Research

22 pages, 3579 KiB

Open AccessArticle

Realistic 3D Phantoms for Validation of Microwave Sensing in Health Monitoring Applications

by Mariella Särestöniemi, Daljeet Singh, Rakshita Dessai, Charline Heredia, Sami Myllymäki and Teemu Myllylä

Sensors 2024, 24(6), 1975; https://doi.org/10.3390/s24061975 - 20 Mar 2024

Viewed by 611

Abstract

The development of new medical-monitoring applications requires precise modeling of effects on the human body as well as the simulation and the emulation of realistic scenarios and conditions. The first aim of this paper is to develop realistic and adjustable 3D human-body emulation [...] Read more.

The development of new medical-monitoring applications requires precise modeling of effects on the human body as well as the simulation and the emulation of realistic scenarios and conditions. The first aim of this paper is to develop realistic and adjustable 3D human-body emulation platforms that could be used for evaluating emerging microwave-based medical monitoring/sensing applications such as the detection of brain tumors, strokes, and breast cancers, as well as for capsule endoscopy studies. New phantom recipes are developed for microwave ranges for phantom molds with realistic shapes. The second aim is to validate the feasibility and reliability of using the phantoms for practical scenarios with electromagnetic simulations using tissue-layer models and biomedical antennas. The third aim is to investigate the impact of the water temperature in the phantom-cooking phase on the dielectric properties of the stabilized phantom. The evaluations show that the dielectric properties of the developed phantoms correspond closely to those of real human tissue. The error in dielectric properties varies between 0.5–8%. In the practical-scenario simulations, the differences obtained with phantoms-based simulations in S21 parameters are 0.1–13 dB. However, the differences are smaller in the frequency ranges used for medical applications. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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20 pages, 7480 KiB

Open AccessArticle

Microwave Receiving System Based on Cryogenic Sensors for the Optical Big Telescope Alt-Azimuth

by Yurii Balega, Grigory Bubnov, Artem Chekushkin, Victor Dubrovich, Valerian Edelman, Aleksandra Gunbina, Sergey Kapustin, Tatyana Khabarova, Dmitrii Kukushkin, Igor Lapkin, Maria Mansfeld, Andrei Maruhno, Vladimir Parshin, Aleksey Raevskiy, Vladislav Stolyarov, Mikhail Tarasov, Gennady Valyavin, Vyacheslav Vdovin, Grigory Yakopov, Renat Yusupov, Petr Zemlyanukha and Igor Zinchenko Show full author list Hide full author list

Sensors 2024, 24(2), 359; https://doi.org/10.3390/s24020359 - 07 Jan 2024

Viewed by 734

Abstract

This article presents the results of evaluating the possibility of conducting radio astronomy studies in the windows of atmospheric transparency ~100, ~230, and ~350 GHz using the optical Big Telescope Alt-Azimuthal (BTA) of the Special Astrophysical Observatory of the Russian Academy of Sciences [...] Read more.

This article presents the results of evaluating the possibility of conducting radio astronomy studies in the windows of atmospheric transparency ~100, ~230, and ~350 GHz using the optical Big Telescope Alt-Azimuthal (BTA) of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). A list of some promising astronomical tasks is proposed. The astroclimat conditions at the BTA site and possible optical, cryogenic, and mechanical interfaces for mounting a superconducting radio receiver at the focus of the optical telescope are considered. As a receiving system, arrays of detectors cooled to ~0.3 K based on the superconductor–insulator–normal metal–insulator–superconductor (SINIS) structure are proposed. The implementation of the project will make it possible to use the BTA site of the SAO RAS not only to solve some astronomical problems (it is possible to consider the implementation of a single observatory, the VLBI (very-long-baseline interferometry) mode in the Suffa, EHT (Event Horizon Telescope), and Millimetron projects), but it will also be used to test various cryogenic detectors in a real observatory. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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30 pages, 15781 KiB

Open AccessArticle

Dual-Polarization Ambient Backscatter Communications and Signal Detection

by Youze Yang and Sen Yan

Sensors 2024, 24(1), 223; https://doi.org/10.3390/s24010223 - 30 Dec 2023

Viewed by 640

Abstract

Ambient backscatter communication (AmBC), an emerging mechanism for batteryless communications that can utilize ambient radio-frequency signals to modulate information and thus reduce power consumption, has attracted considerable attention and has been considered as a critical technology in green “Internet of Things” sensor networks [...] Read more.

