In this work, the design studies of a 60 GHz, 100 kW CW gyrotron have been presented. Mode selection is carefully studied with the aim of minimizing mode competition and to yield a perfect solid beam output through an RF window with a suitable dimpled-wall quasi-optical launcher. Cavity design and interaction computations are then carried out. In addition, preliminary design of the magnetron injection gun, magnetic guidance system, launcher, and RF window are presented. Thus, we present a feasibility study, which indicates that the operation of such a gyrotron is possible and can give a power in excess of 100 kW at an efficiency > 35%. As a part of this work, a complete Graphical User Interface package "GDS V.01" (Gyrotron Design Suit Ver.01) has been developed for the design and conceptualization of specific gyrotrons.
This paper presents a numerical simulation of the human head coupling with a Planar Inverted-F Antenna (PIFA) structure based on the Coupled Integral Equation/Method of Moment (CIE/MoM) approach to study the effects of the EM coupling on the antenna performance. A mix-potential integral equation (MPIE) for the surface current of PIFA structure and a volume electric field integral equation (VEFIE) for the head with mutual coupling terms are obtained. Finally numerical results will be presented at 900 and 1800 MHz for the antenna performance parameters. The validity of the proposed method is evaluated using the XFDTD software.
In this paper, we study tunable metamaterial structures whose unit cell has triangular split ring resonator and wire strip for S- and C-microwave bands. Three types of new metamaterials, concentric and non-concentric configurations, are designed, and their electromagnetic response is investigated. Constitutive and S parameters are computed using retrieval algorithm to demonstrate the properties of the proposed new metamaterial designs. In addition, the electric field distribution on the metallic parts of the structure is illustrated for one design of the each sample. It is shown that the studied new metamaterials exhibit double negative properties in the frequency region of interest. The main advantage of this study based on the proposed structures is having the tunability in terms of the substrate thickness and the possibility of pronounce loss reduction.
In this article we developed a new method of calculation of the active microwaves circuits in micro ribbon technology. This technique is based on the iterative method where localised auxiliary sources are introduced to model the active elements of the circuit (ultra high frequency diodes). To validate this work, the results obtained are compared with those obtained by the software momentum of advanced design system (ADS). We show primarily the interests and the operational limits of auxiliary source in the formulation of the considered problem.
Reliable performance of a component or structure depends on its pre-service quality and in-service degradation under operating conditions. The importance of Non-Destructive Testing and Evaluation is ever increasing, above all in ensuring pre-service quality and monitoring in-service degradation, in order to avoid premature failure of the components/structures. There are many Non-Destructive Techniques based on various physical principles. In this work, our main objective is the characterization of anomalies such as defects, stresses and microstructural degradations in materials. Particularly, in this work we propose a Finite Element Method based approach for modelling a fast and accurate evaluation of defects in metallic materials able to easily detect defects, aside from the orientation. Within this framework, the paper proposes the application of a magnetic field rotating perpendicularly to the analysed specimen. We discuss a few case studies, starting from numerical simulations and finally highlighting the importance of this approach in order to evaluate the structural integrity assessment.
This paper investigates an H-fractal wideband microstrip filter with multi-passbands and a tuned notch band for wireless communication frequencies. The four different filter configurations explored are: symmetric with zero offset, symmetric with nonzero offset, asymmetric with zero offset, and asymmetric with nonzero offset. The effect of H-fractal iterations, fractal scaling parameters, and stub offset on the filter's multi-passband response is presented. A comparison is made to a non-fractal straight stub filter of equivalent length showing improved passband bandwidth while maintaining the same overall response. Then an asymmetry is introduced into the fractal geometry to produce a tuned notch band in the second passband. Two fractal scaling factors are shown to aid in the tuning of the filter notch band. Finally, an asymmetric filter is fabricated on FR-4 substrate and experimentally verified, illustrating that the filter has multi-passbands and can find applications in WiFi/WiMAX transponders. The fabricated filter's first two passbands (with respect to S11 = -10 dB) are: from 2.09 GHz to 3.18 GHz (fractional bandwidth of 1.09 GHz, 41.36%) and from 4.1 GHz to 5.43 GHz (factional bandwidth of 1.33 GHz, 27.91%), both for WiFi applications along with a notch band (S21 = -3 dB) from 3.3 GHz to 3.94 GHz (factional bandwidth of 0.64 GHz, 17.67%) to suppress co-site WiMAX transmission. The measured data agrees reasonably well with the simulated filter response.
A new method is presented for analysis of transient electromagnetic fields in regular structures with abrupt discontinuities. The method is based on mode expansion of the fields in the Time Domain. The modes propagate independently in the regular parts of the structure and are coupled at the discontinuity. The main idea consists in solving 1D FDTD equations for each independent mode channel in the regular waveguides and using mode-matching at the junction cross-section in order to relate the mode amplitudes in all the channels at the same time instant via imposing boundary conditions. As examples the problems of pulse signal diffraction at a step discontinuity in a parallel-plate waveguide, diffraction at a junction of circular and coaxial waveguides, and pulse radiation of a bi-conical antenna are considered. The latter problem is treated as a junction of two conical lines (one of which is the free space) that are regular in spherical coordinates.
