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Antenna chambers are RF‐shielded enclosures which are required for antenna and radio performance measurements. Typically, anechoic chambers (ACs) are used for measuring directional metrics (e.g. antenna pattern, effective isotropic power etc.), while reverberation chambers (RCs) are widely used for non‐directional measurements (e.g. antenna efficiency, total radiated power etc.). When a device under test requires both types of measurements, testing needs to be conducted sequentially in an AC and an RC. This leads to significant time inefficiencies due to the need to set up and calibrate two separate measurement setups in two different chambers. To address these issues, this letter proposes a programmable chamber framework capable of electronically switching between AC and RC modes by programming the reflective intelligent surface‐enabled sidewalls. This framework is highly attractive for the industry as it supports both directional and non‐directional measurements within a single chamber. The letter outlines the conceptual framework, discusses design considerations, and presents preliminary experimental validation of reflective intelligent surface‐enabled sidewall with the designed phase‐setting configurations to emulate the radio absorber sidewall of an AC and the metal plate sidewall of an RC. The experimental results demonstrate the effectiveness and potential of the proposed approach. [ABSTRACT FROM AUTHOR]

In this research, we present an innovative method for estimating the beams of array antennas. Traditional beam analysis methods rely on placing receiving antennas in the far-field region, which requires moving or rotating the Tx or Rx, and using radiation pattern measurements. However, such methods often demand vast spatial requirements and the use of high-cost network analyzers. In contrast, the technique proposed in this study utilizes a board patterned with coupling lines strategically placed in the antenna's near-field zone. Signals intercepted by these coupling lines undergo conversion into DC voltage via a power detector situated at the line terminus. Interestingly, this method enables beam estimation solely based on the DC voltage level output of the power detector, thus offering a cost-effective and space-efficient solution that represents a significant advancement from traditional beam estimation methods. [ABSTRACT FROM AUTHOR]

Automotive antennas are gaining importance due to their increasingly important role for autonomous driving with the development of the Internet of Vehicles. However, over‐the‐air testing on automotive antennas is difficult owing to its large volume and complex body structure. Plane wave generators can approximate uniform plane waves in the near field of the device under test, which can greatly reduce the measurement distance and thereby decreasing the cost compared with direct far‐field solutions. This letter designs three plane wave generators for three quiet zone sizes selected according to the vehicle structure at 5.9 GHz, achieving quiet zone sizes of 1.45 m ×0.23$\times 0.23$ m, 2.9m ×0.56$\times 0.56$ m, and 3.9 m ×1.27$\times 1.27$ m, respectively. Within the three quiet zones, amplitude deviations of 0.82, 0.34, and 0.34 dB and phase deviations of 9.4∘${9.4^\circ }$, 6.72∘${6.72^\circ }$ and 1.42∘${1.42^\circ }$ are realized, respectively, according to the numerical simulations. Uncertainty analysis is further implemented to investigate the robustness of the designed PWGs proposed in this letter. [ABSTRACT FROM AUTHOR]

This paper presents the description of antenna parameters related to its radiation/reception capabilities influenced by the plasma parameters in the environment surrounding the antenna, complementing the existing works on the antenna parameters (e.g., the impedance or currents). The parameters considered are the radiation zones' radiuses (inductive, Fresnel, Fraunhofer), scalloping and directivity; a method of transformation of the air/vacuum-measured radiation/reception pattern to the pattern expected for given plasmatic conditions is also considered. Three different simplified plasma conditions are taken into account (different electron densities: 1.4 × 1012 m−3, 4 × 1011 m−3 and 108 m−3), with varying antenna length (1 m, 10 m, 100 m) and signal propagation mode (classic-ionospheric, whistler and Alfvén). The findings show that the presented antenna parameters and its radiation/reception pattern are heavily dependent on the plasma conditions. These findings can be used to form additional requirements and constraints for the mechanical design of new instrumentation for space weather measurements on board spacecraft (e.g., moving the antennas away from the spacecraft in order not to alter their radiation/reception patterns or not to measure the plasma around the spacecraft) or more accurate data processing from existing space weather satellites, allowing, for example, a more precise triangulation of the signal source or its spectral power regarding the actual performance of the antennas submerged in plasma. [ABSTRACT FROM AUTHOR]

