques (the spherical modal filtering and the equivalent currents) will be experimentally analyzed and compared to verify their effectiveness in removing the effect of the conductive floor. For this purpose, a scaled automotive PEC-based measurement setup has been implemented considering a small spherical multi-probe system and a 1:12 scaled car model. The two techniques will be analyzed considering two different heights of the scaled car model with respect to the conductive floor.
Spherical Near-Field Measurements of Satellite Antennas at Extreme Temperatures
Antenna systems commonly used in space applications, are often exposed to extreme environmental conditions and to significant temperature variation. Thermal stress may induce structural deformations of the radiators or affect the RF performance of the active front-ends. These are some of the reasons that pushed the testing technology to characterize the radiating proprieties of Antennas Under Test (AUT) in realistic thermal conditions. Testing facilities available for these purposes are nowadays typically limited in terms of temperature range, measurable radiation pattern and size of the AUT. This paper describes the multi-physics design considerations (i.e. thermal, structural and RF) for the development of a novel facility to evaluate AUT radiation pattern characteristics in thermal conditions, from L to Q band, as an add-on feature to the ESA-ESTEC Hybrid European RF and Antenna Test Zone (HERTZ), located in Noordwijk (The Netherlands). The goal is to extend such a testing to AUTs up to 2.4m diameter in envelope over an extreme temperature range (+/-120°C), allowing a free movement of the AUT and taking advantage of Spherical Near-Field (SNF) measurement techniques.
Experimental validation of Reference Chip Antennas for 5G Measurement Facilities at mm-Wave
In this paper, the experimental validation of a micro-probe fed reference antenna targeting the upcoming 5G applications (24.25-29.5GHz band) is presented. The main purpose of these reference antennas is to serve as "gold standards" and to perform gain calibration of 5G test facilities through the substitution method. The outline of these antennas is based on a square array of four printed patches enclosed in a circular cavity. The RF input interface is a stripline-to-coplanar waveguide transition and allows for feeding the device with a micro-probe. Performance obtained by high-fidelity modeling is reported in the paper and correlated to experimental data. Interaction and unwanted coupling with the test equipment are discussed. The use of echo-reduction techniques and spatial filtering is investigated to mitigate these effects.
Virtual Drive Testing based on Automotive Antenna Measurements for Evaluation of Vehicle-to-X Communication Performances
In vehicle communications, so as Vehicle-to-X (V2X), field trials are challenging due to high mobility scenarios and dynamic network conditions. It is complex to interpret measurements, to isolate performance from different components in an integrated system. Consequently, it is desirable to test under repeatable laboratory conditions in the early stages of the development cycle, where designers can quickly validate performance and make rapid modifications to prototype hardware and software cost-effectively. Virtual Drive Test (VDT) has attracted great interest from industry and academia. The objective of VDT is to recreate an approximation of the real-world communication conditions in a controlled laboratory environment. VDT is appealing, since testing can be performed in an automated, controllable and repeatable manner, which can considerably reduce testing time and costs, and meanwhile accelerate actual infrastructure deployment. In this paper we present a new VDT technique which allows to evaluate the V2X communications performances taking into account the measured characteristics of transmit and receive antennas installed on vehicles. The proposed VDT technique is a multistage process where radiation characteristics of the vehicle mounted antennas are first measured in free-space conditions in a controlled and repeatable laboratory environment. The Spherical Wave Expansion (SWE) is then applied to the acquired data in order obtain the Spherical Wave Coefficients (SWC) of the measured devices. From the SWC, the transmission formula (or coupling equation) normally involved for probe correction purposes in spherical near field measurements, is then applied in order to evaluate the coupling between two vehicles. The transmission formula has been properly adapted in order to consider variable distances between the vehicles and arbitrary vehicle orientation so that a generic road path can be easily emulated. In the proposed formulation also variable ground conditions can be considered allowing for a more realistic emulation of the final environment. The proposed technique is presented taking into account measurements of a representative scaled automotive scenario.
A Simple High-Perfomance P-Band First-Order Dual-Port Probe for Spherical Near-Field Antenna Measurements based on the Shorted Annular Patch Antenna
This paper presents a new type of P-band first-order dual-port probe for spherical near-field antenna measurements. The probe is based on the well-known shorted annular patch antenna but some extensions are introduced for the probe application. This probe is mechanically simple which facilitates its manufacturing and operation. In addition, it has high performance for impedance bandwidth, pattern, directivity, and gain.
3D Printed Magneto-Electric Phased Array Antenna for Various 5G New Radio Bands
A dual linear polarized 3D printed magneto-electric phased array antenna for various 5G New Radio (NR) frequency bands is proposed and its beam steering performance is investigated. The magneto-electric radiating element exhibits a well-defined stable pattern quality, low variation in the impedance over a wider bandwidth and high port to port isolation in a dual polarization configuration. The analog beamforming network (BFN) of the array is also designed. The fabricated board will be combined with the 3D printed array aperture for experimental verification of the scan performance.
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