The aim of this work is to miniaturize a microstrip patch antenna resonating at 3 GHz. For this purpose, defected ground structure (DGS) has been employed to shift the resonance frequency of an initial microstrip antenna from 5.7 GHz to 3 GHz by disturbing the antenna's current distribution. The proposed DGS is incorporated in the ground plane under the patch antenna to improve its performances. Finally, a miniaturization up to 50%, with respect to the conventional microstrip antenna, is successfully accomplished. A prototype of the antenna was fabricated with the FR4 substrate and tested. The measurements results were in good agreement with simulation results.
Abstruct-The modeling of low-frequency dispersive effects due to surface state densities, deep level traps and thermal phenomena plays an important role in the large-signal performance prediction of 111-V FET's. This paper describes an empirical modeling approach to accurately predict deviations between static and dynamic drain current characteristics caused by dispersive effects in 111-V devices operating at microwave frequencies. It is based on reasonable assumptions and can easily be embedded in nonlinear FET models to be used in Harmonic-Balance tools for circuit analysis and design. Experimental and simulated results, for HEMT's and GaAs MESFET's of different manufacturers, that confirm the validity of the new approach, are presented and discussed together with the characterization procedures required.
Abstract-This paper presents a wideband model, from Direct Current (DC) to W band, for a single Anode Schottky Diode based on a commercial VDI chip. Different measurements have been performed to obtain a complete large-signal equivalent circuit model suitable for the device under consideration up to 110 GHz, and for its integration in planar circuits. The modeling has been done using a combination of DC measurements, capacitance measurements, and RF scattering measurements. The test structure for on-wafer Sparameter characterization has been developed to obtain an equivalent circuit for Coplanar to Microstrip (CPW-Microstrip) transitions, then verified with 3D Electromagnetic (EM) tools and finally used to deembed device measurements from empirical data results in W band. 3D EM simulation of the diodes was used to initialize the parasitic parameters. Those significant extrinsic elements were combined with the intrinsic elements. The results show that the proposed method is suitable to determine parameters of the diode model with an excellent fit with measurements. Using this model, the simulated performance for a number of diode structures has given accurate predictions up to 110 GHz. Some anomalous phenomena such as parasitic resistance dependence on frequency have been found.
Abstruct-The modeling of low-frequency dispersive effects due to surface state densities, deep level traps and thermal phenomena plays an important role in the large-signal performance prediction of 111-V FET's. This paper describes an empirical modeling approach to accurately predict deviations between static and dynamic drain current characteristics caused by dispersive effects in 111-V devices operating at microwave frequencies. It is based on reasonable assumptions and can easily be embedded in nonlinear FET models to be used in Harmonic-Balance tools for circuit analysis and design. Experimental and simulated results, for HEMT's and GaAs MESFET's of different manufacturers, that confirm the validity of the new approach, are presented and discussed together with the characterization procedures required.
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