Probe Antenna Research Articles

Plakun Burial Ground: a new discovery of the well-known site based on the results of the aerial lidar and ground penetrating radar research

The article presents findings of complex interdisciplinary researches of a group of sopkas in the Plakun terrain feature. The monument is part of the Staroladozhky archaeological complex located in Volk- hovsky district, Leningrad region, 120 km east of St. Petersburg. The sopkas are one of the main landmarks of the region. They are high steep embankments 11 – 30 m in diameter and 3 – 8 m high. They date back to the 8th – 10th centuries. The ethnicity of their makers is uncertain. Historiographical data suggest that the monu- ment consisted of 6 sopkas divided into clusters 3 embankments each. In 1955, the southernmost sopka was excavated for demolition. In 2022 – 2023, scheduled scientific researches and Russian Science Foundation Grant No. 23-18-00515 implied an aerial laser scanning of the monument territory. The area was scanned at the attitude of 70 – 90 m with a DJI Matrice 300 RTK drone and an L1 LiDAR from a DJI D-RTK ground station. The coordinates are referenced in LCS-47 Zone 2 with Spectra Epoch 50 GNSS receiver and amended by Geospider survey station network. The findings allow to distinguish a range of small hills in two groups of remaining sopkas. The standard presentation of Digital Elevation Model (DEM) clearly distinguishes 5 remaining large rounded embankments and piles of the excavated southernmost one. However, the research matches several relief color gradations. The study combines several DEM copies in QGIS geographic information system. Consequently, it is revealed that the chain of remaining embankments includes 4 rounded elevations. 3 of them resemble ploughed embankments. In 2023, two identified elevations were studied with OKO-2 ground penetrating radar equipped with a probe antenna which radiates 100 and 700 MHz pulses. The research involves gridding the area of the alleged lost ploughed sopkas and one apparent embankment. The profiles of the site were double-scanned. The radargrams reveal common structure features in the hills and sopka such as contrast mound foundations, heterogeneous centers, multi-layered structures and local depressions in the top layer around 0.5 meters thick. The findings suggest that 3 out of 4 hills can be viewed as demolished embank- ments of a sopka burial. The fourth one requires additional research.

A new synthetic correlation electron cyclotron emission diagnostic for validating nonlinear gyrokinetic simulations of electron temperature turbulence.

To validate nonlinear gyrokinetic simulations of electron temperature turbulence, the experimental correlation electron cyclotron emission (CECE) measurements are to be compared using a synthetic CECE diagnostic, which generates modeled CECE measurement quantities by implementing realistic measurement parameters (e.g., spatial and wavenumber resolutions, radial location, etc.) to nonlinear gyrokinetic simulations. In this work, we calculate the radial and vertical spatial and wavenumber transfer functions, which are defined by the electron cyclotron emission emissivity radial profile and vertical probing antenna pattern, respectively. These transfer functions are applied to nonlinear gyrokinetic simulations of electron temperature turbulence using the continuum gyrokinetic code. A simultaneous comparison of the experimental electron temperature turbulence power spectrum and root-mean-square (RMS) level, as well as the radial correlation length with the new synthetic CECE diagnostic at a core location ρ ∼ 0.75 in an L-mode DIII-D tokamak plasma, is presented. The preliminary result shows that the synthetic CECE output underestimates the RMS level by ∼42% and overestimates the radial correlation length by ∼40%.

Effect of soil compaction on the measurements of complex dielectric permittivity spectrum with an open-ended antenna probe and the coaxial cell system

The paper proposes the use of dielectric spectroscopy to measure changes in dielectric permittivity for soil subjected to compression. Density-dependent dielectric permittivity characteristics of soils for the entire range of obtained density, and thus for a significant parameter of soil properties corresponding with ideal conditions for plant growth as well as those inhibiting their growth were presented. Measurements were carried out for three soil types with different moisture content using an open-ended antenna probe (OE-A), operating in the frequency range of 20 MHz–1.2 GHz and a coaxial cell system in frequency range of 20 MHz–3 GHz. Experimental results showed that an increase in bulk density and volumetric water content of soil affects the complex dielectric permittivity spectrum – a model for this relationship was proposed. Soil dielectric permittivity as a parameter reflecting soil moisture and density can be useful in assessing soil quality.

