Outer Resonator Research Articles

Effect of Insert Misalignment on a Triangular Corrugated Coaxial Cavity Gyrotron

In this paper, the field analysis of a triangular corrugated coaxial cavity with misaligned insert is carried out for a megawatt-class sub-terahertz wave gyrotron. In misalignment analysis, both parallel displacement of the insert axis and tilting of the insert axis with the outer resonator axis are considered. Graff's addition theorem is used for deriving the eigenvalue equation of the coaxial cavity with such a misaligned insert. Mathematical formulations are carried out to include the effect of insert misalignment on the beam coupling coefficient and ohmic wall loading of the outer cavity and insert of the coaxial cavity gyrotron. The effect of structural misalignment of the insert on the operation of 2-MW, 220-GHz coaxial cavity gyrotron is analyzed. It is shown that insert misalignment reduces RF output power as well as increases ohmic wall loading of the insert beyond the prescribed cooling limit. Compared to tilting of the insert, parallel displacement of the insert causes more deterioration in the gyrotron operation. Comparative studies are also performed for a coaxial cavity with rectangular slots on the insert.

A Monopole Antenna with Offset-fed Microstrip Line for Wireless Application

ABSTRACTAn offset-fed microstrp line antenna with split ring and complementary split ring resonator is proposed for wireless applications. FR-4 substrate of 19.18, 22.64 and 1.6 mm3 with dielectric constant () of 4.4 is used to print the proposed antenna. The radiating element of antenna consists of split ring structure and Complementary split ring structure fed by offset fed microstrip line to achieve multiband characteristics required for wireless applications. The resonant frequency generated by the proposed antenna with ring structure formed by split in outer vertical arm and Complementary Split Ring Resonator (CSRR) generate resonance frequency for wireless application such as WIMAX, WLAN, WPAN.

Bandwidth enhanced metamaterial embedded inverse L-slotted antenna for WiFi/WLAN/WiMAX wireless communication

A miniaturized inverse L-slotted meta-material inspired antenna is developed and presented for WiFi, WLAN and WiMAX applications. The designed ‘Z-shaped’ metamaterial structure consists of an outer split ring resonator having an inner split ring resonator nested within the outer split ring resonator. A metallic strip connected with the inner split ring resonator top and bottom strips in a way that form like a ‘Z-shaped’ structure. The Z-shaped metamaterial is integrated on the ground plane for reduce the dependency of the ground plane and enhanced the bandwidth. The computer simulation technology microwave Studio is used to design and perform numerical analysis. The overall size of the metamaterial loaded antenna is 25 × 18 mm2 and fabricated on FR-4 dielectric substrate material (thickness of 1.6 mm and dielectric constant of 4.6). The measured operating band of frequencies from 2.36 ∼ 2.49 GHz and 3.07 ∼ 4.0 GHz covering the bandwidth of 130 MHz and 930 MHz. In addition, the measured average gain is 1.87 dBi, whereas the minimum and maximum gain are 0.1 dBi and 1.93 dBi. Finally, the proposed metamaterial loading antenna is applicable for WiFi (2.41–2.48 GHz), WLAN (2.40–2.49 GHz and 3.65–3.69 GHz), and WiMAX (3.30–3.80 GHz) wireless communications.

Design of In-Line Filters With Strongly Coupled Resonator Triplet

This paper presents a complete design procedure for in-line evanescent mode filters using an innovative pseudoelliptic structure, namely, the strongly coupled resonator triplet (SCRT). The SCRT can be seen as the combination of a strongly coupled resonator pair (SCRP) and a third resonator next to the pair. Compared to the SCRP, which at the passband frequencies generates a pole and a transmission zero, the new SCRT is capable of generating an additional passband pole, thus leading to the design of more compact in-line filters. Similar to the SCRP, the basic structure for filter design purposes is obtained by embedding the SCRT between two outer resonators. The coupling mechanisms and functional properties of this basic structure are explained. A suitable circuit model for the SCRT is introduced, thus allowing the synthesis of a low-pass prototype as well as the evaluation of the coupling coefficients and resonating frequencies to assign to the physical filtering structure. The proposed design procedure is validated by means of several examples, one of which including the detailed dimensions and experimental results of a manufactured prototype.

