Operating Manual
EMI Test Receiver
R&S
1300.5001K03
1300.5001K13
ESL3
R&SESL6
1300.5001K06
1300.5001K16
Test and Measurement
1300.5053.62-03
Dear Customer,
Throughout this manual, the EMI Test Receiver R&S
®
is a registered trademark of Rohde & Schwarz GmbH & Co. KG
R&S
®
ESL is abbreviated as R&S ESL.
Trade names are trademarks of the owners
1300.5053.62-03
Kundeninformation zur Batterieverordnung
(BattV)
Dieses Gerät enthält eine schadstoffhaltige Batterie.
Diese darf nicht mit dem Hausmüll entsorgt werden.
Nach Ende der Lebensdauer darf die Entsorgung nur
über eine Rohde&Schwarz-Kundendienststelle oder eine
geeignete Sammelstelle erfolgen.
Safety Regulations for Batteries
(according to BattV)
This equipment houses a battery containing harmful
substances that must not be disposed of as normal
household waste.
After its useful life, the battery may only be disposed of
at a Rohde & Schwarz service center or at a suitable
depot.
Normas de Seguridad para Baterías
(Según BattV)
Este equipo lleva una batería que contiene sustancias
perjudiciales, que no se debe desechar en los
contenedores de basura domésticos.
Después de la vida útil, la batería sólo se podrá eliminar
en un centro de servicio de Rohde & Schwarz o en un
depósito apropiado.
Consignes de sécurité pour batteries
(selon BattV)
Cet appareil est équipé d'une pile comprenant des
substances nocives. Ne jamais la jeter dans une
poubelle pour ordures ménagéres.
Une pile usagée doit uniquement être éliminée par un
centre de service client de Rohde & Schwarz ou peut
être collectée pour être traitée spécialement comme
déchets dangereux.
1171.0300.51 D/E/ESP/F-1
Customer Information Regarding Product Disposal
The German Electrical and Electronic Equipment (ElektroG) Act is an implementation of
the following EC directives:
2002/96/EC on waste electrical and electronic equipment (WEEE) and
•
•
2002/95/EC on the restriction of the use of certain hazardous substances in
e
lectrical and electronic equipment (RoHS).
Product labeling in accordance with EN 50419
Once the lifetime of a product has ended, this product must not be disposed of
in the standard domestic refuse. Even disposal via the municipal collection
points for waste electrical and electronic equipment is not permitted.
Rohde & Schwarz GmbH & Co. KG has developed a disposal concept for the
environmental-friendly
as
obligation
in accordance with the ElektroG Act.
Please contact your local service representative to dispose of the product.
a producer to take back and dispose of electrical and electronic waste
disposal or recycling of waste material and fully assumes its
1171.0200.52-01.01
EC Certificate of Conformity
Certificate No.: 2008-43
This is to certify that:
Equipment type Stock No. Designation
ESL3 1300.5001.03/.13 EMI Test Receiver
ESL6 1300.5001.06/.16
FSL-B4 1300.6008.02 OCXO Reference Frequency
FSL-B5 1300.6108.02 Additional Interfaces
FSL-B8 1300.5701.02 Gated Sweep Function
FSL-B10 1300.6208.02 GPIB Interface
FSL-B22 1300.5953.02 RF Amplifier
FSL-B30 1300.6308.02 DC Power Supply
FSL-B31 1300.6408.02 NIMH Battery Pack
FSL-Z4 1300.5430.02 Additional Charger Unit
complies with the provisions of the Directive of the Council of the European Union on the
approximation of the laws of the Member States
- relating to electrical equipment for use within defined voltage limits
(2006/95/EC)
- relating to electromagnetic compatibility
(2004/108/EC)
Conformity is proven by compliance with the following standards:
EN 61010-1 : 2001
EN 61326 : 1997 + A1 : 1998 + A2 : 2001 + A3 : 2003
EN 55011 : 1998 + A1 : 1999 + A2 : 2002, Klasse B
EN 61000-3-2 : 2000 + A2 : 2005
EN 61000-3-3 : 1995 + A1 : 2001
For the assessment of electromagnetic compatibility, the limits of radio interference for Class B
equipment as well as the immunity to interference for operation in industry have been used as a basis.
Affixing the EC conformity mark as from 2008
ROHDE & SCHWARZ GmbH & Co. KG
Mühldorfstr. 15, D-81671 München
Munich, 2008-06-18 Central Quality Management MF-QZ / Radde
1300.5001.01 CE E-2
R&S ESL Documentation Overview
Documentation Overview
The user documentation for the R&S ESL is divided as follows:
• Quick Start Guide
• Online Help
• Operating Manual
• Internet Site
• Service Manual
• Release Notes
Quick Start Guide
This manual is delivered with the instrument in printed form and in PDF format on the CD. It provides the
information needed to set up and start working with the instrument. Basic operations and basic measurements
are described. Also a brief introduction to remote control is given. The manual includes general information
(e.g. Safety Instructions) and the following chapters:
Chapter 1 Front and Rear Panel
Chapter 2 Putting into Operation
Chapter 3 Firmware Update and Installation of Firmware Options
Chapter 4 Basic Operations
Chapter 5 Basic Measurement Examples
Chapter 6 Brief Introduction to Remote Control
Appendix A Printer Interface
Appendix B LAN Interface
Online Help
The Online Help is part of the firmware. It provides a quick access to the description of the instrument functions
and the remote control commands. For information on other topics refer to the Quick Start Guide, Operating
Manual and Service Manual provided in PDF format on CD or in the Internet. For detailed information on how
to use the Online Help, refer to the chapter "Basic Operations" in the Quick Start Guide.