Ambient backscatter communication (AmBC), an emerging mechanism for batteryless communications that can utilize ambient radio-frequency signals to modulate information and thus reduce power consumption, has attracted considerable attention and has been considered as a critical technology in green “Internet of Things” sensor networks due to its ultra-low power consumption. This paper presents the first a complete dual-polarization AmBC (DPAm) system model, which can extend AmBC into polarization diversity and improve the data-transmission rate of backscatter symbols. We proposed two scenarios: direct dual-polarization-based DPAm node structures and polarization-conversion-based DPAm node structures. In addition, we consider a parallel backscatter mode with differential coding and develop corresponding detectors, which also give the analytical detection thresholds. Moreover, we consider a simultaneous backscatter mode with Manchester coding in order to avoid complex-parameter estimation. To address the power imbalance problem of the DPAm system that arises because the polarization deflection angle would cause the power level to change with different polarization patterns, we also develop a power-average detector and a clustering detector. Simulation results show the throughput performance on each DPAm node structure with each detector, demonstrating the feasibility and efficiency of the proposed DPAm nodes and detectors. Compared with single-polarization AmBC (SPAm), the proposed DPAm node can achieve higher throughput in most cases. Finally, the clustering detector is shown to be more robust to short training sequences and complex environments. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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24 pages, 6160 KiB

Open AccessArticle

Analysis and Implementation of Controlled Semiconductor Switch for Ultra-Wideband Radar Sensor Applications

by Patrik Jurik, Miroslav Sokol, Pavol Galajda and Milos Drutarovsky

Sensors 2023, 23(17), 7392; https://doi.org/10.3390/s23177392 - 24 Aug 2023

Cited by 2 | Viewed by 1178

Abstract

All ultra-wideband (UWB) sensor applications require hardware designed directly for their specific application. The switching of broadband radio frequency and microwave signals is an integral part of almost every piece of high-frequency equipment, whether in commercial operation or laboratory conditions. The trend of [...] Read more.

All ultra-wideband (UWB) sensor applications require hardware designed directly for their specific application. The switching of broadband radio frequency and microwave signals is an integral part of almost every piece of high-frequency equipment, whether in commercial operation or laboratory conditions. The trend of integrating various circuit structures and systems on a chip (SoC) or in a single package (SiP) is also related to the need to design these integrated switches for various measuring devices and instruments in laboratories, paradoxically for their further development. Another possible use is switching high-frequency signals in telecommunications devices, whether mobile or fixed networks, for example, for switching signals from several antennas. Based on these requirements, a high-frequency semiconductor integrated switch with NMOS transistors was designed. With these transistors, it is possible to achieve higher integration than with bipolar ones. Even though MOSFET transistors have worse frequency characteristics, we can compensate them to some extent with the precise design of the circuit and layout of the chip. This article describes the analysis and design of a high-frequency semiconductor integrated switch for UWB applications consisting of three series-parallel switches controlled by CMOS logic signals. They are primarily intended for UWB sensor systems, e.g., when switching and configuring the antenna MIMO system or when switching calibration tools. The design of the switch was implemented in low-cost 0.35 µm SiGe BiCMOS technology with an emphasis on the smallest possible attenuation and the largest possible bandwidth and isolation. The reason for choosing this technology was also that other circuit structures of UWB systems were realized in this technology. Through the simulations, individual parameters of the circuit were simulated, the layout of the chip was also created, and the parameters of the circuit were simulated with the parasitic extraction and the inclusion of parasitic elements (post-layout simulations). Subsequently, the chip was manufactured and its parameters were measured and evaluated. Based on these measurements, the designed and fabricated UWB switch was found to have the following parameters: a supply current of 2 mA at 3.3 V, a bandwidth of 6 GHz, an insertion loss (at 1 GHz) of −2.2 dB, and isolation (at 1 GHz) of

- 33

dB, which satisfy the requirements for our UWB sensor applications. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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24 pages, 21691 KiB

Open AccessArticle

Wideband TDoA Positioning Exploiting RSS-Based Clustering

by Andreas Fuchs, Lukas Wielandner, Daniel Neunteufel, Holger Arthaber and Klaus Witrisal

Sensors 2023, 23(12), 5772; https://doi.org/10.3390/s23125772 - 20 Jun 2023

Viewed by 1123

Abstract

The accuracy of radio-based positioning is heavily influenced by a dense multipath (DM) channel, leading to poor position accuracy. The DM affects both time of flight (ToF) measurements extracted from wideband (WB) signals—specifically, if the bandwidth is below 100 MHz—as well as received [...] Read more.

