Minimum side-zone power to center-zone power ratio (MSCR) method is presented to estimate array errors of azimuth multichannel synthetic aperture radar (SAR). Spaceborne azimuth multichannel SAR is one of the most promising candidates for achieving high-resolution wide-swath imaging. However, array errors brought in by instrument influences and aperture position errors need to be compensated. MSCR method is designed to obtain phase error estimates by minimizing side-zone power to center-zone power ratio, where the side-zone and the center-zone indicate the intervals far from and around Doppler centroid respectively. The proposed method achieves significantly improved performance on phase error estimation especially when signal to noise ratio is low. Experiment results confirm the validity and solidity of the method.

A new analytical technique to study the complex resonances of a rectangular patch in a multilayered medium is introduced. The problem is formulated as an electric field integral equation (EFIE) in the spectral domain and discretized by means of products of Chebyshev polynomials of first and second kind multiplied by their orthogonal weights in a Galerkin's scheme. The method is fast convergent, i.e., few expansion functions are needed to achieve accurate results, but leads to the numerical evaluation of infinite double integrals of oscillating and slowly decaying functions. To overcome this problem, suitable half-space contributions are pulled out of the kernels of such integrals in order to obtain exponentially decaying integrands. Moreover, the slowly converging integrals of the extracted contributions are expressed as combinations of quickly converging integrals by means of algebraic manipulations and an appropriate integration procedure in the complex plane.

A compact U-shaped defective ground structure (DGS) and an inverted U-shaped resonator are introduced in order to reduce the mutual coupling (MC) between two slotted microstrip antennas at two different resonance frequencies. The proposed DGS and resonator have the same electrical length and both are placed in between two patch antennas, as a technique to suppress the occurrence of MC at two different frequency bands. The DGS and the resonator offer stop bands at 2.45 GHz and 4.5 GHz respectively. Simulated results show a reduction in MC of 20 dB at 2.45 GHz band and 10 dB at 4.5 GHz band. We have developed experimental models that have proved this concept of MC reduction. Finally, the influence of other parameters of the proposed antenna at the presence of the combination of DGS and resonator in the array system has been studied. Prototype antennas for different combinations of DGS and resonator and two-element array integrated with DGS and resonator have been fabricated, measured and the idea has been verified. A good agreement is observed between measured and the simulated results.

Theoretical results on the electromagnetic wave diffraction from a periodic strip grating placed on a chiral medium are obtained. Analytical regularization method based on the solution to the vector Riemann-Hilbert boundary value problem was used to get robust numerical results in the resonant domain, where direct solution methods typically fail. It was shown that in the case of normal incidence of linearly polarized wave the cross-polarized field appears in the reflected field. For elliptically polarized incident wave the diffraction character essentially depends on the polarization direction of the incident wave. These diffraction peculiarities are more pronounced in the resonant domain. Influence of the dichroism caused by chiral medium losses is thoroughly studied. The combination of a chiral medium and a grating can be effectively used for a frequency and polarization selection and for a mode conversion.

The characteristics of periodic multilayered near-field superlenses are analyzed and optimized, using the dispersion relation derived from an effective medium theory and the transfer function in the spectral domain. The k'_z-k''_x and k_z-k_x contours are used to explain and predict the spectral width, amplitude and phase of the transfer function. Superlenses containing CsBr or active layers are proposed to reduce image distortion or to compensate for the propagation loss, respectively. The parameters of the superlenses can be optimized by simulations to resolve half-pitch features down to λ/36 using CsBr layers, and λ/20 using active layers.

Radar scattered time domain response can be modeled by natural poles using singularity expansion method (SEM) in resonance region. In this paper, limitation of the conventional Extinction pulse method is brought out, and a hybrid of conventional Extinction pulse and auto-regressive (AR) method is proposed for robust discrimination of radar targets. A new target discrimination number (TDN) is suggested, which gives very good discrimination margin for enhanced decision process. The Hybrid Extinction pulse technique is applied on the free space targets as well as subsurface canonical metallic targets and the result obtained shows good discrimination margin. The free space target response was obtained using FDTD simulation and the subsurface target response was obtained using frequency domain measurement done for the targets buried under dry sand.

An improved directional equiangular spiral antenna with wide CP band and high gain is proposed, in which the impedance bandwidth is 2~12 GHz, CP bandwidth 4.5~7 GHz, and gain 6~9.5 dBi. The antenna includes 4 layers. The top layer is equiangular spiral antenna, and the bottom layer is ground. The middle two layers are parasitic metal films with irregular rectangular holes, which are introduced to improve the performance of equiangular spiral antenna and reduce the profile. The measured results are in good agreement with the simulated ones.

The purpose of this paper is to describe a model predictive direct torque control (MPDTC) with load angle limitation for surface-mounted permanent magnet synchronous motor (SPMSM) drive system. In this paper, an exact discrete-time state-space model of SPMSM is presented, which improves the state prediction accuracy comparing to simple Euler approximation. A finite control set type MPDTC is used to select the optimum voltage vectors applying to the voltage source inverter (VSI). It makes full use of the inherent discrete nature of VSI, and according to the predefined cost function it chooses the optimal solution from the possible switching states. It has been found that with the proposed scheme SPMSM drives show adequate dynamic torque performance and considerable torque ripple reduction as compared to traditional direct torque control (t-DTC). With the load angle limitation in the cost function, the proposed scheme can prevent the PMSMs falling from synchronism.