Capacitive couplings compact antenna for LTE/WiMAX/WLAN application

AbstractA Compact antenna applicable for wireless communication fields like Long Term Evolution (LTE) frequency division duplex (FDD) Downlink Communication (1850‐1910 MHz Canada, Latin America), Worldwide Interoperability for Microwave Access (WiMAX) and Wireless local area network (WLAN) is proposed. The antenna structure is based on 1 outer ring resonators. Here, directly fed through the patch the stepped impedance transmission line with an optimized electromagnetic coupling outer ring. The proposed design operates in the lower frequency band from 1.79 to 1.94 GHz with 1.86 GHz center frequency and in the higher frequency band form 4.69 to 5.27 GHz. The compact antenna return loss is good agreement between simulated and measured results. The antenna gain value are 0.8 dBi at 1.86 GHz, 1.1 dBi at 4.75 GHz, 3.84 dBi at 4.97 GHz, and 2.64 dBi at 5.19 GHz. Moreover multi‐directional radiation to unidirectional radiation flow at the horizontal plane and vertical plane. A unidirectional radiation patterns based compact antenna utilized for wireless communication applications.

Compact tunable low‐pass to CFBW bandpass switchable filter using concentric resonators

A tunable low-pass to bandpass switchable filter is presented in this study. The proposed structure consists of two concentric resonators. Along with varactors, outer resonator is also loaded with a PIN diode switch. The switching conditions of the PIN diode - OFF lead to a low-pass filter (LPF) and ON lead to a bandpass filter. At the ON condition of the switch, the outer resonator behaves as two resonators which are coupled to each other through two ways - inductively coupled through via hole and capacitively coupled through the varactor loaded between the resonators. The coupling coefficients between the two grounded resonators are controlled using varactors to achieve constant fractional bandwidth (CFBW) tunability. The third CFBW tunable band with bandpass characteristic having three transmission zeros across the passband is achieved using inductively coupled inner resonators. A filter is designed, simulated and fabricated. The response shows a tunable LPF having a tuning range of 0.55-1.4 GHz. One tunable CFBW bandpass response with a tuning range of 0.850-1.25 GHz is achieved with a CFBW of 64%. The third tunable band with bandpass filtering behaviour is achieved with a tunable range of 1.04-1.6 GHz with a CFBW of 13.4%.

Microstrip bandpass filters using triple‐mode circle‐shaped ring resonator with/without stub perturbation

AbstractIn this letter, microstrip bandpass filters (BPFs) using circular triple‐mode ring resonators with/without stub perturbation are designed and analyzed. The first BPF, with a wide passband and a sharp band rejection, is proposed as a prototype, and stubs are attached to two additional BPFs to introduce perturbation. The effects of the stub perturbation are analyzed and evaluated using both the equations and the equivalent circuits presented in this study. The BPF prototype is equipped with both a circular outer resonator, which operates at one wavelength, and a half‐wavelength open‐ended coupled line with a central connected quarter‐wavelength shunt open stub. Each side of the passband has two transmission zeros, which provides the filter with both good selectivity and good out‐band suppression. Based on this BPF prototype, two additional BPFs are designed with stub perturbation for in‐band (BPF 1) and multi‐band (BPF 2) adjustment.

A Rectangular SRR Switched Slotted Microstrip Patch for Frequency Diversity Application

Planar antenna with a specific resonant mode is essential to meet the diversity demand for wireless communication. This paper presents modeling and experimental validation of a microstrip antenna design in which multiple resonant frequencies are excited based on different negative permeability response of the rectangular split ring resonator (SRR). The antenna geometry consists of a slotted patch with split ring resonator loaded between its two arms. The patch was fabricated on FR-substrate of relative permittivity er = 4.4, and has a size of 30.5 mm × 34 mm. In the antenna desing, PIN diodes connect the outer ring and inner ring resonator of the SRR to the adjacent arms of the patch. Under various bias conditions, quad-band resonance was observed at 2.07 GHz, 2.11 GHz, 2.31 GHz, and 2.46 GHz. The measured S11 results are found comparable to the simulated data, and demonstrate proper functioning of the proposed antenna with stable gain and radiation patterns.