Impact of seasonal variations on low and mid-latitudes ionospheric electric field satellite measurements

Ionospheric electric field measurements are provided by the Langmuir probe onboard the DEMETER satellite. Because there are four probes, various combinations of them form double probes that yield measurements. However, only the combination of probe antennas (E3) and (E4) enables possible measurements of the ambient (natural) ionospheric electric field. For other combinations, the measured field is almost identical to the induced field resulting from satellite motion. On the basis of this, we conducted comparative studies of the measured and induced electric fields during different seasons (summer, autumn, winter, and spring) to determine the best period for ionospheric electric field measurements. Multiple orbits were selected during different periods when the satellite was exposed to solar radiation. In all seasons except winter, the profiles of the induced and measured ionospheric electric field are similar. This masking effect leads to an underestimation of the ambient electric field. However, the highest accuracy for the ambient field can be obtained during winter, when solar flux radiation is weaker than that during other seasons. The probe position and orbital altitude also play important roles in the behavior of the induced electric field.

Fully Probe-Corrected Near-Field Far-Field Transformations With Unknown Probe Antennas

Fully Probe-Corrected Near-Field Far-Field Transformations With Unknown Probe Antennas

Reducing the Measurement Time in a Reverberation Chamber to Less than 1 Second

To increase the speed of the measurement, a time-efficient multi-probe system in a reverberation chamber (RC) is validated. The system consists of 4 printed circuit board (PCB) switches integrating with 128 probe antennas. By using solid-state switches, all antennas can be switched over in sequence in less than 1 second. Typical characteristics of the RC and the total radiated power (TRP) of the device under test (DUT) are performed to verify the validity of this configuration. Compared with the RC using mechanical stirrers, this system shows its superiority in terms of testing efficiency.

Impact of the turbulence wavenumber spectrum and probing beam geometry on Doppler reflectometry perpendicular velocity measurements

The perpendicular propagation velocity of turbulent density fluctuations is an important parameter in fusion plasmas, since sheared plasma flows are crucial for reducing turbulence, and thus an essential input parameter for turbulent transport simulations. In the recent past various fusion devices have observed poloidal asymmetry in this velocity using Doppler reflectometry (DR) and correlation reflectometry. In this work, the phase screen model is used to analytically explain and quantify the combined effect of finite wavenumber resolution due to plasma curvature and probing beam geometry in a realistic turbulence wavenumber spectrum, leading to a reduced dominantly back-scattered wavenumber and a further underestimation of the perpendicular propagation velocity determined by DR. The full-wave code IPF-FD3D, which simulates microwave propagation and scattering, is used as a synthetic DR to study the effects of this diagnostic effect in a circular geometry using various isotropic synthetic turbulence wavenumber spectra. Angular scans from the midplane and variations in the position of the probing antenna are shown to estimate the impact of the diagnostic effect on the poloidal asymmetries.

An exploratory simulation study and prediction model on human brain behavior and activity using an integration of deep neural network and biosensor Rabi antenna

The plasmonic antenna probe is constructed using a silver rod embedded in a modified Mach-Zehnder interferometer (MZI) ad-drop filter. Rabi antennas are formed when space-time control reaches two levels of system oscillation and can be used as human brain sensor probes. Photonic neural networks are designed using brain-Rabi antenna communication, and transmissions are connected via neurons. Communication signals are carried by electron spin (up and down) and adjustable Rabi frequency. Hidden variables and deep brain signals can be obtained by external detection. A Rabi antenna has been developed by simulation using computer simulation technology (CST) software. Additionally, a communication device has been developed that uses the Optiwave program with Finite-Difference Time-Domain (OptiFDTD). The output signal is plotted using the MATLAB program with the parameters of the OptiFDTD simulation results. The proposed antenna oscillates in the frequency range of 192 THz to 202 THz with a maximum gain of 22.4 dBi. The sensitivity of the sensor is calculated along with the result of electron spin and applied to form a human brain connection. Moreover, intelligent machine learning algorithms are proposed to identify high-quality transmissions and predict the behavior of transmissions in the near future. During the process, a root mean square error (RMSE) of 2.3332(±0.2338) was obtained. Finally, it can be said that our proposed model can efficiently predict human mind, thoughts, behavior as well as action/reaction, which can be greatly helpful in the diagnosis of various neuro-degenerative/psychological diseases (such as Alzheimer's, dementia, etc.) and for security purposes.