A novel extremely compact Zeroth Order Resonator (ZOR) antenna with a chip inductor, for Digital Video Broadcasting-Handheld (DVB-H) application, is presented. The proposed antenna has a bowtie structure with an overall dimension of 0.0186λ₀ × 0.020λ₀ × 0.003λ₀ mm³ at 503 MHz. The zeroth resonance property makes the resonant frequency to be independent of the antenna dimension. The 3:1 VSWR bandwidth of the antenna is 39 MHz and offers an omnidirectional radiation pattern. A 99.1% reduction in the overall area of the structure is achieved compared to a conventional circular patch antenna operating at the same frequency.

MIMO reference antennas are proposed for over the air (OTA) measurement applications. The reference antennas could get rid of feeding cable interference and control envelope correlation coefficients (ECC) continuously by only changing the length of an etched slot on a dual-feed PIFA. If only the ECC is investigated, the MIMO reference antenna is optimized to have a small variation of total efficiency from 70% to 50% when the ECC increases from 0.1 to 0.88. The prototypes are fabricated and measured in a scattered field chamber (SFC). Measurements agree well with the simulations. A practical example of applying this kind of reference antenna is provided. If the MIMO performance is studied, the MIMO reference antenna is proposed to own a large variation of total efficiencies from 90% to 47% while the ECC increases from 0 to 0.98. The bandwidth of the proposed reference antennas depend on the size of the antennas. This method is valid for all the frequencies.

Gaussian beam techniques are efficient asymptotic methods for field radiation computation. In these techniques, the initial field is first expanded on a chosen surface in elementary Gaussian beams which can propagate and/or interact with surrounding structures. However, the expansion cannot take into account surface and leaky waves propagation. In this paper, we propose an appropriate hybridization method using surface equivalent currents to overcome this limitation. The equivalent current formulation is written on grounded dielectric slab in spectral domain and can model surface and leaky waves which propagate from the surface expansion. The hybridization is carried out on the expansion surface, on which the distribution of elementary Gaussian beams and equivalent currents must be chosen in a relevant way. We study the influence of hybridization parameters and define a set of them leading to good results for general cases.

This paper proposes a miniature microwave bandpass filter. It comprises quasi-lumped suspended substrate stripline resonators of a new type. Their common substrate consists of two contiguous dielectric layers. Every resonator in the filter has three parallel strip conductors. Two of them are placed on the outer substrate surfaces and the rest is placed inside the substrate. The filter of the sixth order was designed with the use of special optimization rules that are universal for all resonator filters. The substrate of the fabricated filter was made of RT/Duroid 5880 (ε_r = 2.2, tan δ =0.002) with thickness of 0.127 mm. It has dimensions of 12 mm x 45.5 mm. The measured passband has a center frequency of 1.01 GHz, 3-dB fractional bandwidth of 11%, and minimum insertion loss of 1.4 dB. The 100-dB upper stopband extends up to 10.5 GHz.

In this paper, a novel compact tri-band monopole antenna for WLAN/WiMAX applications is proposed. By using a horizontal H-shaped strip and an L-shaped open end stub, and a deformation inverted T-shaped strip through a matching line attached to the 50-Ω feed-line, tri-band has impedance bandwidths for S₁₁≤ -10 dB are 2.4-2.7 GHz, 3.4-3.72 GHz, 5.06-5.85 GHz, covering 2.4/5.2/5/5.8 GHz for WLAN and 2.5/3.5/5.5 for WiMAX applications can be acquired. Experimental results show that the proposed tri-band antenna has nearly omnidirectional radiation characteristics across all the operation bands. Furthermore, the antenna with compact size of 30 × 20 × 0.8 mm³ has simple structures.

In present paper, the effect of relativistic hot electron beam for field aligned Whistler mode waves has been studied theoretically in the presence of AC electric field perpendicular to magnetic field. Studies have been performed using perturbative approach along with the method of characteristic solutions and are valid for comparatively small ambient magnetic field of Uranus, of the order of nano Tesla, as observed by Voyager 2. The detailed derivation and calculations has been done for dispersion relation and growth rate for magnetosphere of Uranus. Analyses are done by changing various plasma parameters which are explained in result and discussions section of this paper. Extensive study of wave-particle interactions and numerical calculations concludes that in case of injection of a distribution of particles having a positive slope in v_⊥, temperature anisotropy remains the main source of free energy. It is seen that other effective parameters for the growth of whistler mode waves are AC frequency and higher number density of hot electrons. We also learn that even the minimal presence of such energetic particles having a positive slope of distribution function and increasing power of perpendicular thermal velocity can increase the growth rate significantly in the magnetosphere of Uranus. The present work is basically based upon the theoretical investigation and mathematical analysis of the magnetosphere of Uranus, supported by satellite data.

