Electric Antenna Research Articles

Whistler Wave Observations by Parker Solar Probe During Encounter 1: Counter-propagating Whistlers Collocated with Magnetic Field Inhomogeneities and their Application to Electric Field Measurement Calibration

Observations of the young solar wind by the Parker Solar Probe (PSP) mission reveal the existence of intense plasma wave bursts with frequencies between 0.05 and 0.20f ce (tens of hertz up to ∼300 Hz) in the spacecraft frame. The wave bursts are often collocated with inhomogeneities in the solar wind magnetic field, such as local dips in magnitude or sudden directional changes. The observed waves are identified as electromagnetic whistler waves that propagate either sunward, anti-sunward, or in counter-propagating configurations during different burst events. Being generated in the solar wind flow, the waves experience significant Doppler downshift and upshift of wave frequency in the spacecraft frame for sunward and anti-sunward waves, respectively. Their peak amplitudes can be larger than 2 nT, where such values represent up to 10% of the background magnetic field during the interval of study. The amplitude is maximum for propagation parallel to the background magnetic field. We (i) evaluate the properties of these waves by reconstructing their parameters in the plasma frame, (ii) estimate the effective length of the PSP electric field antennas at whistler frequencies, and (iii) discuss the generation mechanism of these waves.

Very-Low-Frequency Magnetoelectric Antennas for Portable Underwater Communication: Theory and Experiment

Finding an efficient way for underwater communication with a portable antenna at very low frequency (VLF 3–30 kHz) is challenging since the conventional electrical antennas require the size to be larger than 1/10 of the wavelength. Recently, acoustically driven antennas were proposed to realize portable VLF communication in air but lack the demonstration in a lossy environment. Here, we reported the first VLF underwater communication system based on a pair of acoustically actuated magnetoelectric (ME) antennas with small size of 10 cm in length. A theoretical analysis of reflection and radiation performance of the ME antenna was conducted, where the electromechanical resonance (EMR) frequency and effective magnetic dipole moment were estimated, and a near-field coupling model of a pair of ME antennas was further established. The results of theoretical predictions and finite element model (FEM) simulations were then compared with experimental measurements and their differences were discussed. A prototype of underwater communication system based on the ME antenna pair was finally presented, where a binary digital modulation with a bit rate of 100 b/s has been demonstrated, confirming the feasibility of ME antennas for portable underwater communication.

Flexural Vibration Magnetoelectric Antenna for Medium Frequency and High Frequency

High-frequency (HF) and medium frequency (MF) antennas are an important part of modern wireless communication systems. However, the extremely large size of small electric antennas in these bands limits the range of applications of wireless communication systems, especially in implantable devices and the Internet of Things (IoT). In this article, a Microscale Flexible Vibration-Magnetoelectric (FV-ME) antenna with resonant frequencies at MF or HF is proposed. At MF or HF, the size of FV-ME is smaller than that of Magnetoelectric (ME) antennas based on other driving modes. The coupling mechanism of the FV-ME antenna is analyzed using an equivalent circuit. The equivalent circuit is formed by adding a force-magnetic coupling coefficient to the equivalent circuit of a piezoelectric micromechanical ultrasonic transducer, which is derived by the energy method. The effects of material coverage, thickness ratio, modulus ratio and acoustic radiation on the ME coefficient of the FV-ME were evaluated. These results show that ME antennas based on bending vibration modes can operate at intermediate or high frequencies. Furthermore, the FV-ME antenna having a diameter of hundreds of microns is significantly smaller than other MF or HF antennas.

MICS-Band Helical Dipole Antenna for Biomedical Implants

This letter presents the design, analysis, and measurement of a miniaturized ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{7}\!\times\!\text{7.5}$</tex-math></inline-formula> mm) electrically small helical dipole antenna with the introduction of a flexible magnetic sheet of high permittivity and permeability for biomedical implants. The proposed helical dipole, operating at 402–405 MHz Medical Implant Communication Services (MICS) band, supports wider bandwidths (10 dB bandwidth: simulated 33 MHz; measured 49.5 MHz) compared to the state-of-the-art designs. In addition, as a hybrid between a magnetic loop antenna and an electric dipole antenna and operating in the normal mode with small radian (ka < 0.36), enhanced radiation efficiency has been achieved as a result of the magnetic sheet. Measured in-body to on-body transmission verifies the antenna performance.

