A dual-band circularly polarized antenna is presented in this paper. A rectangular patch antenna with gap-feeding structure is firstly designed, and 3-dB axial-ratio bandwidth from 2.35 to 2.48 GHz is obtained. A parasitic square ring is placed on the rear of the rectangular patch as a band-notch unit operating around 2.4 GHz. Then an original wide circularly polarized band is split into two bands from 2.25 to 2.31 GHz and from 2.46 to 2.53 GHz. By adopting differential feeding, symmetrical patterns are achieved. Measurement results show that two 3-dB axial-ratio bands of 2.6% (2.25-2.31 GHz) and 2.0% (2.51-2.56 GHz) are obtained with a small frequency ratio of 1.11.

In this paper, a bi-layer twisted split-ring structure asymmetric chiral metamaterial was proposed, which could achieve circularly polarized (giant circular dichroism effect) wave with dual bands and linear polarization transformation (giant optical activity)with asymmetric transmission wave emissions simultaneously from linearly polarized incident wave at microwave frequencies. Experiment and simulation calculations are in good agreement, indicating that the dual-band circular polarizer features high conversion efficiency around 5.32 GHz and 6.6 GHz in addition to large polarization extinction ratio of more than 16 dB, while cross linear polarization transformation with asymmetric transmission is observed around 10.52GHz. The transformation behavior for both circular and linear polarizations could be further illustrated by simulated surface current and electric field distributions. The proposed asymmetric chiral metamaterial structure could be useful in designing novel EM or optical devices, as well as polarization control devices.

The microwave polarimetric scattering from two-dimensional (2-D) wind fetch- and water depth-limited nearshore sea surface is investigated by using the second-order small-slope approximation (SSA-II). The sea waves are simulated by taking into account the influences of fetch and depth. Based on this, the joint influence of fetch and depth on the normalized radar cross section (NRCS) of sea surfaces for both co-polarizations and cross-polarization in different wind directions is mainly studied. Monostatic and bistatic numerical results both indicate that in the marine environment of small depth and large fetch, the nonlinear interactions among waves become more intense, which has a greater impact on NRCSs for co-polarizations than their cross-polarized counterparts. Comparison of the results for different wind directions also reflects that the backscattered echoes along wind direction have much greater strength, regardless of the magnitude of wind fetch and water depth.

The flux and torque of switched reluctance motor (SRM) have a highly nonlinear functional relationship with rotor position and phase current, as a consequence of the double-salient structure of the stator and rotor pole and highly magnetic saturation, which is difficult to build an accurate analytic model. In order to achieve the SRM high-performance control, it is necessary to build an accurate nonlinear model for SRM. On the basis of the adequate and precise sample data, by taking advantage of neural network that has outstanding nonlinear mapping capability, this paper adopts the Back Propagation (BP) based on Levenberg-Marquardt (LM) algorithm and Radial Basis Function (RBF) neural networkto build offline models for SRM respectively. Under different requirements of model accuracy, two kinds of network are studied and compared with each other on accuracy, scale and other aspects. The research results indicate that the network scale built as SRM nonlinear model by BP neural network based on LM algorithm is smaller than the one built by RBF. Additionally, the model accuracy is higher. In terms of the Switched Reluctance Drive (SRD) which requires real-time controller, reducing the network scale will be beneficial to the online real-time control of the system.

To reduce the complexity of classifier design in radar automatic target recognition (RATR), a novel RATR method for high range resolution profile(HRRP) is proposed. Linearly separable features are extracted with sequential vanishing component analysis (SVCA) which is implemented by finding the generators of each approximately vanishing polynomial set, and target classification is implemented with linear classifiers. Experiments are carried out on simulated vehicle target data and MSTAR database, and the results demonstrate the efficiency of the proposed method.

In this paper, a delivery system allowing simultaneous microwave heating and real-time spectrofluorometric measurements in biological systems is proposed and characterized. This system is used to investigate the phase behavior of lipid bilayers from about 15°C to 45°C. The delivery system is based on an open transverse electromagnetic (TEM) cell combined with a spectrofluorometer via an optical cable system. A numerical and experimental dosimetry of the delivery system is conducted. The Specific Absorption Rate (SAR) efficiency of the system is 26.1±2.1 W/kg/W. Spectrofluorometric measurements on Laurdan labeled small unilamellar vesicles (SUVs) are carried out. Generalized polarization (GP) of the SUV' membrane is obtained from the fluorescence intensities measured at two emission wavelengths.

This paper deals with the modeling of the brushed DC motor used as a reinforced starter for a micro-hybrid automotive application. The aim of such a system, also called ``stop-start'', is to stop a combustion engine when the vehicle pulls to a stop, and to restart it when the driver accelerates. A reinforced starter is able to ensure this new function in addition to the classical cold start. Then, its life time has to be widely increased in comparison with a classical starter. They have to be optimized, and more especially their process of commutation in order to minimize commutator and brush wears, and thereby increase the lifetime of the device up to the whole life of the vehicle. The main contribution of the paper is the development of a coupled FE-circuit model taking into account local saturation and arc phenomena. Brush-segment contact resistance introduced in the circuit model has been computed efficiently and compared to measures. The whole model has been validated by experimental measurements which are carried out with specific experimental test benches.

