AMTA Paper Archive

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.

Modern antenna range design is often a careful balance of several competing objectives. Some of these design parameters are defined by the antenna under test (AUT), i.e. millimeter wave (Ka-band) test frequencies, frequencyconverting and non-converting AUTs, high-power radiation requirements, pulsed RF requirements, and interleaved transmit and receive (T/R) requirements. Other parameters are driven by the AUT’s application, like requirements for providing accurate pattern, gain, EIRP, and G/T predictions based on the measurement data. Yet other parameters are driven by cost and risk considerations, like the need for all-at-once acquisitions incorporating multi-frequency, multi-port, dual-pol, and multistate measurements. Also included in the “cost and risk” category is the need to collect all these measurements in the least amount of time. A planar near-field antenna range designed with all these parameters in mind has been realized and is currently operational. This 1 m x 1 m planar near-field range incorporates several novel electrical and mechanical features, and we illustrate these features in terms of their driving requirements and their limitations. Included in our discussion: modular T/R range “front ends,” reconfigurable probe networks, absorber cooling strategies, near-field probes for high-power measurements, interleaved single-port transmit and multi-port receive measurements, and distributed pulse mode range architectures.

A set of Dual-Polarized Antennas with a 3:1 operating bandwidth has been developed for use in near-field ranges as the probe or range antenna and for use as a Compact Antenna Test Range (CATR) feed [1]. Key development parameters of the antenna are: a wideband impedance match to the coaxial feed line, E and H-plane 1 dB beam widths in excess of 30 degrees, -30 dB on axis cross-polarization, minimum polarization tilt and a phase center that varies over a small region near the aperture. To accomplish these design parameters, a family of range antennas has been developed and previously introduced. Two versions of the antenna have been manufactured and tested for performance. A 2-6 GHz version has been developed using traditional machining techniques and a 6-18 GHz version has been produced using additive manufacturing (3D printing) techniques [4]. These antennas provide proper illumination of the quiet zone for compact ranges used for antenna measurements as well as radar cross section (RCS) measurements. For RCS measurements, an additional requirement for time-based energy storage performance is considered. Energy storage in the feed can result in a pulse spreading or additional copies of the pulse in time, resulting in poor performances of the target characterization. This effect is called ‘ringdown’. In this paper, we focus on the RCS ringdown performance of the 6-18 GHz antenna produced using additive manufacturing. The measured performance of the antenna will be presented and discussed. Finally, the applicability of the antenna as a CATR feed for RCS measurements will be discussed.

Antenna performance plays a significant role in synthetic aperture radar (SAR) image quality, particularly for nondestructive evaluation (NDE) applications. To obtain high image quality and target detectability, SAR imaging systems should possess good resolution (cross- and along-range), and a relatively large penetration depth. Consequently, the antenna used must be wideband with a relatively wide beamwidth for high resolution and operate at low starting frequency for sufficient penetration depth. Meanwhile, antenna aperture size should be small rendering it sufficiently portable for scanning purposes or when employed within imaging arrays. However, increasing frequency bandwidth, reducing minimum frequency of operation while maintaining small aperture size (resulting in wide beamwidth), all at the same time is difficult. To this end, double-ridged horn (DRH) antenna, with flared aperture for improved radiation efficiency and performance is found to provide a good compromise among these parameters. Therefore, an improved modified design of DRH is proposed. The dimensions of its geometry are optimized to provide low unwanted reflections. Curved surfaces are attached at the end of the two ridged walls for better aperture matching. The final aperture size of the antenna is 230 ? 140 mm², operating in the 0.5-4.0 GHz frequency range, and with a relatively wide beamwidth in its near-field region where most NDE imaging measurements are conducted. Measured reflection coefficient by using the fabricated antenna is used to verify the simulation results. Comparisons are also made with similar designs of DRH found in the literature showing that the proposed antenna has smaller electrical length with respect to the lowest operating frequency for designs without using absorbing material. Moreover, to conduct wideband SAR imaging, a new phase calibration method, using a small electric field monopole probe, to measure the phase change between the antenna aperture center and the input feed port for each frequency component is developed. Imaging results over a large concrete slab with delamination and voids simulated by foam and plastic sheets show that the proposed calibration approach works well, and the proposed antenna can effectively detect all of these defects with different scattering properties.

