Intermodulation distortion of cascaded transistors

Intermodulation distortion performance of cascaded transistors is analyzed using a nonlinear frequency-dependent model for the transistor and with Volterra series as an analysis tool. The objective of this study is to determine the optimum cascade that has high gain and good modulation performance especially for higher frequencies. A particular application is in long-haul, analog, solid-state coaxial systems where intermodulation distortion is a critical problem. Both experimental as well as computer results are used in this analysis. It is shown, for example, that certain low distortion configurations can exhibit high distortion when cascaded. A few optimum cascade configurations are discussed in detail.