Standard Gain Horn Antenna Research Articles

Near-field antenna measurement based on Rydberg-atom probe.

Current near-field antenna measurement methods are commonly based on metal probes, with the accuracy limited and hard to be optimized due to the drawbacks they suffered, such as large volume, severe metal reflection/interference and complex circuit signal processing in parameter extracting. In this work, a novel method is proposed based on Rydberg atom in the near-field antenna measurement, which can offer a higher accuracy due to its intrinsic character of traceability to electric field. Replacing the metal probe in near-field measurement system by Rydberg atoms contained in a vapor cell (probe), amplitude- and phase- measurements on a 2.389 GHz signal launched out from a standard gain horn antenna are conducted on a near-field plane. They are transformed to far-field pattern and agree well with simulated results and measured results by using a traditional metal probe method. A high precision in longitudinal phase testing with an error below 1.7% can be achieved.

Battery-Free, Artificial Neural Network-Assisted Microwave Resonator Array for Ice Detection

Ice detection has developed into an integral part of aerospace and wind turbine sectors with the aim of preventing hazards and component breakdown. This article presents an ice detection system consisting of a battery-free, chip-less wirelessly interrogated resonator array, and an artificial neural network for enhanced detection robustness. The designed array of split-ring resonators (SRRs), operating at 3.05 GHz, was a narrowband frequency-selective structure with a ground plane reflector which shielded resonance from the effect of installation material. For an incident wave on the array’s surface, the reflection coefficient changed with the electrical properties of the ice and water, consequently affecting the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> parameter of an interrogator antenna. The array had a surface area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$13\times6.5$ </tex-math></inline-formula> cm2 and a substrate thickness of 0.79 mm and was wirelessly interrogated from a distance of 33 cm by a standard gain horn antenna. A custom LabView program was utilized for time-based data acquisition of the antenna’s reflection coefficient [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> (dB)], with results demonstrating a resonant frequency shift of 150 MHz when 30 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{L}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$ </tex-math></inline-formula> ) of ice was formed on the main split of SRRs. The artificial neural network then classified the reflection coefficients of the interrogator antenna to enhance ice/water differentiation. The neural network improved the classification of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> (dB) raw data to 94.67% while achieving an accuracy of 93.33% for a noisy simulated data set. The proposed battery-free artificial neural network-assisted ice sensor can be implemented in various sizes (depending on the footprint requirements of installation) with applications in aerospace and wind turbine industry.

Multi-Layer Material Characterization at Ka-Band Using Bayesian Inversion Method

This paper presents the implementation of the Bayesian inversion method for the characterization and estimation of different dielectric material properties. The scattering parameters of single and multi-layer materials are measured using a free-space experimental setup using a standard gain horn antenna and a Vector Network Analyzer (VNA) at Ka-band (26–40 GHz). The relative permittivity, material thickness, and material positioning error are defined as model parameters and estimated using the observed (measured) data. The FR4 Epoxy, Rogers RT/Duriod 5880, and Rogers AD600 with different relative permittivities and thicknesses are used in the measurement setup. The results displayed good agreement between model parameters and estimated properties of the presented materials, while the corresponding eigenvectors provided a level of confidence in model parameter values. The results were compared with different reported techniques to showcase the possible use of the presented method in microwave imaging, non-destructive testing, and similar applications.

Antenna Diagnostics Based on Infinitesimal Dipole Modeling With Limited Measurement on Antenna Aperture

This letter presents an antennadiagnosis method using infinitesimal dipole modeling. For antenna diagnosis, it is important to estimate the current distribution of the antenna aperture. By using the measured near-field data of the antenna, the infinitesimal dipole current distribution that can generate the same near-field measurement result is extracted. This current distribution can be considered as a back-projection image on the antenna aperture. Using the infinitesimal dipole modeling, accurate antenna diagnosis is possible even by using only the measured near-field which is limited over the antenna aperture. We compared the results of the conventional antenna diagnosis method based on Fourier transform and the proposed method for the near-field measurement results of the standard gain horn antenna. Although the limited near-field measurement over the antenna aperture, the back-projection image for the antenna diagnosis of the proposed method has a very high resolution.

