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The simplest Micro-Ring Resonator consists of an input–output directional coupler connected into itself through a feedback loop. We show that a magneto-optical coupler exhibiting a nonreciprocal phase shift is enough to render the whole structure nonreciprocal, even with an otherwise reciprocal loop. We illustrate this effect by considering a planar (slab) coupler made of bigyrotropic waveguides submitted to a suitable external magnetization; its scattering parameters are derived analytically in the frame of Coupled Mode Theory. Including the modal dispersion, it is possible to adjust the dimensions and/or the operating wavelength in order to design very specific regimes, either in absorption, amplification or emission, from a rather trivial unidirectional behavior to the subtler case of well-balanced interdigitated frequency combs—circulating both ways, but separated by exactly one half of a Free Spectral Range. [ABSTRACT FROM AUTHOR]

This research discusses about the effect of adding high content cashew shell biochar (CSB) nanoparticle onto the carbon fibre–reinforced epoxy resin composite in electromagnetic interference (EMI) shielding behaviour. The primary goal of this research was to study the EMI shielding behaviour of CSB particle addition in carbon-epoxy composite at elevated frequency ranges up to 18 GHz. The shielding epoxy composites were prepared via hand layup method followed by characterized in accordance to ASTM standards. It is noted that the addition of CSB particle increased the mechanical properties of carbon-epoxy composite up to 226 and 298 MPa in tensile and flexural properties of composite designation CS4. The scattering parameters of tested composites showed highest reflection, multi-reflection and absorption behaviour for high CSB content in composite. It is further noted that the shielding effect increased with the volume of CSB particle. A highest shielding of − 48.6 dB was observed for composite designation CS5 at 18 GHz. These EMI shielding behaviours improved biochar-epoxy composites which could be used in radar, telecommunication, defence and signal processing devices where the effect of interference needs to be reduced. [ABSTRACT FROM AUTHOR]

The effect of introducing high-content SiC nanoparticle to a carbon fibre reinforced epoxy resin composite on electromagnetic interference (EMI) shielding behavior is discussed in this study. The main purpose of this work was to investigate the EMI shielding performance of SiC particle addition in carbon epoxy composites at high frequencies up to 18GHz. Hand layup process was used to make the shielding epoxy composites, which were then characterized according to ASTM standards. It was found that adding SiC particles to a carbon-epoxy composite improved its mechanical characteristics. For high SiC content in composites, the scattering characteristics showed the maximum reflection, multi reflection, and absorption behavior. It was also found that the shielding effect increased as the volume of SiC particle increased. At 18GHz, composite designation N5 had the maximum shielding of −49.6 dB. These enhanced SiC-epoxy composites with improved EMI shielding properties might be employed in radar, tele-communication, military, and signal processing equipment where interference is a challenge. [ABSTRACT FROM AUTHOR]

In this paper, using in-depth simulations and measurements, a simple and compact design is engineered for making a circular ring microstrip patch antenna radiating element which is suitable for different ultra wide band (UWB) applications. This design approach is different because it has not utilized the usual method of using a set of electromagnetic equations and calculations to make the radiating antenna. Measurements and simulations were performed on Microwave CST. Using this measurement engineering approach, novelty of proposed antenna structure is obtained by making the required changes in the ground plane. The measurements showed that truncating the ground plane by a square shape structure of 2.5 mm by 2.5 mm size at the feed point was practically significant to provide an impedance bandwidth S 11 < - 10 dB ranging from 2.75 to 32.035 GHz with a VSWR which is less than 2. For this entire bandwidth the directivity has shown a variation from 0.8 to 7.9 dBi. The compact size (33 mm × 28 mm × 1.57 mm), low design complexity, very high bandwidth, good directivity and satisfying VSWR has made this antenna unique among all previously presented UWB antennas. [ABSTRACT FROM AUTHOR]

