The electro-magnetic torque production in the reluctance machine is highly influenced by the magnetic linkages in the air-gap area. The conventional machines derive the drawback of reduction in the air-gap area to a minimal due to influence of mechanical unbalancing thereby restricting the effective energy conversion area. In order to increase the magnetic linkage area the dual-air-gap structure is introduced. The dual-air-gap structure is realised through the division of the magnetic circuit area into two-air-gap while still maintaining the net air-gap length value. A double-rotor with single-stator structure is used to attribute the above concept. The electro-magnetic analysis of such a structure is developed and investigated through numerical analysis. In order to validate the proposed structure the electro-magnetic characteristics are compared with that of the conventional structure at similar operating conditions. The maximum torque generated by the selected dual-air-gap structure is 1.7549 Nm and for conventional structure is 1.2723 Nm. The evaluation of the proposed machine is done at the same operating conditions and it is found that the dual-air-gap structure exhibit 65% increase in average torque value in comparison with that of the conventional single-air-gap structure.

A novel approach for the design of a compact multiband monopole antenna for improving radiation characteristics at higher resonant frequencies is presented. The proposed structure consists of a conventional printed monopole loaded with spiral ring resonators and fed by microstrip. When at higher resonant frequency, the electrical length of the conventional monopole antennas is relatively large and the surface currents distribute on the patch periodically which will degrade the omnidirectional property. To achieve good radiation characteristics at the upper bands, two spiral ring strips are inserted into the microstrip line on the different layer and connected through via hole. Thus, the direction of surface currents on the spiral ring strips changes with the alteration of spiral structure and their effects on the radiation pattern are reduced. The radiation pattern is mainly contributed by the surface current on the microstrip line and very good stable radiation pattern can be obtained within all the operating bands. In comparison to the previous printed strip monopole structures, the miniaturized antenna dimension is only about 28 mm×20 mm×1 mm. The experimental results show that the proposed antenna can provide operating bands which meet the required bandwidths specification of 2.4/5.2 GHz WLAN and 3.5 GHz WiMAX standard. Detailed design considerations of the proposed antenna are described, and both the simulated and measured results of the proposed antenna are also presented and discussed.

In this paper, a novel compact quadruplexer is implemented by using slotline stepped impedance stub loaded resonators (SISLRs) in ground plane. Four folded dual-mode slotline SISLRs with one input and four output coupled line structures are designed at different frequencies for the quadruplexer operation. By properly adjusting the geometrical parameters of a single dual-mode slotline SISLR, its first two resonant frequencies can be controlled, and thus it can be utilized to implement a second-order bandpass filter when these resonant frequencies are suitably assigned. Furthermore, because the proposed quadruplexer utilizes the distributed coupling technique, a small circuit size can be obtained. As a result, the proposed quadruplexer occupies an extremely small area, i.e., 0.22λ₀ × 0.25 λ₀(0.36λ_g × 0.41λ_g). Finally, good agreement between measurement and EM simulation verifies the design method successfully.

In this work a non-linear efficiency optimization method for its application to an Injection-Locked High Efficiency Voltage Controlled Oscillator is presented. The proposed approach is based on the control of the harmonic content of the oscillator autonomous signal, which is accomplished through the use of an Auxiliary Generator and several multi-harmonic loads based on Arbitrarily Width-Modulated Microstrip Lines. The presented technique has been applied to the design of a 2.5 GHz high efficiency Voltage Controlled Oscillator, which has been manufactured and experimentally characterized, obtaining a good agreement between the simulated and measured results.

This paper presents a simple mathematical model to determine the force, stiffness and moment parameters in Permanent Magnet (PM) bearings made of radial magnetized ring magnets using Coulombian model and vector approach for five degrees of freedom. MATLAB codes are written to evaluate the bearing characteristics for three translational (x, y and z) and two angular (ξ and γ) degrees of freedom of the rotor magnet. The results of the mathematical model are compared with the results of Finite Element Analysis (FEA) using ANSYS and experiments for a PM bearing with one ring pair, thereby the presented mathematical model is validated. Furthermore, the PM bearing with three ring pairs with alternate radial polarizations are analysed by extending the presented mathematical model and also using ANSYS. Finally, the 5×5 stiffness matrix consisting of principal and cross coupled values is presented for the elementary structure as well as for the stacked structure with three ring pairs.

A compact dual-band band-pass filter is proposed in this paper. The central frequencies of the passbands are around 2.46 GHz and 5.86 GHz. There are two resonators located at the top side layer and the bottom side(the CPW) layer, respectively. Dual-resonance operation usually needs two resonators on the same layer to generate two passbands simultaneously. However,in this paper the size can be reduced efficiently by connecting resonators at two layers through via-holes to implement dual-band performance. Furthermore, the stop-band for this novel filter with T slot-line, L-line and rectangular micro-strips can be extended to 30 GHz. To verify the feasibility of the design above, a dual-band band-pass filter has been implemented on a Rogers RT5880 substrate (thickness is 0.508 mm). This filter with passbands operated at 2.46 GHz and 5.86 GHz can finely meet the IEEE 802.11 n wireless local area network (WLAN) bands requirements.