The integration of directive elements into a circular switched parasitic array at 868 MHz is presented. The typical usage of reflective parasitic monopoles is supplemented with additional, shorter monopole elements which are positioned closer to the central active monopole to induce directive behaviour. This allows for more degrees of freedom with the steering of the antennas beam and to increase the gain of the antenna. This leads to a greater flexibility of the system and enables power reduction of the amplifiers for enhanced battery life time. The design and configuration of a circular switched parasitic array with directive elements is shown and a prototype is built for validation. [ABSTRACT FROM AUTHOR]

Abstract Antenna chambers are RF‐shielded enclosures which are required for antenna and radio performance measurements. Typically, anechoic chambers (ACs) are used for measuring directional metrics (e.g. antenna pattern, effective isotropic power etc.), while reverberation chambers (RCs) are widely used for non‐directional measurements (e.g. antenna efficiency, total radiated power etc.). When a device under test requires both types of measurements, testing needs to be conducted sequentially in an AC and an RC. This leads to significant time inefficiencies due to the need to set up and calibrate two separate measurement setups in two different chambers. To address these issues, this letter proposes a programmable chamber framework capable of electronically switching between AC and RC modes by programming the reflective intelligent surface‐enabled sidewalls. This framework is highly attractive for the industry as it supports both directional and non‐directional measurements within a single chamber. The letter outlines the conceptual framework, discusses design considerations, and presents preliminary experimental validation of reflective intelligent surface‐enabled sidewall with the designed phase‐setting configurations to emulate the radio absorber sidewall of an AC and the metal plate sidewall of an RC. The experimental results demonstrate the effectiveness and potential of the proposed approach.

Abstract Ever‐increasing bandwidth requirements from various industries drive the need for the ever‐increasing bandwidth of antennas used for testing. Broadband Double‐Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state‐of‐the‐art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial‐to‐ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber‐filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented.

Ever‐increasing bandwidth requirements from various industries drive the need for the ever‐increasing bandwidth of antennas used for testing. Broadband Double‐Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state‐of‐the‐art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial‐to‐ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber‐filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented. [ABSTRACT FROM AUTHOR]

Abstract Automotive antennas are gaining importance due to their increasingly important role for autonomous driving with the development of the Internet of Vehicles. However, over‐the‐air testing on automotive antennas is difficult owing to its large volume and complex body structure. Plane wave generators can approximate uniform plane waves in the near field of the device under test, which can greatly reduce the measurement distance and thereby decreasing the cost compared with direct far‐field solutions. This letter designs three plane wave generators for three quiet zone sizes selected according to the vehicle structure at 5.9 GHz, achieving quiet zone sizes of 1.45 m ×0.23 m, 2.9m ×0.56 m, and 3.9 m ×1.27 m, respectively. Within the three quiet zones, amplitude deviations of 0.82, 0.34, and 0.34 dB and phase deviations of 9.4∘, 6.72∘ and 1.42∘ are realized, respectively, according to the numerical simulations. Uncertainty analysis is further implemented to investigate the robustness of the designed PWGs proposed in this letter.

Abstract The integration of directive elements into a circular switched parasitic array at 868 MHz is presented. The typical usage of reflective parasitic monopoles is supplemented with additional, shorter monopole elements which are positioned closer to the central active monopole to induce directive behaviour. This allows for more degrees of freedom with the steering of the antennas beam and to increase the gain of the antenna. This leads to a greater flexibility of the system and enables power reduction of the amplifiers for enhanced battery life time. The design and configuration of a circular switched parasitic array with directive elements is shown and a prototype is built for validation.

Abstract Since the total number of the antenna elements can be up to hundreds in a massive multiple‐input multiple‐output (MIMO) system, subarray‐structured base station (BS) array configurations are widely adopted to achieve a good cell coverage and to reduce the required number of radio frequency chains at the same time. It is crucial for any BS product to ensure that the antenna elements perform correctly as expected. Therefore, the necessity of array diagnosis is evident, especially for large BS arrays. Furthermore, it is essential that the diagnosis can be achieved in a compact and cost‐effective setup with high measurement efficiency (i.e. only a few measurement samples are required). The principle of the diagnosis method presented in this article is to obtain the S‐parameters between the subarrays and the probe via solving linear equations. In the simulation, a BS array composed of 16 subarrays with each containing 3 elements is used to validate the diagnosis method at 3.5 GHz. An array composed of 4 subarrays with each containing 3 elements was used in the measurements to verify the diagnosis method with two different phase tuning matrices at 3 GHz. Successful diagnosis results have been achieved in both the simulations and the measurements.