Broadband interconnected receiver–transmitter surface for generating dual circularly polarized dual beams

We propose an interconnected receiver–transmitter surface (IRTS) for simultaneously generating left-hand circularly polarized (CP) beams and right-hand CP beams based on the Pancharatnam–Berry phase, thus realizing dual CP dual beam radiations. The IRTS is composed of upper-layer gradient patches and lower-layer periodic patches that are connected by the metal probes that cross the center tears of the middle metal ground. The lower-layer patches of the IRTS can receive linearly polarized waves and couple the energy into the upper-layer by the metal probe for obtaining dual CP dual beam radiations. In particular, the working bandwidth of the present design can also be further extended when both IRTSs with adjacent working frequency bands are superimposed on each other to form a broadband IRTS (BIRTS). Finally, we fabricate the proposed IRTS and BIRTS with a standard gain horn antenna as the feed and experimentally demonstrate the functionalities of generating dual CP dual beams.

Stereolithographic additive manufacturing of Luneburg lens using Al2O3-based low sintering temperature ceramics for 5G MIMO antenna

In this paper, we provided a manufacturing method for low-sintering-temperature radio frequency (RF) devices by stereolithographic (SLA) printing. The effect of ceramic powder percentage on rheological properties, curing behavior, sintering properties, microstructure, and dielectric properties was discussed. With the proportion of ceramic powder ranging from 60 wt% to 75 wt%, the viscosity of slurries declined, the sintering shrinkage rate varied from 21.61% to 15.83%, the dielectric constant raised from 5.22 to 6.64, and the dielectric loss initially reached the optimum value of 0.0024 and then deteriorated to 0.0035. The maximum solid content of slurries was 75 wt%, and the printable viscosity should be below 7.33 Pa·s. At the mass ratio of 65:35, the samples sintered at 850 °C showed good properties: a density of 3.0135 g·cm−3, a dielectric constant of 5.56, a low dielectric loss of 2.4 × 10−3, and τf = −32.76 ppm/°C. The printed Luneburg lens showed a gain enhancement of over 5 dB, by using a 10 dBi standard gain horn antenna as a feed source. Thus, this research established a foundation for the fabrication of ceramic RF devices with high-performance, complex structures, and low sintering temperature via SLA printing.

Broadband Lens-Integrated CMOS Camera-Type THz Compact Antenna Test Range

This article presents the concept of a lens-integrated CMOS camera-type terahertz (THz) compact antenna test range (CATR) to determine the far-field characteristics of transmitters (TX), including the radiation pattern, directivity, half-power beam-width (HPBW), and radiation power. For concept validation, the frequency-dependent far-field radiation pattern of a 0.6-1.1 THz TX equipped with a 23.7-28.2 dBi standard gain horn antenna was measured using THz CATR. Directivity, HPBW, and radiation power have been extracted from THz CATR measurements. The first two parameters are compared with values obtained from calculations, full-wave simulations, and reference measurements performed at a conventional far-field range. In contrast, the third parameter is compared with a reference measurement performed with an absolute power meter. The following performance was achieved employing super-resolution imaging. Frequency-dependent directivity and HPBW were determined within a root mean square (RMS) accuracy of 0.85 dB and 1.16 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , respectively, related to reference measurements performed at the conventional far-field range. The frequency-dependent radiation power was determined within an RMS accuracy of 0.7 μW related to reference measurements with the absolute power meter. Camera-related limitations concerning the THz CATR application are discussed in detail, such as field-of-view limitations, angular resolution limits, scan loss, pixel-to-pixel variation, signal-to-noise ratio limitations, and the interaction between TX and camera lens.

A Self-Calibrated SI-Traceable Rydberg Atom-Based Radio Frequency Electric Field Probe and Measurement Instrument

We present a self-calibrating, SI-traceable broadband Rydberg-atom-based radio-frequency (RF) electric field probe (the Rydberg Field Probe or RFP) and measurement instrument (Rydberg Field Measurement System or RFMS). The RFMS comprises an atomic RF field probe (RFP), connected by a ruggedized fiber-optic patch cord to a portable mainframe control unit with a software interface for RF measurement and analysis including real-time field readout and RF waveform visualization. The instrument employs electromagnetically induced transparency (EIT) readout of spectral signatures from RF-sensitive Rydberg states of an atomic vapor for continuous, pulsed, and modulated RF field measurement. The RFP exploits resonant and off-resonant Rydberg-field interactions to realize broadband RF measurements at frequencies ranging from ~10 MHz to sub-THz over a wide dynamic range. The RFMS incorporates an RF-field-free atomic reference and a laser-frequency tracker to ensure reliability and accuracy of the RF measurement. We characterize the RFP and measure polar field and polarization patterns of the RFP at 12.6 GHz RF in the far-field of a standard gain horn antenna. Measurements at 2.5 GHz are also performed. Measured patterns are in good agreement with simulations. A detailed calibration procedure and uncertainty analysis are presented that account for deviations from an isotropic response over a $4\pi$ solid angle, arising from dielectric structures external to the atomic measurement volume. Contributions to the measurement uncertainty from the fundamental atomic measurement method and associated analysis as well as material, geometry, and hardware design choices are accounted for. A calibration (C) factor is used to establish absolute-standard SI-traceable calibration of the RFP. Pulsed and modulated RF field measurement, and time-domain RF-pulse waveform imaging are also demonstrated.