Operating Manual
This manual is a supplement to the Quick Start Guide and is available in PDF format on the CD delivered with
the instrument. To retain the familiar structure that applies to all operating manuals of Rohde&Schwarz Test &
Measurement instruments, the chapters 1 and 3 exist, but only in form of references to the corresponding
Quick Start Guide chapters.
In this manual, all instrument functions are described in detail. For additional information on default settings
and parameters, refer to the data sheets. The set of measurement examples in the Quick Start Guide is
expanded by more advanced measurement examples. In addition to the brief introduction to remote control in
the Quick Start Guide, a description of the commands and programming examples is given. Information on
maintenance, instrument interfaces and error messages is also provided.
The manual includes the following chapters:
Chapter 1 Putting into Operation, see Quick Start Guide chapters 1 and 2
Chapter 2 Advanced Measurement Examples
1300.5053.12 0.1 E-2
Documentation Overview R&S ESL
Chapter 3 Manual Operation, see Quick Start Guide chapter 4
Chapter 4 Instrument Functions
Chapter 5 Remote Control - Basics
Chapter 6 Remote Control - Commands
Chapter 7 Remote Control - Programming Examples
Chapter 8 Maintenance
Chapter 9 Error Messages
This manual is delivered with the instrument on CD only. The printed manual can be ordered from Rohde &
Schwarz GmbH & Co. KG.
Internet Site
The Internet site at: R&S ESL EMI Test Receiver provides the most up to date information on the R&S ESL.
The current operating manual at a time is available as printable PDF file in the download area. Also provided
for download are firmware updates including the associated release notes, instrument drivers, current data
sheets and application notes.
Service Manual
This manual is available in PDF format on the CD delivered with the instrument. It informs on how to check
compliance with rated specifications, on instrument function, repair, troubleshooting and fault elimination. It
contains all information required for repairing the R&S ESL by the replacement of modules. The manual
includes the following chapters:
Chapter 1 Performance Test
Chapter 2 Adjustment
Chapter 3 Repair
Chapter 4 Software Update / Installing Options
Chapter 5 Documents
Release Notes
The release notes describe the installation of the firmware, new and modified functions, eliminated problems,
and last minute changes to the documentation. The corresponding firmware version is indicated on the title
page of the release notes. The current release notes are provided in the Internet.
1300.5053.12 0.2 E-2
R&S ESL Conventions Used in the Documentation
Conventions Used in the Documentation
To visualize important information quickly and to recognize information types faster, a few conventions has
been introduced. The following character formats are used to emphasize words:
Bold All names of graphical user interface elements as
dialog boxes, softkeys, lists, options, buttons etc.
All names of user interface elements on the front
and rear panel as keys, connectors etc.
Courier All remote commands (apart from headings, see
below)
Capital letters All key names (front panel or keyboard)
The description of a softkey (Operating Manual and Online Help) always starts with the softkey name, and is
followed by explaining text and one or more remote control commands framed by two lines. Each remote
command is placed in a single line.
The description of remote control commands (Operating Manual and Online Help) always starts with the
command itself, and is followed by explaining text including an example, the characteristics and the mode
(standard or only with certain options) framed by two grey lines. The remote commands consist of
abbreviations to accelerate the procedure. All parts of the command that have to be entered are in capital
letters, the rest is added in small letters to complete the words and transport their meaning.
1300.5053.12 0.3 E-2
R&S ESL Putting into Operation
1 Putting into Operation
For details refer to the Quick Start Guide chapters 1, "Front and Rear Panel", and 2, "Preparing for
Use".
1300.5053.12 1.1 E-2
R&S ESL Advanced Measurement Examples
Contents of Chapter 2
2 Advanced Measurement Examples............................................................. 2.1
Test Setup .........................................................................................................................................2.2
Measurement of Harmonics ............................................................................................................2.2
High–Sensitivity Harmonics Measurements ...............................................................................2.4
Measuring the Spectra of Complex Signals ..................................................................................2.6
Separating Signals by Selecting an Appropriate Resolution Bandwidth ....................................2.6
Intermodulation Measurements ..................................................................................................2.7
Measurement example – Measuring the R&S ESL's intrinsic intermodulation...............2.9
Measuring Signals in the Vicinity of Noise ..................................................................................2.13
Measurement example – Measuring level at low S/N ratios.........................................2.14
Noise Measurements .....................................................................................................................2.17
Measuring Noise Power Density...............................................................................................2.17
Measurement example – Measuring the intrinsic noise power density of the R&S ESL at
1 GHz and calculating the R&S ESL's noise figure ......................................................2.17
Measurement of Noise Power within a Transmission Channel ................................................2.19
Measurement example – Measuring the intrinsic noise of the R&S ESL at 1 GHz in a
1.23 MHz channel bandwidth with the channel power function....................................2.20
Measuring Phase Noise............................................................................................................2.24
Measurement example – Measuring the phase noise of a signal generator at a carrier
offset of 10 kHz .............................................................................................................2.24
Measurements on Modulated Signals ..........................................................................................2.25
Measuring Channel Power and Adjacent Channel Power .......................................................2.25
Measurement example 1 – ACPR measurement on an CDMA 2000 signal ................2.26
Measurement example 2 – Measuring adjacent channel power of a W–CDMA uplink
signal.............................................................................................................................2.32
Amplitude Distribution Measurements......................................................................................2.36
Measurement example – Measuring the APD and CCDF of white noise generated by
the R&S ESL .................................................................................................................2.36
Noise Figure Measurements Option (K30)...................................................................................2.39
Direct Measurements................................................................................................................2.39
Basic Measurement Example .......................................................................................2.39
DUTs with very Large Gain ...........................................................................................2.41
Frequency–Converting Measurements ....................................................................................2.42
Fixed LO Measurements...............................................................................................2.42
Image–Frequency Rejection (SSB, DSB).....................................................................2.42
1300.5053.12 I-2.1 E-2
R&S ESL Advanced Measurement Examples
2 Advanced Measurement Examples
This chapter explains how to operate the R&S ESL using typical measurements as examples.
