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Lamb wave resonators (LWRs) based on lithium niobate on insulator (LNOI) substrates operating in an A1 mode at frequencies above 5 GHz typically exhibit high electromechanical coupling coefficients (K2) ranging from 20% to 30%. This makes them promising candidates to replace current bulk acoustic wave technology in next-generation broadband RF filters. However, the K2 of conventional LWRs still struggles to meet application requirements for bandwidths exceeding 1 GHz, such as WiFi-6E. This paper presents an analytical optimization approach for rapid and comprehensive scanning of the full 3D Euler space to find the maximum effective K2 of LWR devices. Such a full scan is difficult to achieve by the conventional time-consuming finite element method (FEM). The K2 results for a selected subset of Euler angles obtained through this analytical approach align with FEM simulation results. The optimized results show that LWRs on LNOI can achieve the highest K2 of 59.92% at Euler angles of (0, −151°, −60°), providing bandwidths exceeding 1 GHz at 5 GHz. To validate this optimization approach, LWRs with various orientations were fabricated on both 41° YX-cut and Z-cut LNOI wafers, with measured K2 values at different Euler angles agreeing well with both analytical and FEM results. The proposed K2 optimization method serves as a valuable guideline for selecting substrate cuts and device orientations in the design of ultra-broadband filters for next-generation telecommunications. [ABSTRACT FROM AUTHOR]

The emission properties of a single Si microdisk resonator with a deterministically embedded GeSi quantum dot (QD) stack have been investigated. The results demonstrate selective excitation of different modes of the resonator depending on the position of QDs. The photoluminescence (PL) spectrum changes dramatically depending on the location of the QDs in the resonator. For the central QD position, the excitation of low Q-factor Mie modes with high field concentration in the center of resonator results in the appearance of a broad PL band. When the stack of QDs is shifted from the center to the edge of the Si resonator, the quenching of this PL band is observed and narrow PL peaks corresponding to whispering gallery modes (WGMs) appear in the PL spectrum. It is found that resonator modes can be excited not only by QDs but also by the radiation of the wetting layer. It is shown that a GeSi island on the top of the QD stack, not covered by silicon, can play the role of a nanoantenna, redirecting radiation to the upper half-space, which is especially important for WGMs that usually radiate sideways. [ABSTRACT FROM AUTHOR]

We present a novel approach for actively controlling electromagnetically induced transparency (EIT) analogs in a single-mode microstrip cavity. This cavity is side-coupled with a pair of varactor-loaded split-ring resonators (SRRs). The EIT-like effect is achieved through resonance hybridization between the paired SRRs with frequency detuning. The microstrip cavity is utilized to enhance the EIT-like transmission properties, including Q-factor and group delay. Varactor diodes, soldered at the gap of the SRRs, are biased electrically through a DC voltage source. This dynamic modulation setup allows for the tuning of the enhanced EIT analog. Experimental results demonstrate that the enhanced EIT-like transmission spectrum can be tuned reversibly by 378 MHz with respect to the transmission dip frequency of 2.464 GHz under the bias voltage ranging from 0 to 5 V. Simultaneously, the controlled transmission spectrum enables a remarkable change in group delay of 10.9 ns. Moreover, the modulation amplitude of the composite SRRs-cavity structure reaches a peak value of up to 34.5 dB, significantly higher than the 6.4 dB of the individual SRRs pair. These results hold promise for inspiring innovation in actively controlled photonic devices for practical applications. [ABSTRACT FROM AUTHOR]

A plasma refractive index sensor based on metal–insulator–metal waveguide-coupled analogy T-shaped with double-ring resonators was designed. The transmission characteristics of the waveguide were investigated using the finite-difference time-domain method with perfectly matched layer absorbing boundary conditions. By optimizing the structure parameters, the sensor obtained the maximum sensitivity (S) of 1110 nm/RIU and the maximum figure of merit of 1904. The results demonstrate that this new structure can generate dual Fano resonances and exhibit typical refractive index sensing functionality, which provides valuable insights into the design and optimization of plasma refractive index sensors. Additionally, by measuring the concentration of plasma solution and glucose solution, it has been proven that the structure has the prospect of practical application. [ABSTRACT FROM AUTHOR]

The lithographically tunable and small size features of Lamb wave resonators (LWRs) take a bright future for their use in high frequency narrow band filters. Resonant frequency drift due to temperature variation has a large impact on the narrower passband and a temperature coefficient of frequency (TCF) closer to 0 can broaden the stable temperature range of the resonator. This paper proposes a method of etching grooves in the area of the piezoelectric layer not covered by the Interdigital transducer (IDT) electrodes to improve the temperature stability of the Lamb resonator. Through the finite element method and theoretical analysis, the phase velocity, group velocity, and TCF dispersion curve of different modes of the resonator with groove structure were determined. The reason for the change of TCF under different normalized thicknesses of AlN was explained through the conversion of the LWR from a contour mode resonator (CMR) to a Cross-Sectional Lamé Mode Resonator. Simulation and test have shown that etching grooves have the effect of reducing TCF by adjusting the electromechanical coupling coefficient. The test shows that 205 nm-depth grooves can lower the TCF of the S0 mode IDT-Open LWR from −13.3 to −5.1 ppm/°C and S1 mode from −36.8 to −9.0 ppm/°C, respectively. The TCF of S0 and S1 mode LWRs decreased by 61.7% and 75.5%, respectively, after 205 nm groove etching. The groove etching method greatly raises the temperature stability of the LWR, enabling Lamb wave filters to operate stably over a wider temperature range. [ABSTRACT FROM AUTHOR]

Resonators based on two-dimensional (2D) materials have exceptional properties for application as nanomechanical sensors, which allows them to operate at high frequencies with high sensitivity. However, their performance as nanomechanical sensors is currently limited by their low quality (Q)-factor. Here, we make use of micro-electromechanical systems (MEMS) to apply pure in-plane mechanical strain, enhancing both their resonance frequency and Q-factor. In contrast to earlier work, the 2D material resonators are fabricated on the MEMS actuators without any wet processing steps using a dry-transfer method. A platinum clamp, which is deposited by electron beam-induced deposition, is shown to be effective in fixing the 2D membrane to the MEMS and preventing slippage. By in-plane straining the membranes in a purely mechanical fashion, we increase the tensile energy, thereby diluting dissipation. This way, we show how dissipation dilution can increase the Q -factor of 2D material resonators by 91%. The presented MEMS actuated dissipation dilution method does not only pave the way toward higher Q -factors in resonators based on 2D materials, but also provides a route toward studies of the intrinsic loss mechanisms of 2D materials in the monolayer limit. [ABSTRACT FROM AUTHOR]

