Resonance Frequencies Of Modes Research Articles

Investigation of resonant mode and simultaneous excitation of multiple modes in slot‐coupled rectangular dielectric resonator antenna for multiband applications

AbstractA low‐profile rectangular dielectric resonator antenna (RDRA) through the slot‐based feed method is studied for the multiband operation. Based on the perfect magnetic wall (PMW) model and dielectric waveguide model (DWM), field distributions and resonant frequencies of the RDRA intrinsic modes are calculated for multimodal analysis. The microstrip backed slot coupling scheme is employed for the simultaneous excitation of multiple modes. A prototype is fabricated and validated. By generating 10 modes simultaneously including TEy111 to TEy711, and TEx221 to TEx421 modes. The RDRA is able to provide good multiband performance.

Dual-wideband sandwich coupled three-lines bandpass filter based on modified open-stub loaded stepped impedance resonator with improved second harmonic for 5G wi-fi/ ku-band applications

A modified open-stub-loaded three sections stepped impedance resonator (OSL-TSIR) is analysed in this paper. Based on the even- and odd-mode analysis technique, it can be easily achieved that the proposed OSL-TSIR have the advantage of improving spurious resonant mode frequencies. Besides, more degrees of freedom are provided to control the location of harmonics. A third order Chebyshev dual-wideband bandpass filter composed of cascade parallel sandwich coupled three-lines sections of types SC/CS and OSL-TSIR which act as multi-mode resonator was developed and the design procedure is described. To demonstrate the efficiency of the design process, DB-BPF operating at 5.15/12.58 GHz (2.45 f0) and FBW of 19/5.7% for 5G Wi-Fi/Ku-band Applications is designed and simulated. Three transmission zeros are created, resulting in the excellent band-in-band isolation and high selectivity. The filter has a miniaturized size of 27 mm × 18 mm.

Cubic root-locus format for structures with a local viscous damping device

The tuning and efficiency of a local viscous damper on a flexible structure is described via an approximate representation of the characteristic equation in the form of a cubic polynomial. Increasing the viscosity to the limit of locking of the device typically leads to an increased modal resonance frequency, but may lead to a decrease. A cubic approximation is developed covering both cases in which the effect of the non-resonant modes is represented by an equivalent stiffness or inertia term, respectively. The magnitude of the stiffness or inertia parameter is determined by the change in resonance frequency following from locking of the device, and thus the cubic root-locus curve is determined by only two parameters: the original undamped resonance frequency, and the frequency after locking. The length parameter along the curve is given by a suitably scaled non-dimensional damping parameter. It is demonstrated that when introducing the geometric mean of the unlocked and locked frequencies the complex root locus curve for increasing damping parameter consists of inverse points with respect to a circle with the geometric mean frequency as radius, and furthermore the inverse points correspond to reciprocal values of the normalized damping parameter. The explicit results of optimal damper tuning and the resulting structural damping enable direct design based solely on the three parameters, that can typically be extracted from a standard finite element analysis of the structure. Two examples demonstrate the accuracy of the cubic format, and clarify the reason for decrease of the modal frequency by damping for certain cases.

Dual-Band Uniaxial Dielectric Anisotropy Sensor Using Coupled-Line Resonators

In this paper, a new dual-band sensor to measure uniaxial anisotropy at two frequency bands is proposed. This sensor is composed of two dual-mode resonators separated by a T-shaped structure implemented in microstrip technology. The configuration of vertical and horizontal electric field lines for the two resonance modes allows for the characterization of a uniaxial anisotropic sample placed on top of the sensor. The resonance frequencies of different modes are separated using active S-parameters measured at the input port. They are subsequently used in the space mapping process to extract the dielectric constants of the sample in two directions, parallel and normal to the surface of the sensor, by means of electromagnetic analyses. The sensor is used to extract the dielectric constants of anisotropic FR4, RO4003C, and RO3010 samples at 2.4 and 3.4 GHz. An isotropic PTFE sample is also characterized to verify the reliability of the proposed method. Two single-band sensors are also implemented to measure RO3010 sample and the extracted dielectric constants are compared to those resulted from the proposed dual-band sensor.