Wideband self-isolated four-element MIMO antenna based on magnetic monopole and electric monopole for sub-6 GHz 5G communication applications

ABSTRACT A wideband antenna element is designed based on complementary antenna theory by utilizing magnetic and electric monopole antennas. By sequentially rotating the antenna element, a wideband MIMO antenna is designed with an impedance bandwidth of 51.2% (3.1–5.2 GHz), which covers the 5G sub-6 GHz bands (N48/N77/N78/N79) with isolation greater than 21.8 dB between the antenna elements over the operating band. The proposed MIMO antenna provides pattern diversity with a half-power beamwidth (HPBW) greater than (–) over the wide bandwidth. It has a stable gain of 4 dBi over the bandwidth. The proposed MIMO antenna exhibits good efficiency, low ECC, and low channel capacity loss in the operating frequency band.

Simulation of electric field response of horizontal circular electric half wave dipole antenna for seabed logging

Seabed logging (SBL) is a direct and remote application of controlled source electromagnetic (CSEM) method to detect hydrocarbon resources beneath the seafloor in offshore conditions. In this method, electromagnetic waves are used to detect the resistivity contrast between various sediment layers. The current source of electromagnetic waves is a horizontal electric dipole (HED) antenna. The antenna design represents a challenge in shallow waters (less than500 m seawater depth) due to the presence of airwaves that lead to a low signal-to-noise ratio, hence hindering the detection of a hydrocarbon reservoir. A horizontal circular electric half-wave dipole will be used in this work as the source of electromagnetic waves. The numerical solution for the electric field response will be developed based on solving the Maxwell equations in two modes: the poloidal and toroidal modes. Simulation results have shown that the new antenna is able to detect the presence of deep hydrocarbon reservoirs (up to 5000 m) in shallow-water environment. Comparison of the average percentage difference in delineation between the circular and the HED was carried out. The new antenna results in 61 % delineation compared to 15 % for the HED at 5000 m hydrocarbon depth and 200 m seawater depth, indicating the ability of the antenna to disperse the airwaves. The results also show that the airwaves are significantly reduced from nearly 15000 m (for the HED) to 10000 m offset for the proposed antenna, hence increasing the signal-to-noise ratio. These results seem to indicate the potential for the new antenna to be used as an EM source for SBL in shallow-water environment.

A Magnetic Yagi-Uda Antenna With Vertically Polarized Endfire Radiation in Millimeter-Wave Band Applying Higher Order Mode

A magnetic Yagi-Uda antenna applying higher order mode in millimeter-wave (mm-Wave) band with vertically polarized endfire radiation is proposed in this article. Surface wave mode analysis is applied to spot TE mode for magnetic Yagi-Uda antenna in contrast to TM mode for electric Yagi-Uda antenna. A modified structure evolved from conventional U-shaped cavity is used to address the reversed current issue for higher order mode, which exhibits a more uniform phase distribution at the Yagi-Uda array end. Then, a composite end-feeding structure with reflector integrated is further introduced to minimize its parasitic effects for practical antenna design in mm-Wave band. To validate the design, a prototype with a size of 2.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\mathbf {0}}\times1.25\lambda _{\mathbf {0}}\times0.088\lambda _{\mathbf {0}}$ </tex-math></inline-formula> is fabricated and tested. It can achieve anendfiregain of 8–11 dBi within 24–26 GHz with –10 dB impedance band covering an even wider frequency range. The measured front-to-back ratio (FBR) is larger than 16.1 dB. Vertically polarized radiation is realized with cross-polarization level lower than –20 dB atendfiredirection.

Design of Low-RCS Broadband High-Gain Antennas Based on Transmission Array Metasurface.

