Improved analysis for the intermodulation performance of amplifiers with envelope signal injection

Large signal analysis of a nonlinear amplifier excited by a multi-tone signal is presented. The special case of a four-tone signal comprising two equal-amplitude sinusoids and their injected envelope is considered in detail and the results are compared, whenever possible, with previously published experimental results. The results show that although the envelope-injection can result in an improvement in the third-order intermodulation, it degrades the fifth-order intermodulation performance compared with the no envelope-injection case. Moreover, the results show that improvement in third-order intermodulation can be achieved only for certain values of the phase angles of the components of the injected envelope.