Based on energy injection and free resonant mode, an approach to optimize the startup frequency setting of the voltage-fed inductive power transfer (IPT) system is proposed to mitigate the effects of uncertain system parameters and load conditions. Differential equations of the primary resonant network on the free resonant mode is firstly established, then the free resonant frequency with different parameters and load conditions is calculated and verified with the soft-switching frequency of system based on stroboscopic mapping modeling method and fixed points theory. By controlling the micro-energy injection of system and free resonance, the frequency of free resonant mode is detected, and is regarded as the fixed frequency of startup process. Hence, the proposed strategy solves the uncertainty of the startup frequency and system re-setting to fit with changed system parameters and load conditions. This method also initiates immediate protection when the system operates under zero loads. In sum, our experimental results verify the theoretical implication, effectiveness, and merits of the proposed approach.

This paper proposes a novel design methodology for dual-band Doherty power amplifier (DPA) with simplified offset-lines. The methodology is validated with the design and fabrication of a 10 W GaN based DPA for Global System for Mobile Communications (GSM) and Wideband Code Division Multiple Access (WCDMA) applications at 0.90 GHz and 2.14 GHz, respectively. In the measurement results, the DPA achieves a drain efficiency (DE) of 51.2% with an output power of 37.2 dBm at the 6.5 dB output power back-off (OBO) from the saturated output power at 0.90 GHz, and a DE of 39.9% with an output power of 37.4 dBm at the 6.5 dB OBO at 2.14 GHz. Linearity results using 20 MHz 16QAM signal show an adjacent channel leakage ratio (ACLR) of -48 dBc and -43 dBc with the average output power of 37.2 dBm and 37 dBm at 0.90 GHz and 2.14 GHz, respectively.

This paper introduces a new numerical method to calculate the group delay, chromatic dispersion and dispersion slope of weakly-guiding optical fibers with arbitrary radial refractive index profiles. It is based on the analytic differentiation of the propagation coefficient up to the third order. The simulation results are compared to experimental data, with those calculated by other approaches and exact data where possible. Due to the analytical differentiation of the matrix equation, the method is more accurate compared to other approaches, it is also much faster than numerical differentiation as allows avoiding repeated solution of the eigenvalue problem to calculate the derivatives of the propagation coefficient. The precision of the method is limited only by the approximation errors of the mode solver. The Galerkin method with Laguerre-Gauss basis functions is used to determine the propagation coefficients of weakly-guiding structures. The new method enables fiber manufacturers to rapidly design dispersion characteristics of graded index, step index, single- and multiple-clad fibers, as well as few-mode and bend insensitive fibers.

Permanent-magnetmotorsare widely usedin-wheel motors of electric vehiclesand hybrid vehicles. Based on a movable stator design, this paper presents a new type permanent-magnet motor, whose torque can be adjusted in order to meetdifferent driving requirements. The stator geometryis varied by means of changing movable stator positions.Accordingly, the air-gap lengthin permanent-magnet motorsis changed so that torque can be adjusted. To derive an analytical model, Fourier series expansions are employed to formulate air-gap geometry variation. The analytical modelis validated by finite element numerical results.Concerning motor torque variation capability achieved in this study, the ratio of the largest vs. the smallest torque is 2.3.

Partial Discharge (PD) measurements may be affected by external noise and disturbances of various natures such as interference from broadcasting stations, stochastic noise, pulses from power electronics, etc. Extracting PD pulses from such a noisy environment is therefore a crucial issue. This paper presents a wavelet based technique for automatic noise rejection. The core of the paper is the use of an improved methodological approach for the selection of a suitable wavelet, which aims at summing up the benefits and overcoming some limitations of previous techniques. Firstly, a very wide set of training signals is used for the identification of the decomposition level and for the calculation of suitable performance parameters that identify each wavelet; then a Performance Fingerprint is introduced in order to summarize the ability of a specific wavelet to reconstruct a partial discharge waveform, and a distance criterion is used for the selection of the most suitable wavelet. Afterwards, useful information is collected for the reconstruction of the PD signal, and finally, results on the application of the algorithm for a set of numerical and experimental signals are presented.

A broadband power amplifier designed and implemented in Doherty configuration is illustrated in this paper. Both input and output networks adopt the broadband matching topology. Additionally a compensation network, consisting of a series transmission line shunted with a capacitance, is set behind the peak amplifier to avoid in-band power leakage in the low-power section while at the cost of peak output power in partial band. A novel coupler is designed as an uneven power-divided splitter and experimentally validated for a broadband power amplifier module. A tradeoff of bandwidth, efficiency and output power is fulfilled through parameters select and postproduction tuning. According to the measured results, the proposed broadband Doherty power amplifier achieves an average saturated output power of 42 dBm, an average gain of 10.6 dB, an average peak and 6 dB back-off efficiency of 48.4% and 32.8%, respectively, and a fractional bandwidth of 51.4%, from 1.3 GHz to 2.2 GHz. The adjacent channel power ratio is better than -40 dBc when the amplifier is driven with 10-MHz QPSK signal, thus exhibiting a high linearity performance.