Postgraduate, Universiti Sains Malaysia
New model/relationship of the dielectric matching network that describes the stability performances
The stability performances and matching networks analysis of the amplifier by using parasitic components of the dielectric resonator.
Abstract: Some new experimental results of optically controlled dielectric resonator oscillators (DROs) are presented. A very stable X-band DRO was found to be optically tunable up to 17.5 MHz with modulation rate of 1.17 MHz/mW with red light illumination. And an even higher modulation rate of 2.24 MHz/mW with illumination of violet light was obtained. Instead of a drop in optically controlled DRO output power, a little rise of output power was achieved.
Pub.: 01 Apr '94, Pinned: 24 Aug '17
Abstract: A wideband cryogenic amplifier has been developed for low temperature scanning tunneling microscopy. The amplifier consisting of a wideband complementary metal oxide semiconductor field effect transistors operational amplifier together with a feedback resistor of 100 kΩ and a capacitor is mounted within a 4 K Dewar. This amplifier has a wide bandwidth and is successfully applied to scanning tunneling microscopy applications at low temperatures down to ∼7 K. The quality of the designed amplifier is validated by high resolution imaging. More importantly, the amplifier has also proved to be capable of performing scanning tunneling spectroscopy measurements, showing the detection of the Shockley surface state of the Au(111) surface and the superconducting gap of Nb(110).
Pub.: 03 Jul '17, Pinned: 24 Aug '17
Abstract: This paper focuses on stability analysis and stabilization of nonlinear systems with interval time-varying delay, modeled by Takagi-Sugeno (T-S) fuzzy approach. To achieve more relaxation in the feasibility region, delay-partitioning approach is used for all integral terms in the Lyapunov-Krasovskii functional (LKF). A fuzzy Lyapunov function is proposed instead of non-integral term in LKF, and moreover, some slack matrices variables are offered to enlarge the design space. By doing this, new delay-dependent stability criteria are obtained. During the derivation of stability conditions, Jensen's integral inequality is applied to deal with integral terms. Furthermore, in this paper the problem of controller design via the parallel distributed compensation (PDC) scheme is studied. Stability and stabilization conditions with less conservative are achieved in terms of linear matrix inequality (LMI). Finally, two numerical examples are presented to show the effectiveness of the proposed results.
Pub.: 16 Jul '17, Pinned: 24 Aug '17
Abstract: As a first approach to the study of systems coupling finite and infinite dimensional natures, this article addresses the stability of a system of ordinary differential equations coupled with a classic heat equation using a Lyapunov functional technique. Inspired from recent developments in the area of time delay systems, a new methodology to study the stability of such a class of distributed parameter systems is presented here. The idea is to use a polynomial approximation of the infinite dimensional state of the heat equation in order to build an enriched energy functional. A well known efficient integral inequality (Bessel inequality) will allow to obtain stability conditions expressed in terms of linear matrix inequalities. We will eventually test our approach on academic examples in order to illustrate the efficiency of our theoretical results.
Pub.: 25 Jul '17, Pinned: 24 Aug '17
Abstract: A 9.0-GHz dielectric resonator oscillator (DRO), generating a CW output power of 2.5 W at room temperature, has been designed and fabricated using a high-power GaAs MESFET and a dielectric resonator (DR) in a parallel feedback configuration. The oscillator exhibited a frequency stability of better than 130 ppm, without any temperature compensation, over the range -50 degrees C to +50 degrees C. The output power varied from +35 dBm (3.2 W) at -50 degrees C to +33 dBm (2 W) at +50 degrees C. The single-sideband phase noise levels were measured and found to be -105 and -135 dBc/Hz, at 10- and 100-kHz carrier offset frequencies, respectively. The oscillator output was then fed into a single-stage high-power MESFET amplifier, resulting in a total RF power output of 6.5 W. The overall DC to RF conversion efficiency of the 6.5-W unit was approximately 15.3%
Pub.: 01 Jan '93, Pinned: 24 Aug '17
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