1GP104

Envelope Tracking with the SMW

5 Envelope Tracking with the SMW

5.1 Overview

In an envelope tracking test setup, a single SMW provides the two required test signals

(RF and corresponding envelope) for testing the PA in combination with the DC supply modulator. The envelope signal can be shaped in a flexible way and a time delay can be applied to achieve perfect synchronization of the two signals at the PA inputs.

SMW

V supply

Analog out

Envelope calculation

Shaping

Envelope voltage adaptation

Delay

Supply modulator

V cc

Baseband

I/Q

Up-converter

Leveling

RF

PA

The envelope signal is output at the analog I/Q output:

 at the “I” connector (single-ended)

 at the “I” and “I inverted” connectors (differential)

The envelope signal stimulates the DC supply modulator which then provides a modulated supply voltage (V cc

) to the PA.

RF signal

Envelope signal

I

Envelope signal

I inverted

The following sections give more information about the individual blocks shown in the logical block diagram above.

5.2 Baseband Signal

Any baseband signal can be used. The envelope tracking function works with all available digital standards (such as LTE, WLAN, etc.) and ARB waveforms. Downlink as well as uplink signals can be used for base station and user equipment test.

1GP104_1E Rohde & Schwarz Envelope Tracking and Digital Pre-Distortion Test Solution for RF Amplifiers 10