Small Electrical Size Research Articles

Compact dual‐band circularly polarised GNSS antenna

As is well known, the global navigation satellite system (GNSS) antenna always suffers from the size problem. The authors' propose that two shorting probes in parallel are loaded on a patch antenna and a dual-band compact GNSS antenna, which has a smaller electrical size of only 60 mm (0.23λ) × 60 mm ×18 mm (0.07λ) × (λ being the wavelength in free space). A dual-layer feed network is also designed to achieve circular polarised radiation. Simulated and measured results show that the proposed antenna has good and stable performance over both dual operating bands.

Angular Displacement and Velocity Sensors Based on Coplanar Waveguides (CPWs) Loaded with S-Shaped Split Ring Resonators (S-SRR).

In this paper, angular displacement and angular velocity sensors based on coplanar waveguide (CPW) transmission lines and S-shaped split ring resonators (S-SRRs) are presented. The sensor consists of two parts, namely a CPW and an S-SRR, both lying on parallel planes. By this means, line-to-resonator magnetic coupling arises, the coupling level being dependent on the line-to-resonator relative angular orientation. The line-to-resonator coupling level is the key parameter responsible for modulating the amplitude of the frequency response seen between the CPW ports in the vicinity of the S-SRR fundamental resonance frequency. Specifically, an amplitude notch that can be visualized in the transmission coefficient is changed by the coupling strength, and it is characterized as the sensing variable. Thus, the relative angular orientation between the two parts is measured, when the S-SRR is attached to a rotating object. It follows that the rotation angle and speed can be inferred either by measuring the frequency response of the S-SRR-loaded line, or the response amplitude at a fixed frequency in the vicinity of resonance. It is in addition shown that the angular velocity can be accurately determined from the time-domain response of a carrier time-harmonic signal tuned at the S-SRR resonance frequency. The main advantage of the proposed device is its small size directly related to the small electrical size of the S-SRR, which allows for the design of compact angular displacement and velocity sensors at low frequencies. Despite the small size of the fabricated proof-of-concept prototype (electrically small structures do not usually reject signals efficiently), it exhibits good linearity (on a logarithmic scale), sensitivity and dynamic range.

CALCULATION OF RESONANT FREQUENCY OF HEXAGONAL SPLIT RING RESONATOR USING ANN

In this paper, an artificial neural network model is proposed to find out the resonant frequency of a metamaterial based Hexagonal Split Ring Resonator (SRR). The main advantage of Hexagonal SRR is small electrical size at resonance (electrically small) in the microwave regime. The method can be used for a wide range of different depending parameters (effective radius of the Hexagonal ring, split gap in the rings, width of the rings, spacing between the rings, depth of the substrate). The calculated resonant frequency is in very good agreement with the experimental results.

Transmission line approach to quantifying the resonance and transparency properties of electrically small layered plasmonic nanoparticles

The scattering and transparency properties of layered plasmonic nanoparticles are studied from the perspective of spherical transmission line theory. The advantage of this approach is that the interaction of the nanoparticle with its surroundings can be very conveniently represented as a combination of admittances. In this framework we reformulate the total impedance expression of a spherical nanoparticle, and from this we derive through a compact and intuitive methodology the two conditions that govern the resonance and transparency states of a nanoparticle. These conditions are satisfied when the particle’s input admittance becomes inductive and capacitive, respectively. The recursive relations that determine the TM admittance of an electrically small, radially inhomogeneous dielectric sphere are analyzed, and it is demonstrated that any degree of layering can be homogenized by a decomposition into successive binary mixtures. The appropriate material choice results in mixtures that exhibit multiple Lorentzian resonances that are directly mapped to the particle’s admittance, due to its small electrical size. Consequently, the particle’s admittance exhibits multiple inductive-to-capacitive switchings, and thus the resonance and transparency conditions are satisfied at multiple frequencies. This explains the well-known feature of multiple resonance–transparency pairs observed in the scattering signature of layered plasmonic nanoparticles.

Analysis and Design of a Novel Coupled Shorting Strip for Compact Patch Antenna With Bandwidth Enhancement

As it is well known, the bandwidth of a patch antenna will decrease with the decrease of antenna size, no matter what size reduction technique is adopted. In this letter, a detailed research on the shorting load, which is a traditional and effective size reduction technique for patch antennas, is done with the help of a transmission line (TL) model of the patch antenna, and a novel design of a coupled shorting strip with bandwidth enhancement is proposed. Based on the research, a compact circularly polarized (CP) patch antenna loaded by the proposed shorting strip is designed for the application of E6 band of COMPASS Navigation System, which has a small electrical size of only λ/7 ×λ/7 ×λ/15 (λ is the wavelength in free space). The simulated and measured results show that the proposed antenna has good and stable performance over the whole operating band, which means that it is quite an ideal compact antenna used for wideband satellite navigation applications.

