In this paper a novel evolutionary algorithm is used for the optimization of the performance of a magnetorheological (MR) device, capable to transmit torque between two shafts and powered by a system of Permanent Magnets (PMs). The stochastic, evolutionary, global optimization algorithm is based on a modified version of the self-organizing map. It uses a dedicated simplied analytical model of the device, developed in order to obtain a fast and accurate evaluation of the torque. Then, by means this model, the cost function to find the optimal parameters of the device is defined. Once the optimal parameters are identified, the performance of the proposed device is simulated by means of a FEM software. The results in terms of magnetic flux density inside the fluid, the transmissible torque and the actuation torque necessary to perform the device activation are discussed. Finally, a preliminary experimental validation of the proposed device is performed.

Ultra-wideband (UWB) antennas have advantages such as high data rates, improved multipath resistance and lower power consumption. In this work, UWB patch antennas based on electrically conductive adhesive were manufactured with a simple technique and evaluated in the laboratory. Results showed that the thickness of the samples ranged from 207 to 261 μm. The bandwidth optimization obtained was 200% compared to a traditional copper-layer antenna. UWB antennas showed an average bandwidth of 8.558 GHz in the region 609 MHz to 9.105 GHz. The antennas covered the whole of UHF band, L band, S band, C band and part of X band. Finally, the proposed technique allows reducing the size of patch by 70% for low frequencies of operation, while achieving a similar performance.

An analysis on the calculation of the inverse discrete Fourier transform (IDFT) of passband frequency response measurements in terms of lowpass equivalent responses is shown, in order to specify the differences in the results given from different common algorithms; differences with respect to the calculation of the IDFT for true lowpass responses are remarked. It is shown how the basic sequence has to be represented in time domain by invoking the causality, which is supported by results. Results are corroborated by an application on measured data in a reverberation chamber. The present analysis helps readers understand different IDFT algorithms used by Manufacturers and make their own codes whenever desirable.

In this paper, a novel terahertz tunable bandstop filter with constant absolute bandwidth is proposed, which consists of graphene-based three-section L resonators. In order to perform bandstop property, the L resonator is used and analyzed in details based on the traditional Z matrix and ABCD matrix. With the introduction of graphene materials, the operating frequency of bandstop filter can be extended to terahertz. Moreover, the tunable performance with constant absolute bandwidth can be achieved by only loading different chemical potentials on a graphene surface. For demonstration, a terahertz tunable bandstop filter prototype is designed and simulated with chemical potentials of 0.1, 0.3, and 1 eV. The simulated results agree well with the anticipation perfectly.

This study presents a novel technique for designing an ultra-wideband (UWB) filtering-antenna with dual sharp band notches. This design composed of a modified monopole antenna integrated with resonant structures. The monopole antenna is modified using microstrip transition between the feedline and the patch. In addition, block with a triangle-shaped slot is loaded on both sides of the ordinary circular patch to produce wide bandwidth with better return loss and higher frequency skirt selectivity. The resonant structures based on two double split ring resonators (DSRR) loaded above the ground plane of the antenna design to produce dual notched bands, and filter out WiMAX (3.3-3.7 GHz) and HiperLAN2 (5.4-5.7 GHz) frequencies. The band notch position is controlled by varying the length of the DSRR. The reconfigurability feature is achieved by using two PIN diode switches employed in the two DSRR. The measured results show that the proposed filtering-antenna provides wide impedance bandwidth from 2.58 to 15.5 GHz with controllable dual sharp band notches for WiMAX and HiperLAN, peak realized gain of 4.96 dB and omnidirectional radiation pattern.

A portable microscope has been created through our work, so that we can observe and collect images in future scientific research whenever and wherever possible. The portable microscope is made up of a small LED chip, compact lens modules, a commonly used SLR camera and a USB driven power. The microscopic morphological features can be observed through our system. We also demonstrate that this standalone system can work well in moving state. Therefore, the portable microscope that has the potential for becoming a point-of-care setup in terms of health monitoring is appropriate for on-site micro-imaging.

An innovative and general approach is proposed to the optimal, mask-constrained power synthesis of circular continuous aperture sources able to dynamically reconfigure their radiation behavior by just modifying their phase distribution. The design procedure relies on an effective a-priori exploration of the search space which guarantees the achievement of the globally-optimal solution. The synthesis is cast as a convex programming problem and can handle an arbitrary number of pencil and shaped beams. The achieved solutions are then exploited as reference and benchmark in order to design phase-only reconfigurable isophoric circular-ring sparse arrays. Numerical results concerning new-generation telecommunication systems are provided in support of the given theory.

A decoupling network for a pair of strongly coupled MIMO antennas is presented. The decoupling network is composed of two inverters and two split ring resonators (SRRs) that are also coupled. By properly transforming the mutual admittance of the original coupled antennas and properly designing the coupling between the two SRRs, more than 20dB isolation between the two antennas can be achieved while their respective matching performances remain good. To validate the concept, a microstrip decoupling network is designed and implemented for a pair of wideband printed monopole antenna elements. Measurement results have demonstrated that nearly 10% bandwidth for 20 dB isolation can be achieved. Measured radiation patterns have demonstrated a significant reduction of the correlation coefficient, which makes the proposed technique a promising candidate for both current and future generations of MIMO-enabled mobile terminals.

