Electric Split-ring Resonators Research Articles

Broadband packaging solution in embedded wafer level ball grid array technology for D-band PMCW radar

Abstract A system-in-package for a wideband digital radar, in D-band, requires broadband, high-gain antennas combined with broadband chip-to-package and package-to-printed circuit board (PCB) interconnects. This paper demonstrates a wideband, low-loss quasi-coaxial signal transition, and a novel electric split ring resonator (eSRR)-based antenna-in-package (AiP) with a modified reflector concept, for improved gain, in embedded wafer level ball grid array (eWLB) technology. A complete chip-to-package-to-PCB interconnect is also demonstrated by combining the quasi-coaxial transition with a chip-to-package interconnect. The quasi-coaxial signal transition has the largest impedance bandwidth among ball grid array-based quasi-coaxial signal transitions. For the modified reflector concept, a horn-shaped cavity is micromachined in the PCB substrate and remetallized with aerosol-jet printing, placing the reflector 0.25λ from the antenna. The antenna gain is improved with up to 5.3 dB. The AiP with the horn-shaped reflector is the single element with the highest gain, in eWLB technology, above 100 GHz.

Reversed Cherenkov radiation amplifier with compact structure and high efficiency

Based on the reversed Cherenkov radiation excited in metamaterials, a novel S-band reversed Cherenkov radiation amplifier (RCRA) with two output ports is proposed in this paper. Its metamaterial slow-wave structure (MSWS) consists of a hollow circular waveguide periodically loaded with all-metal double-ridge complementary electric split-ring resonators (CeSRRs). The CeSRR exhibits subwavelength and strong resonance characteristics, which lead to miniaturization and high interaction impedance of the MSWS. The period of the MSWS is optimized using the phase velocity jump technique to further increase the output power and electronic efficiency. The simulation results demonstrate that when the microwave signal of 7.8 W at 2.286 GHz is inputted at port 2, the output power at port 1 is 307 W, and the saturated output power and saturated gain at port 3 are 5.48 kW and 28.47 dB, respectively. Notably, the total electronic efficiency of the RCRA is predicted as 33.84%. The RCRA features high electronic efficiency and miniaturization and may meet special application scenarios that require two output microwave signals at the same frequency.

Tunable terahertz metamaterial using electric split-ring resonator with refractive index sensing characteristic

Tunable terahertz metamaterial using electric split-ring resonator with refractive index sensing characteristic

Characterization of an X-Band Metamaterial Slow Wave Structure for HPM Applications

In this article, we have characterized an X-band complementary electric split-ring resonator (CeSRR) based metamaterial (MTM) slow-wave structure (SWS), suitable for high-efficiency vacuum electron devices (VEDs). The MTM SWS consists of an array of CeSRR and a circular waveguide that propagates below the cut-off frequency of an empty waveguide in the TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{01}$</tex-math> </inline-formula> mode. The surface current distribution has been used to predict the resonance frequency of the CeSRR. An equivalent circuit approach has been used here to obtain its equivalent circuit capacitance and inductance per unit length, which is used further to analyze the dispersion characteristics and interaction impedance of the MTM SWS. The electromagnetic (EM)simulation result showed that the dispersion bandwidth ranges from 9.53 to 9.78 GHz, and the average interaction impedance is greater than 550 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $</tex-math> </inline-formula> . Furthermore, we have designed, EM simulated, and experimentally characterized the proposed X-band MTM SWS. The experimental transmission coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21})$</tex-math> </inline-formula> has been found approximately consistent with the EM simulated values.

Experimental Demonstration of Compact S-Band MW-Level Metamaterial-Inspired Klystron

Metamaterials are artificially constructed subwavelength structures exhibiting unprecedented electromagnetic phenomena. In this letter, an S-band MW-level metamaterial-inspired klystron using all-metal complementary electric split ring resonators (CeSRRs) was realized in the experiment. The CeSRR-loaded interaction structure of the klystron developed here features a miniaturized structure, the volume of which is only about 0.44 of the conventional counterparts. The metamaterial-inspired klystron based on the interaction structure loaded with CeSRRs was designed, fabricated and assembled. Using a pencil beam with parameters of 120 kV/80 A in the hot-test, the klystron delivered the biggest output power of 5.51 MW with gain of 55.6 dB and electronic efficiency of 57.4% at 2.852 GHz. This compact metamaterial-inspired klystron has potential applications in proton therapy facilities, tokamaks for the low-hybrid wave heating, and accelerators.