Numerical investigation of wave interaction with two closely spaced floating boxes using particle method

This paper applies Improved Meshless Local Petrov-Galerkin method based on Rankine source function (IMLPG_R) to simulate two-dimensional wave interaction with two closely spaced floating boxes. The present study considers four different box configurations based on the degree of freedom, namely FF (both boxes fixed), HH (only heave allowed), RR (only roll allowed), and MM (both heave and roll allowed). The influences of the different degrees of freedom of the boxes on the wave elevation in the gap, and forces acting on the boxes, are investigated. Regular waves with a wave period ranging from 0.6s to 1.6s and two focused wave groups based on the JONSWAP spectrum with a peak frequency of 0.869Hz and 1.081Hz, respectively, are employed for the analysis. The piston mode resonance frequencies of different configurations were observed to vary slightly depending on the motion restrained. Compared to the FF configuration, the MM configuration showed a 28.3% increase in wave amplification in the gap. Some unique characteristics observed in the response amplitude operator (RAO) and flow patterns around the boxes are explained using instantaneous velocity and vorticity diagrams. The response of various configurations under a nonlinear transient-focused wave is also examined. The first-order and second-order time series of wave elevation in the gap is obtained by using the four-phase combination method.

EFFECT OF CHELATING AGENTS, SINTERED TEMPERATURE AND HEAT TREATMENT DURATION ON THE STRUCTURAL AND ELECTRICAL PROPERTIES OF BiFeO3


 
 
 A multiferroics BiFeO3 (BFO) samples are prepared by co-precipitation and sol-gel methods. Various combinations of chelating agent, sintering temperature and heat treatment durations tried to prepare single phase BiFeO3 samples. Sol-gel method is found more suitable to synthesize phase pure BiFeO3 samples. The samples were characterized by XRD, SEM, EDX, Electrical resistivity and optical reflectivity measurements. The distorted rhombohedral perovskite structure R3c has been confirmed. The grain size and lattice constant of the samples are also calculated using XRD patterns. The resistivity of the samples is measured at room temperature. The resistivity is found to increase on changing the chelating agent from Tartaric acid to Tartaric acid plus Ethylene glycol. The resistivity reveals the semi conductivity behavior of the BFO samples. The measurement of infrared reflectivity of BFO samples at room temperature reveals optical phonons. The resonant frequency of the phonon modes is determined and reported.
 
 

드릴링 가공을 위한 초음파 유닛 설계

With the development of new alloys and composites, existing drilling techniques have technical constraints for machining difficult-to-cut materials. To overcome these constraints, researchers have developed various drilling methods, including ultrasonic-assisted drilling (UAD). An ultrasonic spindle with a 30 kHz resonant frequency was designed to apply UAD to hole processing. The resonance frequency and vibration mode were predicted using the finite element method (FEM), and a vibration nodal plane was selected. The resonance frequency and impedance characteristics of the ultrasonic spindle were determined using an impedance analyzer, and an error of approximately 1.9% was predicted using the FEM. Next, the vibration characteristics of the ultrasonic spindle were analyzed using a laser displacement system. The vibration displacement tests showed amplitudes of 39.7 and 0.5 μm at the end of the drilling tool and the nodal plane, respectively. The design validity of the manufactured ultrasonic spindle was demonstrated based on experimental drilling results.

