Tech Briefs

MMIC Amplifier Produces Gain of 10 dB at 235 GHz

This is the fastest MMIC amplifier reported to date.

The first solid-state amplifier capable of producing gain at a frequency >215 GHz has been demonstrated. This amplifier is an intermediate product of a continuing effort to develop amplifiers having the frequency and gain characteristics needed for a forthcoming generation of remote-sensing instruments for detecting water vapor and possibly other atmospheric constituents. There are also other potential uses for such amplifiers in wide-band communications, automotive radar, and millimeter- wave imaging for inspecting contents of opaque containers.

The MMIC Amplifier described in the text is shown mounted for testing with custom wafer probes for testing at 220 to 325 GHz.
This amplifier was fabricated as a monolithic microwave integrated- circuit (MMIC) chip containing InP high-electron-mobility transistors (HEMTs) of 0.07-μm gate length on a 50-μm-thick InP substrate. The passive components on the chip are of the microstrip type and were designed by use of advanced electromagnetic- behavior-simulating software. The amplifier contains three stages of HEMTs with matching networks that comprise microstrip transmission lines and metal/insulator/metal capacitors. Bias is supplied via transmission-line networks with bypass capacitors on the gate and drain sides of the HEMTs.

The performance of the amplifier was measured by use of the instrumentation system described in “Equipment for On-Wafer Testing From 220 to 325 GHz” (NPO-40955), NASA Tech Briefs, Vol. 30, No. 1 (January 2006), page 38. This instrumentation system, equivalent to a two-port vector network analyzer, was equipped with custom wafer probes (see figure) designed for the noted frequency band, which is that of WR-3 waveguides [waveguides having a standard rectangular cross section of 0.0340 by 0.0170 in. (0.8636 by 0.4318 mm)]. Among other things, the measurements showed a peak gain of 10 dB at a frequency of 235 GHz.

This work was done by Douglas Dawson, King Man Fung, Karen Lee, Lorene Samoska, Mary Wells, Todd Gaier, and Pekka Kangaslahti of Caltech; and Ronald Grundbacher, Richard Lai, Rohit Raja, and Po-Hsin Liu of NGST for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at under the Semiconductors & ICs category. NPO-42202

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MMIC Amplifier Produces Gain of 10 dB At 235 GHz (reference NPO-42202) is currently available for download from the TSP library.

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