Abstract An effective, probe‐compensated, phaseless Near‐Field‐Far‐Field (NF–FF) transformation technique with planar spiral scanning is presented. The phase retrieval problem is solved by a quadratic inverse process, whose data are the voltage squared amplitudes of the NF samples acquired on two scanning surfaces. The available information on the antenna under test and on the scanning geometry are used to provide efficient representations for both the unknowns and the data, thus improving the accuracy and reliability of the technique. Furthermore, disconnected apertures are dealt with by adopting two different sets of prolate spheroidal wave functions to represent the aperture fields. Experimental results are reported to assess the effectiveness of the proposed approach. A drastic reduction (about 90%) of the required NF samples, as compared to standard λ/4 measurements (λ being the wavelength), is observed. Aggregating the measurements on the two scanning surfaces, the technique uses less samples even when compared to the case of complex, λ/2 measurements performed on a single surface. Our approach exhibits an accuracy comparable to that achieved when adopting complex measurements with non‐redundant sampling or classical, λ/2 plane‐rectangular NF–FF transformations.

Abstract This letter presents a comprehensive analysis of the radiation behaviour exhibited by nine distinct on‐wafer radio‐freqeuncy (RF) probes used for device characterization in the mm‐wave bands of integrated circuits and antennas. The tested probes are sourced from two different manufacturers and feature various probe pitches. All probes are intended for use with the WR‐3.4 waveguide band ranging from 220 to 330 GHz. To the best of the authors' knowledge, such a detailed examination of RF probes operating in this band with respect to their radiation behaviour has not been demonstrated before.

Since the total number of the antenna elements can be up to hundreds in a massive multiple‐input multiple‐output (MIMO) system, subarray‐structured base station (BS) array configurations are widely adopted to achieve a good cell coverage and to reduce the required number of radio frequency chains at the same time. It is crucial for any BS product to ensure that the antenna elements perform correctly as expected. Therefore, the necessity of array diagnosis is evident, especially for large BS arrays. Furthermore, it is essential that the diagnosis can be achieved in a compact and cost‐effective setup with high measurement efficiency (i.e. only a few measurement samples are required). The principle of the diagnosis method presented in this article is to obtain the S‐parameters between the subarrays and the probe via solving linear equations. In the simulation, a BS array composed of 16 subarrays with each containing 3 elements is used to validate the diagnosis method at 3.5 GHz. An array composed of 4 subarrays with each containing 3 elements was used in the measurements to verify the diagnosis method with two different phase tuning matrices at 3 GHz. Successful diagnosis results have been achieved in both the simulations and the measurements. [ABSTRACT FROM AUTHOR]

Abstract In millimetre wave (mmWave) frequency band, radio resource management (RRM) performance is characterised in plane wave conditions using radiated over‐the‐air test method, which is a challenging combination of protocol and radio frequency performance measurement. This article presents a novel design of multiple lens‐based compact antenna test ranges (CATRs) to simulate multiple angles of arrival from different base‐stations in RRM measurement. Only four lens‐based CATRs are proposed to create plane wave conditions at the device under test with six different angles of arrival and capable of accurately constructing the wireless propagation condition and minimising the diffraction and scattering between adjacent CATRs. The lens‐based CATR is the key element in the RRM measurement system, which is composed of a metasurface lens for phase alignment and a 2 × 2 feed array antenna for the emission of electromagnetic signals. The function and capability of the proposed lens‐based CATR is validated through simulation and measurement, that the worst‐case amplitude variation in the quiet zone region is lower than ±0.8 dB at 26 GHz, and phase variation is lower than ±7.5° in the designed quiet zone, which could be used in the fifth‐generation mmWave RRM measurement.