Mode-locked self-pumping and squeezing photons model in a nonlinear micro-ring resonator

Photon squeezing and self-pumping within a nonlinear microring GaAsInP/P resonator are modeled and simulated, based on practical, published device parameters. A slowly varying amplitude pulse is input to the system, with a pulse width of 20 ns, a wavelength of 1.55 µm and peak power of 100 mW. The nonlinear effect resulting from the photons within the nonlinear ring resonator can be increased by adding external nonlinear coupling where, in this case, two nonlinear side rings are provided. The Dirac approach is used to generate the squeezed photons within the system. Three different device structures have been investigated, which include an add-drop filter, and a modified add-drop filter with two inner and outer side ring coupling resonators, where the nonlinear four-wave mixing effect is introduced. By using the commercial Opti-wave and MATLAB programs (in which suitable parameters have been chosen), the balance between the creation and annihilation operators can form the squeezed photons, which can be seen at the edge and center rings. The results obtained have shown that the squeezed center photon optical path (between 0 and 1 nm can be obtained) can be useful for interferometry, photon sources, and security code and sensor applications.

Dual-band electromagnetically induced transparency effect in a concentrically coupled asymmetric terahertz metamaterial

We propose a scheme to achieve a dual-band electromagnetically induced transparency (EIT) effect in a planar terahertz metamaterial (MM), comprising an inner circular split ring resonator (CSRR) concentrically coupled to an outer asymmetric two-gap circular split ring resonator (ASRR). The scheme is numerically and theoretically analyzed. The dual-band EIT effect occurs as a result of the near field coupling between the resonant modes of the resonators comprising the MM configuration. It is observed that the dual-band EIT effect in the MM structure could be modulated with an in-plane rotation of the CSRR structure. The dual-band EIT effect is also examined by varying the asymmetry of the ASRR and the size of the inner CSRR. A theoretical model based upon the four-level tripod-system provides an intuitive explanation about the underlying coupling mechanism responsible for the dual-band EIT effect in the proposed MM structure. Our study could be significant in the development of multi-band slow light devices, narrowband absorbers, etc., in the terahertz regime.

Enhancing artificial sum frequency generation from graphene-gold metamolecules.

The enhanced artificial sum frequency generation (SFG) is realized by graphene-gold metamolecules at the mid-infrared without any natural nonlinear material. The unit cell of the proposed metamolecules combines an inner graphene cut-wire meta-atom and an outer gold split-ring resonator meta-atom. In order to achieve high efficiency of the artificial SFG, not only the novel material of graphene with high mobility is used as the constituent material, but also the double resonances at two fundamental frequencies are excited to form an intensive magnetic Lorentz force. Both time domain response and frequency domain response are analyzed numerically. Results show that the SFG efficiency is at least two orders of magnitude larger than that of second-harmonic generation, which involves only a single resonance. The tunability of graphene on the SFG is studied as well. This work will facilitate the engineering of nonlinear metamaterials, whose nonlinear properties can be customized by artificial structuring, in their practical applications.

A Closed-Loop Accelerometer Based on Three Degree-of-Freedom Weakly Coupled Resonator With Self-Elimination of Feedthrough Signal

This paper, for the first time, reports a closed-loop accelerometer based on three degree-of-freedom weakly coupled resonator (WCR). Three resonators are weakly coupled by two bridge-type coupling beams. When acceleration acts on the proof masses, the stiffness perturbation between the two outer resonators will incur the mode localization and cause the shift of amplitude ratio. The accelerometer is tested under open-loop circuit and closed-loop circuit to obtain the frequency responses and transient responses, respectively. The experimental results show that the sensitivity based on the amplitude ratio readout is improved by 348% compared with the 2-DoF WCR accelerometer. The measured signal-to-ratio noise is 124.2 dB and resolution reaches $1.1~\mu \text {g} / \surd \text {Hz}$ , which are significantly improved compared with the previous works. The resolution and signal-to-ratio noise under closed-loop measurement are improved by 46181% and 123.2%, respectively, compared with those under open-loop measurement which demonstrate that the performance of the mode-localized accelerometer can be improved using the closed-loop measurement method.