Resonant Oscillations within Multiple Moonpools for a Fixed Rectangular Vessel

_ We present experimental results of resonant free surface oscillations within three circular moonpools arranged in tandem at forward, central, and aft positions of a fixed rectangular vessel in head waves. The piston mode resonance frequency is primarily captured, which decreases with the increase in the vessel draft. The aim is to study the effect of body diffraction on the free surface amplitude and phase of the oscillating water columns at the three locations. The results indicate that, in general, the forward moonpool has the highest response amplitude, whereas the relative amplitudes of the central and aft moonpools depend on the wave frequency. It is observed that the nondimensional response amplitude increases nonlinearly with decreasing wave steepness close to the resonance frequency, while the effect diminishes at lower wave frequencies. The oscillation phase differences between the moonpools show effects of wave-body interaction, a phenomenon dependent on the vessel draft and wave frequency. Finally, the study includes a comparison of the responses at the three moonpool locations between multiple and single configurations. Introduction A moonpool is a vertical opening through the ship deck and open to the sea at the bottom, which is installed in vessels specialized in certain offshore operations. Resonant water column oscillations are encountered in moonpools (Aalbers 1984) due to vessel operations in waves. On the other hand, oscillating water columns (OWCs) have been extensively researched, primarily due to their potential for ocean wave energy conversion (Evans 1978; Heath 2012; Falcão & Henriques 2016). Now, considering design perspectives, the focus of the studies on water column resonance in waves depends on the specific marine application. For example, wave energy converters would require maximized OWC responses for efficient energy capture (Evans & Porter 1995; Morris-Thomas et al. 2007), while large free surface oscillations within moonpools of drillships have adverse effects on the vessel dynamics (Fakuda 1977).

Ultrasound detection using a thermal-assisted microcavity Raman laser

Optical microcavities have emerged as promising platforms for ultrasound detection. One of the main tendencies in recent studies is to develop high-Q microresonators for ultrasensitive ultrasound detection, while the nonlinear optical effects become significant but are generally neglected. Here, we propose a thermal-assisted microcavity Raman laser for ultrasound detection. Acoustic waves modulate the resonant frequency of the cavity mode, altering the coupled efficiency of a fixed-wavelength input laser, and therefore the output Raman power. Experimentally, the noise equivalent pressure reaches as low as 8.1 Pa at 120 kHz in air. Besides, it is found that the thermal effect involved in high-Q microcavities can compensate for the low-frequency noises, while without degrading their sensitivity to high-frequency acoustic waves above hundreds of kilohertz. Therefore, it enables long-standing stability during the measurements due to the natural resistance to laser frequency drifts and environmental disturbances, which holds great potential in practical applications of ultrasound sensing and imaging.

Frequency Modulation Approach for High Power Density 100 Hz Piezoelectric Vibration Energy Harvester

Piezoelectric vibration energy harvester (PVEH) is a promising device for sustainable power supply of wireless sensor nodes (WSNs). PVEH is resonant and generates power under constant frequency vibration excitation of mechanical equipment. However, it cannot output high power through off-resonance if it has frequency offset in manufacturing, assembly and use. To address this issue, this paper designs and optimizes a PVEH to harvest power specifically from grid transformer vibration at 100 Hz with high power density of 5.28 μWmm-3g-2. Some resonant frequency modulation methods of PVEH are discussed by theoretical analysis and experiment, such as load impedance, additional mass, glue filling, axial and transverse magnetic force frequency modulation. Finally, efficient energy harvesting of 6.1 V output in 0.0226 g acceleration is tested in grid transformer reactor field application. This research has practical value for the design and optimization process of tunable PVEH for a specific vibration source.

Analytical Approaches for Effects of Edge-Located EBG Structure With Defected Ground Structure on Cavity-Mode Resonances of Power/Ground Planes

The effects of an edge-located electromagnetic bandgap (EL-EBG) structure including a defected ground structure (DGS) on the cavity-mode resonances of power/ground planes are analyzed for the power integrity design of high-speed packages and printed circuit boards (PCBs). The EBG structure localized in the power/ground planes significantly affects the power integrity characteristics. However, previous studies did not consider this effect. An analytical equation and a numerical method based on the contour integral method (CIM) are developed to examine the EL-EBG effect on cavity-mode resonance. The proposed method reveals that the employment of the EL-EBG structure results in resonance frequency reduction, generation of hybrid-type mode, irregular relationship between mode resonance frequencies, and different distribution of mode intensity compared to conventional open-ended power/ground planes. The proposed CIM modeling and analysis for investigating the distinctive features of the EL-EBG effect are validated using full-wave simulations and measurements. The rigorous analysis of the EL-EBG effect enables the improvement of power integrity design for power/ground planes combined with EBG structures. Moreover, the proposed CIM modeling can obtain fast and accurate results for EL-EBG power/ground planes compared to full-wave simulations.