Mechanical distortions of phased array antennas make transmit pattern distort. The transmit pattern cannot be simply calibrated by compensating the position error of each element since the effect of the mechanical distortions is angle-dependent. To solve this problem, we treat the element position errors measurement as prior knowledge and propose a knowledge-aided (potentially cognitive) transmit pattern design method. When the mechanical distortions occur, the cognitive transmit pattern can still place pattern nulls in the directions of interferences while preserving the main beam response of the target of interest. The proposed method is validated by simulation results.

Based on quantum Stokes operators and non-Kolmogorov spectrum model of index-of-refraction fluctuation, the analytical formulas for the quantum degree of depolarization of quantization Hermite-Gaussian (QHG) beams propagating in a turbulent atmosphere slant channel are derived. The nonclassical polarization properties of QHG beams propagating in turbulent atmosphere are studied numerically. It is found that the polarization fluctuations of QHG beams are dependent of the turbulence factors such as spectrum powerlaw exponent, refractive index structure parameter at the ground and zenith angle. The degree of depolarization of QHG beams has a saltation and reaches the minimum value at spectrum power-law exponent α = 11/3, the refractive index structure parameter at the ground of the turbulent atmosphere slightly affects the polarization degree of QHG beams which have travelled a long distance, and the change of polarization degree decreases with the increasing zenith angle. Furthermore, the numerical simulations show that QHG beams with higher photonnumber level, lower beam order, shorter wavelength are less affected by the turbulence. These results indicate that One can choose low-order QHG beams with wavelength λ = 690 nm as optical carrier, increase photon number, set the size of transmitting aperture ω₀ as about 0.1 m, and detect communication signals at the central region of beams to improve the performance of a polarization-encoded free-space quantum communication system.

A multi-band ferrite-based metamaterial has been investigated by experiments and simulations. The negative permeability is realized around the ferromagnetic resonance (FMR) frequency which can be influenced by the saturation magnetization 4πM_s of the ferrites. Due to having multiple negative permeability frequency regions around the multiple FMR frequencies, the metamaterials consisting of metallic wires and ferrite rods with various 4πM_s possess several passbands in the transmission spectra. The microwave transmission properties of the ferrite-based metamaterials can be not only tuned by the applied magnetic field, but also adjusted by the 4πM_s of the ferrite rods. A good agreement between experimental and simulated results is demonstrated, which confirms that such a ferrite-based metamaterial possesses a tunable multi-band behavior. This approach opens a new way for designing multi-band metamaterials.

In this study, a novel dual band-notched ultra-wideband (UWB) antenna has been proposed and discussed. The proposed antenna is fed by a micro-strip line and in the square-etched radiation patch a T-shape parasitic stub is attached. On the other hand, a pair of parasitic parallel micro-strip lines are also added on the ground plane, one of which is shorted to the radiation patch by a short-pin through dielectric substrate. The two parasitic units are to achieve band-notched characteristics at 3.3-3.7 GHz and 5.15-5.85 GHz, respectively. In order to realize impedance matching over the ultra-wideband, two arc-shape cuts are made symmetrically at the junction of feed-line and radiation patch. The simulated and measured results, including return loss, radiation pattern, group-delay and peak gains are in good agreement with theory analysis which validates our design concept.

This work focuses on the development of multiscale meshless technique in area of scattered fields from paramagnetic scatterers. The radial point interpolation method (RPIM), as the most common meshless technique, is employed for above purpose. Due to high frequency analysis, some special considerations must be applied, particularly in subdomains near the incident face. So, to ensure the accuracy, a multiscale meshless technique in wavelet frames sounds necessary. Simulating the scatterers using above method, specifically an elliptic paramagnetic scatterer, shows some efficient aspects such as less computational time and more precision compared with some other numerical methods.

The paper deals with the design and optimization of a novel magnetic switchable device based on Halbach array. The magnetic field in air gap is adjustable by rotating the center axis of adhesion mechanism so that the magnetic adhesion force is variable, and it is convenient for device to adsorb on and detach from the ferromagnetic workpiece or surface. The magnetic field model is established by Fourier series method, and the optimal dimensions of configuration are obtained by finite element parameter approximation method for best performing design. The magnetic force of novel optimal device is measured, and a good agreement between simulation and measurement is found. The results are compared to the traditional mechanism, and it is shown that the utilization ratio of magnets of novel optimal mechanism is 2.2 times larger than the H-type one with the same usage of magnets, while its consumption of soft iron is only 12.7% of the H-type one.