The absorption of a free-standing ultra-thin film supporting a single resonant mode is, in principle, limited to 50%. Based on the degenerate critical coupling (DCC) of dipole modes, silicon Mie resonators can overcome the absorption limit and achieve perfect absorption in the green light range. DCC requires that the radiative loss of each dipole mode matches material loss. Due to the material properties of silicon, the material loss varies with wavelength. Therefore, flexible tuning of radiative loss to match the wavelength-dependent material loss is crucial for realizing DCC-based perfect absorbers. In this study, we propose that a 45-degree rotation of cubic Mie resonators enhances the radiative loss of electric dipole mode. Hence, the DCC-based perfect absorption can be extended to the violet light range. In addition to applications in photodetectors and imaging sensor pixels, the proposed perfect absorber has great potential to become nonlinear elements based on the photothermal effect for photonic neuromorphic computing due to its temperature-dependent scattering. [ABSTRACT FROM AUTHOR]

We present experimental demonstration and modeling of mechanical wave propagation in a quasi-one-dimensional (quasi-1D) phononic crystal (PnC) waveguide (WG) constructed from a periodic array of single-crystal cubic-silicon carbide (3C-SiC) coupled micromechanical resonators, with an exceptional dynamic range exceeding 92 dB. The PnC design comprises 50 periodic cells, enabling the propagation of flexural mechanical waves in high-frequency and very-high-frequency bands, featuring a broad PnC bandgap spanning approximately 24–27.5 MHz. Furthermore, the 3C-SiC PnC WG exhibits excellent characteristics, including a high group velocity of 350 m/s and a low transmission loss of 0.69 dB/mm, enabling efficient guidance and support for mechanical waves across extended distances before reaching the noise level of the device. These attributes of the PnC WG, as demonstrated in this study, may open possibilities for the development of device platforms with applications in on-chip signal processing, sensing, and quantum transducer technologies. [ABSTRACT FROM AUTHOR]

Within the field of elastic metamaterials, topological metamaterials have recently received much attention due to their ability to host topologically robust edge states. Introducing local resonators to these metamaterials also opens the door for many applications such as energy harvesting and reconfigurable metamaterials. However, the interactions between phenomena from local resonance and modulation patterning are currently unknown. This work fills that gap by studying multiple cases of spatially modulated metamaterials with local resonators to reveal the mechanisms behind bandgap formation. Their dispersion relations are determined analytically for infinite chains and validated numerically using eigenvalue analysis. The inverse method is used to determine the imaginary wavenumber components from which each bandgap is characterized by its formation mechanism. The topological nature of the bandgaps is also explored through calculating the Chern number and integrated density of states. The band structures are obtained for various sources of modulation as well as multiple resonator parameters to illustrate how both local resonance and modulation patterning interact together to influence the band structure. Other unique features of these metamaterials are further demonstrated through the mode shapes obtained using the eigenvectors. The results reveal a complex band structure that is highly tunable, and the observations given here can be used to guide designers in choosing resonator parameters and patterning to fit a variety of applications. [ABSTRACT FROM AUTHOR]

The hemispherical shell resonator (HSR) is the core element of the hemispherical resonator gyroscope (HRG), and its frequency mismatch is a key property influencing gyroscope accuracy. Investigating the mechanism of frequency mismatch is vital for improving the quality of HSRs and performance of HRGs. Midsurface radius imperfections and thickness imperfections are two principal causes of frequency mismatch, but their combined effects have rarely been discussed. This paper develops a model to comprehensively analyze the frequency mismatch of HSRs with both radius and thickness imperfections. The model derives a quantitative relation between the frequency mismatch and the two imperfections, and provides principles for evaluating dominant imperfections. To validate the model, we conduct experiments on a batch of 12 HSRs with random geometric imperfections. We apply the model in calculating the theoretical frequency mismatches of these HSRs, and the results agree well with the experimental data. The experiment also confirms that for macro-HSRs, thickness imperfections have a larger impact than radius imperfections, and the frequency mismatch is approximately linear to the fourth thickness harmonic. Our research can be a useful reference for the design and fabrication of HSRs and may open new possibilities for high-precision manufacture of HRGs. [ABSTRACT FROM AUTHOR]

In a class of high quality (Q-) factor dielectric resonators with low radiative losses, including popular whispering-gallery mode (WGM) resonators with high azimuthal mode numbers, due to high confinement of modal field in dielectric, the Q-factor is limited by the value of inverse dielectric loss tangent of dielectric material. Metal enclosures necessary for device integration only marginally affect the Q-factor while eliminating the residual radiative loss and allowing the optimization of input and output coupling. While very high Q-factors ∼ 200 000 are available in sapphire WGM resonators in X-band, at millimeter wave frequencies increasing dielectric loss limits the Q-factor to much smaller values, e.g. ∼50000 and ∼25000 for quasi-TE and quasi-TM modes, correspondingly, at 36 GHz. The use of distributed Bragg reflection (DBR) principle allows to push modal energy outside dielectric while also isolating it from Joule losses in metallic enclosure walls. Very high Q ∼ 600 000 > --> t g δ has been demonstrated in X-band [C. A. Flory and R. C. Taber, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 44, 486–495 (1997).] at the expense of impractically large dimensions. In this work, we report on the assembly and testing of a compact Ka-band sapphire distributed Bragg reflector cavity characterized with Q-factor seven times larger than one predicted by the material's dielectric loss at the frequency of interest. An intrinsic Q-factor of ∼ 200 000 is demonstrated at 36 GHz for the lowest order TM-mode of a sapphire DBR. The resonator has 50 cm 3 volume, smaller than previously demonstrated DBRs. [ABSTRACT FROM AUTHOR]

A novel mode-localized acceleration sensor employing an electrostatically coupled resonator and integrating a lever with proof mass is micromachined using standard silicon on insulator (SOI) technology. In order to determine the linear dynamic range of the sensor, a reduced order model is developed while assuming that the resonators vibrate below the critical amplitude. Then, open-loop and closed-loop testing platforms are established to measure the performance of the linearly operating accelerometer in a vacuum environment (less than 5 Pa). Moreover, the corresponding amplifier circuit based on the capacitive detection principle is designed in order to extract and amplify the current signal from the resonators. The obtained results show that the accelerometer sensitivity can be increased by three orders of magnitude when using the relative shift of amplitude ratio as the output metric instead of the relative shift of frequency, and the experimental measurements are consistent with the theoretical predictions. Remarkably, the Allan standard deviation of the mode-localized acceleration sensor obtained from the closed-loop testing circuit is around 5.03 μg. [ABSTRACT FROM AUTHOR]