Adaptive Neuro-fuzzy systems constitute an intelligent systems hybrid technique that combines fuzzy logic with neural networks in order to have better results. A study is presented to forecast the relative magnetic permeability using ANFIS. The global electromagnetic parameter, namely, the magnetic induction has been used as input to estimate the relative magnetic permeability. In this exceptional research, finite element simulations are carried out to build up a database which will be used to train ANFIS network. The ANFIS approach learns the rules and membership functions from training data. The hybrid system is tested by the use of the validation data. Performance of the trained ANFIS network was compared with the multilayer feed forward network model and experimental results. The results show the effectiveness of the proposed approach in solving inverse electromagnetic problem.
In this paper a multifunctional microstrip antenna is designed, fabricated and experimentally verified for operation in AWS, GSM, WiMAX and WLAN bands. This microstrip patch antenna has two U-shaped slots to achieve the dual wideband operation required to meet these specifications. The dimensions and locations of the U-slots are designed appropriately. The thick substrate used here helps in integrating the antenna with the existing aircraft panel material while achieving wide bandwidths. Experimental results of this single feed antenna indicate that it meets all current requirements for in-cabin wireless communication needs.
A capacitive method for measuring hand grip position on a mobile phone equipped with a dual-band planar inverted-F antenna (PIFA) and a monopole antenna was studied using different electrode arrangements. A capacitive sensor with a dual-electrode configuration and an antenna-integrated capacitive sensor for hand grip recognition were developed. The sensitivities of the sensors were measured along the front, side and back of the phone. The dual-electrode sensor configuration exhibited its best sensitivity of 29 fF at the bottom end of the phone. The PIFA antenna-integrated sensor proved to have sensitivity of 420 fF and the monopole antenna-integrated sensor had sensitivity of 115 fF, making them both reasonable solutions for hand grip sensors in mobile applications.
Shielding prevents coupling of undesired radiated electro-magnetic energy into equipment otherwise susceptible to it. In view of this, some studies on shielding effectiveness of different shields against angle of incidence with conductors and conductive polymers using plane-wave theory are carried out in this paper. The plane wave shield- ing effectiveness of new combination of these materials is evaluated as a function of angle of incidence for Single, Double and Laminated Shields. Conductivity of the polymers, measured in previous investigations by the cavity perturbation technique, is used to compute the overall reflection and transmission coefficients of single and multiple layers of the polymers. With recent advancements in synthesizing stable highly conductive polymers, these light-weight mechanically strong materials appear to be viable alternatives to metals for EM1 shielding. The analysis is done at a particular frequency for all three types of shields.
Although the discontinuity structures in the microstrip transmission lines such as a gap and bend have been largely studied, the three-dimensional edge effects, skin effects and metal losses have hardly been analyzed. In this paper, modeling of transmission line with bend and gap discontinuity with equation based process technology independent method are developed. The effect of the signal layer thickness is fully included in the model. Gap model is verified with EM simulation and implemented in BiCMOS technology on Silicon substrate. The bend is modeled with transmission line with effective length for the discontinuity area, and the equations have been generated. The bend model is compared with EM simulations, existing bend model generated with curve-fitted method and measured results. Gap and bend are enabled as library device in a 0.13 μm SiGe BiCMOS process design kit. Both bend and gap device have a scalable layout pattern and a schematic symbol, which allows users to choose them with different dimensions and metal stacks. In addition, the models can be migrated into other process technologies with different metal options. Very good match have been achieved among model, EM simulation and measurements for different process technologies and metal stacks.
This paper estimates separately the components of scattering waves generated in cylinder-body model for body area networks. For the evaluation, scattering field formulations in relation to uniform cylinder- and slab-body models are provided, and the reliability of the analyses is testified by the comparison with results computed by the finite-difference time-domain (FDTD) method. Creeping waves, cylinder leaky waves, and cylinder guided waves, which are created only in cylindrical structure, are extracted quantitatively by contrasting the scattering waves that are calculated with the two body models. In addition to the extracted waves, other components of scattering waves such as reflected waves, transmitted waves, surface waves, leaky waves, and guided waves also are examined. From evaluations with various operating frequencies and thicknesses of the body model, it is confirmed that reflected waves have the most influence on electrical characteristics of a source. Moreover creeping waves and cylinder leaky waves are generally dominant at the opposite side of the cylinder when a source is located near cylinder surface. Furthermore, the existence of creeping waves with low attenuation in the vicinity of cylinder surface is demonstrated by electric field intensities calculated by varying the observation point along cylinder axis.
