Research

10 pages, 2848 KiB

Open AccessCommunication

Rapid Test Method for Multi-Beam Profile of Phased Array Antennas

by Qingchun Luo, Yantao Zhou, Yihong Qi, Pu Ye, Francesco de Paulis and Lie Liu

Sensors 2022, 22(1), 47; https://0-doi-org.brum.beds.ac.uk/10.3390/s22010047 - 22 Dec 2021

Cited by 1 | Viewed by 2351

The measurement of the phased array antenna (PAA) is completely different from the traditional antenna, due to its multi beam patterns. Usually, each beam pattern of the PAA needs a separate measurement, which makes the overall time extremely long. Thus, the traditional method [...] Read more.

The measurement of the phased array antenna (PAA) is completely different from the traditional antenna, due to its multi beam patterns. Usually, each beam pattern of the PAA needs a separate measurement, which makes the overall time extremely long. Thus, the traditional method can no longer meet the efficiency and cost requirements of new PAA measurement. In this paper, a pattern reconstruction method is proposed which significantly reduce the measurement time of multi-beam PAAs. With the known array element patterns (AEP) and theoretical weighted port excitation of the beams, any beam pattern can be predicted by measuring only a certain beam pattern, due to the element excitation coefficient (including the matching, mutual coupling, and manufacturing factors, etc.) of the specific PAA being calculated. The approach has low reconstruction error in term of beam pointing accuracy, side lobe, and co-polar and cross-polar patterns while being validated for large scanning range. Through theoretical derivation and experiments, the effectiveness of the method is verified, and the testing efficiency of the phased array antenna can be improved by 10 times or even more. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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18 pages, 6504 KiB

Open AccessArticle

Reconstruction of Relative Phase of Self-Transmitting Devices by Using Multiprobe Solutions and Non-Convex Optimization

by Rubén Tena Sánchez, Fernando Rodríguez Varela, Lars J. Foged and Manuel Sierra Castañer

Sensors 2021, 21(7), 2459; https://0-doi-org.brum.beds.ac.uk/10.3390/s21072459 - 02 Apr 2021

Cited by 6 | Viewed by 1459

Abstract

Phase reconstruction is in general a non-trivial problem when it comes to devices where the reference is not accessible. A non-convex iterative optimization algorithm is proposed in this paper in order to reconstruct the phase in reference-less spherical multiprobe measurement systems based on [...] Read more.

Phase reconstruction is in general a non-trivial problem when it comes to devices where the reference is not accessible. A non-convex iterative optimization algorithm is proposed in this paper in order to reconstruct the phase in reference-less spherical multiprobe measurement systems based on a rotating arch of probes. The algorithm is based on the reconstruction of the phases of self-transmitting devices in multiprobe systems by taking advantage of the on-axis top probe of the arch. One of the limitations of the top probe solution is that when rotating the measurement system arch, the relative phase between probes is lost. This paper proposes a solution to this problem by developing an optimization iterative algorithm that uses partial knowledge of relative phase between probes. The iterative algorithm is based on linear combinations of signals when the relative phase is known. Phase substitution and modal filtering are implemented in order to avoid local minima and make the algorithm converge. Several noise-free examples are presented and the results of the iterative algorithm analyzed. The number of linear combinations used is far below the square of the degrees of freedom of the non-linear problem, which is compensated by a proper initial guess. With respect to noisy measurements, the top probe method will introduce uncertainties for different azimuth and elevation positions of the arch. This is modelled by considering the real noise model of a low-cost receiver and the results demonstrate the good accuracy of the method. Numerical results on antenna measurements are also presented. Due to the numerical complexity of the algorithm, it is limited to electrically small- or medium-size problems. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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15 pages, 6156 KiB

Open AccessArticle

Different Metrics for Singular Value Optimization in Near-Field Antenna Characterization

by Amedeo Capozzoli, Claudio Curcio and Angelo Liseno

Sensors 2021, 21(6), 2122; https://0-doi-org.brum.beds.ac.uk/10.3390/s21062122 - 18 Mar 2021

Cited by 7 | Viewed by 1762

Abstract

We deal with the use of different metrics in the framework of the Singular Value Optimization (SVO) technique for near-field antenna characterization. SVO extracts the maximum amount of information on an electromagnetic field over a certain domain from field samples on an acquisition [...] Read more.

We deal with the use of different metrics in the framework of the Singular Value Optimization (SVO) technique for near-field antenna characterization. SVO extracts the maximum amount of information on an electromagnetic field over a certain domain from field samples on an acquisition domain, with a priori information on the source, e.g., support information. It determines the field sample positions by optimizing a functional featuring the singular value dynamics of the radiation operator and representing a measure of the information collected by the field samples. Here, we discuss in detail and compare the use, in the framework of SVO, of different objective functionals and so of different information measures: Shannon number, mutual information, and Fisher information. The numerical results show that they yield a similar performance. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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16 pages, 23817 KiB

Open AccessArticle

Multi-Probe Measurement System Based on Single-Cut Transformation for Fast Testing of Linear Arrays

by Fernando Rodríguez Varela, Manuel José López Morales, Rubén Tena Sánchez, Alfonso Tomás Muriel Barrado, Elena de la Fuente González, Guillermo Posada Quijano, Carlos Zarzuelo Torres, Manuel Sierra Pérez and Manuel Sierra Castañer

Sensors 2021, 21(5), 1744; https://0-doi-org.brum.beds.ac.uk/10.3390/s21051744 - 03 Mar 2021

Cited by 4 | Viewed by 2103

Abstract

This paper introduces a near-field measurement system concept for the fast testing of linear arrays suited for mass production scenarios where a high number of nominally identical antennas needs to be measured. The proposed system can compute the radiation pattern, directivity and gain [...] Read more.