The accuracy of radio-based positioning is heavily influenced by a dense multipath (DM) channel, leading to poor position accuracy. The DM affects both time of flight (ToF) measurements extracted from wideband (WB) signals—specifically, if the bandwidth is below 100 MHz—as well as received signal strength (RSS) measurements, due to the interference of multipath signal components onto the information-bearing line-of-sight (LoS) component. This work proposes an approach for combining these two different measurement technologies, leading to a robust position estimation in the presence of DM. We assume that a large ensemble of densely-spaced devices is to be positioned. We use RSS measurements to determine “clusters” of devices in the vicinity of each other. Joint processing of the WB measurements from all devices in a cluster efficiently suppresses the influence of the DM. We formulate an algorithmic approach for the information fusion of the two technologies and derive the corresponding Cramér-Rao lower bound (CRLB) to gain insight into the performance trade-offs at hand. We evaluate our results by simulations and validate the approach with real-world measurement data. The results show that the clustering approach can halve the root-mean-square error (RMSE) from about 2 m to below 1 m, using WB signal transmissions in the 2.4 GHz ISM band at a bandwidth of about 80 MHz. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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17 pages, 4764 KiB

Open AccessArticle

Transmission-Based Vertebrae Strength Probe Development: Far Field Probe Property Extraction and Integrated Machine Vision Distance Validation Experiments

by Paul Meaney, Robin Augustine, Adrian Welteke, Bernd Pfrommer, Adam M. Pearson and Helena Brisby

Sensors 2023, 23(10), 4819; https://doi.org/10.3390/s23104819 - 17 May 2023

Viewed by 1012

Abstract

We are developing a transmission-based probe for point-of-care assessment of vertebrae strength needed for fabricating the instrumentation used in supporting the spinal column during spinal fusion surgery. The device is based on a transmission probe whereby thin coaxial probes are inserted into the [...] Read more.

We are developing a transmission-based probe for point-of-care assessment of vertebrae strength needed for fabricating the instrumentation used in supporting the spinal column during spinal fusion surgery. The device is based on a transmission probe whereby thin coaxial probes are inserted into the small canals through the pedicles and into the vertebrae, and a broad band signal is transmitted from one probe to the other across the bone tissue. Simultaneously, a machine vision scheme has been developed to measure the separation distance between the probe tips while they are inserted into the vertebrae. The latter technique includes a small camera mounted to the handle of one probe and associated fiducials printed on the other. Machine vision techniques make it possible to track the location of the fiducial-based probe tip and compare it to the fixed coordinate location of the camera-based probe tip. The combination of the two methods allows for straightforward calculation of tissue characteristics by exploiting the antenna far field approximation. Validation tests of the two concepts are presented as a precursor to clinical prototype development. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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15 pages, 4798 KiB

Open AccessArticle

Propagation Constant Measurement Based on a Single Transmission Line Standard Using a Two-Port VNA

by Ziad Hatab, Arezoo Abdi, Gregor Steinbauer, Michael Ernst Gadringer and Wolfgang Bösch

Sensors 2023, 23(9), 4548; https://doi.org/10.3390/s23094548 - 07 May 2023

Cited by 1 | Viewed by 1367

Abstract

This study presents a new method for measuring the propagation constant of transmission lines using a single line standard and without prior calibration of a two-port vector network analyzer (VNA). The method provides accurate results by emulating multiple line standards of the multiline [...] Read more.