The CISPR 16-1-5 standard requires site attenuation (SA) measurements for the validation of Calibration Test Sites (CALTS) and Reference Test Sites (REFTS). CALTS validation requires horizontally-polarized SA measurements, while REFTS validation requires both horizontally- and vertically-polarized measurements. These measurements are made with tuned linear dipole antennas driven from coaxial transmission lines via balancing networks (baluns). According to the CISPR standard, the effects of the baluns are removed with a substitution measurement. Specifically, the baluns are connected back-to-back (balanced to balanced) with the elements removed and the port-to-port insertion loss then measured. This insertion loss is then subtracted from the port-to-port insertion loss with the antennas assembled and in place on the OATS. Thus, the measurement is a true RF substitution measurement. The baluns must be perfectly symmetric for this measurement to be sound. It is then accurate only if the baluns are very well matched simultaneously to both to the coaxial transmission lines and the dipole antennas. Essentially, the dipole-to-dipole transmission, the 2-port network which is substituted, would have to behave as a matched attenuator. In the CISPR standard SA measurements are made a a minimum of 24 specific frequencies between 30 and 1000 MHz. The height of the transmitting antenna above the ground plane in all cases is 2 m, but the height of the receive antenna varies in order to avoid a transmission null. For each one of these measurements it is possible to obtain a perfect match for each dipole antenna. However, the matching network would be different for each frequency and also for the different heights involved. Thus, there is impetus to use broadband baluns and resistive matching pads. If this approach is selected, neither dipole can be perfectly matched. Moreover, if the balun is required to operate over a broad bandwidth, it is difficult for itsperformance to be made so good that it could be considered ideal. By employing a full 4-port model for antenna-to-antenna transmission on an OATS between linear dipoles with imperfect baluns and thus unbalanced antennas, we assess measurement error for topologies of balun/attenuator combinations for the CISPR 16-1-5 SA measurements.

Accuracy in a measurement campaign is dependent on many factors. Some of these factors are in the physical components used, the requirements of the electromagnetics involved and the procedural requirements of the campaign. This paper will focus on how the mechanical accuracy of the equipment can impact total cost. The current stage in the life cycle of the AUT (design, production, repair) also impacts total cost. The affordability of the accuracy in terms of more costly equipment, calibration processes and operator and test range time may be the determining factor. Throughput needs may limit the accuracy that can be obtained. The accuracies required for each metric must then be evaluated against the accuracy of an available test range(s) or the renovation of an existing range or construction of a new range to meet the accuracy requirements. Two case studies included in this paper are: 1) the improvement of the positioning accuracy of a rotator via custom hardware and calibration for a severe global positioning accuracy specification and 2) the improvement of the planarity of an X-Y scanner system for use at increasing frequencies.

Near-field measurements on antennas require magnitude and phase information dependent on the antenna position to support the near-field to far-field transformations. Modern active antennas are often integrated into frequency converters with embedded local oscillators (LO). For example, devices ranging from small 5G transceivers to large satellite payloads often need to be tested with the antenna integrated into the overall solution. There is no access to the embedded LO signal in these systems. The unknown phase of the embedded LO masks or corrupts the near-field phase measurement of the integrated antenna under test. A novel solution to this challenge is presented based on a new Vector Network Analyzer (VNA) platform. The system utilizes two stimulus signals (a measurement signal and a pilot signal) to characterize the antenna under test which is integrated into the frequency convertor. The pilot signal captures the phase information of the embedded LO, allowing the measurement signal to capture the antenna's magnitude and phase pattern as the antenna under test is moved within the near-field region.

3D-printing methods presents unique opportunities for new antenna applications. One of these applications of particular interest is integrating antennas onto automotive vehicle bodies. Currently the automotive industry is experiencing a growth in number of on vehicle antennas to support connectivity and internet of things. This combined with the physical nature of automotive designs (large areas of non-conductive materials) results in an ideal implementation of 3D-printed technology. Key technologies of implementation include both cellular and vehicle to everything communications (V2X) as these play a critical role to the implementation of the connected vehicle. For the cellular operations connectivity can require up to 4 MIMO antennas operating from 600 MHz to 5 GHz. In addition, V2X operates in the 5.9 GHz frequency band, requiring up to 2 antennas. The result is a large number of varied types of antennas. Therefore, additive manufacturing techniques is an ideal technology to simplify and progress automotive antenna design and production. Moreover, Aerosol Jet Printing (AJP), as a contactless technique, can be exploited to fabricate conformal antennas. AJP allows the development of electronic components on any curved or flat body and gives the opportunity to mix different materials to print on the unique surfaces found in the automotive industry. The presented antenna is designed and simulated using Ansys HFSS and fabricated using Optomec Aerosol Jet Printer. The antenna is initially printed using the Clariant Prelect TPS 50 G2 silver ink on the Rogers Ultralam 3850 (LCP) substrate and then techniques are developed to print the antenna on the ABS substrate that is taken from a plastic trunk lid of a commercial vehicle. The antenna is dual-band, operating at the cellular and C-V2X bands and has an omnidirectional pattern at the cellular frequencies where its average realized gain on H-plane, as simulated in the ANSYS EM software, is 0.2 dBi at 836 MHz and -4dBi at 5.9 GHz. The antenna fabricated on LCP using Additive Manufacturing and is measured in a Satimo spherical nearfield chamber with a resulting average realized gain on H-plane is -1.8 dBi at 800 MHz and -3dBi at 5.9 GHz.