Electric-Field Null Bending of a Single Dual-Port Patch Antenna for Colinear Polarization Decoupling Using Characteristic Modes Analysis

A novel design concept for bending the electric-field nulls of a single dual-port microstrip patch antenna (MPA) for colinear polarization decoupling is proposed in this communication. Initially, the electric-field distributions of the traditional MPA are theoretically studied by using characteristic mode analysis (CMA). The results demonstrate that the of electric-field nulls could be bent by combining its two modes. Hence, when the antenna is excited at the left port, electric-field nulls could be formed around the right port. In contrast, electric-field nulls are formed on the left port for the MPA under excitation of the right port. Next, a set of shorting pins is loaded below the radiating patch. Hence, the MPA reallocates the resonant frequencies of these dual modes closely to each other and combines them for low mutual coupling. After that, the slot is cut on the radiator, aiming to improve the impedance matching over the operating band. With these arrangements, the mutual coupling of the MPA between dual ports is successfully decreased with good impedance matching. In final, the proposed MPA is fabricated and measured. Good agreement between the simulated and measured results is obtained, and it proves that the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert &lt; -10$ </tex-math></inline-formula> dB of the antenna is operated in a range from 5.3 to 5.54 GHz. Besides, the antenna maintains the low-profile, single-layer, and single-element properties. Most importantly, it has generated a broadside radiation pattern with the same polarization, and its isolation is satisfactorily enhanced to above 17 dB, which is much higher than the 3.5 dB of the traditional counterpart. Hence, it can be used for in-band full-duplex (IBFD) systems.

Single-Polarized Low-Profile High-Order Bandpass Frequency Selective Surfaces Based on Aperture-Coupled Patch Resonators Under TM and TM Modes

This communication presents a methodology to construct the aperture-coupled dual-mode patch resonators (AC-DMPRs)-based periodic element to realize single- and dual-band high-order bandpass frequency selective surfaces (FSSs). Initially, a single patch resonator (PR) loaded with two sets of shorting pins is theoretically studied by using the characteristic mode analysis (CMA) method and by applying periodic boundary conditions, respectively. The results demonstrate that the radiation pattern and resonant frequency of TM00 mode in the PR can be effectively reshaped and controlled by the shorting pins, so that the TM00 and TM01 modes can be simultaneously excited under the normal incidence of a plane wave. As such, the single-mode PR is transformed into a DMPR. Moreover, such DMPRs are arranged in a back-to-back manner with coupling apertures etched on the common middle metallic layer to form an AC-DMPR-based bandpass FSS element. By reasonably reallocating the resonant frequencies of these two resonant modes and etching different apertures to provide magnetic and/or electric couplings in the AC-DMPR, single- and dual-band high-order bandpass FSSs can be conveniently and flexibly constructed, respectively. Finally, the conceptual designs are validated by measurements.

Compact, Order Extensible and Wide-Stopband Bandpass Filter Based on SIW Cavity With Rectangular Ring Slot

This brief introduces novel architectures of bandpass filters (BPFs) using a substrate integrated waveguide (SIW) cavity with a rectangular ring slot (RRS) for compact size, extensible order, and broad stopband responses. Two bandpass filters, which demonstrate a second-and a fourth-order Chebyshev response, respectively, are realized by employing identical cavities with RRS, without increasing the physical size of the circuit. A rectangular ring slot is etched along the perimeter and a metallic via is allocated towards the bottom edge of the cavity to realize the resonances. The resonant frequencies of different modes are controlled by introducing one or three slots, which enable the realization of the second and fourth-order BPFs with wide stopbands, respectively. The working principles of the filters are illustrated by applying the eigen-mode analysis, field distribution, and the coupling matrix. Finally, a second-order BPF centered at 0.87 GHz, and a fourth-order BPF centered at 0.92 GHz are synthesized, fabricated, and experimentally validated. As compared to the earlier works, the proposed fourth-order BPF offers competitive performance with a low insertion-loss of 0.7 dB, compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.036\mathbf {\lambda } ^{2}$ </tex-math></inline-formula> , and a wide passband of 22.1%. Additionally, the second- and the fourth-order BPFs achieve wide upper stopband responses of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.86{f} _{0}$ </tex-math></inline-formula> at a level greater than 20dB and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.98{f} _{0}$ </tex-math></inline-formula> at a level greater than 30dB, respectively.

