R&S®SMBVB-K540, R&S®SMBVBK541
Envelope Tracking and AM/AM,
AM/PM Predistortion
User Manual
(;ÜßÏ2)
1178816502
Version 07
This document describes the following software options:
●
R&S®SMBVB-K540 Envelope Tracking (1423.7701.xx)
●
R&S®SMBVB-K541 AM/AM, AM/PM Predistortion (1423.7718.xx)
This manual describes firmware version FW 5.00.044.xx and later of the R&S®SMBV100B.
© 2021 Rohde & Schwarz GmbH & Co. KG
Mühldorfstr. 15, 81671 München, Germany
Phone: +49 89 41 29 - 0
Email: info@rohde-schwarz.com
Internet: www.rohde-schwarz.com
Subject to change – data without tolerance limits is not binding.
R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG.
Trade names are trademarks of the owners.
1178.8165.02 | Version 07 | R&S®SMBVB-K540, R&S®SMBVB-K541
The following abbreviations are used throughout this manual: R&S®SMBVB100B is abbreviated as R&S SMBVB; the license types
02/03/07/11/13/16/12 are abbreviated as xx.
R&S®SMBVB-K540, R&S®SMBVB-K541
Contents
1 Welcome to the R&S SMBVB-K54x options........................................ 5
1.1 Accessing the required settings..................................................................................6
1.2 What's new.....................................................................................................................6
1.3 Documentation overview..............................................................................................6
1.3.1 Getting started manual....................................................................................................6
1.3.2 User manuals and help................................................................................................... 7
1.3.3 Service manual............................................................................................................... 7
1.3.4 Instrument security procedures.......................................................................................7
1.3.5 Printed safety instructions............................................................................................... 7
1.3.6 Data sheets and brochures............................................................................................. 7
1.3.7 Release notes and open source acknowledgment (OSA).............................................. 8
Contents
1.3.8 Application notes, application cards, white papers, etc...................................................8
1.4 Scope............................................................................................................................. 8
1.5 Notes on screenshots...................................................................................................8
2 Generation of envelope tracking signals...........................................10
2.1 Required options.........................................................................................................10
2.2 About the envelope tracking......................................................................................10
2.2.1 Envelope voltage adaptation modes............................................................................. 11
2.2.2
2.2.3 Envelope shaping and shaping methods...................................................................... 12
Signal parameters for testing according to the eTrak® specification.............................12
2.3 General RF envelope settings....................................................................................21
2.4 Envelope settings....................................................................................................... 29
2.5 Shaping settings......................................................................................................... 31
2.6 Edit I/Q envelope shape settings...............................................................................40
2.7 Polynomial coefficients settings............................................................................... 43
3 Applying digital predistortion............................................................. 46
3.1 Required options.........................................................................................................46
3.2 About digital predistortion......................................................................................... 46
3.2.1 Defining the power level of the generated signal.......................................................... 47
3.2.2 Defining the correction values.......................................................................................48
3.2.3 Finding out the correction values.................................................................................. 51
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3.3 Digital predistortions AM/AM and AM/PM settings..................................................52
3.3.1 General settings............................................................................................................ 53
3.3.2 Predistortion settings.....................................................................................................55
3.3.3 Edit predistortion table settings..................................................................................... 60
3.3.4 Polynomial coefficients settings.................................................................................... 62
3.3.5 Normalized data settings...............................................................................................66
4 How to generate a control signal for power amplifier envelope
tracking tests........................................................................................68
5 How to apply a DPD to improve the efficiency of RF PAs................72
6 Remote-control commands.................................................................77
6.1 SOURce:IQ:OUTPut subsystem................................................................................ 78
6.2 SOURce:IQ:OUTPut:ENVelope commands.............................................................. 80
Contents
6.3 SOURce:IQ:DPD subsystem...................................................................................... 95
List of commands...............................................................................111
Index....................................................................................................114
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1 Welcome to the R&S SMBVB-K54x options
The R&S SMBVB-K540 is a software option that allows you to generate an envelope
tracking signal, that follows the envelope variation of the RF signal.
R&S SMBVB-K540 key features
●
Baseband signal, RF signal, and envelope signal generation out of one instrument
●
Envelope signal derived directly and in real time from the baseband signal
●
Fully synchronous envelope and RF signal with optional delay compensation for
time alignment of the envelope signal
●
Simultaneous output of envelope and inverted envelope signal
●
Flexible envelope shaping based on different algorithms incl. a build-in table shaping editor
●
Import/export interface for files describing shaping functions
●
Real-time display of the characteristics of the envelope signal
Welcome to the R&S SMBVB-K54x options
The R&S SMBVB-K541 is a software option that adds functionality to define and apply
AM/AM and AM/PM predistortions.
R&S SMBVB-K541 key features
●
Applying user-defined AM/AM and AM/PM digital predistortions directly on the digital baseband signal
●
Digital predistortions are applied directly and in real time to the baseband signal,
i.e. to any Digital Standard signal or with ARB waveforms
●
Separate or superimposed AM/AM or AM/PM predistortion also with variable order
in the processing flow
●
Flexible shaping of the predistortion functions based on a polynomial function and
a build-in table editor
●
Import/export interface for files describing the predistortion functions, i.e. load of
AM/AM and AM/PM tables directly from characterization software
●
Real-time display of the correction functions
●
In instruments equipped with the option R&S SMBVB-K540, digitally predistorted
baseband signal, RF signal, and envelope signal generation out of one instrument
This user manual contains a description of the functionality that the application provides, including remote control operation.