A Fast and Efficient Calibration Method for Phased Array Antennas Using Fourier-Structured Excitation Matrix

This article presents a novel phased array antenna calibration method. Unlike conventional phased array calibration methods equipped with only one probe antenna in the far-field setup, multiple measurement probes are introduced in the proposed algorithm to significantly improve the measurement efficiency. Specifically, a novel construction method for an excitation matrix (which contains excitation coefficients for phased array elements) is proposed, where phase differences introduced by the spatial locations of the multiple probes are perfectly incorporated into the Fourier-structured excitation matrix, thereby presenting the best measurement efficiency without sacrificing the array calibration accuracy. The proposed method can offer robust array calibration results (guaranteed by the low condition number of the constructed excitation matrix with Fourier structure) and high measurement efficiency (offered by multiprobe setups). To experimentally validate the proposed algorithm, a multichannel (i.e., multiprobe) far-field measurement setup was utilized. A four-element open-ended waveguide array operating at 2.6 GHz and two-probe far-field systems were employed as the antenna under test (AUT) and multiple probes, respectively, to validate the effectiveness and robustness of the proposed phased array calibration algorithm. The proposed algorithm will be highly valuable for efficient phased array calibration, especially for future antenna systems equipped with large-scale antenna configurations.

SYNCA: A Synthetic Cyclotron Antenna for the Project 8 Collaboration

Cyclotron Radiation Emission Spectroscopy (CRES) is a technique for measuring the kinetic energy of charged particles through a precision measurement of the frequency of the cyclotron radiation generated by the particle's motion in a magnetic field. The Project 8 collaboration is developing a next-generation neutrino mass measurement experiment based on CRES. One approach is to use a phased antenna array, which surrounds a volume of tritium gas, to detect and measure the cyclotron radiation of the resulting β-decay electrons. To validate the feasibility of this method, Project 8 has designed a test stand to benchmark the performance of an antenna array at reconstructing signals that mimic those of genuine CRES events. To generate synthetic CRES events, a novel probe antenna has been developed, which emits radiation with characteristics similar to the cyclotron radiation produced by charged particles in magnetic fields. This paper outlines the design, construction, and characterization of this Synthetic Cyclotron Antenna (SYNCA). Furthermore, we perform a series of measurements that use the SYNCA to test the position reconstruction capabilities of the digital beamforming reconstruction technique. We find that the SYNCA produces radiation with characteristics closely matching those expected for cyclotron radiation and reproduces experimentally the phenomenology of digital beamforming simulations of true CRES signals.

An Antenna Solution for Glacial Environmental Sensor Networks

Antennas used in glacial environmental sensor networks and reported in the last two decades have been reviewed. A link budget framework for designing such antenna systems is presented and used to design an antenna system for deployment at the Thwaites glacier, Antarctica. Design details of two left hand circularly polarized cross dipole antennas, one for englacial sensor probes and the other for supraglacial surface receivers are presented. The probe antenna is a 3D bent cross dipole that fits within a borehole of 8 cm diameter while providing a 1 dBic gain at 433 MHz in ice. The surface receiver antenna is a planar printed antenna providing a gain of 6.1 dBic with a quarter wave reflector. Both antennas provide 3 dB beamwidths of at least 50° in the xz and yz vertical planes catering for transmitter-receiver antenna misalignments caused by extended deployments. The antennas displayed good circular polarization and polarization purity traits. The 3 dB axial ratio bandwidths of both the antennas remained 54.9 %. The total efficiencies of the bent cross dipole and the surface receiver antennas were noted as 69.7 % and 86.9 % respectively. Lastly, the 433 MHz band has been validated for achieving englacial communication ranges of up to 2300 metres.

Machine Learning Approach in Optimal Localization of Tumor Using a Novel SIW-Based Antenna for Improvement of Ablation Zone in Hepatocellular Carcinoma

In recent years, hepatocellular carcinoma has been the leading cause of cancer-related mortality and thermal ablation procedures such as MWA (microwave ablation) and RFA (Radiofrequency ablation) provide a viable alternative to radiation and surgical excision. Due to uneven ablation and tissue charring in RFA, MWA offers faster and uniform heating as a result of its higher operating frequency. In MWA, the antenna probe heats the tissue to the point of cell necrosis using electromagnetic heating. In this aspect, a substrate-integrated waveguide (SIW) antenna is designed to work at 2.45 GHz. Further, a finite element method (FEM) is employed to model the probe and the liver tissue environment. Within 10 minutes of application time, a maximum ablation diameter of 32 mm (transversal-T) and 25 mm (axial-A) is achieved at 20W of power. Since the position of the applicator probe is of utmost importance, the relationship between the percentage of ablation, probe tip position, and tumor diameter is evaluated using ML- algorithm to estimate the ideal probe location for maximal tumor ablation and thus may improve clinical outcome.