Additional background information on the settings is given. Examples of more basic character are
provided in the Quick Start Guide, chapter 5, as an introduction. The following topics are included in the
Quick Start Guide:
• Performing a Level and Frequency Meaurement
• Measuring a Sinusoidal Signal
Measuring the Level and Frequency Using Markers
Measuring the Signal Frequency Using the Frequency Counter
• Measuring Harmonics of Sinusoidal Signals
Measuring the Suppression of the First and Second Harmonic of an Input Signal
• Measuring Signal Spectra with Multiple Signals
Separating Signals by Selecting the Resolution Bandwidth
Measuring the Modulation Depth of an AM–Modulated Carrier (Span > 0)
Measuring of AM–Modulated Signals
• Measurements with Zero Span
Measuring the Power Characteristic of Burst Signals
Measuring the Signal–to–Noise Ratio of Burst Signals
Measurement of FM–Modulated Signals
• Storing and Loading Instrument Settings
Storing an Instrument Configuration (without Traces)
Storing Traces
Loading an Instrument Configuration (with Traces)
Configuring Automatic Loading
1300.5053.12 2.1 E-2
Test Setup R&S ESL
Test Setup
All of the following examples are based on the standard settings of the R&S ESL. These are set with
the PRESET key. A complete listing of the standard settings can be found in chapter "Instrument
Functions", section "Initializing the Configuration – PRESET Key".
In the following examples, a signal generator is used as a signal source. The RF output of the signal
generator is connected to the RF input of R&S ESL.
If a 65 MHz signal is required for the test setup, as an alternative to the signal generator, the internal 65
MHz reference generator can be used:
1. Switch on the internal reference generator.
Press the SETUP key.
Press the Service softkey.
Press the Input RF/Cal/TG softkey, until Cal is highlighted.
The internal 65 MHz reference generator is now on. The R&S ESL's RF input is switched off.
2. Switch on the RF input again for normal operation of the R&S ESL. Two ways are possible:
Press the PRESET key
Press the SETUP key.
Press the Service softkey.
Press the Input RF/Cal/TG softkey, until RF is highlighted.
The internal signal path of the R&S ESL is switched back to the RF input in order to resume
normal operation.
Measurement of Harmonics
Measuring the harmonics of a signal is a frequent problem which can be solved best by means of a
spectrum analyzer. In general, every signal contains harmonics which are larger than others.
Harmonics are particularly critical regarding high–power transmitters such as transceivers because
large harmonics can interfere with other radio services.
Harmonics are generated by nonlinear characteristics. They can often be reduced by lowpass filters.
Since the spectrum analyzer has a nonlinear characteristic, e.g. in its first mixer, measures must be
taken to ensure that harmonics produced in the spectrum analyzer do not cause spurious results. If
necessary, the fundamental wave must be selectively attenuated with respect to the other harmonics
with a highpass filter.
When harmonics are being measured, the obtainable dynamic range depends on the second harmonic
intercept of the spectrum analyzer. The second harmonic intercept is the virtual input level at the RF
input mixer at which the level of the 2nd harmonic becomes equal to the level of the fundamental wave.
In practice, however, applying a level of this magnitude would damage the mixer. Nevertheless the
available dynamic range for measuring the harmonic distance of a DUT can be calculated relatively
easily using the second harmonic intercept.
nd
As shown in Fig. 2-1, the level of the 2
is reduced by 10 dB.
harmonic drops by 20 dB if the level of the fundamental wave
1300.5053.12 2.2 E-2
R&S ESL Measurement of Harmonics
2
Level display
/ dBm
0
5
40
30
2nd harmonic
ntercept point /
i
d
Bm
10
0
-10
-20
-30
-40
-50
-60
-70
-80
1st harmonic
1
1
-30
-20 0-10 10 20 30 40 50
2nd harmonic
2
1
RF level
/ dBm
Fig. 2-1 Extrapolation of the 1st and 2nd harmonics to the 2nd harmonic intercept at 40 dBm
The following formula for the obtainable harmonic distortion d
in dB is derived from the straight–line
2
equations and the given intercept point:
= S.H.I – PI(1)
d
2
d
2
= harmonic distortion
PI= mixer level/dBm
S.H.I. = second harmonic intercept
Note: The mixer level is the RF level applied to the RF input minus the set RF attenuation.
The formula for the internally generated level P1at the 2nd harmonic in dBm is:
P
= 2PI– S.H.I. (2)
1
The lower measurement limit for the harmonic is the noise floor of the spectrum analyzer. The harmonic
of the measured DUT should – if sufficiently averaged by means of a video filter – be at least 4 dB
above the noise floor so that the measurement error due to the input noise is less than 1 dB.
The following rules for measuring high harmonic ratios can be derived:
Select the smallest possible IF bandwidth for a minimal noise floor.
Select an RF attenuation which is high enough to just measure the harmonic ratio.