All functions not discussed in this manual are the same as in the base unit and are
described in the R&S SMBV100B user manual. The latest version is available at:
www.rohde-schwarz.com/manual/SMBV100B
Installation
You can find detailed installation instructions in the delivery of the option or in the
R&S SMBV100B service manual.
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1.1 Accessing the required settings
To open the dialog with Envelope Tracking settings
1. In the block diagram of the R&S SMBV100B, select the "I/Q OUT" connector to
unfold the "I/Q Analog" block.
A dialog box opens that displays the provided general settings.
2. Select "I/Q Analog > I/Q Analog Outputs > General".
3. Select "RF Envelope > On".
To open the dialog with DPD settings
► In the block diagram of the R&S SMBV100B, select "I/Q Mod > Digital Predistortion
> AM/AM AM/PM".
A dialog box opens that displays the provided settings.
Welcome to the R&S SMBVB-K54x options
Documentation overview
The signal generation is not started immediately. To start signal generation with the
default settings, select "State > On".
1.2 What's new
This manual describes firmware version FW 5.00.044.xx and later of the
R&S®SMBV100B.
Compared to the previous version there are editorial changes only.
1.3 Documentation overview
This section provides an overview of the R&S SMBV100B user documentation. Unless
specified otherwise, you find the documents on the R&S SMBV100B product page at:
www.rohde-schwarz.com/manual/smbv100b
1.3.1 Getting started manual
Introduces the R&S SMBV100B and describes how to set up and start working with the
product. Includes basic operations, typical measurement examples, and general information, e.g. safety instructions, etc. A printed version is delivered with the instrument.
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1.3.2 User manuals and help
Separate manuals for the base unit and the software options are provided for download:
●
Base unit manual
Contains the description of all instrument modes and functions. It also provides an
introduction to remote control, a complete description of the remote control commands with programming examples, and information on maintenance, instrument
interfaces and error messages. Includes the contents of the getting started manual.
●
Software option manual
Contains the description of the specific functions of an option. Basic information on
operating the R&S SMBV100B is not included.
The contents of the user manuals are available as help in the R&S SMBV100B. The
help offers quick, context-sensitive access to the complete information for the base unit
and the software options.
All user manuals are also available for download or for immediate display on the Internet.
Welcome to the R&S SMBVB-K54x options
Documentation overview
1.3.3 Service manual
Describes the performance test for checking compliance with rated specifications, firmware update, troubleshooting, adjustments, installing options and maintenance.
The service manual is available for registered users on the global Rohde & Schwarz
information system (GLORIS):
https://gloris.rohde-schwarz.com
1.3.4 Instrument security procedures
Deals with security issues when working with the R&S SMBV100B in secure areas. It
is available for download on the Internet.
1.3.5 Printed safety instructions
Provides safety information in many languages. The printed document is delivered with
the product.
1.3.6 Data sheets and brochures
The data sheet contains the technical specifications of the R&S SMBV100B. It also
lists the options and their order numbers and optional accessories.
The brochure provides an overview of the instrument and deals with the specific characteristics.
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See www.rohde-schwarz.com/brochure-datasheet/smbv100b
1.3.7 Release notes and open source acknowledgment (OSA)
The release notes list new features, improvements and known issues of the current
firmware version, and describe the firmware installation.
The open-source acknowledgment document provides verbatim license texts of the
used open source software.
See www.rohde-schwarz.com/firmware/smbv100b
1.3.8 Application notes, application cards, white papers, etc.
These documents deal with special applications or background information on particular topics.
See www.rohde-schwarz.com/application/smbv100b
Welcome to the R&S SMBVB-K54x options
Notes on screenshots
1.4 Scope
Tasks (in manual or remote operation) that are also performed in the base unit in the
same way are not described here.
In particular, it includes:
●
Managing settings and data lists, like saving and loading settings, creating and
accessing data lists, or accessing files in a particular directory.
●
Information on regular trigger, marker and clock signals and filter settings, if appropriate.
●
General instrument configuration, such as checking the system configuration, configuring networks and remote operation
●
Using the common status registers
For a description of such tasks, see the R&S SMBV100B user manual.
1.5 Notes on screenshots
When describing the functions of the product, we use sample screenshots. These
screenshots are meant to illustrate as many as possible of the provided functions and
possible interdependencies between parameters. The shown values may not represent
realistic usage scenarios.
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The screenshots usually show a fully equipped product, that is: with all options installed. Thus, some functions shown in the screenshots may not be available in your particular product configuration.
Welcome to the R&S SMBVB-K54x options
Notes on screenshots
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2 Generation of envelope tracking signals
Envelope tracking (ET) is a method used by modern power amplifiers (PA) to improve
their efficiency, especially when amplifying RF signals with a high peak to average
power (PAPR). An envelope tracking detector "tracks" the power variations in the input
signal of the PA. The PA then varies synchronously to this variation the supply voltage
vcc at its end amplifying stage.
