InP HEMT MMIC Low-Noise Amplifier for 65 to 110 GHz

NASA’s Jet Propulsion Laboratory, Pasadena, California

A monolithic microwave integrated circuit (MMIC) has been designed to function as a low-power-consumption, low-noise amplifier (LNA) at frequencies from about 65 to about 110 GHz. This MMIC incorporates TRW's state-of-the-art, InP-based, high-electron-mobility transistors (HEMTs) coupled with coplanar- waveguide (CPW) transmission lines, thin-film resistors, and thin-film capacitors. The MMIC is mounted in a waveguide module with CPW-to-waveguide transitions of the probe type (see figure).

A Four-Stage MMIC LNA is mounted in a split-block waveguide module. The dimensions of the MMIC chip are 2 by 0.73 by 0.075 mm.

An unusual feature of the circuit is a path for a pilot signal with a typical frequency of 500 MHz. This path is through the same transistors used to amplify the millimeter-wave signal. The pilot signal is applied through a pilot input terminal (the upper left pad in the figure) and appears at a pilot output terminal (the upper right pad in the figure). The low-level pilot signal is coupled from one bias circuit to the next and does not interact appreciably with the millimeter-wave signal. The pilot signal is meant to be used to measure fluctuations in the gain of the transistors; such measurements are useful in applications (e.g., radiometry) in which fluctuations in gain can affect measurements.

The MMIC is designed to operate in the presence of cooling by a suitable cryogenic apparatus. Seventeen waveguide modules containing copies of the MMIC were tested for noise temperature by use of a variable-temperature waveguide with a 20-dB attenuator and a precise diode temperature sensor. The range of noise temperatures over the 85-to-115-GHz frequency range was found to be 30 to 107 K at an operating temperature of 24 K. The noise at room operating temperature was found to range from 250 to 470 K. In other tests, the MMICs were found to be capable of producing 20 dB of gain while consuming as little as 1.4 mW of dc power.

This work was done by Todd Gaier and Sander Weinreb of Caltech, Neal Erickson of the University of Massachusetts, and Richard Lai of TRW for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Electronic Components and Systems category.

NPO-20752