A theory of broadband matching for optical heterodyne receivers

A theory of broadband matching for an optical heterodyne receiver consisting of a semiconductor photodiode followed by an IF broadband amplifier is presented in this paper. It is assumed that a finite linear lumped lossless interstage network is used for the broadband matching of the optical receiver, and the restrictions thereby imposed by the diode on the gain of the optical receiver are obtained both in integral and nonintegral forms. Several types of rational function approximations to an ideal flat gain characteristic of the optical receiver are then considered, and synthesis procedures for thelossless interstage networks to realize these approximations are presented. Explicit expressions are given for the amount of tolerance of broadband performance obtained with these networks.