This section introduces the concept of the envelope tracking functionality and the way
it is implemented in the R&S SMBV100B.
Refer to Chapter 4, "How to generate a control signal for power amplifier envelope
tracking tests", on page 68 for step-by-step instruction on how to use the provided
function.
2.1 Required options
Generation of envelope tracking signals
About the envelope tracking
The equipment layout for generation and output of envelope tracking signal includes:
●
Base unit
●
Option differential analog I/Q outputs (R&S SMBVB-K17)
●
Option envelope tracking (R&S SMBVB-K540)
●
Optional option AM/AM AM/PM predistortion (R&S SMBVB-K541)
For more information, see data sheet.
2.2 About the envelope tracking
The R&S SMBV100B allows you to generate an envelope tracking signal, that follows
the envelope variation of the RF signal.
Principle of the envelope tracking
The Figure 2-1 shows a simplified test setup for testing of a PA with an envelope tracking. This illustration is intended to explain the principle in general, not all connections
and required equipment are considered.
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Figure 2-1: Simplified test setup for power amplifier envelope tracking tests
The R&S SMBV100B in this setup is configured to generate both, an RF signal with
complex modulation scheme and an envelope signal, that follows the envelope variation of this RF signal. A suitable test signal is, for example, an EUTRA/LTE DL signal.
Generation of envelope tracking signals
About the envelope tracking
The R&S SMBV100B generates the envelope signal directly from the baseband signal.
The envelope signal is a voltage signal, with voltage level V
power of the RF signal (√[I(t)2+Q(t)2]) of the corresponding path. If you do not apply a
shaping function, the envelope signal linear dependent follows the variation of the RF
signal's envelope.
The envelope signal is output at the I out and I Bar out rear panel connectors. This
envelope signal is then further fed to an external DC modulator.
The PA receives the RF input signal and the dynamically adapted supply voltage vcc.
Ideally, the PA gain stays constant.
Suitable baseband signal to observe the effect of the envelope tracking settings
To simplify the explanation in the following sections, we use a simple ramp function as
a baseband signal modulated on the RF carrier.
Other suitable baseband signals are signals with relative constant envelope. You find a
choice of predefined signals in the "Baseband > Custom Digital Mod > Set according to
standard" dialog. With the default settings in this dialog, you can observe the generated envelope signal and the effects of enabled shaping.
2.2.1 Envelope voltage adaptation modes
proportional to the
out
In the R&S SMBV100B, you define the voltage of the generated envelope signal using
one of the following modes:
●
Auto Power/Normilized Envelope Voltage Adaptation:
In this mode, you define the desired input characteristics of the power amplifier.
Based on these values and depending on the crest factor of the generated signal,
the R&S SMBV100B calculates:
– The voltage on the I out/I Bar out connectors (V
Min/Max) and a bias (Bias),
out
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– The RMS level of the RF signal
The auto voltage adaptation mode is a suitable choice, if you have knowledge on
the power amplifier components and characteristics. Common PA characteristics
are the supply voltage Vcc, the input power PEPin required for working in the linear
range and the gain characteristics of the external DC modulator.
You find the required values in the documentation of your power amplifier, for
example in its data sheet.
●
Manual Envelope Voltage Adaptation:
In this mode, you can also define the operating range of the power amplifier based
on a pre-gain and a post-gain range. Based on these values, the instrument calculates the supply voltage Vcc.
All modes support envelope shaping.
Generation of envelope tracking signals
About the envelope tracking
2.2.2
Signal parameters for testing according to the eTrak
In the R&S SMBV100B, you can select one of the predefined eTrak® interface types so
that the generated signal is conformed with the MIPI®Alliance specification "Analog
Reference Interface for Envelope Tracking Specification".
Table 2-1: Default parameters per eTrak® Interface Type
Parameter 1.2 Vpp 1.5 Vpp 2 Vpp
I/Q output Type Differential Differential Differential
Bias 500 mV 600 mV 900 mV
Vpp Max 1.2 V 1.5 V 2 V
Vpp Max 1.2 V 1.5 V 2 V
Bipolar Input On On On
2.2.3 Envelope shaping and shaping methods
Envelope shaping is a method that uses functions to describe the relationship between
supply voltage and RF input power. An envelope shaping function is a trade-off
between effectivity and improved linearity of the PA.
®
specification
In the R&S SMBV100B, you can select the way you define the shaping function. You
can choose between:
●
2 predefined simple linear functions
(see Chapter 2.2.3.1, "About the linear functions", on page 13)
●
3 detroughing functions with a configurable factor
(see Chapter 2.2.3.2, "About the detroughing function", on page 14)
●
A polynomial function with up to 10 polynomial coefficients
(see Chapter 2.2.3.3, "About the polynomial function", on page 14)
●
A shaping function defined as a shaping table
(see Chapter 2.2.3.4, "About the shaping table", on page 15)
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●
To set the correction values in raw format with a single remote control command
(see Chapter 2.2.3.5, "Shaping function in raw data format", on page 16)
The linear, the detroughing and the polynomial shaping functions are mathematical
expressions that are described as function of the variable x, see Table 2-2.
