INVARIANCE OF S-21 S-12 AND K-FACTOR UNDER PARALLEL OPERATION OF LINEAR 2-PORT DEVICES/

Based on a generalized circuit model for parallel-operated amplifiers with linear two-port devices, it has been proved that the S-parameter ratio S-21/S-12 and hence MSG (Maximum Stable Gain) are invariant as l ong as the devices have an identical value of S-21/S-12 and the input and output networks are reciprocal. The invariance of K-factor has bee n shown to hold for two cases: (i) devices are identical and input/out put networks are lossless and symmetric with respect to each device, a nd Oil identical admittances are added to the networks of case (i) so as to connect every device port with each other. Thus at least in thes e two cases, MAG (Maximum Available Gain) and U (Unilateral Gain) are invariant as well as MSG under parallel operation of linear two-port d evices. The invariance of S-21/S-12 and hence MSG applies to a variety of parallel-operated amplifiers such as distributed amplifiers and li near power amplifiers.