Two packaged monolithic microwave integrated-circuit (MMIC) mixers have been designed to operate as subharmonically pumped frequency down-converters in receivers of satellite- or ground-based digital communication systems. One operates a radio frequency (RF) between 17 and 20 GHz, the other at an RF between 22 and 32 GHz (see Figure 1). These MMICs are of a type described in "MMIC Converters for K- and Ka-Band Communications" (LEW-16752), NASA Tech Briefs, Vol. 23, No. 7 (July 1999), page 59. The approach taken in developing this type of MMIC is one of minimizing costs by relying on well established design practices and mature, commercially available processes for fabrication of MMIC chips.
Both mixers incorporate onboard local-oscillator (LO) amplifiers to reduce the required LO drive levels. The 22 -32-GHz mixer also incorporates an output [intermediate-frequency (IF)] amplifier. To reduce the sizes and thus the costs of the mixer chips, both mixers incorporate lumped circuit elements for matching of impedances(in contradistinction to the transmission-line impedance-matching elements customarily used for microwaves).
The specific practices and processes chosen for design and fabrication of the 17 -20-GHz MMIC are those of GaAs metal/semiconductor field-effect transistors (MESFETs) with 0.5-µm design rules, while those of electron-acceptor-doped high-electron-mobility transistors (p-HEMTs) with 0.25-µm design rules were chosen for the 22 -32-GHz MMIC. Figure 2 depicts the two MMIC chips. Both MMIC chips are integrated into ball-grid-array (BGA) packages, which are leadless ceramic interconnection substrates with tungsten/copper vias; the MMICs are inserted in these packages in surface-mount configurations and bonded in place by use of arrays of noncollapsing, hard balls made of a copper/silver eutectic alloy.
In tests, the 17 -20-GHz down-converter was found to perform well at RFs from 15 to 24 GHz, LO frequencies of 7 to 10.5 GHz, and IFs from 0 to 5 GHz. The 22 -32-GHz down-converter was found to perform well over the RF range from 22 to 32 GHz in tests in which the LO frequency was swept, along with the RF, to maintain an IF of 2 GHz.
This work was done by Paul Blount of Hittite Microwave Corp. for Glenn Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Electronic Components and Systems category.
Inquiries concerning rights for the commercial use of this invention should be addressed to
NASA Glenn Research Center
Commercial Technology Office
Attn: Steve Fedor
Mail Stop 4 —8
21000 Brookpark Road
Refer to LEW-16805.