R&S SMW200A Generates RF and Envelope Signals in Real Time

October 3, 2013. Rohde & Schwarz has enhanced its new R&S SMW200A high-end vector signal generator by adding the R&S SMW K540 option for envelope tracking. This option enables quick and easy testing of envelope tracking power amplifiers for smartphones, base stations, and tactical radios.

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 optimized for linearity or efficiency.

Rohde & Schwarz meets the test requirements of chipset manufacturers by offering a solution that 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 1-ps resolution. Due to its performance characteristics, the R&S SMW200A delivers a low-noise envelope signal at the analog baseband outputs. The signal generator calculates the envelope waveform from the baseband signals in real time, so that all communications standards supported by the R&S SMW200A as well as custom waveforms can be used. A large selection of flexible shaping functions allows users to optimize 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 setup and testing time since the main parameters such as VCC voltage range, PA input 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.


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