Calibrated RF time-domain measurement of non-linear devices in digital polar transmitter architecture

This paper presents a time-domain characterization of non-linear microwave devices driven by wideband modulated signal. A fully calibrated 4 channel time-domain measurement system is applied here for the characterization of an S-band 40 W GaN power amplifier used in digital polar delta-sigma modulation transmitter architecture. Measuring voltage/current time-domain waveforms at a high equivalent sampling rate of 15 times the carrier frequency, allows the visualization of the RF transient responses of the amplifier under test. This measurement instrument is also used to evaluate the trade-off between linearity and Power Added Efficiency (PAE) of the same power amplifier used in conventional architecture and in digital polar delta-sigma modulation transmitter architecture. It has been experimentally demonstrated that this last one allows a linearity improvement of 18 dBc and 16 points of PAE compared to conventional transmitter architecture.