An invariant alignability factor and its significance

The sensitivities of the port immittance to small immittance and large reactive changes of the self-immittance at the opposite port of a linear active two-port network are investigated. A new ´invariant alignability factor´, S, is defined as the inverse of the maximum modulus of the sensitivity. 6 is an invariant for interchange of the ports, arbitrary lossless terminations and immittance substitution. It precisely expresses the maximum interaction between the two ports and is related to earlier stability and performance factors, S can be evaluated by a simple experimental method. The power gain margin of any active linear two-port network is 8 nepers, when 8 is very small compared with unity. The upper limit of its maximum power gain for a given performance factor is inversely proportional to the square of 8.