The maximum harmonic distortion is obtained if the level of the harmonic equals the intrinsic noise level
of the receiver. The level applied to the mixer, according to (2), is:
2/ IPdBmP
noise
P
=
I
+
(3)
At a resolution bandwidth of 10 Hz (noise level –143 dBm, S.H.I. = 40 dBm), the optimum mixer level is
– 51.5 dBm. According to (1) a maximum measurable harmonic distortion of 91.5 dB minus a minimum
S/N ratio of 4 dB is obtained.
1300.5053.12 2.3 E-2
Measurement of Harmonics R&S ESL
Note: If the harmonic emerges from noise sufficiently (approx. >15 dB), it is easy to check (by
changing the RF attenuation) whether the harmonics originate from the DUT or are generated
internally by the spectrum analyzer. If a harmonic originates from the DUT, its level remains
constant if the RF attenuation is increased by 10 dB. Only the displayed noise is increased by
10 dB due to the additional attenuation. If the harmonic is exclusively generated by the
spectrum analyzer, the level of the harmonic is reduced by 20 dB or is lost in noise. If both – the
DUT and the spectrum analyzer – contribute to the harmonic, the reduction in the harmonic
level is correspondingly smaller.
High–Sensitivity Harmonics Measurements
If harmonics have very small levels, the resolution bandwidth required to measure them must be
reduced considerably. The sweep time is, therefore, also increased considerably. In this case, the
measurement of individual harmonics is carried out with the R&S ESL set to a small span. Only the
frequency range around the harmonics will then be measured with a small resolution bandwidth.
Signal generator settings (e.g. R&S SMU):
Frequency: 128 MHz
Level: – 25 dBm
Procedure:
1. Set the R&S ESL to its default state.
Press the PRESET key.
The R&S ESL is set to its default state.
2. Set the center frequency to 128 MHz and the span to 100 kHz.
Press the FREQ key.
The frequency menu is displayed.
In the dialog box, enter 128 using the numeric keypad and confirm with the MHz key.
Press the SPAN key.
In the dialog box, enter 100 using the numeric keypad and confirm with the kHz key.
The R&S ESL displays the reference signal with a span of 100 kHz and resolution bandwidth of
3 kHz.
3. Switching on the marker.
Press the MKR key.
The marker is positioned on the trace maximum.
4. Set the measured signal frequency and the measured level as reference values
Press the Phase Noise/Ref Fixed softkey.
The position of the marker becomes the reference point. The reference point level is indicated
by a horizontal line, the reference point frequency with a vertical line. At the same time, the
delta marker 2 is switched on.
Press the Ref Fixed softkey.
1300.5053.12 2.4 E-2
R&S ESL Measurement of Harmonics
The mode changes from phase noise measurement to reference fixed, the marker readout
hanges from dB/Hz to dB.
c
Fig. 2-2 Fundamental wave and the frequency and level reference point
5. Make the step size for the center frequency equal to the signal frequency
Press the FREQ key.
The frequency menu is displayed.
Press the CF–Stepsize softkey and press the = Marker softkey in the submenu.
The step size for the center frequency is now equal to the marker frequency.
6. Set the center frequency to the 2
nd
harmonic of the signal
Press the FREQ key.
The frequency menu is displayed.
Press the UPARROW key once.
nd
The center frequency is set to the 2
7. Place the delta marker on the 2
nd
harmonic.
harmonic.
Press the MKR–> key.
Press the Peak softkey.
nd
The delta marker moves to the maximum of the 2
harmonic. The displayed level result is
relative to the reference point level (= fundamental wave level).
1300.5053.12 2.5 E-2
Measuring the Spectra of Complex Signals R&S ESL
Fig. 2-3 Measuring the level difference between the fundamental wave (= reference point
level) and the 2
The other harmonics are measured with steps 5 and 6, the center frequency being incremented or
decremented in steps of 128 MHz using the UPARROW or DNARROW key.
nd
harmonic
Measuring the Spectra of Complex Signals
Separating Signals by Selecting an Appropriate Resolution Bandwidth
A basic feature of a spectrum analyzer is being able to separate the spectral components of a mixture
of signals. The resolution at which the individual components can be separated is determined by the
resolution bandwidth. Selecting a resolution bandwidth that is too large may make it impossible to
distinguish between spectral components, i.e. they are displayed as a single component.
An RF sinusoidal signal is displayed by means of the passband characteristic of the resolution filter
(RBW) that has been set. Its specified bandwidth is the 3 dB bandwidth of the filter.
Two signals with the same amplitude can be resolved if the resolution bandwidth is smaller than or
equal to the frequency spacing of the signal. If the resolution bandwidth is equal to the frequency
spacing, the spectrum display screen shows a level drop of 3 dB precisely in the center of the two
signals. Decreasing the resolution bandwidth makes the level drop larger, which thus makes the
individual signals clearer.
If there are large level differences between signals, the resolution is determined by selectivity as well as
by the resolution bandwidth that has been selected. The measure of selectivity used for spectrum
analyzers is the ratio of the 60 dB bandwidth to the 3 dB bandwidth (= shape factor).
For the R&S ESL, the shape factor for bandwidths is < 5, i.e. the 60 dB bandwidth of the 30 kHz filter is
< 150 kHz.
1300.5053.12 2.6 E-2
R&S ESL Measuring the Spectra of Complex Signals
The higher spectral resolution with smaller bandwidths is won by longer sweep times for the same
pan. The sweep time has to allow the resolution filters to settle during a sweep at all signal levels and
s
frequencies to be displayed. It is given by the following formula.
Span/RBWkSWT •= (4)
SWT = max. sweep time for correct measurement
k = factor depending on type of resolution filter
= 1 for digital IF filters
Span = frequency display range
RBW = resolution bandwidth
2
If the resolution bandwidth is reduced by a factor of 3, the sweep time is increased by a factor of 9.