Compact square spiral printed antenna

A novel compact printed antenna with a spiral winding and a loop feed is proposed. After optimising the design parameters, the prototype of the antenna with a small electrical size of 0.043λc × 0.043λc × 0.001λc is fabricated. It is shown that a central frequency as low as 425.9 MHz can be achieved without any additional matching networks, and a good omnidirectional radiation pattern similar to the dipole antenna is obtained.

Compact 2 $\times$ 2 Coupled Double Loop GPS Antenna Array Loaded With Broadside Coupled Split Ring Resonators

The design and nulling capability of a compact 2 × 2 dual-band coupled double loop (CDL) GPS antenna array loaded with broadside coupled split ring resonators (BC-SRR) are presented. The high level of L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> band mutual coupling is reduced by utilizing -negative (MNG) BC-SRR metamaterial within the array volume. This metamaterial loading is possible due to the small L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> band electrical size (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> / 8.5 × λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> / 8.5) of the CDL antenna elements. Different than the existing work on coupling reduction of linearly polarized antenna arrays, mutual coupling mechanism within the circularly polarized GPS array is considered and MNG metamaterials are shown to reduce the mutual coupling if they are placed between the antennas in a particular alignment. Specifically, a 2 × 2 array with inter-element spacing is designed to be loaded with BC-SRRs and experimentally verified to exhibit a 10 dB L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> band mutual coupling reduction. Through simulations and experiments, it is also demonstrated that the reduction in L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> band mutual coupling improves the L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> band array nulling capability in terms of accuracy and null depth without affecting the already well-behaved L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> band performance. The presented array has an overall footprint size 4.3" × 4.3" of and can be potentially miniaturized further for different inter-element spacing.

FRACTAL-BASED COMPOSITE RIGHT/LEFT-HANDED TRANSMISSION LINE AND ITS APPLICATIONS IN MINIATURIZED NEGATIVE-ORDER RESONANT ANTENNAS

In this article, a fractal-based composite right/left-handed transmission line (TL) is proposed, and its applications in miniaturized negative-order resonant (NOR) antennas are investigated. The TL unit-cell is constructed by etching a Hilbert-fractal slot on the surface of a substrate integrated waveguide structure. The dispersion analysis shows that the proposed TL can be used to design miniaturized NOR antennas. Then, two fractal-based NOR antennas are designed and fabricated. According to the measured results, the electrical sizes of the fabricated open-ended and short-ended antennas are 75.8% and 74.6% smaller than those of the reported counterparts, respectively. In addition, compared with the microstrip patch antennas, the fabricated antennas exhibit similar gain level and radiation patterns, but have a much smaller electrical size.

Design of small planar antennas based on double-layered CRLH metamaterials

This letter presents the design of a new efficient double negative metamaterial antennas. The design of the unit cell of these antennas is based on the composite right/left-handed (CRLH) transmission line model. The zeroth-order resonance of this kind of antennas depends mainly on the equivalent circuit of the unit cell and provides the opportunity to design the antenna with very small electrical size. The previous published results show that the conventional CRLH mushroom radiator suffers from narrow bandwidth and low gain. In this letter, we introduce a new method of design of CRLH metamaterial antennas to tackle the above problem using two layers of CRLH mushroom structure. The upper layer of the CRLH is used to reduce the reactance of the small antenna and to improve the matching between the antenna and the feeding line. The results at the zeroth-order resonance show improvements in the antenna gain and bandwidth by introducing the upper layer. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2224–2229, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27078

Double-sided open split ring resonator for compact microstrip band-pass filter design

A metamaterial structure, called the double-sided open split ring resonator (DOSRR), which combines two open split ring resonators (OSRRs) aligned over the opposite faces of the substrate in an inverted fashion is presented. A study of this resonator from full-wave electromagnetic and circuit simulations is performed. As with the OSRR cell, the DOSRR cell allows a series connection along a microstrip transmission line and it has a small electrical size. Moreover, the DOSRR cell has the ability to add a transmission zero in the out-of-band region without increasing its size. This DOSRR cell is used for the design of compact microstrip slow-wave-type band-pass filters. Two strategies based on circular windows etched at the bottom plane instead of square windows and U-shape slots etched in the microstrip transmission line are designed to increase the stop band and to add extra zeros in order to suppress the spurious band. The experimental results have confirmed the possibilities of this electrically small resonator (DOSRR) and the efficiency of both strategies to improve the out-of-band rejection.

