Intelligible Crosstalk Between Frequency Modulated Carrers Through AM-PM Conversion

When two or more frequency modulated signals are transmitted simultaneously through a nonlinear device, intelligible crosstalk from one signal to another is a potential problem. Such a situation arises in connection with the multicarrier use of satellite transponders. In this paper, intelligible crosstalk arising from transmission vs frequency deviations followed by amplitude-to-phase (AM-PM) conversion is considered. The AM-PM conversion characteristics of the transponder are represented by a single constant coefficient determined through a simple measurement technique. Crosstalk ratios for an arbitrary carrier system are derived and experimental verification is presented for the two-carrier case.