An ultra-wideband (UWB) power divider is designed in this paper. The UWB performance of this power divider is obtained by using a tapered microstrip line that consists of exponential and elliptic sections. The coarse grained parallel micro-genetic algorithm (PMGA) and CST Microwave Studio are combined to achieve an automated parallel design process. The method is applied to optimize the UWB power divider. The optimized power divider is fabricated and measured. The measured results show relatively low insertion loss, good return loss, and high isolation between the output ports across the whole UWB (3.1-10.6 GHz).

A new wide-band microstrip phase inverter is reported in this paper. Interdigital striplines, defected ground and via holes are used to obtain 180° phase shift. The structure is simple and can be realized with ordinary microwave integrated circuit (MIC) fabrication process. The bandwidth is enhanced largely. A lumped-element model of the phase shifter is devised. The fabricated phase inverter has a bandwidth of 105.6% (2.065-6.682 GHz), with 1 dB insertion loss and a phase deviation less than 10°.

In a large number of applications, including communications from satellites, an optimal exploitation of the available power is of the outmost importance. As a consequence, isophoric array architectures, i.e., arrays using the same power in all the different entry points and achieving the amplifiers' maximum efficiency, are of great interest. At the same time, the easy reconfigurability of the power patterns results fundamental in order to get a full exploitation of the payload. In this paper, an innovative and deterministic approach is proposed for the optimal synthesis of linear phase-only reconfigurable isophoric sparse arrays able to commute their pattern amongst an arbitrary number of radiation modalities. The introduced perspective leads to an effective solution procedure for the fast design of antennas with high performance, and does not recur to computationally expensive global-optimization techniques. Numerical results concerning applications of actual interest and employing realistic element patterns are provided in support of the given theory.

This paper presents two design-and-analysis cases of a line-start axial-flux permanent-magnet motor: with solid rotor and with composite rotor. For a novel structure of the motor, two concentric unilevel spaced raised rings are added to the inner and outer radii of its rotors to enable auto-start capability. The composite rotor was coated by a thin (0.05 mm) layer of copper. The basic equations for the solid rotor ring were extracted. The motor's lack of symmetry necessitated 3D time-stepping finite element analysis, conducted via Vector Field Opera 14.0, which evaluated the design parameters and predicted the motor's transient performance. Results of the FEA show the composite rotor significantly improving both starting torque and synchronization capability over solid rotor.

In this paper, a design of new tri-band bandpass filter for the application of GSM (1.8 GHz), WiMAX (2.7 GHz) and UWB (3.3-4.8 GHz) is proposed. The first two narrow passbands are created, and the bandwidth of the third passband can be tuned by properly selecting the impedance ratio (R) and physical length ratio (u) of the asymmetric stepped-impedance resonator. To improve passband performance and form the UWB passband, a U-shape defected ground structure and extra extended coupling lines are integrated with the asymmetric SIR. Due to the three transmission zeros appearing near the passband edges, the band selectivity of the proposed filter is much improved. The filter was fabricated, and the measured results have a good agreement with the full-wave simulated ones.

This paper presents a complementary metal-oxide-semiconductor (CMOS) differential voltage-controlled oscillator (VCO) implemented with the push-push principle. The push-push VCO uses two frequency doublers stacked in series with an LC quadrature voltage-controlled oscillator (QVCO) to share the dc current with the QVCO for low power consumption. The proposed CMOS VCO has been implemented with the TSMC 0.18 μm CMOS technology, and the die area is 0.822×1.564 mm². At the supply voltage of 0.9 V, the total power consumption is 3.15 mW. The free-running frequency of VCO is tunable from 10 GHz to 11.15 GHz as the tuning voltage is varied from 0.0 V to 1.2 V. The measured phase noise at 1 MHz frequency offset is -114.93 dBc/Hz at the oscillation frequency of 9.99 GHz, and the figure of merit (FOM) of the proposed VCO is -190.0 dBc/Hz.

