Capacitive Strip Research Articles

Miniaturized circularly polarized metasurface antenna based on characteristic mode analysis

AbstractA miniaturized circularly polarized (CP) metasurface (MTS) antenna is investigated based on characteristic mode theory (CMT). The 4 × 4 square patch structure was used as the initial structure for characteristic mode analysis (CMA) and improvement using CMT to guide the evolution of antenna structures. The square ring is bent and the capacitive strips are introduced to obtain the final miniaturized MTS. Comparing the proposed MTS with traditional MTS, the proposed antenna size is significantly reduced. To give the proposed antenna a CP, a feeding structure with a 90° phase difference is designed to excite a pair of orthogonal target patterns. The final antenna structure has a reduced overall size and has circular polarization characteristics. For verification, the proposed CP MTS antenna is fabricated and measured. The measured results show an impedance bandwidth of 2.9–3.65 GHz and 3 dB axial ratio bandwidth of 3.1–3.57 GHz, and a stable gain in the operating frequency band.

Dual-mode hyperbolicity, supercanalization, and leakage in self-complementary metasurfaces

Abstract Anisotropic Self-Complementary Metasurfaces (SC-MTSs) are structures constituted by an alternation of complementary inductive and capacitive strips, which are “self-dual” according to Babinet’s duality principle. They support the propagation of two orthogonally polarized surface-wave modes with the same phase velocity along the principal directions (i.e., along the strips and normal to them). The isofrequency dispersion curves of these modes are hyperbolas, and therefore, these MTSs fall in the category of hyperbolic MTSs. It is shown here that the hyperbolic dispersion curves may degenerate in same cases into almost straight lines, which implies that the velocity of energy transport is constantly directed along the same direction for any possible phasing orthogonal to the strips. In this circumstance, the SC-MTS can be conveniently used to design dual-polarized leaky-wave antennas by modulating the impedances of the complementary strips.

Synthesis Design of Bandpass Frequency Selective Surface With Multiple Transmission Zeros Using Slotline Structures

This article presents a synthesis method to design a new type of bandpass frequency selective surfaces (FSSs) with multiple transmission zeros (TZs). To briefly show the concept of our synthesis method, a generalized topology of the bandpass FSS based on cascaded slotline sections paralleled with bandpass resonators is first presented to map with an alternative <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> th-order bandpass filtering network with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$J$ </tex-math></inline-formula> -inverters and typical LC parallel resonators. Then, two kinds of composite LC parallel resonators, named as LC – LC and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}$ </tex-math></inline-formula> – LC parallel resonators, are introduced and discussed to replace the typical LC parallel resonators, which can produce TZs at skirts of the passband and increase the out-of-band selectivity. The derivations of equivalent relationships between the composite and typical LC resonators are given. Furthermore, for the exploration of bandpass FSS with multiple out-of-band TZs, the realization of these two discussed composite LC parallel resonators is exhibited by inductive and capacitive strip lines loading on slotline structures. The design curves and guidelines are given and discussed correspondingly. To validate our design concept, two FSS examples, a second-order bandpass FSS with four out-of-band TZs and a third-order one with five out-of-band TZs, are synthesized and designed. In final, these two designed bandpass FSS prototypes are fabricated and then measured by the free-space measurement method. The measured results show that the desired stable bandpass filtering performance and independently multiple out-of-band TZs are successfully realized.

A Capacitive Strip Sensor for Detecting Partial Discharge in 110-kV XLPE Cable Joints

The joints of cross-linked poly ethylene (XLPE) power cables often suffer the frequent faults and latent defects, which can be detected effectively by partial discharge (PD). In this paper, a novel capacitive strip sensor for the PD measurement is proposed and testified under the context of prefabricated 110-kV XLPE cable joints. First, a simulation model based on finite integration technique is established. Then, the transmission mode and the frequency spectrum of the electromagnetic wave related to the PD signal are investigated. Furthermore, the energy distribution of the PD signal among the cable joint is analyzed to identify the optimal position of installation. Finally, a real capacitive strip PD detection sensor is deployed on a 110-kV XLPE cable system, and comparative tests with a standard sensor are conducted. Consistent experimental results have been observed, and a sensitivity better than 5 pC has been achieved on the proposed capacitive strip sensor, which clearly shows its potential on online PD monitoring for high voltage power cable joints.