Emission Calculation Methodologies for CHP Plants

The paperdiscussesdifferent calculation methods to correctly express the emission level of air pollutants produced byCHP(CombinedHeatandPower) systems, in order to take into account the environmentalbenefitdueto cogeneration. New and established methods to estimate the emission saving due to cogeneration of heat and power are reviewed and compared, with reference to small scale CHP systems; the paper clarifies that a proper emission assessment of CHP systems should consider both the global and the local scales of environmental impact. In particular, the method of the “avoided heat generator” is proposed in this study, for a local-scale environmental impact evaluation. This approach calculates the reduction of emission due to CHP operation, in comparison with the non-CHP operation of the same machine, taking into account the amount of pollutant emitted by a heat generator which provides the same thermal power of the cogenerator. Moreover, it is shown in the paper that another method, based on the PSI (Pollutant Saving Index) value, is suitable to estimate the global-scale environmental impact. The problem of the most representative unit of measure is also discussed, highlighting the advantages of an “output based” approach and providing easy-to-use formulas and graphs for the conversion of concentration values into output-based emission factors. Finally, a numerical evaluation of the CHP environmental benefit is provided for small electric power size CHP machines.

Dual-band microwave duplexer based on spiral resonators (SR) and complementary split ring resonators (CSRR)

In this work, a microstrip dual-band microwave duplexer implemented by means of a pair of dual-band branch-line hybrid couplers and a pair of dual-band band-stop filters is presented. The hybrid couplers are implemented by using complementary split ring resonators (CSRRs), etched in the ground plane, while the band-stop filters are made of spiral resonators (SRs) coupled to the host line. The measured duplexer characteristics are good and the device is compact by virtue of the small electrical size of the employed resonant elements. From this paper, it is clear that CSRRs and SRs are useful particles for the design of dual-band microwave systems requiring various microwave components.

Open complementary split ring resonators: Physics, modelling, and analysis

This article is focused on the physics and analysis of a new type of planar resonant particles: the open complementary split ring resonators (OCSRRs). These resonators are the complementary counterpart of the open split ring resonators (OSRRs), previously presented by some of the authors, and consist on a pair of concentric hooks etched on a metal layer in opposite orientation. Like OSRRs, OCSRRs are open resonators that can be excited by means of a voltage or current source. An accurate circuit model of the particle is proposed and experimentally validated by exciting the particle by means of a coplanar waveguide transmission line. It will be also shown that OCSRRs exhibit higher order resonance frequencies, which can be selectively suppressed by introducing additional elements, as derived from a simple analysis based on mode parity. Because of the small electrical size of OCSRRs, such particles are useful for the synthesis of planar metamaterials and microwave components. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1520–1526, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25282

A Novel Electrically-Small Microstrip Genetic Antenna

One of the most challenging problems in antenna design is that of the electrically-small antenna. A novel genetic antenna with electrically-small property is presented. To make use of the simple and low cost microstrip fabrication techniques, this antenna adopts a two-dimensional microstrip structure rather than the commonly-used three-dimensional wire structure. It includes a 7-segment microstrip line as its radiator and is directly fed from a 50Ω coaxial line without an impedance transformer that is necessary for most electrically-small antennas. After designed by a parallel Genetic Algorithm (GA) in conjunction with the Finite Different Time Domain (FDTD) method on a cluster system, a prototype antenna was fabricated and measured. Results show that its resonant frequency is only 0.775 GHz, which corresponds to a very small electrical size of 0.147λ and kre = 0.46, where k is the wave vector in the free space, and re is the radius of the smallest sphere enclosing the entire antenna system.

COMPARATIVE INVESTIGATION OF RESONANCE CHARACTERISTICS AND ELECTRICAL SIZE OF THE DOUBLE-SIDED SRR, BC-SRR AND CONVENTIONAL SRR TYPE METAMATERIALS FOR VARYING SUBSTRATE PARAMETERS

This paper introduces a planar µ-negative (MNG) metamaterial structure, called double-sided split ring resonator (DSRR), which combines the features of a conventional SRR and a broadside-coupled SRR (BC-SRR) to obtain much better miniaturization at microwave frequencies for a given physical cell size. In this study, electromagnetic transmission characteristics of DSRR, BC-SRR and conventional SRR are investigated in a comparative manner for varying values of substrate parameters which are thickness, the real part of relative permittivity and dielectric loss tangent. Simulation results have shown that magnetic resonance patterns of all these three structures are affected in a similar way from variations in permittivity and in loss tangent. However, changes in substrate thickness affect their resonance characteristics quite differently: In response to decreasing substrate thickness, resonance frequency of the SRR increases slowly while the bandwidth and the depth of its resonance curve do not change much. For the DSRR and BC- SRR structures, on the other hand, resonance frequency, half power bandwidth and the depth of resonance curve strongly decrease with decreasing substrate thickness. Among these three structures, all having the same unit cell dimensions, the newly suggested DSRR is found to reach the lowest resonance frequency, hence the smallest electrical size, which is a highly desired property not only for more effective medium approximation but also for miniaturization in RF design. The BC-SRR, on the other hand, provides the largest