Table 2-2: Definition of the variable x depending on the envelope voltage adaptation mode
"Envelope Voltage Adaptation" x
Generation of envelope tracking signals
About the envelope tracking
Auto Power x = Vin - V
Auto Normalized x = Vin/V
Manual x = V
The mathematical expressions and further information on the shaping functions are
provided in the corresponding sections.
See also Chapter 2.2.3.6, "Converting shaping functions and understanding the dis-
played values", on page 16.
● About the linear functions........................................................................................13
● About the detroughing function............................................................................... 14
● About the polynomial function.................................................................................14
● About the shaping table.......................................................................................... 15
● Shaping function in raw data format........................................................................16
● Converting shaping functions and understanding the displayed values................. 16
2.2.3.1 About the linear functions
The linear shaping can be used for less demanding applications, simple analysis, and
the first interactions by designing the optimum envelope shape. Because the shaping
gain of the linear function is 0 dB, in "Envelope Voltage Adaptation > Manual" mode
this function is suitable for determining the "Pre-/Post-Gain" values (see Example "Cal-
culating the current VCC in "Manual" mode" on page 20).
in, min
x ≥ 0
in,max
Env/VEnv,max
Provided are two linear functions, where each of them depends on the "Envelope Voltage Adaptation" mode:
●
Linear (Voltage)
– f(x) = x in "Auto Normalized/Manual"
– f(x) = b*x + V
●
Linear (Power)
–
f(x) = x2 in "Auto Normalized/Manual"
–
f(x) = b*x2 + V
in "Auto Power"
cc,min
in "Auto Power"
cc,min
Where:
●
The variable x depends on the "Envelope Voltage Adaptation" mode, see
Table 2-2.
●
The constant b is calculated as:
b = (V
cc,max
- V
cc,min
)/(V
in,max
- V
in,min
)
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See also Chapter 2.2.3.6, "Converting shaping functions and understanding the dis-
played values", on page 16.
2.2.3.2 About the detroughing function
Detroughing functions are well-defined mathematical functions that prevent that the
supply voltage Vcc drops down to zero or falls under specified limits. That is, they pre-
vent that the signal is clipped.
Provided are the following functions:
●
f(x) = x + d*e
●
f(x) = 1 - (1 - d)*cos(x*pi/2)
●
f(x) = d + (1 - d)*x
-x/d
a
Where:
●
x is a variable, that depends on the "Envelope Voltage Adaptation" mode, see
Table 2-2
●
a is the Exponent (a).
●
d is the Detroughing Factor (d), that limits the supply voltage Vcc in the low-power
region and controls the shaping.
The detroughing factor (d) can be set manually or derived from the selected V
value. In the latter case, it is calculated as follows:
d = V
cc,min/Vcc,max
See Couple Detroughing Factor with Vcc.
A "Detroughing Factor = 0" defines a linear function.
Generation of envelope tracking signals
About the envelope tracking
cc
See also Chapter 2.2.3.6, "Converting shaping functions and understanding the dis-
played values", on page 16.
2.2.3.3 About the polynomial function
The polynomial function is an analytical method to describe a shaping function. The
polynomial function is defined as follows:
f(x) = a0 + ∑(an*xn), where n ≤10 and:
●
Depending on the "Envelope Voltage Adaptation" mode, f(x) is:
– f(x) = Vcc(x) in "Auto Power"
– f(x) = Vcc/V
●
The polynomial order n, the polynomial constant a0, and polynomial coefficients a
(x) in "Auto Normalized/Manual"
cc,max
to an are user-definable, see Chapter 2.7, "Polynomial coefficients settings",
on page 43
●
x depends on the "Envelope Voltage Adaptation" mode, see Table 2-2
The default polynomial function with n = 1, a0 = 0 and a0 = 1 describes a linear function.
See also:
●
Figure 2-13
0
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●
Chapter 2.2.3.6, "Converting shaping functions and understanding the displayed
values", on page 16.
File format of the polynomial function file
You can store a polynomial function in a file or even define the polynomial coefficients,
store them as a file and load this file into the instrument. The polynomial files are files
with extension *.iq_poly.
The file contains an optional header # Rohde & Schwarz - IQ Output
Envelope Polynomial Coefficients # a0,a1,a2,... and a list of commaseparated coefficient values.
Example: Polynomial function file content
# Rohde & Schwarz - IQ Output Envelope Shaping Table
# a0,a1,a2,...
0.135,0.91,0.34,-0.59,-0.11
2.2.3.4 About the shaping table
Generation of envelope tracking signals
About the envelope tracking
The envelope shaping table is a widely used method to define the shaping function.
This kind of definition is suitable if you have knowledge on or aim to achieve an exact
relation between supply voltage and RF input power. For example, with suitable settings, the shaping table can precisely describe the transition region of the PA.
You can receive information on suitable envelope shaping values form the power
amplifier manufacturer.
In the R&S SMBV100B, there are two ways to define a shaping table function:
●
Externally
Create a shaping table file as a CSV file with Microsoft Excel, with a Notepad or a
similar tool. Save it with the predefined extension, transfer it to and load it into the
instrument.
See also "File format of the shaping table file" on page 15.
●
Internally
Use the built-in editor table editor, see Chapter 2.6, "Edit I/Q envelope shape set-
tings", on page 40.
