Van Tuyen Vo

3-D low-loss coplanar waveguide transmission lines in multilayer MMICs

Newly developed transmission-line structures using the great flexibility of three-dimensional multilayer technology have been designed and fabricated. In this paper, we demonstrate that monolithic microwave integrated circuit (MMIC) coplanar waveguide transmission lines with a wide range of characteristic impedances can easily be designed using the multilayer technique. Furthermore, this implementation can avoid the well-known current crowding effects on the conductor edges minimizing dissipation loss. The system of three layers of metals and two layers of sandwich polyimide as dielectrics was employed. The fabricated transmission lines have been characterized providing a wide range of impedances from 10 to 70 Omega. In addition, the effects of unintentional horizontal and vertical coupling in multilayer MMICs have been investigated. The results indicated that an optimum separation of 75 mum is necessary for negligible coupling (~-30 dB)

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

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

Design and Realization of Spiral Marchand Balun Using CPW Multilayer GaAs Technology

Newly developed spiral Marchand baluns using the great flexibility of three-dimensional multilayer technology have been designed, optimized, fabricated, and measured. This paper demonstrates a monolithic microwave integrated circuits (MMIC) coplanar waveguide (CPW) spiral Marchand balun with good balance performance in a wide frequency range and compact size. Even/odd mode characteristic impedance analysis was applied to optimize the baluns performance. A 2.5D simulator ADS Momentum and a true 3D simulator Ansoft HFSS were used for EM simulations providing useful insight of the components design and optimizations as compared with the measured data. On-wafer RF measurements were carried out from 45MHz to 40GHz. The measured results shows small insertion loss, good amplitude and phase balance in a wide operating frequency band. A very compact size of 0.26 mm2 is achieved

High tangential signal sensitivity GaAs planar doped barrier diodes for microwave/millimeter-wave power detector applications

Tangential signal sensitivity (TSS) of GaAs planar doped barrier (PDB) detector diodes as low as -55 dBm at 35 GHz has been achieved. In comparison with that of reported devices, this value is 6-dBm better, implying the diodes can detect much lower power hence widening the dynamic range of microwave/millimeter-wave power detectors.

Broadband CPW multilayer directional couplers on GaAs for MMIC applications

This paper describes the design and characterisation of wide band multilayer directional couplers, fabricated on GaAs semi-insulating substrates with two conductive layers of gold separated by polyimide as a dielectric layer, operating at a centre frequency of 24 GHz. These components are very useful in the construction of multilayer MMICs and are compact and easy to design employing multilayer technology. High frequency simulations were carried out using Agilents Advanced Design System (ADS). In the design iteration, the thickness of the dielectric layer was varied to optimize the coupling and the isolation factors. The effects of metal overlap to improve the isolation factor of the directional couplers have been investigated in full. In this work, on-wafer RF measurements were carried out on the fabricated directional couplers using a HP85107A network analyser. Directional couplers with 90/spl deg/ phase angle, coupling factor of 5 dB and isolation of 10 dB were achieved over the 10 to 35 GHz frequency band. We further compare the results of simulations with those of measured data for final design optimisations.

Miniaturized Multilayer CPW pHEMT Amplifiers

Compact pHEMT amplifiers, which are composed of newly developed miniaturized multilayer inductors and capacitors, have been designed, fabricated and characterised. Their measured performances are presented and compared with those of amplifiers composed of conventional planar components. The results show that multilayer technology reduces the size of the amplifiers by approximately 50% while maintaining the same performance. In this paper we demonstrate that the developed compact components are integrated with pre-fabricated GaAs pHEMTs to form 3D MMICs providing excellent performance and space saving resulting in low cost manufacturing of future MMICs.

Miniature CPW Inductors for 3-D MMICs

Newly developed miniaturized CPW inductors using the great flexibility of three-dimensional multilayer technology have been designed and fabricated. Their measured performances are also presented and compared. The area of these inductors are almost four time smaller than that of planar spiral inductors while maintaining the same performance. The miniaturized inductors are constructed using a combination of three metal and two polyimide dielectric layers on semi-insulating GaAs substrates

Thermal Characterization of Compact Inductors and Capacitors for 3D MMICs

Increasing utility of 3D multilayer passive components in MMIC designs gives more flexibility with reduced cost and chip size. This also requires an in-depth analysis and characterization of these components over temperature and frequency. In this paper we present an experimental study of coplanar waveguide (CPW) based multilayer inductors and capacitors over a wide range frequency (45MHz to 40GHz) and temperature (25 to 200 degC). All the structures are fabricated on GaAs semi-insulating substrate. The experimental results show that the inductance and capacitance value remains fairly constant over this temperature range. Also the resonant frequency of the compact 3D inductor is constant over the entire temperature range. On the other hand Q factor of the inductor and capacitor decreases with increase in temperature

Design and Temperature Dependent Analysis of GaAs Multilayer Transmission Lines

In multilayer technology, the generated heat can not be dissipated effectively due to its multilayer structure. In this paper we designed, fabricated and characterised a group of GaAs multilayer coplanar waveguide (CPW) transmission lines and studied the effects of temperature on these components. Furthermore a de-embedding technique has been applied and the effect of de-embedding shown to be critical in removing the pads parasitics. The temperature dependents of the transmission lines are carefully analyzed from -25degC to 125degC and the results indicated that the characteristic impedances and effective dielectric constants of the transmission lines remained constant within the temperature range. These results are reported for the first time and provide an insight into the design optimization of multilayer circuits for compact 3D MMIC applications.

Compact 3D MMIC spiral baluns using multilayer CPW technology

This paper describes the design, fabrication and characterization of a novel broadband monolithic passive spiral Marchand balun using the great flexibility of three-dimensional multilayer technology by The Electromagnetics Centre, The University of Manchester. As a measured result, the insertion loss better than -5 dB including the 3 dB power splitting loss over the 15 to 27 GHz bandwidth and the return loss better than -30 dB have been achieved at the perfectly matched frequency of 20 GHz. Amplitude and phase imbalance of 1 dB and 10 degrees, respectively, were achieved over the frequency band from 15 to 27 GHz. The balun occupies a small area as 0.26 mm/sup 2/.