This study presents a new method for measuring the propagation constant of transmission lines using a single line standard and without prior calibration of a two-port vector network analyzer (VNA). The method provides accurate results by emulating multiple line standards of the multiline calibration method. Each line standard was realized by sweeping an unknown network along a transmission line. The network need not be symmetric or reciprocal, but must exhibit both transmission and reflection. We performed measurements using a slab coaxial airline and repeated the measurements on three different VNAs. The measured propagation constant of the slab coaxial airline from all VNAs was nearly identical. By avoiding disconnecting or moving the cables, the proposed method eliminates errors related to the repeatability of connectors, resulting in improved broadband traceability to SI units. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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12 pages, 2788 KiB

Open AccessCommunication

UWB-Modulated Microwave Imaging for Human Brain Functional Monitoring

by Youness Akazzim, Marc Jofre, Otman El Mrabet, Jordi Romeu and Luis Jofre-Roca

Sensors 2023, 23(9), 4374; https://doi.org/10.3390/s23094374 - 28 Apr 2023

Cited by 1 | Viewed by 1510

Abstract

Morphological microwave imaging has shown interesting results on reconstructing biological objects inside the human body, and these parameters represent their actual biological condition, but not their biological activity. In this paper, we propose a novel microwave technique to locate the low-frequency ( [...] Read more.

Morphological microwave imaging has shown interesting results on reconstructing biological objects inside the human body, and these parameters represent their actual biological condition, but not their biological activity. In this paper, we propose a novel microwave technique to locate the low-frequency (

f ≃ 1

kHz) -modulated signals produced by a microtag mimicking an action potential and proved it in a cylindrical phantom of the brain region. A set of two combined UWB microwave applicators, operating in the 0.5 to 2.5 GHz frequency band and producing a nsec interrogation pulse, is able to focus its radiated field into a small region of the brain containing the microtag with a modulated photodiode. The illuminating UWB microwave field was first modulated by the low-frequency (

f ≃ 1

kHz) electrical signal produced by the photodiode, inducing modulated microwave currents into the microtag that reradiating back towards the focusing applicators. At the receiving end, the low-frequency (

f ≃ 1

kHz) -modulated signal was first extracted from the full set of the backscattered signals, then focused into the region of interest and spatially represented in the corresponding region of the brain, resulting in a spatial resolution of the images in the order of 10 mm. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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21 pages, 2027 KiB

Open AccessArticle

Improving TDOA Radar Performance in Jammed Areas through Neural Network-Based Signal Processing

by Jakub Gotthans, Tomas Gotthans and David Novak

Sensors 2023, 23(6), 2889; https://doi.org/10.3390/s23062889 - 07 Mar 2023

Viewed by 1963

Abstract

This paper presents a method for estimating the position of a target under jammed conditions using the Time Difference of Arrival (TDOA) method. The algorithm utilizes a deep neural network to overcome the challenges posed by the jammed conditions. The simulations and results [...] Read more.

This paper presents a method for estimating the position of a target under jammed conditions using the Time Difference of Arrival (TDOA) method. The algorithm utilizes a deep neural network to overcome the challenges posed by the jammed conditions. The simulations and results indicate that the presented method is more accurate and efficient than the traditional TDOA methods. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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17 pages, 11980 KiB

Open AccessArticle

Persistent Homology Approach for Human Presence Detection from 60 GHz OTFS Transmissions

by Roman Maršálek, Radim Zedka, Erich Zöchmann, Josef Vychodil, Radek Závorka, Golsa Ghiaasi and Jiří Blumenstein

Sensors 2023, 23(4), 2224; https://doi.org/10.3390/s23042224 - 16 Feb 2023

Cited by 1 | Viewed by 1659

Abstract

Orthogonal Time Frequency Space (OTFS) is a new, promising modulation waveform candidate for the next-generation integrated sensing and communication (ISaC) systems, providing environment-awareness capabilities together with high-speed wireless data communications. This paper presents the original results of OTFS-based person monitoring measurements in the [...] Read more.

Orthogonal Time Frequency Space (OTFS) is a new, promising modulation waveform candidate for the next-generation integrated sensing and communication (ISaC) systems, providing environment-awareness capabilities together with high-speed wireless data communications. This paper presents the original results of OTFS-based person monitoring measurements in the 60 GHz millimeter-wave frequency band under realistic conditions, without the assumption of an integer ratio between the actual delays and Doppler shifts of the reflected components and the corresponding resolution of the OTFS grid. As the main contribution of the paper, we propose the use of the persistent homology technique as a method for processing gathered delay-Doppler responses. We highlight the advantages of the persistent homology approach over the standard constant false alarm rate target detector for selected scenarios. Full article

(This article belongs to the Special Issue Microwave Sensing Systems)

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