Metamaterial-Inspired Interaction Structure for MW-Level Klystron at 714 MHz

A metamaterial (MTM)-inspired interaction structure for MW-level klystron at 714 MHz is proposed. The electromagnetic characteristics of MTM-inspired resonant cavities with single-bridge complementary electric split ring resonators (CeSRRs) are studied, and the cold-tested results confirm the feasibility of miniaturizing the resonant cavity. Furthermore, the beam–wave interaction simulation for the interaction structure constructed by MTM-inspired resonant cavities with single-bridge CeSRRs is carried out, demonstrating 2.28 MW of output power at 714 MHz for a 100 kV, 40 A electron beam. The radius and length of the MTM-inspired interaction structure are 1/2 and 2/3 of the conventional counterparts, respectively. The promising performance makes it attractive for future applications such as linacs.

Normal Mode Splitting in THz Fabry–Pérot Microcavity Containing Electric Split-Ring Resonator or Tilted Cut Wire Metamaterial

Normal Mode Splitting in THz Fabry–Pérot Microcavity Containing Electric Split-Ring Resonator or Tilted Cut Wire Metamaterial

Compact reversed Cherenkov radiation oscillator with high efficiency

An all-metal metamaterial slow-wave structure (MSWS), which comprises a hollow circular waveguide loaded by periodically arranged complementary electric split-ring resonators (CeSRRs), is proposed. Due to the CeSRRs with the characteristics of both subwavelength and strong resonance, the MSWS has both compact size and high interaction impedance relative to conventional SWS. Based on the reversed Cherenkov radiation in the MSWS, a compact reversed Cherenkov radiation oscillator (RCRO) with high efficiency is developed. The measured electronic efficiency is 19.54%, and measured output power is 10.16 kW at 2.221 GHz under the conditions that the beam voltage is 26 kV, the beam current is 2.0 A, and axial magnetic flux density is ∼962 G. The experimental results clearly show that the brand-new RCRO can be applied to large-scale scientific facilities, medical imaging, microwave heating, microwave disinfection and sterilization, and so on.

Research on a high-sensitivity asymmetric metamaterial structure and its application as microwave sensor

In this paper, an Asymmetric Electric Split-Ring Resonator (AESRR) metamaterial structure is proposed to explore the interaction between metamaterials and electromagnetic waves with the influence of Fano resonance on electromagnetic properties. With the symmetry of basic electric Split-Ring Resonator (eSRR) being broken, a new Fano resonant peak appears at around 11.575 GHz and this peak is very sensitive to the dielectric environment. Based on the proposed high sensitivity of AESRR, a microwave sensor based on a 13 × 13 arrays of AESRR was designed and verified using printed circuit board (PCB) technology. T-shape channel was integrated to the sensor by grooving in the FR-4 substrate which improved the integration and provided the feasibility of liquids detection. Seven organic liquids and four dielectric substrates are measured by this sensor. The measured results show the transmission frequency shifts from 11.575 to 11.150 GHz as the liquid samples permittivity changes from 1 to 7 and the transmission frequency shifts from 11.575 to 8.260 GHz as the solid substrates permittivity changes from 1 to 9. The results have proven the improved sensitivity and the larger frequency shift ∆f on material under test (MUTs) compared with the conventional reported sensor. The relative permittivity of liquid samples and solid samples can be obtained by establishing approximate models in CST, respectively. Two transcendental equations derived from measured results are proposed to predict the relative permittivity of liquid samples and solids samples. The accuracy and reliability of measured results and predicted results are numerically verified by comparing them with literature values. Thus, the proposed sensor has many advantages, such as low-cost, high-sensitivity, high-robustness, and extensive detecting range, which provided a great potential to be implemented in a lab-on-a-chip sensor system in the future.