File format of the shaping table file
The shaping table files are files with predefined extension and simple file format, see
Table 2-3.
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Table 2-3: Shaping table files: format and extensions
"Envelope Voltage Adaptation" File extension Header (optional)
Generation of envelope tracking signals
About the envelope tracking
Auto Power
Auto Normalized/Manual
*.iq_lutpv # Rohde & Schwarz - IQ Output
*.iq_lut # Rohde & Schwarz - IQ Output
The header is optional. The file content is list of up to 4000 comma-separated value
pairs; a new line indicator separates the pairs.
Example: Shaping table file content (*.iq_lut file)
# Rohde & Schwarz - IQ Output Envelope Shaping Table
# Vin/Vmax,Vcc/Vmax
0.3,0.4
0.35,0.45
0.56,0.55
0.4,0.5
0.6,0.65
0,0.135
2.2.3.5 Shaping function in raw data format
Envelope Shaping Table
# Power[dBm],Vcc[V]
Envelope Shaping Table
# Vin/Vmax,Vcc/Vmax
The shaping values are defined directly, with a single remote control command. You
define up to 4000 comma-separated value pairs, describing the Vin/Vmax,Vcc/Vmax
or Power[dBm],Vcc[V].
Example:
SOURce1:OUTPut:ANALog:ENVelope:SHAPing:PV:FILE:DATA 0,0, 0.1,0.2, 1,1
See:
●
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:SHAPing:FILE:DATA
on page 92
●
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:SHAPing:PV:FILE:
DATA on page 92
●
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:SHAPing:FILE:NEW
on page 92
●
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:SHAPing:PV:FILE:NEW
on page 92
2.2.3.6 Converting shaping functions and understanding the displayed values
If an envelope function is defined, the "Shaping" dialog displays the diagram of the
resulting envelope shape.
See for example Figure 2-7.
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Several parameters influence the displayed information:
●
The selected "Envelope Voltage Adaptation" determines whether the x-axis uses
normalized or linear values
●
The selected "Graphic Configuration > Scale" sets the x-axis units
●
The selected VccMin/Max and PEPinMin/Max values set the borders of the clipping
areas
●
The selected "Shaping" function and the parameters influence the envelope shape.
The illustration on Figure 2-2 shows how these parameters influence a linear shaping
function.
Generation of envelope tracking signals
About the envelope tracking
Figure 2-2: Understanding the displayed values ("Shaping > Linear (Voltage)")
Shaded area = Area where the signal is clipped and the envelope signal is held constant
1a, 1b, 2a, 2b = V
Shaping = Linear (Voltage)
3a = Linear function (dashed line) in "Auto Power" mode, if V
3b = Linear function in "Auto Power" mode, if V
4a = Linear function (dashed line) in "Auto Normalized" mode, if V
4b = Linear function in "Auto Normalized" mode, if V
V
in
VccNorm = Vcc in "Auto Normalized" mode
VccPow
0
VccPow
1
cc,min/Vcc,max
= Operating point
= Vcc in "Auto Power" mode and V
= Vcc in "Auto Power" mode and V
and PEPinMin/Max values that set the borders of the clipping areas
= 0 V
cc,min
> 0 V
cc,min
= 0 V
cc,min
> 0 V
cc,min
= 0 V
cc,min
> 0 V
cc,min
For information on the provided shaping functions and their formulas, see:
●
Chapter 2.2.3.1, "About the linear functions", on page 13
●
Chapter 2.2.3.2, "About the detroughing function", on page 14
●
Chapter 2.2.3.3, "About the polynomial function", on page 14
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Generation of envelope tracking signals
The group of examples in this section uses the same linear shaping function to explain
the representation in the different voltage adaptation modes. The example explains the
displayed values and how they are calculated and converted. The same principle
applies for the other shaping methods.
Common settings
●
"Envelope Voltage Adaptation > Auto Power"
●
Vcc Max = 1 V
●
PEPinMin = -30 dBm corresponds to V
●
PEPinMax = 0 dBm corresponds to V
●
Pin = -15 dBm corresponds Vin = 0.04 V
●
PEP = -3.4 dB
●
"Shaping > Linear (Voltage)"
"Graphic Scale > Power" "Graphic Scale > Voltage"
= 0.0071 V
in,min
= 0.2236 V
in,max
About the envelope tracking
Example: Calculating the current VccPow0 ("Auto Power" mode, Vcc Min = 0 V)
Configuration as described in Common settings and:
●
V
= 0 V
cc,min
●
f (x) = b*x + V
cc,min
(see Chapter 2.2.3.1, "About the linear functions", on page 13)
VccPow0 = [(V
cc,max
- V
cc,min
)/(V
in,max
- V
)] * (Vin - V
in,min
in,min
) + V
cc,min
VccPow0 = [(1 - 0)/(0.2236 - 0.0071)]*(0.04 - 0.0071) + 0
VccPow0 = 0.151 V
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Example: Calculating the current VccPow1 ("Auto Power" mode, Vcc Min > 0 V)
Configuration as described in Common settings and:
●
V
= 200 mV
cc,min
VccPow1 = [(V
cc,max
- V
VccPow1 = [(1 - 0.2)/(0.2236 - 0.0071)]*(0.04 - 0.0071) + 0.2
VccPow1 = 0.321 V
cc,min
)/(V
in,max
- V
Generation of envelope tracking signals
About the envelope tracking
)] * (Vin - V
in,min
in,min
) + V
cc,min
Example: Calculating the current VccNorm ("Auto Normalized" mode)
Configuration as described in Common settings and:
●
"Envelope Voltage Adaptation > Auto Normalized"
●
The x-axis shows the normalized values Vin/V
in,max
;
The operating point with Vin = 0.04 V corresponds to
Vin/V
●
f (x) = x, i.e.
