Taper and forward-feed in GaAs MMIC distributed amplifiers

The authors consider an improved distributed-amplifier (DA) architecture which uses simultaneous inductance tapering and signal forward feeding to obtain additional degrees of freedom for optimization. The effects of losses on the high-frequency performance are investigated numerically using detailed MESFET models. Further simulations show how impedance tapering, forward-feed capacitors, and series-drain inductors can be used together to overcome the high-frequency losses, thereby maximizing the bandwidth. The approach is illustrated by the design and fabrication of a DA with a predicted gain of 6.9+or-0.7 dB over a bandwidth of 1-12 GHz. The results support the use of the forward-feed concept and also validate the hypothesis that induction tapering should increase gain and improve the input and output voltage standing-wave ratios. >