Tunable Terahertz Metamaterial with Electromagnetically Induced Transparency Characteristic for Sensing Application.

We present and demonstrate a MEMS-based tunable terahertz metamaterial (TTM) composed of inner triadius and outer electric split-ring resonator (eSRR) structures. With the aim to explore the electromagnetic responses of TTM device, different geometrical parameters are compared and discussed to optimize the suitable TTM design, including the length, radius, and height of TTM device. The height of triadius structure could be changed by using MEMS technique to perform active tunability. TTM shows the polarization-dependent and electromagnetic induced transparency (EIT) characteristics owing to the eSRR configuration. The electromagnetic responses of TTM exhibit tunable characteristics in resonance, polarization-dependent, and electromagnetically induced transparency (EIT). By properly tailoring the length and height of the inner triadius structure and the radius of the outer eSRR structure, the corresponding resonance tuning range reaches 0.32 THz. In addition to the above optical characteristics of TTM, we further investigate its potential application in a refraction index sensor. TTM is exposed on the surrounding ambient with different refraction indexes. The corresponding key sensing performances, such as figure of merit (FOM), sensitivity (S), and quality factor (Q-factor) values, are calculated and discussed, respectively. The calculated sensitivity of TTM is 0.379 THz/RIU, while the average values of Q-factor and FOM are 66.01 and 63.83, respectively. These characteristics indicate that the presented MEMS-based TTM device could be widely used in tunable filters, perfect absorbers, high-efficient environmental sensors, and optical switches applications for THz-wave optoelectronics.

Reconfigurable THz Metamaterial Filter Based on Binary Response for Information Processing System

Light-matter interactions between the metallic and dielectric layers along with the controlling of electromagnetic waves can create a way to develop micro-devices and moderate the functionalities for advanced applications. This study describes a new controlling technique of the plasmatic electron packet based on an electric split-ring resonator (eSRR). All numerical experiments were performed using an advanced CST electromagnetic package. The proposed metamaterial tunneled structure in this study operates using terahertz (THz) frequency spectrum as an efficient digital processing filter. The array combination of the tunneled structure consisted of three individual unit cells. Moreover, the two engineered metallic arms added to the tunneled structure exhibited two peak resonances and one passband frequency region. A large evanescent field was produced to enhance the wave-metal interactions with the presence of a metal-dielectric micro-tunnel. The intensity of the electromagnetic wave-metal interactions was encoded to binary 0 and 1 for information encoding purposes. As a result, the reconfigurable micro-unit cell metamaterial tunneled structure was able to effectively control the electric field and allow electron packets to be digitally encoded for the information processing system.

Enhancement of magnetic field intensity with a left-handed metamaterial tunnel resonator for obstacle sensing

A narrow metal strip inspired by the left-handed metamaterial and sensitive LC resonator structure has been released in this work where the narrow metal strip is presented as a tunnel structure which can enhance electric and magnetic properties. A commercially available electromagnetic simulator CST Microwave Studio is utilized to design and investigate the eSRR (electric split-ring resonator) and tunnelled LC resonator structures. Furthermore, ADS (Advance Design software) is used to determine the scattering parameters of the equivalent circuit. The proposed metamaterial structure is employed as a sensor operating in the C-band (6.88 GHz) of the microwave region, and its sensing properties are tested using glossy paper as an obstacle. The designed metamaterial tunnelling structure exhibits very high sensitivity toward dielectric obstacles at different rotational angles and thus can be potentially used in various sensing applications. The field enhancement effects on sensing application are verified by measured obtained results for eSRR and tunnelled LC resonator structures.

