Search

An analytical study of scattering between electromagnetic waves at radiofrequencies and the collective electromagnetic modes in dielectric solids which are generated as a result of transient polarization of the bound charges under non-equilibrium thermal interaction is presented. The fundamental observation is that the symmetry of frequency spectrum of electromagnetic modes is explicitly broken due to finite electrodynamic boundaries leading to dominance of selective modes. The near field radio scattering of the electromagnetic wave by the given dielectric material results in modulation of the existing electromagnetic modes, which lead to the generation of characteristic radio emission, having a specific radio signature of the given system. [ABSTRACT FROM AUTHOR]

In a compact dual-planar electromagnetic (EM) bandgap (EBG) microstrip structure, patches are etched periodically in the ground plane to prohibit the propagation of EM waves in certain frequency bands so as to provide filtering functionality. However, the existence of the etched patches in the ground plane becomes a concern in terms of EM compatibility (EMC) and EM susceptibility (EMS). These structures might be prone to EM interference from nearby circuit components as compared to a microstrip filter with a perfect ground plane. In this paper, we study the EMS of a dual-planar EBG filter structure to a microstrip line in close proximity. This study examines the coupling effects of a nearby microstrip line on the performance of the EBG structure when the microstrip line is transmitting a signal and when it is not transmitting a signal. When the microstrip line is transmitting a signal, the effects of the working frequency and the direction of the signal on the coupling to the EBG structure are studied. Experimental and numerical work are presented, analyzed, and verified. The results obtained are useful for the applications and integrations of EBG microstrip structures to microwave circuits. They are useful for EMC and EMS studies of other patterned ground structures/defected ground structures. [ABSTRACT FROM PUBLISHER]

In this article, an approach is proposed to provide an accurate and fast calculation on the transmission coefficients of an electromagnetic band-gap (EBG) structures where patches are periodically inserted into the microstrip line (capacitive loaded EBG microstrip structure). The stopband performance, such as the center frequency, bandwidth, and attenuation, of these EBG structures can be predicted at a high degree of accuracy through the calculation of the transmission coefficient. The dispersion relation of electromagnetic waves in the structure is derived, plotted, and analyzed. The grating nature of the structure is demonstrated. This approach can be applied to periodic microstrip structures of a similar nature to simplify the analysis and design procedures. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:793–797, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25046 [ABSTRACT FROM AUTHOR]

In this paper, an E-shaped patterned ground microstrip bandstop resonant cell is proposed. In comparison to other bandstop resonators, it provides the advantages of a high-Q factor, and a sharp transition knee within a small circuit area. This resonant cell is applied to the design of a tunable bandstop resonator. Due to the unique E-shaped pattern etched in the ground plane, the proposed resonant cell is able to provide tuning function within a small circuit area. [ABSTRACT FROM AUTHOR]

A high-performance stepped-impedance low-pass filter is proposed by using a microstrip line with a longitudinal slot in the ground plane (slot-back microstrip line). The design process is simple and yet effective in improving the performance of the filter structure. Expressions are proposed to obtain the characteristic impedance of a slot-back microstrip line. Because of the high characteristic impedance and slow-wave effect of a slot-back microstrip line, the proposed filter shows a sharper cutoff and a wider stopband with higher attenuation within a smaller circuit area when compared with a conventional stepped-impedance low-pass filter. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1058–1061, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23284 [ABSTRACT FROM AUTHOR]

In this paper, a novel high-performance compact dual planar electromagnetic bandgap (DP-EBG) microstrip low-pass filter with a U-shaped geometry is proposed. By employing the unique DP-EBG configuration and the U-shaped geometry of the microstrip line (MLIN), the proposed structure achieves a wide stophand with high attenuation and a high selectivity within a small circuit area. Its passband ripple level is low due to the U-shaped geometry and the electromagnetic bandgap (EBG) structure with square patches inserted at the bends of the MLIN. The Chebyshev tapering technique is used to taper components of the proposed structure in order to eliminate ripples caused by the EBG periodicity. The structure was fabricated and the measured results are in good agreement with the simulated results. This novel design demonstrates superior low-pass filtering functionality and can easily be applied to monolithic circuits. [ABSTRACT FROM AUTHOR]

