Adjacent Resonant Frequencies Research Articles

Broadband multiresonance metasurface antenna based on characteristic mode analysis

ABSTRACT A multiresonance metasurface antenna for C-band application is proposed in this paper. A broadband metasurface with consistent radiation performance is designed using characteristic mode analysis (CMA). The metasurface is formed by 4 × 4 square patches, and circular slots of different radius are etched on the center and edge patches. To achieve consistent radiation, the size of circular slots on the corner patches is increased. The metasurface is excited by slot antenna, and multiple adjacent resonant frequencies are generated by combining two modes of the metasurface and resonant mode of slot antenna. The measured results show that the −10 dB impedance bandwidth of the antenna is 4.22–8.38 GHz (66%), and the peak gain is 8.2 dBi.

Small blind-area, high-accuracy ultrasonic rangefinder using a broadband multi-frequency piezoelectric micromachined ultrasonic transducer array

This paper presents a broadband ultrasonic rangefinder, with merits of a small blind area and high accuracy, based on a multi-frequency piezoelectric micromachined ultrasonic transducer (MF-PMUT) array. The coupling bandwidth between six types of resonant cells with adjacent resonant frequencies was studied and optimized, and these cells were then integrated into an array to broaden the bandwidth of the device. The array device showed a wide −6 dB fractional bandwidth of 108% in silicon oil. A wide bandwidth can contribute to obtaining the maximum steady-state with less excitation and reducing its residual ring-down, resulting in a small blind area. Pulse-echo ranging experiments demonstrated that the blind area was effectively reduced to 5 mm due to the multi-frequency array. For short distance measurements (<250 mm), the error was well controlled within ±0.3 mm and the 3σ accuracy was 0.445 mm. Compared with earlier reported PMUTs designed for bandwidth enhancement, the proposed broadband MF-PMUT array is much simpler in design and fabrication, revealing it as a promising candidate for short-distance high-accuracy measurements.

Higher-Order Characteristic Modes-Based Broad-Beam Dielectric Resonator Antenna

A dielectic resonator antenna (DRA) with simple configurations but an ultrabroad beam is proposed by combining the characteristic modes (CMs) from the dielectric block and ground. To accurately identify these CMs, an effective design methodology based on the surface integral equation-based substructure characteristic mode analysis is developed. Compared to the traditional CM-based DRA design approach, this new method provides much more useful modal information by eliminating spurious modes and mode mixing. The wide-beam DRA is then designed by selecting a set of higher-order CMs with complementary radiated beams and adjacent resonant frequencies. The results from full-wave simulation and measurement are also displayed. Good consistency is observed.

Sensing and slow light properties of dual-band terahertz metamaterials based on electromagnetically induced transparency-like

&lt;sec&gt;Electromagnetically induced transparency (EIT) is a quantum interference phenomenon in a three-level atomic system. The generation of quantum interference effect significantly reduces the light absorptivity of the specific frequency that is strongly absorbed, and produces a sharp “transmission window” in the resonance absorption region. The EIT is usually accompanied by strong dispersion, which significantly reduces the group velocity of light and enhances the nonlinear interaction. The EIT phenomenon of atomic system usually needs to be observed at very low temperature or high intensity laser, which is a very serious challenge for the application of EIT technology. The simulation of electromagnetically induced transparency using metamaterials can effectively break through these limitations.&lt;/sec&gt;&lt;sec&gt;In this work, an electromagnetically induced transparency-like terahertz metamaterial structure with three bright modes is proposed and investigated. Two weakly hybrid states are composed of two bright modes with similar resonant frequencies. The energy oscillates back and forth between the two modes, and a transparent window is generated between the two resonance points. The designed metamaterial is composed of three groups of bright modes with adjacent resonant frequencies, and the three groups of bright modes are coupled to produce two transparent windows. The electromagnetically induced transparency-like formation mechanism is analyzed based on the simulation curve and electric field distribution. In addition, the sensing properties of metamaterial are determined by simulation and calculation, and the refractive index sensitivities of the two windows can be as high as 451.92 GHz/RIU and 545.31 GHz/RIU under the optimal thickness of the measured substances. Through the sensing simulation of six petroleum products, it is verified that the dual-band has more excellent advantages in dielectric constant matching than the single frequency band. The characteristics of the designed metamaterial in the slow light effect are also studied. The maximum group delay times of the two windows can reach 9.98 ps and 6.23 ps. Therefore, the structure is considered to have an important application value in the field of high sensitivity sensors and slow light devices.&lt;/sec&gt;

