An analog MMIC phase modulator for X-band satellite transponder applications

The design and measured performance of a GaAs MMIC (monolithic microwave integrated circuit) analog linear phase modulator for the next-generation space-borne communications systems are presented. The analog phase shifter is based on the reflection-type hybrid coupled approach and uses a novel lumped quadrature hybrid and MESFET varactors as a building block. Three cascaded sections (with tapered varactor sizes) of this building block along with two high-isolation amplifiers have been realized in a single chip (96 mils*36 mils). This MMIC provides an X-band (8415+or-50-MHz) phase modulation with +or-2.6 radians (300 degrees ) of peak phase deviation, +or-2% of phase deviation linearity, 1.5-dB insertion loss, and better than 12-dB input and output return loss performance.<
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