A novel dual-band bandstop filter based on a square, symmetric dumbbell-shaped resonator and U-shaped slot defected ground structure is presented. First, the characteristic of the fundamental structure which adopts two dumbbell-shaped resonators and one U-shaped slot is analyzed. Simulated results demonstrate that the proposed structure induces two transmission zeros within 2-8 GHz. Then, the structure adopting four dumbbell-shaped resonators and one U-shaped slot is analyzed. Simulated results point out that the characteristic of dual stopbands is better than the fundamental structure. Based on above implementation, a dual-band bandstop filter based on eight proposed dumbbell-shaped resonators and two U-shaped slots is proposed and fabricated. Two center frequencies at 4 and 6.5 GHz are reported, corresponding to the attenuation levels of 41.9 and 26.1 dB. The return losses of center frequencies are 0.04 and 0.20 dB, respectively, and the dual stopband bandwidths with 10 dB signal attenuation are 690 MHz and 250 MHz. In addition, two transmission poles at each stopband are induced for better selectivity. Owing to the symmetric dumbbell shape, the size of the filter gets reduced. It is simple to design and quite compatible with planar construction fabrication.

Compact wideband flexible monopole antennas are designed and analyzed for its performance for Body Centric Wireless Communications (BCWC). Two antennas with identical radiators on different substrates are designed and fabricated on polyamide and teslin paper substrates, deployinga modified rectangle-shaped radiator. With the aid of modifications in the radiating plane and defecting the ground plane, the polyamide based antenna is designed to operate between 1.8 and 13.3 GHz, and teslin paper based antenna is designed to operate between 1.45 and 13.4 GHz to cover the wireless communication technology frequencies and ultra-wideband range for various wireless applications. The reflection coefficient characteristics of the fabricated antennas on free space and on various sites of the body are measured and match reasonably well with the simulated reflection coefficient characteristics. The specific absorption rate (SAR) analysis is also carried out by placing the antennas on tissue layered model.

In this paper, a Multiple Split Ring Resonator (MSRR) based coplanar waveguide (CPW) fed antenna for 5.8 GHz RFID application is presented. The antenna has a compact size of 15 x 21 x 0.8 mm³. The proposed antenna is designed, fabricated and tested. The simulated results are discussed and in good compliance with the measured results. Split Ring Resonator (SRR) characteristics are also studied. The proposed antenna shows good performance at the measured resonance frequency of 5.75 GHz.

This letter presents a two-port dual-band multiple-input-multiple-output (MIMO) antenna, which is achieved based on a non-radiation passive circuit. The circuit is composed of two pairs of open-ended stubs and a transmission line connecting them. The decoupling condition of S₂₁ = 0 is deduced, thus a good isolation is achieved. Then this non-radiation circuit is further designed to be a structure with enough radiation without affecting the character of port isolation. Since the implementation of port isolation does not adopt complex decoupling network or decoupling structure, the process of design is simple and effective. The simulation and physical demonstration obtain good agreements for the proposed dual-band MIMO antenna.

In this paper, a circularly polarized antenna for Synthetic Aperture Radar (SAR) application is presented. The antenna is proposed to be implemented for the airborne SAR and the spaceborne SAR. To enhance the bandwidth of the antenna, the Circular-Ring-Slot (CRS) technique is implemented on the ground plane and in a square slot in the centre of the patch. In this antennas design, the model of the slot on the radiator is also investigated. The antenna is printed on NPC-H220A substrates with the dielectric constant of 2.17 and thickness of 1.6 mm. The resonant frequency of the antenna design sets at 9.4 GHz with the minimum requirement of the bandwidth of 800 MHz. The antenna design is produced under the -10 dB bandwidth of reflection coefficient, S₁₁ of approximately 27% (8.2 GHz-10.76 GHz) and left-handed circular polarization (LHCP). The gain of the antenna is 6.5 dBic and 12.7% (8.8 GHz-9.84 GHz) for the axial ratio bandwidth (ARBW). This paper includes the description and presentation of the completed discussion.

In this article, a theoretical analysis and design are presented for a Microstrip Patch Antenna (MPA) embedded with an inclined rectangular slot supported by a C-shaped Defected Ground Structure (DGS). Dual-band characteristics are achieved at 2.4 GHz and 2.6 GHz with a small frequency ratio of 1.08, which makes the proposed antenna useable for Wi-Fi and WiMAX applications. A theoretical analysis is also proposed for the designed antenna structure using modal expansion cavity model and equivalent circuit approach. The analyzed antenna design is fabricated, and it is found that measured results are in good match with theoretical and simulated results.