Wideband high‐gain multiresonance antenna based on polarization‐dependent metasurface

AbstractIn this article, a novel polarization‐dependent metasurface (PDMS) structure is presented and applied to realize a wideband high‐gain antenna with multiple resonances. The PDMS element is obtained by cutting slots into the square patch unit cell of conventional metasurface (MS). Very different from the conventional MS structure, the proposed PDMS element exhibits different reflection phases and resonance frequencies, depending on the polarization state of the incident plane wave. By properly tailoring the reflection‐phase curves under different polarizations, a proper PDMS structure is introduced. Then, by arranging the PDMS elements along different orientations, a multiresonance radiator can be realized. When applying the proposed radiator to the slot‐coupled MS antenna, one broadband PDMS‐based antenna with multiple adjacent resonance frequencies can be realized by the combination of coupling slot‐mode and PDMS modes. For verification, a PDMS radiator with 4 × 4 unit cells is designed accordingly and applied to realize one C‐band broadband PDMS‐based antenna in a low profile (0.06 λ0). The measured results of the fabricated prototype PDMS‐based antenna exhibit a large –10 dB impedance bandwidth of 55% (4.31‐7.58 GHz), a maximum available gain of 10.898 dBi, and a 2‐dB gain bandwidth of 30.81% (5.1‐6.96 GHz).

Broadband Stable-Gain Multiresonance Antenna Using Nonperiodic Square-Ring Metasurface

A multiresonance antenna based on a nonperiodic square-ring metasurface (MS) is proposed, which has large bandwidth and stable radiation gain. The nonperiodic MS radiator is formed by several adjustable square-ring patches and fed by a microstrip line through a coupling slot. By properly adjusting the widths of these square rings, different resonance modes can be inspired for the MS according to the characteristic mode analysis. Combined with the resonance mode of the coupling slot, multiple adjacent resonance frequencies occur and thus realize a wideband and consistent radiation. For demonstration, a C-band wideband antenna based on the proposed 4 × 4 square-ring MS units with a low profile of 0.06 λ 0 is accordingly designed and fabricated. The measured results indicate a large impedance bandwidth of 54% (4–7 GHz) and an extremely stable gain with 2 dB gain bandwidth of 32% (4.76–6.54 GHz).

Dynamic stiffness design of plate/shell structures using explicit topology optimization

The aim of this article is to present a novel and viable topological design approach for minimizing dynamic compliance of stiffened plate/shell structures subjected to time-harmonic loading with prescribed excitation frequency. In this method, the generalized incremental frequency technique (GIF) is introduced to transform the optimization problem into several sub-problems by making the prescribed excitation frequency located within different sub-intervals constructed by adjacent resonance frequencies. Based on this, a set of local optimum designs are identified by associating with the smallest value of dynamic compliance in each sub-interval, and then the optimized solution is selected from among these candidate solutions. Furthermore, the GIF technique is integrated into a Lagrangian-based topology optimization framework, where the stiffening topologies are represented explicitly by a set of geometric primitives such as line segments. In order to get an optimal layout solution, a special interpolation scheme called stiffness and mass transformation approach (SMTA) is presented to separate the line segments from the underlying FEM grids, so that they can move freely within the design domain. To demonstrate the benefits this method affords for dynamic design problems, three numerical examples are validated in detail. In each of the cases the optimization enables a significant reduction in the dynamic compliance. The proposed method allows for more flexibility in topology optimization, which is applicable for large-scale practical dynamic design problems.

Design of a Wideband Circularly Polarized Stacked Dielectric Resonator Antenna

A kind of circular polarized (CP) stacked dielectric resonator (DR) antenna with wide bandwidth and high gain is presented in this communication. For this design, a two-layer DR with improved performance in bandwidth and gain is used as the basic resonator. By further applying it into a stacked design, two similar modes with adjacent resonant frequencies can be merged together, providing a wide axial ratio bandwidth of more than 20%. The single-feed CP operation is achieved by adopting a coupling cross-slot, which is beneficial for fine-tuning and array forming, as compared to multifeed structures. Two design examples working at different frequency bands and for different senses of CP have been presented to demonstrate the effectiveness of the design concept.

