From the material presented here, it is clear that the theory underlying the SNF approach is complex and involved to implement. However, it is also very elegant and provides one with many measurement options and powerful capabilities. The numerical implementation of the theory can be efficiently deployed through the use of the fast Fourier transform (FFT) enabling transforms of even electrically large antennas to be accomplished in a matter of a few seconds on a modern powerful digital computer. With the advent of commercially available SNF test systems, the user can exploit these techniques, largely unimpeded by the burden of the theory or the implementation thereof. The material presented here highlighted some of the fundamental concepts and limitations the user needs to be aware of in order to use these test systems with confidence.

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Spherical near-field antenna measurements

We present a promising application of the inverse source technique for antenna diagnostics and the creation of a synthetic higher-performance measurement environment. The focus is on the post-processing of antenna measurements via the recently introduced dual-equation formulation of the inverse source problem, which provides the equivalent sources with highest correlation to actual radiators among the infinite possible choices of equivalence. It is shown how, in practically relevant conditions, measured data can be spatially filtered in the source domain to recover reference conditions not achievable during measurements, e.g., perfectly balanced antenna feeding and absence of supporting structure. The procedure proposed is useful also in the detection, synthetic elimination, and actual correction of the effect of undesired interactions with scatterers in the measurement volume, such as the supporting platform and surrounding obstacles.

Suppression of Undesired Radiated Fields Based on Equivalent Currents Reconstruction From Measured Data

Wide-angle coverage, fine angular resolution, and low-power consumption are the key characteristics of millimeter-wave short-range wireless systems, such as access points in fifth-generation cellular networks and automotive radars. In this paper, we present a 60 GHz switched-beam antenna system addressing all these requirements. It consists of two identical parallel-fed arrays of eight slots, each fed by a passive pillbox beamformer. A switch network comprising four single-pole-multiple-throw switches excites one of the two arrays at a time and selects the radiated beam. The whole system is fully integrated into a multilayer low-temperature cofired ceramic module. The antenna covers a scan range of about ±39° in one plane using 11 beams between 57 and 66 GHz. The proposed architecture enables the simultaneous achievement of continuous coverage (beam crossover levels of about −3 dB) and of low sidelobe levels. Dedicated numerical tools are used for a preliminary design of the antenna. The design procedure, the technological development, and the experimental results are discussed in detail.

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A Wide-Angle Scanning Switched-Beam Antenna System in LTCC Technology With High Beam Crossing Levels for V-Band Communications

This study proposes a compact dual-polarised directive radiator whose complex prototyping is enabled by additive manufacturing. In addition to monolithic implementation, stereolitography followed by metal coating, it also provides high radio-frequency performance, low cost and low weight. Dual-channel simultaneous operation is supported thanks to the integration of an orthomode transducer within the structure. Entirely waveguide based, this compound radiating structure is specially well suited to be 3D-printed, and in principle, it allows scaling to match a specific frequency of operation. Both the antenna concept and the employed advanced manufacturing technique are validated experimentally through the realisation and measurement of two prototypes operating, respectively, at 30 and 60 GHz. The proposed architecture is easily amenable to be grouped in a compact higher-gain array, thus holding strong potential for platform-constrained applications, such as inter-satellite links between CubeSats.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2016.0950

Cost-effective dual-polarised leaky-wave antennas enabled by three-dimensional printing

In order to incorporate different communication standards into a single device, a compact quad-band slot antenna is proposed in this paper. The proposed antenna is composed of a dielectric substrate, T-shaped microstrip patch with a circle slot and an inverted L-slot, and a comb-shaped ground on the back of the substrate. By adopting these structures, it can produce four different bands, while maintaining a small size and a simple structure. Furthermore, a prototype of the quad-band antenna is designed and fabricated. The simulated and measured results show that the proposed antenna can operate over the 1.79–2.63 GHz, 3.46–3.97 GHz, 4.92–5.85 GHz, and 7.87–8.40 GHz, which can cover entire PCS (Personal Communications Service, 1.85–1.99 GHz), UMTS (Universal Mobile Telecommunications System, 1.92–2.17 GHz), WCDMA (wideband code-division multiple access, 2.1 GHz), Bluetooth (2.4–2.48 GHz), WiBro (Wireless Broad band access service, 2.3–3.39 GHz), WLAN (Wireless Local Area Networks, 2.4/5.2/5.8 GHz), WiMAX (Worldwide Interoperability for Microwave Access, 2.5/3.5/5.5 GHz), and X-band SATcom applications (7.9~8.4 GHz). The proposed antenna is particularly attractive for mobile devices integrating multiple communication systems.