In this paper, the designs of two novel tapered dual-plane compact electromagnetic bandgap (C-EBG) microstrip filter structures are presented. With the dual-plane configuration, the proposed structure displays an ultrawide stopband with high attenuation within a small circuit area. Chebyshev distribution is adopted to eliminate ripples in the passband caused by the periodicity of the EBG structure. This gives rise to a compact EBG structure that exhibits excellent transmission and rejection characteristics in the passband and the stopband, respectively. The proposed structures are implemented and the measurement results are found to be in good agreement with the simulation results, verifying the excellent stopband and passband performance obtained using the proposed configuration. These novel structures are easy to fabricate and are promising structures that have wide applications for compact and high performance circuit component designs in microwave circuits. [ABSTRACT FROM AUTHOR]

Hyperbolic (or indefinite) materials have attracted significant attention due to their unique capabilities for engineering electromagnetic space and controlling light propagation. A current challenge is to find a hyperbolic material with wide working frequency window, low energy loss, and easy controllability. Here, we propose that naturally existing electride materials could serve as high-performance hyperbolic medium. Taking the electride Ca2N as a concrete example and using first-principles calculations, we show that the material is hyperbolic over a wide frequency window from short-wavelength infrared to near infrared (from about 3.3 µm to 880 nm). More importantly, it is almost lossless in the window. We clarify the physical origin of these remarkable properties and show its all-angle negative refraction effect. Moreover, we find that the optical properties can be effectively tuned by strain. With moderate strain, the material can even be switched between elliptic and hyperbolic for a particular frequency. Our result points out a new route toward high-performance natural hyperbolic materials, and it offers realistic materials and novel methods to achieve controllable hyperbolic dispersion with great potential for applications. [ABSTRACT FROM AUTHOR]

A mobile-phone antenna with a wideband feed structure (WBFS) and an auxiliary structure for a full metal casing and a very narrow frame are proposed. The most highlight of this proposed antenna is that it provides a method to overcome the difficulties of designing a high-performance antenna in a full metal casing with a very narrow frame. The WBFS is designed to have a broadband performance. The total size of the antenna is 6 × 48 mm2, and a 6 mm long ground clearance is set on the bottom edge of the system circuit board. The experimental results reveal that a good impendence matching is obtained across the frequency bands of 824-960 and 1710-2690 MHz, and the total efficiency is more than 40%. The antenna maintains a good performance when user's hand(s) is (are) holding it; meanwhile, keeps the specific absorption rate (SAR) under the IEEE Std. C95.1 compliant SAR. In addition, the performance of the proposed antenna in a multi-antenna system is examined. The result shows that the proposed antenna is a good candidate for a multiple-input-multiple-output system. [ABSTRACT FROM AUTHOR]

The polymorphisms of cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex 1 (VKORC1) are important genetic factors for warfarin dose determinations. The present study aimed to investigate the contribution of the CYP2C9 and VKORC1 genotypes to warfarin dose requirement in atrial fibrillation (AF) patients, and to evaluate the clinical application of a warfarin-dosing algorithm. A total of 122 AF patients with a target international normalized ratio of 2.0 to 3.0 were included to determine the genotypes of CYP2C9 (rs1057910) and VKORC1 (rs9923231). A warfarin-dosing algorithm was developed based on age, height, and the CYP2C9 and VKORC1 genotypes of AF patients. The results indicated that the mean warfarin daily dose requirement was lower in the CYP2C9*1/*3 genotype compared with those in the homozygous wild-type CYP2C9*1/*1 patients (P<0.05), and was higher in patients with the VKORC1 AG and GG genotypes compared with those with the AA genotype (P<0.05). The multivariate regression model showed that age, height, and the CYP2C9 and VKORC1 genotypes were the best variables for estimating warfarin dose (R²=56.4%). A new warfarin-dosing algorithm was developed and its validity was confirmed in a second cohort of AF patients. During the 50-day follow-up, 63.3% (19/30) of control group patients and 86.7% (26/30) of patients in the experimental group acquired the warfarin maintenance dose. Among all the patients who acquired the warfarin maintenance dose, the mean time elapse from initiation until warfarin maintenance dose was significantly less in the experimental group (25.8±1.7 day) compared to the control group (33.1±1.9 day) (P<0.05). There was significant linear correlation between predicted warfarin maintenance dose and actual dose (r=0.822, P<0.01). In conclusion, a new warfarin-dosing algorithm was developed based on the CYP2C9 and VKORC1 genotypes, and it can shorten the time elapse from initiation until warfarin maintenance dose in AF patients with warfarin therapy. [ABSTRACT FROM AUTHOR]