A modified Y-parameters approach is proposed to model the behavior of coupled oscillator arrays (COA's). A coupling network with tunable coupling strength is proposed, which has a near-constant input conductance, to ensure the oscillation condition under different attenuation levels. The parameters of oscillators and the coupling network are derived on the TSMC 0.18 μm technology, and their Y parameters are extracted around 10 GHz for illustration. After being verified with full-circuit simulations and other behavior models, including the Adler's equation and the conventional Y-parameters approach, this method is applied to estimate the maximum allowable number of oscillators that can be coupled together. The inter-element phase shift of a COA is controlled by tuning the free-running frequencies of oscillators at both ends. Injection signals with proper phases are proposed to synchronize multiple COA's into a bigger COA.

In this paper, a novel microstrip-fed compact antenna with triple band-notched characteristics is presented for ultrawideband (UWB) applications. The antenna consists of a circular radiating patch, a 50 Ω microstrip feed line, a partially slotted ground plane, and a pair of modified capacitance loaded loop (MCLL) resonators. The novel resonators are symmetrically located in the vicinity of the feed line to achieve triple band-notched characteristics, such as 3.4-3.7 GHz for WiMAX, 5.15-5.825 GHz for WLAN, 7.25-8.395 GHz for X-band satellite communication. The good performance of triple notched bands, stable gain and omnidirectional radiation patterns in the operating bands make the proposed antenna a good candidate for UWB utilization.

A novel ultra-wideband (UWB) bandpass filter (BPF) with notched band based on microstrip/slotline ring resonators is presented in this paper. The UWB BPF is fabricated with two microstrip ring resonators on the top copper layer and a slotline ring resonator on the bottom ground layer. Thus, an ultra-wide passband can be achieved owing to the coupling effects and microstrip/slotline transitions of these three ring resonators. Then, a notched band which is created at 8.0 GHz for satellite communication system is designed based on loaded short-circuited stubs. Both the simulated and measured results show that this compact UWB BPF has good performances of wide passband and notched band.

A novel coplanar waveguide (CPW)-fed tri-band monopole antenna for WLAN/WiMAX applications is presented. To get a compact antenna size, meandering and coupling technologies are used here. Meanwhile, with the loading method, the higher mode is used to cover the required band. The antenna has a very small size of only 18×28 mm². The measured and simulated results show that the proposed antenna has three separate 10-dB impedance bandwidths of 220 MHz (2.36-2.58 GHz), 470 MHz (3.36-3.83 GHz) and 1460 MHz (4.83-6.29 GHz), which can cover all the 2.4/5.2/5.8 GHz WLAN and 3.5/5.5 GHz WiMAX bands. Good dipole-like radiation characteristics are obtained over the operating bands.

A coupled-line-based planar antenna for single-band and dual-band operation is presented. The well-known uniplanar coupled inverted-L antenna (UCILA) has a simple and specific mechanism to achieve the dual-band ratio that was not described in the past. The UCILA which shunted a short stub in the slotline portion can provide switchable modes among single-low band (3.4% for WLAN 2.44 GHz), single-high band (15% for WLAN 5.2-5.8 GHz band) and dual-band (WLAN 2.44/5-6 GHz) operations.

A wideband dual-polarized crossed-dipole antenna with parasitical crossed-strip for base-station applications is presented. By using a pair of orthogonal crossed-dipoles, two linear polarizations (+45°) are obtained. A parasitical crossed-strip is introduced to improve the impendence bandwidth and enhance the isolation (S₁₂) between the two orthogonal polarizations of the upper band. The antenna shows a wideband impedance characteristic about 34.9% for S₁₁≤-10 dB (+45° polarization) and S₂₂≤-10 dB (-45° polarization). High isolation (S₁₂≤-32 dB) between the two polarizations in the required band are obtained. The stable peak gain, unidirectional radiation patterns and low cross-polarization over the whole operating band are also achieved. Due to its good performance, simple fabrication technique and low cost, the antenna is very suitable for potential base station applications in mobile communication such as DCS, PCS and UMTS.

Electromagnetic shielding (EMS) fabrics often need to design rectangular holes for application. However, there is not a mature approach to predict the shielding effectiveness (SE) of the EMS fabric with rectangular hole. This paper proposes that there are a number of loose regions of conductive fibers on the hole edge of the EMS fabric, and establishes a SE prediction model of the EMS fabric with rectangular hole. Firstly, the loose region of conductive fiber is analyzed to build a model of the rectangular hole. Secondly, the SE prediction model of the EMS fabric with rectangular hole is deduced according to the transmission coefficient of the normal region, hole region and loose region, and the determining method of the loose region is given. Finally, the prediction model is verified by experiments. The results show that the model can successfully predict the SE of the EMS fabric with the plain, twill and satin weaves, and the factors such as frequency, fabric density and metal fiber content have little influence on the model. The proposed model can provide a valuable reference for the rational design of the rectangular hole of the EMS fabric.