This paper introduces a near-field measurement system concept for the fast testing of linear arrays suited for mass production scenarios where a high number of nominally identical antennas needs to be measured. The proposed system can compute the radiation pattern, directivity and gain on the array plane, as well as the array complex feeding coefficients in a matter of seconds. The concept is based on a multi-probe antenna array arranged in a line which measures the near field of the antenna under test in its array plane. This linear measurement is postprocessed with state-of-the-art single-cut transformation techniques. To compensate the lack of full 3D information, a previous complete characterization of a “Gold Antenna” is performed. This antenna is nominally identical to the many ones that will be measured with the proposed system. Therefore, the data extracted from this full characterization can be used to complement the postprocessing steps of the single-cut measurements. An X-band 16-probe demonstrator of the proposed system is implemented and introduced in this paper, explaining all the details of its architecture and operation steps. Finally, some measurement results are given to compare the developed demonstrator with traditional anechoic measurements, and show the potential capabilities of the proposed concept to perform fast and reliable measurements. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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12 pages, 4886 KiB

Open AccessArticle

Reconstruction of the Far-Field Pattern of Volumetric AUTs from a Reduced Set of Near-Field Samples Collected along a Planar Spiral with a Uniform Step

by Francesco D’Agostino, Flaminio Ferrara, Claudio Gennarelli, Rocco Guerriero, Massimo Migliozzi and Giovanni Riccio

Sensors 2021, 21(5), 1644; https://0-doi-org.brum.beds.ac.uk/10.3390/s21051644 - 26 Feb 2021

Cited by 1 | Viewed by 1517

Abstract

An efficient near-to-far-field transformation (NTFFT) technique, wherein the near-field (NF) measurements are acquired along a planar spiral with a uniform step to make the control of the involved positioners easier, is developed in this article. Such a technique is tailored for quasi-spherical, i.e., [...] Read more.

An efficient near-to-far-field transformation (NTFFT) technique, wherein the near-field (NF) measurements are acquired along a planar spiral with a uniform step to make the control of the involved positioners easier, is developed in this article. Such a technique is tailored for quasi-spherical, i.e., volumetric, antennas under test and makes use of a reduced number of NF data. An effective two-dimensional sampling interpolation algorithm, allowing the accurate reconstruction of the input NF data for the standard NTFFT with plane-rectangular scan, is obtained by setting the spiral step equal to the sample spacing required for interpolating along a radial line according to the spatial bandlimitation properties of electromagnetic fields, and by properly developing a non-redundant representation along such a spiral. Tests results are reported to demonstrate that the proposed NTFFT technique retains the same accuracy as the standard plane-rectangular one. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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11 pages, 3039 KiB

Open AccessCommunication

Some Contributions for Antenna 3D Far Field Characterization at Terahertz

by Laurent Le Coq, Nicolas Mézières, Paul Leroy and Benjamin Fuchs

Sensors 2021, 21(4), 1438; https://0-doi-org.brum.beds.ac.uk/10.3390/s21041438 - 19 Feb 2021

Cited by 3 | Viewed by 2383

Abstract

The three-dimensional (3D) characterization of antenna far field patterns at terahertz frequencies is addressed. This task is challenging, because the phase of the electric field is difficult to measure accurately and reliably. From the sub-millimeter wave range, the small wavelength indeed significantly increases [...] Read more.

The three-dimensional (3D) characterization of antenna far field patterns at terahertz frequencies is addressed. This task is challenging, because the phase of the electric field is difficult to measure accurately and reliably. From the sub-millimeter wave range, the small wavelength indeed significantly increases the impact of mechanical and electrical errors. Models and procedures to estimate these errors are proposed to mitigate their effects. The 3D far field patterns of a circularly polarized horn measured at 300 GHz and a multibeam pillbox antenna at 270 GHz are shown. The agreement between the 3D measurements and the two-dimensional (2D) patterns of reference as well as the radiated pattern before and after correction demonstrates the interest of the proposed approach and experimentally validate the proposed error estimation procedures. The methodology can be applied to direct far field measurement facilities as well as compact antenna test ranges. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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18 pages, 6226 KiB

Open AccessArticle

Design, Implementation, and Measurement Procedure of Underwater and Water Surface Antenna for LoRa Communication

by Aliyu Dala and Tughrul Arslan

Sensors 2021, 21(4), 1337; https://0-doi-org.brum.beds.ac.uk/10.3390/s21041337 - 13 Feb 2021

Cited by 17 | Viewed by 4053

Abstract

There is an increasing interest in water bodies, which make up more that seventy percent of our planet. It is thus imperative that the water environment should be remotely monitored. Radio frequency (RF) signals have higher bandwidth and lower latency compared to acoustic [...] Read more.

