Parallel Plate Resonator Research Articles

Eliminating sensing blind spots of field-enhanced Rydberg atomic antenna via an asymmetric parallel-plate resonator

Due to its large electric dipole moment, the Rydberg atom exhibits a strong response to weak electric fields, hence it is regarded as a highly promising atomic antenna. However, to enhance the reception sensitivity, split-ring resonators are needed normally, which will brings sensing blind spots. Thus it is not conducive to the application of full-coverage space communication. Here we propose that an atomic antenna with an asymmetric parallel-plate resonator, can not only enhance the received signal, but also eliminate sensing blind spots (pattern roundness can reach 7.8 dB while the split-ring resonator can be up to 39 dB). We analyze the influence of structural parameters on the field enhancement factor and directionality, and further discuss the limitation of the sensitivity by using thermal resistor noise theory. This work is expected to pave the way for the development of field-enhanced Rydberg atomic antennas that communicate without a blind spot.

Quantitative Operando 7Li NMR Investigations of Silicon Anode Evolution during Fast Charging and Extended Cycling.

The development and optimization of fast battery charging protocols require detailed information regarding lithium speciation inside a battery. Nuclear magnetic resonance (NMR) spectroscopy has the unique capability of identifying the Li phases formed in an anode during Li-ion cell operation and quantifying their relative amounts. In addition, both Li metal films and dendrites are readily detected and quantified. Here, our recently reported parallel-plate resonator radio frequency (RF) probe and the cartridge-type single-layer full cell were used to track the behavior of Si electrodes during cycling and during fast charging. The LixSi compounds formed during electrochemical cycling exhibit an unexpected intrinsic nonequilibrium behavior at both slow and fast rates, evolving toward increasingly disordered local environments. The evolution with time of lithiated phases is nonlinear during both charging and discharging at constant current, unlike the case for pure graphite, and asymmetric between charge and discharge. During charging at rates of 1C, 2C, and 3C, metallic Li in both films and (to a lesser extent) dendritic forms are deposited on the Si anode. Part of the Li metal film formation is reversible, but a fraction remains on the electrode surface as dead Li, while all of the dendritic Li, even though formed in a considerably smaller amount, is entirely irreversible. Such performance-governing properties are critical to the development of fast-charging protocols for lithium-ion batteries (LIBs) and are exceptionally well evaluated and quantified by 7Li magnetic resonance strategies such as those presented here.

A Novel Parallel-Plate Dielectric Resonator Method for Broadband Complex Permittivity Measurement in the Millimeter-Wave Bands

This article proposes a novel measurement method based on parallel-plate dielectric resonator (PPDR) for determining complex permittivity of low-loss dielectric materials over a wide frequency range. Two 1.0-mm coaxial probes are placed symmetrically as a coupling structure in the center of top and bottom of the PPDR, and only the TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm{0np}}$</tex-math> </inline-formula> resonant modes will be selectively excited. For each value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$</tex-math> </inline-formula> , the resonator will operate over a specific frequency range, within which there are usually multiple frequency points available for testing. Based on this unique feature, dielectric constants of cylindrical or disk-shaped samples can be measured from less than 20 up to 110 GHz by utilizing TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm{0np}}$</tex-math> </inline-formula> high-order modes. Rigorous analysis of the PPDR based on the electromagnetic field matching method is carried out and verified numerically. Moreover, the PPDR method is further validated experimentally by measuring several specimens processed from well-known materials, the main sources of measurement uncertainty are also analyzed in detail, and some recommendations are made accordingly. The results show that the PPDR method can perform high-accuracy measurement of complex permittivity in the millimeter-wave bands, even when the sample thickness exceeds the maximum value limited by the current state of the art.

The parallel-plate resonator: An RF probe for MR and MRI studies over a wide frequency range

We explore the use of the parallel-plate resonator for the study of thin cuboid samples over a wide range of magnetic resonance frequencies. The parallel-plate resonator functions at frequencies from tens to hundreds of MHz. Seven parallel-plate resonators are presented and discussed in a frequency range from 8 to 500 MHz. Magnetic resonance experiments were performed on both horizontal and vertical bore magnet systems with lithium and hydrogen nuclei. Parallel-plate radiofrequency (RF) probes are easy to build and easy to optimize. Experiments and simulations showed good sensitivity of the parallel-plate RF probe geometry with a small decrease in sensitivity at higher frequencies.