We propose a general method to design an arbitrarily shaped radome which can extend the scanning angle of a phased array antenna through finite embedded transformation (FET). The main advantage of our method is that the relationship between the incident angle and steered output angle of the radome can be designed in advance (e.g., a linear relation can be achieved). Unlike a traditional FET, which is often applied onto a slab region, we first apply FET onto an arbitrarily shaped region to bestow the desired radome with an arbitrary shape. Two specific examples have been given to demonstrate our method. Numerical simulations show good performance of our radome.

Implanted antennas are widely used in hyperthermia and biomedical applications. The antenna needs to be extremely small while maintaining a permissible Specific Absorption Rate (SAR) and being able to cope with the detuning effects due to the dielectric properties of human body tissues. Most of the proposed antennas for implanted applications are electric field antennas such as Planner Inverted-F Antennas (PIFA) and micro-strip patch antennas. By minimizing the size of an electric field antenna, the near zone electric field will increase, resulting in higher SAR. This work is devoted to design a miniaturized magnetic field antenna to overcome the above limitations. The proposed electrically coupled loop antenna (ECLA) has high magnetic field and low electric field in the near zone and therefore, has a small SAR and is less sensitive to detuning effects. ECLA is designed at the Medical Implanted Communication Service (MICS) band with dimensions of (5×5×3 mm³). ECLA has been simulated inside one-layer human body model, three-layer spherical human head model, human head and human body. From the simulation results, ECLA inside the human body has a 5 MHz -3 dB bandwidth, -14 dB gain, and radiation efficiency of 0.525%. The 1 g average SAR inside the human body for 10 mW input power is about 1 W/kg which is 7 times lower than the SAR for a patch antenna of the same size with the same accepted power.

The paper presents a methodology to achieve efficient low-profile electromagnetic bandgap (EBG) antennas based on thick EBG unit cells. The EBG cells are composed of thick metal patches separated by narrow high aspect ratio (HAR) gaps, and positioned on a PEC-backed substrate. This approach yields new miniaturized EBG cells with considerably reduced electrical size. The miniaturized cells are employed to demonstrate new compact self-excited EBG resonator antennas with considerably reduced operating frequencies. Full-wave simulations and experimental results demonstrate the design approach.

This study presents an equivalent circuit and a design of an H-plane waveguide bandpass filter (BPF) with chamfer. Traditionally, only thin inductive diaphragm with no chamfers considered in the direct-coupled cavity theory, but this will lead to difficulties in the BPF manufacturing. During manufacturing process the chamfer cannot be avoided, and its equivalent circuit and effects on frequency shifting are investigated in this paper. A new design method is proposed in order to compensate the effect of chamfer in the half-wavelength resonator connection between the inductance diaphragm and the waveguide. A modified empirical formula and corresponding procedure are provided for designing such filters. The working center frequency and 3 dB bandwidths (BW) are simulated considering different chamfer radius. The simulated center frequencies are 18 GHz, 26 GHz, 34 GHz and 42 GHz, and BWs are 2.265%, 2.5%, 10%, 15% and 20%. Results show that the modified formula, which conforms better with the simulated results, is superior to the traditional formula. Two H-plane waveguide BPFs are manufactured with center frequency 26 GHz with 2.5% BW and 34 GHz with 2.265% BW. The results of the modified formula are in good agreement with measured ones.

In this paper, we study the scheduler design problems over delay-constrained wireless communication links. Following a crosslayer design approach, the wireless system is modeled as a joint link-PHY layer architecture with a finite-length buffer and continuousstate fading links. A heuristic and efficient fixed rate transmission scheduler scheme (FRT) is proposed. We formulate and analyze the performance of the FRT scheme in terms of power efficiency and packet drop rate. Compared with variable rate schemes, the FRT scheme can considerably simplify the hardware implementation of transmitter. In addition, we show that the optimization of FRT scheme can be conducted with significantly reduced computational cost by utilizing the sparse feature of the transition probability matrix. Moreover, the simulation results show that at the packet drop rate of 10^-3, the optimized average transmit power of FRT scheme is only 0.5 dB higher than the known optimal variable rate scheme, indicating that the FRT scheme is quite power efficient as well. Therefore, we conclude that the FRT scheme is more feasible than variable rate schemes in practical delayconstrained wireless systems with regard to both hardware cost and power efficiency.

In this paper, extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structures, with two left-handed (backward) and two right-handed (forward) pass bands, are investigated. Also, design procedures in order to design dual- and quad-band E-CRLH-TLs are presented in detail and the parameters of these structures are extracted by clean formulas, while satisfying arbitrary phase shifts at the operating frequencies. Finally, the dispersion and characteristic impedances of these transmission lines are derived and plotted. The results of this paper can be applied to any type of TL-based dual- and quad-band microwave component.