In this paper, a low-RCS broadband high-gain antenna based on metasurface transmission array is proposed, consisting of two parts: a metasurface transmission array and a feed antenna. When designing the metasurface transmission array, the phase compensation method is used to achieve the beam convergence effect of metasurface in the broadband. By designing the elements and using the checkerboard arrangement, the RCS of the incident wave with fixed polarization can be reduced more than 10 dB at X band or Ku band. The feed antenna is designed as a microstrip magnetic and electric dipole antenna, which has the characteristics of small structure and wide impedance bandwidth. An antenna that can reduce RCS by more than 10 dB in Ku band is simulated and measured. The measurement and simulation results show that the −10 dB operating bandwidth of the high-gain antenna designed in this paper is 6.7~13.5 GHz, and the relative bandwidth is 67%. The designed metasurface can effectively improve the gain of the antenna in the operating frequency band. In this way, the design of high-gain antenna is realized, and the antenna has an obvious RCS reduction effect on the vertically incident y-polarized wave in the whole Ku band. The method to design an antenna in this paper realizes the regulation of radiation and scattering at the same time, which has important reference significance for expanding the function of transmission array antennae and has great application value.

Electrically Small Piezocomposite Strain Antennas

Recent literature has explored the use of single-material piezoelectrics for impedance matching in electrically small strain antennas. Efficiency calculations have assumed that radiation resistance is the same as that of a small wire dipole. In this work, piezoelectric composites, or piezocomposites, are used for impedance matching electrically small antennas to increase the degrees of freedom in the design process. A methodology is proposed for impedance matching a piezocomposite strain antenna at the desired center frequency over the desired bandwidth via optimal choice of materials, volume fraction, and shape without the need for an external matching network. Furthermore, the radiation resistance for piezoelectric strain antennas is derived from Wheeler’s power factor and is shown to be much smaller than that of the similarly sized electric dipole antenna that was assumed in much of the literature. The radiated power and efficiency are expressed directly in terms of piezocomposite material properties and the dimensions of the antenna. The results from this investigation provide a model of the impedance matching capabilities and efficiency limits for the piezoelectric strain antenna, demonstrating fundamental limitations for VLF applications.

Magnetic and electric antennas synergy for partial discharge measurements in gas-insulated substations: Power flow and reflection suppression

One of the main difficulties in measuring partial discharges (PD) in gas-insulated substations (GIS) is the overlapping of pulses at the sensor’s location, which distorts the pulse resolution and the charge estimation. This research presents a new method called “synergy,” which identifies and suppresses reflections using magnetic and electric antennas in the very-high frequency range. By scaling the antennas’ outputs and adding them, it is possible to segregate forward and backward pulses. Additionally, by multiplying the electric and magnetic signals, the power flow of the pulses is obtained, which identifies the propagation direction and the location of discontinuities in the transmission path. The synergy method is evaluated in three scenarios: a fully matched test bench using a calibrated pulse, a full-scale GIS using a calibrated pulse, and a full-scale GIS using a PD defect. The results showed that the pulse reflections can be eliminated from the incident pulse, improving the charge calculation when the pulses overlap. The output of this research represents an improvement for PD monitoring in GIS, exhibiting a tool for better defect localization, pulse wave shape construction, charge estimation, and possible interference rejection.© 2017 Elsevier Inc. All rights reserved.

Quasi‐Periodic Whistler Mode Emission in the Plasmasphere as Observed by the DSX Spacecraft