Design of Ku-Band Flat Luneburg Lens Using Ceramic 3-D Printing

A flat Luneburg lens antenna for Ku-band (12-18 GHz) applications is proposed and designed using ceramic 3-D printing. Metamaterial structures and transformation optics technology are used to realize the gradient dielectric constant, compress the height, and reduce the weight of the Luneburg lens. The proposed 3-D printed Luneburg lens, combined with a 10 dB standard gain horn antenna, obtained an antenna gain up to 19.1 dBi over the operating frequency and the thickness reduction of 78%. In addition, the ability of the flat Luneburg lens to perform passive beam scanning with a limited power loss is achieved. This exploration of ceramic 3-D printing can serve as a reference for the development of ceramic components with complex structures.

Robotically‐controlled antenna measurement system for millimeter‐wave applications

AbstractThe characterization of antenna radiation patterns in millimeter‐wave (mmW) bands can be particularly challenging. Due to a small wavelength, minute misplacement of the probe antenna in the order of few millimeters can generate substantial errors in the measured pattern. A highly precise measurement system that incorporates a 6‐axis compact robotic arm is implemented to overcome this challenge. System testing shows a positional accuracy and repeatability of approximately 20 μm or 0.004λ at 60 GHz. After implementation, programming, and testing, the system is used to measure gain patterns on three different mmW antennas. The radiation pattern of a 50–75 GHz standard gain horn antenna demonstrated the accurate measurement at the far‐field using the robotically controlled system. Furthermore, the characterization of the center element pattern of a 60 GHz phased array has shown that the measurements with this system are repeatable and suitable for arrays as well. Additionally, we performed near‐field measurements by successfully characterizing a 40–60 GHz horn antenna with a planar scan.

Design and analysis of quad ridged horn antenna for high gain application

This paper discusses the design consideration of a Quad Ridged horn Antenna (QRHA). The different ridge profiles that are inserted in the horn have different significant effect on the horn performance that are discussed in the paper. The paper is based on the QRHA that can be used as a Standard Gain Horn Antenna. The QRHA is simulated using HFSS software and the results obtained are mentioned.

57-64 GHz Imaging/Detection Sensor–Part I: System Setup and Experimental Evaluations

A novel experimental evaluation of millimeter-wave imaging / detection system based on time domain reflectometry (TDR) is presented. The proposed 60 GHz-band system is characterized by high precision, lightweight, low profile, and utilization of low cost scanning probes. As a scanning sensor, multi sin-corrugation antipodal tapered slot antenna (MC-AFTSA-SC) with and without a grooved spherical probe is introduced. Although, the precise mechanical setup is especially designed and optimized to hold the proposed scanning probe antenna, it can handle a wide range of probes. The proposed antenna sensor is experimentally evaluated by integrating it in the proposed imaging / detection system. As a bench-marking process, multiple images for different targets are reconstructed using both the proposed probe and conventional standard gain horn (SGH) antenna. The images are generated using 2D linear scanning platform with a cross range resolution $\delta {x}=\delta {y}=3$ mm achieving a $100\times100$ pixels image. The obtained images indicate a superior performance of the proposed scanning probe over the bigger sized SGH. This paper is split into two parts because of its length: this paper (part I) describes the system setup and experimental evaluation of the probes, while part II will discuss experiments for detecting concealed weapons and threatening materials.

