EM Measurements Research Articles

Wideband absorber at X‐band adopting trumpet‐shaped structures

A wideband single-layer absorber at X-band adopting trumpet structures is presented. One unit of the proposed absorber is composed of a trumpet-shaped resonator loading four chip resistors, a metallic backplane and an FR-4 (e r = 4.4-j0.02) substrate between them. The absorption is 99% at 10.9 GHz. The full width at half maximum is 95% at 12.7 GHz (6.7–18.7 GHz). The 90% absorption bandwidth is 65% at 12.75 GHz (8.6–16.9 GHz). The size of the unit cell is 5.6 × 5.6 × 2.4 mm3. The proposed absorber is almost insensitive to polarisations of incident waves due to the symmetry of the structure. The results of EM simulation and measurements are in good agreement.

Input Match and Output Balance Improvement of Marchand Balun With Connecting Line

A novel method allowing for improvement of input match and output balance of Marchand balun with connecting line has been presented. The proposed compensation technique together with the ideal Marchand balun design formulas allow for achieving an arbitrary impedance transformation ratio even for the circuit having a long connecting line. The theoretical analysis has been verified by EM simulations and measurements of a Marchand balun composed of 3 dB coupled-line sections and 30° transmission line operating at the center frequency f 0 = 1.15 GHz and terminated at input and outputs with 50 Ω and 100 Ω, respectively.

Applying airborne electromagnetics in 3D stochastic geohydrological modelling for determining groundwater protection

ABSTRACTAirborne electromagnetic (AEM) measurements provide information regarding the electrical properties of the subsurface for large spatial coverage in a limited time. In mapping and modelling for geological and geohydrological purposes, electrical properties (e.g. resistivity) need to be converted to relevant parameters, like lithology. Helicopter‐borne frequency‐domain EM measurements from an area in the Netherlands were combined with borehole data to create a 3D model of two contrasting lithologies (sand and clay) that served as proxy for assessing the vulnerability of the aquifer to surface contamination. By comparing the lithology found in boreholes with the resistivity derived from AEM at that location, a probabilistic relationship between these two variables was determined. This relationship was used to convert the AEM resistivity models into a 3D model of clay probability. Using geostatistical Monte Carlo simulations, the boreholes (hard data) and the probability of clay from the AEM resistivity models (soft data) were combined. AEM improved the 3D model substantially, compared to using only borehole data. An independent validation dataset verified the improvement of the 3D model using AEM data. Areas with a high probability of clay occurrence could be distinguished and a clay thickness map with uncertainty (standard deviation) was calculated. Using a simple groundwater model, the capability of the clay to protect the underlying aquifer from contamination was quantified. This resulted in the delineation of distinct areas that are well protected due to the large travel time for infiltrating water from the surface to the aquifer.

Geophysical investigation in the Temple of Poseidon at Cape Sounio, Attica, Greece

G. Apostolopoulos, K. Leontarakis and C. Orfanos present an integrated geophysical investigation of the Temple that has been done with EM, GPR and ERT measurements. The cliff at Cape Sounion is the spot from where Aegeus, King of Athens, leapt to his death, thus giving his name to the Aegean Sea. The original Archaic Period Temple of Poseidon on the site, which was built of tufa, was destroyed in 480 BC by Persian troops during Shahanshah Xerxes I’s invasion of Greece. After the Athenians defeated Xerxes in the naval Battle of Salamis, the later Temple at Sounion, whose columns still stand today (Figure 1), was probably built in ca. 440 BC. This was during the ascendancy of Athenian statesman Pericles, who also rebuilt the Parthenon in Athens. The Ministry of Culture’s 2nd Ephorate of Prehistoric and Classical Antiquities has set up a project for geophysical investigation to detect whatever constructions or material may exist under the temple (possible relics of the previous temple). This project has been undertaken by the Applied Geophysics Laboratory of the School of Mining and Metallurgical Engineering at the National Technical University of Athens.