Biodynamic responses of adolescent idiopathic scoliosis exposed to vibration.

Patients with adolescent idiopathic scoliosis suffer severe health issues. The unclear dynamic biomechanical characteristics of scoliosis were needed to be explored to improve the prevention and treatment in clinics. Validated 3D finite element (FE) models of thoracolumbosacral spine (T1-S1) both with and without scoliosis were developed from computed tomography (CT) images. Modal and harmonic analyses were performed to investigate the biomechanical responses of the spinal models to vibration. Resonant frequencies of the scoliotic model were lower than those of the model without scoliosis. Peak amplitudes occurred at vibrational frequencies close to the modal resonant frequencies, which caused the deformed thoracic segment in scoliosis suffered the maximum amplitude. The stresses on vertebrae and intervertebral discs in the scoliotic model derived from vibrations were significantly larger than those in the non-scoliosis model, and heterogeneously concentrated on the scoliotic thoracic segment. In conclusion, the scoliotic spine in the patients with Lenke 1BN scoliosis is more prone to injuries than the non-scoliotic spine while vibrating. Scoliotic thoracic segments in patients with Lenke 1BN scoliosis were the more vulnerable and sensitive component of the T1-S1 spine to vibration than lumbar spines. This study suggested that vibration would impair the scoliotic spines, and patients with Lenke 1BN scoliosis should avoid exposure to vibration, especially the low-frequency vibration.

The strain gradient-based torsional vibration analysis of micro-rotors with nonlinear flexural-torsional coupling

The powerful non-classical continuum theory of strain gradient elasticity is capable of effectively capturing small-scale effects in micro-structures. Based on this theory, a formulation is developed to investigate the coupled torsional-flexural vibrations of micro-rotors in the presence of inertia nonlinearities arising from the eccentricity and gyroscopic motion of the rotors. With the aid of a weighted-residual technique, coupled nonlinear partial differential equations of motion are truncated into a discrete model. Then, the resonance of the fundamental mode of the torsional vibration excited by the flexural vibration is investigated by utilizing the perturbation method of multiple scales. Moreover, a numerical simulation approach is conducted to confirm the validity of the analytical solution proposed by the multiple scales perturbation method. Obtained results for the resonant frequency and amplitude of the fundamental torsional mode indicate that the strain gradient theory can predict far more reliable results than the classical continuum mechanics for micro-rotors with very thin shafts.

Co-axial acoustic-based optical coherence vibrometry probe for the quantification of resonance frequency modes in ocular tissue

We present a co-axial acoustic-based optical coherence vibrometry probe (CoA-OCV) for vibro-acoustic resonance quantification in biological tissues. Sample vibrations were stimulated via a loudspeaker, and pre-compensation was used to calibrate the acoustic spectrum. Sample vibrations were measured via phase-sensitive swept-source optical coherence tomography (OCT). Resonance frequencies of corneal phantoms were measured at varying intraocular pressures (IOP), and dependencies on Young´s Modulus (E), phantom thickness and IOP were observed. Cycling IOP revealed hysteresis. For E = 0.3 MPa, resonance frequencies increased with IOP at a rate of 3.9, 3.7 and 3.5 Hz/mmHg for varied thicknesses and 1.7, 2.5 and 2.8 Hz/mmHg for E = 0.16 MPa. Resonance frequencies increased with thickness at a rate of 0.25 Hz/µm for E = 0.3 MPa, and 0.40 Hz/µm for E = 0.16 MPa. E showed the most predominant impact in the shift of the resonance frequencies. Full width at half maximum (FWHM) of the resonance modes increased with increasing thickness and decreased with increasing E. Only thickness and E contributed to the variance of FWHM. In rabbit corneas, resonance frequencies of 360–460 Hz were observed. The results of the current study demonstrate the feasibility of CoA-OCV for use in future OCT-V studies.