In order to achieve low cost and compact design, it becomes more and more popular to integrate the circuit of the on-board charger into other power electronic circuits existing in EVs. In this paper an integrated air conditioner on-board charger system based on switched reluctance motor (SRM) was proposed, and the electromagnetic behavior occurring in the SRM when working in the charging mode was investigated. Three charging patterns, viz. single-phase charging, double-phase charging and triple-phase charging were analyzed. The specific rotor positions for which the rotor can be kept still when injecting charging currents to the armature windings were identified. The optimal design for maximizing the keeping-still capability was conducted. The power losses occurring in the SRM when working in charging mode were estimated.

In this paper, an equivalent circuit model for special type of planer transmission lines with defected ground structures (DGS) is presented. This structure has multi stop bands in its frequency behaviour. The proposed circuit is very simple compared to the previously published works. It is considered as simplified form of the model found in [8]. Using sensitivity analysis on model [8], some circuit parameters can be omitted without significant influence on the response of the model. The modified model is easily extracted from the full-wave EM simulations. An excellent agreement is obtained between S-parameters of the simplified equivalent circuit and their counterpart of full wave EM simulators.

This paper proposes parallel-coupled stepped impedance resonators (SIRs) used for wideband bandpass filters with reduced size and improved spurious response suppression in out-of-band. The filter design concept is demonstrated by both two- and four-parallel coupled line resonator structures with the same fundamental frequency (f₀) of 6.5 GHz. The first bandpass filter has been designed using two resonators with λg/4 slot and embedded slot feeds for spurious response suppression at 2f₀ and 3f₀, respectively. The measured insertion loss is around 0.3 dB and the operation band is from 4.4 to 9.2 GHz (FBW = 73.8%). For the second bandpass filter, the embedded slot feeds and additional loaded open-stubs have been utilized to improve the wide spurious response suppression and sharp skirt characteristic in the passband. The measured passband of frequency response is from 4.2 to 8.6 GHz (FBW = 67.7%). The insertion loss of passband is lesser than 0.25 dB and the return loss is better than 15 dB. The filter designs are described in details. The simulated and experimental results are demonstrated and discussed.

An efficient numerical solution is been developed to compute the impedances of rectangular transmission lines. Method of moments is applied to integral equations for the current density, where the cross section is discretized, to improve the convergence, by a nonuniform grid that obeys the skin effect. Powerfulness of this approach up to rather high frequencies is verified by comparing with asymptotic formulas and other references. Detailed discussion is given for the current density distribution and its effect to the impedance, especially for a high frequency range.

We introduce an electromagnetic investigation of the complex experimental setup used in studying the Ratchet Effect at low We introduce an electromagnetic investigation of the complex experimental setup used in studying the Ratchet Effect at low temperature. This investigation, based on intensive electromagnetic simulations, shows that a compromise has to be taken into consideration between the physical aspects, the technological and the practical restrictions as well as the electromagnetic conditions of the observed phenomenon. By improving the electromagnetic response of the whole system, the Ratchet induced photovoltage can be increased, and hence the Ratchet device can be used for practical applications in wireless communications.

An ultra-wideband microwave imaging system that employs a heterogeneous breast phantom and covers the ultra-wideband (UWB) frequency range (3.1 GHz to 10.6 GHz) is presented. The platform scanning system allows monostatic and bistatic mode of operation. In this work, developed heterogeneous phantoms are used to mimic the realistic breast tissues. A utilized tapered slot antenna array allows for a high resolution hemispherical scan, achieved by rotating the imaged object on a turntable. Full design details of the scanning system and the utilized post-processing algorithm are explained. To validate the reliability of the presented system, the results of several imaging cases, including the challenging low dielectric contrast case, are presented.

The characteristics of guided modes in the circular waveguide consist of uniaxial chiral medium have been investigated. The characteristic equation of guided modes is derived. The dispersion curves and energy flux of guided modes for three kinds of uniaxial chiral media are presented. Unusual dispersion characteristics and negative energy flux are found, i.e., backward wave is supported in the uniaxial chiral waveguide.

