Details of Grant 

EPSRC Reference:	GR/J06924/01
Title:	MONOLITHIC MILLIMETRE WAVE INTEGRATED CIRCUITS AT 94 AND 140 GHZ
Principal Investigator:	Howes, Professor M
Other Investigators:	Snowden, Professor C
Researcher Co-Investigators:
Project Partners:
Department:	Electronic and Electrical Engineering
Organisation:	University of Leeds
Scheme:	Standard Research (Pre-FEC)
Starts:	01 October 1993	Ends:	31 March 1997	Value (£):	285,819
EPSRC Research Topic Classifications:	RF & Microwave Technology
EPSRC Industrial Sector Classifications:	Electronics
Related Grants:
Panel History:
Summary on Grant Application Form
This is part of a collaborative project between the Universities of Cambridge [GR/H 94191], Glasgow [GR/J 15728], Kent [GR/J 07594] and Leeds [GR/J 06924]. The overall objective is to investigate the technology, modelling, design and characterisation of multifunction MMICs at W (75-110 GHz) and T(111-170 GHz) bands. Demonstrators will be provided. The Leeds contribution is concerned with:(i) the provision of pHEMT physical models,(ii) the design of voltage controlled oscillators at 94 GHz and 140 GHz and(iii) on wafer characterisation of MMIC circuit elements and subsystems at W band (funded by Leeds University).Progress:The physical model uses a quasi-two-dimensional approach for modelling HEMTs in which the driving force for electron transport (electric field) is in the x-direction only (source to drain). The current continuity, momentum and energy balance equations are used to describe electron dynamics in the conducting channel, taking into account electron heating. This calculation is coupled to a solution for the electron sheet density in the y-direction using a charge-control look-up table. A charge-control model is used to generate the look-up table which solves the coupled Poisson-Schrodinger equations in the y-direction and includes the variation of x-directed field. An analytical model is used to describe the buffer injection which greatly improves the computational efficiency of the solutions and gives excellent pinch-off at high drain voltage. Work is continuing to extend the physical model to account for the large signal performance of pHEMTs. Sensitivity analysis and reverse modelling is also being developed. A W-band measurement system has been purchased from Hewlett Packard/Cascade Microtech for carrying out the on-wafer characterisation of W-band devices and circuits. The accuracy of network analyser calibration and measurement repeatability at W-band is currently under investigation. TRL, LRM and SOLT calibrations have been considered using standards fabricated on alumina and on GaAs. On-wafer measurements have been performed on both passive circuits and active devices. Coplanar lines and shorted T structures have been measured to obtain predictions for electrical length and line loss. Measurements of pHEMTs has also been carried out at W-band to identify the Maximum Available Gain at 94GHz. A minimum of 5 mW output power is required from the local oscillator at 94GHz. Assuming a 10% efficiency this implies a that the active device must be capable of delivering 50mW at 94 GHz Thus the DC characteristics of the device should have a very low knee-voltage, (< 0.5 V), a gate to drain breakdown voltage around 7V and a minimum IDSS of 70mA. The design methodology is based on the synthesised negative conductance concept and the final oscillator will be realised using coplanar waveguide technology. The active device is connected in the common source configuration. In the absence of suitable devices a linear analysis of a 94GHz oscillator has been made based on a 94GHz pHEMT reported in the literature. This allows the oscillator to be designed for maximum power output at a specified operating frequency. Gate bias tuning is under consideration to provide the small amount of tuning bandwidth required. A large signal analysis will be used to determine spectral power density. The oscillator circuit topology is determined with circuit layout awaiting device availability.
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Organisation Website:	http://www.leeds.ac.uk