Series Gap Research Articles

Moore Curve Fractal‐Shaped Miniaturized Complementary Spiral Resonator

ABSTRACTIn this article, a novel design of complementary spiral resonators as miniaturized metamaterial particles based on Moore curve fractal shape is presented. The proposed design of metamaterial unit cell is investigated using a microstrip line loaded with series gap discontinuities and implementing fractal shape complementary spiral resonator in ground plane that behaves as a composite right left hand transmission line. It is observed that Moore curve fractal‐shaped spiral resonator provides 49% size reduction as compared to conventional split ring resonators. An equivalent lumped element circuit model of the proposed composite right left handed transmission line is developed to analyze the proposed topology. A close agreement between electromagnetic simulation, circuit simulation, and measurement is obtained. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1950–1954, 2013

Electric Split-Ring Resonator Based on Double-Sided Parallel-Strip Line

A new electric split-ring resonator (ESRR) specialized for the double-sided parallel-strip line (DSPSL) is proposed. Adding a DSPSL swap to a split-ring resonator (SRR), its magnetic response becomes electrical, which is explained by even- and odd-mode analysis and resonant current distribution. Loading in a line with a series gap, it behaves similarly to the previously well-studied complementary SRR. ESRR may be useful in the design of novel DSPSL-based antennas and microwave components.

A new multi-gap spark switch connected with frequency-dependent network for EHV overvoltage protection applications

With the development of modern power systems, the overvoltage protection and high current fast bypass of important electric equipment or parts in EHV grids put forward a great demand for high reliable fast bypass techniques. The triggered spark gaps now used in H.V. grids are still confronted with many difficulties. This paper proposes a conceptual design of a new multi-gap spark switch connected with a frequency-dependent network. The device is composed of series gaps and a chain RC network for producing frequency-dependent voltage distribution along the gaps. An even voltage distribution under power frequency operating voltage while an extremely uneven voltage distribution under trigger impulse can be achieved by proper parameter setting. The even voltage distribution enables the multi-gap spark switch to withstand much higher voltage than that in operation, thus avoiding false firing. On the contrary, extremely uneven voltage distribution could initiate cascade discharge at low amplitude impulse, insuring reliable triggering. The working principle of the new multi-gap spark switch differs considerably from that of the current spark gaps in H.V. and pulsed power systems. It has high reliability and no dead zone of trigger control, which can be sufficiently used as a high speed bypass switch for overvoltage protection applications in EHV grids. The conceptual design of the multi-spark gap switch, simulation of the frequency-dependent voltage distribution, cascade discharge of the spark gaps as well as the experimental performance verification on the prototype are presented in this paper.

Analysis of New Type Repulsion Mechanism Performance

Using circuit method to analysis equations of circuit and motion of coil-coil Mechanism, numerical simulations were also made. Simple method of experimental verification was proposed. The numerical results show influence of circuit parameter and benefits of multiple series gaps.

Near real-time disturbance detection using satellite image time series

Near real-time monitoring of ecosystem disturbances is critical for rapidly assessing and addressing impacts on carbon dynamics, biodiversity, and socio-ecological processes. Satellite remote sensing enables cost-effective and accurate monitoring at frequent time steps over large areas. Yet, generic methods to detect disturbances within newly captured satellite images are lacking. We propose a multi-purpose time-series-based disturbance detection approach that identifies and models stable historical variation to enable change detection within newly acquired data. Satellite image time series of vegetation greenness provide a global record of terrestrial vegetation productivity over the past decades. Here, we assess and demonstrate the method by applying it to (1) simulated time series of vegetation greenness data from satellite data, (2) real-world satellite greenness image time series between February 2000 and July 2011 covering Somalia to detect drought-related vegetation disturbances. First, simulation results illustrate that disturbances are successfully detected in near real-time while being robust to seasonality and noise. Second, major drought-related disturbance corresponding with most drought-stressed regions in Somalia are detected from mid-2010 onwards. The method can analyse in-situ or satellite data time series of biophysical indicators from local to global scale since it is fast, does not depend on thresholds and does not require time series gap filling. While the data and methods used are appropriate for proof-of-concept development of global scale disturbance monitoring, specific applications (e.g., drought or deforestation monitoring) mandate integration within an operational monitoring framework (e.g., http://www.fews.net/).

