A Large Signal Network Analyzer (LSNA) system has been configured to automatically engineer specific baseband voltage waveforms that, when injected into the output of an active device enable novel device linearization investigations. This is achieved using a formulation, generalized in the envelope domain, to describe the required baseband injection voltage. The advantage of this formulation is that it can be used to compute and then engineer the required baseband injection voltage signals, for arbitrary amplitude modulated envelopes, in terms of a limited set of describing coefficients. Using this approach, it is possible to determine the optimum baseband signal coefficients necessary to linearize a 10W Cree GaN HEMT device using baseband injection techniques. The formulation is validated by experimental investigation, using a 3-tone modulated signal, where the optimum output baseband signal for third and fifth order IMD suppression is successfully identified. For the optimum case, the observed level of IM3 and IM5 distortion was reduced to less than -56dBc whilst driving into 1.5 dB of compression.
- Multi-tone modulation
- non-linear distortion