Multiple Resonant Modes Research Articles

Triple-Wideband Open-Slot Antenna for the LTE Metal-Framed Tablet device

An open-slot antenna with a low profile of 7 mm to provide a triple-wideband LTE operation in the metal-framed tablet device is presented. With the low profile, the antenna can fit in the narrow region between the metal frame and the display panel of the metal-framed tablet device. The triple-wideband operation covers 698–960 MHz (low band), 1710–2690 MHz (middle band), and 3400–3800 MHz (high band). The antenna mainly has a rectangular open slot and an L-shaped metal strip embedded therein to provide two open slots of different resonant paths. Using a microstrip feedline having a step-shaped section across the two open slots, good excitation of multiple slot resonant modes is obtained. Details of the proposed antenna are presented.

Compact substrate integrated waveguide filter using dual-plane resonant cells

A dual-plane resonant cell wideband bandpass filter is proposed and designed on substrate integrated waveguide (SIW) cavities using U-shape slots and H-shape fractal defected ground structure (DGS). The U-shape slots etched on the top meta layer of the SIW cavity are used to constitute a multiple-mode resonator and the H-shape fractal DGS etched on the bottom metal layer can greatly improve the filter performance while keeping the overall size of the filter circuit to be much compact. The proposed filter can lead to a size reduction of approximately one-third compared with the traditional SIW filters only using U-shape slots on the top metal plate of the SIW cavity. The filter has been fabricated and experimentally measured. The measured data are in good agreement with the simulated results. The measured 3 dB bandwidth is from 7.15 to 11.25 GHz, representing a fractional bandwidth of 44.6% at a center frequency of 9.2 GHz. Within the passband, the measured return loss performance is quite good (below −22dB), and the insertion loss is measured to be 1.05 dB, including the loss from two SMA connectors. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:111–114, 2016

Terahertz response of fractal meta-atoms based on concentric rectangular square resonators

We investigate the terahertz electromagnetic responses of fractal meta-atoms (MAs) induced by different mode coupling mechanisms. Two types of MAs based on concentric rectangular square (CRS) resonators are presented: independent CRS (I-CRS) and junctional-CRS (J-CRS). In I-CRS, each resonator works as an independent dipole so as to result in the multiple resonance modes when the fractal level is above 1. In J-CRS, however, the generated layer is rotated by π/2 radius to the adjacent CRS in one MA. The multiple resonance modes are coupled into a single mode resonance. The fractal level increasing induces resonance modes redshift in I-CRS while blueshift in J-CRS. When the fractal level is below 4, the mode Q factor of J-CRS is in between the two modes of I-CRS; when the fractal level is 4 or above, the mode Q factor of J-CRS exceeds the two modes of I-CRS. Furthermore, the modulation depth (MD) decreases in I-CRS while it increases in J-CRS with the increase in fractal levels. The surface currents analysis reveals that the capacitive coupling of modes in I-CRS results in the modes redshift, while the conductive coupling of modes in J-CRS induces the mode blueshift. A high Q mode with large MD can be achieved via conductive coupling between the resonators of different scales in a fractal MA.

Dynamics of the spatial electron density distribution of EUV-induced plasmas

We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure.

Quantitative Contact Resonance Force Microscopy for Viscoelastic Measurement of Soft Materials at the Solid-Liquid Interface.

Viscoelastic property measurements made at the solid-liquid interface are key to characterizing materials for a variety of biological and industrial applications. Further, nanostructured materials require nanoscale measurements. Here, material loss tangents (tan δ) were extracted from confounding liquid effects in nanoscale contact resonance force microscopy (CR-FM), an atomic force microscope based technique for observing mechanical properties of surfaces. Obtaining reliable CR-FM viscoelastic measurements in liquid is complicated by two effects. First, in liquid, spurious signals arise during cantilever excitation. Second, it is challenging to separate changes to cantilever behavior due to the sample from changes due to environmental damping and added mass effects. We overcame these challenges by applying photothermal cantilever excitation in multiple resonance modes and a predictive model for the hydrodynamic effects. We demonstrated quantitative, nanoscale viscoelastic CR-FM measurements of polymers at the solid-liquid interface. The technique is demonstrated on a point-by-point basis on polymer samples and while imaging in contact mode on a fixed plant cell wall. Values of tan δ for measurements made in water agreed with the values for measurements in air for some experimental conditions on polystyrene and for all examined conditions on polypropylene.