A novel hydrostatic pressure sensor based on a gold-coated fiber modal interferometer (FMI) is proposed and demonstrated. Two single mode fibers (SMFs) are spliced with a lateral offset which forms a single-end FMI. The single-end FMI is gold-coated to enhance the reflectivity and to avoid the influence of any unwanted light from getting into the sensor. Relative reflection spectra of the proposed FMIs with different sensing SMF lengths or different lateral offsets are experimentally investigated. A high hydrostatic pressure sensor test system is proposed for the testing of the proposed FMI pressure sensor. The performance of a gold-coated FMI pressure sensor based on a 12-mm sensing SMF has been experimentally investigated. The proposed pressure sensor has a sensing range from 0 to 42 MPa and a sensitivity of 53 pm/MPa.

This study is designed mainly for dual band antennas of GSM/WiMAX operation in a wireless mobile communication device. This study proposes a matching technology for single path resonance in a basic monopole antenna running in dual-mode [1] and extends to a wide tuning range. The tuning of each frequency band is complicated under the constraint of the common path of dual-mode due to mutual interaction. This study proposes a refined process and new type of antennas for excellent dual-frequency matching. The incorporation of such a matching mechanism into a tuning monopole antenna enables the flexible operation bands. Moreover, the ground plane size can be shrunk to a reasonable size, and the details will be discussed in Section~6. As a result, antennas can achieve a tuning ratio of 1.6 (from 1825 to 2943 MHz). The total area of such a compact antenna including its ground can be effectively reduced to 0.018λ₀².

An integrated photonic True Time Delay phaser for phased array, based on an innovative technology, is here presented. The module versatility is showed by presenting more driving strategies matching different antenna features. The phaser insertion loss, the fluctuations of the excitation coefficients corresponding to the various driving configurations and the statistical modeling of the realization defects are also discussed.

The multi-frequency propagation in urban environment is investigated in this letter. An experimental measurement campaign is conducted to simultaneously measure the GSM-900, GSM-1800 and UMTS band of a cellular system in a suburban environment. The shadowing and small-scale fading parameters are extracted, and the correlation of these parameters across the different frequency bands is measured. It is shown that shadowing coefficients are highly correlated, while small-scale fading is completely uncorrelated between different frequency bands.

The lack of wave-plates for the terahertz region opens the way for novel components/devices enabling polarization control at these frequencies. With the aid of chiral metamaterials - a new class of metamaterials - novel possibilities for the fabrication of multilayer structures for the realization of polarization rotators emerge. In this study, we present design and analysis of a polarization rotator for the terahertz frequency regime based on a multilayer structure consisting of an alternating sequence of chiral-metamaterial- and dielectric-plates. The combination of chiral constituents with dielectrics permits optimization of the spectral-filter and polarization-rotation features. We can generate either polarization-rotation combs or narrow rotation bands with very good and broad sideband suppression, of interest for example for data transmission or sensing purposes.

The problem of direction-of-arrival (DOA) estimation by using spectral search for a non-uniform planar array is addressed. New search methods for DOA estimation based on piecewise interpolation are proposed. The relationships between these methods and Fourier-Domain (FD) root-MUSIC are discussed. The proposed methods are based on dividing the multiple signal classification (MUSIC) null-spectrum function into a number of equal subintervals. These subintervals are interpolated by using low-degree polynomials. Piecewise interpolation methods based on elementary functions are used to reduce the required computations of MUSIC null-spectrum function. This property reduces the computational complexity compared with line-search methods for DOA estimation. The Cramér Rao Lower Bound (CRB) is used as a benchmark to check the accuracy and validity of the proposed methods.

The complex permittivity of thickened waste activated sludge (WAS) was measured from 3 MHz to 40 GHz. The solid content of the thickened WAS sample was varied from 4.5% to 18% by weight. The permittivity spectra exhibit features typical of biological tissues that have a high water content. At high frequencies, a Debye type dispersion is observed with a relaxation rate of 19 GHz characteristic of the bulk water in the sample (γ-dispersion). At lower frequencies, the solid content of the samples determines the properties of the permittivity. The onset of the so-called β-dispersion, attributed to the charging of cell membranes, occurs between 10-100 MHz. For samples with higher solid concentrations, a weak dispersion of the real part of the permittivity, characteristic of bound water, was observed at intermediate frequencies (δ-dispersion).