A 220-260 GHz medium power variable gain amplifier MMIC with low phase variation

A variable gain amplifier (VGA) operating in the WR3 frequency range (220 to 325GHz) with low phase variation is presented. The VGA is carried out as balanced amplifier with a three-stage cascode amplifier in each path. The small-signal gain is 24.2dB with a 3 dB bandwidth of 43GHz ranging from 218.8 to 261.8GHz. Within a gain control rangeof 17dB the phase variation is below -5CR and +10CR. The large signal behavior shows a maximum output power Psat of 7.4 dBmat 240GHz with a saturated gain of 12dB. The MMIC was fabricated in a 50nm InGaAs technology and has a chip size of1.25 × 0.75mm2.