Modern gyrotron beam tunnels are rather complicated structures designed to enhance the suppression of the parasitic oscillations, which may be excited there. In some beam tunnel designs, azimuthal corrugations are engraved on their walls to further improve the suppression of these oscillations. In this work, we investigate the effect of the geometrical properties of the corrugations on the propagation characteristics of TE modes for the simplified model of a smooth waveguide with an azimuthally corrugated region. For this structure, the scattering parameters are calculated and the mode conversion is investigated with the in-house FDTD code COCHLEA. [ABSTRACT FROM AUTHOR]

This paper gives an overview of optimizing wireless power transfer systems using magnetic coupling. Optimization aims to maximize either the power transfer efficiency or the transferred power. The resulting load calculation and matching strategies are revisited. Moreover, the coupling system is described, starting with its equivalent circuit and scattering parameters. In addition to wireless power transfer, communication in RFID and NFC systems and its frequency characteristics and bandwidth issues are highlighted. The focus in this paper is on load modulation for data transfer between a tag and reader. For this purpose, subcarrier voltages are derived using time-domain as well as frequency-domain signal analysis. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR)–based structures are finding important applications in sensing biological as well as inorganic samples. In SPR techniques, an angle-resolved reflection (R) profile of the incident light from a metal-dielectric interface is measured and the resonance characteristics are extracted for the identification of the target sample. However, the performance, and hence the applicability of these structures, suffers when the weight and concentration of the target samples are small. Here, we show that SPR-based sensors can create strong magnetism at optical frequency, which can be used for the detection of target samples instead of using the conventional R profiles, as the magnetic resonance varies depending on the refractive index of the target sample. Using scattering parameters retrieval method, we computationally find out the effective permeability (μeff) of a SPR sensor with a structure based on Kretschmann configuration, and use it to calculate the performance of the sensor. A comparison with the conventional technique that uses R profile to detect a target sample shows a significant increase in the sensor performance when μeff is used instead. [ABSTRACT FROM AUTHOR]

In this study, the production and the EM-wave absorption properties of the polymer nanocomposites were investigated. The two- and three-phase polymer nanocomposites on the base of the PVDF matrix, multi-walled carbon nanotubes, and magnetite nanoparticles were produced by the in-situ method. With the help of XRD and SEM methods, produced nanocomposites were analyzed. Measurement of the absorption coefficient of the nanocomposites with different filler concentrations shows that the maximum effect was obtained for the nanocomposite, with 20 wt% of MWCNT in the PVDF matrix. Very close value to maximum was also, got for a nanocomposite, which contained 10 wt% of MWCNT and 5 wt% of Fe3O4 in the PVDF matrix. These results were related to energy dissipation at the high-frequency region, depending on the components fraction in the nanocomposites. [ABSTRACT FROM AUTHOR]

The electric and magnetic properties of zinc oxide (ZnO) nanoparticles (NPs) have been investigated through waveguide measurement in the x-band. Because of the advantages of the x-band, the application of the Nicolson–Ross–Weir (NRW) method was able to be used to extract the mentioned characteristics from the scattering parameters. The advantages of the NRW method are that it is fast and applicable to waveguides and coaxial lines, and it can also be used to determine both the permittivity and permeability. Therefore, the results show two main resonant frequencies at 9.279 GHz and 10.46 GHz. The response of the ZnO NPs for an incident electromagnetic wave implies that both capacitance and inductance behaviors can be observed. Finally, the obtained magnetic susceptibility characteristic confirms that the ZnO NPs are ferromagnetic over the frequency range from 8 GHz to 8.265 GHz and paramagnetic up to 12.5 GHz. [ABSTRACT FROM AUTHOR]