Directional side scattering of light by a single plasmonic trimer

AbstractDirectional side scattering of light by individual gold nanoparticles (AuNPs) trimers assembled by the atomic force microscope (AFM) nanomanipulation method is investigated in experiment and theory. The AFM nanomanipulation approach brings an active way to construct ultracompact and effective optical nanoantennas. Different configurations of the trimers are constructed in situ via AFM nanomanipulation. Unidirectional side scattering of light by a single trimer is demonstrated with a broad response bandwidth over 400 nm and directivity up to ∼7.8 dB in experiments. The near‐field plasmon coupling of the AuNPs is simulated with the 3D finite‐difference time‐domain method and the far‐field radiation patterns are calculated by employing near‐field‐to‐far‐field transformation methods. The calculated results are in agreement with the experiments qualitatively. The physical origin is revealed intuitively by employing a simple phenomenological “two‐dipole” model. The unidirectional light scattering is due to the interference between multiple plasmonic resonance modes of the trimers. The study contributes to the understanding of the optical response of complex nanostructures and optimizing nanoantenna performances for practical applications, e.g. increasing the detection efficiency of surface‐enhanced spectroscopy. image

Improved efficiency of ultra-thin µc-Si solar cells with photonic-crystal structures.

We investigate the improvement of the conversion efficiency of ultra-thin (~500nm-thick) microcrystalline silicon (μc-Si) solar cells incorporating photonic-crystal structures, where light absorption is strongly enhanced by the multiple resonant modes in the photonic crystal. We focus on the quality of the intrinsic μc-Si layer deposited on the substrate, which is structured to form a photonic crystal at its upper surface with a period of several hundred nanometers. We first study the crystalline quality from the viewpoint of the crystalline fraction and show that the efficiency can be improved when the deposition conditions for the μc-Si layer are tuned to give an almost constant crystalline fraction of ~50% across the entire film. We then study the influence of the photonic-crystal structure on the crystalline quality. From transmission-electron microscope images, we show that the collision of μc-Si grains growing at different angles occurs when a photonic-crystal structure with an angular surface is used; this can be suppressed by introducing a rounded surface structure. As a result, we demonstrate an efficiency of 8.7% in a ~500-nm thick, homo-junction μc-Si solar cell, which has only ~1/4 the thickness of typical μc-Si solar cells. We also discuss the possibility of further improving the efficiency by performing calculations that focus on the absorption characteristics of the fabricated cell structure.

Design of a multi-frequency resonator for UHF multiband communication applications

A new structure for RF MEMS resonators is demonstrated in UHF range. The presented resonator has the ability to work in multiple resonance modes by its specific anchor design. Also, its special electrodes are designed so that the desired mode at any time could be excited by embedding simple MOS switches. Since the resonance frequency of different modes could be adjusted by the inner radius of the resonator, the structure could be designed for wide range of arbitrary frequency differences between modes. Specific electrodes and anchors design guarantees low insertion loss and high quality factor in all modes. Modal and harmonic analysis verify our approach.

Inducing multiple Fano resonant modes in split concentric nanoring resonator dimers for ultraprecise sensing

We report on finite-difference time domain analysis of silicon split concentric ring resonator dimers (SCRRDs) with nanoscale dimensions deposited on a dielectric substrate to design all-dielectric polarization-dependent metamaterial (MM) structures. Investigating the optical response of an SCRRD on a quartz (SiO2) substrate, we verified that it can be considered as a meta-atom to design a MM. The proposed structure is able to support double sharp Fano resonances in the visible spectrum under transverse electric polarization excitation. Immersing the all-dielectric MM in various chemical liquids with different refractive indices and calculating the transmission spectra, we estimated the sensitivity of the presented MM as 497 nm/RIU and the corresponding figure of merit as 118.5. This study could help designing ultra-sensitive, low-cost and efficient bio-chemical sensors based on all-dielectric components.

Fano Resonances in Thin Metallic Grating for Refractive Index Sensing with High Figure of Merit

We theoretically present a high figure of merit (FOM) tunable surface plasmon resonance sensor device by using multiple resonance modes generated from a prism-based thin metallic grating structure at the oblique incidence in this paper. This sensor includes a thin gold film periodically pierced by narrow nanostructured slits deposited on the prism structure. The excitation of Fano-like resonance in different surfaces of metallic grating structure creates two new plasmon modes with narrow bandwidths and unique spectra features, resulting in two obvious dips in the reflection spectrum. These Fano-like resonances in the designed structure originate from the interference between surface plasmons polariton (SPP) resonance modes with different orders on the surface of metallic grating and the narrow dark resonance mode induced by asymmetric charge distribution in the metal slit. The dependence of two resonance dips on structural parameters further explains their physics mechanism, which indirectly verify that the excitation of Fano-like resonance on the top and down surfaces of metallic grating generates the two resonance dips. High bulk sensitivity and high FOM of the designed structure are also analyzed, where the narrow FWHM (full width at half maximum) of resonance dip plays an important role. We also analyze the selections of specific structure parameters to obtain high sensitivity and FOM for different refractive index range. This thin metallic grating based on surface plasmon resonance (SPR) device can be used for biochemical measurements in a wider refractive index range.

