11 | Keysight | N7614B Signal Studio for Power Amplifier Test - Technical Overview

Timing alignment

ETPS dynamically adjusts the power supply voltage to the PA. As defined in the MIPI™

Alliance’s eTrak standard, most ETPS have differential inputs and therefore, the envelope

waveform generator must have differential output. ETPS output is applied to the PA’s

supply line. This voltage has to be applied to the PA with precise timing relative to the

input RF signal. Typically the timing alignment between RF and envelope has to be less

than 1 ns. Rough timing adjustments between RF and envelope can be achieved with an

oscilloscope before connecting to the ETPA and ETPS. However, due to internal delays

in the ETPS and the RF PA, the final tuning has to be done with the ETPA output using

parameters such as EVM or ACLR. Precise timing adjustments, down to a fraction of a

nanosecond, may be required to optimize ET system performance.

Figure 12. Envelope tracking system simplified block diagram

N7614B Signal Studio Envelope Tracking for Power Amplifier test provides:

Envelope tracking key features

– Envelope generator can use 33522B/33622A AWG or a second MXG or EXG

– Envelope calculation can be from non-predistorted I/Q signal or pre-distorted I/Q

signal

– Envelope waveform can be imported from user-defined waveform

– Oversampling ratio for envelope can be user-defined

– Shaping input can be normalized I/Q amplitude or absolute RF output voltage

– Envelope waveform can be exported

– ETPS characteristic parameters can be user-defined

Shaping table

– Users provide the RF voltage to envelope voltage shaping table

– Supports the ET shaping table edition directly in the GUI

– Supports the ET shaping table open and save function

– Supports shaping table in real-time with MXG-B or EXG as envelope generator

Timing alignment

– Supports automatic alignment based on ACP measurement results

– Delay step can be settable as low as 1 ps

– Supports manual alignment based on ACP, EVM or time domain