Compact Left-Handed Meta-Atom for S-, C- and Ku-Band Application

A new compact left-handed meta-atom for S-, C- and Ku-band applications is presented in this paper. The proposed structure provides a wide bandwidth and exhibits left-handed characteristics at 0°, 90°, 180° and 270° (xy-axes) rotations. Besides, the left-handed characteristics and wide bandwidth of 1 × 2, 2 × 2, 3 × 3 and 4 × 4 arrays are also investigated at the above-mentioned rotation angles. In this study, the meta-atom is designed by creating splits at the outer and inner square-shaped ring resonators, and a metal arm is placed at the middle of the inner ring resonator. The arm is also connected to the upper and lower portions of the inner ring resonator, and later, the design appears as an I-shaped split ring resonator. The commercially available, finite integration technique (FIT)-based electromagnetic simulator CST Microwave Studio is used for design and simulation purposes. The measured data comply well with the simulated data of the unit cell for 1 × 2, 2 × 2, 3 × 3 and 4 × 4 arrays at every rotation angle. Owing to the effective medium ratio (EMR) of 8.50 at 0° and 180° rotations, the proposed meta-atom structure is compact in size. Moreover, due to the quality factor of 82, the designed meta-atom is flexible for high-performance antenna, filter and sensor applications. Therefore, the meta-atom integrated antenna shows multi frequency bands with the highest peak gain of 5 dBi, which is used as the long distance radio communication frequency.

Composite left-handed meta-atom for tri-band operation

This paper introduces a compact composite meta-atom for S-, C-, and Ku-band applications, which shows left-handed characteristics at 0°, 90°, 180° and 270° structural rotations. The proposed structure provides wide bandwidth when the operating frequency is between 2.0 and 14.0 GHz. Additionly, the proposed meta-atom is designed by creating splits in the outer and inner square shape ring resonators, and a metal arm is placed at the middle of the inner ring resonator. The arm is also connected with the upper and lower portion of the inner ring resonator, and later, the design appears as an I-shaped split ring resonator. FIT based computer simulation technology electromagnetic simulatortool is utilized for the design, simulation, and numerical analysis. The measured results comply well with the simulated results of the meta-atom for every rotation angle. Owing to the effective medium ratio of 8.50 at 0° and 180° rotational angles and the figure of merit grater than 1.0, the designed meta-atom is compact in size and practically implementable.

Parametric studies on split S-shaped composite meta atom for X-band communication

AbstractThe aim of this paper is to describe a split S-shaped composite meta atom which shows double negative characteristics at resonance frequency. The proposed meta-atom structure exhibits an almost 3.70 GHz bandwidth when the operating frequency from 8 to 14 GHz (X-band). In this study, the ring width, split width, size of substrate material, and the substrate material itself are varying to investigate their effect on the resonance frequencies. Metal strips of the outer resonator are the splits and the inner ring resonator is designed in a way that it forms a split S-shaped structure on the epoxy resin fibre (FR-4) substrate material. The CST Microwave Studio electromagnetic simulator software was used for the design and simulation purposes, and an Agilent N5227A vector network analyser was used for practical measurements.

Terahertz plasmon-induced transparency based on asymmetric dual-disk resonators coupled to a semiconductor InSb waveguide and its biosensor application

An ultracompact double eight-shaped plasmonic structure for the realization of plasmon-induced transparency (PIT) in the terahertz (THz) region has been studied. The device consists of a semiconductor–insulator–semiconductor bus waveguide coupled to the dual-disk resonators. Indium antimonide is employed to excite SPP in the THz region. The transmission characteristics of the proposed device are simulated numerically by the finite-difference time-domain method. In addition, a theoretical analysis based on the coupled-mode theory for transmission features is presented and compared with the numerical results. Results are in good agreement. Also, the dependence of PIT frequency characteristics on the radius of the outer disk is discussed in detail. In addition, by removing one of the outer disk resonators, double-PIT peaks can be observed in the transmission spectrum, and the physical mechanism of the appeared peaks is investigated. Finally, an application of the proposed structure for distinguishing different states of DNA molecules is discussed. Results show that the maximum sensitivity with 654 GHz/RIU−1 could be obtained for a single PIT structure. The frequency shifts equal to 37 and 99 GHz could be observed for the denatured and the hybridized DNA states, respectively.