AbstractWe describe the quasi‐periodic (QP) whistler‐mode emissions found in the plasmasphere as detected by electric and magnetic instrumentation onboard the Demonstration and Science Experiments (DSX) spacecraft in medium Earth orbit. Over the course of the nearly 2‐year mission, at least 45 episodes of whistler mode QP emissions were detected by the Broad Band Receiver (BBR) onboard DSX. Episodes of QP emissions were identified by discrete events having a clear unambiguous periodic nature as detected by both the electric antennae and search coil magnetic sensors in the BBR survey data at 30 s temporal resolution. Most of the QP episodes occurred in a frequency range between 1 and 4 kHz, in a band previously identified by Van Allen Probes and Cluster investigators. However, episodes were also detected by DSX at higher frequencies ‐ events in these episodes extending all the way to 15 kHz. We present our findings on these unusual high frequency events in the presentation herein. Specifically, these high frequency QP episodes tended to be observed near dawn/dusk when the spacecraft was at relatively high magnetic latitudes and on magnetic L‐shells between 3 and 5. Another unusual feature of these episodes is that individual up‐drifting events making up the episode were found to sometimes occur concurrently in time: The high frequency portion of one up‐drifting “polliwog‐shaped” event overlapped in time with the low frequency portion of the subsequent event. This behavior of the QP emissions has not been previously emphasized and we consider how this temporal concurrence relates to the source processes.

Transceiving Signals by Mechanical Resonance: A Miniaturized Standalone Low Frequency (LF) Magnetoelectric Mechanical Antenna Pair With Integrated DC Magnetic Bias

Low frequency(LF) communication systems offer significant potential in internet of things(IoT) applications due to their low propagation loss and long transmission range. However, traditional LF electrical antennas are too bulky for IoT. Due to their small dimensions, magnetoelectric mechanical antennas are promising, however, the state of art magnetoelectric antennas either have bulky external magnetic bias or have limited operation range. In this paper, we present a miniaturized standalone LF magnetoelectric transmitting/receiving antenna pair with integrated magnetic bias to significantly improve the operation range by 360%. As the operation principle of the antenna is based on mechanical resonance, its dimension is reduced by four orders of magnitude compared with an electrical antenna counterpart. The transmitting and receiving antennas are the same in structure and dimensions: they are both composed of magnetostrictive Terfenol-D and piezoelectric PZT laminate with dimensions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$38\times 12\times19.4$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The integrated magnetic bias significantly reduces the dimension compared with magnetoelectric antennas with external bias. Performance measurement demonstrates that a maximum operation distance of 4 m is achieved without DC magnetic bias, while maximum operation distance with DC magnetic bias is 9 m, which is significantly improved by 225%. Compared with the spiral LF antenna presented in prior study, the radiation efficiency of the magnetoelectric antenna is enhanced by 17.96 times, resulting in 360% operation distance improvement from 2.5m at an input power of 4.5W to 9m at an input power of 2.03W. The LF magnetoelectric mechanical antenna pair may be a promising candidate for IoT applications.

Wavelength Measurements of Electron Cyclotron Harmonic Waves in Earth's Magnetotail

AbstractElectron cyclotron harmonic (ECH) waves, potential drivers for diffuse aurora precipitation, have been extensively investigated for decades. The generation mechanism of ECH waves, however, remains an open question. Theoretical work in 1970s has demonstrated that ECH waves can be excited by loss cone distributions of hot plasma sheet electrons. Recent THEMIS spacecraft observations, however, indicate that the waves can also be excited by low energy electron beams. Utilizing interferometry techniques to analyze the phase difference between electric potentials measured by individual probes on Electric Field Instrument antenna pairs on THEMIS spacecraft, we compute the wavenumber of both beam‐driven ECH waves and loss‐cone‐driven ECH waves. These wavenumber measurements as well as other wave properties obtained from spacecraft measurements prove to be consistent with expectation from linear instability analysis. This provides us with independent verification of the generation mechanism and linear dispersion relation of beam‐driven and loss‐cone‐driven ECH waves. Our statistical results demonstrate that the median value of the wave vectors of beam‐driven ECH waves, characterized by wave normal angles () less than 80°, is 0.011 m−1; and that of loss‐cone‐driven ECH waves, characterized by wave normal angles larger than 85°, is 0.00765 m−1. Direct wavenumber measurements of ECH waves allow us to better understand the interaction between ECH waves and electrons in Earth's magnetosphere.