MEASURING TIDES AND BINARY PARAMETERS FROM GRAVITATIONAL WAVE DATA AND ECLIPSING TIMINGS OF DETACHED WHITE DWARF BINARIES

The discovery of the most compact detached white dwarf (WD) binary SDSS J065133.33+284423.3 has been discussed in terms of probing the tidal effects in white dwarfs. This system is also a verification source for the space-based gravitational wave (GW) detector, evolved Laser Interferometer Space Antenna (eLISA) which will observe short-period compact Galactic binaries with $P_{orb}\lesssim 5$ hrs. We address the prospects of doing tidal studies using eLISA binaries by showing the fractional uncertainties in the orbital decay rate and the rate of that decay, $\dot{f}, \ddot{f}$ expected from both the GW and EM data for some of the high-$f$ binaries. We find that $\dot{f}$ and $\ddot{f}$ can be measured using GW data only for the most massive WD binaries observed at high-frequencies. Form timing the eclipses for $\sim 10$ years, we find that $\dot{f}$ can be known to $\sim 0.1% $ for J0651. We find that from GW data alone, measuring the effects of tides in binaries is (almost) impossible. We also investigate the improvement in the knowledge of the binary parameters by combining GW amplitude and inclination with EM data with and without $\dot{f}$. In our previous work we found that EM data on distance constrained 2-$\sigma$ uncertainty in chirp mass to $15-25%$ whereas adding $\dot{f}$ reduces it to $0.11%$. EM data on $\dot{f}$ also constrains 2-$\sigma$ uncertainty in distance to $35%-19%$. EM data on primary mass constrains the secondary mass $m_2$ to factors of 2 to $\sim40%$ whereas adding $\dot{f}$ reduces this to $25%$. And finally using single-line spectroscopic constrains 2-$\sigma$ uncertainties in both the $m_2, d$ to factors of 2 to $\sim 40%$. Adding EM data on $\dot{f}$ reduces these 2-$\sigma$ uncertainties to $\leq 25%$ and $6%-19%$ respectively. Thus we find that EM measurements of $\dot{f}$ and radial velocity will be valuable in constraining binary parameters.

Testing of Josephson Spectrometer with Waveguide Coupling

One of the challenges in public security is the quick and reliable identification of threat liquids in bottles, when vapour analysis is not possible. Recently, we demonstrated that it is possible to rapidly identify liquids by EM measurements of their dielectric functions in the sub-THz range with a high-Tc Josephson spectrometer. Following this approach, we have developed a Josephson spectrometer with a new radiation coupling system, based on dielectric waveguides. In this paper, we present the results of spectroscopic measurements on liquid samples of various purities including 30% H2O2/H2O, performed using our Josephson spectrometer with waveguide coupling. Also, the signal and noise characteristics of a classical Josephson detector used in our liquid identifier were numerically simulated and the power dynamic range was estimated for a wide spread of junction parameters.

Mismatch Between the Resting Membrane Potential and the Voltage at Maximum Amplification in Outer Hair Cells (OHCS) of Mammalian Cochlea

OHCs amplify sound by an electromechanical mechanism. Sound-induced vibrations cause OHC membrane potential (E) to change from its resting voltage (Em) to a new value (Em+dE). The induced receptor potential (dE) initiates charge movement (Q) and force production to counteract viscous losses incurred by the traveling wave. Q exhibits a sigmoidal function with E and because it is most sensitive to dE at the midpoint (Vm), Em should equal Vm to ensure maximum amplification. Vm was measured with isolated OHCs extracted from guinea pig with whole-cell patch clamp under constant intracellular pressure in presence of KCNQ4 blocker XE991 (≥ 30 μM) to ensure robust voltage clamp (conductance < 1.5 nS at Vm). After correcting for physiological conditions the results show Vm is coincident with in vitro measurements of Em (Neuron 2011 70: 1143), but a mismatch of 40 mV is apparent when comparing with in vivo measurements of Em made at basal (J. Physiol. 1987 383: 551 and Proc. R. Soc. Lond. B. 1992 247: 97) or apical (J. Neuroscience 1985 5: 1591) regions of cochlea. Results also reveal variation of Vm across the cochlea as a function of a non-uniform charge density of the lateral wall (σ); when σ is uniform Vm is constant, and when σ varies inversely with area of lateral wall (ALW)Vm increases monotonically from a hyperpolarized value at the high frequency region of cochlea to a depolarized value at low frequency region. Although the relationship between Vm and σ is satisfying as it reflects the electric field, the disparity between in vitro and in vivo measurements highlights the need to reconcile them to ascertain the operating position of the amplifier.

Compact UHF 9th-Order Bandpass Filter with Sharp Skirt by Cascaded-Triplet CRLH-ZOR

We propose a compact high-order(9th) UHF bandpass filter comprising the composite right-handed and left-handed(CRLH) zeroth-order resonators(ZORs) in the form of the three cascadedtriplets(CTs) newly applied to the ZOR filter which results in very steep skirt. The method is verified by circuit and EM simulations and measurement with metamaterial properties.