A High Temperature Superconductor filter operating in the C-band between 4200 and 5600 MHz has been developed for one of the radio astronomical receivers of the Sardinia Radio Telescope. The motivation was to attenuate an interference from a weather radar at 5640 MHz, whose power level exceeds the linear region of the first active stages of the receiver. A very sharp transition after the nominal maximum passband frequency is reached by combining a 6th order band-pass filter with a 6th order stop-band. This solution is competitive with an alternative layout based on a cascaded triplet filter. Three units of the filter have been measured with two different calibration approaches to investigate pros and cons of each, and data repeatability. The final performance figures of the filters are: ohmic losses of the order of 0.15-0.25 dB, matching better than −15 dB, and −30 dB attenuation at 5640 MHz. Finally, a more accurate model of the connection between external connector and microstrip shows a better agreement between simulations and experimental data. [ABSTRACT FROM AUTHOR]

An approach to model the parameters of LNA which is ideal for GLONASS navigation system. To design LNA, multilayer perceptron architecture is used. The parameters of LNA are calculated using Levenberg Marquardt Backpropagation Algorithm for the frequency range 300 MHz to 18 GHz. ANN model is trained using Agilent MGA 71543 Low Noise Amplifier datasheet and this model shows high regression. The smith and polar charts are plotted for frequency range 300 MHz to 18 GHz and parameters are calculated for center frequency of L1 band of GLONASS, which is 1.602 GHz. [ABSTRACT FROM AUTHOR]

We characterize a system consisting of a two-mode waveguide coupled to a single-mode microring resonator possibly presenting a nonlinear response of Kerr type. By using the scattering parameter formalism extended to the multimode domain, we show that in the linear regime and for an ideally transparent medium, each resonance of the system can be exploited to perform complete even-to-odd (respectively, odd-to-even) modal conversion. Moreover, when the Kerr nonlinearity is effective, the microring enables a power-dependent modal switching mediated by phase bistability. Thanks to its mode-processing capabilities, this configuration is suitable to find application as a functional building-block in mode-division multiplexing (MDM) photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Paper presents an ANN modeling of microwave LNA for the global positioning front end receiver, operating at 1.57542 GHz. To design LNA, multilayer perceptron architecture is used. The scattering parameters of LNA are calculated using Levenberg Marquardt Backpropagation Algorithm for the frequency range 100 MHz to 8 GHz. The inputs given to this architecture are drain to source current, drain to source voltage, temperature and frequency and the outputs are maximum available gain, noise figure and scattering parameters (magnitude as well as angle). ANN model is trained using Agilent MGA 72543 GaAs pHEMT Low Noise Amplifier datasheet and this model shows high regression. The smith and polar charts are plotted for frequency range 100 MHz to 8 GHz. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of verification artifacts in WR-03 waveguides. The waveguide verification artifacts include a cross-guide and a custom-made circular iris section. The investigation involves the transmission loss uncertainty analysis of the verification artifacts for vector network analyzer (VNA) waveguide systems operating at millimeter wavelengths. The measurement errors due to the dimensional tolerances and the flange misalignment are predicted by using a commercially available electromagnetic software package. The data analysis is carried out for complex-valued scattering parameters (S-parameters). The uncertainty due to different error sources is computed according to the Law of Propagation of Uncertainty. The real and imaginary data along with the associated uncertainties are converted to magnitude and phase representation via linear propagation of uncertainties. The experimental results are also compared with simulated results. [ABSTRACT FROM AUTHOR]

For high quality performance, future efficient wireless communication systems require a Broadband Amplifier in the frequency range under consideration. When such an amplifier is plugged into the measuring path it would enable the system to perceive even the weakest of signals. To achieve this, a new Scattering-parameter model that is valid for a wide frequency range has been developed for microwave analysis of a pseudomorphic high electron mobility transistors (pHEMT). The developed neural network model is used for designing a pHEMT power amplifier. The calculated S-parameters, gain and minimum noise figure from the artificial neural networks (ANN) model are the parameters used to design the low noise pHEMT power amplifier. The various gains so obtained from the S-parameters have been plotted with the frequency and it was found to yield a close fit to the simulated model. Neural network training has been done using Levenberg-Marqaurdt back propagation algorithm implemented in ANN toolbox of MATLAB software. All the results have been compared with the experimental data that showed a close agreement and validated our model. The calculated S-parameters, gain and minimum noise figure from the ANN model are the parameters used to design a stabilized and matched LNA. [ABSTRACT FROM AUTHOR]