Hybrid spin-mechanical systems offer a promising platform for advancing quantum science and technology. However, practical implementation of applications within these hybrid quantum systems demands the seamless integration of supplementary physical components. In this context, we present a proposal for a multi-mode spin-mechanical setup, featuring the utilization of three-mode coupling nanomechanical carbon nanotube (CNT) resonators. These resonators interact with each other via a phase-dependent phonon-exchange mechanism, which is coupled to the same nitrogen vacancy (NV) centers in diamond. Based on the modulation of the phonon–phonon coupling phase and leveraging the triple Fano-like resonance phenomenon, a tripling of electromagnetically induced transparency (EIT) becomes achievable within the system. This tripling is accompanied by swift dispersion, leading to a subtle advancement or delay in outcomes. The phenomenon of triple Fano-like resonance, alongside the resulting triple EIT, engenders noteworthy slow-to-fast and fast-to-slow light effects, which is theoretically demonstrated in CNT resonators, with both identical and distinct frequencies. The findings underscore that CNT resonators with varying frequencies can evoke a more pronounced transition in the slow–fast–slow and fast–slow–fast light effects. This study lays the foundation for the application of phonon-mediated optical information storage and processing. [ABSTRACT FROM AUTHOR]

We deduce equations to calculate coupling coefficients of diamond micro-ring resonators. The equations can be used universally at any wavelength but not limited to the transmission peaks/valleys, and can be adapted with triangular cross-sections and tapered waveguides. Consequently, we build three models in accordance to different diamond processing technologies. These models deal with ring resonators with either rectangular cross sections, or triangular cross sections, or with tapered bus for triangular cross sections. The calculated coupling coefficients can be well fitted by exponential decay functions of gap d. Due to geometrical limitations, triangular-cross-sectional diamond resonators are shown to have much smaller (factor 20) coupling coefficients than those of rectangular-cross-sectional resonators. A tapered bus is shown to be beneficial to increase the coupling coefficient. Besides the calculation of coupling coefficients, the method presented in the paper can also be used to calculate the bending loss of micro-ring resonators, as a complement to the existing methods. [ABSTRACT FROM AUTHOR]

The recently proposed concept of electric chiral magnonic resonator (ECMR) has been extended to include usage of spin–orbit torques (SOT). Unlike the original version of ECMR which was based on voltage controlled magnetic anisotropy (VCMA), the spin wave amplification power by this new version of ECMR (pumped by SOT) no longer depends on the phase of the incident wave, which is highly desirable from an application point of view. The performance of the SOT pumped ECMR has been compared with the case of amplification by applying SOT pumping directly to a waveguide (without any ECMR involved). It is argued that at the expense of narrowing the bandwidth (i.e., slower amplifier response), the advantage of the former configuration (amplification by a SOT pumped ECMR) over the latter (amplification by direct SOT pumping the waveguide) is to offer gain, while at the same time, maintaining system stability (avoidance of auto-oscillations). Non-linear behavior of the SOT pumped ECMR has been analyzed. It is demonstrated that by cascading a SOT ECMR operating in an off-resonance mode together with a VCMA biased passive ECMR, it is possible to produce a magnonic neuron with a transmitted signal magnitude larger than the input in the firing state. [ABSTRACT FROM AUTHOR]

Metasurface analogs of electromagnetically induced transparency (EIT) are attracting sustaining attention due to their ability to maintain transparency windows accompanied by extreme dispersion of propagating waves, which are important for slow light devices and highly sensitive optical sensors. In this paper, we study theoretically, numerically, and experimentally the conditions for the existence of multi-band transparency windows in the metasurface supported by the interaction of dipole modes in an asymmetric unit cell. The unit cell is composed of a single bright resonator and several dark resonators made in the form of rectangular metal patches. The manifestation of EIT is studied for different metasurface configurations by varying the number and positions of resonators used within the unit cell. To validate the slow-down effect caused by EIT, a prototype of the metasurface is fabricated and tested, providing a measurement of the group delay and bandwidth-delay product features. The obtained results clearly confirm the presence of four EIT-like transparency windows in the metasurface transmission spectra originating from the coupling between either quasi-TE or quasi-TM modes of the resonators. [ABSTRACT FROM AUTHOR]

We derive a coupled-mode theory (CMT) formulation for the fast analysis of periodic multi-element metasurfaces in the presence of radiation losses. Full-wave simulations of periodic multi-element metasurfaces are very time- and memory-consuming, especially as the size and complexity of the metasurface increase. The CMT formulation provides a considerably faster and efficient alternative. It results in a small system of equations with size equal to the number of supported resonator modes in the frequency range of interest, allowing to calculate the resonator mode amplitudes and, consequently, the metasurface response. Subsequently, we systematically derive analytical closed-form expressions for the coupling coefficients between two weakly coupled resonators in the presence of radiation losses and incorporate them into the CMT model, which is found important for the accurate description of the metasurface, while also providing insight into the underlying physics of complex metasurfaces. We validate the proposed formulation on benchmark examples of both metal- and dielectric-based metasurface absorbers (MSAs) by comparing the CMT results to spectral FEM simulations of the composing supercell. To further demonstrate the potential of the proposed formulation, as a proof of concept, we use the CMT to synthesize a larger optimized periodic multi-element MSA. A comprehensive comparison to full-wave FEM simulations of the composing supercell is included in terms of time and computational requirements, which shows that our method provides a valuable and efficient alternative solver for synthesizing complex metasurfaces. [ABSTRACT FROM AUTHOR]

All real systems are essentially non-conservative in nature, which is non-Hermitian in the fundamental premises of the quantum realm. Such open systems obeying parity-time (PT) symmetry can offer intriguing physics, which has sparked much attention in recent years. The thoughtful interplay of loss and gain in PT-symmetric systems can tune the eigenstates from real to complex space passing through a singular point known as an exceptional point (EP) with concurrently coalescing the discrete eigenstates. In this regard, artificially engineered near-field coupled metasurfaces provide a remarkable podium to introduce as well as control loss and coupling strength simultaneously, manifesting a practical channel to attain EP. Motivated by this notion, we have theoretically explored near-field coupled dark-bright-mode assisted terahertz metasurfaces imitating a typical non-Hermitian PT-symmetric system. Structurally, such metasurfaces are realized by utilizing a pair of orthogonally twisted near-field coupled split-ring resonators (bright-dark-resonators). We have meticulously examined such a system with two distinctive approaches, i.e., the loss parameter and inter-resonator coupling strength. Eventually, our exploration demonstrates that judicious modulation of the loss parameter can invoke an undemanding route to approach the other wisely elusive exceptional point. We believe that this comprehensive study of non-Hermitian quantum systems in a photonic context can lead to the development of accurate and precise ultra-sensitive sensors besides other futuristic photonic devices. [ABSTRACT FROM AUTHOR]