This letter presents a comprehensive analysis of the radiation behaviour exhibited by nine distinct on‐wafer radio‐freqeuncy (RF) probes used for device characterization in the mm‐wave bands of integrated circuits and antennas. The tested probes are sourced from two different manufacturers and feature various probe pitches. All probes are intended for use with the WR‐3.4 waveguide band ranging from 220 to 330 GHz. To the best of the authors' knowledge, such a detailed examination of RF probes operating in this band with respect to their radiation behaviour has not been demonstrated before. [ABSTRACT FROM AUTHOR]

An effective, probe‐compensated, phaseless Near‐Field‐Far‐Field (NF–FF) transformation technique with planar spiral scanning is presented. The phase retrieval problem is solved by a quadratic inverse process, whose data are the voltage squared amplitudes of the NF samples acquired on two scanning surfaces. The available information on the antenna under test and on the scanning geometry are used to provide efficient representations for both the unknowns and the data, thus improving the accuracy and reliability of the technique. Furthermore, disconnected apertures are dealt with by adopting two different sets of prolate spheroidal wave functions to represent the aperture fields. Experimental results are reported to assess the effectiveness of the proposed approach. A drastic reduction (about 90%) of the required NF samples, as compared to standard λ/4 measurements (λ being the wavelength), is observed. Aggregating the measurements on the two scanning surfaces, the technique uses less samples even when compared to the case of complex, λ/2 measurements performed on a single surface. Our approach exhibits an accuracy comparable to that achieved when adopting complex measurements with non‐redundant sampling or classical, λ/2 plane‐rectangular NF–FF transformations. [ABSTRACT FROM AUTHOR]

Canonical objects with known radar cross section (RCS), for example, the trihedral corner reflector (TCR), play a crucial role in the calibration of automotive radar sensors. Moreover, these canonical objects are also used in the validation of simulated RCS obtained using asymptotic methods, such as hybrid geometric optics (GO) and the physical optics (PO) based methods. However, accurate RCS prediction with asymptotic methods is highly dependent on the individual scattering mechanisms considered in a simulation, for example reflection and diffraction from the TCR surfaces and edges, respectively. Reliable measurements are therefore required to evaluate if a particular interaction mechanism can be neglected to reduce computation complexity without adversely affecting the accuracy of the predicted RCS. In this letter, the monostatic scattering characteristics of three metallic TCRs are investigated with varying geometrical sizes in the E‐band, that is, from 60 GHz to 90 GHz. The ultra‐wideband (UWB) measurements, which offer a high delay resolution, can enable the identification of the individual scattering mechanisms. Diffraction from the TCR edges is experimentally demonstrated to contribute to a non‐negligible scattered power in this frequency band. [ABSTRACT FROM AUTHOR]

In millimetre wave (mmWave) frequency band, radio resource management (RRM) performance is characterised in plane wave conditions using radiated over‐the‐air test method, which is a challenging combination of protocol and radio frequency performance measurement. This article presents a novel design of multiple lens‐based compact antenna test ranges (CATRs) to simulate multiple angles of arrival from different base‐stations in RRM measurement. Only four lens‐based CATRs are proposed to create plane wave conditions at the device under test with six different angles of arrival and capable of accurately constructing the wireless propagation condition and minimising the diffraction and scattering between adjacent CATRs. The lens‐based CATR is the key element in the RRM measurement system, which is composed of a metasurface lens for phase alignment and a 2 × 2 feed array antenna for the emission of electromagnetic signals. The function and capability of the proposed lens‐based CATR is validated through simulation and measurement, that the worst‐case amplitude variation in the quiet zone region is lower than ±0.8 dB at 26 GHz, and phase variation is lower than ±7.5° in the designed quiet zone, which could be used in the fifth‐generation mmWave RRM measurement. [ABSTRACT FROM AUTHOR]

The theoretical foundations of the near to far field transformation (NTFFT) techniques with spiral scannings have been properly applied to develop a non‐redundant spherical spiral NTFFT which properly accounts for a mounting of a volumetric antenna under test (AUT) in an offset configuration, due to any practical constraints. Such an NTFFT, based on the non‐redundant sampling representations of electromagnetic fields using spherical modelling of the AUT, requires the same number of near‐field (NF) spiral data when the AUT is mounted both in onset and offset configuration because this number depends only on the area of the modelling sphere centred at the AUT centre. Moreover, it employs an efficient two‐dimensional (2D) optimal sampling interpolation (OSI) formula to recover, from the spiral NF samples, the massive number of NF data required by the classical spherical NTFFT, which is related to the radius of the smallest sphere enclosing the AUT and centred at the scanning sphere centre. It is so possible to get a remarkable measurement time saving when the AUT is offset mounted. Numerical and experimental results, fully assessing the effectiveness of the developed NTFFT and the related 2D OSI algorithm, are shown. [ABSTRACT FROM AUTHOR]

