Multiple Resonant Modes Research Articles

Multi-modal vibration based MEMS energy harvesters for ultra-low power wireless functional nodes

In this work we discuss a novel design concept of energy harvester (EH), based on Microsystem (MEMS) technology, meant to convert mechanical energy, available in the form of vibrations scattered in the surrounding environment, into electrical energy by means of the piezoelectric conversion principle. The resonant structure, named four-leaf clover (FLC), is circular and based on four petal-like double mass-spring systems, kept suspended through four straight beams anchored to the surrounding Silicon frame. Differently from standard cantilever-type EHs that typically convert energy uniquely in correspondence with the fundamental vibration frequency, this particular shape is aimed to exploit multiple resonant modes and, thereby, to increase the performance and the operation bandwidth of the MEMS device. A preliminary non-optimized design of the FLC is discussed and physical samples of the sole mechanical resonator, fabricated at the DIMES Technology Center (Delft University of Technology, the Netherlands), are experimentally characterized. Their behaviour is compared against simulations performed in ANSYS Workbench™, confirming good accuracy of the predictive method. Furthermore, the electromechanical multiphysical behaviour of the FLC EH is also analysed in Workbench, by adding a layer with piezoelectric conversion properties in the simulation. The measured and simulated data reported in this paper confirm that the MEMS converter exhibits multiple resonant modes in the frequency range below 1 kHz, where most of the environmental vibration energy is scattered, and extracted power levels of 0.2 μW can be achieved as well, in closed-loop conditions. Further developments of this work are expected to fully prove the high-performance of the FLC concept, and are going to be addressed by the authors of this work in the on-going activities.

Modulated photoluminescence of graphene quantum dots in the vicinity of an individual silver nano-octahedron

We propose an effective strategy to enhance and modulate the photoluminescence (PL) of graphene quantum dots (GQDs) in the vicinity of a single silver nano-octahedron (SNO) utilizing three-dimensional finite-difference time-domain calculations. The SNO is designed to act as a multifrequency plasmonic antenna with multiple plasmon resonance modes covering multiple emission peaks of GQDs. The spectral modifications of spontaneous emission are investigated with the variations of the GQD's position and dipole moment orientation relative to the SNO. The PL colour of the GQD can be precisely adjusted between blue and green through the strong interaction with the designed antenna. The multicolour features of GQDs will also facilitate their potential applications as eco-friendly and multifunctional optical probes. The study contributes to a deeper understanding of the PL properties of GQDs near the metallic nanoparticles.

A Ka-Band Multi-Layer Parasitic Patch Array Antenna Using Low-Temperature Co-Fired Ceramic Technology

An aperture-coupled multi-layer parasitic patch array antenna operating at the Ka-band has been developed based on low-temperature co-fired ceramic technology. E-shaped parasitic patches are employed to direct the antenna radiation toward the broadside direction, thus improving the gain. Meanwhile, the parallel slots in the parasitic patches excite multiple resonant modes to broaden the bandwidth. The antenna shows a measured 10-dB impedance bandwidth of 28% (31.1 to 41.2 GHz) with a gain of >6 dBi at 31 to 38 GHz. A mutual coupling of <−18 dB is measured between adjacent elements with a center-to-center spacing of 6 mm (0.7λ0 at 35 GHz). A two-element array was also developed, which exhibits a measured 10-dB impedance bandwidth of 26% (31.5 to 40.7 GHz), as well as a gain >8.8 dBi at 31 to 37 GHz and a peak gain of 9.7 at 36 GHz. The proposed antenna achieves wide bandwidth and relatively high gain, which is suitable for millimeter-wave radars and high data-rate communication systems.