A High-Efficiency Compact Planar Antenna for ISM Wireless Systems

A novel high-efficiency compact planar antenna at 433 MHz with minimized size and low-cost and easy to integrate into the ISM wireless applications is designed, fabricated, and measured. Capacitive strips that are formed by cutting inter-digital slots and the meander lines on both sides are introduced to greatly reduce the antenna size yet maintain the high efficiency. The proposed antenna has a simple planar structure and occupies a small area (i.e., 45 × 30 mm2). This novel electrically small antenna can be operated well without any lumped elements for impedance matching. Details of the antenna design and experimental results are presented and discussed.

A skewed omega for LHM characteristics

ABSTRACTThis letter reports numerical and experimental study on a concentric‐edge‐coupled low‐loss MTM structure composed of concentric skewed omega inclusion and capacitive strip wire unit cells for DNG behavior via transmission and reflection characteristics. Modified NRW method provides effective medium parameters, refractive index, and the dispersion characteristic from simulated S‐parameters. It is shown that this MTM exhibits DNG behavior over 3.65–4.53 GHz band. It also investigates the effect of geometrical parameters, like strip width, slit gap, length and width of each side, and arc length on magnetic resonant frequency. Incidence of perpendicularly polarized electromagnetic wave on a host medium embedding metallic skewed omega inclusions interact shows negative material parameters for the composite media in the frequency band of interest. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:847–850, 2016

Small-Size Stacked Inverted-F Antenna With Two Hybrid Shorting Strips for the LTE/WWAN Tablet Device

The stacked inverted-F antenna with two hybrid shorting strips placed close to the antenna's feeding strip can provide two wide operating bands to cover long-term evolution/wireless wide-area network operation (698-960/1710-2690 MHz) in the tablet device. The antenna's lower and higher bands are, respectively, contributed by the longer and shorter arms of the antenna. The two hybrid shorting strips include an inductive shorting strip (chip-inductor-loaded strip) and a capacitive shorting strip which capacitively couples to the antenna's shorter arm. The longer arm is also coupled through a chip inductor to the feeding strip such that the longer arm has a decreased resonant length for the low-band operation and, on the other hand, has very small effects on the high-band operation, which is mainly contributed by the shorter arm. The feeding strip is also embedded with a chip capacitor such that an internal high-pass matching circuit formed by the inductive shorting strip and the capacitive feeding strip is obtained to greatly widen the antenna's low-band bandwidth, with small effects on the high-band operation. On the other hand, the capacitive shorting strip is added to greatly enhance the bandwidth of the antenna's higher band, with small effects on the low-band operation. Two wide operating bands are hence easily obtained and adjusted. The antenna can also be recessed in a small ground clearance of 10 × 35 mm 2 inside the tablet device such as a tablet computer in this study. Details of the proposed antenna are presented.

DUAL BAND COPLANAR CAPACITIVE COUPLED MICROSTRIP ANTENNAS WITH AND WITHOUT AIR GAP FOR WIRELESS APPLICATIONS

This article presents the coplanar capacitive coupled probe fed microstrip antennas for dual frequency band operation. The proposed antenna is excited by a single probe feed connected to a capacitive strip. Of the two dual band antennas presented here, the flrst one uses small air gap and the other is designed without air gap. In the flrst case an efiort has been made to reduce the height of suspended antenna. A vertical slot is placed to obtain antenna resonance at low frequency side, and also for proper impedance matching. After presenting the basic geometry the second conflguration (which uses no air gap) which also ofiers dual band operation at the expense of reduced bandwidth is presented. Measured values fairly agree with the simulated results.