Note: The impact of the video bandwidth on the sweep time is not taken into account in (4). For the
formula to be applied, the video bandwidth must be 3 x the resolution bandwidth.
FFT filters can be used for resolution bandwidths up to 30 kHz. Like digital filters, they have a shape
factor of less than 5 up to 30 kHz. For FFT filters, however, the sweep time is given by the following
formula:
SWT = k
span/RBW (5)
If the resolution bandwidth is reduced by a factor of 3, the sweep time is increased by a factor of 3 only.
Intermodulation Measurements
If several signals are applied to a transmission two–port device with nonlinear characteristic,
intermodulation products appear at its output by the sums and differences of the signals. The nonlinear
characteristic produces harmonics of the useful signals which intermodulate at the characteristic. The
intermodulation products of lower order have a special effect since their level is largest and they are
near the useful signals. The intermodulation product of third order causes the highest interference. It is
the intermodulation product generated from one of the useful signals and the 2nd harmonic of the
second useful signal in case of two–tone modulation.
The frequencies of the intermodulation products are above and below the useful signals. Fig. 2-4 shows
intermodulation products P
and PI2 generated by the two useful signals PU1 and PU2.
I1
Fig. 2-4 Intermodulation products PU1 and PU2
1300.5053.12 2.7 E-2
Measuring the Spectra of Complex Signals R&S ESL
2
60
2
The intermodulation product at f
ignal P
s
P
.
2
U
the intermodulation product at f
,
1
U
= 2 x fu1 – fu2 (6)
f
i1
= 2 x fu2 – fu1 (7)
f
i2
is generated by mixing the 2nd harmonic of useful signal PU2 and
I2
y mixing the 2nd harmonic of useful signal P
b
1
I
nd signal
a
1
U
The level of the intermodulation products depends on the level of the useful signals. If the two useful
signals are increased by 1 dB, the level of the intermodulation products increases by 3 dB, which
means that spacing a
between intermodulation signals and useful signals are reduced by 2 dB. This is
D3
illustrated in Fig. 2-5.
Fig. 2-5 Dependence of intermodulation level on useful signal level
The useful signals at the two–port output increase proportionally with the input level as long as the two–
port is in the linear range. A level change of 1 dB at the input causes a level change of 1 dB at the
output. Beyond a certain input level, the two–port goes into compression and the output level stops
increasing. The intermodulation products of the third order increase three times as much as the useful
signals. The intercept point is the fictitious level where the two lines intersect. It cannot be measured
directly since the useful level is previously limited by the maximum two–port output power.
It can be calculated from the known line slopes and the measured spacing a
at a given level
D3
according to the following formula.
a
D
IP
rd
The 3
order intercept point (TOI), for example, is calculated for an intermodulation of 60 dB and an
input level P
IP dBm dBm3
3
3
=+
P
N
(8)
of –20 dBm according to the following formula:
U
20 10= + =( ) (9)
1300.5053.12 2.8 E-2
R&S ESL Measuring the Spectra of Complex Signals
Measurement example – Measuring the R&S ESL's intrinsic intermodulation
Test setup:
Signal
G
enerator 1
Coupler
[- 6 dB]
Signal
Generator 2
R&S ESL
Signal generator settings (e.g. R&S SMU):
Signal generator 1 –4 dBm 999.7 MHz
Signal generator 2 –4 dBm 1000.3 MHz
Level Frequency
Procedure:
1. Set the R&S ESL to its default settings.
Press the PRESET key.
The R&S ESL is in its default state.
2. Set center frequency to 1 GHz and the frequency span to 3 MHz.
Press the FREQ key and enter 1 GHz.
Press the SPAN key and enter 3 MHz.
3. Set the reference level to –10 dBm and RF attenuation to 0 dB.
Press the AMPT key and enter –10 dBm.
Press the RF Atten Manual softkey and enter 0 dB.
4. Set the resolution bandwidth to 10 kHz.
Press the BW key.
Press the Res BW Manual softkey and enter 10 kHz.
The noise is reduced, the trace is smoothed further and the intermodulation products can be
clearly seen.
Press the Video BW Manual softkey and enter 1 kHz.
rd
5. Measuring intermodulation by means of the 3
order intercept measurement function
Press the MEAS key.
Press the TOI softkey.
1300.5053.12 2.9 E-2
Measuring the Spectra of Complex Signals R&S ESL
The R&S ESL activates four markers for measuring the intermodulation distance. Two markers
re positioned on the useful signals and two on the intermodulation products. The 3
a
d
r
rder
o
intercept is calculated from the level difference between the useful signals and the
intermodulation products. It is then displayed on the screen:
Fig. 2-6 Result of intrinsic intermodulation measurement on the R&S ESL. The 3rd order
intercept (TOI) is displayed at the top right corner of the grid.
The level of a spectrum analyzer's intrinsic intermodulation products depends on the RF level of the
useful signals at the input mixer. When the RF attenuation is added, the mixer level is reduced and
the intermodulation distance is increased. With an additional RF attenuation of 10 dB, the levels of
the intermodulation products are reduced by 20 dB. The noise level is, however, increased by 10
dB.
6. Increasing RF attenuation to 10 dB to reduce intermodulation products.
Press the AMPT key.
Press the RF Atten Manual softkey and enter 10 dB.
The R&S ESL's intrinsic intermodulation products disappear below the noise floor.
1300.5053.12 2.10 E-2
R&S ESL Measuring the Spectra of Complex Signals
Fig. 2-7 If the RF attenuation is increased, the R&S ESL's intrinsic intermodulation products
disappear below the noise floor.
