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Three new isoflavone C-glycosides, along with two known isoflavone O-glycosides, were isolated from the roots of Pueraria lobata (.) . The structures of the new compounds were elucidated as 4′,7-dihydroxy-3′-methoxyisoflavone 8- C-[ βglucopyranosyl-(1→6)]- βglucopyranoside (), 4′,7-dihydroxy-3′-methoxyisoflavone 8- C-[ βapiofuranosyl-(1→6)]- βglucopyranoside (), and 8- C- βglucopyranosyl-4′,7-dihydroxy-3′-methoxyisoflavone 4′- O- βglucopyranoside () on the basis of spectroscopic methods, especially 2D-NMR and MS analyses. The known compounds isolated were identified by comparison of their physical and spectroscopic data with those reported in the literature. [ABSTRACT FROM AUTHOR]

A novel defected ground structure (DGS) with two semicircular defected areas is investigated for low pass filter (LPF) applications. An equivalent lumped L-C circuit model is presented and its corresponding L-C parameters are also extracted by using parametric relationships. With this structure, the effect of the defected parameters on performance is detailed. Based on the equivalent circuit model, a 3-pole LPF, using 2 DGS units, is optimally designed and implemented. The results from experiments confirm that the designed LPF can provide a very wide stop band, which is approximately 3.7 times of the cutoff frequency. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1760–1763, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21750 [ABSTRACT FROM AUTHOR]

In this paper, an equivalent-circuit model of a defected ground structure (DGS) is applied to explain the characteristics of the DGS. The parameters of the circuit model are extracted from the EM-simulation results. A novel three-pole lowpass filter is proposed and optimized by using the defected ground structures. It is demonstrated that the filter can provide a sharp rate of attenuation in the stop-band, as predicted. To further verify this method, the filter with DGS is fabricated on a 30 × 30 mm2 substrate. A comparison between the simulation and the measurement confirms the effectiveness of the proposed schemes. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 17–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20888 [ABSTRACT FROM AUTHOR]

In this work we numerically investigate the nonlinear dynamics of the Colpitts oscillator. Bifurcation diagrams of consecutive plots of the values of electrical current minima are presented, according to the circuit parameters. By following observer-based synchronization, two identical Colpitts oscillators with scalar transmitted signals are developed. Computer simulation results are given. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 446–449, 2003 [ABSTRACT FROM AUTHOR]

A novel compact dual-mode microstrip bandpass filter (BPF) with adjustable transmission zero (TZ) is proposed. It is composed of a nested microstrip square-loop resonator. The filter with two TZs in the lower and upper stopbands is designed, fabricated, and measured. A circuitry size reduction of 55% is achieved by the proposed filter when compared with the convention dual-mode filters with nonorthogonal feed lines. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2049–2051, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24560 [ABSTRACT FROM AUTHOR]

We discuss the dynamics of the forced modulation-doped AlxGa1-xAs heterostructure device governed by the coupled differential equations, which is operative in the state far from thermodynamic equilibrium. Biased with an appropriate dc field, the system exhibits two states: spontaneous current oscillation and fixed points. Under an ac driving force imposed on a dc bias, the dynamical system shows the expected characteristics of frequency locking, quasiperiodicity, and chaos, which are sensitive to the amplitude and frequency of the external applied microwave field. In particular, the basins of attraction of both an ordinary attractor and a chaotic attractor are presented. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 93–95, 2001. [ABSTRACT FROM AUTHOR]