A Novel Quad-Band Diversity Antenna for LTE and Wi-Fi Applications With High Isolation

A novel quad-band diversity antenna is presented with two radiating elements suitable for long-term evolution (LTE) and wireless fidelity (Wi-Fi) applications in handheld devices. The radiating elements are two planar inverted F-shaped antennas (PIFA) constructed by a meandered line and folded patch with interdigitated capacitive strips connected to the folded patch. To achieve high isolation between the two radiating elements, a defected ground plane (a combination of rectangular slot ring and inverted T-shaped slot stub) is employed. The antenna is designed to operate in the 746-787 MHz, 1850-1990 MHz, 1920-2170 MHz, and 3600-3700 MHz frequency bands. The characterization of the antenna in free-space as well as in the proximity of the user head and hand is presented. The results confirm the excellent performance of the proposed diversity antenna.

Simulation and Design of Orthogonal Capacitive Strip CdZnTe Detectors

Orthogonal strip detectors are single-carrier devices that allow reduction of the amount of read-out channels while obtaining a good spatial resolution. They are especially interesting for low count rate imaging applications like gamma-ray medical imaging. Nevertheless, applying a bias voltage between X and Y strips is necessary in order to localize correctly the interactions. Unfortunately, this bias voltage induces a leakage current, thus generating an unwanted shot noise. We propose in this paper a new setup using capacitive contacts, which suppresses leakage currents between collecting and non-collecting strips. In this paper, we first briefly present the state-of-the-art relative to coplanar grid and strip detectors, their advantages and their drawbacks. In a second part, we will focus on the theoretical background of the capacitive contact. In a third part, a simulation study of the electrode geometry is reported. Thanks to the spectral approach, we have computed the 3D applied and weighting electric fields, bulk resistances and capacitances for various geometries of the design. Afterwards, we have used these data to simulate pulse waveforms and study the associated electronics. Finally the fabrication of the devices is presented and our first experimental results are reported. As a conclusion, we will discuss the interests and the limitations of this kind of devices.

Planar Miniature RFID Antennas Suitable for Integration With Batteries

A class of planar, electrically-small UHF antennas suitable for direct integration with electronic components such as batteries is introduced. The new design approach combines a meander line section and a capacitive strip section. The geometries of the two sections can together be scaled in size over a wide range of planar form factors while still maintaining self-resonance and practically realizable line widths and spacings. No external matching network is required. Moreover, batteries can be mounted above or below the capacitive strip section, significantly reducing the total size of a wireless device. Three designs are demonstrated on printed circuit board at 433 MHz. Measurements show that the antennas provide good gain and excellent bandwidth, omnidirectional radiation patterns, and electrically small size. The results of this work have numerous uses in radiofrequency identification (RFID)

Road-Damaging Potential of Measured Dynamic Tyre Forces in Mixed Traffic

A series of tests was conducted on a British trunk road in which the dynamic tyre forces generated by approximately 1500 heavy goods vehicles (HGVs) were measured using a load measuring mat containing 144 capacitive strip sensors. The data were used to investigate the relative road-damaging potential of the various classes of vehicles. Air suspensions were found to be more effective at static load equalization than steel suspensions. Two criteria were used to rank axle groups in terms of road damage: the average dynamic load coefficient and the 95th percentile aggregate fourth-power force. These criteria were found to rank axle groups in different orders, due to spatial correlation between tyre forces. On average, air suspended vehicles were found to generate smaller dynamic loads and hence less road damage than steel suspended vehicles. However, some air suspensions with inadequate suspension damping were found to generate very high dynamic loads and consequently very high levels of road damage.