Electromechanical Coupling and Application of High-Frequency Communication Antenna Channel Capacity

The next-generation communication base station antennas represented by phased array antennas are towards high frequency, high gain, high density, and high pointing accuracy. The influence of mechanical structure factors on communication system channel quality is obviously increasing, and the electromechanical coupling problem is becoming more prominent. To effectively guarantee the realization of 5G/6G communication in complex working environments and accelerate the commercial process of future communication systems, an electromechanical coupling channel capacity model is established in comprehensive consideration of the positional shift, attitude deflection, and temperature change of the communication base station phased array antennas. It can be used to rapidly evaluate the communication index degradation of RF devices within the heating environment. Moreover, a sensitivity model of the electric field strength and array antenna channel capacity to the random position error of each element is constructed. The influence of the random positioning error of each element on the communication indicators is analyzed and compared under different working conditions. The simulation results show that the proposed model can effectively provide a theoretical basis and guiding role for the design and manufacture of high-frequency array base station antennas.

Flexible, Bandwidth-Enhanced, Electrically Small, Electric Near-Field Resonant Parasitic Antenna With Filtering Performance Characteristics

In this communication, a flexible, bandwidth-enhanced, electrically small, electric near-field resonant parasitic (NFRP) filtering antenna is presented. The inherent radiation null of the dipole-driven NFRP antenna is first presented. In addition, by properly adjusting the relative position of the NFRP element and the driven dipole, this radiation null can be placed at either the lower or upper operational band edge. Then, by implementing multiple NFRP elements and properly allocating their relative positions, excellent bandpass-filtering response together with the enhanced bandwidth of the electrically small NFRP filtenna is accomplished. A prototype of the optimized design operating centered at 1.9 GHz was fabricated and measured. The simulation and experimental results are in good agreement, indicating that the antenna exhibits a wide ~11.3% impedance bandwidth with good out-of-band rejection, while maintaining its electrically small size: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ka</i> ~ 0.924. The flexibility of this antenna is experimentally analyzed under different bending conditions and the results confirm that its performance characteristics are substantially maintained.

Magnetic and electric antennas calibration for partial discharge charge estimation in gas-insulated substations

There are no accepted procedures that quantify the apparent charge of partial discharge (PD) in gas-insulated substations (GIS). This paper proposes a calibration method for PD charge estimation using unconventional electromagnetic sensors: a magnetic loop antenna (inductive coupler) and an electric antenna (capacitive coupler.) The calibration procedure is intended for the voltage double integral method, which is reviewed for magnetic antennas and extended for electric antennas. By injecting low-frequency sinusoidal signals, the calibration constants are determined for two different test setups: the first one being a testbench where the characteristic impedance is matched and the second one a full-scale 420 kV GIS. The calibration method is validated in three ways: with a calibrated pulse in the testbench, a calibrated pulse in a full-scale GIS, and PD defects in the full-scale GIS. The calibration procedure revealed a frequency limit range dependent on the GIS length and the sensor’s signal-to-noise ratio. The three validation methods showed low charge estimation errors for the magnetic and electric antennas, demonstrating that the PD calibration method applies to any electric/magnetic detector with a low-frequency derivative response. This research paves the way for better GIS insulation monitoring and PD sensor harmonization.© 2017 Elsevier Inc. All rights reserved.

Design of a low-frequency miniaturized piezoelectric antenna based on acoustically actuated principle

An acoustically actuated piezoelectric antenna is proposed for low frequency (LF) band in this paper. The proposed antenna is theoretically calculated, numerically optimized by the finite element method (FEM), and experimentally analyzed. The measurement results show that the near-field radiation pattern of the piezoelectric antenna is similar to that of the electric dipole antenna. The radiation efficiency of the piezoelectric antenna is 3–4 orders of magnitude higher than that of electrically small antenna (ESA), with their sizes being the same size, and the maximum transmission distance obtained experimentally is 100 cm, which can be improved by increasing the input power. In addition, the gain, directivity, and quality factor of piezoelectric antenna are also analyzed. In this paper, traditional antenna parameters are creatively used to analyze the performance of piezoelectric antenna. The research conclusions can provide reliable theoretical basis for realizing LF antenna miniaturization.