Calculation method:
The method used by the R&S ESL to calculate the intercept point takes the average useful signal level
in dBm and calculates the intermodulation d3in dB as a function of the average value of the levels of
P
u
the two intermodulation products. The third order intercept (TOI) is then calculated as follows:
TOI/dBm = ½ d
3
+ P
u
Intermodulation– free dynamic range
The Intermodulation – free dynamic range, i.e. the level range in which no internal intermodulation
products are generated if two–tone signals are measured, is determined by the 3
rd
order intercept point,
the phase noise and the thermal noise of the spectrum analyzer. At high signal levels, the range is
determined by intermodulation products. At low signal levels, intermodulation products disappear below
the noise floor, i.e. the noise floor and the phase noise of the spectrum analyzer determine the range.
The noise floor and the phase noise depend on the resolution bandwidth that has been selected. At the
smallest resolution bandwidth, the noise floor and phase noise are at a minimum and so the maximum
range is obtained. However, a large increase in sweep time is required for small resolution bandwidths.
It is, therefore, best to select the largest resolution bandwidth possible to obtain the range that is
required. Since phase noise decreases as the carrier–offset increases, its influence decreases with
increasing frequency offset from the useful signals.
The following diagrams illustrate the intermodulation–free dynamic range as a function of the selected
bandwidth and of the level at the input mixer (= signal level – set RF attenuation) at different useful
signal offsets.
1300.5053.12 2.11 E-2
Measuring the Spectra of Complex Signals R&S ESL
Distortion free Dynamic Range
D
y
n
r
a
n
g
e
/
d
B
-40
-50
-60
-70
-80
-90
-100
-110
-120
-60 -50 -40 -30 -20 -10
RWB = 1 kHz
RWB = 100 Hz
RWB = 10 Hz
Fig. 2-8 Intermodulation–free range of the R&S ESL as a function of level at the input mixer and the
set resolution bandwidth (useful signal offset = 1 MHz, DANL = –145 dBm /Hz, TOI = 15 dBm; typical
values at 2 GHz)
(1 MHz carrier offset
)
T.O.I.
Thermal Noise
+ Phase Noise
Mixer level /dBm
The optimum mixer level, i.e. the level at which the intermodulation distance is at its maximum, depends
on the bandwidth. At a resolution bandwidth of 10 Hz, it is approx. –35 dBm and at 1 kHz increases to
approx. –30 dBm.
Phase noise has a considerable influence on the intermodulation–free range at carrier offsets between
10 and 100 kHz (Fig. 2-9). At greater bandwidths, the influence of the phase noise is greater than it
would be with small bandwidths. The optimum mixer level at the bandwidths under consideration
becomes almost independent of bandwidth and is approx. –40 dBm.
Distortion free Dynamic Range
D
y
n
.
r
a
n
g
e
/
d
B
-40
-50
-60
-70
-80
-90
-100
-110
-120
-60 -50 -40 -30 -20 -10
RBW = 1 kHz
RBW = 100 Hz
RBW = 10 Hz
(10 to 100 kHz carrier offset
)
TOI
Thermal Noise
+ Phase Noise
Mixer level /dBm
Fig. 2-9 Intermodulation–free dynamic range of the R&S ESL as a function of level at the input
mixer and of the selected resolution bandwidth (useful signal offset = 10 to 100 kHz, DANL = –145 dBm
/Hz, TOI = 15 dBm; typical values at 2 GHz).
1300.5053.12 2.12 E-2
R&S ESL Measuring Signals in the Vicinity of Noise
Note: If the intermodulation products of a DUT with a very high dynamic range are to be measured
and the resolution bandwidth to be used is therefore very small, it is best to measure the levels
of the useful signals and those of the intermodulation products separately using a small span.
The measurement time will be reduced– in particular if the offset of the useful signals is large.
To find signals reliably when frequency span is small, it is best to synchronize the signal
sources and the R&S ESL.
Measuring Signals in the Vicinity of Noise
The minimum signal level a spectrum analyzer can measure is limited by its intrinsic noise. Small
signals can be swamped by noise and therefore cannot be measured. For signals that are just above
the intrinsic noise, the accuracy of the level measurement is influenced by the intrinsic noise of the
spectrum analyzer.
The displayed noise level of a spectrum analyzer depends on its noise figure, the selected RF
attenuation, the selected reference level, the selected resolution and video bandwidth and the detector.
The effect of the different parameters is explained in the following.
Impact of the RF attenuation setting
The sensitivity of a spectrum analyzer is directly influenced by the selected RF attenuation. The highest
sensitivity is obtained at a RF attenuation of 0 dB. The attenuation can be set in 10 dB steps up to 70
dB. Each additional 10 dB step reduces the sensitivity by 10 dB, i.e. the displayed noise is increased by
10 dB.
Impact of the resolution bandwidth
The sensitivity of a spectrum analyzer also directly depends on the selected bandwidth. The highest
sensitivity is obtained at the smallest bandwidth (for the R&S ESL: 10 Hz, for FFT filtering: 1 Hz). If the
bandwidth is increased, the reduction in sensitivity is proportional to the change in bandwidth. The
R&S ESL has bandwidth settings in 1, 3, 10 sequence. Increasing the bandwidth by a factor of 3
increases the displayed noise by approx. 5 dB (4.77 dB precisely). If the bandwidth is increased by a
factor of 10, the displayed noise increases by a factor of 10, i.e. 10 dB.
