An Advanced Traveling Wave Matching Network for DC-12GHz Variable Gain Amplifier Design

A traveling wave matching (TWM) network is proposed for broadband variable gain amplifier design. The TWM network lessens input return loss and noise figure dependence on VGA’s gain, which is adjusted by biasing of the gain control circuit. A wide band (DC to 12 GHz) VGA with the novel TWM network as input matching is implemented in 2μm InGaP/GaAs HBT (fT of 29.5GHz) technology with die size of 1×2 mm2. As gain control voltage sweeps, the VGA shows a gain tuned from -15 dB to 15 dB and an average noise figure ranging from 8dB to 6.5dB, while S11 (lower than -20dB) and S22 (lower than -10dB) almost unchanged over the operation frequency band.