Wideband filters employing multilayer gratings

Multilayer surfaces, consisting of stacked inductive and capacitive strips or grids, have been used to design wideband filters in the 5–40 GHz range, with rapid transitions between reflection and transmission. For singly polarised applications, transmission bandwidths of 70–100% and edge transition ratios of 1.1–1.3 are realisable at 45° TM incidence using 4–8 layers of capacitive and inductive strips. Factors which constrain the passbands are highlighted. In dual polarised designs using doubly periodic grids, the widths are restricted to 35–40% by TE incidence grating responses at the upper passband edge. In TM they are even more restricted by a TE11 mode resonance. Wider passbands require high inductances to reduce the low frequency edge, implying very fine conductors.

Impedance Calculation of Three Narrow Resonant Strips on the Transverse Plane of a Rectangular Waveguide (Short Paper)

A theoretical analysis has been developed to calculate the impedance of two inductive strips and one capacitive strip located on the transverse plane of a rectangular waveguide. The current ratios among the strips were determined by a variational method and then used for impedance calculations. The results can be applied to the impedance calculations of a single capacitive strip, two inductive strips, or three inductive ships as special cases.

Impedance transformation in fin lines

Various discontinuities in the slot width of fin lines are accurately analysed. These include a step in the slot width, an inductive notch, a small capacitive strip and a longitudinal stripe for mounting a semiconductor diode. Equivalent circuits are derived and related to the geometrical parameters. The results can directly be applied to a design of impedance transforming and filter networks.

Analysis of a Narrow Capacitive Strip in Waveguide

A theoretical determination is made for the susceptance of a narrow conducting strip inserted vertically into a waveguide. The theory is based upon a variational form for the susceptance. A suitable current distribution along the strip is obtained for the variational equation, and is found to be similar to that determined from analysis of backscattering by a cylindrical obstacle irradiated from an incident plane wave. Accurate theoretical results may be obtained using a sinusoidal current distribution having a phase constant of /spl pi//2d, where d is the strip depth. Experimental results agree closely with the theory in the dominant-mode range and also at frequencies below cutoff.

Thickness Corrections for Capacitive Obstacles and Strip Conductors

Capacitive thickness corrections are derived exactly for two basic geometries involving pairs of semi-infinite plates. In one arrangement the pair of plates are coplanar, while in the other they are parallel to each other. In each case the total capacitance per unit length between the pair of plates is infinite, but the incremental increase of capacitance when the thickness is increased from zero to a value t is finite. These capacitance increments are evaluated, and it is shown how they may be used as approximate thickness corrections in a great varity of more complicated geometries involving capacitive obstacles in waveguide, coaxial line, and artificial dielectric media. They may also be applied to coupled-strip-line conductors. As examples, the corrections are applied in detail to a waveguide iris, and to three useful coupled-strip-line cross sections.

The impedance of unsymmetrical strips in rectangular waveguides

The radiation from capacitive and inductive strips is calculated in terms of arbitrary currents flowing on the strip surfaces. By requiring the tangential component of the sum of an incident field and the radiated field to vanish at the surface of the strip, an integral equation for the currents is obtained. This integral equation is solved by a transformation of variables due to Schwinger. The integrals involved in the final solution are given in terms of standard elliptic integrals.The following generalizations of the well-known quasi-static formulae for symmetrically located strips are obtained:(a) Capacitive strip of width D, centre x0 from waveguide side; waveguide dimensions a × b (see Fig. 1).Susceptance B=4b/λg log Θ(β)/(1+s)Θ(0)where cn β = c/(1+s)c = cos(πx0/b) sin(½πD/b).s = sin(πx0/b) cos(½πD/b).The modulus of the elliptic functions is [4s/(1+s)2−c2]½(b) inductive strip of width D, centre Y0 from waveguide side; waveguide dimensions a × b (see Fig. 2).Reactance X= a/λg[−1+K cosec2 (πy0/a)/2E − K sin2 (½π D/a)]The modulus of the elliptic functions is[1 − sin2 (½π D/a) cosec2 (πy0/a)]½