Characterization of the Parameters of Superconducting NbN and NbTiN Films Using Parallel Plate Resonator

This work is dedicated to the determination of parameters of superconducting NbN and NbTiN films such as critical temperature, normal state conductivity, ratio between the gap and critical temperature and parameter incorporating the quasiparticle states inside the gap that emerge due to strong-coupling effects. The measurements were performed using a parallel plate resonator method. From the experiment, the dependence of London penetration depth on temperature was obtained. The experimental data were fitted using the expressions of Mattis-Bardeen theory extended by the consideration of strong-coupling effects. In order to design the experimental setup and visualize the results a modeling in Ansys HFSS was performed.

Transient lithium metal plating on graphite: Operando7Li nuclear magnetic resonance investigation of a battery cell using a novel RF probe

The development of optimal fast charging protocols requires detailed information regarding lithium inventory in a battery. We built a parallel-plate resonator RF probe and a cartridge-type single layer cell of improved designs. The probe has excellent sensitivity and homogeneity of electromagnetic field, while the cartridge allows easy cell assembly, straight-forward multiplexing, and excellent cell-to-cell data reproducibility. Herein we present our findings from operando7Li NMR measurements on a graphite//NMC622 cell. The usual/expected sequencing of LixC6 phases from dilute to concentrated observed during charging at low (<C/5) rates is replaced at high (≥1C) rates by a direct transition to, and propagation of concentrated phases throughout the graphite electrode, with no evidence for dilute phases. Concurrently, a peak attributed to lithium naphthalenide appears at ∼20 ppm. Lithium therefore accumulates on graphite surfaces, facilitating Li metal plating under fast charge conditions. While some of the deposited Li metal can intercalate into graphite after cell charging, a significant fraction accumulates during consecutive cycles, creating a barrier for Li+ transport, which decreases the amount of recoverable Li, and its intercalation rate into graphite. Thus, Li plating not only can create safety hazards through dendrite growth, but also irreversibly impairs the fast charging capability of cells.

Wideband Low-Profile Dual-Polarized Phased Array With Endfire Radiation Patterns for 5G Mobile Applications

In this paper, an endfire dual-polarized phased array is introduced for 5G mobile applications, which operates from 26 GHz to 30 GHz with low profile of only 1.1 mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bf 0.1\lambda _0}$</tex-math></inline-formula> at 26 GHz) and small clearance of 3.5 mm. The array consists of interleaved substrate integrated waveguide (SIW) based vertical-polarized elements and notch type horizontal-polarized elements. The bandwidth of each SIW element is greatly improved by introducing a wide-band impedance transition, which is composed by parallel plate resonators and a metallic via in between. The notch elements have very compact size, which helps to keep the half-wavelength inter-element distance. The array has a planar structure and is easy to fabricate. The measured and simulated results align well with each other.

Compact Dual Microwave/Millimeter-Wave Planar Shared-Aperture Antenna for Vehicle-to-Vehicle/5G Communications

This paper presents a compact dual-port dual-frequency planar shared-aperture antenna with large frequency ratio. It consists of a microwave magneto-electric (ME) dipole antenna and a millimeter-wave parallel-plate resonator antenna (PPRA). It has two vertical conducting walls that form an upper-band parallel-plate resonator and meanwhile provide a magnetic source to the lower-band ME dipole. The design is a shared-aperture structure and is therefore very compact. For demonstration, a dual-frequency antenna simultaneously covering the 5.9-GHz vehicle-to-vehicle (V2V) band (5.855-5.925 GHz) and the 28-GHz 5G band (27.5-28.35 GHz) was designed, fabricated, and measured. Good agreement between the measured and simulated results was found. The lower and upper bands have the measured 10-dB impedance bandwidths of 41.6% (5.30-8.08 GHz) and 6.66% (27.15-29.02 GHz), and measured peak antenna gains of 5.80 dBi and 8.46 dBi, respectively. The antenna can be used on vehicular platforms for providing V2V communications and 5G millimeter-wave connections simultaneously.