Compact lowpass filters with very sharp transition bands based on open complementary split ring resonators

It is shown that open complementary split ring resonators (OCSRRs) are useful particles for the design of lowpass filters with very narrow transition bands in microstrip technology. Owing to the small electrical size of OCSRRs, the filters are also very small. These filters are implemented by cascading several OCSRR stages in a microstrip line. The OCSRR stages can be modelled as parallel resonators in series configuration, thus providing a transmission zero at their resonance frequency. By designing the OCSRRs with small inductance and high capacitance, very sharp cutoffs are achieved. To illustrate the possibilities of the approach, a prototype device example is provided. It consists on a five-stage periodic microstrip lowpass filter with 3 dB insertion losses at 1.33 GHz and 40 dB rejection at 1.45 GHz. To improve out-of-band rejection, four additional OCSRR stages tuned at the spurious frequency band have been cascaded. Filter dimensions are 39×7.4 mm (i.e. 0.46λ× 0.087λ, where λ is the guided wavelength at the cutoff frequency). These filters are of interest in applications where small size and severe cutoff requirements are required.

An Improved Multilevel Green's Function Interpolation Method With Adaptive Phase Compensation

An improved multilevel Green's function interpolation method (MLGFIM) with adaptive phase compensation (APC) is proposed. The difficulty in applying interpolation approaches to the fast varying phase term in the integral equation kernel for full-wave electromagnetic (EM) simulations is eradicated by using the phase compensation and adaptive direction separation (ADS). The multilevel tree structure in MLGFIM keeps the number of direction separation invariant at all levels, attributing to the recursive interpolation with multilevel phase compensation. The proposed MLGFIM-APC in conjunction with the Lagrange-Chebyshev interpolation yield an O(N log N) CPU time and O(N) computer memory requirement for surface scattering problems. By introducing a transition level, the MLGFIM-APC can adaptively incorporate interpolation techniques of conventional interpolation (CI), transition interpolation (TI) and phase-compensation interpolation (PI), corresponding to electromagnetic simulation of problems of small, moderate, and large electrical sizes, respectively. Large-scale microstrip antenna arrays are simulated to illustrate the accuracy and efficiency of the proposed method. It is found that the CPU time scales better than O(N log N) for these co-planar problems.

A BEVELED AND SLOT-LOADED PLANAR BOW-TIE ANTENNA FOR UWB APPLICATION

Abstract—A novel planar bow-tie aperture antenna is proposed for ultra-wide band (UWB) application in this paper. Beveling technique is employed to increase the impedance bandwidth, and slot loading is introduced to improve the impedance matching. The measured impedance bandwidth is from 2.7 to 12 GHz for S11 < −10 dB, proving the effectiveness of these two techniques. The measured radiation patterns are relatively stable almost over the entire ultra-wide band of 3.1 to 10.6 GHz with low cross-polarization levels of at least −10 dB. Moreover, the proposed antenna maintains the advantages of ease of fabrication and relatively small electrical size.

Applications of resonant‐type metamaterial transmission lines to the design of enhanced bandwidth components with compact dimensions

AbstractIn this article, it is demonstrated that metamaterial transmission lines implemented by means of complementary split rings resonators are useful for the design of planar microwave components with small dimensions and broad operational bandwidths. These characteristics are achieved thanks to the small electrical size of complementary split rings resonators and to the controllability of the dispersion diagram in such artificial lines. The technique is illustrated by means of the design of a rat‐race hybrid coupler. The performance and size of this metamaterial‐based component is compared with those characteristics and dimensions of the classical (distributed) implementation. It is clearly demonstrated that by replacing the conventional transmission lines in the design with metamaterial transmission lines conveniently engineered, the functionality of the device is preserved over broader bandwidths and, additionally, significant size reduction is achieved. These characteristics and the absence of lumped elements in the design are of interest for applications in which cost and compatibility with fully planar technology are fundamental aspects. The most relevant contribution of the article is the demonstration of the compatibility between the resonant artificial lines and the design of broad band and high performance microwave components. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 127–134, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22990

Design of Wide-Band Semi-Lumped Bandpass Filters Using Open Split Ring Resonators

Open split ring resonators (OSRRs) are used in this letter to design wide-band semi-lumped bandpass filters. OSRRs work as lumped LC series elements due to their small electrical size and can be then used as building blocks of reduced size band pass filters. The values of the capacitance, C, and inductance, L, of the OSRR are controlled by adjusting the geometrical parameters of the coupled open rings. In our design, the OSRRs are connected through quarter-wave lines which act as inverters. The impedance of these inverters have been conveniently calculated to achieve the filter specifications. Finally bending and/or meandering techniques have been applied so as to obtain highly compact designs. Experimental verification is provided and good agreement has been found between electromagnetic simulations and measurements