Tunable terahertz metamaterial using electrostatically electric split-ring resonator

A design of electrostatically tunable metamaterial is proposed in the terahertz (THz) frequency range using electric split-ring resonators (eSRR), which shows polarization-dependent and switching characteristics. The eSRR is composed of anchored rectangular split-ring resonators and a movable middle I-shaped metal bar. By exploiting electrostatic force to change the gap within eSRR and the distance of middle I-shaped metal bar, the electromagnetic characteristics of eSRR can be controlled. The electromagnetic response of eSRR shows a single-resonance in transverse electric (TE) mode and keeps as quite stable. In transverse magnetic (TM) mode, the electromagnetic response of eSRR shows dual- and triple-resonance. Such eSRR design is able to be used in lots of applications, such as polarizers, actively tunable filters, frequency-selective detectors, tunable high-efficiency sensors, and multi-functional switches in the THz optoelectronic devices.

Programmable multidigit metamaterial using terahertz electric spilt-ring resonator

We present a design of electric split-ring resonators (eSRR) to explore its electromagnetic coupling effect. eSRR is composed of metal-insulator-metal (MIM) configuration. The equivalent circuit of eSRR has multiple capacitors and inductors to provide multiple resonant frequencies in the THz frequency range. By changing the gaps within eSRR, some resonances can be continuously red-shifted and some resonances can remain stable. These tunable resonances are high Q-factors. The maximum Q-factor is 206. The stable resonances allow the eSRR device in the use of vibrating environment. Furthermore, eSRR possesses optical “on” and “off” states operated in transverse electric (TE) and transverse magnetic (TM) modes. eSRR device shows three resonances at 0.19 THz, 0.43 THz, 0.68 THz. The first resonance at 0.19 THz only appears in TM mode, the second and third resonances only appear in TE mode. This polarized switching function can perform the programmable multidigit characteristic. Therefore, eSRR shows the switching characteristics during the alternating of TM and TE modes. Such optical properties of eSRR with MIM configuration provide the potential possibilities of THz metamaterial to be used in the sensors, programmable devices, radars, and optical communication applications.

Tunable Terahertz Metamaterial Using an Electric Split-Ring Resonator with Polarization-Sensitive Characteristic

We present a tunable terahertz (THz) metamaterial using an electric split-ring resonator (eSRR), which exhibits polarization-sensitive characteristics. The proposed eSRR is composed of double symmetrical semicircles and two central metal bars. By changing the lengths of two metal bars, the electromagnetic responses can be tuned and switched between dual-band and triple-band resonances in transverse magnetic (TM) mode. Furthermore, by moving the bottom metal bar to change the gap between the two metal bars, the first resonance is stable at 0.39 THz, and the second resonance is gradually blue-shifted from 0.83 to 1.33 THz. The tuning range is 0.50 THz. This means that the free spectrum ranges (FSR) could be broadened by 0.50 THz. This proposed device exhibits a dual-/triple-band switch, tunable filter, tunable FSR and polarization-dependent characteristics. It provides an effective approach to perform tunable polarizer, sensor, switch, filter and other optoelectronics in THz-wave applications.

Experimental Testing of a 3-D-Printed Metamaterial Slow Wave Structure for High-Power Microwave Generation

A high-power-microwave (HPM) source consisting of a backward wave oscillator (BWO) based on a metamaterial slow wave structure (MTM SWS) is investigated and tested. The MTM SWS is composed of a circular waveguide with periodic loading of two complementary electric split-ring resonator (CeSRR) disks and was designed at the University of California, Irvine, CA, USA (UCI). This SWS has been studied and simulated to quantify its cold structure properties. Moreover, a BWO using the proposed SWS has been simulated using a particle-in-cell solver to evaluate its performance. In the simulations, this BWO has generated 88-MW peak power in a pulse duration on the order of 15 ns with frequency about 2.9 GHz. This SWS was fabricated using 3-D printing and copper plating technology and was tested using the SINUS-6 pulsed electron beam accelerator at the University of New Mexico, Albuquerque, NM, USA (UNM). An output of 22 MW at 3.0 GHz was observed in experiments.

Terahertz Fano resonances induced by combining metamaterial modes of the same symmetry.