/pdf/design-of-a-compact-quad-band-slot-antenna-for-integrated-19nx9yrfia.pdf

Design of a Compact Quad-Band Slot Antenna for Integrated Mobile Devices

A fast spherical near-field to far-field transformation using single cuts is introduced in this paper. It is based on calculating the Cylindrical Modal Coefficients of each individual near-field ring and processing them independently, considering them as cylinders of zero height and applying probe correction. The reconstruction of each far-field cut is obtained through an inverse Fast Fourier Transform. This procedure provides the opportunity to perform real time transformations due to its low acquisition and processing time. It is a useful tool for applications which do not require a full or accurate characterization, such as measuring the main patterns of an antenna or its most important parameters (peak gain, beam width, side lobe level, etc.).

/pdf/a-fast-single-cut-spherical-near-field-to-far-field-s6d6yd3i39.pdf

A fast single cut spherical near-field-to-far-field transformation using Cylindrical Modes

A method to reduce the noise power in a far-field pattern without modifying the desired signal is proposed. An important signal-to-noise-ratio improvement may thereby be achieved. The method is used when the antenna measurement is performed in the planar near-field, where the recorded data are assumed to be corrupted with white Gaussian and space-stationary noise, because of the receiver's additive noise. Back-propagating the measured field from the scan plane to the plane of the antenna under test (AUT), the noise remains white Gaussian and space-stationary, whereas the desired field is theoretically concentrated in the aperture antenna. Thanks to this fact, a spatial filtering may be applied, canceling the field that is located out of the AUT's dimensions and that is only composed of noise. Next, a planar-field-to-far-field transformation is carried out, achieving a great improvement compared to the pattern obtained directly from the measurement. To verify the effectiveness of the method, two examples are presented using both simulated and measured near-field data.

/pdf/novel-method-to-improve-the-signal-to-noise-ratio-in-far-5gubiv59oo.pdf

Novel Method to Improve the Signal-To-Noise Ratio in Far-Field Results Obtained from Planar Near-Field Measurements

In this paper, four new applications of sources reconstruction techniques (also called diagnostic techniques) are presented. First of all, the important information of such techniques will be mentioned, seeing that they are a tool to obtain the extremely near field from the measured data. Depending on the region where these data are taken (near field or far field), the reconstruction method will be different. Also, all of them may be classified in other two groups depending on its features: Integral Equation Methods (IEM) or Modal Expansion Methods. Classical applications of such techniques are errors detection, like phase errors in arrays or conformai errors in reflectors, therefore, they constitute an important antenna design tool. But also and it has been said, they can be used as the basis to other applications whose aim is to improve the measurement results in anechoic chambers or non anechoic environments. Here, four of them are presented, being the reflection cancelling, the detection of unwanted radiation points, the truncation error reduction in planar or cylindrical near-field and the noise reduction.

/pdf/applications-of-sources-reconstruction-techniques-theory-and-2t9aqbokfb.pdf

Applications of sources reconstruction techniques: Theory and practical results

In order to improve its capabilities in measuring millimeter-wave antennas, the Institute of Electronic and Telecommunications of Rennes has implemented a Compact Antenna Test Range (CATR) in one of its anechoic chamber. This paper describes the main lines of this project, from the technical requirements to the verification of the CATR performances. Measurements of the Quiet Zone (QZ) in V-band are presented to show the performances of this equipment.

https://hal-univ-rennes1.archives-ouvertes.fr/hal-01380055/document

IETR millimeter-wave Compact Antenna Test Range implementation and validation

This paper deals with the upgrade of the ESTEC Compact Payload Test Range (CPTR) [1] to ensure that its capability in terms of measurement accuracy and frequency domain is adequate for complementing the ESTEC test centre facilities with state of the art antenna testing as requested by space projects. A near-field scanner has been incorporated in the existing ESA CPTR to establish a Hybrid Test Range in the frequency range from 400 MHz to 50 GHz. The main goals of this RF system upgrade are to increase the operational frequency range, to easy exchange the DUT transmit and receive modes and to improve the dynamic range. The system features are presented in this paper.

Sara Burgos

Papers

A fast single cut spherical near-field-to-far-field transformation using Cylindrical Modes

Novel Method to Improve the Signal-To-Noise Ratio in Far-Field Results Obtained from Planar Near-Field Measurements

Applications of sources reconstruction techniques: Theory and practical results

IETR millimeter-wave Compact Antenna Test Range implementation and validation

Near-field Hybrid Test Range from 400 MHz to 50 GHz in the ESTEC Compact Payload Test Range with RF upgrade for high frequencies