Influence of number of split rings on the leaky radiation of a metamaterial transmission line based on complementary split ring resonators

This article discusses the influence of the number of concentric split rings on the radiation performances of a leaky wave antenna (LWA) created by a microstrip transmission line periodically loaded by series gaps and complementary split ring resonators (CSRRs) in its ground plane.The addition of a second concentric split ring in the CSRR structure strongly modifies the distribution of electric and magnetic currents in each cell of the periodic LWA structure. As a consequence, the far-field radiation pattern of the cell shows a zero in the broadside direction, which is responsible for an apparent split of the LWA radiation pattern at the upper frequency of the backward scanning range, predicted by full-wave simulations and validated by measurements in anechoic chamber.

Multimode Propagation and Complex Waves in CSRR-Based Transmission-Line Metamaterials

Transmission-line metamaterials based on complementary split-ring resonators (CSRRs) are shown to support forward, backward, electroinductive, and complex waves. Two CSRR-based lines are considered: 1) stopband microstrip lines simply loaded with CSRRs, and 2) passband microstrip lines loaded with CSRRs and series gaps. The effects of interresonator coupling on bandwidth enhancement are analyzed on the basis of Bloch mode theory by considering the lumped-element equivalent 4-port circuit model of the unit cell. All the propagation modes are captured by the proposed multiterminal Bloch mode theory, from an eigenmode analysis. The results are validated through a commercial eigenmode solver and supported by experimental data.

Composite right/left-handed transmission line based on complementary single-split ring resonator pair and compact power dividers application using fractal geometry

A new resonant-type composite right/left-handed transmission line (CRLH TL) is proposed based on the combination of a complementary single-split ring resonator pair (CSSRRP) etched on the ground plane and a series gap embedded in the conductor strip of a microstrip line. The CSSRRP, which is composed of two identical complementary single-split ring resonators (CSSRR) with face-to-face splits, demonstrates negative permittivity. An equivalent circuit model is presented and studied in depth through the Bloch theory and finally validated by the simulated full-wave S-parameters. The balanced condition for novel CRLH TL is also derived. Moreover, the negative refractive index and backward wave propagation are confirmed by the effective constitutive parameters. It is proved that the zero-degree phase-shift CRLH TL exhibits a significantly lower resonant frequency by constructing the CSSRRP as Koch curves of different iteration order (K-CSSRRP). To demonstrate the applicability, two compact prototype device examples are provided, these being a three-way fork power divider and a four-way series power divider. The three-way divider achieves a 74.2% size reduction and displays comparable performance relative to its conventional counterpart, whereas the four-way divider obtains a 56% bandwidth enhancement and a 48% size reduction in comparison with a conventional one using a one-wavelength meandered transmission line.

Electrical discharge behavior of micro-gaps

Electrical discharge characteristics of micro-gaps, ranging from 50 to 1000 μm in air are investigated under ac, dc and high frequency (5 kHz) by using blade electrodes that possess a high aspect ratio: 20 μm edge thickness and 15 mm length. Three micro-gap configurations (single, series and parallel) are studied for the breakdown strength and partial discharge characteristics. An exponential increase in the breakdown strength with air gaps below 1000 μm is observed. The finite element models revealed that the electric stress at 1000 μm is about 4 times the applied field. The electric stress magnitude is found to reduce as a function of air gap up to about 100 μm where the actual field is equal to the applied field. The breakdown strength of the series gap configuration is significantly higher than that of the parallel configuration. The partial discharge activities are observed in the series configuration whilst the same is absent in the parallel configuration.

Design and Analysis of a Tunable Bandpass Filter Employing RF MEMS Capacitors

This letter presents an RF microelectromechanical systems (MEMS) tunable bandpass filter with a tuning range of 30%. An analytical process of designing a bandpass filter is also presented by using MEMS switch, series gap, and etched structure in coplanar waveguide (CPW). The designed structure of the MEMS switch and CPW is used to get a wide tuning range of the filter. The fabricated filter performances show an acceptable agreement between the measured results and the simulation results with a center frequency from 10 to 13.5 GHz.