Fano resonances are observed in a composite metamaterial that consists of an electric split ring resonator eSRR and an I-shaped resonator ISR. By adjusting the length of the ISR the degree of asymmetry in the line shape of the composite metamaterial can be controlled and even made to be symmetric. In contrast to other methods to create Fano resonances, the individual modes of the eSRR and ISR have the same symmetry and are not evanescently coupled to each other. The transmission is simulated using the finite difference time domain method and a coupled oscillator model is used to obtain nominal values of the Fano asymmetry factor q. Composite metamaterials and individual eSRR and ISR metamaterials are fabricated, and their transmission is measured with terahertz time-domain spectroscopy.

Characterization of Metamaterial Slow-Wave Structure Loaded With Complementary Electric Split-Ring Resonators

We proposed an all-metal metamaterial slow-wave structure (MSWS) that consists of a circular waveguide periodically loaded with complementary electric split-ring resonators (CeSRRs). We set up an equivalent circuit theoretical model of MSWS and analyzed its high-frequency characteristics. Also, based on the surface current distribution on the CeSRR obtained by using the eigenmode solver in the CST Microwave Studio, a method of calculating the resonant frequency of the CeSRR was proposed. Furthermore, an MSWS with RF coupling port was designed, simulated, fabricated, and experimentally characterized. The dispersion characteristics of MSWS obtained by interpreting the experimental transmission characteristics agreed well with those predicted by theory as well as simulation. Based on the results of simulation and experiment, a concept of “resonance-coupling” was proposed for the passband of MSWS for frequencies below the cutoff frequency of an empty circular waveguide. The role of the slot-line in the CeSRR in influencing the performance of MSWS was also analyzed. The proposed MSWS has wide potential applications in vacuum electron devices, such as backward-wave oscillator and extended interaction klystron.

Multi-functional terahertz metamaterial using symmetrical and asymmetrical electric split-ring resonator

Abstract We present the electromagnetic coupling effects in four types of electric split-ring resonators (eSRRs). These four designs of eSRRs are based on SRR tailored with single-, dual-, triple-, and quad-split, respectively. The near-field electromagnetic coupling responses indicate the resonance caused from the inductive-capacitive (LC) resonance between eSRRs. According to the patterns of eSRR are symmetrical or asymmetrical configurations, these eSRRs exhibit polarization-dependence, polarization-independence, resonant frequency shifting, resonant intensity modulation, and resonant switching characteristics, respectively. To increase the flexibility and applicability of eSRRs, two patterned eSRR layers are designed on elastic substrate for the enhancement of the resonant tunability. The designs of eSRRs open an avenue to a new direction for future optical applications, which offer significant promise in flexible electronics applications. This work provides future tunable THz designs based on flexible actuation mechanism to deform the geometrical dimensions between eSRRs microstructures.

Terahertz electromagnetically-induced transparency of self-complementary meta-molecules on Croatian checkerboard

A terahertz (THz) electromagnetically-induced transparency (EIT) phenomenon is observed from two types of self-complementary meta-molecules (MMs) based on rectangular shaped electric split-ring resonators (eSRR) on Croatian checkerboard. Each MM contains a couple of identical size eSRRs and a couple of structural inversed eSRRs twisted π/2 in checkerboard pattern. In the first type of MM (type-I), the gap is in the middle line of eSRR. In the second type of MM (type-II), the gap is on the two arms of eSRR. Both types of MMs exhibit EIT effect. A maximum 20 ps group delay is observed at the transparency window of 0.63 THz in type-I MM; while a maximum 6.0 ps group delay is observed at the transparent window of 0.60 THz in type-II MM. The distribution of surface currents and electrical energy reveals that only CeSRR contribute to the transparency window as well as the side-modes in type-I MM, where the current leakage via contact point contributes to the low-frequency side-mode, and the coupled local inductive-capacitive (LC) oscillation in CeSRRs contributes to the high-frequency side-mode. In type-II MM, however, the localized dipolar oscillator of CeSRR contributes to the low-frequency side-mode; while the hybridization of dipole oscillation on eSRR and LC resonance on CeSRR contributes to the high-frequency side-modes. Our experimental findings manifest a new approach to develop THz slow-light devices.