An asymmetric coplanar waveguide (ACPW)-fed zeroth-order resonant (ZOR) antenna with extended bandwidth is investigated. By embedding a strip connected between the metallic patch and an ACPW ground plane, another resonant frequency at 2.53 GHz is achieved. The bandwidth enhancement of designed antenna can be obtained when the zeroth-order resonant frequency and the resonant frequency at 2.53 GHz are merging together. The size of the antenna is only 15×22×0.8 mm³ with simple planar structure. A prototype of the proposed antenna has been constructed and experimentally studied. The measured results show that operating bandwidths with 10 dB return loss are about 510 MHz (2.49-3.0 GHz), the simulated peak gain of 1.59 dBi at 2.68 GHz, which is suitable for WiMAX (2.5 GHz-2.69 GHz) application.

In this paper, a novel compact ultra-wideband (UWB) microstrip bandpass filter (BPF) with a notched band using the proposed multi-stub loaded ring resonator (MSLRR) is presented. The MSLRR is constructed by loading four open stubs in a ring resonator, i.e., one pair of high-impedance stub at the top side and another two low-impedance stubs at the bottom side locations. Five modes, including two odd modes and three even modes, could be designed within UWB band. Moreover, two transmission zeros (TZs) are generated by the ring structure, leading to a quasi-elliptic function response that enhances the selectivity significantly. Two slotline split-ring resonators (SRR) are used to create a narrow notched band at 8.3 GHz. The simulated and measured results are in good agreement and show good in-band filtering performance and sharp selectivity.

This work presents a methodology for the development of microwave systems and circuits. Starting from the system decomposition, the proposed method is aimed at estimates the requirements of each component of the system taking into account the effects on the whole system and the interactions with the others microwave components. The obtained requirements are then used to design or optimize each device with standard design methodologies or CAD tools. The problem is recast as an optimization one by defining a suitable cost function able to take into account the interactions between all the components of the system. The cost function is then minimized with an evolutionary optimization technique, namely the particle swarm optimizer. The obtained preliminary results, concerning the design of a broad-band bidirectional amplifier, demonstrate the potentialities of the proposed approach.

In a recent study, we proposed improved quasi-static expressions for the electromagnetic field components excited by a vertical electric dipole lying on the surface of a flat and homogeneous lossy half-space. The present paper introduces an analytical approach to derive analogous formulas for the case of the horizontal electric dipole. The procedure is based on the expansion of the integral representations for the fields into power series of the ratio between the wavenumbers in free-space and in the conducting medium. Later, the terms in the expansions up to the second order can be reduced to known tabulated integrals. Numerical results are presented to illustrate the improvement in accuracy that follows from using the second-order approximations for the fields in place of the zeroth-order ones. In the quasi-static frequency range and beyond, use of the new formulation makes it possible to reduce the maximum relative error in the calculation of the fields from about 23% down to less than 7%.

In Part I of this work, travelling-wave modelling of uniform multi-conductor transmission line networks was analytically established with direct applicability to narrowband transmission, covering any network formed of lossy (in the general case), diagonalisable uniform multi-conductor transmission lines of either distinct or degenerate eigenvalues. As the whole work applies especially in the field of Power-Line Communications, in Part II, a validating experimental paradigm is first provided using a common cable type for indoor power electric networks. Then, direct applicability to narrowband transmission is addressed, along with potential expandability towards wideband signalling. A comparative evaluation with other existing methods of time-domain modelling is also included and relevant directions for future research are suggested.

In Part I of this work, analysis of uniform multi-conductor transmission line networks is performed on travelling-wave basis, via "quasi-TEM" approach. Narrowband interpretation of the modal theory in the time domain and quantification of the multiple reflections effect are both included. Theoretical demonstration and analytical formulation are provided, along with guidelines towards computational implementation. Any network formed of lossy, diagonalisable uniform multi-conductor transmission lines of either distinct or degenerate eigenvalues is covered. This work applies especially in the field of Power-Line Communications, as High-Frequency transmission over the power electric network is dominated by multipath propagation.

A compact quad-band microstrip band-pass filter (BPF) based on novel step-impedance ring resonator (SIRR) is investigated in this paper. The proposed BPF is composed of one ring resonator and input/output coupled structure. The novel resonator is studied and employed to generate four desired independent passbands. A compact quad-band BPF centered at 1.57, 2.45, 3.5 and 5.2 GHz is designed and fabricated. The predicted results are compared with measured data, and good agreement is reported.

Electromagnetic fields associated with the electric current flowing along a horizontal conductor located over perfectly conducting ground are estimated using electromagnetic fields pertinent to acceleration of electric charges. It is shown that the electric and magnetic fields that exist below a long overhead horizontal conductor are nothing but the radiation fields generated by the acceleration of charge at the point of injection of current into the horizontal conductor.