We study both numerically and experimentally an acoustic metasurface based on coupled Helmholtz resonators to obtain broadband low-frequency spectral responses for acoustic insulation. A hierarchical approach is proposed, starting from single and coupled Helmholtz resonators, up to a periodic array of resonators. To this end, we performed numerical simulations using the finite element method, in which the resonators are modeled as drilled rigid spheres in airborne environment and experimental demonstrations based on ping-pong balls as Helmholtz resonators in an acoustic reverberation box. We showed the alteration of the low-frequency response of acoustic insulation resulting from inter-unit coupling in acoustic metasurfaces, and the apparition of additional attenuation by inserting a plexiglass board as support for the structure. [ABSTRACT FROM AUTHOR]

In the paper, a metasurface is investigated, the unit cell of which consists of two resonators. We show that the breaking of the axial symmetry of the unit cell in such a structure leads to the appearance of two Fano resonances instead of one that is characteristic of the symmetric unit cell. The two resonances are different, one of which is symmetric and the other is asymmetric. This is confirmed by calculating the phases of currents in the adjacent resonators. Modeling results are confirmed by experimental investigation of the metasurface spectrum in a microwave frequency range showing two resonances measured experimentally. A detailed study of the currents flowing in the adjacent resonators of the unit cell demonstrates that currents at the Fano resonance dips flow either in phase or in antiphase with respect to the external electric field, whereas in peaks this difference is π /2. This confirms the interference nature of the Fano effect. [ABSTRACT FROM AUTHOR]

This paper proposes an elastic topological resonator derived from the Kekulé tight-binding model, which enables the quantum spin Hall effect (QSHE). Band inversion in the spin system is realized through fine-tuning the intracellular coupling constants. With full-wave simulations, the topological interface configurations demonstrate the robust spin-locked edge state transport characteristic, featuring excellent fidelity via defects and anti-direct transmission. Then, a hexagonal resonator is located beside the straight waveguide to achieve multiple effective coupling directed by the edge state. The effect of the distance between the straight waveguide and the hexagonal part is further analyzed on the number of the resonant mode. Based on the functionally graded design concept, the topological resonance rainbow is also proposed to spatially separate distinct frequency components in accordance with projected band branches, to realize the progressive propagation of Lamb waves along the resonator route. Our work provides a novel mechanism for manipulating elastic waves with topological edge states, which is anticipated to serve as a foundation for creating programmable sensors and multifunctional testing equipment. [ABSTRACT FROM AUTHOR]

This paper investigates a highly selective frequency selective rasorber (FSR) utilizing interdigitated resonators, characterized by a passband exhibiting low insertion loss (IL) and the introduction of a second-order passband response in the lossless layer enhances selectivity on both sides of the passband. The lossy unit is implemented by inserting interdigitated resonators on an octagonal ring loaded with lumped resistors, while the lossless layer is constructed with a five-layer structure. Simulation results demonstrate a low IL value of 0.78 dB at 3.5 GHz. At vertical incidence, the S 21>−3 dB bandwidth ranges from 3.41 to 3.67 GHz, and the S 11<−10 dB range spans from 2.2 to 8.2 GHz, obtaining two absorption bands on either side of the passband, with absorption rates exceeding 80%. The operating frequency bands are 1.95–3.27 GHz and 3.8–8.4 GHz. The designed FSR exhibits polarization insensitive. To validate simulation results, a prototype FSR was fabricated and tested, with experimental data aligning with simulation results. [ABSTRACT FROM AUTHOR]

This research proposition introduces a novel microstrip antenna design that features triple notches for ultra-wideband (UWB) applications. The antenna, measuring 35.4 mm × 28.82 mm × 1.57 mm, incorporates rectangular and semi-circular slots, as well as a pentagonal stub. A modified U-shaped slot on the pentagonal stub creates one notched frequency band at 3.3–3.7 GHz. Additionally, two Split Ring Resonators (SRRs) are integrated into the antenna's rear surface, resulting in two more notched bands at 5.1–5.8 GHz and 7.1–7.8 GHz. Operating within a frequency range from 3 to 11.2 GHz with VSWR ≤ 2, the antenna effectively excludes the triple stop bands at 3.3–3.7 GHz (11.4%), 5.1–5.8 GHz (12.8%) and 7.1–7.8 GHz (9.4%). The proposed antenna has been successfully prototyped and verified. An extensive result analysis has been conducted, confirming that the developed antenna is suitable for application in a range of wireless systems. Moreover, the article includes the implementation of an equivalent circuit for the proposed antenna. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a design of a substrate‐integrated waveguide (SIW) triplexer with improved low‐loss performance, passband ratio, and compactness based on the complementary split ring resonator (CSRR) structure is presented. The proposed triplexer operates at three passbands of 6, 8, and 10 GHz that correspond to the passband ratios of 1.33 and 1.67. By appropriately designing square CSRRs on the surface of the SIW structure, the low‐loss and compact resonator filters below the cut‐off frequency of the SIW at each operation frequency can be realized. The wide passband ratio is obtainable by adjusting the dimensions of the T‐junction. The measured results show the minimum insertion losses of 1.5, 1.4, and 1.9 dB at 6, 8, and 10 GHz, respectively. In addition, the minimum measured return losses are −9.33, −11.3, and −12.4 dB at the corresponding three passbands. The measured isolation between output ports is better than −17 dB in the frequency range from 5 to 11 GHz. The measured results agree well with simulations which are conducted by the CST Microwave Studio simulator. The proposed triplexer is designed on a cost‐effective RO4003C substrate with a compact size of 35 × 25 mm2 [ABSTRACT FROM AUTHOR]

In this paper, a Wilkinson power divider based on a new harmonic suppressor structure is proposed with suppressed harmonics and improved operating band parameters. The proposed suppressor structure consists of three resonators. The first resonator is an elliptic rectangular shaped resonator with a short base line and two slots. These slots decrease the resonant frequency location, without changing the dimensions of the resonator. This mode has been fully analysed by investigating the effect of surface current density. The second resonator is an elliptic resonator with a long base length to suppress the second harmonic. The third resonator is a rectangular suppressor to suppress higher order harmonics. The proposed power divider is fabricated and measured. The operating frequency of this power divider is 1.26 GHz, the return loss is 31.5 dB and the insertion loss is 3.1 dB. The operating bandwidth is from 0.99 to 1.4 GHz with a return loss better than 15 dB which shows the fractional bandwidth of FBW = 34%. The second to sixth harmonics have suppression level better than 50 dB, and for higher harmonics up to the 14th harmonic, they have suppression level better than 25 dB. [ABSTRACT FROM AUTHOR]