Tunable Bandpass Filter Design Based on External Quality Factor Tuning and Multiple Mode Resonators for Wideband Applications

In this paper, a tunable bandpass filter using cross-shaped multiple mode resonators (MMRs) and N:1 transformer based external quality factor tuning structures is proposed. The use of a cross-shaped MMR simplifies inter-resonators control while two Qe tuning structures are investigated and incorporated with the MMR to implement simultaneous center frequency agility and narrow and wide bandwidth tuning. Compared with traditional tunable filters, the proposed architecture requires less tuning elements and is easier to realize wideband and high-order tunable filters. Two examples (Filter I and II) are presented to validate the design. Both filters use a single MMR and six tuning elements to achieve a third-order wideband tunable filter. Filter I reports 58% center frequency tuning with constant bandwidth and 14%-64.4% fractional bandwidth (FBW) tuning when center frequency locates at 1 GHz. Filter II achieves larger frequency agility and wider FBW tuning of 82.9% and 95%, respectively, for the same bandwidth and center frequency of Filter I.

Multi-qubit parity measurement in circuit quantum electrodynamics

We present a concept for performing direct parity measurements on three or more qubits in microwave structures with superconducting resonators coupled to Josephson-junction qubits. We write the quantum-eraser conditions that must be fulfilled for the parity measurements as requirements for the scattering phase shift of our microwave structure. We show that these conditions can be fulfilled with present-day devices. We present one particular scheme, implemented with two-dimensional cavity techniques, in which each qubit should be coupled equally to two different microwave cavities. The magnitudes of the couplings that are needed are in the range that has been achieved in current experiments. A quantum calculation indicates that the measurement is optimal if the scattering signal can be measured with near single-photon sensitivity. A comparison with an extension of a related proposal from cavity optics is presented. We present a second scheme, for which a scalable implementation of the four-qubit parities of the surface quantum error correction code can be envisioned. It uses three-dimensional cavity structures, using cavity symmetries to achieve the necessary multiple resonant modes within a single resonant structure.

A novel miniaturized directly coupled UWB BPF

A novel ultra-wideband (UWB) bandpass filter (BPF) structure with directly coupled I/O ports is presented in this paper. The presented structure consists of a two-end short stepped-impedance resonator with a pair of stepped-impedance open stubs (SIOSs) and one uniform-impedance open stub (UIOS) symmetrically loaded on its high-impedance section. The presented structure has multiple resonant modes. The directly coupled configuration, the SIOSs and UIOS can provide three transmission zeros on its upper stopband, which not only improve the skirt of the upper transition band but also extend the upper stopband. As an example, an UWB BPF is designed, fabricated, and measured. The measured results show that the fabricated filter has a less than 0.7 dB insertion loss, better than 14 dB return loss and wide stopband up to 18.5 GHz. The measurement agrees well with the simulation.

Broadband bandpass filter with wide upper stopband using stub‐loaded multiple‐mode resonators

A compact wideband filter with a wide upper stopband using stub-loaded multiple-mode resonators is designed. The multimode behaviour and characteristics of the proposed filter structure are studied by conventional natural modes analysis. A prototype is designed and fabricated at 1 GHz (f 0) with 3 dB fractional bandwidths 102% and 20 dB stopband attenuation up to 10.75f 0. Good agreement between simulations and experiments is observed.

A Wideband Multilayer Quasi-Yagi Antenna with a Simplified Microstrip-to-CPS Transition Based on LTCC Technology

In this article, a wideband multilayer quasi-Yagi antenna using low temperature cofired ceramic technology is presented. The antenna is fed by a simplified microstrip-to-coplanar strip transition, which serves as balun and impedance transformer simultaneously. Multilayer directors are flared to direct the antenna propagation toward the end-fire direction. Compared with the traditional planar quasi-Yagi antenna, they can suppress the surface waves significantly and provide better director effect to improve the radiation performance. Furthermore, they excite multiple adjacent resonant modes to broaden the bandwidth. The measured results show that the proposed antenna achieves a wide bandwidth of 60% for S11 < −10 dB (26.8–49.8 GHz), better than 12 dB front-to-back ratio, smaller than 16 dB cross polarization and 4.5–6.9 dBi gain within the bandwidth. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1959–1963, 2013

Small-Size Planar LTE/WWAN Antenna and Antenna Array Formed by the Same for Tablet Computer Application