VccNorm = Vin/V
= 0.04 / 0.2236 = 0.178
in.max
in,max
VccNorm = 0.178 V
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Generation of envelope tracking signals
About the envelope tracking
If the V
●
If 0 < Vin/V
●
If Vin/V
For the previous example, if V
value is changed (V
cc,min
≤ V
in,max
> V
in,max
cc,min
> 0 V), then the following applies:
cc,min
, the signal is clipped and VccNorm = V
cc,min
, then VccNorm = Vin/V
= 200 mV, that VccNorm = V
cc,min
in,max
cc,min
cc,min
= 0.2 V.
Example: Calculating the current VCC in "Manual" mode
In "Envelope Voltage Adaptation > Manual" mode, set the parameter "Pre-Gain = PEP
= - 3.4 dB".
The displayed shaping function resembles the shaping function in "Auto Normalized"
mode; the same formulas apply, too.
You can also query the VCC values for any specified x in the supported voltage adaptation mode and units.
See [:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VCC:VALue?
on page 89.
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Additional information
The described principle applies for any shaping function.
Only if linear shaping is used, the VCCNorm can also be directly converted to VCCPow
according to the following formula:
f
Pow
(x) = [f
Norm
(x) - V
in,min/Vin,max
]*[(V
cc,max
Generation of envelope tracking signals
General RF envelope settings
- V
cc,min
)/(1 - V
in,min/Vin,max
)]
For example, if f
(x) = VCCNorm = 0.178 V, f
Norm
VccPow0 = [0.178 - 0.0071/0.2236]*[(1 - 0)/(1 - 0.0071/0.2236)]
VccPow0 = 0.151 V
2.3 General RF envelope settings
Access:
1. In the block diagram, select the "I/Q OUT" connector to unfold the "I/Q Analog"
block.
2. Select "I/Q Analog > I/Q Analog Settings > General".
3. Select "RF Envelope > On".
(x) = VccPow0 is:
Pow
Figure 2-3: RF Envelope Settings (Example)
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R&S®SMBVB-K540, R&S®SMBVB-K541
1 = Termination and input impedance of the circuit board
2 = Voltage level measured at the circuit board
3 = Signal characteristics of the DC Modulator
4 = Signal characteristics at the inputs of the PA (see the documentation of the PA, for example its data
sheet)
The remote commands required to define these settings are described in Chap-
ter 6.2, "SOURce:IQ:OUTPut:ENVelope commands", on page 80.
Settings:
State..............................................................................................................................22
Set to Default................................................................................................................ 22
Save/Recall...................................................................................................................23
RF Envelope................................................................................................................. 23
Envelope Voltage Adaptation........................................................................................23
eTrak® Interface Type....................................................................................................24
I/Q Output Type.............................................................................................................24
Envelope Voltage Reference.........................................................................................24
V
Min/Max...................................................................................................................24
out
Bias............................................................................................................................... 25
DC Modulator characteristics........................................................................................25
└ EMF................................................................................................................ 25
└ Rin................................................................................................................... 26
└ Termination..................................................................................................... 26
└ Bipolar Input....................................................................................................26
└ VppMax............................................................................................................ 27
└ Gain................................................................................................................ 27
└ VccOffset..........................................................................................................27
PA characteristics..........................................................................................................28
└ VccMin/Max......................................................................................................28
└ Power Offset................................................................................................... 29
└ PEPinMin/Max................................................................................................. 29
Generation of envelope tracking signals
General RF envelope settings
State
Enables/disables the analog I/Q output.
Note: By default, these output connectors are deactivated.
Note: Interdependencies
Some functions cannot be activated simultaneously. They deactivate each other.
Remote command:
[:SOURce<hw>]:IQ:OUTPut:ANALog:STATe on page 78
Set to Default
Calls the default settings. The values of the main parameters are listed in the following
table.
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R&S®SMBVB-K540, R&S®SMBVB-K541
Parameter Value
"State" Not affected by the "Set to Default"
"RF Envelope" Off
Generation of envelope tracking signals
General RF envelope settings
"I/Q Output Type"
"I/Q Level Vp (EMF)" 1 V
"Bias (EMF)" 0 mV
Depends on "System Configuration > External RF and I/Q > Preset behavior:
Keep connections to external instruments":
●
"Off": Single Ended
●
"On": Not affected by the "Set to Default"
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:PRESet on page 78
Save/Recall
Accesses the "Save/Recall" dialog, that is the standard instrument function for saving
and recalling the complete dialog-related settings in a file. The provided navigation
possibilities in the dialog are self-explanatory.
