Broad-band distributed amplifier impedance-matching techniques

A circuit concept is developed which allows impedance transformations to be performed over extremely broad bandwidths. The transformation is obtained by coupling one or more input or output lines of a distributed amplifier into several output or input lines, respectively. The circuit technique is demonstrated by results for an amplifier for a 1:2 impedance transformation over a 2-20-GHz bandwidth. The amplifier yields a voltage standing wave ratio (VSWR) of better than 1.7:1 into 25 Ω at the input and better than 1.5:1 into 50 Ω at the output while maintaining a gain of 9±1 dB. An application of the technique to the broadband impedance-matching problem of a laser diode driver is discussed. The circuit has a gain of 8.5±1 dB from 0.5 to 12.5 GHz and better than 10 dB return loss at both the input and output