A low-profile, compact and efficient antenna is especially desirable for wireless applications, as it can reduce the size and weight of the system and improve its performance. In recent years, flower-shaped antennas have gained popularity due to their low profile, broad bandwidth and good radiation characteristics. In this work, a high-isolated dual-element UWB-MIMO antenna is experimentally verified having size of 32 × 39 × 0.8 mm3. The main radiating element of MIMO setup comprises a Half-Cut Flower-Shaped (HCFS) resonator. A tree-shaped decoupling structure is use to enhance the isolation. The simulated operating band of the proposed 2-port UWB-MIMO antenna ranges from 2.3 to 2.68 GHz and 3.15 to 12.87 GHz which covers Bluetooth, Wi-Fi/WLAN, Wi-MAX and UWB) with inter-element isolation of more than 15 dB and 20 dB, respectively. The measured results are found in close agreement with simulated ones. Furthermore, the diversity parameters such as Envelope Correlation Coefficient (ECC), Channel Capacity Loss (CCL), Mean Effective Gain (MEG), Effective Diversity Gain (EDG) and Total Active Reflection Coefficient (TARC) have also been analysed to ensure its legitimacy for wireless applications. Moreover, the simulation S-parameters characteristic of the proposed 8-element antenna for wireless access point applications has also been showcased. [ABSTRACT FROM AUTHOR]

In this research, the effects of two different types of in-track countermeasures on ground-borne vibration from underground railways are investigated. First, the influence of new type of supports is investigated, in which the rotation of the rail is partially or fully restrained. Second, a different simple local resonator is considered consisting of masses on springs placed at fixed spacing between the supports. To investigate the effects of these countermeasures, a numerical model is developed consisting of two sub-models: the first sub-model is an excitation model in which the track is modelled as an infinite beam on discrete supports connected to rigid foundation, for the calculations of forces transmitted to tunnel bed. The beam is analysed under the action of a number of axle masses with harmonic excitation induced through relative displacement between the un-sprung axle mass and the beam using a pull-through roughness. This first sub-model employs the dynamic stiffness method to perform the calculation. The second sub-model accounts for a tunnel embedded in a half space and is used to calculate the responses in the free surface with the input forces taken from the first sub-model after transformation to the wavenumber domain. The second sub-model is based on the well-known Pipe in Pipe (PiP) model. The discontinuously-supported model used in this work is verified using a continuously supported model. The effects of the suggested countermeasures on vibration mitigation are explored via parametric analysis that shows the impact of the added rotational stiffness, resonators' natural frequency and the resonators' mass. The results show for the parameters considered that using the rotation restrained support can effectively reduce the ground-borne vibration levels by up to 20 dB for low frequencies. Furthermore, the use of local resonators can reduce the ground-borne vibration by 4–10 dB for frequencies in the range 20–200 Hz. [ABSTRACT FROM AUTHOR]

We aim to assess a straightforward technique to enhance spectral quality in the brain, particularly in the cerebellum, during 7 T MRI scans. This is achieved through a wireless RF array insert designed to mitigate signal dropouts caused by the limited transmit field efficiency in the inferior part of the brain. We recently developed a wireless RF array to improve MRI and 1H‐MRS at 7 T by augmenting signal via inductive coupling between the wireless RF array and the MRI coil. In vivo experiments on a Siemens 7 T whole‐body human scanner with a Nova 1Tx/32Rx head coil quantified the impact of the dorsal cervical array in improving signal in the posterior fossa, including the cerebellum, where the transmit efficiency of the coil is inherently low. The 1H‐MRS experimental protocol consisted of paired acquisition of data sets, both with and without the RF array, using the semi‐LASER and SASSI sequences. The overall results indicate that the localized 1H‐MRS is improved significantly in the presence of the array. Comparison of in vivo 1H‐MRS plots in the presence versus absence of the array demonstrated an average SNR enhancement of a factor of 2.2. LCModel analysis reported reduced Cramér–Rao lower bounds, indicating more confident fits. This wireless RF array can significantly increase detection sensitivity. It may reduce the RF transmission power and data acquisition time for 1H‐MRS and MRI applications, specifically at 7 T, where 1H‐MRS requires a high‐power RF pulse. The array could provide a cost‐effective and efficient solution to improve detection sensitivity for human 1H‐MRS and MRI in the regions with lower transmit efficiency. [ABSTRACT FROM AUTHOR]

This research work investigates the performance of a novel low profile 20-bit frequency coded L-shape slot loaded resonator for chipless RFID applications. The proposed chipless RFID comprises a CPW-fed UWB radiator and an L-shaped multi-slot resonator to achieve 20-bit data capacity. CPW technique is implemented to enhance antenna bandwidth and radiation characteristics. The designed UWB radiator covers the entire band from 3 to 12 GHz with better return loss. Also, the peak gain is measured as 6 dBi in the respective frequency spectrum. The proposed L-shaped frequency-coded multi-slot resonator is developed with a compact size of 23.6 × 14.1 × 1.6 mm³. Moreover, the frequency coding technique allows for a wide range of frequency combinations for data representation, as well as contributes to reducing the RFID tag size. The research holds significance in propelling RFID technology forward and ushering in a new era of small, efficient, and flexible data encoding solutions. [ABSTRACT FROM AUTHOR]

This paper describes the general properties of power dividers, in particular matching and isolation. This original works relates to three different divider structures based on the circular-shaped resonator. These prototypes resemble the Wilkinson power divider due to their geometric configuration. These power dividers provide very good isolation between their output ports of −51.26 dB. In fact, the originality of these new structures stems from the idea of minimizing the size of this classic power divider. The required design parameters for the three proposed dividers came from a simulation study using the Ansoft HFSS tool in addition to a design theory. The experimental prototypes are well presented and operate at 2.4 GHz. They demonstrate excellent performance in adaptation, which refers to impedance matching, ensuring consistent impedance at the component terminations. Additionally, they exhibit low insertion losses and high isolation at 2.4 GHz. The measurement results agree well with those of the simulation. The benefits demonstrated by this study are significant, justifying the preference for these components. [ABSTRACT FROM AUTHOR]