On May 26, 2011 Mitsubishi Electric Corporation released its GaN HEMT power amplifier for C-band satellite communication, which offers a power-added efficiency (PAE) of 67%. Frequency and bias dependence of scattering parameters of microwave transistors can be successfully modeled by artificial neural networks (ANN). Dependence of angle of a scattering parameter may result in inappropriate modeling accuracy in the vicinity of the frequency, when sharp changes occur. In this paper we are discussing pre-processing of the training data in order to make modeling accuracy better. The proposed approach is illustrated by a suitable example. By doing so we are proposing to design an onboard low noise Amplifier for Mobile Satellite Receiver. [ABSTRACT FROM AUTHOR]

The constitutive parameters of a metamaterial slab showing negative refractive index over the 9-12 GHz frequency range are unambiguously retrieved from complex scattering parameters upon using the phase unwrapping method. Such a technique relies on properly adding to the phase of the complex transmission coefficient a stepwise function constructed from critical frequencies at which the phase of the transmission coefficient reaches ∓ π. [ABSTRACT FROM AUTHOR]

Inherent to transmission/reflection measurement methods and posed by the multiple-valued logarithm function of the complex transmission coefficient, the phase ambiguity problem is solved by the phase wrapping technique. Here extended and generalized, the proposed technique relies on properly adding to the phase of the complex logarithmic function a stepwise function built in from the resonance frequencies at which the phase of the transmission coefficient reaches ±π. In a concrete example the method is illustrated by correctly retrieving from complex scattering parameters the constitutive parameters of a highly-dispersive medium (distilled water) over the 0-250 GHz frequency range. Implication of a mathematically negative wavelength is also discussed. [ABSTRACT FROM AUTHOR]

The effects of direct-current (DC) stress on GaN high-electron-mobility transistors (HEMTs) are investigated by means of numerical simulations, by which the creation of an acceptor trap in the AlGaN barrier layer was correlated to the observed experimental degradation. An increase in the trap concentration induces a worsening of the saturated current I, transconductance g, and output conductance g. An increase in the length of the trapping region induces a degradation of I and g, but can reduce g. Analysis of scattering parameters in the saturation region shows that the cutoff frequency f matches the trend of g. [ABSTRACT FROM AUTHOR]

The method extracting the electromagnetic parameters from scattering coefficients was studied in this paper. The Support Vector Machine (SVM) method is used to solve the inverse problem of parameters extraction. The mapping relationship is set up by calculating a large number of S parameters from the samples with different permittivity by using transmission line theory. The simulated data set is used as training data set for SVM. After the training, the SVM is used to predict the permittivity of material from the scattering coefficients. [ABSTRACT FROM AUTHOR]

We investigate the properties of out-of-phase coupled periodic waveguides (CPW) in the frame of a rigorous coupled-mode theory (CMT), with special emphasis on internal symmetries at the scale of a unit cell. Specifically, we demonstrate an exact mathematical equivalence between the continuously distributed system and its discrete counterpart, made of four-port networks interconnected by segments of transmission lines. [ABSTRACT FROM AUTHOR]

In this paper, the modified matrix pencil (MMP) method is used in the finite difference time domain (FDTD) method to eliminate the late time instability of time domain responses when analyzing the novel microstrip circulator with a magnetized ferrite sphere. The frequency dependent scattering parameters: reflection, isolation and insertion parameters of the microstrip circulator calculated over a wide band of frequencies with this hybrid method are compared with that obtained by direct FDTD method which agree well with the experimental results. [ABSTRACT FROM AUTHOR]