For eight-band LTE/WWAN operation (704–960/1710–2690 MHz) in the Ultrabook or thin-profile tablet computer, a planar antenna of simple structure and small size is presented. The proposed antenna is obtained by modifying a simple planar inverted-F antenna and can be printed on one surface of a thin FR4 substrate of size 10 × 45 mm2 only. The antenna's lower band bandwidth is greatly widened by embedding a proper chip capacitor of 2.7 pF at the feeding strip. This chip capacitor combines with the antenna's shorting strip can control the excitation of a parallel resonance to modify the impedance matching of the antenna's lower band such that a widened bandwidth is easily obtained to cover the LTE700/GSM850/900 operation. Conversely, the antenna's upper-band bandwidth is also greatly enhanced by using a coupled section in the antenna's radiating strip and adding a parasitic shorted strip near the feeding strip, which lead to multiple resonant modes excited to form a wide bandwidth (>1 GHz) to cover the GSM1800/1900/UMTS/LTE2300/2500 operation. Owing to its small size and simple structure, the proposed antenna is very suitable to be applied in achieving an antenna array with high isolation for MIMO or dual talk (dual WWAN) operation. Promising high-isolation antenna arrays formed by the proposed antennas are presented. The obtained isolation between the antennas in the antenna array is better than 12 dB, and the envelope correlation coefficient is less than 0.15 for frequencies over the LTE/WWAN bands. Details of the proposed antenna and antenna array are presented. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1928–1934, 2013

A novel compact dual-wideband BPF with multiple transmission zeros and super wide upper stopband

In this article, a novel miniaturised dual-wideband bandpass filter (DWB-BPF) based on two different resonators including a quasi-spiral loaded multiple-mode resonator (QSL-MMR) and L-shaped transmission line (LS-TL) is presented. At the first step, in order to design a single wideband BPF filter with controllable transmission zeros near the centre frequency, the open circuit impedance parameter of quasi-spiral loaded resonator Z21 is determined in terms of ABCD matrix. Then an equivalent circuit model of the proposed structure is derived and the impedance characteristic and electrical length of LS-TLs to achieve a DWB-BPF with excellent selectivity are calculated through even- and odd-mode analysis. The proposed filter possesses both compact and simple structure as well as two wide passbands with fractional bandwidth (FBW) of 70% and 22.8% for its first and second passbands, respectively. The proposed technique creates two transmission zeros at the lower and upper stopbands of each passband resulting in a very sharp roll-off accompanied by a wide stopband. Notably, the circuit size is reduced and the bandwidth is enhanced in comparison with its conventional counterparts. The theoretical performance of the filter is verified by the experimental one where a good agreement is reported between them.

Broadband bandpass filter using parallel-coupled microstrip line and coupled open stub resonator

A novel broadband bandpass filter with multiple resonant modes based on parallel-coupled microstrip line is proposed. The required cutoff frequency and out-of-band performance are achieved by placing L-shaped capacitive cross-coupling open stubs at the middle resonator with appropriate dimensions. A compact broadband bandpass filter of dimensions 18 × 29 mm2 is fabricated and tested for performance confirmation. The proposed filter demonstrates a wide bandwidth (from 3 to 7 GHz), as well as excellent out-of-band performance with more than 25-dB rejection up to more than 12 GHz and sharp upper cutoff frequency due to the proper location of two transmission zeros. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1640–1644, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27637

A multi-mode platform for cantilever arrays operated in liquid

A rapid and reliable multi-mode device capable of the readout of both the static and dynamic response of a micron scale cantilever array in a physiological liquid environment is presented. The resolution of the static mode is on the order of 1–2nm and in the dynamic mode it is possible to measure up to the 19th flexural resonance mode of vibration of a 500μm long and 1μm thick cantilever. Rapid measurement from the tip of the cantilevers or line scan measurement of the cantilever profiles are both possible in dual mode. The device provides sequential readout of both modes to provide the best signal to noise ratio for each mode. Proof of principle measurements are presented demonstrating the capabilities of the device and confirming the readout from both the static bending and multiple dynamic resonance modes.

