Vasa Radonic

Fractal Geometries of Complementary Split-Ring Resonators

Complementary split-ring resonators (CSRRs) are typically used as negative-permittivity particles in microstrip left-handed structures. In this paper, novel CSRRs that use a square Sierpinski fractal curve are proposed and studied in detail. It is shown that the application of fractal geometries results in significant miniaturization of the metamaterial unit cell in comparison with conventional and equivalent meander structures. Multiple fractal CSRRs are also analyzed. The influence of different geometrical parameters and the order of the fractal curve on the performances are investigated, as well as the efficiency of excitation of the particles. When used in the design of left-handed transmission lines, fractal complementary split rings improve frequency selectivity in the upper transition band when compared to other nonfractal topologies.

Complementary Split Ring Resonators Using Square Sierpinski Fractal Curves

Split ring resonators and complementary split ring resonators are used in a left-handed media to obtain negative values of permeability and permittivity, respectively. In this paper, novel split ring geometry using square Sierpinski fractal curves is proposed, that reduces resonant frequency of the structure and achieves improved frequency selectivity in the upper transition band. In order to validate the results, left-handed microstrip line that uses square Sierpinski complementary split ring resonators is designed, fabricated and measured

Flexible Sierpinski Carpet Fractal Antenna on a Hilbert Slot Patterned Ground

This paper presents a novel design of fractal antenna on a flexible substrate that operates in UMTS band (universal mobile telecommunication system, 1.92–2.17 GHz). The antenna consists of a Sierpinski carpet fractal radiator, which reduces the overall size of the antenna, and it is realized on top of a Hilbert slot in the ground layer, to achieve required impedance matching. The antenna is compact with the overall dimensions equal to 70 mm × 31 mm × 0.075 mm. Influence that folding has on the initial planar topology is investigated in detail. The obtained results show that the proposed antenna is more tolerant to folding than the conventional patch and that it exhibits relatively stable radiation patterns even when folded in complex manners.

A New Fractal-Based Design of Stacked Integrated Transformers

Silicon-based radio-frequency integrated circuits are becoming more and more competitive in wide-band frequency range. An essential component of these ICs is on-chip (integrated) transformer. It is widely used in mobile communications, microwave integrated circuits, low-noise amplifiers, active mixers, and baluns. This paper deals with the design, simulation, and analysis of novel fractal configurations of the primary and secondary coils of the integrated transformers. Integrated stacked transformers, which use fractal curves (Hilbert, Peano, and von Koch) to form the primary and secondary windings, are presented. In this way, the occupied area on the chip is lower and a number of lithographic processes are decreased. The performances of the proposed integrated transformers are investigated with electromagnetic simulations up to 20 GHz. The influence of the order of fractal curves and the width of conductive lines on the inductance and quality factor is also described.

Comparison of Commercially Available Full-Wave EM Simulation Tools for Microwave Passive Devices

A great number of software packages specialized for CAD and EM simulation of microwave components is commercially available today. However, choosing optimal package for an application is not trivial. This paper presents comparison of two widely used full-wave EM simulation tools: Ansofts High Frequency Structure Simulator and EMSight - EM simulator in Microwave Office from Applied Wave Research (AWR)

A Microwave Microfluidic Sensor Based on a Dual-Mode Resonator for Dual-Sensing Applications

In this paper, we propose a novel microwave microfluidic sensor with dual-sensing capability. The sensor is based on a dual-mode resonator that consists of a folded microstrip line loaded with interdigital lines and a stub at the plane of symmetry. Due to the specific configuration, the resonator exhibits two entirely independent resonant modes, which allows simultaneous sensing of two fluids using a resonance shift method. The sensor is designed in a multilayer configuration with the proposed resonator and two separated microfluidic channels—one intertwined with the interdigital lines and the other positioned below the stub. The circuit has been fabricated using low-temperature co-fired ceramics technology and its performance was verified through the measurement of its responses for different fluids in the microfluidic channels. The results confirm the dual-sensing capability with zero mutual influence as well as good overall performance. Besides an excellent potential for dual-sensing applications, the proposed sensor is a good candidate for application in mixing fluids and cell counting.

Novel Hilbert soil-moisture sensor based on the phase shift method

In this paper, novel soil-moisture sensor based on the Hilbert fractal curve is proposed. The developed sensor is intended to be integrated into wireless sensor network whose goal is the monitoring of the agricultural soils. The operating principle of this sensor is based on the phase shift method which in essence represents the measurement of the soil permittivity. Analytical expressions for the calculation of optimal operating frequency and the absolute moisture content derived from effective permittivity are presented. The influence of the order and the number of fractal curves used to the sensor characteristics are analyzed. The proposed sensor operates at 1.2 GHz and provides phase shift in the range of 70.76° for the extreme cases of the soil moisture content (2 % and 20 %).

On the Orientation of Split-Ring Resonators in Metamaterial Media

Split-ring resonators (SRR) are used both in microstrip and waveguide metamaterial structures to obtain negative values of permeability, whereas complementary split- ring resonators (CSRR) result in negative permittivity when placed below the microstrip. While the orientation of SRR positioned next to the microstrip transmission line significantly influences its performances, it is generally accepted that such dependence does not exist in the case of CSRR-loaded microstrip or SRR-loaded waveguide. In this paper, we show that SRR and CSRR can not be arbitrarily orientated, neither in microstrip nor in waveguide structures. The influence of the orientation is especially visible in the case of multiple CSRR geometries. To validate simulation results, microstrip lines loaded with multiple CSRRs were designed, fabricated and measured.

Accuracy of EM Simulation Tools in Modeling of Resonant Left-Handed Microstrip Lines

Split ring resonators and complementary split ring resonators are used in left-handed media to obtain negative values of permeability and permittivity, respectively. A typical resonant left-handed (LH) microstrip line, composed of complementary split ring resonators (CSSR) and capacitive gaps in the microstrip, exhibits a pass-band behavior. However, a significant shift between the measured and simulated values of the central frequency of the pass-band always occurs. In this paper, three widely used full-wave simulation tools: Ansofts high frequency structure simulator, EMSight in Microwave Office, and IE3D from Zeland Software Inc., are compared for the case of resonant LH transmission lines. The simulation results are compared with the measured data.

Compact tri-band bandpass filter based on quarter-wavelength resonators

In this work, a planar microstrip tri-band filter based on quarter-wavelength resonators is presented, which allows independent control of the positions of all three passbands. Furthermore, the topology of the filter provides five transmission zeros and thus results in a highly selective response in all passbands. A synthesis procedure of the filter is presented and used to design a tri-band filter which operates at WLAN frequencies of 2.4/3.5/5.2 GHz. The designed filter outperforms all other state-of-the-art tri-band filters in terms of compact size, high selectivity and transmission, and return-loss characteristics.