This investigation primarily promotes a ultra-high frequency radiofrequency identification (RFID) tag antenna for complex environment applications of smart card in free space and near body scenarios. It also considers other high dielectric materials such as water and metallic objects. A dual dipole antenna with T-match structure is chosen due to the advantage of providing high resilience towards change in impedance of high dielectrics, and to ensure the reception of maximum signals at the blind spots of the antenna. The proposed geometry facilitates placement of other off-the-shelf high and low-frequency antennas on the card, enabling more features, higher performance, and minimum field interaction between different frequencies. A presented RLC equivalent circuit model estimates the impact of body layers on antenna impedance. A high read range of 7.7 m in free space, 5.2 m near body and 2.8 m at the blind spots is obtained. The novelty is shown by testing the antenna near metals and water, achieving high read range without any design modifications. The proposed tag aims to provide new RFID applications that demand small size, less volume, low cost and multifunctionality over various constraints while showing good agreement with sensitivity, impedance matching and the read range. [ABSTRACT FROM AUTHOR]

Anechoic chambers are widely used to measure antenna parameters because of the free reflection conditions inside them. Recently, there has been increasing research into antennas working at frequencies from 20 to 70 GHz. General-purpose anechoic chambers are usually between 5 and 10 m in size, which leads to free-space distances longer than required at millimeter-wave frequencies and corresponding larger cables losses. Designing anechoic chambers tailored to such a frequency range would lead to minimum losses and improve measurement performance. If uncertainty is considered all the way from the design stage to operation, it will be easier to obtain highly accurate measurement outcomes. This article focuses on the issues related to uncertainty in a tailor-made millimeter-wave anechoic chamber at every step before achieving a fully functional measurement system. This includes setting the requirements for the chamber, calculating its dimensions, designing the structure, and selecting the building materials, in order finally to characterize its performance by measuring the insulation from external signals and the ripple in the quiet zone. This process has resulted in a full description of design, construction, and operation stages of an anechoic chamber from the point of view of the control on the measurement uncertainty. [ABSTRACT FROM AUTHOR]

The classic method of testing array antenna is measuring the beam pattern separately, which suffers from low efficiency. In this study, a fast measurement method used for received array antenna has been present. Firstly, the patterns of element antennas have been tested using multi-channel receiver. Then the entire pattern could be computed by weighting the information of elements. The information contains amplitude and phase, which could be obtained by theory or measurement.

The classic method of testing array antenna is measuring the beam pattern separately, which suffers from low efficiency. In this study, a fast measurement method used for received array antenna has been present. Firstly, the patterns of element antennas have been tested using multi-channel receiver. Then the entire pattern could be computed by weighting the information of elements. The information contains amplitude and phase, which could be obtained by theory or measurement. [ABSTRACT FROM AUTHOR]

A method to filter out the contribution of interference sources in array diagnosis is proposed. The interference-affected near field measured on a surface is treated as a (complex-data) image. This allows to use some modern image processing algorithms. In particular, two strategies widely used in image processing are applied. The first one is the reduction of the amount of information by acquiring only the innovation part of an image, as currently happens in video processing. More specifically, a differential measurement technique is used to formulate the estimation of the array excitations as a sparse recovery problem. The second technique has been recently proposed in video denoising, where the image is split into a low-rank and high-rank part. In particular, in this paper the interference field is filtered out using sparsity as discriminant adopting a mixed minimum '1 norm and trace norm minimization algorithm. The methodology can be applied to both near and far field measurement ranges. It could be an alternative to the systematic use of anechoic chambers for antenna array testing. [ABSTRACT FROM AUTHOR]

A method to filter out the contribution of interference sources in array diagnosis is proposed. The interference-affected near field measured on a surface is treated as a (complex-data) image. This allows to use some modern image processing algorithms. In particular, two strategies widely used in image processing are applied. The first one is the reduction of the amount of information by acquiring only the innovation part of an image, as currently happens in video processing. More specifically, a differential measurement technique is used to formulate the estimation of the array excitations as a sparse recovery problem. The second technique has been recently proposed in video denoising, where the image is split into a low-rank and high-rank part. In particular, in this paper the interference field is filtered out using sparsity as discriminant adopting a mixed minimum ℓ 1 norm and trace norm minimization algorithm. The methodology can be applied to both near and far field measurement ranges. It could be an alternative to the systematic use of anechoic chambers for antenna array testing.

