Passive FET MMIC linearizers for C, X, and Ku-band satellite applications

The design and measured performance of GaAs MMIC (monolithic microwave integrated circuits) linearizers for use with spaceborne traveling wave tube amplifiers (TWTAs) are presented. These linearizers operate at C, X, and Ku-band, and are based on a passive FET design similar to that of MMIC switches and attenuators. MESFET varactors and voltage variable resistors are used as control elements. More than 2.5 GHz of bandwidth is obtained at Ku-band with an improvement of greater than 10 dB in TWTA carrier-to-intermodulation ratio (C/I), and a phase change of less than 5 degrees . Linearizer insertion loss was reduced to below 8 dB at C-band and 10 dB at Ku-band. The MMICs also verified the soundness of the CAD (computer-aided design) modeling techniques used to develop the chips, and the value of the unique MMIC air bridge over metal tuning technique incorporated into the designs.<>