A parallel-plate RF probe and battery cartridge for 7Li ion battery studies

A new parallel-plate resonator for 7Li ion cell studies is introduced along with a removable cartridge-like electrochemical cell for lithium ion battery studies. This geometry separates the RF probe from the electrochemical cell permitting charge/discharge of the cell outside the magnet and introduces the possibility of multiplexing samples under test. The new cell has a geometry that is similar to that of a real battery, unlike the majority of cells employed for MR/MRI studies to this point. The cell, with electrodes parallel to the B1 magnetic field of the probe, avoids RF attenuation during excitation/reception. The cell and RF probe dramatically increase the sample volume compared to traditional MR compatible battery designs. Ex situ and in situ 1D 7Li profiles of Li ions in the electrolyte solution of a cartridge-like cell were acquired, with a nominal resolution of 35 µm at 38 MHz. The cell and RF probe may be employed for spectroscopy, imaging and relaxation studies. We also report the results of a T1-T2 relaxation correlation experiment on both a pristine and fully charged cell. This study represents the first T1-T2 relaxation correlation experiment performed in a Li ion cell. The T1-T2 correlation maps suggest lithium intercalated into graphite is detected by this methodology in addition to other Li species.

Electromagnetic Signature of a Quadcopter Drone and Its Relationship With Coupling Mechanisms

This paper presents an investigation of the electromagnetic signature and the coupling mechanism of quadcopter drones with incident electromagnetic (EM) wave and radar cross section (RCS) analysis. Coupling analysis is performed based on the dominant coupling path: when an incident EM wave with a magnitude of 50 kV/m contacts a commercial quadcopter drone, its motor power wires are identified as the dominant coupling path. Higher coupling voltages are obtained for frequencies that have large impedance values at both ends of the load on the motor power wire. This induced voltage can affect the integrated circuit chip on a printed circuit board, as well as parallel plate resonances. Furthermore, the RCS of a quadcopter drone is measured in the frequency range of 0.5-3 GHz. The internal-component vulnerability characteristics of quadcopters can spike at specific frequencies with high RCS values and can be analyzed with or without motor power wires. We verified these hypotheses via 2D inverse synthetic aperture radar images, and we analyzed the results by comparing the empirical and full-wave simulation values.

Metallic mesh devices-based terahertz parallel-plate resonators: characteristics and applications.

The capability to design, fabricate, and optimize metamaterials based on various structures and material platforms has been crucial for the rapid development of modern terahertz (THz) technology. While the detailed structures of artificial unit cells within a metamaterial is certainly worth investigating, there has been increasing demand to integrate novel metamaterials with a traditional functional photonic device to form a hybrid device, whose performance is so significantly improved as to be promising for real-world applications. In this study, we proposed, for the first time, a THz parallel-plate resonator based on metallic mesh devices (MMDs) for chemical sensing applications. We studied the influences of various structural parameters through simulations, fabricated MMD-based resonator devices, and fully characterized the device performance through THz spectroscopy experiments. Furthermore, we experimentally demonstrated that our device can detect a doxycycline hydrochloride aqueous solution whose concentrations is as low as 1 mg L-1 through resonance frequency shifts, evidencing the device sensitivity capable of delicate chemical sensing tasks. Our work presents a practical and low cost architecture for chemical sensing using THz radiation, which opens new avenues for numerous useful THz devices based on metamaterials.

A Method for the Suppression of Multiple Spurious Modes

This paper reports on a novel electrode design technique for spur suppression in parallel-plate piezoelectric resonators with minimal impact on the intended vibration mode. To demonstrate this technique, fabricated two-port resonators were designed to optimally excite the first harmonic of length extension in a lead zirconate titanate-on-silicon resonator and suppress chosen higher harmonics. The targeted harmonics have been largely suppressed, while the intended mode experienced no change in magnitude. This is the first step towards a general technique for suppression of an arbitrary mode. [2017–0251]

Impact of excitation waveform on the frequency stability of electrostatically-actuated micro-electromechanical oscillators