Active VLF Transmission Experiments Between the DSX and VPM Spacecraft

AbstractThis study presents results from magnetic field line conjunctions between the medium‐Earth orbiting Demonstration and Science Experiments (DSX) satellite and the low‐Earth orbiting (LEO) very low frequencies (VLF) Propagation Mapper (VPM) satellite. DSX transmitted at VLF toward VPM, which was equipped with a single‐axis dipole electric field antenna, when the two spacecraft passed near the same magnetic field line. VPM did not observe DSX signals in any of the 27 attempted conjunction experiments; the goal of this study, therefore, is to explain why DSX signals were not received. Explanations include (a) the predicted power at LEO from DSX transmissions was too low for VPM to observe; (b) VPM's trajectory missed the “spot” of highest intensity due to the focused ray paths reaching LEO; or (c) rays mirrored before reaching VPM. Different combinations of these explanations are found. We present ray‐tracing analysis for each conjunction event to predict the distribution of power and wave normal angles in the vicinity of VPM at LEO altitudes. We find that, for low‐frequency (below 4 kHz) transmissions, nearly all rays mirror before reaching LEO, resulting in low amplitudes at LEO. For mid‐ and high‐frequency transmissions (∼8 and 28 kHz respectively), the power at LEO is above the noise threshold of the VPM receiver (between 0.5 μV/m and 1 μV/m). We conclude that the antenna efficiency and plasmasphere model are critical in determining the predicted power at LEO, and are also the two most significant sources of uncertainty that could explain the apparent discrepancy between predicted amplitudes and VPM observations.

Miniaturized Beam Reconfigurable Reflectarray Antenna With Wide 3-D Beam Coverage

A miniaturized electrical beam-scanning reflectarray antenna providing a directional beam and wide steering ranges with fixed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> -polarization is proposed. To accomplish these properties, we devise a new active reflectarray cell that can control both the phase and polarization of incident waves. Accordingly, we can enforce all reflected waves to constructively interfere with each other in all target directions. To feed the proposed reflectarray cells, an omnidirectional monopole antenna is installed at the center of the reflectarray, which illuminates the reflectarray evenly. In addition, because the monopole feeder is directly connected to the reflectarray, we can significantly reduce the overall volume of the antenna down to about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5~\lambda ^{3}$ </tex-math></inline-formula> with a small F/D ratio of 0.147. Consequently, the proposed antenna attains a wide scan coverage and directional beam patterns. Moreover, the antenna can also maintain polarization direction stably, which is strongly required for dynamically moving platforms such as drones and unmanned aerial vehicles (UAVs). The experimental results agree well with the predictions, proving the validity of our approach.

Application of a Modified Empirical Wavelet Transform Method in VLF/LF Lightning Electric Field Signals

In this paper, to realize a better adaptive method for the lightning electric field signal denoising, we firstly compared the decomposition results of three methods called the EMD (empirical mode decomposition), the CEEMDAN (complete ensemble empirical mode decomposition with adaptive noise), and the EWT (empirical wavelet transform) by artificial signals, respectively, and found that the EWT was better than the other two methods. Then, a MEWT (modified empirical wavelet transform) method based on the EWT was presented for processing the natural lightning signals data. By using our MEWT method, we processed three types of electric field signal data with different frequency bands radiated by the lightning step leader, the cloud pulse and the return stroke, respectively, and the VLF (very low frequency) lightning signals propagating different distances from 500 km to 3500 km, by using the data of the fast electric field change sensors from Nanjing Lightning Location Network (NLLN) in 2018 and the data of the fast electric field change sensors and the VLF electric antennas from the NUIST Wide-range Lightning Location System (NWLLS) in 2021. The results showed that our presented MEWT method could adaptively process different lightning signal data with different frequencies from the step leader, the cloud pulse, and the return stroke; for the lightning VLF signal data from 500 km to 3500 km, the MEWT also achieved a better noise reduction effect. After denoising the signal by using our MEWT, the detection ability of the fast electric field change sensor was improved, and more weak lightning signals could be identified.