The authors present a test method for quantifying and reducing systematic errors arising from antenna proximity to lossy objects in over‐the‐air performance testing of lossy large‐form‐factor wireless devices. The method determines the extent to which antenna proximity to lossy, large‐form‐factor objects influences the measured reference power transfer function. The test may be used to pre‐characterise a given chamber set‐up in terms of a minimum distance between antennas and lossy objects. They illustrate the use of the method in a total radiated power measurement of a large, commercially available, machine‐to‐machine device, where agreement to anechoic‐chamber measurements is demonstrated to within the measurement uncertainty. [ABSTRACT FROM AUTHOR]

Measurements in reverberation chamber (RC) produce data that are random, and therefore they need to be processed from the statistical point‐of‐view for obtaining the desired characteristics and the accuracy. The complex channel transfer function in the RC follows complex Gaussian distribution provided that the RC is well stirred. The authors have recently presented a new uncertainty model based on the presence of an unstirred component of the transfer function, which was modelled by introducing an average Rician K‐factor. The model was validated in two RCs with translating mode‐stirring plates, being able to correctly describe the improvement in accuracy by rotating the antenna under test, and by blocking the line‐of‐sight between this and the fixed RC antenna(s). In the present study, they apply this uncertainty model to four RCs with different settings (e.g. RC volumes, number of plates or fixed RC antennas, translating and rotating mode‐stirrers etc.). For each RC, they examine the measurement uncertainty under different loading conditions. To repeat (during the different measurements) the actual mode‐stirrer positions at which the transfer function is sampled, they conduct all the measurements with stepwise (instead of continuous) mode‐stirring. The model is shown to work well for all the cases. [ABSTRACT FROM AUTHOR]

A technique for array diagnosis using a small number of measured data acquired by a near-field system is proposed. The technique, inspired by some recent results in the field of compressed sensing, requires the preliminary measurement of a failure-free reference array. The linear system relating the difference between the field measured using the reference array and the field radiated by the array under test, and the difference between the coefficients of the reference and of the AUT array, is solved using a proper regularization procedure. Numerical examples confirm that the technique gives satisfactory results in terms of failure detection with a reduction in the number of data of two orders of magnitudes compared to standard back-propagation technique and of one order of magnitude compared to the number of elements of the array, provided that the number of fault elements is small. This result is relevant in practical applications, since the high cost of large array diagnosis in near-field facilities is mainly caused by the time required for the data acquisition. Accordingly, the technique is particularly suitable for routine testing of arrays. [ABSTRACT FROM PUBLISHER]

In this Letter, a tri‐reflector compact antenna test range (CATR) with a paraboloidal main reflector and two shaped sub‐reflectors is synthesised by the kinematic and dynamic ray tracing method, while the high cross‐polarisation isolation is achieved through the proposed system geometry. Numerical simulations by general responsibility assignment software patterns demonstrate that a cross‐polarisation isolation >40 dB and a peak‐to‐peak amplitude (phase) ripple <1 dB (10°) can be achieved on the principal cuts of the designed quiet zone at 90–325 GHz. This clearly shows that the high cross‐polarisation isolation in such a tri‐reflector CATR can be achieved by the proposed antenna geometry without depolarisation control in the shaping procedure. [ABSTRACT FROM AUTHOR]

