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A team from Caltech and Northrop Grumman Corporation, engaged in a project for NASA's Jet Propulsion Laboratory, has devised a single-stage amplifier that delivers 5 dB of gain at 340 GHz. This is among the highest gains per stage at this frequency reported at this time.

The device is a monolithic microwave integrated-circuit (MMIC) single-stage amplifier that contains an InP-based High-Electron-Mobility Transistor (HEMT) — plus coplanar-waveguide (CPW) transmission lines for impedance matching and input and output coupling. The layout is highly miniaturized — essential for high performance at operating frequencies in the hundreds of gigahertz.

This is one in a series of devices that are intermediate products of a continuing effort to develop advanced MMIC amplifiers for sub-millimeter wavelength imaging systems, scientific instrumentation, heterodyne receivers and other applications.

The HEMT in this amplifier has a gate length of 35 nm and two fingers each 15-nanometers wide. The CPWs have a ground-to-ground spacing of only 14 micrometers. The inclusion of quarter-wavelength-long CPWs for impedance matching and of on-chip shunt capacitors makes it possible to obtain about 5 dB of gain with respectable values of input and output return losses at the design frequency of 340 GHz. Moreover, the measurement data suggest the potential for a further increase in gain at frequencies above the 345-GHz limit of the test equipment used to perform the measurements.

This work was performed by David Pukala, Lorene Samoska, King Man Fung, and Todd Gaier of Caltech and W. R. Deal, Gerry Mei, Vesna Radisic, and Richard Lai of Northrop Grumman Corporation for NASA's Jet Propulsion Laboratory.

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