Waveguide Power-Amplifier Module for 80 to 150 GHz

NASA’s Jet Propulsion Laboratory, Pasadena, California

A waveguide power-amplifier module capable of operating over the frequency range from 80 to 150 GHz has been constructed. The module comprises a previously reported power amplifier packaged in a waveguide housing that is compatible with WR-8 waveguides. (WR-8 is a standard waveguide size for the nominal frequency range from 90 to 140 GHz.) Because the amplifier in its unpackaged form was a single, fragile InP chip, it was necessary to use special probes to make electrical connections between the amplifier and test equipment in order to measure the power gain and other aspects of amplifier performance. In contrast, the waveguide poweramplifier module is robust and can be bolted to test equipment and to other electronic circuits with which the amplifier must be connected for normal operation. The amplifier in its unpackaged form was reported in "Power Amplifier With 9 to 13 dB of Gain from 65 to 146 GHz" (NPO-20880), NASA Tech Briefs, Vol. 25, No. 1 (January 2001), page 44.

The **Amplifier Module** features a housing that is compatible with WR-8 waveguides. (Note: The largest dimension of the wave-guide block is smaller than the size of a quarter.)

To recapitulate: the amplifier provides three stages of amplification, implemented by means of four InP high-electron- mobility transistors in a grounded coplanar waveguide circuit with lumped-element interstage and shunt capacitors. The circuit also features a unique coplanar waveguide powercombining structure in the output stage. The output radio-frequency power was measured to be 25 to 40 mW from 106 to 140 GHz. The figure shows selected aspects of the amplifier in its present packaged form. In addition to packaging in a waveguide housing, the amplifier was modified to suppress lowfrequency oscillations, to which the amplifier was previously susceptible because it had high gain at DC. The modifications consisted mostly of special placement of bypass capacitors and radio-frequency chokes within the package. The packaged amplifier was found to operate stably, and to produce a gain of at least 7 dB while producing output power of at least 10 mW at frequencies from 80 to 150 GHz.

This work was done by Lorene Samoska, Sander Weinreb, and Alejandro Peralta of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free online at www.techbriefs.com/tsp under the Semiconductors & ICs category. NPO-30576