FMR and Magnetic Studies on Polycrystalline YIG Thin Films Deposited Using Pulsed Laser

Ferromagnetic resonance (FMR) and magnetic studies have been carried out on polycrystalline YIG films deposited by pulsed laser deposition (at TS:750 °C, O2:5×10-2 mbar) using a range of laser energies (240 to 350 mJ). The films were ex situ annealed (Ta:700 °C, in air for 2 h). The film thickness increases from 100 to 290 nm for an hour of deposition with the increase in laser energy from 240 to 350 mJ. The FMR linewidth was found to reduce from 340 to 70 Oe for the same incremental variation in laser energy. Multiple resonance modes were observed in the perpendicular FMR spectra of our samples which are related to intrinsic as well as extrinsic mechanisms such as in homogeneities. Saturation magnetization measurement (Ms) is found to be dependent on the laser energy. The value of Ms is found to increase with laser energy and is close to 90% of the bulk value for the film with highest power. An attempt has been made to correlate the magnetization results with the microstructure.

Design of a Superconducting Ultra-Wideband (UWB) Bandpass Filter With Sharp Rejection Skirts and Miniaturized Size

This letter presents a superconducting ultra-wideband (UWB) bandpass filter (BPF) with sharp rejection skirts and miniaturized size using multiple-mode resonator (MMR). The MMR is formed by loading a stepped-impedance open-end stub in shunt to a modified stepped-impedance resonator (SIR). The modified SIR generates three resonant modes within the 3.1-10.6 GHz UWB band, whereas the stepped-impedance open-end stub creates two transmission zeros and two additional resonant modes improving the bandedge steepness. Interdigital coupled-lines are used for the external couplings to enhance the coupling strength. A superconducting UWB BPF is realized with a compact size of 20 mm × 11 mm. The measured results without any tuning show good performance. The insertion loss at the center frequency is 0.58 dB, the return loss is greater than 10.6 dB, and the group delay variation is less than 1.76 ns. Furthermore, the experimental results of the filter are in good agreement with the simulated ones.

Multi-resonant plasmonic nanodome arrays for label-free biosensing applications

The characteristics and utility of plasmonic nanodome arrays capable of supporting multiple resonance modes are described. A low-cost, large-area replica molding process is used to produce, on flexible plastic substrates, two-dimensional periodic arrays of cylinders that are subsequently coated with SiO2 and Ag thin films to form dome-shaped structures, with 14 nm spacing between the features, in a precise and reproducible fashion. Three distinct optical resonance modes, a grating diffraction mode and two localized surface plasmon resonance (LSPR) modes, are observed experimentally and confirmed by finite-difference-time-domain (FDTD) modeling which is used to calculate the electromagnetic field distribution of each resonance around the nanodome array structure. Each optical mode is characterized by measuring sensitivity to bulk refractive index changes and to surface effects, which are examined using stacked polyelectrolyte layers. The utility of the plasmonic nanodome array as a functional interface for biosensing applications is demonstrated by performing a bioassay to measure the binding affinity constant between protein A and human immunoglobulin G (IgG) as a model system. The nanoreplica molding process presented in this work allows for simple, inexpensive, high-throughput fabrication of nanoscale plasmonic structures over a large surface area (120 × 120 mm(2)) without the requirement for high resolution lithography or additional processes such as etching or liftoff. The availability of multiple resonant modes, each with different optical properties, allows the nanodome array surface to address a wide range of biosensing problems with various target analytes of different sizes and configurations.

A NOVEL COMPACT SIZE UWB BANDPASS FILTER WITH SHARP REJECTION SKIRT AND WIDE UPPER-STOPBAND BASED ON MULTIPLE-MODE-RESONATOR

In this paper, a novel ultra-wideband (UWB) bandpass fllter (BPF) based on multiple-mode resonator (MMR) is presented. The structure of the proposed MMR constructed by a modifled triple- mode stepped-impedance resonator (SIR) loaded with a T-shape stub. This stub-loaded resonator can generate two more resonate modes and two transmission zeros (TZs) simultaneously. Five resonate modes of the proposed MMR are roughly allocated in the UWB pass band, as well as two TZs at the lower and upper cut-ofi frequencies of the passband, leading to sharp roll-ofi. Using aperture-backed interdigital- coupled lines for feeding, passband is realized, flrst harmonic resonate mode (sixth mode) suppressed by flrst TZ of the interdigital-coupled lines, and upper stopband extended. Resonant modes and TZs are discussed together. Finally, the proposed fllter is fabricated and measured, and predicted results verifled in measurement.