Noninvasive measurement of subcutaneous temperature using active antenna and high gain low noise microwave radiometer

ABSTRACT This paper presents a radiometric thermometer for non-invasive measurement of the internal body temperature. The proposed radiometric thermometer designed in 1.575 GHz band consists of a near-field probe and a high gain Dick radiometer. A phantom based on Agar material was developed to emulate the real tissue of skin and muscle for experiments. The measured results show that the active probe antenna provides additional 12.5 dB gain with noise figure less than 1dB, and the radiometer has a system gain of 50 dB and total noise figure of 1.738 dB at 1.575 GHz. The output voltage measured by the proposed 1.575 GHz microwave radiometer is 2.994 V when the water temperature is set to 25 °C, while it is 3.129 V when the water temperature is set to 80 °C. The study demonstrates that using the active probe connected to the radiometer can identify temperature difference of the body.

An Efficient OTA Calibration and Pattern Estimation Method for 5G mmWave Large-Scale Arrays

In this article, an efficient over-the-air (OTA) calibration and pattern estimation method under the midfield (MF) condition for the fifth-generation (5G) millimeter-wave (mmWave) large-scale arrays is proposed. A new transformation and revision algorithm is developed to calibrate the antenna array fast and accurate. Meanwhile, the time consumed in the accurate beamforming pattern estimation is reduced significantly. The proposed method requires a much smaller size anechoic chamber, a fixed probe antenna, and a vector network analyzer (VNA). The effectiveness is proven with the detailed theoretical analysis and experimented with a 64-element phased array in the 26 GHz band. The calibrated root-mean-square (rms) errors of the phase and magnitude are about 1.8°/0.4 dB. In addition, the proposed calibration and pattern estimation method is tremendously cost-effective and time-saving with similar accuracy as the far-field test method.

Simulation of Negative and Positive Corona Discharges in Air for Investigation of Electromagnetic Waves Propagation

Corona discharge, as one of the partial discharge (PD) modes, emits electromagnetic (EM) waves in the ultrahigh frequency (UHF) range. In order to study the behavior of the EM waves emitted from a PD source, a comprehensive PD source modeling method should be employed that takes into account the essential processes involved in the formation of that. In this article, a drift- and diffusion-based model is presented to simulate the corona discharges in the positive and negative voltages to investigate the differences between these two types of corona and their characteristics in terms of the EM waves’ propagation. This modeling tool includes ionization, attachment, and photoionization source terms as necessary phenomena to form the discharge. The results are analyzed for both types of coronas in the UHF range, and the differences between them are shown. Experimentally measured corona discharges using a high-frequency current transformers (HFCTs) and a monopole antenna probes are compared with the simulation current signals in the time and frequency domains, with promising results in terms of rise time and amplitude of the signal.

Mm-wave polarimeter and profilometry design study for retrieving plasma density in the PANDORA experiment

In the recent past, the possibility to use a superconducting trap confining a hot and dense plasma as a tool to investigate radioactivity in astrophysical scenarios has been proposed. Making possible these kind of unprecedented measurements is the main aim of the PANDORA (Plasmas for Astrophysics Nuclear Decays Observation and Radiation for Archaeometry) project. In this context, it is planned to build a compact and flexible magnetic plasma trap where plasma reaches an electron density ne ∼ 1011–1013 cm−3, and an electron temperature, in units of kT, kTe ∼ 0.1–30 keV. The setup is conceived to be able to measure, for the first time, nuclear β-decay rates in stellar-like conditions in terms of ionization states. In this paper, the design study of a mm-wave polarimeter for the PANDORA plasma line-integrated electron density measurement is presented. The paper highlights the method of this type of measurements for the first time proposed for a magneto-plasma trap which represents an “intermediate” case between the ultra-compact plasma ion sources and the large-size thermonuclear fusion devices. Preliminary measurements at scaled microwave frequencies have carried out both on a “free-space” setup by using a wire-grid polarizer and a rotable Ka-band OMT + horn antennas system, and on a compact trap (called Flexible Plasma Trap) installed at INFN-LNS and used as PANDORA down-sized testbench are described. The polarimeter technique will support β-decay investigation by simultaneous measurements of the total plasma density, which is crucial to carefully evaluate the decay-constant and to extrapolate the laboratory observed data to the astrophysical scenarios. Moreover, this work proposes to adopt an electromagnetic inverse-scattering-based technique-based method to retrieve the electron density profile along the probing antennas line-of-sight. Numerical results of this so-called “inverse profilometry” are also shown.