There is an increasing interest in water bodies, which make up more that seventy percent of our planet. It is thus imperative that the water environment should be remotely monitored. Radio frequency (RF) signals have higher bandwidth and lower latency compared to acoustic signals. However, water has high permittivity and conductivity which presents a challenge for the implementation of RF technology. In this work, we undertook a novel design, fabrication, measurement and implementation of an antenna for a sensor node with dual ability of underwater and water surface long range (LoRa) communication at 868 MHz. It was observed that the antenna’s performance deteriorated underwater without −10 dB effective bandwidth between 668 MHz and 1068 MHz. The introduction of an oil-impregnated paper buffer around the antenna resulted in an effective 400 MHz bandwidth within the same frequency span. The sensor node with the buffered antenna was able to achieve a distance of 6 m underwater and 160 m over water surface communication to a data gateway node. The sensor node without the buffered antenna was only able to achieve 80 m over water surface communication. These experimental results show the feasibility of using the LoRa 868 MHz frequency in underwater and water surface communication. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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16 pages, 5127 KiB

Open AccessArticle

Specific Resonant Properties of Non-Symmetrical Microwave Antennas

by Ján Labun, Pavol Kurdel, Alexey Nekrasov, Mária Gamcová, Marek Češkovič and Colin Fidge

Sensors 2021, 21(3), 939; https://0-doi-org.brum.beds.ac.uk/10.3390/s21030939 - 31 Jan 2021

Cited by 2 | Viewed by 2361

Abstract

The aircraft avionics modernization process often requires optimization of the aircraft itself. Scale models of aircraft and their antennas are frequently used to solve this problem. Here we present interesting properties of the resonant antennas, which were discovered serendipitously during the measurement process [...] Read more.

The aircraft avionics modernization process often requires optimization of the aircraft itself. Scale models of aircraft and their antennas are frequently used to solve this problem. Here we present interesting properties of the resonant antennas, which were discovered serendipitously during the measurement process of some microwave antennas’ models as part of an aircraft modernization project. Aircraft microwave antennas are often designed as non-symmetric flat microwave antennas. Due to their thin, low and longitudinally elongated outer profile, they are also called tail antennas. An analysis of the resonant properties of non-symmetric antennas was performed in the band from 1 GHz to 4 GHz. The length of the antenna models ranged from 2 cm to 7 cm. The width of the antennas, together with the thickness of the strip, was always a constant parameter for one measured set of six antennas. In the measurement and subsequent analysis, attention was focused on the first-series resonant frequency (λ/4) of each antenna. During the evaluation of the resonance parameters, the flat microwave antenna models showed specific resonant properties different from those of conventional cylindrical microwave antennas. This article aims to inform professionals about these unknown specific properties of non-symmetrical antennas. The results of experimental measurements are analyzed theoretically and then visually compared using graphs so that the reader can more easily understand the properties observed. These surprising observations open up some new possibilities for the design, implementation, and use of flat microwave antennas, as found in modern aircraft, automobiles, etc. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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15 pages, 4176 KiB

Open AccessArticle

A New Planar Microwave Sensor for Building Materials Complex Permittivity Characterization

by João G. D. Oliveira, José G. Duarte Junior, Erica N. M. G. Pinto, Valdemir P. Silva Neto and Adaildo G. D’Assunção

Sensors 2020, 20(21), 6328; https://0-doi-org.brum.beds.ac.uk/10.3390/s20216328 - 06 Nov 2020

Cited by 25 | Viewed by 3464

Abstract

A new microwave sensor is proposed to characterize the complex relative permittivity of building non-magnetic materials and used in the characterization of three concrete samples. The proposed sensor structure consists of a log-periodic planar antenna with microstrip elements tilted forward by an angle [...] Read more.

A new microwave sensor is proposed to characterize the complex relative permittivity of building non-magnetic materials and used in the characterization of three concrete samples. The proposed sensor structure consists of a log-periodic planar antenna with microstrip elements tilted forward by an angle β and printed, alternately, on the top and bottom sides of a dielectric layer. The operation principle is based on the measurement of the scattering parameters S₁₁ and S₂₁ in a free space propagation transmitter-receiver setup, for both cases with the material under test (MUT) sample (non-line-of-sight, NLOS) and without it (line-of-sight, LOS). A prototype is fabricated and measured to determine the scattering parameters of concrete samples. After measurements, the obtained results are used in the efficient and accurate Nicolson–Ross–Weir (NRW) method, making it possible to estimate the values of the complex relative permittivity of the concrete blocks. The sensor design is demonstrated from initial simulations to measurements for validation of the developed prototype. The obtained results for the complex relative permittivity of concrete are in agreement with those available in the literature and the difference between the simulated and measurement results for the sensor antenna resonant frequency is 4.71%. The used measurement setup can be applied to characterize different types of solid or liquid dielectric materials. Full article

(This article belongs to the Special Issue Antenna Measurement Techniques and Sensor Systems)

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