Multi-resonant wideband energy harvester based on a folded asymmetric M-shaped cantilever

This article reports a compact wideband piezoelectric vibration energy harvester consisting of three proof masses and an asymmetric M-shaped cantilever. The M-shaped beam comprises a main beam and two folded and dimension varied auxiliary beams interconnected through the proof mass at the end of the main cantilever. Such an arrangement constitutes a three degree-of-freedom vibrating body, which can tune the resonant frequencies of its first three orders close enough to obtain a utility wide bandwidth. The finite element simulation results and the experimental results are well matched. The operation bandwidth comprises three adjacent voltage peaks on account of the frequency interval shortening mechanism. The result shows that the proposed piezoelectric energy harvester could be efficient and adaptive in practical vibration circumstance based on multiple resonant modes.

Multimodal Broadband Plasmonic Absorber With Densely Packed Metallic Nanostars

A nanoplasmonic absorber consisting of a metal-dielectric-metal stack with a top layer of densely packed nanostars is designed and numerically investigated. The multimodal absorber can achieve 91% average absorption efficiency in the wavelength range of 450-700 nm. Remarkably, super absorption exhibits desirable insensitivity to both incident angles and polarization states. Electric field intensity was significantly enhanced in a nanogap region between adjacent nanostars, corresponding to an electric field enhancement factor of up to 300. Broadband absorption is attributed to the excitation of multiple resonance modes. Underlying mechanisms of individual modes were well revealed by a thorough physical analysis. The proposed absorber shows great potentials to enhance performances of various optical or optoelectronic devices.

Sensorless Control Technique for PWM Rectifiers With Voltage Disturbance Rejection and Adaptive Power Factor

This paper presents a control strategy for pulsewidth-modulation rectifiers without grid voltage sensors employing a current-shaping strategy. The proposed technique has the ability to reject harmonic components from grid voltage and power factor adaptation in the presence of uncertain grid impedance. The harmonic compensation is selective, obtained from multiple resonant modes tuned in the desired frequencies. The resulting control laws obtained by the proposed method can be easily implemented on digital processors. Aspects of robustness and performance are regarded in the control synthesis with an optimum approach for a satisfactory operation. A prototype of 1.1 kVA was implemented for experimental verification and validation.

High selectivity UWB bandpass filter with a wide notched-band

This article presents a compact ultrawideband (UWB) bandpass filter (BPF) with sharp selectivity, wide notched-band, wide out-of-band rejection, and approximately flat group delay. The proposed filter structure is composed of a U-shaped open-circuited line that is interdigitally coupled to the input/output feed-lines using high impedance lines. The structure generates multiple resonant modes across the UWB span between 3.1 and 10.6 GHz, however, high coupling between the feed-lines and the U-shaped structure transforms the discrete resonant modes into an UWB BPF. Coupling is enhanced by inserting dielectric slots in the ground-plane immediately under the coupling-lines. A wide notched-band is implemented by introducing asymmetry in the coupled lines. This was achieved by making one of the coupling lines longer by folding it and extending the line to partially couple with U-shaped structure. The length of the extended coupled line and the position of the folded section determine the center frequency of the notch-band and its 3-dB bandwidth. The notch was designed to be centered at 5.5 GHz with appropriate 3-dB bandwidth to blocking interference from WLAN signals. The selectivity of the filter was enhanced by loading the U-shaped structure with a T-shaped open-circuited stub to generate two additional resonant modes in the filter's passband and two transmission zeros that were strategically located at the upper and lower cut-off frequencies of the filter. The design was fabricated and its performance verified. The proposed filter has dimensions of 9.4 × 9.9 mm2.

HIGH-SELECTIVITY UWB FILTERS WITH ADJUSTABLE TRANSMISSION ZEROS

This letter proposes a novel ultra-wideband (UWB) bandpass filter with compact size and high-selectivity performance. The filter has been studied and implemented through multiple-mode resonator (MMR) using new coupling schemes such as capacitive source-load (S-L) coupling/inductive source-load (S-L) coupling. By properly adjusting the length and width of these stubs, its first four resonant modes can be allocated within the 3.1-10.6 GHz passband, whereas its fifth resonant mode is placed above 16.0 GHz. Two transmission zeros (an inherent transmission zero and an additional transmission zero) can be produced. Moreover, the position of the additional zero can be controlled by adjusting the direct coupling inductance/capacitance. Simulated and measured results are in good agreement indicating that the proposed BPF has a passband (3.0-11.0 GHz)/(2.92-10.6 GHz) and a wide stopband width with 23 dB/25 dB attenuation up to 27.0 GHz. The group delay of the filter is relatively constant and less than 0.65 ns/0.52 ns over the operating pass band.