Waveguide-coupled heterodyne terahertz detector based on AlGaN/GaN high-electron-mobility transistor

We report a room-temperature, low output impedance, broad intermediate-frequency (IF) bandwidth field-effect terahertz detector based on an AlGaN/GaN high-electron-mobility transistor (HEMT) integrated in a metal waveguide. The waveguide detector equips a pair of quasi-Yagi antenna probes that are used to couple the terahertz energy to the HEMT channel. The gate is configured as an asymmetric edge-coupled coplanar waveguide transmission line. This terahertz electric field is asymmetrically distributed in the channel along the edges of the transmission lines. The responsivity and noise for direct and heterodyne detections are characterized and analyzed at different local oscillator (LO) powers. The noise-equivalent power in direct detection is below 189 pW/Hz1/2. Operated in a heterodyne mode with a LO power of −3 dBm, the detector offers a conversion loss less than 55 dB in a frequency band of 320–340 GHz. The channel in a form of transmission line performs the broad IF bandwidth, which is increased to gigahertz range (3 GHz), and reduces the output impedance to 377 Ω which is about 20 times lower than previously reported. The transmission-line impedance could be optimized together with the distribution of the terahertz electric field in the gated channel to reduce the conversion loss.

Achieving Wireless Cable Testing for MIMO Terminals Based on Maximum RSRP Measurement

It is essential to perform end-to-end performance testing of multiple-input–multiple-output (MIMO) systems under realistic propagation channel conditions. However, due to the highly integrated and compact radio frequency (RF) system design, the traditional conducted cable testing method is getting more and more problematic. The wireless cable solution, which can achieve the equivalent functionality of the conducted cable testing without actual RF coaxial cables, has attracted huge attention from the industry and standardization for over-the-air (OTA) testing in recent years. However, the state-of-the-art solutions to achieve wireless cable testing necessitate at least reference signal received power (RSRP) reporting per device under test (DUT) antenna port for MIMO capable terminals, which is demanding and might not be accessible for commercial DUTs. In this work, a novel wireless cable solution based only on the maximum RSRP measurement of all DUT antenna ports is proposed, which can significantly alleviate the requirement of DUT RSRP reporting. To achieve the wireless cable testing, a novel calibration procedure is proposed to determine the transfer matrix between the probe antenna ports and the DUT antenna ports based on the DUT maximum reported RSRP measurement. The proposed algorithm is theoretically derived and experimentally validated for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> MIMO system, where the isolation of above 25 dB is achieved for the measurement setup. The numerical simulation and experimental validation demonstrate the efficiency and robustness of the proposed algorithm.

Direct measurement of electron Bernstein waves in Low Aspect ratio Torus Experiment (LATE)

By using a newly developed five-pin probe antenna and two-dimensional mechanical probe driving system, the 2D wave pattern of phase and amplitude has been directly measured in the Low Aspect ratio Torus Experiment (LATE) device, for an overdense ECR plasma with microwave obliquely injected. In the case of O-mode injection, an electron Bernstein wave (EBW)-like wave pattern has been detected for the first time, in a localized region near the upper hybrid resonance layer. The pattern has a short wavelength of about 2 mm and is also electrostatic and backward. In the case of X-mode injection, the 2D wave pattern is quite different and no EBW signal can be observed. By adjusting the toroidal magnetic field in O-mode injection, it is found that both the position and size of the EBW region have changed, which suggests the localized condition of efficient O-X-B conversion and high collisional damping rate of EBWs in these experiments.

A Cost-Effective Tethered-UAV-Based Coherent Near-Field Antenna Measurement System

For antenna measurements, the device under test (DUT) is usually transported to an anechoic chamber equipped with a scanner system. To measure on-site, unmanned aerial vehicles (UAVs) are a flexible solution as they can precisely maneuver a probe antenna over a surface in the DUT&#x2019;s near-field region. In this work, the designed multi-rotor UAV enables electromagnetically optimal placement of the probe antenna and effective gravity center re-balacing by payload position adjustment. The on-board software-defined radio (SDR) serves as a dual-channel receiver for the dual-polarized probe and as a signal source. For phase-coherent measurements, the source signal is transmitted to the DUT via an optical fiber tethering the UAV to the ground control station. Power supply cables allow unlimited flight times. A laser-based tracking system originating from virtual reality (VR) applications measures the probe position and orientation. The developed operator software guides the UAV along a trajectory and records the irregularly distributed near-field samples. An inverse equivalent sources solver (IESS) with full probe correction computes equivalent sources for antenna diagnostics and the DUT far field. The deployed components make the system very cost-effective. Still, verification measurements demonstrate its usability and the accuracy of the results for frequencies up to several GHz.