Vector signal generator gets envelope tracking option

Because of the specific power distribution of RF signals with modern communications standards such as LTE and WCDMA, power amplifiers generally exhibit poor efficiency since spare capacity has to be reserved for high crest factors. With envelope tracking, the amplifier supply voltage is controlled in such a way that it tracks the envelope of the RF signal. As a result, the amplifier always operates in a range close to its instantaneous maximum output power, considerably boosting amplifier efficiency. Using shaping functions, the amplifier can be optimised for linearity or efficiency.

This new option generates fully synchronous RF and envelope waveforms in a single instrument. Users can delay the RF waveform and the envelope waveform relative to each other by ±500 ns with 1ps resolution. It delivers an extremely low-noise envelope signal at the analogue baseband outputs. The signal generator calculates the envelope waveform from the baseband signals in real-time, so that all communications standards supported as well as custom waveforms can be used. A large selection of flexible shaping functions allows users to optimise the envelope in real-time.   

The envelope tracking parameters can be configured on the generator's straightforward graphical user interface. Automatic envelope voltage adaptation is available to speed up setup and testing time since the main parameters such as VCC voltage range, PAin range, DC modulator gain, DC offset and power offset only need to be entered once. Automatic recalculation of the envelope based on the power amplifier input level makes it possible to perform power sweeps over the amplifier's entire input range.  

The new R&S SMW-K540 software option will be presented at the European Microwave Week in Nuremberg in hall 7A, booth 106.