Inverse E‐shape chiral metamaterial for long distance telecommunication

AbstractIn this article, a chiral metamaterial based on the inverse E‐shape combined with the outer ring resonator that look like an inverse E‐shape structure has been discussed. The designed metamaterial structure is printed on Rogers RT 5880 material and electromagnetic simulator CST Microwave Studio has been used to design, simulation and investigation purposes. The proposed structure shows resonance at C‐band and exhibits 5.14 GHz bandwidth from 4 to 9.14 GHz. The effective medium ratio of the designed metamaterial is 6.83 and shows left handed characteristics at 7.61 GHz. Because of the bandwidth in the major portion of C‐band this proposed chiral metamaterial is applicable for long distance telecommunication applications.

CPW fed miniaturized dual-band short-ended metamaterial antenna using modified split-ring resonator for wireless application

A miniaturized dual-band metamaterial (MTM) antenna has been designed in this article. The designed coplanar waveguide fed antenna has composed of inner split-ring resonator and an outer open ring resonator with rectangular stub. The series parameter of the antenna is used to determine the zeroth order resonance frequency due to short-ended boundary condition. The whole size of proposed structure is 20 × 25.5 mm2. This MTM antenna exhibits dual-band operation at 3.17 GHz (3.1–3.22 GHz) and 5.39 GHz (5.27–5.47 GHz). The proposed MTM structure achieves measured peak gain of 0.71 and 1.89 dB at 3.17 and 5.39 GHz, respectively. The proposed antenna can be used for recent radio communication in form of S-band application and Wi-MAX.

Multiband left handed biaxial meta atom at microwave frequency

Left handed meta atoms are special class materials that characterized by the negative refractive index. In this paper, a left handed biaxial meta-atom is reported that has 5.81 GHz wide bandwidth and applicable for C-, X- and Ku-band applications. The meta atom is developed by an outer and the inner split ring resonator with inverse E-shape metal strips of copper, which are connected with the outer ring resonator that look like a mirror-shape structure. A finite integration technique based CST Microwave Studio is utilized to design, simulation and analysis purposes, where the Agilent N5227A vector network analyzer is utilized for measurement purpose. Measurements show that, the measured and simulated results are well complied together and negative index bandwidth from 3.27 to 6.55 GHz (bandwidth of 3.28 GHz) and 7 to 12.81 GHz (bandwidth of 5.81 GHz) along the z-axis wave propagation. The total dimensions of the designed structure are 0.2λ × 0.2λ × 0.035λ and the effective medium ratio 5, makes the proposed biaxial meta-atom is suitable for practical applications.

A flexible metamaterial absorber with four bands and two resonators

Abstract An efficient approach for achieving more resonance bands with fewer resonators is proposed in this paper. We investigate the theory, design, simulation, fabrication, and performance of a flexible metamaterial perfect absorber (MPA) with two resonators and four resonances located in GHz and THz ranges. The sandwich microstructure of the MPA consists of periodic “回” shaped metal patches on a metasurface, a dielectric of FR4 board on the interlayer, and a continuous copper film on the substrate. The four peaks of absorptivity owing to the coupling effect of the strong LC and surface resonance of the outer ring resonator as well as the strong LC and surface resonance of the inner ring resonator are 93.887%, 99.479%, 98.296%, and 93.035% at 38.165 GHz, 155.48 GHz, 231.71 GHz, and 275.27 GHz, respectively. The influences on absorptivity produced by angles, dimensions, and materials are also studied. The proposed MPA, equipped with strong flexibility, ultrathin thickness, light weight, strong absorption, sparks inspirations in designing the MPA with more resonances and fewer resonators.