The quantitative advantages of using B-field sensors in time-domain EM measurement for mineral exploration and unexploded ordnance search

The use of simple models for decay of conductive targets under conductive overburden and for the decay of magnetically permeable conductive steel objects allows quantitative consideration of the advantages of the use of magnetic-field detectors in time-domain electromagnetic (TEM) measurements, or more generally, the advantage of step response over impulse response TEM systems. We identified eight advantages of the step response versus impulse-response systems. The first two advantages relate to the inductive limit (early time) decay behavior, in which a target response amplitude is largely dependent on geometrical rather than conductivity parameters. Five further advantages occur when measuring response of a target in a conductive host or under conductive overburden; the maximum target-to-overburden response occurs 25%–30% earlier in time, the earliest target detection time occurs a factor 2–4 earlier, and the amplitude advantage of target-to-overburden response is a factor in the range of 1–10 for the step versus impulse-response systems, respectively. These advantages agree quantitatively with field observations on a chalcopyrite orebody under conductive cover. We used a model response for a conductive permeable sphere to derive mathematically consistent approximations for the power-law and exponential decay behaviors for step and impulse responses of metal objects, from which the onset of late-time exponential decay of EM responses of unexploded ordnance occurs about a factor of two earlier in time for the step response. This earlier-time transition together with the higher signal-to-noise ratio available from the step-response measurement makes measurement of the fundamental time-constant of unexploded ordnance (UXO) possible for medium and large UXO where the time constant is in the range of tens of milliseconds. This time-constant thus becomes accessible as an additional parameter for UXO characterization and discrimination.

Letter-shaped microstrip ground slots

This paper proposes a systematic approach for designing and modeling letter-shaped microstrip ground slots. Twenty-three structures are investigated. For each one, a geometrical circuit model is developed. Interestingly, 21 letters have unique s-parameters (electromagnetic [EM] print). Results are confirmed by EM simulations and measurements. These results may pave the way to new applications, e.g. microwave character recognition, letter-based microwave circuits, or new radio frequency identification (RFID) structures

Reply to “Three-dimensional galvanic distortion of three-dimensional regional conductivity structures: Comment on Three-dimensional joint inversion for magnetotelluric resistivity and static shift distributions in complex media” by A. G. Jones

[1] Static shift and spatial aliasing are the bane of magnetotelluric exploration and Jones [2011] provides two useful comments on the issue of accounting for static shift in 3-D inversion, one concerning Sasaki and Meju [2006] and another concerning Zhdanov et al. [2011]. This is followed by an overview of well-known impedance tensor relationships in magnetotelluric data analysis (equations (1)–(9)), on which he based his comments. The main tenet of his discussion is that in a fully 3-D situation, all the elements of the impedance tensor (Zxy, Zxx, Zyx and Zyy) are nonzero and should be considered in any 3-D inversion approach. In practice, for geological interpretation, we commonly define apparent resistivities and phases using Zxy and Zyx, which permit an assessment of whether they are influenced by galvanic distortion (i.e., static shift) from their expected background levels especially by comparison with data from coincident alternative EM soundings which are less affected by small size near-surface heterogeneities such as the transient EM method [e.g., Sternberg et al., 1988; Meju, 1996, 2005]. There are other ways of determining and removing static shifts using only MT data as mentioned by Jones [2011] and these have their strengths and weaknesses. Whatever the adopted approach, for a long time, static shift is commonly identified on apparent resistivity sounding curves while the phase curves are assumed to be unaffected, even though Jones [2011] use physical arguments to suggest that phase mixing rather than geometric amplitude shifts obtains in complex 3-D environments at all spatial scales. Regional galvanic distortions are fully accounted for in 3-D inversions within the accuracy of the forward modeling unless the model discretization is inadequate. However, there is one type of galvanic distortions that cannot be handled in the conventional 3-D MT inversion. That is the distortions due to near-surface inhomogeneities located just below the receiver sites, because such inhomogeneities cannot be accurately represented by the given model discretization in the inversion. These include random conductive weathered patches (model A of Sasaki and Meju [2006]), elongate conductors such ancient stream channels (model B of Sasaki and Meju [2006]) and covered waste dump sites, all common in real life. The Sasaki and Meju [2006] approach to removing static shifts was introduced to tackle this type of galvanic distortions, assuming that the distortions can be represented by static shifts (and it was shown in Figures 3 and 5 that the phases are unaffected for model A and are partially affected at higher frequencies for model B). [3] It is important to stress that the purpose of inversion is to find a model that explains the observed data quantitatively. In the first experiment in our paper (model A), we show that joint estimation of resistivities and static shifts improve the inversion image in the presence of surficial inhomogeneities that are too small to be recovered by the conventional 3-D inversion. In the next experiment (model B), we show that our method is still effective in recovering resistivity distribution even if the effects of near-surface structure include frequency-dependent shifts. The necessary constraint, which serves as a form of a priori information, is provided by the assumption of a Gaussian or a zero-sum distribution of static shifts (justified by numerous alternative EM field measurements) in our inverse problem formulation (i.e., the β2S term in equation (1) above), not by the assumption that the MT phase is unaffected by static shift. While we put emphasis on static shifts arising from the weathered surficial layer, deeper structures may yield static effects if the period range starts at, say, 10 s. This is just a matter of the spatial scale of operation. Our 3-D algorithm is full domain and can handle such a situation. It should also be borne in mind that the mathematical representations of the complex subsurface process on which Jones [2011] based his comments are necessarily simple approximations of physical reality.

