Non-uniform Resonators Research Articles

Resonance and Bragg band frequencies coupling of lossy sonic crystals based on nonuniform resonators and lattice

Traditional sonic crystals (SCs) are based on scatterers or resonators distributed periodically that attenuate sound waves in different bands of frequencies. Recently, we adopted an improved design of SC, namely, the gradient-based sonic crystal (GBSC), designed with a gradient in the geometric parameters using nonuniform resonators and lattices. The finite element (FE) study on the GBSCs indicated that the gradient induces better attenuation than the traditional periodic SCs. This work is an extension of our previous work with experimental and new FE studies on different parameters of the GBSC in an attempt to improve the attenuation of the GBSCs. It was found that the gradient of the geometry enhances the Bragg scattering and resonance in the array, creating a large number of band frequencies. When designed properly by manipulating their gradient, GBSCs were found to target particular frequency bands over other GBSCs of identical filling ratios by coupling the resonant frequencies or the resonant and Bragg frequencies. It was also found that the thickness of the GBSC can be reduced by removing some specific columns from the array without significantly affecting the attenuation by the GBSC. Similarly, it was also found that the relative position of the resonator columns in a GBSC affects the band frequencies, and swapping the columns may also improve the attenuation by the GBSC.

Acoustic coding metamaterial based on non-uniform Mie resonators

Acoustic coding metamaterials have important applications in simplifying design procedure and providing a flexible approach to realize complicated functions. Here, we design a 1-bit coding metamaterial for flexibly manipulating the sound propagation path. The capability of subwavelength acoustic propagation control on coding metamaterial is attributed to the dipole-like characteristic of the Mie resonator. The Mie resonator with a subwavelength scale is constructed with a non-uniform structure, which can generate Mie resonance with dipole-like characteristic. Two kinds of coding elements are introduced by horizontally or vertically reversing the Mie resonator in each element. To verify the performance of the designed coding metamaterials, three specific metamaterial patterns are fabricated to give different trajectories of sound propagation. Our finding may open an avenue for designing acoustic metamaterials and is expected to design intelligent acoustic devices with exciting reconfigurable and programmable applications.

Realization of real-time directional radiation of acoustic wave with non-uniform Mie resonators

In this study, we present a tunable metamaterial consisting of rotatable non-uniform Mie resonators (NMRs) with identical structures. The metamaterial can in real-time manipulate the direction of acoustic radiation and guarantee high transmission efficiency by simply changing the rotation angle of the NMR unit cells, which is induced by the anisotropic property of NMR. In addition, according to generalized Snell’s law, the arbitrarily direction-scanning capability is realized by tuning the phase shift distribution along the metamaterial. Our proposed anisotropic metamaterial could contribute to designing a device for the emission and reception of acoustic waves in real-time.

A Novel Design of Compact Dual-Band Bandpass Filter for Wireless Communication Systems

In this paper, design, fabrication, and measurement of a new microstrip dual-band bandpass filter with compact size and high selectivity characteristics for modern wireless communication systems is presented. The filter structure is composed of folded non-uniform meander resonators along with defected ground structure patterns. The proposed filter with a total size of 14.43 × 9.04 mm2 is designed to exhibit two passbands centered at 2.18 GHz and 5.12 GHz with fractional bandwidths of 16.2% and 6.48%, respectively. The measured insertion losses are about 1.13 dB and 2.65 dB at the lower and upper passband, respectively. The simulation and experimental measurement results are basically in good agreement which validate the proposed approach.

Analysis of thermoelastic damping in the clamped-free microbeam with linearly tapered circular cross-section

An accurate estimation of thermoelastic damping (TED) is of significance and importance in the design for the microbeam resonators with variable cross-section operated in vacuum. TED determines the up limit of quality factor (Q-factor) used for evaluating the microresonator performance. However, in the past, the previous works focus on the TED modelling of uniform microbeam resonators with rectangular cross-section. There is lack of works aiming at the TED modelling of non-uniform microbeam resonators with circular cross-section. In addition, the previous TED model developed by Zener for uniformly circular cross-section beams is not suitable for calculating TED values of the non-uniform beams. Therefore, the TED model for clamped –free microbeam resonators with linearly tapered circular cross-section is meaningful to be derived in this work. The radius and length dependences of TED are investigated. The results of finite element method (FEM) model are calculated for purpose of comparison. Results indicate that for large aspect ratio (l/r0), TED values of linearly tapered microbeams with circular cross-section are larger than those of uniform microbeams, while for small aspect ratio (l/r0), TED values of linearly tapered microbeams are lower than those of uniform microbeams. Moreover, the maximum values of TED called Debye peaks in linearly tapered microbeams are lower than those of uniform microbeams.