Impact of the video bandwidth
The displayed noise of a spectrum analyzer is also influenced by the selected video bandwidth. If the
video bandwidth is considerably smaller than the resolution bandwidth, noise spikes are suppressed,
i.e. the trace becomes much smoother. The level of a sinewave signal is not influenced by the video
bandwidth. A sinewave signal can therefore be freed from noise by using a video bandwidth that is
small compared with the resolution bandwidth, and thus be measured more accurately.
Impact of the detector
Noise is evaluated differently by the different detectors. The noise display is therefore influenced by the
choice of detector. Sinewave signals are weighted in the same way by all detectors, i.e. the level
display for a sinewave RF signal does not depend on the selected detector, provided that the signal–to–
noise ratio is high enough. The measurement accuracy for signals in the vicinity of intrinsic spectrum
analyzer noise is also influenced by the detector which has been selected. For details on the detectors
of the R&S ESL refer to chapter "Instrument Functions", section "Detector overview" or the Online Help.
1300.5053.12 2.13 E-2
Measuring Signals in the Vicinity of Noise R&S ESL
Measurement example – Measuring level at low S/N ratios
The example shows the different factors influencing the S/N ratio.
Signal generator settings (e.g. R&S SMU):
requency: 128 MHz
F
Level: – 80 dBm
Procedure:
1. Set the R&S ESL to its default state.
Press the PRESET key.
The R&S ESL is in its default state.
2. Set the center frequency to 128 MHz and the frequency span to 100 MHz.
Press the FREQ key and enter 128 MHz.
Press the SPAN key and enter 100 MHz.
3. Set the RF attenuation to 60 dB to attenuate the input signal or to increase the intrinsic noise.
Press the AMPT key.
Press the RF Atten Manual softkey and enter 60 dB.
The RF attenuation indicator is marked with an asterisk (*Att 60 dB) to show that it is no longer
coupled to the reference level. The high input attenuation reduces the reference signal which
can no longer be detected in noise.
Fig. 2-10 Sinewave signal with low S/N ratio. The signal is measured with the auto peak
detector and is completely hidden in the intrinsic noise of the R&S ESL.
1300.5053.12 2.14 E-2
R&S ESL Measuring Signals in the Vicinity of Noise
4. To suppress noise spikes the trace can be averaged.
Press the TRACE key.
Press the Trace Mode key.
Press the Average softkey.
The traces of consecutive sweeps are averaged. To perform averaging, the R&S ESL
automatically switches on the sample detector. The RF signal, therefore, can be more clearly
distinguished from noise.
Fig. 2-11 RF sinewave signal with low S/N ratio if the trace is averaged.
5. Instead of trace averaging, a video filter that is narrower than the resolution bandwidth can be
selected.
Press the Trace Mode key.
Press the Clear Write softkey.
Press the BW key.
Press the Video BW Manual softkey and enter 10 kHz.
The RF signal can be more clearly distinguished from noise.
1300.5053.12 2.15 E-2
Measuring Signals in the Vicinity of Noise R&S ESL
Fig. 2-12 RF sinewave signal with low S/N ratio if a smaller video bandwidth is selected.
6. By reducing the resolution bandwidth by a factor of 10, the noise is reduced by 10 dB.
Press the Res BW Manual softkey and enter 300 kHz.
The displayed noise is reduced by approx. 10 dB. The signal, therefore, emerges from noise by
about 10 dB. Compared to the previous setting, the video bandwidth has remained the same,
i.e. it has increased relative to the smaller resolution bandwidth. The averaging effect of the
video bandwidth is therefore reduced. The trace will be noisier.
Fig. 2-13 Reference signal at a smaller resolution bandwidth
1300.5053.12 2.16 E-2
R&S ESL Noise Measurements
Noise Measurements
oise measurements play an important role in spectrum analysis. Noise e.g. affects the sensitivity of
N
radio communication systems and their components.
Noise power is specified either as the total power in the transmission channel or as the power referred
to a bandwidth of 1 Hz. The sources of noise are, for example, amplifier noise or noise generated by
oscillators used for the frequency conversion of useful signals in receivers or transmitters. The noise at
the output of an amplifier is determined by its noise figure and gain.
The noise of an oscillator is determined by phase noise near the oscillator frequency and by thermal
noise of the active elements far from the oscillator frequency. Phase noise can mask weak signals near
the oscillator frequency and make them impossible to detect.
Measuring Noise Power Density
To measure noise power referred to a bandwidth of 1 Hz at a certain frequency, the R&S ESL provides
marker function. This marker function calculates the noise power density from the measured marker
level.
Measurement example – Measuring the intrinsic noise power density of the R&S ESL at 1 GHz and calculating the R&S ESL's noise figure
Test setup:
Connect no signal to the RF input; terminate RF input with 50 O.
Procedure:
1. Set the R&S ESL to its default state.
Press the PRESET key.
The R&S ESL is in its default state.
2. Set the center frequency to 1.234 GHz and the span to 1 MHz.
Press the FREQ key and enter 1.234 GHz.
Press the SPAN key and enter 1 MHz.
3. Switch on the marker and set the marker frequency to 1.234 GHz.
Press the MKR key and enter 1.234 GHz.
4. Switch on the noise marker function.
Switch on the Noise Meas softkey.
The R&S ESL displays the noise power at 1 GHz in dBm (1 Hz).
Note: Since noise is random, a sufficiently long measurement time has to be selected to obtain stable
measurement results. This can be achieved by averaging the trace or by selecting a very small
video bandwidth relative to the resolution bandwidth.
1300.5053.12 2.17 E-2
Noise Measurements R&S ESL
5. The measurement result is stabilized by averaging the trace.
Press the TRACE key.
Press the Trace Mode key.
Press the Average softkey.