Recent Advances in Metamaterial Transmission Lines Based on Split Rings

This paper is focused on metamaterial transmission lines based on split rings. Specifically, the considered lines are those based on the hybrid approach, where complementary split ring resonators (CSRRs) are combined with series gaps and shunt inductive stubs, and those implemented by loading a host line with open split ring resonators (OSRRs) and open complementary split ring resonators (OCSRRs). The dispersion characteristics and the characteristic impedance of such lines, essential for design purposes, are analyzed to the light of the lumped element equivalent circuit models of the lines. Finally, it is shown that hybrid lines are useful for the design of power splitters with filtering capability, and OSRR/OCSRR-loaded lines are of interest for the design of wideband bandpass filters. The achieved performances are satisfactory and device dimensions small.

A Controllable Bandwidth Filter Using Varactor-Loaded Metamaterial-Inspired Transmission Lines

This letter presents a tunable bandwidth bandpass filter based on varactor-loaded metamaterial coplanar waveguide (CPW) lines. The CPW lines are based on series gaps and split-ring resonators. The varactors are reverse-biased semiconductor diodes connected between both sides of each series gap. This configuration, directly inspired from the so-called metamaterial technology, takes advantage of the high dispersion of the loaded transmission line. Therefore, strong permittivity and permeability responses induced by means of the resonators are obtained. A single varactor-loaded transmission line is first analyzed. Then, a third-order tunable filter with fractional bandwidth tuning range from 5.8% to 21.5% is experimentally assessed. The proposed filters can be used in several practical applications such as multichannel wireless and satellite communication systems, where reconfigurable devices are often required.

Novel Co-planar Waveguide (CPW)-Fed Small Antenna with Circular Polarization

A planar circularly-polarized (CP) small antenna is proposed. To obtain a low profile configuration, a co-planar waveguide (CPW) structure is employed. Circular polarization is achieved using a curved stub that generates current distribution in a direction orthogonal to the current distribution from the patch. Using meander lines and a series gap capacitance, a 70% size reduction is achieved compared to a half-wavelength resonant antenna. To the best of the authors' knowledge, the proposed antenna is the smallest CP antenna using CPW technology. The measured 3dB axial ratio bandwidth is 8.3% from 3.83GHz to 4.16GHz, and a 1.6dBic gain and 89% efficiency are achieved.

Metamaterials‐inspired technologies applied to ultra high‐frequency filtering structures

AbstractIn this letter, the design and comparative study of metamaterial‐inspired bandpass filters operating at G‐band (150 GHz) is presented. To this aim, filters based on split ring resonators (SRRs) and complementary SRRs are studied and compared on a scale compliant with MMIC technology. Technological issues impose severe constraints to the design of this type of devices. Specifically, the filter selectivity concern is addressed as a trade‐off between the acceptable insertion losses in the transmitted band and the achievable bandwidth. The addition of series gaps to previous unit cell configurations and suspended membrane structures are introduced to overcome these limitations, thus presenting improved upper band edges and rejection characteristics. In this context, the extension of metamaterial‐based filtering structures to higher frequencies and notably at millimeter waves is still lacking. Therefore, we present here the first contribution in this field by addressing the possibility to fabricate an ultra narrow bandpass filter for space applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1868–1872, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25300

Synthesis of compact and highly selective filters via metamaterial-inspired coplanar waveguide line technologies

In this study, two split ring resonator-based coplanar waveguide cells operating in C-band are studied. Particularly, the lines have been loaded with double shunt strips or series gaps. The use of double strips allows controlling the electric plasma frequency, and at the same time permits one to have a good excitation of the resonators. On the other hand, the employment of double series gaps provides a right-handed behaviour, contrary to conventional metamaterial structures for which a backward propagation is obtained. Several parametric studies show the possibility to significantly increase the selectivity, and in particular the possibility to have an effective control on the out-of-band rejection levels by means of the loading elements characteristics. In a second stage, enhanced out-of-band rejection properties have been obtained by the use of cascaded basic cells and rigorous optimization processes. As a consequence, the proposed filters can be foreseen for practical applications relying on the trade-off found between selectivity, insertion losses and out-of-band rejection.