In this paper, the frequency stability of high-Q electrostatically-actuated MEMS oscillators with cubic restoring forces, and its relation with the amplitude, the phase and the shape of the excitation waveform, is studied. The influence on close-to-the carrier frequency noise of additive processes (such as thermomechanical noise) or parametric processes (bias voltage fluctuations, feedback phase fluctuations, feedback level fluctuations) is taken into account. It is shown that the optimal operating conditions of electrostatically-actuated MEMS oscillators are highly waveform-dependent, a factor that is largely overlooked in the existing literature. This simulation-based study covers the cases of harmonic and pulsed excitation of a parallel-plate capacitive MEMS resonator.

BLIPPED (BLIpped Pure Phase EncoDing) high resolution MRI with low amplitude gradients

MRI image resolution is proportional to the maximum k-space value, i.e. the temporal integral of the magnetic field gradient. High resolution imaging usually requires high gradient amplitudes and/or long spatial encoding times. Special gradient hardware is often required for high amplitudes and fast switching. We propose a high resolution imaging sequence that employs low amplitude gradients.This method was inspired by the previously proposed PEPI (π Echo Planar Imaging) sequence, which replaced EPI gradient reversals with multiple RF refocusing pulses. It has been shown that when the refocusing RF pulse is of high quality, i.e. sufficiently close to 180°, the magnetization phase introduced by the spatial encoding magnetic field gradient can be preserved and transferred to the following echo signal without phase rewinding. This phase encoding scheme requires blipped gradients that are identical for each echo, with low and constant amplitude, providing opportunities for high resolution imaging. We now extend the sequence to 3D pure phase encoding with low amplitude gradients.The method is compared with the Hybrid-SESPI (Spin Echo Single Point Imaging) technique to demonstrate the advantages in terms of low gradient duty cycle, compensation of concomitant magnetic field effects and minimal echo spacing, which lead to superior image quality and high resolution. The 3D imaging method was then applied with a parallel plate resonator RF probe, achieving a nominal spatial resolution of 17 μm in one dimension in the 3D image, requiring a maximum gradient amplitude of only 5.8 Gauss/cm.

Development of two dielectric sensors coupled with computational techniques for detecting milk adulteration

Milk adulteration is a challenging concern which leads to economic losses, quality deterioration of the end products in dairy industry, and consequently public health risks. The demands for reliable and fast methodologies have been already increased in dairy industry. Therefore, developing simple, rapid, and reliable instrumental methods is a necessity for detecting the milk adulterations. This research effort was aimed to combine the sensor technology with computational techniques for the milk adulteration detection. For this purpose, two dielectric sensors, parallel-plate (PPC) and cylindrical stub resonator (CS), were developed and evaluated to examine a number of prevalent milk adulterations (sodium bicarbonate, water, sugar, urea, and gelatin) with a range of variation. Dielectric power and amplitude were recorded versus frequency (swept within 0–150MHz) for the PPC and CS sensors, respectively. The spectral data were then analyzed using some computational approaches consisted of SPLINE (moving cubic spline), NIPALS (principal component analysis), CLASS (classification and class modelling techniques), MRM (multivariate range modelling), TREE (classification trees), and PLS2 (correlation between blocks of variables)). Based on the results, the dielectric power spectra of the PPC sensor showed the frequency range of 15–60MHz as the most sensitive band with respect to different adulterations and the amplitude-frequency response of the CS sensor revealed remarkable changes in the amplitude at the resonance frequencies. According to the data analysis, for PPC, two matrices were studied, with different range of the frequencies and it was proved that the data matrix with 145 variables has more discriminant information. Also, in the case of PPC data, classification tree showed the best result with 80% prediction ability for the milk samples while full classification accuracy was found for CS data. As a consequence, it was concluded that the adulterations in milk can be screened by both sensors coupled with computational techniques. Therefore, the methodologies presented here could be considered as a candidate for potential use in dairy industry.