Tunable microwave frequency comb generation based on double-loop mixing-frequency optoelectronic oscillator

With the development of wireless communication technology and micro-cell technology, optical-borne microwave technology, specially optical-borne multi-carrier technology has become one of the most important trends for generating high-quality sources. Therefore, the efficient generation of high-quality microwave signals has always been a requirement in wireless communication systems. Due to its low-noise and high-frequency output characteristics, photoelectric oscillator is widely used to generate high-quality microwave frequency sources in communication systems. Combining the advantages of photoelectric oscillator's low-noise output and direct-modulated laser's gain-switching state characteristics, a tunable optical-borne microwave frequency comb scheme based on dual-loop mixing-frequency photoelectric oscillator is proposed in this paper. And a direct-modulated laser operating in a gain-switching state is used to generate the original optical-borne microwave frequency comb signals. The dual-loop adjacent resonant frequencies are separated by two different high-frequency microwave bandpass filters. The beat frequency of adjacent frequencies mentioned above is injected back into laser to form photoelectric resonance, and thus enhancing the generated original optical-borne microwave frequency comb signals. To suppress the side modes caused by long resonant cavity, a polarized dual-loop structure is used in the system, and thus improving the noise characteristics of output signals. After experimental analysis, the dual-loop filtered resonant microwave signals and low-phase-noise microwave comb signals with a frequency interval of 797.4 MHz are all obtained. The microwave output side-mode suppression ratio after polarized dual-loop adjustment is improved to 47 dB. And microwave comb signal's first-order carrier phase noise is lower than-101.7 dBc/Hz at 10 kHz,-115.2 dBc/Hz at 50 kHz. In addition, higher-order carriers all come from the light multiplication of first-order carrier, they share the same low noise characteristics with first-order microwave comb signal. The output power of first-to-fourth, fifth-to-thirteenth order carriers are balanced to 10 dB by photoelectric resonance injection. And their side-mode suppression ratios are all better than 40 dB. Furthermore, theoretically, the comb interval can be adjusted to any frequencies by changing the center frequencies of two high-frequency bandpass microwave filters. Therefore, optical-borne multi-carrier microwave signals are generated efficiently and cost-effectively by this tunable optical-borne microwave frequency comb scheme, and the generated low-noise multi-carrier frequency sources meet the demand of an optical-borne microwave wireless communication system.

An inkjet-printed microstrip patch sensor for liquid identification

In this paper, we propose a compact microstrip patch sensor using radio frequency (RF) signals to identify different liquids. The operation of the proposed sensor depends on the fact that liquids of different dielectric constants have different resonance frequencies. The proposed patch sensor is composed of radiator and ground fabricated by silver nanoparticle (AgNPs) ink and separated by empty chamber of 5mm height for containing liquid sample. The radiator and the ground are printed on glass substrate by using commercialized inkjet printer Dimatix Material Printer (DMP). To obtain the best sensor parameters, we propose simple design procedure, which finds not only maximum frequency separation between two adjacent resonance frequencies but also lowest reflection coefficients at the resonance frequencies. Through finite element method based ANSYS high frequency structure simulator (HFSS) simulation, we obtain sensor parameters, which can identify water, ethanol, water/ethanol 50:50 and synthetic engine oil. The designed sensor has at least 80MHz resonance frequency separation and shows maximum −25dB reflection coefficients at resonant frequencies. Remarkably, the fabricated sensor has 140MHz minimum frequency separation and maximum −29dB reflection coefficient. By comparing existing sensors, we show that the proposed sensor has outstanding identification capability. Therefore, the proposed patch sensor can be utilized in RF tunable liquid detection applications.