A planar super‐wideband (SWB) antenna fed by an asymmetric coplanar strip is proposed, fabricated, and tested. The antenna consists of a hexagonal loop strip in which a signal strip is prolonged, curved, and shorted to a ground plane to facilitate SWB characteristics. In addition, by adding a boomerang‐shaped strip to the ground plane, the effective electrical length is increased, thereby decreasing the lowest operating frequency. The simulated results show that the proposed antenna exhibits a −10 dB reflection bandwidth from 1.18 to 49.22 GHz corresponding to a ratio bandwidth of 41.7:1. The measured results of the fabricated antenna are also represented and compared with the simulated results. The antenna gain changes from 2.05 to 10.62 dBi within the measured frequency range. [ABSTRACT FROM AUTHOR]

A comparison between different modern heuristic optimization methods applied to antenna far-field radiation pattern reconstruction from planar near-field data is presented in this paper. The antenna under test is represented by means of equivalent magnetic currents (EMC) whose components are optimized using several heuristic algorithms such as simulated annealing (SA), genetic algorithms (GA), and particle swarm optimization (PSO), as well as a traditional local optimization method, the Nelder Mead downhill simplex algorithm. Several schemes for GA (classical real-valued and binary encoding, and their hybrid versions) and PSO (global or local topologies with synchronous or asynchronous updates of the swarm) have been considered in the analysis and the pros and cons of each one are reported and discussed. A study of the performance and limitations of each algorithm using as a canonical problem a small size antenna aperture, along with results of near-field to far-field (NF-FF) transformation are also included [ABSTRACT FROM PUBLISHER]

With the proliferation of wireless devices in recent years, there is a growing need to test the operation and functionality of these various devices in different multipath environments, ranging from line-of-sight environment to a pure Rayleigh environment. In this paper we discuss how a reverberation chamber can be used to simulate a controllable Rician radio environment for the testing of a wireless device. We show that by varying the characteristics of the reverberation chamber and/or the antenna configurations in the chamber, any desired Rician K-factor can be obtained. Expressions for the desired K-factor as a function of the chamber and antenna characteristics will be presented. Experimental results are presented to illustrate the validity of these expressions, to show how the reverberation chamber can be used to simulate different multipath environments, and to show the realization of a controlled K-factor test facility. We present both a one-antenna and a two-antenna test configuration approach [ABSTRACT FROM PUBLISHER]

By supporting an L-probe coupled circular patch antenna with four metallic posts at appropriate locations, it is demonstrated that the conical and the broadside modes which are excited separately by two different sets of L-shaped probes, can be operated at the same frequency range. For a tested antenna operated at 1.85 GHz, the bandwidth (SWR<2) achieved is 24%, and the isolation between the two input ports is 28 dB. The gains of the conical and broadside modes are 4 and 8.5 dBi, respectively. With suitable switching feed networks, the antenna can be reconfigurable in radiation pattern. The antenna can also be used as a pattern diversity antenna for modern mobile communications. [ABSTRACT FROM PUBLISHER]

A tunable, electrically small, wire antenna is developed for HF/VHF ground wave transmission. A variable capacitor is serially connected to tune the resonant frequency of the antenna. The optimal position for the placement of the capacitor is evaluated by numerical simulation. The tuning range and sensitivity are also investigated. A prototype antenna is built and tested, and the measured tuning performance is compared to the simulation results. Transmission loss tests are carried out in several nonline-of-sight environments. The measured transmission loss of the tunable small antenna is found to be within 1 to 2 dB of that of a commercial whip across the tested frequency range. [ABSTRACT FROM PUBLISHER]

A quick review of the planar phaseless near‐field antenna measurement technique is presented and some interesting aspects related to the size of the mask used at the aperture of the antenna under test (AUT) are pointed out. It is shown simulatively and experimentally that due to the edge fields the AUT aperture's mask needs to be larger than the physical aperture of the AUT to achieve better accuracy. In addition, the misalignment of the setup has a big impact on the achieved far‐field accuracy. This is emphasised experimentally. [ABSTRACT FROM AUTHOR]

A novel and simple approach to adjust the polarisation properties of a microstrip patch antenna in the entire axial ratio (AR) range is proposed. The proposed antenna consists of a radiating patch and a parasitic strip separated into two parts, and the separated strip is placed at the outer perimeter of the patch for capacitive coupling. This structure enables the antenna to induce opposite‐direction currents on the strip, which allows flexible polarisation adjustment by moving the separated positions of the strip. For evaluation, two antennas with linear and circular polarisations are fabricated, and their performance is measured in a full anechoic chamber. The results prove that the proposed approach is suitable for flexible AR adjustment without a significant degradation of the matching characteristics and the design complexity. [ABSTRACT FROM AUTHOR]