Reflection based Strain Sensing using Metamaterials

Resonator arrays of periodicially arranged electromagnetic sub-wavelength resonators show a strong frequency filter behaviour which can be controlled by the geometry, size and arrangement of the resonators. The use of several resonator arrays and their integration into a polymer matrix allows the realisation of metamaterials with a specific resonance behaviour. The resonance behaviour can be influenced by material and structural changes enabling a passive sensor function. The considered sensor approach based on metamaterials is investigated to enable structural health monitoring of lightweight structures. In the present case, a double-layer Jerusalem cross (JC) resonator array (RA) is integrated into a glass fibre reinforced plastic (GFRP) to analyse the change of the resonance behaviour under load (strain) using a reflection measurement. The CST (Computer Simulation Technology) Microwave Studio was used to model the resonator array for operation in the microwave frequency range between 15 GHz and 35 GHz as well as for the numerical analysis of the resonance behaviour under load. The numerical results were validated by a tensile test using a tensile test machine (type TIRATEST 28100, Tira GmbH) and by a reflection measurement using two standard gain horn antennas (type Standard Gain Horn Series 862, ARRA Inc) and a vector network analyser (type ZVA50, Rohde&amp;Schwarz). The reflection measurement shows a reflection minimum at 28.6 GHz which moves to higher frequencies under load of the GFRP laminate. With the shift of the minimum, the quality factor decreases and the dip widens. The investigation shows that it is possible to provide a GFRP laminate with a specific electromagnetic behaviour by integrating resonator arrays. It is also shown that the specific electromagnetic behaviour can be influenced by structural changes and thus opens up the possibility of monitoring the condition of lightweight structures.

Estimation of Gain of Antennas Integrated in Commercial Smartphones

Project-based learning is one of the most popular approaches to enhance the learning experience in technical courses. An example of project-based learning to augment “design of passive microwave components” course is presented in this paper. Conventional courses on antenna design would have an experimental verification by measuring a stand-alone antenna in an anechoic chamber. But, this approach lacks the real-world application and hence the estimation of gain of antenna integrated in a commercial smartphone is investigated in this paper. The smartphone is initially activated for a specific wireless service and used as a transmitter inside an anechoic chamber. A broadband standard gain horn antenna is used as a receiver which is connected to the spectrum analyzer. The power profile of the received signal is logged and used for estimating the gain. Various cases of this scenario are presented.

A Wideband and Low-Loss Spatial Power Combining Module for mm-Wave High-Power Amplifiers

We present a low-loss power combiner, providing a highly integrated interface from an array of mm-wave power amplifiers (PAs) to a single standard rectangular waveguide (WG). The PAs are connected to an array of parallel and strongly coupled microstrip lines that excite a substrate integrated waveguide (SIW) based cavity. The spatially distributed modes then couple from the cavity to the rectangular WG mode through an etched aperture and two stepped ridges embedded in the WG flange. A new co-design procedure for the PA-integrated power combining module is presented that targets optimal system-level performance: output power, efficiency, linearity. A commercial SiGe quad-channel configurable transmitter and a standard gain horn antenna were interfaced to both ends of this module to experimentally demonstrate the proposed power combining concept. Since the combiner input ports are non-isolated, we have investigated the effects of mutual coupling on the transmitter performance by using a realistic PA model. This study has shown acceptable relative phase and amplitude differences between the PAs, i.e. within ±15° and ±1 dB. The increase of generated output power with respect to a single PA at the 1-dB compression point remains virtually constant (5.5 dB) over a 42% bandwidth. The performed statistical active load variation indicates that the interaction between the PAs through the combiner has negligible effect on the overall linearity. Furthermore, the antenna pattern measured with this combiner shows negligible deformation due to non-identical PAs. This represents experimental prove-of-concept of the proposed spatial power combining module, which can be suitable for applications in MIMO array transmitters with potentially coupled array channels.

Measurement System for Millimeter-Wave Antennas With Distributed External Local Oscillators and Mixers

A measurement system for a millimeter-wave (mm-wave) antenna is presented here. The topologies of RF subsystems for antenna measurements are reviewed, and the optimum topology for a far-field antenna measurement range for mm-wave antennas is proposed. This topology minimizes the losses of both the Tx and local oscillator (LO) signal paths. In order to verify the proposed topology, a $W$ -band antenna measurement system for a fully anechoic chamber 10 ( $W$ ) m $\times \,\, 13$ ( $L$ ) m $\times \,\, 7.5$ ( $H$ ) m in size is designed and implemented. To provide the optimal LO input power, a test signal supply that compensates for the complicated losses in the LO signal path is also designed and implemented. The optimization procedure of the LO power is described. The performance of the $W$ -band antenna measurement system is evaluated by measuring the complex reflection coefficient and far-field gain of an electro-formed standard gain horn antenna. The measurement results are compared with intercomparison results between National Measurement Institutes. The results are shown to be within accepted uncertainty levels.