Three-dimensional galvanic distortion of three-dimensional regional conductivity structures: Comment on “Three-dimensional joint inversion for magnetotelluric resistivity and static shift distributions in complex media” by Yutaka Sasaki and Max A. Meju

[1] Distortion of natural time variations of the electric and magnetic fields induced by external magnetic sources by local, near-surface inhomogeneities has been the bane of the magnetotelluric method (MT). These distortions are caused by galvanic charges on conductivity gradients at the boundaries of near-surface inhomogeneities that are below the resolution of the MT experiment. They often dominate over the inductive response of deeper structures, leading to erroneous interpretations if not appropriately considered. Indeed, one can argue that MT has become a generally robust and useful geological mapping tool only with the advent of distortion recognition, appraisal and removal methods. On land, these distortions are usually low in regions of laterally uniform surficial layers, such as sedimentary basin environments, and extreme in highly heterogeneous resistive environments, such as on Precambrian regions. On the seafloor they are usually extreme. They are always present and affect the MT responses derived from the observed fields to a greater or lesser extent, and must be considered in any analyses and subsequent interpretations. [2] Distortion methods for MT data responding to onedimensional (1-D) and two-dimensional (2-D) structures (reviewed below) have been advanced and are usually quite effective, except in the situations of very severe distortion. For data from three-dimensional (3-D) structures however, the problems caused by these galvanic charges becomes far more complex and require innovative analysis and treatment. [3] In their paper, Sasaki and Meju [2006] describe their approach to 3-D inversion of MT data for 3-D structure taking galvanic distortion, which they characterize and simplify as static shifts, into account. Their paper is an update on prior work by Sasaki [2004] with the same approach. The assumption made by the authors is that the magnitudes of the observed off-diagonal elements of the impedance tensor can be described as geometrically shifted versions of their true values, namely in their terms

Measurement of the membrane potential in small cells using patch clamp methods

The resting membrane potential, Em, of mammalian cells is a fundamental physiological parameter. Even small changes in Em can modulate excitability, contractility and rates of cell migration. At present accurate, reproducible measurements of Em and determination of its ionic basis remain significant challenges when patch clamp methods are applied to small cells. In this study, a mathematical model has been developed which incorporates many of the main biophysical principles which govern recordings of the resting potential of 'small cells'. Such a prototypical cell (approx. capacitance, 6pF; input resistance 5 GΩ) is representative of neonatal cardiac myocytes, and other cells in the cardiovascular system (endothelium, fibroblasts) and small cells in other tissues, e.g. bone (osteoclasts) articular joints (chondrocytes) and the pancreas (β cells). Two common experimental conditions have been examined: (1) when the background K+ conductance is linear; and (2) when this K+ conductance is highly nonlinear and shows pronounced inward rectification. In the case of a linear K+ conductance, the presence of a "leakage" current through the seal resistance between the cell membrane and the patch pipette always depolarizes Em. Our calculations confirm that accurate characterization of Em is possible when the seal resistance is at least 5 times larger than the input resistance of the targeted cell. Measurement of Em under conditions in which the main background current includes a markedly nonlinear K+ conductance (due to inward rectification) yields complex and somewhat counter-intuitive findings. In fact, there are at least two possible stable values of resting membrane potential for a cell when the nonlinear, inwardly rectifying K+ conductance interacts with the seal current. This type of bistable behavior has been reported in a variety of small mammalian cells, including those from the heart, endothelium, smooth muscle and bone. Our theoretical treatment of these two common experimental situations provides useful mechanistic insights, and suggests practical methods by which these significant limitations, and their impact, can be minimized.