The authors have developed a flow-phantom model in order to measure the temperature profile of radiofrequency (RF) and microwave (MW) catheters. The model consists of a muscle equivalent phantom in a perfusion chamber with constant saline infusion of 4 L/min immersed in a 37/spl deg/C saline bath, RF (4 or 8 mm, 550 kHz) or MW (12 mm helical antenna, 915 MHz) catheters were placed on the surface of the phantom and various energies were applied. Temperature measurements were obtained with fiberoptic thermometry probes placed at various distances from the catheter. Temperature contours were generated, and lesion volumes were estimated using 47/spl deg/C isotherm (/spl Delta/T 10/spl deg/C). The dosimetry of power versus /spl Delta/T was linear. A 2.59 fold increase in power density was required to achieve a similar surface temperature with the 8 mm versus 4 mm electrode tip. The volumes of lesions created with an 8 mm electrode were 2.5/spl times/ larger than those made with a 4 mm electrode at a similar surface temperature. The RF phantom data compared favorably with the lesion volumes seen in the in vivo canine left ventricular model. The temperature profile of the microwave electrode showed heating along the length of the catheter due to imperfect tuning of the antenna. Deeper heating was seen with 8 mm RF and MW electrodes than with an RF 4 mm electrode given the same surface temperature. Measurements obtained with both a static and flow-phantom model demonstrated the cooling effects of flow on surface temperature measured during power delivery. Conclusions: The flow-phantom model accurately predicts the lesion geometry but underestimates the lesion volume at higher temperature when compared to the in vivo left ventricular canine model. Static phantom models will overestimate lesion size due to the surface cooling effects of cardiac blood flow. Changes in microwave catheter design may be carefully analyzed with the flow-phantom model prior to in vivo testing. [ABSTRACT FROM AUTHOR]

In this paper the problem of sampling the field radiated by a planar source observed over a finite planar aperture located in the near-field is addressed. The problem is cast as the determination of the spatial measurement positions which allow us to discretize the radiation problem so that the singular values of the radiation operator are well-approximated. More in detail, thanks to a suitably warping transformation of the observation variables, the kernel function of the relevant operator is approximated by a band-limited function and hence the sampling theorem applied to achieved discretization. It results in the sampling points having to be non-linearity arranged across the measurement aperture and their number can be considerably lowered as compared to more standard sampling approach. It is shown that the proposed sampling scheme works well for measurement apertures that are not too large as compared to the source's size. As a consequence, the method appears better suited for broad-side large antenna whose radiated field is mainly concentrated in front of the antenna. A numerical analysis is included to check the theoretical findings and to study the trade-off between the field accuracy representation (over the measurement aperture) and the truncation error in the estimated far-field radiation pattern. [ABSTRACT FROM AUTHOR]

In this paper, we describe the design of an electrically large anechoic chamber for usage on millimetre-wave bands. Ansys Savant sotware was used to perform a simulation of the chamber, using physical optics coupled with uniform theory of diffraction (PO/UTD). Moreover, a method based on an open waveguide probe is described in this paper to obtain the electrical properties of the RF absorbers at millimetre-wave frequencies. Two different source antennas were simulated in this work and the corresponding quiet zones predicted. The largest quiet zone was 30 m m × 30 m m × 50 m m , for a chamber size of 1.2 m m × 0.6 m m × 0.6 m . [ABSTRACT FROM AUTHOR]

A beam‐deflection short backfire antenna (BD‐SBA) is proposed. The BD‐SBA consists of an SBA and a deflection plate. The deflection plate is designed to change the phase of the reflected waves, hence deflecting the beam of the BD‐SBA. The beam deflection can realise different beam pointing within about 20°. An X‐band antenna (10 GHz) with a beam pointing of 12° is fabricated and tested. The measured results demonstrate that the desired beam deflection is obtained. A gain of 14.3 dBi and a sidelobe level of −20.6 dB are realised. The BD‐SBA, with a simple structure, low cost and moderately high gain, is suitable for the application of fifth‐generation wireless backhauling potentially. [ABSTRACT FROM AUTHOR]