DESIGN FILTERS USING TUNABLE E-SHAPED DUAL-MODE RESONATORS FOR LOWER-ULTRA-WIDEBAND AND UPPER-ULTRA-WIDEBAND APPLICATIONS

Two ultra-wideband (UWB) microstrip bandpass fllters (BPFs) are proposed by using tunable E-shaped dual-mode microstrip Stepped-Impedance Resonator (SIR). For the lower band fllter measurement results show there is a passband of 3.1GHz to 5.2GHz and its 3dB fractional bandwidth is 51%. The UWB upper band fllter may be obtained by tuning E-shaped SIR. The measurement results show there is a passband of 6GHz to 10.6GHz and its 3dB fractional bandwidth is 55%. Compared with the similar investigation using the cascade of electromagnetic band gap (EBG)-embedded multiple-mode resonator (MMR) and fork resonator, the proposed approach has some advantages, such as easier adjustment of bandwidths, better passband performances and smaller size etc..

Small-Size Wideband Monopole With Distributed Inductive Strip for Seven-Band WWAN/LTE Mobile Phone

An on-board coupled-fed printed monopole with a distributed inductive shorted strip for seven-band operation covering the GSM850/900/1800/1900/UMTS2100/LTE2300/2500 bands in the mobile phone is presented. The presented antenna consists of a feeding strip and a distributed inductive shorted strip (formed by a printed distributed inductor and a simple shorted strip). By the coupled-fed excitation, the proposed antenna can generate multiple resonant modes at lower and upper bands for seven-band WWAN/LTE operation covering 824–960/1710–2690-MHz bands. The proposed antenna only occupies a size of 15 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\,\times\,$</tex></formula> 29 mm <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{2}$</tex></formula> and is easily printed on the top of an FR4 substrate, which makes it suitable for practical mobile applications. The proposed antenna was fabricated and tested. Measured and simulated results are presented.

Enhanced Light Trapping in Periodic Aluminum Nanorod Arrays as Cavity Resonator

ABSTRACTMetallic nanostructures can exhibit different optical properties compared to bulk materials mainly depending on their shape, size, and separation. We present the results of an optical modeling study on ordered arrays of aluminum (Al) nanorods with a hexagonal periodic geometry placed on an Al thin film. We used a finite-difference time-domain (FDTD) method to solve the Maxwell's equations and predict the reflectance of the nanorod arrays. The thickness of the base Al film was set to 100 nm, and diameter, height and nanorod center-to-center periodicity were varied. Incident light in the FDTD simulations was an EM-circular polarized plane wave and reflectance profiles were calculated in the wavelength range 200-1800 nm. In addition, we calculated spatial electric field intensity distributions around the nanorods for wavelengths 300, 500, and 700 nm. Our results show that average reflectance of Al nanorods can drop down to as low as ∼50%, which is significantly lower than the ∼90% reflectance of conventional flat Al film at similar wavelengths. In addition to the overall decrease in reflectance, Al nanorod arrays manifest multiple resonant modes (higher-order modes) indicated by several dips in their reflectance spectrums (i.e. multiple attenuation peaks in their absorption profiles). Positions of these dips in the reflectance spectrum and spatial EM field distribution vary with nanorod height and diameter. Multiple reflectance peaks are explained by cavity resonator effects. Spatial EM field distribution profiles indicate enhanced light trapping among the nanorods, which can be useful especially in optoelectronic and solar cell applications.

Investigation of Mutual Coupling Effects in Conventional and Fractal Capacitive Coupled Suspended RMSAs

An array of coplanar capacitive coupled suspended microstrip antenna has been investigated to study the mutual coupling effect between its elements. Also, the work is extended to study the mutual coupling effect in Koch shaped coplanar capacitive coupled suspended fractal microstrip antenna. From the investigations it is observed that less coupling effect occurs between the elements in fractal array. This study reveals the use of fractal geometries in place of conventional (regular) shapes because of their numerous advantages like self similarity property, ability to excite multiple resonant modes etc. Antenna arrays are simulated using IE3D software from Zeland which is based on Method of Moments (MoM).