A Band-Notched Absorber Designed With High Notch-Band-Edge Selectivity

In this paper, a band-notched absorber with high notch-band-edge selectivity is proposed and investigated. It is formed by introducing a narrower and full reflectance band into a wider absorption band. For each absorbing unit cell, two independently magnetic and electric resonances with adjacent resonant frequencies are employed to develop the narrower and full reflectance band, while a dipole-shaped metal strip with a resister printed on one side of the supporting substrate and a ground plane is used to realize the wider absorption band. By retrieving relative equivalent circuits of each cell, the performance of the proposed absorber can be qualitatively analyzed. Simply through tuning the frequencies of the independently magnetic and electric resonances, the performance of the notched band can be adjusted with high notch-band-edge selectivity. A sample of an absorber with the notched band frequency from 8.2 to 9.8 GHz, good absorption band from 4.8 to 8.0 GHz and 10.2 to 16 GHz has been designed, fabricated, and measured. Good agreement among circuit analysis, simulation results, and measurement results is finally obtained.

Wideband Segmented Loop Antenna With Dual-Polarized Omnidirectional Patterns for Mobile Platforms

A wideband planar double-segmented loop antenna that can excite different modes with perpendicular polarized omnidirectional radiation patterns is designed for mobile platforms. The proposed antenna combines these resonant modes with adjacent resonant frequencies for wideband application. One of the modes is induced by the loop element itself and generates horizontally polarized radiation pattern. Meanwhile, the other mode generates vertically polarized radiation pattern when the ground plane is excited by the loop element and operates as a radiator. The measured results confirm that the antenna is capable of achieving wide bandwidth (10-dB return loss) from 2.1 to 2.9 GHz (the corresponding fractional bandwidth is 32%). The average total realized gain of the antenna is 2.75 dBi over the entire operating bandwidth.

An experimental and theoretical study of two-dimensional traveling waves in plates

The present work explores the generation of two-dimensional steady-state flexural waves that are non-reflective on a thin rectangular plate with free boundary conditions when excited by two macro-fiber composites (MFCs). The voltage signals to the MFCs have a frequency lying halfway between two adjacent resonant frequencies with a phase difference of [Formula: see text]. Locations of MFCs and frequencies of actuation are varied to study the response of the plate due to these forces. A finite element plate model is developed and updated based on experimental modal tests on the plate. This model is able to predict up to the 40th damped eigenvalue with a maximum error of 2.5% and match mode shapes accurately, with a lowest Modal Assurance Criterion value of 0.92. Numerical simulations of traveling waves have been carried out and are compared with experimental results. Preliminary results show that the location of the MFCs and the frequency of excitation have an effect on the type and the quality of the traveling waves. These results shall lay the foundation for an exhaustive analysis of planar traveling waves in plates.

COMPACT TRIPLE-BAND MONOPOLE ANTENNA FOR 2.4/5.2/5.8 GHz WLAN OPERATIONS

A novel compact monopole antenna with triple-band operation is proposed in this paper. The proposed antenna, fed by a 50-› microstrip line, consists of an inverted-L-shaped microstrip feed line loaded with a parasitic strip and a protrudent mirrored quasi-F-shaped strip on the ground plane, with a compact overall size of 20 £ 25mm 2 . The protrudent mirrored quasi-F-shaped strip is aimed to excite a resonant mode at 2.4 GHz. Meanwhile, with the introduction of the parasitic strip to the inverted-L shaped strip, two adjacent resonant frequencies at 5.2/5.8 GHz are obtained. The numerical and experimental results exhibit the designed antenna operates over triple frequency ranges, satisfying the standards of wireless local area networks (WLAN) both in IEEE 802.11b/a/g at 2.4-GHz, 5.2-GHz, and 5.8-GHz. Besides, the antenna is fabricated and measured, and the simulation and measurement results of the return loss, radiation patterns and peak antenna gains are studied showing that the presented antenna is in good performance.