Specific Considerations on IEC Standardization of Externally Gapped Line Surge Arresters (EGLAs)

The application of externally gapped line surge arresters (EGLAs), which have been developed and established in Japan, is now expanding into many countries. Therefore, the maintenance team 4 (MT4) in the international electrotechnical commission (IEC) technical committee 37 (TC37) for surge arresters advances the standardization works to specify the minimum criteria for requirements and testing methods of EGLAs. EGLAs are effective lightning protection of overhead transmission lines, and have unique required performances originated from the external series gap. The unique required performances of EGLA are insulation coordination performance of EGLA sparkover voltage for lightning overvoltage with the insulator assembly to be protected, withstand voltage performance for switching surge overvoltage and TOV, and follow current interruption performance.This paper discusses the specific issues to be considered for the standardization, such as classification of lightning discharge current rating and a test procedure for follow current interruption performance, based on the Japanese technology through more than twenty years of experience with a large numbers of EGLAs in 22kV to 500kV systems.

Series Gap Type 피뢰기의 뇌임펄스 동작책무 및 온도의존성에 관한 연구

This paper describes lightning impulse operating duty performance and temperature dependence of series gap type for transmission line arresters. The ageing parameters of lightning arresters are impulse current, moisture ingress, temperature ageing and so on. Especially it is important to estimate the change of electrical characteristics by lightning impulse current. In the discharge withstand test, total energy applied to the ZnO arrester each time is 4/10 , 30 kA. and in the operating duty test, the arrester has passed the test if thermal stability is achieved, if the residual voltage measured before and after the test is not changed by more than 5 %, and after the test reveals no evidence of puncture, flashover or cracking of the ZnO block. As a results, the residual voltage was in the range of 17.220.3 kV and ZnO block bear up against at 2 shot of series impulse current of 30 kA. Also it was so excellent that the mechanical destruction does not occur at the 2 groups of 5 impulses current of 2/20 10 kA. According to the tests, it is thought that the ZnO arrester shows good stability with impulse current test. and it was found that the ambient temperature is increased resistive leakage current was increased in the range 47.3167.4 .

Minimum Distance of Lightning Protection Between Insulator String and Line Surge Arrester in Parallel

The line surge arrester can effectively improve the lightning protection performances of transmission lines by eliminating the insulator flashover. If the line arrester is very close to the insulator string in parallel, the lightning discharging would take place in the gap between the upper discharging ring of the line arrester and the bottom grading ring of the insulator string, there is no discharging in the series gap of the line arrester. Sometimes, the insulator string would have a flashover, the line surge arrester cannot provide protection for the insulator string. This so-called ldquotransverse dischargerdquo phenomenon is caused by the proximity effect of the discharging ring of the line arrester. This phenomenon is explained in this paper, and the transverse discharge phenomenon is simulated in high voltage laboratory. The demanded minimum distances between the 110-kV and 220-kV line arrester and insulator string protected are proposed from experimental results.

Microstrip bandpass filters based on zeroth-order resonators with complementary split ring resonators

The zeroth-order resonant (ZOR) properties of the left-handed material (LHM) unit cells composed of complementary split ring resonators and series gaps are analysed. The method to determine the resonant frequency and susceptance slope parameter is proposed. A bandpass filter (BPF) is designed by connecting the ZORs with admittance inverters. Experimental verification is provided and a good agreement has been found between the simulation and measurement. Compared with the bandpass structure fabricated by simply cascading the same amount of LHM unit cells, the proposed BPF has much better selectivity, more symmetrical responses and controllable bandwidth.

DESIGN OF NARROWBAND BANDPASS FILTER ON COPLANAR WAVEGUIDE USING SPIRAL SLOTS

A configuration for a miniaturized band-pass filter on a coplanar waveguide (CPW) is proposed in this communication. Parametric studies conducted for various geometrical parameters suggest that the frequency response of the filter is strongly related to that of the spiral slots. A a series gap on the center conductor of the CPW changes the overall response of the device. For validation of these concepts, a bandpass filter operating at about 3.5 GHz has been designed, fabricated and tested. Experimental results show good agreement with electromagnetic simulations. The design takes up an area of approximately 0.1λ0 × 0.1λ0.