The design of balanced filters based on composite right/left hand (CRLH) structure is well developed. Among those, few designs exist which although they provide some good responses, suffer from narrow stopbands and interdependent passbands. This paper proposes a new technique for improving the characteristics of dual-band balanced bandpass filters (B-BPFs) based on planar CRLH. Using unequal inductive stubs (UISs) attached to the interdigital capacitor (IDC) unit cell, we were able to achieve outstanding harmonic suppression and passband controllability. This structure offers higher degrees of freedom compared to conventional designs and provides better control over the filter specifications. Mathematical modeling, analysis, simulation, fabrication, and performance measurement of the proposed technique in a dual-band B-BPF are also provided. Our work resulted in an independent and controllable dual-band B-BPF with ultra-wide upper differential-mode (DM) stopband of 5.9f1 and common-mode (CM) suppression of 40.4 and 32.6 dB for the first and second bands, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a mode control technology of a slotline resonator is proposed and utilized to guide the design of the slotline resonator. With this method, characteristic modes generated by the slotline resonator are more controllable. With characteristic mode analysis, which is the core of this technology, the desired and unwanted modes of the slotline resonator are easy to be analyzed, controlled, and further used to expand the stopband bandwidth. By applying this technology, a multi-mode slotline resonator with a T-shaped coupling structure (MMSR-T) is proposed by modifying a multi-mode slotline resonator (MMSR), and its unwanted modes out of the passband are more controllable without influencing the expected modes in the passband. Based on the proposed MMSR-T, a balanced bandpass filter (BPF) is proposed, which consists of a U-shaped microstrip/slotline transition as the input/output structure, a T-shaped slotline feeding structure as a feeding terminal, and MMSR-T as the filtering unit. Through the mode analysis and design of MMSR-T, ultra-wide differential-mode (DM) stopband, high common-mode (CM) suppression, and high DM selectivity are obtained in this design. The measured results agree well with the theoretical predictions and simulated results. The effects of mode control technology on stopband extension are proven. [ABSTRACT FROM AUTHOR]

In order to achieve miniaturization and high performance in microwave filters, this paper proposes two double-layer bandpass filters with different structures, both equivalent to square-coupled topologies. These filters employ dual-cavity single-mode and single-cavity dual-mode substrate-integrated waveguide resonators. In this configuration, the upper layer comprises two single-mode resonators connected to the input and output feed lines, while the lower layer contains dual-mode resonators coupled to the upper layer’s single-mode resonators through two slots on the middle metal layer. A comprehensive analysis is conducted on the impact of primary parameters on filter characteristics and transmission zero positions. The second filter is fabricated and tested, yielding results consistent with simulation outcomes. The center frequency of the filter is 4.77 GHz, with a 3 dB bandwidth of 0.16 GHz (relative bandwidth: 3.35%). Additionally, its rectangularity coefficient at 10 dB approximately equals one, an ideal value for practical applications. [ABSTRACT FROM AUTHOR]

We present a comprehensive experimental study of the dynamics of electrostatic MEMS resonators under large excitations. We identified three frequency ranges where large oscillations occur; a non-resonant region driven by fast–slow dynamic interactions and two resonant regions. In these regions, we found a plethora of dynamic phenomena including cascades of period-doubling bifurcations, a bubble structure, homoclinic and cyclic-fold bifurcations, hysteresis, intermittencies, quasiperiodicity, chaotic attractors, odd-periodic windows within those attractors, Shilnikov orbits, and Shilnikov chaos. We encountered these complex nonlinear dynamics phenomena under relatively high dissipation levels, the quality factors of the resonators examined in this study were Q = 6.2 and 2.1. In the case of MEMS with higher quality factors (Q > 100) , it is quite reasonable to expect those phenomena to appear under relatively low excitation levels (compared to the static pull-in voltage). This calls for a new paradigm in the design of electrostatic MEMS that seeks to manage dynamic phenomena rather than attempt to avoid them and, thereby, overly restricting the design space. We believe this is feasible given the repeatable and predictable nature of those phenomena. [ABSTRACT FROM AUTHOR]

Summary: A low profile, concave conformal ring cylindrical dielectric resonator antenna (CDRA) employing frequency selective surface (FSS) using split ring resonator (SRR) for wideband and high gain applications is presented. The ring CDRA loaded with the monopole is designed to excite the TM01δ mode to increase the antenna's bandwidth. The effect of a curved ground plane (GP) on the radiation performance of CDRA is studied. A 5 × 5 array of the SRR is placed above the conformal GP at a far‐field distance optimized to (2n ± 1) λ/4 from the radiating element to enhance the gain of the proposed structure. The planar CDRA with FSS is compared with the conformal CDRA with FSS and a 4.3 GHz improvement in bandwidth is observed due to the multiple reflection and surface reflection leading to a 3.2 dBi improvement in gain. An impedance bandwidth of 51.8% (5 to 8.5 GHz) with a maximum gain of 8.7 dBi at 7.3 GHz resonant frequency and 99% radiation efficiency at 5.9 GHz is offered by the proposed antenna with FSS. Additionally, the proposed CDRA has a low profile of 0.12 λ0 where λ0 is the lower cut‐off frequency's wavelength. A good agreement is observed between the simulated and measured results. [ABSTRACT FROM AUTHOR]

Ring resonators are crucial in silicon photonics for various applications, but conventional designs face performance trade‐offs. Here a third‐order polynomial interconnected circular (TOPIC) bend is proposed to revolutionize the ring designs fundamentally. The TOPIC bend has a unique feature of continuous curvature and curvature derivative, which is theoretically derived to be essential for waveguide loss optimization. With the TOPIC bend, the silicon ring resonators demonstrated here have achieved three records to the best of our knowledge: the smallest radius (0.7 μm$\mathrm{\mu m}$) for silicon rings resonating with single guided mode, the lowest thermal tuning power (5.85 mW/π${\pi}$) for silicon rings with FSR≥${\rm FSR}\ge$3.2 THz, and the first silicon ring‐based WDM 32×$\mathrm{\times }$100 GHz filter. The filter has doubled the channel amount compared to the state of the art, and meanwhile achieved low insertion loss (1.91 ±$\pm$ 0.28 dB) and low tuning power (283 GHz mW−1${\rm mW}^{-1}$). Moreover, the TOPIC bend is not limited to ring applications, it can also be used to create bends with an arbitrary angle, with the advantages of ultra‐compact radius and heater integration, which are expected to replace all circular bends in integrated photonics, greatly reducing system size and power consumption. [ABSTRACT FROM AUTHOR]

Suspending devices on thin SiN membranes can limit their interaction with the bulk substrate and reduce parasitic capacitance to ground. While suspending devices on membranes are used in many fields including radiation detection using superconducting circuits, there has been less investigation into maximum membrane aspect ratios and achievable suspended device quality, metrics important to establish the applicable scope of the technique. Here, we investigate these metrics by fabricating superconducting coplanar waveguide resonators entirely atop thin (∼ 110 nm) SiN membranes, where the membrane's shortest length to thickness yields an aspect ratio of approximately 7.4 × 10 3 . We compare these membrane resonators to on-substrate resonators on the same chip, finding similar internal quality factors ∼ 10 5 at single photon levels. Furthermore, we confirm that these membranes do not adversely affect resonator thermalization and conduct further materials characterization. By achieving high quality superconducting circuit devices fully suspended on thin SiN membranes, our results help expand the technique's scope to potential uses including incorporating higher aspect ratio membranes for device suspension and creating larger footprint, high impedance, and high quality devices. [ABSTRACT FROM AUTHOR]