휴대 방송용 단말기에 적합한 다중 대역 및 광대역 안테나 설계

본 논문에서는 휴대 방송용 기기에 적합한 다중 대역 및 광대역 안테나를 제안한다. 제안된 안테나는 두 복사체의 공진 주파수를 인접시킴으로써 DVB-H 서비스 대역에서의 광대역 특성을 만족시키고, 체배 주파수를 이용하여 DAB 서비스 대역에서 동작 가능케 한다. 3개의 공진 주파수 조정함에 있어서 상호 영향이 적기 때문에 비교적 쉽게 대역폭을 만족시킬 수 있다. 제작된 안테나는 DVB-H 서비스 대역인 <TEX>$470{\sim}740\;MHz$</TEX>와 DAB 서비스 대역인 <TEX>$1,450{\sim}1,480\;MHz$</TEX> 대역에서 VSWR 2:1 이하의 특성을 가지며, 각각 <TEX>$1.97{\sim}4.10\;dBi$</TEX>와 <TEX>$1.98{\sim}2.04\;dBi$</TEX>의 최대 이득 특성을 갖는다. The multi-band and wide-band antenna for a portable broadcasting terminal is proposed. The proposed antenna consists of two radiators with a parallel structure. The antenna has an enough wide impedance bandwidth for the DVB-H(Digital Video Broadcasting-Handheld) service band since two radiators have adjacent resonance frequencies and operates in the DAB(Digital Audio Broadcasting) service band using the third harmonic of the radiator 1. The fabricated antenna has VSWR characteristics of less than 2:1 in the frequency band <TEX>$470{\sim}740\;MHz$</TEX> for DVB-H and <TEX>$1,450{\sim}1,480\;MHz$</TEX> for DAB. The measured peak gain of the antenna is <TEX>$1.97{\sim}4.10\;dBi$</TEX> in the DVB-H band and <TEX>$1.98{\sim}2.04\;dBi$</TEX> in the DAB band.

DESIGN OF WIDE-BAND DIELECTRIC RESONATOR ANTENNA WITH A TWO-SEGMENT STRUCTURE

This paper discusses the analysis of a novel two-segment rectangular dielectric resonator antenna (DRA) for broadening of the impedance bandwidth. In the proposed configuration, two rectangular dielectric sections are used which are separated by a metal plate. With this configuration, it is possible to excite two adjacent resonant frequencies. Utilizing the two-segment thin DRA and skillfully varying its aspect ratio, an appropriate structure is obtained that illustrates more than 76.8% impedance bandwidth (for S11>10 dB) at 3.32- 7.46 GHz frequency band.

Broadband rectangular microstrip antenna with pair of toothbrush-shaped slots

A novel broadband design of a probe-fed rectangular microstrip antenna with a pair of toothbrush-shaped slots embedded close to the nonradiating edges of the patch is presented. The proposed broadband design is achieved by the excitation of two adjacent resonant frequencies of the TM10 and TMδ0 modes (1 &lt; δ &lt; 2), to obtain a wide operating bandwidth. An antenna bandwidth as large as ~2.6 times that of a conventional rectangular microstrip antenna has also been obtained. Details of the proposed design and experimental results are presented.

RF hole-burning within inhomogeneously broadened Raman heterodyne NMR signals

A second fixed-frequency RF source is introduced within the technique of Raman heterodyne detection of nuclear magnetic resonance and used to burn spectral holes in the I2=+or-1/2' implies/implied by +or-3/2' transitions of Eu3+ in KEu(WO4)2. At 1.8 K the hole has a width (FWHM) of 350 Hz whereas the homogeneous width of the transition determined from Raman heterodyne-detected nuclear spin echoes is 220 Hz. At 4.2 K the width of the RF hole is 1300 Hz and the homogeneous width is 660 Hz. The holes are asymmetric in shape and displaced by about 100 Hz to the low-energy side of the burn frequency; this is attributed to cross-relaxation between the resonant ions and ions with adjacent resonant frequencies. The effect of the burn frequency and burn power on the shape and depth of the holes is reported. In a magnetic field, burning in one Zeeman component also gives auxiliary holes in the other Zeeman components. The hole spectrum gives an increase in resolution of an order of magnitude compared with the regular Raman heterodyne scheme.

Vibration sensor for an automotive vehicle

A vibration sensor for an automotive vehicle having a multi-peak vibration characteristic of wider responsiveness and of a higher S/N ratio. The vibration sensor comprises a plurality of piezoelectric vibrators so arranged that the piezoelectric voltage signals from the vibrators are synthesized in reverse polarity between two elements having two adjacent resonant frequencies, when the element are deformed in the same direction. Therefore, the voltages are synthesized in the same polarity, when engine knocking frequency lies between two adjacent sensor resonant frequencies, because a vibrator is 180 degrees out of phase with another adjacent vibrator.