The settings are saved in a file with predefined extension. You can define the filename
and the directory, in that you want to save the file.
See also, chapter "File and Data Management" in the R&S SMBV100B user manual.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:SETTing:CATalog? on page 79
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:SETTing:STORe on page 79
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:SETTing:LOAD on page 79
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:SETTing:DELete on page 79
RF Envelope
Enables the output of a control signal that follows the RF envelope. This control signal
is provided for power amplifiers envelope tracking testing. The signal is output at the I
out and I Bar out connectors.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:STATe on page 83
Envelope Voltage Adaptation
Defines the way you configure the voltage of the envelope tracking generator (see
Chapter 2.2.1, "Envelope voltage adaptation modes", on page 11).
"Auto Normalized"
Generation based on the physical characteristics of the power amplifier; the power values are normalized based on the selected PEPin
Max value.
This mode enables you to use the complete range of a selected
detroughing function.
See also Shaping settings and compare the values on the X axis on
the graphical display.
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Generation of envelope tracking signals
General RF envelope settings
"Auto Power"
Generation based on the physical characteristics of the power amplifier, where the input power of the PA "PEPin" is defined with its min
and max values.
"Manual"
Generation, in that the operating range of the amplifier is defined
based on a pre-gain and a post-gain range.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:ADAPtion on page 83
eTrak® Interface Type
Selects one of the predefined interface types or allows user-defined settings.
See Chapter 2.2.2, "Signal parameters for testing according to the eTrak® specifica-
tion", on page 12.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:ETRak on page 84
I/Q Output Type
Selects the type of output signal.
The provided parameters in the "I/Q Analog Outputs" dialog depend on the selected
output mode.
●
"Single-Ended"
If "RF Envelope > Off"
Single-ended output at the I/Q connectors.
●
If "RF Envelope > On"
The envelope signal E is output at the I connectors.
You can define a bias between the output signal and ground.
"Differential"
Option: R&S SMBVB-K17
●
If "RF Envelope > Off"
The analog I/Q signal components are output at the I/Q and I/Q
Bar connectors.
●
If "RF Envelope > On"
The inverted envelope signal Ē is output at the I Bar connectors.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:TYPE on page 80
Envelope Voltage Reference
Defines whether the envelope voltage V
is set directly or it is estimated from the
out
selected supply voltage Vcc.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VREF on page 84
V
Min/Max
out
Displays the minimum and maximum values of the peak-to-peak voltage V
on the interface between the circuit board and the DC modulator.
For "Envelope Voltage Reference" , sets the value of this parameter.
voltage
out
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Generation of envelope tracking signals
General RF envelope settings
To measure the V
●
Use a suitable probe, i.e. use a differential probe if a "Wire to Wire" termination is
voltage:
out
used and a single ended probe otherwise
●
Measure at the circuit board after the termination impedance Rin.
Estimated "V
Min/Max" values are calculated based on the selected supply voltage
out
VccMin/Max, enabled Gain and VccOffset in the DC modulator.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VOUT:MIN on page 85
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VOUT:MAX on page 85
Bias
Sets a DC voltage, superimposed upon the envelope signal E and the inverted envelope signal E Bar.
Use this parameter to define the operating point of a DUT.
"I/Q Output Type" Termination "Bias" defines
"Single Ended" - The bias between the envelope signal E and ground
"Differential" "To Ground" Superimposed DC voltage, where "Bias" is related to
the selected Rin.
See also Table 2-4
"Wire To Wire" Superimposed DC voltage, where "Bias" is related to
high impedance (1 MΩ).
Table 2-4: Effect of enabled bias
Effect of a positive bias Effect of a negative bias
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:BIAS on page 85
DC Modulator characteristics
Refer to the product documentation of the external DC modulator for information on its
characteristics.
The following settings are required:
EMF ← DC Modulator characteristics
Activates EMF, which defines whether the EMF or the voltage value is displayed.
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R&S®SMBVB-K540, R&S®SMBVB-K541
An EMF-based calculation assumes an open-end circuit. Disable this parameter for
testing in more realistic conditions, where you define the input impedance of the used
external DC modulator Rin. The R&S SMBV100B then calculates the envelope output
voltage V
Min/Max based on it.
out
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:EMF[:STATe] on page 86
Rin ← DC Modulator characteristics
If "EMF > Off", sets the input impedance Rin of the external DC modulator.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:RIN on page 86
Termination ← DC Modulator characteristics
If "I/Q Output Type > Differential" and "EMF > Off", defines the way the inputs of the
DC modulator are terminated.
The termination influences the way an enabled Bias is applied.
"To Ground" "Wire to Wire"
Generation of envelope tracking signals
General RF envelope settings
*) Bias = 0 and VccOffset = 0 *) Bias = 0 and VccOffset = 0
Both inputs of the DC modulator are terminated to
ground.
This termination is also referred as a common mode
voltage.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:TERMination on page 87
Bipolar Input ← DC Modulator characteristics
If "I/Q Output Type> Differential", enables the instrument to generate a bipolar signal.
The envelope signal E swings above and below the inverted envelope signal E Bar; the
R&S SMBV100B calculates and applies a suitable envelope VccOffset automatically.