High-frequency microstrip dual-band bandpass filter fabricated using FR-4 glass epoxy material

In this paper, design, fabrication and measurement of a novel microstrip dual-band bandpass filter (BPF) structure with a compact size using FR-4 glass epoxy material is presented. The filter structure is composed of folded non-uniform meander resonators. The proposed filter with a total size of 0.24λg × 0.16λg is designed to exhibit two passbands centred at 2.68 GHz and 5.64 GHz with fractional bandwidths of 25.38% and 10.4%, respectively. The simulation and experimental measurement results are basically in good agreement which validate the proposed approach.

Thermoelastic Damping in Cone Microcantilever Resonator

Microbeams with continuous or discontinuous variable cross-section have been applied in Microelectromechanical Systems (MEMS) resonators, such as tapered microbeam, torsion microbeam and stepped microbeam. Thermoelastic damping (TED), which is verified as a fundamental energy lost mechanism for microresonators, is calculated by the Zener’s model and Lifshits and Roukes’s (LR) model in general. However, for non-uniform microbeam resonators, these two classical models are not suitable in some cases. On the basis of Zener’s theory, a TED model for cone microcantilever with rectangular cross-section has been derived in this study. The comparison of results obtained by the present model and Finite Element Method (FEM) model proves that the proposed model is able to predict TED value for cone microcantilever. In addition, TED in cone microcantilever is nearly same as TED in wedge microcantilever. The results show that quality factors (Q-factors) of cone microcantilever and wedge microcantilever are larger than Q-factor of uniform microbeam at low frequencies. The Debye peak value of a uniform microcantilever is equal to 0.5ΔE, while those of cone microcantilever and wedge microcantilever are about 0.438ΔE and 0.428ΔE, respectively.

Design and measurements of variably nonuniform acoustic resonators

We describe the design, construction, and acoustical measurements of resonators with nonuniform cross-sectional areas that are easily altered to yield different resonance frequencies. These resonators are useful as educational demonstrations of symmetry breaking and of an effect of nonuniformity upon standing waves. Resonators that yield two, three, and four pitches are considered, where the relative frequencies are designed to correspond to musical intervals. Agreement is within 2% in all cases and 1% for most. The data reveal a breakdown of the theory, which is shown to be a result of additional kinetic energy, and thus effective inertia, near a discontinuity in cross-sectional area. The data also reveal that it is more accurate accurate to employ the end correction of an infinite flange rather than that of a thin-walled tube.

Design and measurements of variably nonuniform acoustic resonators.

The design, construction, and acoustical measurements of resonators with nonuniform cross‐sectional areas that are easily altered to yield different resonance frequencies are described. These resonators are useful as educational demonstrations of symmetry breaking and of an effect of nonuniformity upon standing waves, and have been previously demonstrated and explained [B. Denardo, J. Acoust. Soc. Am. 95, 2935(A) (1994), and B. Denardo and S. Alkov, Am. J. Phys. 62, 315–321 (1994)]. Resonators that yield two, three, and four pitches are considered, where the relative frequencies are designed to correspond to musical intervals. Agreement is within 2% in all cases and 1% for most. The data reveal a breakdown of the theory, which is shown to be a result of additional kinetic energy, and thus effective inertia, near a discontinuity in cross‐sectional area. The data also reveal that an appropriate end correction for this case is not that for a thin‐walled tube but, rather, an infinite flange.

Whispering‐gallery modes of nonuniform dielectric resonators

AbstractNew results of theoretical and experimental investigations of nonuniform dielectric resonators (DRs) with higher‐order azimuthal waves (whispering‐gallery modes) are presented. The frequency splitting and modal coupling phenomena are studied. The effect of the space‐frequency field separation of the modes is found. Application of nonuniform dielectric resonators for the study of various materials (semiconductive and dielectric plates and films, high‐Tc superconductors), and for the design of millimeter‐wave filters and oscillators is proposed. © 1995 John Wiley & Sons, Inc.

Quasioptical dielectric resonators in millimeter-wave band experiments

New results of theoretical and experimental investigations of non-uniform dielectric resonators with the higher order azimuthal waves (whispering gallery modes) have been presented. Their application for study of various materials (dielectric, high-Tc superconductor) and for generation obtaining of millimeter wave oscillations has been considered.

Experimental properties of an unstable resonator with nonuniform magnification using aspheric mirrors

Laser resonators having nonuniform magnification can provide an advantage over constant magnification resonators in terms of energy extraction and far-field performance for low-gain lasers. This work explored the experimental characteristics of a resonator that was designed to have a lower magnification at the center of the resonator than at the edge. This was achieved using aspheric mirrors. Misalignment sensitivity, intracavity intensity, polarization, and collimation measurements were made. Results illustrate that some geometric properties were predictable and that aspheric mirrors can be used in resonator designs. In addition, the feasibility of using aspheric mirrors was evaluated. For certain applications, nonuniform magnification resonators using aspheric mirrors offer promising options.

Resonance splitting in nonuniform ring resonators

The frequency response of a microstrip ring resonator with small terminal couplings is discussed. For resonators consisting of nonuniform lines, there is shown to be resonance splitting in the transfer function.