High‐index dielectrics or Super‐Mossian materials are essential for emerging nanophotonic applications. Several transition metal dichalcogenides (TMDCs) are promising as super‐Mossian dielectric materials. Molybdenum disulfide (MoS2) is an outstanding super‐Mossian TMDC exceeding Moss' rule prediction of its refractive index by nearly 40%. This high refractive index enables compact, multi‐functional, and high‐performance metadevices. Here, a MoS2 metasurface is experimentally demonstrated using resonators with volumes of nearly a tenth of those made of silicon. To harness their phase control ability, a MoS2 blazed metasurface is designed, fabricated, and demonstrated. The performance of the device is benchmarked by rigorous‐coupled‐wave‐analysis calculation. The results suggest that MoS2 holds great promise as a dielectric material platform for emerging nanophotonic technologies. [ABSTRACT FROM AUTHOR]

ABSTRACT The rapid expansion of Internet of Things (IoT) applications presents unprecedented challenges for antenna design, demanding solutions that are versatile, efficient, and capable of operating across multiple frequency bands. This paper addresses these challenges through the development of a design of a multiband antenna using Auxiliary Classifier Wasserstein Generative Adversarial Network for IoT applications (DMA‐ACWGAN‐IoT). Here, the Auxiliary Classifier Wasserstein Generative Adversarial Network (ACWGAN) is employed to generate synthetic data representing electromagnetic field distributions and antenna characteristics across various frequencies. The proposed metamaterial‐based Multiple‐Input Multiple‐Output (MIMO) antenna contains four discrete elements, each provided by a micro strip feed. The structures overall width and length are 60 and 52 mm. The metamaterial is printed on a patch and dispersed from the fields with the most effective coupling. The proposed structures strong impedance bandwidth works at 8.3 GHz, 10.8 GHz, 12.3 GHz, 13.7 GHz, 16.1 GHz, and 18.1 GHz, fabricating the proposed antenna prototype using a substrate made of FR‐4 material. The proposed DMA‐ACWGAN‐IoT design provides 6.5 dB maximum gain and 25.40%, 21.60%, and 20.05% higher efficiency compared to existing dual band antenna design with resonance frequency prediction under machine learning models (DBA‐PRF‐ML), machine learning verification depending on a distinctive SWB multiple slotted four‐port high isolated MIMO antenna loaded with metasurface for the applications of IoT (SWB‐MIMO‐IOT‐ML), and dual‐band miniaturized composite right–left‐handed transmission line ZOR antenna along machine learning method for microwave communication (DB‐ZORA‐MC‐ML). [ABSTRACT FROM AUTHOR]

Benefitting from the mature, cost‐effective, and scalable manufacturing capabilities of complementary metal‐oxide‐semiconductor (CMOS) technology, silicon photonics has facilitated the seamless and monolithic integration of diverse functionalities, including optical sources, modulators, and photodetectors. Microresonators can generate multiple coherent optical frequency comb lines and serve as optical sources. However, at the telecom band, silicon suffers from two‐photon absorption and free‐carrier absorption, which severely hampers the realization of microcombs from a single silicon chip at telecom wavelengths until now. In this paper, a novel approach is presented and demonstrated with near‐infrared dual‐band frequency combs from a multimode silicon resonator. With a single pumping configuration, dual‐band combs are generated from the interaction between the pump and Raman Stokes fields by involving two different optical mode families but with similar group velocities. It is observed that the pump power required to generate dual‐band combs is as low as 0.7 mW. The work in bringing telecom microcombs to the silicon platform will advance silicon photonics for the next generation of monolithically integrated technology based on a single silicon chip, enabling new possibilities for further exploring silicon photonics‐based applications in optical telecommunications, sensing, and quantum metrology in the telecom band using a monolithic single silicon chip. [ABSTRACT FROM AUTHOR]

Generating coherent optical frequency combs in micro-ring resonators with Kerr nonlinearity has remarkably advanced the fundamental understanding and applications of temporal dissipative solitons. However, the spectrum of such soliton combs is restricted to the conventional definition of combs as phase-locked, equidistant lines in frequency. Here, we introduce a new class of floquet topological soliton combs that emerge in two-dimensional arrays of strongly coupled resonators engineered using floquet topology. Specifically, we demonstrate incommensurate combs where the comb lines are not equidistant but remain phase-locked. These incommensurate combs are generated by self-organized, phase-locked floquet topological soliton molecules that circulate the edge of the array. We show that these floquet topological solitons are robust and they navigate around defects, allowing for agile tunability of the comb line spacing. Our results introduce a new paradigm in using floquet engineering to generate unconventional frequency combs beyond those achievable with single or weakly coupled resonators. Optical frequency combs are conventionally defined as a set of phase-locked, equally spaced spectral lines. Here, using a two-dimensional array of Floquet topological ring resonators, the authors propose novel incommensurate combs with phase-locked spectral lines that are not all equally spaced. [ABSTRACT FROM AUTHOR]

In a nanomechanical resonator coupled to a quantum point contact, the back action of the electronic state on mechanical motion is studied. The quantum point contact conductance changing with subband index and the eigenfrequency of the resonator are found to correlate. A model is constructed explaining the frequency deviations by the variable ability of the quantum point contact to screen the piezoelectric charge induced by mechanical oscillations. The observed effects can be used to develop electromechanical methods for studying the density of states in quasi-one-dimensional systems. [ABSTRACT FROM AUTHOR]

A promising route towards the deterministic creation and annihilation of single-phonons is to couple a single-photon emitter to a mechanical resonator. The challenge lies in reaching the resolved-sideband regime with a large coupling rate and a high mechanical quality factor. We achieve this by coupling self-assembled InAs quantum dots to a small mode-volume phononic-crystal resonator with mechanical frequency Ωm/2π = 1.466 GHz and quality factor Qm = 2.1 × 103. Thanks to the high coupling rate of gep/2π = 2.9 MHz, and by exploiting a matching condition between the effective Rabi and mechanical frequencies, we observe the interaction between the two systems via correlations in the emitted photons. Our results represent a major step towards quantum control of the mechanical resonator via a single-photon emitter. Coupling a single-photon emitter to a mechanical resonator enables the generation of single phonons. Here, the authors study the interaction of a single-photon emitter and a phononic-crystal resonator in the sideband-resolved regime. [ABSTRACT FROM AUTHOR]

