Showing papers by "Zhirun Hu published in 2006"

Optimization and Realization of Planar Isolated GaAs Zero-Biased Planar Doped Barrier Diodes for Microwave/Millimeter-Wave Power Detectors/Sensors

Abstract: A high tangential signal sensitivity (TSS) zero-bias GaAs planar doped barrier (PDB) diode for microwave and millimeter-wave power detection applications is presented. The fabricated PDB diodes have shown 4 dB better TSS at 35 GHz than that of reported devices, considerably increasing the minimum detectable power and widening the dynamic range. The high TSS was obtained by optimizing the PDB layer structures, namely, the delta-doped p++ layer and the two intrinsic layers, and by employing ion bombardment to better define the device and reduce parasitic effects. The isolation properties of ion bombarded epitaxial layers on GaAs substrates were examined and optimized to have a sheet resistivity of 108 Omega/sq. The temperature dependence of the barrier height of the PDB diode has been investigated experimentally, showing positive temperature coefficient and, hence, better thermal stability. We have also defined the critical barrier height and derived its analytical expression, which gives the theoretically lowest possible barrier height of a PDB diode

Compact Left-handed Dual Mode Notch Bandstop Filter

Abstract: An innovative compact microstrip line left-handed dual mode notch bandstop filter is presented, showing that the size of the bandstop filter can be significantly reduced by employing the left-handed meta-materials. The fabricated filter has the size of 11 mm times 50 mm, five times smaller than that of the conventional filter of the same class. The filter has a center frequency of 1.12 GHz

Integrated Left-handed Metamaterials for RF/MMIC Miniaturization and Performance Enhancement

Abstract: Integrated left-handed (LH) metamaterials on GaAs RF/MMIC technology are presented. LH unit cells, transmission lines and filters are fabricated and characterized, showing that a step improvement in RF/MMIC size reduction can be achieved using LH technology. In addition, integrated LH circuits have exhibited broader operation bandwidth.

Integrated Left-Handed Metamaterials on MMIC Technology

Abstract: Super compact multilayer broadband left-handed (LH) metamaterials medium for RF/MMIC applications have been previously proposed and demonstrated by full wave and equivalent circuit analysis (Tong and Hu, 2005 and Horii et al., 2005). From references (Tong and Hu, 2005 and Horii et al., 2005), LH metamaterials have the potential to miniaturise circuits for low frequency applications. In this paper, we propose an integrated unit cell and transmission line, which has the advantages of simpler fabrication, convenient probe contactability and the potential integrates with MMIC technology. LH unit cell circuits have been developed, and the simulation and measurement results are presented. The miniaturised LH transmission line is also developed and the simulation and measurement results are presented

Compact and Broadband Coplanar Waveguide Left-Handed Metamaterial Transmission Line for RF/ MICC Application

Abstract: A GaAs solid state passive coplanar waveguide (CPW) left-handed metamaterial medium is proposed and validated by measured results. The unit cell of the fabricated structures has a size of 0.09 mm2. The left handedness range of the solid state left-handed structure extends from 2.3 GHz to 17.5 GHz. The compactness and broad left-handed operating bandwidth make the presented left-handed metamaterial be well incorporated with RF/MMIC applications