Reduced‐size UWB uniplanar tapered slot antennas without and with corrugations

AbstractThis paper presents the design of compact uniplanar Tapered Slot Antennas (TSAs) without and with corrugations for operation in an ultra wide band (UWB) of 3.1–10.6 GHz.In the initial step, a conventional size‐reduced uniplanar TSA with an exponential taper is designed. The analysis of its radiation pattern shows that this TSA exhibits reduced directivity in the lower part of UWB. To overcome this shortfall, two modifications are investigated. One includes an introduction of constant or variable‐length narrow corrugations and the other one making elliptical cuts on conducting sides of the TSA. The modified TSAs maintain the initial UWB impedance characteristics. However, their behavior differs with respect to the radiation pattern and gain. The TSA with constant‐length corrugations shows similar radiation pattern characteristics as it's non‐modified predecessor while the TSA with variable‐length corrugations exhibits an almost constant directive radiation pattern across UWB. The gain of these two antennas oscillates with frequency leading to pulse distortion. The TSA with elliptical conductor cuts shows both constant directive properties and distortionless pulse transmission. This is confirmed by full‐wave EM simulations and measurements. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:830–836, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25878

24-Element Antenna-in-Package for Stationary 60-GHz Communication Scenarios

An integrated multilayer antenna-in-package (AiP) targeted for stationary 60-GHz communication is presented. The key differences in design conditions for mass-market-level and prototype-level AiP are discussed and reflected during the design process. Hence, a low-cost and high-reliability package solution is realized. The proposed AiP consists of a 4 × 6 array of 24 stacked circular patch antennas and corresponding antenna feed lines designed for phased array. The finalized LTCC AiP prototype features 20 × 15 × 1.02 mm3 in dimension. Solder bump flip-chip technology is used to attach the AiP to the RFIC for system-level assembly. The assembled package is evaluated using a custom-designed near-field measurement setup. EM simulations and measurements confirm the presented AiP features more than 9 GHz bandwidth, 45° beam-steering ranges in both E- and H-planes, and more than 14.5 dBi gain at boresight.

Frequency adjustable microstrip annular ring patch antenna with multi-band characteristics

This study introduces a frequency-tunable dual-band microstrip annular ring patch antenna design for wireless local area network (2.45 GHz) and Worldwide Interoperability for Microwave Access (3.5 GHz) applications. The proposed antenna produces realisable gain higher than 5 dBi and return loss better than 10 dB for the stated applications. The antenna design consists of an annular ring patch loaded with a slot or gap. This loaded ring excites higher-order modes around the dominant mode (TM11) of the annular ring thus making this design capable of dual-band operation. This design is realised on a 1.57 mm thick polytetrafluoroethylene substrate using a coaxial probe feed. In this study, a novel technique for independent frequency tuning has also been introduced by cutting grooves on the periphery of the ring at the desired locations. Furthermore, the design capability of multi-band operation (2.45 GHz/3.5 GHz/5.5 GHz) has also been explained in the later part of the study. Antenna operation has been verified with the help of two commercially available EM solvers (CST Microwave Studio and Ansoft HFSS Designer) and measurements. A close agreement has been found between the simulated and the measured results.

Dual mode composite right-left-handed unit cells

This paper presents a new category of composite right-left-handed (CL-CRLH) unit cells. The new cells rely on complementary stubs, e.g., open and short circuited stubs in planar transmission lines or dual modes in coupled lines. They have geometrical circuit model, do not rely on commercial off-the-shelf components, and do not require vias. Theoretical expectations have been confirmed by EM simulations and measurements.

Sea-ice thickness distribution of the Bellingshausen Sea from surface measurements and ICESat altimetry