A compact dual-band inverted-F filtering antenna with good band-edge selectivity for modern wireless communication systems is presented in this paper. A novel dual-band filter based on open-loop dual-mode resonator loading a T-shaped stub and an inverted-F antenna (IFA) also with a T-shaped open stub are integrated together. The higher band is controllable easily by adjusting the dimension of the T-shaped stub, leaving the lower band unaffected. To minimize the dimension of the filtering antenna, the last stage of the filter is folded. A flat gain response is obtained with steep skirts at both band edges. Simulated and measured results show that the integration makes the proposed antenna operate at 2.4/3.7 GHz with compact size, good band-edge selectivity, and controllable higher band compared with the traditional IFA.

A dual-band shorted annular ring patch antenna with interference rejection at the horizon is presented for GPS timing applications. It is shown that the dimensions of the annular ring can be optimized to make a null in the RHCP pattern at low elevation near the horizon for all azimuth angles. This null attenuates interfering signals originating from ground based sources. The antenna achieves circular polarization utilizing radial shunted stubs. The effect of the stubs on the resonance is analytically derived and verified through simulations. A novel feed configuration that incorporates a coplanar waveguide transition improves the impedance match for both L1 and L2 GPS frequency bands compared to previous designs that present compromises between the feed impedance of the two bands. Additionally, since the shunted stubs reduce the number of required electronic components compared to other antennas with similar horizon nulling capability, the cost is reduced. A prototype antenna operating at GPS L1 and L2 bands has been fabricated and validated through measurements.

In this article, design and analysis of a dual-band ring dielectric resonator based radiator with circular polarization features is explored. The presented ring DRA is excited with the help of a tilted modified square-shaped aperture. Two important attractive features of present article are: (i) two radiating modes originated inside the ring DRA i.e. HEM11δ and HEM12δ mode; (ii) tilted modified square aperture generates circular polarized (CP) wave in both the operating frequency bands. For verifying the simulated results, practical model of the proposed antenna has been fabricated and verified. Experimental outcomes display that the proposed radiator functions over dual frequency bands i.e. 2.8-3.58 GHz and 5.5-5.92 GHz respectively. 3-dB axial ratio (AR) frequency ranges of proposed radiator are 2.8-3.2 GHz and 5.85-6.0 GHz, respectively. These appearances make it appropriate for some important wireless applications such as wireless LAN (2.4/5.2 GHz) and WiMAX (2.5 GHz) applications.

In this paper, a novel microwave planar resonant sensor is designed and developed for simultaneous detection of permittivity and permeability of an unknown sample using a nondestructive technique. It takes advantage of two-pole filter topology where the interdigitated capacitor (IDC) and spiral inductor are used for placement of a sample with significant relative permittivity and permeability values. The developed sensor model has the potential for differentiating permittivity and permeability based on the odd mode and even mode resonant frequencies. It operates in the ISM (industrial, scientific and medical) frequency band of 2.2-2.8 GHz. The sensor is designed using the full wave electromagnetic solver, HFSS 13.0, and an empirical model is developed for the accurate calculation of complex permittivity and permeability of an unknown sample in terms of shifts in the resonant frequencies and transmission coefficients (S₂₁) under loaded condition. The designed resonant sensor of size 44x24 mm² is fabricated on a 1.6 mm FR4 substrate and tested, and corresponding numerical model is experimentally verified for various samples (e.g., magnetite, soft cobalt steel (SAE 1018), ferrite core, rubber, plastic and wood). Experimentally, it is found that complex permeability and permittivity measurement is possible with an average error of 2%.

This paper describes the design of an experimental radio frequency (RF) heating system for efficiently heating waste activated sludge (WAS), a byproduct of wastewater treatment plants. Thermal pretreatment is used to increase the bio-gas yield from subsequent anaerobic processes which use WAS. The RF heating system operates at a frequency of 13.56 MHz and the frequency was selected based on a study of the electrical properties of WAS. RF heating has advantages over microwave heating including access to very efficient RF generators, and RF applicators can be designed to provide uniform heating through large load volumes, overcoming limitations of microwave heating which has a shallow penetration depth in the load. Experimental results for the RF heating system show a dc to RF power conversion efficiency of 85% and a power transfer efficiency from the amplifier to load of more than 86% over a temperature range from 20˚C to 120˚C.

Ground bounce noise (GBN) is a major concern in high speed electronic circuits. In this paper a Genetic Algorithm (GA) optimized electromagnetic band gap (EBG) structure is proposed for suppression of the GBN. The unit cell of the structure is comprised of several square patches, each having a dimension of 5 mm x 5 mm. The position of the square patches is optimized using the GA, such that the stopband is maximized. A single unit cell of the optimized structure is fabricated and tested for its stopband characteristics using the vector network analyzer (VNA). The structure is then tested for its signal integrity (SI) using the Agilent ADS software. The single unit cell of the optimized structure provides a wide band gap of 20 GHz with 30 dB isolation and a band gap of 17.4 GHz with 40 dB isolation. The results obtained are compared with the existing results. The optimized structure shows improved performance in terms of stop band gap and signal integrity (SI).