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R&S®SMBVB-K540, R&S®SMBVB-K541
Figure 2-4: Effect of a "Bipolar Input > On"
This parameter influences the lower limit of the supply voltage Vcc.
The generated signal is conformed with the MIPI®Alliance specification "Specification
for Analog Reference Interface for Envelope Tracking".
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:BINPut on page 87
Generation of envelope tracking signals
General RF envelope settings
VppMax ← DC Modulator characteristics
Sets the maximum value of the peak-to-peak driving voltage Vpp of the external DC
modulator.
The Vpp limits:
●
The value range of the supply voltage VccMin/Max
Vpp ≥ VCCMax
●
In "I/Q Output Type > Differential", the voltage of the generated envelope signal
V
Min/Max as follows:
out
Vpp ≥ V
Max[E] - V
out
Max[E Bar], where [E] and [E Bar] refer to the envelope sig-
out
nal and the inverted envelope signal.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VPP[:MAX] on page 86
Gain ← DC Modulator characteristics
Sets the gain of the external DC modulator.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:GAIN on page 87
VccOffset ← DC Modulator characteristics
Applies a voltage offset on the supply voltage VccMin/Max, i.e. compensates a possible
offset from the external DC modulator. Reduces the envelope output voltage
V
Min/Max by this value to maintain the supply voltage Vcc in the defined value range.
out
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R&S®SMBVB-K540, R&S®SMBVB-K541
Figure 2-5: Effect of a Vcc offset
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VCC:OFFSet on page 87
Generation of envelope tracking signals
General RF envelope settings
PA characteristics
Refer to the product documentation of the power amplifier (PA) for information on its
characteristics.
The following settings are required:
VccMin/Max ← PA characteristics
Displays the minimum and maximum values of the supply voltage Vcc, as required by
the power amplifier (PA).
For "Envelope Voltage Reference > Vcc", sets the minimum and maximum values of
the supply voltage Vcc.
The value range of the supply voltage Vcc is determined by the allowed peak-to-peak
driving voltage Vpp of the external DC modulator and the enabled VccOffset.
VccMax ≤ VppMax
The Vcc is calculated as follows:
Vcc = Vout * Gain + Vcc Offset
Example:
Envelope Voltage Reference = V
cc
VccOffset = 0 mV
VccMax = 1 V = 0 dBV
Gain = 3 dB
VccMax [dBV] - Gain [dB] = V
V
Max = 0 dBV - 3 dB = -3 dBV = 0.708 V
out
Max or
out
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R&S®SMBVB-K540, R&S®SMBVB-K541
"Bipolar Input" Value range "VccMin"
"State > On" VccMin = - 0.5*VppMax
"State > Off" VccMin = 0 to VccMax
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VCC:MIN on page 88
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:VCC:MAX on page 88
Power Offset ← PA characteristics
Indicates an enabled power offset, for example to compensate power attenuation
because of cable lengths.
The displayed value is applied as level offset to the generated RF signal and considers
the following settings:
●
"RF > RF Level > Level > Offset"
●
"RF > RF Level > UCOR"
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:POWer:OFFSet?
on page 90
Generation of envelope tracking signals
Envelope settings
Note: Implemented as a VccOffset, see Effect of a "Bipolar
Input > On".
PEPinMin/Max ← PA characteristics
Sets the minimum and maximum values of the input power PEPin, as required by the
power amplifier (PA).
The "PEPinMin/Max" parameters define the linear range of the PA. Refer to the product
documentation of the PA for information on the characteristics of the required input sig-
nal.
The value range corresponds to the value range of output level.
Remote command:
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:PIN:MIN on page 89
[:SOURce<hw>]:IQ:OUTPut[:ANALog]:ENVelope:PIN:MAX on page 90
2.4 Envelope settings
Access:
1. Enable the generation of envelope tracking signal.
See Chapter 2.3, "General RF envelope settings", on page 21.
2. Select "I/Q Analog Settings > Envelope Settings".
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R&S®SMBVB-K540, R&S®SMBVB-K541
1 = Enabled Digital Predistortion
2 =
3a, 3b = (for "Envelope Voltage Adaptation > Manual") Pre-Gain/Post-Gain
4 = Shaping state and shaping function; gray background color = deactivated shaping
5 = Enabled Envelope to RF Delay
6 = Indicates the output connectors, depending on the I/Q Output Type
Envelope detector, √[I(t)2+Q(t)2]; indication changes, depending on the Envelope Voltage
Adaptation
Generation of envelope tracking signals
Envelope settings
The dialog displays an interactive overview diagram of the ET processing chain.
The diagram displays information on shaping state, incl. current shaping method
and setting, like gains or delay.
Tip: Hotspots for quick access. The displayed blocks are hotspots. Select one of
them to access the related function.
The remote commands required to define these settings are described in Chapter 6.2,
"SOURce:IQ:OUTPut:ENVelope commands", on page 80.
Settings:
Envelope to RF Delay................................................................................................... 30
Calculate Envelope from Predistorted Signal................................................................31
Envelope to RF Delay
Sets the time delay of the generated envelope signal relative to the corresponding RF
signal. A positive value means that the envelope signal delays relative to the RF signal
and vice versa.
30User Manual 1178.8165.02 ─ 07
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