Metasurface-Loaded Off-Center Monopoles With Wideband Radiation Performance Using Characteristic Mode Analysis

A metasurface (MTS)-based reactive impedance surface (RIS) is proposed to load an eccentrically placed monopole above a ground plane for controllable wideband omnidirectional radiation. With the off-center placement, the radiation pattern of the monopole is not omnidirectional anymore, with ripples in the H-plane measured by un-roundness. The RIS is introduced above and in parallel with the finite ground plane and the monopole is placed in the center of the RIS. Characteristic mode analysis (CMA) is used to analyze the RIS-loaded monopole and to reveal the mechanism. It is found that two desired modes determine the bandwidth of the omnidirectional radiation together. The resonant frequency of the RIS mode can be easily tuned by changing the sheet impedance of the RIS. A metal-dielectric-metal constructed MTS is proposed to realize the RIS. The grid impedance of the MTS can be tuned easily by changing the size of the patch in the unit cell. For a single monopole placed off-center above a rectangular ground plane (150 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times300$ </tex-math></inline-formula> mm), the impedance bandwidth is increased from 19.6% to 32.4% with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert &lt; -10$ </tex-math></inline-formula> dB at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0} =2.5$ </tex-math></inline-formula> GHz. And the maximum un-roundness is reduced by 66.7% from 4.8 to 1.6 dB over the frequency band of 2.2–2.8 GHz. For a two-monopole antenna system with the same ground plane mentioned above, the loading MTS increases the impedance bandwidth of the monopole from 19.2% to 32.4% with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert &lt; -10$ </tex-math></inline-formula> dB at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0} =2.5$ </tex-math></inline-formula> GHz. When only one monopole is loaded with MTS in the system, the maximum un-roundness is reduced by 65.5% from 5.5 to 1.9 dB in the frequency band of 2.2–2.8 GHz. When both monopoles are loaded with MTS in the system, the maximum un-roundness is reduced by 40% from 5.5 to 3.3 dB in the frequency band of 2.2–2.8 GHz. The antenna prototypes are fabricated and measured.

Simultaneous matching, decoupling, and miniaturization in MIMO antenna by loading a folded cross resonator

A novel concept of simultaneous matching, decoupling and miniaturization in multiple input multiple output (MIMO) antenna is proposed. Firstly, the integration of matching and decoupling can be achieved by making the resonant frequency of common mode (CM) and differential mode (DM) consistent. Then, the same resonant frequency of CM and DM will move to lower frequency through changing parameters value of the folded cross resonator. The MIMO antenna will operate normally at lower frequency with low mutual coupling without increase the volume. The operating frequency of antenna is reduced from 3 to 2.5 GHz of achieving 16.7% miniaturization, and the isolation is increased from 20 to 45 dB at 2.5 GHz at the same time. The measurement and simulation results are in good agreement, which verifies the correctness of the design. The goal of matching, decoupling and miniaturization for MIMO antenna will be completed without too much software optimization and other complex structures.

A single‐surface wideband printed monopole antenna with high‐order mode compression by bending line loading

AbstractA wideband coplanar waveguide‐fed printed monopole antenna is proposed. The wideband performance of the monopole is achieved by compressing the third‐ and fifth‐order modes. By loading the bending line at the zero point of the third‐order mode of the monopole current distribution, the fifth‐order mode resonant frequency decreases significantly, while the third‐order mode resonant frequency remains almost constant. Therefore, a wideband impedance match is achieved. A fully functional prototype was fabricated and characterized. The measured results are in good agreement with the simulated results. A wideband from 2.92 to 3.66 GHz (22.5%) was achieved in a thin structure of 85 × 33 mm2, exhibiting a measured omnidirectional radiation pattern with 2.4–4.9 dBi gain.