In-situ electron paramagnetic resonance studies of paramagnetic point defects in superconducting microwave resonators

The physical nature and concentration of paramagnetic point defects in the dielectrics of superconducting planar microwave resonators have been determined using in-situ electron paramagnetic resonance spectroscopy. To perform this work, the quality factor of parallel plate and stripline resonators was measured as a function of the magnitude of a magnetic-field applied parallel to the electrode surfaces. YBa2Cu3O7−δ thin film electrodes proved to be a preferred choice over Nb and MgB2 because they are readily available and have a small surface resistance (Rs) up to high temperatures (∼77 K) and magnetic fields (i.e., &amp;lt;1 T). Stripline resonators with a widely used high performance microwave dielectric, Co2+-doped Ba(Zn1/3Nb2/3)O3, are shown to have losses dominated by d-electron spin-excitations in exchange-coupled Co2+ point-defect clusters, even in the absence of an applied magnetic field. A significant enhanced microwave loss in stripline and parallel plate resonators is found to correlate with the presence of paramagnetic Mn2+ dopants in Ba(Zn1/3Ta2/3)O3 ceramics and dangling bond states in amorphous Si thin films, although the identification of the dominant loss mechanism(s) in these dielectrics requires further investigation.

Dual-Frequency Folded-Parallel-Plate Antenna With Large Frequency Ratio

This communication investigates a new compact dual-frequency antenna with a large frequency ratio, which consists of a pair of folded parallel plates. It integrates the microwave parallel-plate waveguide resonator antenna (WRA) with the millimeter-wave Fabry-Perot resonator antenna (FPRA), with their resonant frequencies independent of each other. Due to the folded structure, the profile of the proposed antenna is lower than that of the conventional parallel-plate WRA. The WRA part is excited by a hook-shaped strip on its top, whereas the FPRA is excited by an L-probe with a half-ring sleeve. To demonstrate the idea, a dual-frequency antenna that covers the 2.4- and 24-GHz ISM bands was designed. ANSYS HFSS was used to simulate the S-parameters, radiation pattern, and antenna gain and reasonable agreement between the measured and simulated results is obtained.

Study of the onset of the acoustic streaming in parallel plate resonators with pulse ultrasound

In a previous study, we introduced pulse mode ultrasound as a new method for reducing and controlling the acoustic streaming in parallel plate resonators (Hoyos and Castro, 2013). Here, by modifying other parameters such as the resonator geometry and the particle size, we have found a threshold for particle manipulation with ultrasonic standing waves in confined resonators without the influence of the acoustic streaming. We demonstrate that pulse mode ultrasound open the possibility of manipulating particles smaller than 1μm size.

Analysis of resonant pull-in of micro-electromechanical oscillators

In this paper, the equations governing the pull-in of electrostatic (micro-electromechanical systems MEMS) oscillators are established and analyzed. This phenomenon defines the maximal oscillation amplitude that can be obtained without incurring instability and, hence, an upper limit to the performance of a given device. The proposed approach makes it possible to accurately predict pull-in behavior from the purely resonant case, in which the electrostatic bias is very small, to the static case. The method is first exposed in the case of a parallel-plate resonator and the influence of the excitation waveform on the resonant pull-in characteristics is assessed. It is then extended to the more complex case of clamped–clamped and cantilever beams. The results are validated by comparison with transient simulations.

RF breakdown test of diamond-loaded resonator for high gradient wakefield accelerator applications

Dielectric-loaded accelerating structures (DLAs) for wakefield applications are an alternative to conventional corrugated metal structures. These structures have simple geometry, scale up to THz frequencies, and feature higher breakdown threshold. Diamond has been proposed as a loading material for DLAs due to a number of its unique thermal, microwave, and electrical properties. In this paper we report results of a wakefield breakdown test of a single crystal diamond resonator. A large, 72nC, charge beam with 2.5mm length, 8.6 kA peak current was transmitted through a diamond-loaded parallel plate resonator, and induced a standing wave with a 70MV/m electric field strength. One of the diamond plates had a laser cut, 20μm wide and 200μm deep groove, that provided an additional ~5-fold field enhancement at edges of the groove resulting in an electric gradient as high as 0.3GV/m on the surface of the groove. SEM and x-ray topography analyses before and after the test did not reveal any structural damage to the diamond resonator plates. This corroborates further promotion of diamond for high gradient wakefield acceleration at high repetition rates.