MEMS gyroscopes are well known for their outstanding advantages in Cost Size Weight and Power (CSWaP), which have inspired great research attention in recent years. A higher signal-to-noise ratio (SNR) for MEMS gyroscopes operating at larger vibrating amplitudes provides improved measuring resolution and ARW performance. However, the increment of amplitude causes strong nonlinear effects of MEMS gyroscopes due to their micron size, which has negative influences on the performance. This paper carries out detailed research on a general nonlinear mechanism on the sensors using parallel-plate capacitive transducers, which is called the gain nonlinearity in electrostatic actuation. The theoretical model established in this paper demonstrates the actuation gain nonlinearity causes the control-force coupling and brings extra angle-dependent bias with the 4th component for the whole-angle gyroscopes, which are verified by the experiments carried out on a micro-shell resonator gyroscope (MSRG). Furthermore, a real-time correction method is proposed to restore a linear response of the electrostatic actuation, which is realized by the gain modification with an online parameter estimation based on the harmonic-component relationship of capacitive detection. This real-time correction method could reduce the 4th component of the angle-dependent bias by over 95% from 0.003°/s to less than 0.0001°/s even under different temperatures. After the correction of actuation gain nonlinearity, the bias instability (BI) of whole-angle MSRG is improved by about 3.5 times from 0.101°/h to 0.029°/h and the scale factor nonlinearity (SFN) is reduced by almost one order of magnitude from 2.02 ppm to 0.21 ppm. [ABSTRACT FROM AUTHOR]

Purpose: This work measures the performance characteristics of a hemispherical resonator gyroscope (HRG) and compares it with a numerical model. Design/methodology/approach: This work we explore the optical and piezoelectric measurement methods to determine the resonant frequency of HRG. These experimental results are compared with their numerically obtained values. To explore the performance characteristics, the effect of varying actuation voltages on the sense mode displacement and the piezoelectric sensor output was studied in the absence of input angular rate. The structure was then subjected to range of angular rate signals, at a constant actuation voltage and the corresponding sensor response was analysed. Findings: Experimental values of the resonant frequencies in drive and sense modes are found to be within 8% of the numerical results. The sensor output depicts a quadratic dependency on the applied angular rate, which is synchronous with the governing equations of the HRG. The experimental output is within 12% of that obtained numerically. The sensor is found to resolve upto 0.24 rad/s. Originality/value: This work presents an in-house developed inexpensive measurement setup for static and dynamic characterization of mesoscale MEMS gyroscopes. The measurement setup can also be modified accordingly for measurement of other MEMS-based devices. [ABSTRACT FROM AUTHOR]

Purpose: The effect of viscosity on the performance of disk-shaped electromechanical resonators has been studied and investigated in the past. The vibration frequency of a disk-shaped resonator changes according to the viscosity of the liquid which the resonator is in contact with. Therefore, the purpose of this paper is based on design a sensor for measuring the viscosity of liquids using a disk-shaped electromechanical resonator. The viscosity of liquids is of interest to researchers in industry and medicine. Design/methodology/approach: In this paper, a viscosity sensor for liquids is proposed, which is designed based on a disk-shaped electromechanical resonator. In this proposed sensor, two comb drives are used as electrostatic actuators to stimulate the resonator. Also, two other comb drives are used as electrostatic sensors to monitor the frequency changes of the proposed resonator. The resonance frequency of the resonator in response to different fluids under test varies according to their viscosity. Findings: After calibration of the proposed sensor by nonlinear weights, the viscosity of some liquids are calculated using this sensor and results confirm its accuracy according to the liquids real viscosity. Originality/value: The design of the proposed sensor and its simulated performance are reported. Also, the viscosity of several different liquids are evaluated with simulations of the proposed sensor and presented. [ABSTRACT FROM AUTHOR]

Purpose: In the measurement of liquid density and viscosity, the change of resonance parameters due to the parasitic parallel capacitance of resonator affects the measurement accuracy. To improve the accuracy, a method was proposed to compensate the parasitic parallel capacitance of resonator by adding an electrode. Design/methodology/approach: The new electrode (compensation electrode) was added into resonant sensor to make compensation capacitance. The closer the compensation capacitance was to the parasitic parallel capacitance, the better compensation was. The structural parameters of resonant sensor with the compensation electrode were determined by the simulation and experiment. Findings: The effect of this method was examined by the experiment. The relative errors of density and viscosity were less than 0.15, 0.5 % and standard deviations were less than 0.0004 g/cm3 and 0.005 mPas, respectively. Practical implications: The experimental results show that this method is valuable for the parasitic parallel capacitance compensation of immersed resonant sensor. Originality/value: This paper has not been published in other journals. [ABSTRACT FROM AUTHOR]

A quad-band microstrip bandpass filter (BPF) based on a 13-mode resonator is proposed in this article with compact size, high band‐to‐band isolation, and multiple transmission zeros (TZs). The proposed filter is constructed by two transmission paths from the input to the output port, which employs the transversal cancellation mechanism of two transition paths to introduce extra nine TZs. Therefore, a total of 12 TZs are located at 0.2, 1.8, 2, 3.88, 4.61, 5.24, 5.9, 9.26, 9.51, 12.32, 12.75, and 13.27 GHz, respectively, realizing high selectivity. Moreover, the designed filter can achieve quad passbands with centered frequency at 0.95, 2.78, 7.32, and 10.63 GHz for the requirement of multi-service in modern communication systems, with wide bandwidth of 235, 790, 2200, and 1540 MHz, respectively. The measured results agree well with the simulation results, which proves the feasibility of the design method. [ABSTRACT FROM AUTHOR]

In this study, a novel design methodology of multibeam focusing using a checkerboard metasurface is proposed and investigated. The metasurface is designed as a single-layer anisotropic surface consisting of two identical electric field coupled resonators (ELCRs) separated by a dielectric substrate. When a circularly polarized (CP) wave is incident on the unit cell of the metasurface and the unit cell is rotated to angle of θ, the unit cell has a transmitted phase shift of 2θ. The multibeam transverse and longitudinal focusing and control easily can be achieved by a structural rearrangement of metasurface in the form of a checkerboard without mathematical method. The feasibility of the proposed methodology is confirmed by full-wave simulation and measurement results at 5.8 GHz. [ABSTRACT FROM AUTHOR]

The mechanisms underlying the stability of the intensity imbalance between the left‐ and right‐circulating lasing modes in a GaN hexagonal microdisk resonator are investigated. Finite‐difference time‐domain simulations reveal that the imbalance is determined by the position of the point light source (seed light for lasing) inside the resonator. The coupling mechanism between the resonance modes and light from the source is clarified using numerical calculations. In addition, it is confirmed that light is highly coupled with one of the circulation modes when the source is placed off the bilateral symmetry axis of the mode near the side of the resonator, without any influence of the polarization of the source. The results indicate that the imbalance of the lasing modes observed in the experiments is determined by the position of the seed light near the side of the resonator, which must be spontaneous emission from impurities or defects, such as donor–acceptor pairs, donor‐bounded excitons, basal plane stacking faults, or the transition of free electrons in the conduction band to acceptor levels et al. [ABSTRACT FROM AUTHOR]