Although sea-ice extent in the Bellingshausen-Amundsen (BA) seas sector of the Antarctic has shown significant decline over several decades, there is not enough data to draw any conclusion on sea-ice thickness and its change for the BA sector, or for the entire Southern Ocean. This paper presents our results of snow and ice thickness distributions from the SIMBA 2007 experiment in the Bellingshausen Sea, using four different methods (ASPeCt ship observations, downward-looking camera imaging, ship-based electromagnetic induction (EM) sounding, and in situ measurements using ice drills). A snow freeboard and ice thickness model generated from in situ measurements was then applied to contemporaneous ICESat (satellite laser altimetry) measured freeboard to derive ice thickness at the ICESat footprint scale. Errors from in situ measurements and from ICESat freeboard estimations were incorporated into the model, so a thorough evaluation of the model and uncertainty of the ice thickness estimation from ICESat are possible. Our results indicate that ICESat derived snow freeboard and ice thickness distributions (asymmetrical unimodal tailing to right) for first-year ice (0.29±0.14 m for mean snow freeboard and 1.06±0.40 m for mean ice thickness), multi-year ice (0.48±0.26 and 1.59±0.75 m, respectively), and all ice together (0.42±0.24 and 1.38±0.70 m, respectively) for the study area seem reasonable compared with those values from the in situ measurements, ASPeCt observations, and EM measurements. The EM measurements can act as an appropriate supplement for ASPeCt observations taken hourly from the ship’s bridge and provide reasonable ice and snow distributions under homogeneous ice conditions. Our proposed approaches: (1) of using empirical equations relating snow freeboard to ice thickness based on in situ measurements and (2) of using isostatic equations that replace snow depth with snow freeboard (or empirical equations that convert freeboard to snow depth), are efficient and important ways to derive ice thickness from ICESat altimetry at the footprint scale for Antarctic sea ice. Spatial and temporal snow and ice thickness from satellite altimetry for the BA sector and for the entire Southern Ocean is therefore possible.

Development of an Image-Based System for Measurement of Membrane Potential, Intracellular Ca2+ and Contraction in Arteriolar Smooth Muscle Cells

Changes in smooth muscle cell (SMC) membrane potential (Em) are critical to vasomotor responses. As a fluorescent indicator approach would lessen limitations of glass electrodes in contracting preparations, we aimed to develop a Forster (or fluorescence) resonance energy transfer (FRET)-based measurement for Em. The FRET pair used in this study (donor CC2-DMPE [excitation 405 nm] and acceptor DisBAC(4) (3)) provide rapid measurements at a sensitivity not achievable with many ratiometric indicators. The method also combined measurement of changes in Ca(2+) (i) using fluo-4 and excitation at 490 nm. After establishing loading conditions, a linear relationship was demonstrated between Em and fluorescence signal in FRET dye-loaded HEK cells held under voltage clamp. Over the voltage range from -70 to +30 mV, slope (of FRET signal vs. voltage, m) = 0.49 ± 0.07, r(2) = 0.96 ± 0.025. Similar data were obtained in cerebral artery SMCs, slope (m) = 0.30 ± 0.02, r(2) = 0.98 ± 0.02. Change in FRET emission ratio over the holding potential of -70 to +30 mV was 41.7 ± 4.9% for HEK cells and 30.0 ± 2.3% for arterial SMCs. The FRET signal was also shown to be modulated by KCl-induced depolarization in a concentration-dependent manner. Further, in isolated arterial SMCs, KCl-induced depolarization (60 mM) measurements occurred with increased fluo-4 fluorescence emission (62 ± 9%) and contraction (-27 ± 4.2%). The data support the FRET-based approach for measuring changes in Em in arterial SMCs. Further, image-based measurements of Em can be combined with analysis of temporal changes in Ca(2+) (i) and contraction.

변형된 원형 버섯 구조의 0차 공진을 이용한 메타 재질 대역 통과 여파기의 설계

본 논문에서는 변형된 원형 버섯 구조의 메타 재질을 이용하여 새로운 대역 통과 여파기의 설계법을 제안한다. 0차 공진(Zeroth-Order Resonance: ZOR) 특성을 보이는 반원 형태의 버섯 구조 셀을 공진기로 이용하며, 각각의 이웃하는 0차 공진기 사이에 갭을 두어 용량성 결합을 유도한다. 제안된 메타 재질 대역 통과 여파기 설계법은 회로 해석 및 3차원 모의 실험과 측정을 통하여 해석 및 설계 목표와 비교 분석되어 그 타당성을 증명하였다. 0차 공진의 특수한 전계 분포 및 분산도를 통하여 메타 재질임을 증명하였으며, 대역 통과 여파기의 소형화에 대하여도 논의된다. In this paper, the design of a new bandpass filter based on the modified circular mushroom metamaterial structure is proposed. In detail, half circular mushroom cells are used as the zeroth order resonators(ZOR), and an intermediate gap is adopted to introduce the coupling between neighboring ZOR resonators. The proposed bandpass filter design is validated by the circuit and 3D EM simulations and measurements compared to the target specifications, and the metamaterial properties are proved by the ZOR field distributions and dispersion diagram. Also, the effect of size reduction is addressed.