The R&S ESL performs sliding averaging over 10 traces from consecutive sweeps. The
measurement result becomes more stable.
Conversion to other reference bandwidths
The result of the noise measurement can be referred to other bandwidths by simple conversion. This is
done by adding 10 log (BW) to the measurement result, BW being the new reference bandwidth.
Example
A noise power of –150 dBm (1 Hz) is to be referred to a bandwidth of 1 kHz.
= –150 + 10 * log (1000) = –150 +30 = –120 dBm (1 kHz)
P
[1kHz]
Calculation method for noise power
If the noise marker is switched on, the R&S ESL automatically activates the sample detector. The video
bandwidth is set to 1/10 of the selected resolution bandwidth (RBW).
To calculate the noise, the R&S ESL takes an average over 17 adjacent pixels (the pixel on which the
marker is positioned and 8 pixels to the left, 8 pixels to the right of the marker). The measurement result
is stabilized by video filtering and averaging over 17 pixels.
Since both video filtering and averaging over 17 trace points is performed in the log display mode, the
result would be 2.51 dB too low (difference between logarithmic noise average and noise power). The
R&S ESL, therefore, corrects the noise figure by 2.51 dB.
To standardize the measurement result to a bandwidth of 1 Hz, the result is also corrected by –10 * log
(RBW
), with RBW
noise
being the power bandwidth of the selected resolution filter (RBW).
noise
Detector selection
The noise power density is measured in the default setting with the sample detector and using
averaging. Other detectors that can be used to perform a measurement giving true results are the
average detector or the RMS detector. If the average detector is used, the linear video voltage is
averaged and displayed as a pixel. If the RMS detector is used, the squared video voltage is averaged
and displayed as a pixel. The averaging time depends on the selected sweep time (=SWT/501). An
increase in the sweep time gives a longer averaging time per pixel and thus stabilizes the measurement
result. The R&S ESL automatically corrects the measurement result of the noise marker display
depending on the selected detector (+1.05 dB for the average detector, 0 d for the RMS detector). It is
assumed that the video bandwidth is set to at least three times the resolution bandwidth. While the
average or RMS detector is being switched on, the R&S ESL sets the video bandwidth to a suitable
value.
The Pos Peak, Neg Peak, Auto Peak and Quasi Peak detectors are not suitable for measuring noise
power density.
Determining the noise figure
The noise figure of amplifiers or of the R&S ESL alone can be obtained from the noise power display.
Based on the known thermal noise power of a 50 resistor at room temperature (–174 dBm (1Hz)) and
the measured noise power P
NF = P
+ 174 – g,
noise
the noise figure (NF) is obtained as follows:
noise
where g = gain of DUT in dB
1300.5053.12 2.18 E-2
R&S ESL Noise Measurements
Correction
Example
The measured internal noise power of the R&S ESL at an attenuation of 0 dB is found to be –143
dBm/1 Hz. The noise figure of the R&S ESL is obtained as follows
NF = –143 + 174 = 31 dB
Note: If noise power is measured at the output of an amplifier, for example, the sum of the internal
noise power and the noise power at the output of the DUT is measured. The noise power of the
DUT can be obtained by subtracting the internal noise power from the total power (subtraction
of linear noise powers). By means of the following diagram, the noise level of the DUT can be
estimated from the level difference between the total and the internal noise level.
0
1
factor in dB
-
2
-
-3
-4
-5
-6
-7
-8
-9
-10
012345678910111213141516
Total powe r/intrinsic noise po wer in dB
Fig. 2-14 Correction factor for measured noise power as a function of the ratio of total power to the
intrinsic noise power of the spectrum analyzer
Measurement of Noise Power within a Transmission Channel
Noise in any bandwidth can be measured with the channel power measurement functions. Thus the
noise power in a communication channel can be determined, for example. If the noise spectrum within
the channel bandwidth is flat, the noise marker from the previous example can be used to determine the
noise power in the channel by considering the channel bandwidth. If, however, phase noise and noise
that normally increases towards the carrier is dominant in the channel to be measured, or if there are
discrete spurious signals in the channel, the channel power measurement method must be used to
obtain correct measurement results.
1300.5053.12 2.19 E-2
Noise Measurements R&S ESL
Measurement example – Measuring the intrinsic noise of the R&S ESL at 1 GHz in a
1.23 MHz channel bandwidth with the channel power function
Test setup:
Leave the RF input of the R&S ESL open–circuited or terminate it with 50 .
Procedure:
1. Set the R&S ESL to its default state.
Press the PRESET key.
The R&S ESL is in its default state.
2. Set the center frequency to 1 GHz and the span to 1 MHz.
Press the FREQ key and enter 1 GHz.
Press the SPAN key and enter 2 MHz.
3. To obtain maximum sensitivity, set RF attenuation on the R&S ESL to 0 dB.
Press the AMPT key.
Press the RF Atten Manual softkey and enter 0 dB.
4. Switch on and configure the channel power measurement.
Press the MEAS key.
Press the CP, ACP, MC–ACP softkey.
The R&S ESL activates the channel or adjacent channel power measurement according to the
currently set configuration.
Press the CP/ACP Config softkey.
The submenu for configuring the channel is displayed.
Press the Channel Settings softkey.
The submenu for channel settings is displayed.
Press the Channel Bandwidth softkey and enter 1.23 MHz.
The R&S ESL displays the 1.23 MHz channel as two vertical lines which are symmetrical to the
center frequency.
Press the Adjust Settings softkey.
The settings for the frequency span, the bandwidth (RBW and VBW) and the detector are
automatically set to the optimum values required for the measurement.
1300.5053.12 2.20 E-2
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