Statistical characteristics of scattered electromagnetic waves by turbulent magnetized plasma slab with electron density and magnetic field fluctuations are considered via the perturbation method and boundary conditions. Magnetic field fluctuates both in magnitude and direction. Analytical expressions for the component of scattered electric field, correlation functions of the amplitude and phase fluctuations, and also the phase structure function for arbitrary correlation functions of fluctuating plasma parameters are derived. The obtained results are valid for near and far zones. Under equal conditions, at strong magnetic fields, electron density fluctuations play the important role and in this case the imposed magnetic field decreases fluctuation intensity of the ordinary and extraordinary waves. Numerical calculations of statistical characteristics of scattered radiation were carried out for anisotropic Gaussian correlation function for electron density fluctuation and correlation tensor of the second order for the fluctuation of an external magnetic field. The phase portraits of correlation functions of the amplitude and phase fluctuations are constructed.
In this paper, synthesis of superconducting circular antennas mounted on circular array is designed by the combination of a method based on particle swarm and full-wave method. Full-wave method is used for computing the resonant frequency, the bandwidth, radiation pattern and efficiency of a perfectly superconducting, or an imperfectly conducting circular microstrip, which is printed on isotropic or uniaxial anisotropic substrate. Particle Swarm Optimization (PSO) has been used to obtain the minimum side lobe level (SLL) of circular array, by varying element excitations and/or positions. Numerical results concerning the effect of the parameters of substrate and superconducting patch on the antenna performance are presented and discussed. It is found that superconducting circular antenna could give high efficiency. Also, results show the efficiency of PSO in producing desired radiation characteristics and are in good agreement with previously published data.
Radio astronomy has a wide electromagnetic spectrum. It is based on antennas, electronics, software etc., and thus highly technical. The radio data obtained from distant objects like stars, galaxies, pulsars etc. are useful for studying the Universe. Many of the radio emissions, especially from the Sun have been studied over decades for understanding the ionosphere and its effects on radio communication. Untill now, this subject of radio astronomy has found its existence among those who are associated with astronomy and possessing at least some knowledge of RF engineering. A requirement of a review literature on this subject with technical details is felt by many working engineers and scientists. It is thus proposed to write a series of articles covering the subject from both engineering and scientific angles. This paper is the first of this series. It focusses on the foundation of this subject and briefly describes the supersynthesis technique. Overview of various concepts like cosmic radio signals, continuum, synchrotron emission etc., general instrumentation for radio astronomy, imaging techniques and radio interference have have been presented.
Utilization of wearable textile materials for the development of microstrip antenna segment has been rapid due to the recent miniaturization of wireless devices. A wearable antenna is meant to be a part of the clothing used for communication purposes, which includes tracking and navigation, mobile computing and public safety. This paper describes design and development of four rectangular patch antennas employing different varieties of cotton and polyester clothing for on-body wireless communications in the 2.45 GHz WLAN band. The impedance and radiation characteristics are determined experimentally when the antennas are kept in flat position. The performance deterioration of a wearable antenna is analyzed under bent conditions too to check compatibility with wearable applications. Results demonstrate the suitability of these patch antennas for on-body wireless communications.
We numerically compare the mode birefringence and confinement loss with four patterns of index-guiding photonic crystal fibers (PCF) using the finite element method. These PCFs are composed of a solid silica core surrounded by different sizes of elliptical air holes and a cladding which consist of the same elliptical air holes in fiber cladding with tetragonal lattice. The maximal modal birefringence and lowest confinement loss of our proposed case A structure at the excitation wavelength of λ=1550 nm can be achieved at a magnitude of 5.3×10-2 (which is the highest value to our knowledge) and less than 0.051 dB/km (an acceptable value less than 0.1 dB/km) with only four rings of air holes in fiber cladding, respectively. The merit of our designed PCFs is that the birefringence and confinement loss can be easily controlled by turning the pitch (hole to hole spacing) of elliptical air holes in PCF cladding.
This paper proposes a metamaterial reflective surface (MRS) as a superstrate for a single-feed circularly polarized microstrip patch antenna (SFCP-MPA). It illustrates a simultaneous enhancement on antenna gain, impedance bandwidth (ZBW) and axial-ratio bandwidth (ARBW) by adding the MRS atop the SFCP-MPA. The MRS can enhance the ZBW and ARBW by 3.5 and 9.9 times, respectively, compared to the circularly polarized patch source. Moreover, the gain of the CP-MPA with the MRS is 7 dB higher than that of the conventional CP-MPA. The small spacing between the MRS and patch source is another merit in the present design, which is as low as λo/16 as it results in a low-profile antenna design that well suits modern wireless communications.
In this paper, a new simple design procedure of multi-frequency unequal split Wilkinson power dividers (WPDs) is presented. The procedure is based on using N-sections of transmission line transformers, instead of the conventional quarter-wave WPD branches, to realize a WPD that operates at N frequencies. Good isolation is achieved by using lumped resistors without any extra modification to the conventional structure of WPDs. The analysis, design procedure, and mathematical expressions are presented for arbitrary design frequencies, and arbitrary power split ratio. For verification purposes, a 1:2 dual-frequency, a 1:2 tri-frequency, and a 1:2 quad-frequency WPDs are designed and fabricated. The measured results show good agreement with those obtained using the presented design methodology and with full-wave simulated results.