Wideband Bandpass Filter Using U-Slotted Substrate Integrated Waveguide (SIW) Cavities

A wideband fifth-order bandpass filter (BPF) is proposed and designed using the U-slotted substrate integrated waveguide (SIW) cavities. The U-shape slots, etched on the SIW cavity, are used to form up a new multiple-mode resonator (MMR) in order to achieve a wide passband of operation while keeping the overall size of the filter circuit to be much compact. The proposed fifth-order SIW filter is 2.5 times in size reduction compared with the traditional fifth-order SIW filters using the single-mode SIW cavities. In order to prove the validity, one wideband SIW BPF on a single layer printed circuit board (PCB) is designed and experimentally examined. The measured results show that the filter achieves an insertion loss of 1.1 dB at 8.5 GHz, return loss of higher than 11 dB and 3 dB fractional bandwidth of 42%. The measured results are in good agreement with the simulated results.

Compact Ultra-Wide Band Bandpass Filter Design Employing Multiple-Mode Resonator and Defected Ground Structure

A compact bandpass filter (BPF) for ultra wideband (UWB) applications is proposed in this paper. The filter is consisting of two symmetrical multiple-mode resonators (MMRs) connected to quarter-wavelength parallel coupled lines in the input and output ports on the top, and a rectangular shaped defected ground structure (DGS) on the bottom of the filter. This filter provides in the passband an insertion loss of 0.2 dB and a return loss greater than 17 dB. Furthermore, the filter occupies an area of 10.42 x 2 mm2. The simulation results are in satisfactory agreement with the measurement ones reported elsewhere. The proposed UWB-BPF presents good performances in terms of insertion loss, return loss, fractional bandwidth and compact size than those reported in the literature.

Stress-Minimized Packaging of Inertial Sensors by Double-Sided Bond Wire Attachment

This paper presents a novel approach for low-stress packaging of microelectromechanical system (MEMS)-based gyroscopes. The proposed approach makes use of conventional ball-stitch wire bonding. The gyroscope die is attached exclusively by means of bond wire connections between the package frame, and the top and bottom surfaces of the die. The process enables the electrical connection of metal pads on the top and the bottom side of the MEMS die within the same process. No adhesives, glue, or solder is used for the die attach. The stiffness of the proposed die attach is evaluated by scanning laser Doppler vibrometry. White-light interferometry is used to investigate stress in the die that is induced by the die attach. The bond wire attachment is compared with conventional single-sided die attach using two types of commercially available adhesives. It was found that the proposed packaging system exhibits multiple resonance modes and displays a dependence on the amount of bond wires. White-light interferometry reveals a centered bow across the die and shows low-induced stresses compared with conventionally attached dies using epoxy adhesives.

A COMPACT MULTIBAND BOW-TIE DIPOLE SLOT ANTENNA FOR WLAN AND WIMAX APPLICATIONS

A compact multiband bow-tie dipole slot antenna fed by coplanar waveguide (CPW) is proposed in this paper. Multiple resonant mode technique and notch-band technique have been combined in this design to form triple-band operation just by adding single elements. Based on this, a pair of hairpin-shaped branches is implemented on each arm of the bow-tie slot antenna. A notch- band property is achieved compared with the original wideband bow-tie antenna (without branches). Meanwhile, a new lower resonant frequency is obtained by using this kind of structure, which means that the size is compact in nature, and the triple-band operation is achieved. The notch-band and lower resonant frequency can be tuned by changing the length of the branch. The parameters of the antenna, including reflection coefficients, current distributions, radiation patterns and gain, are achieved by numerical simulations and measurements. The results indicate that the slot size of the proposed antenna is 52. 4m m× 22.3 mm, and the proposed antenna can offer triple-band operation at 2.39-2.50 GHz (4.5%), 3.38-3.79 GHz (11.4%) and 4.87-6.23 GHz (24.5%), which is suitable for WLAN in the 2.4/5.2/5.8-GHz band and WiMAX in the 3.5/5.5-GHz bands.

Small Wideband Monopole Antenna With a Distributed Inductive Strip for LTE/GSM/UMTS

We present a small, planar, and dual-wideband antenna for handheld devices, which consists of a driven spiral monopole and a distributed inductive strip designed. A dual-wideband characteristic is realized by using a coupling feed, a distributed inductor, and a folded strip, which excite multiple resonant modes to achieve wide impedance matching. The antenna size is reduced by spiraling of the monopole and meandering and folding of the distributed inductive strip, which occupies $20 \times 15~\hbox{mm}^{2}$ . The measured antenna gains and efficiencies are over 0.75 to 1.80 dBi and 60 to 82%, respectively. Radiation patterns are approximately omnidirectional in the x-y (H) planes for all bands: the LTE800, GSM850/900, GSM1800/1900, UMTS, and LTE2300/2500 bands.