An antenna group delay measurement method based on three‐antenna extrapolation and least residual error curve fitting technique

AbstractThis article presents an antenna group delay (GD) measurement method based on the three‐antenna extrapolation technique and a least residual error curve fitting. The system GD is measured as a function of distances in an extrapolation range; then the antenna GD is determined together with antenna scattering characteristic (SC) defined by Kerns using GD variation curve fitting according to the measurement model and measured data. Measurement in frequency band of (1575.42 ± 16) MHz for a standard gain horn antenna is given, and the results of the antenna GD and SC at 1575.42 MHz are 2.83 ns and 0.36, respectively. The GD measurement results are with good agreement with our previously developed method, within a difference of 0.05 ns in the whole frequency band, and thus proposed method is cross‐checked. Although the proposed method is a little complicated and time consuming, its unique advantages are still prominent, as the optimization is a general solution for eliminating antenna multiple reflection; and the method can determine the two parameters of antenna GD and SC simultaneously.

Electronically Reconfigurable FSS-Inspired Transmitarray for 2-D Beamsteering

A novel electronically reconfigurable transmitarray (TA) with 2-D beamsteering capability is presented in this communication. The proposed structure, inspired on frequency selective surfaces loaded with varactor diodes, allows the phase range of each TA element to be individually controlled enabling an automated steering of the main lobe of an original antenna pattern, in both elevation and azimuth planes (2-D beamsteering). This has been demonstrated on a $5\times 5$ unit-cell stacked structure with active feeding, coupled to the aperture of a standard gain horn antenna. A complete electromagnetic study using CST Microwave Studio is presented to evaluate and characterize the TA elements and the effect the proposed feeding network has on the structure’s behavior. Following initial simulations, a prototype of the active TA has been characterized. Automated antenna beamsteering with ranges up to Az = 28° and El = 26° and 1° of angular resolution, is achieved by means of electromagnetic simulations and validated against experimental results at 5.2 GHz.

Electromagnetic Field Sensor Based on Atomic Candle

A new electromagnetic sensor using the atomic Rabi frequency is presented. Gaseous cesium-133 atoms enclosed in a compact glass cell work as an electromagnetic sensor by detecting the Rabi frequency. In this paper, we measured the electromagnetic field radiated from a standard gain horn antenna using the new sensor. This result was compared with a numerical simulation based on the method of moments. Both results were in good agreement. Moreover, a hypothesized reduction in electromagnetic perturbation caused by the glass cell was investigated using a numerical simulation.

Reflection and Transmission Properties of Common Construction Materials at 2.4 GHz Frequency

Having an adequate shielding from radiofrequency (RF) electromagnetic fields (EMFs) may serve many causes: to protect sensitive electronic equipment from outside interference; to protect the environment from the high radiation generating equipment; to protect humans from excess radiation etc. Strong RF EMFs may be encountered in public domain but especially in occupational settings, where the process and technology of work requires the usage of RF EMFs. Technical measures to reduce the levels of EMFs include using construction materials with attenuation properties. Generally three types of microwave behavior can be observed: transmission, reflection and absorption. In this study the radiofrequency reflection and transmission characteristics of common building materials were investigated. The investigated materials can broadly be divided into three groups: 1) load bearing materials – concrete, aerated concrete, LECA concrete; 2) thermal insulation materials - foamed polystyrene, mineral wool; 3) cover materials – gypsum based plates and wood dust/chips boards. The samples were square shaped, with the size of 300 x 300mm. The testing frequency was 2.4 GHz and the output power of the generator was 0 dBm. The study used three standard gain horn antennas for reflection and transmission measurements. The results show relatively good transmission properties for most of the materials. The least transmittance was measured in high performance concrete plate where only 34% of the waves penetrated the material and 35% were reflected off. Also with low transmission properties are gypsum board and oriented strand board. These materials were also measured to give low reflectance, 17% by both. Besides concrete, waterproof plywood and particleboard with veneer gave off somewhat reflections. Other materials exhibited very small reflection properties.