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Subject to change O.Gerlach 07.2009 - 1MA29_7e
Products: R&SAFQ100A, R&S
AFQ100B, R&S
SMF100A, R&S
SMR, R&S
SMJ100A, R&S
SMV,
R&SSMU, R&S
SFU, R&S
FSL, R&S
FSP, R&S
FSQ, R&S
FSU, R&S
FSV, R&S
NPR - Noise Power Ratio
Signal Generation and
Measurement
Noise Power Ratio (NPR) is an add-on tool for WinIQSIM / WinIQSIM2 to generate noise power ratiostimulus signals and measure the resulting noise power ratio of a device under test (DUT) using Rohde &
Schwarz instruments via IEEE or LAN interface.
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Contents
1 Overview ................................................................................................. 22 Software Features................................................................................... 33 Hardware and Software Requirements................................................... 4
Hardware Requirements.................................................................... 4
Software Requirements ..................................................................... 44 Connecting the Computer and Instrument .............................................. 55 Installing NPR.......................................................................................... 56 Starting the Software / Measurement...................................................... 6
Parameters ...................................................................................... 14Sampling Parameters ................................................................. 14Notch Related Parameters.......................................................... 16Phase / Magnitude Distribution................................................... 17Notch List .................................................................................... 17Calculate FFT ............................................................................. 18Connected................................................................................... 19
Menu ................................................................................................ 19Load / Save Configuration File.................................................... 19
Devices ....................................................................................... 21Optimize Crest Factor................................................................. 23Performing NPR Measurements................................................. 24Using NPR with Microwaves....................................................... 25
7 Additional Information ........................................................................... 288 Ordering information ............................................................................. 28
The following abbreviations are used in this Application Note for Rohde &Schwarz test equipment:
The IQ Modulation Generators R&SAFQ100A and R&S
AFQ100B are
referred to as AFQ.
The IQ Modulation Generator R&SAMIQ is referred to as AMIQ.
The Vector Signal Generator R&SSMU200A is referred to as SMU.
The Vector Signal Generator R&SSMBV100A is referred to as SMBV.
The Vector Signal Generator R&SSMJ100A is referred to as SMJ.
The Vector Signal Generator R&SSMV03 is referred to as SMV.
The Vector Signal Generator R&SSMIQ is referred to as SMIQ.
The Broadcast Test System R&SSFU is referred to as SFU.
The Spectrum Analyzer R&SFSL is referred to as FSL.
The Spectrum Analyzer R&SFSP is referred to as FSP.
The Spectrum Analyzer R&SFSQ is referred to as FSQ.
The Spectrum Analyzer R&SFSU is referred to as FSU. The Spectrum Analyzer R&S
FSV is referred to as FSV.
The Spectrum Analyzer R&SFSIQ is referred to as FSIQ.
The Spectrum Analyzers R&SFSEA and R&S
FSEB are referred to as
FSE.
The Microwave Generator R&SSMF100A is referred to as SMF.
The Microwave Generator R&SSMR is referred to as SMR.
The R&S logo, Rohde & Schwarz, and R&S are registered trademarks ofRohde & Schwarz GmbH & Co. KG and its subsidiaries.
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1 Overview
Noise Power Ratio (NPR) is an add-on tool for WinIQSIM / WinIQSIM2 togenerate noise power ratio stimulus signals and measure the resultingnoise power ratio of a device under test (DUT) using Rohde & Schwarz in-struments via IEEE or LAN interface. The Noise Power Ratio measurement
technique can characterize the linearity of a wide band amplifier over a cus-tom frequency range. Since NPR drastically reduces measurement timecompared to classic gain wobbling, it is particulary interesting for productionspecific applications.
2 Software Features
The software offers:
custom notch definition
generator and analyzer control load / save device configuration
automatic measurement of specified notch with adjacent channelpower (ACP) option
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3 Hardware and Software Requirements
Hardware Requirements
The software runs on a PC with:
CPU: 1 GHz or faster
RAM: 512 MBytes or more
Monitor: VGA color monitor
GPIB bus: National Instruments or Agilent GPIB controller board
and / or
LAN Standard on-board 10/100 MBit/s (FSV up to 1 GBit/s)controller or switch / hub.
It supports following instruments:
AFQ100,AMIQ: I/Q modulation generator
SMBV, SMIQ, SMJ, SMV03, SMU, SFU, SMIQ: Signal generator with I/Qinputs
FSL, FSP, FSQ, FSU, FSV, FSE, FSIQ spectrum analyzer with ACP ca-pability.
SMF, SMRmicrowave generator supported, but not mandatory.
Software Requirements
MICROSOFT WINDOWS XP/VISTA operating system.
IEEE bus driver.
TCP/IP network protocol installed.
WINIQSIM V4.4 or WINIQSIM2 V2.X (or higher) installed. This is a soft-ware tool that generates standard and custom I/Q signals e.g. forACPmeasurements. It can upload I/Q data to an AFQ / SMU I/Q modulationgenerator and control one of the SMx signal generators named above.NPR communicates with WinIQSIM / WinIQSIM2 via the TCP/IP net-work protocol. Both programs must run simultaneously to enable data
transfer. Download the latest WINIQSIM version from http://www.rohde-schwarz.com.
VISA driver by National Instruments or Agilent. See manufacturer's websitefor latest revision.
http://www.rohde-schwarz.com/http://www.rohde-schwarz.com/http://www.rohde-schwarz.com/http://www.rohde-schwarz.com/http://www.rohde-schwarz.com/8/8/2019 1MA29_7e
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4 Connecting the Computer and Instrument
Connect the computer running NPR to the instruments that are involvedwith the measurement, such as an AFQ, AMIQ IQ modulator, an SMx sig-nal generator and an FSx spectrum analyzer. Make sure that all instru-ments have different GPIB bus addresses.
REF In
REF Out
RF Input
RF Output
QI
WinIQSIM
WindowsXP/Vista
NPR
AFQ, AMIQ
SMx
IEEE bus
RS Analyzer(FSx)
DUT
TCP/IP protocol
Fig. 1 Connecting Instruments
5 Installing NPR
Make sure that WINIQSIM orWINIQSIM2 is installed on your hard disc.
Execute NPR_4.X.EXE and follow the installation notes.
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6 Starting the Software / Measurement
Execute NPR.EXE. The example setup below shows three notches generatedwith AUTOCALC NOTCHES. NPR configuration is stored in NPR.CFG at exit.
Fig. 2 Main Menu
Devices can be configured in the device menu. See DEVICES for details. Then
define a custom signal with the sampling and notch specific parameters (SAMPLE
RATE, FFTLENGTH, NOTCH COUNT, etc.). Prepare the IQ data for transmission
to WinIQSIM by pressing CALC FFT. The DATA VALID LED indicates that thedata is ready for transfer. After transferring the data to the AMIQ via WinIQSIM(see following section, step 4) press the PRESETNPRMEAS button to put the
analyzer in ACP measurement mode. Then select a NOTCH NR and press theMEASURE button to receive the signals NPRand calculated SIGNALPOWER.
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Execute WINIQSIM.EXE / WINIQSIM2.EXE and load the configuration fileNPR.IQS. / NPR.SAVRCL This affects following settings:
1. IMPORT settings for TCP/IP link.
Fig. 3 WinIQSIM Import Settings
Fig. 4 WinIQSIM2 Import Settings
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2. FILTER set to ideal low pass.
Fig. 5 WinIQSIM Filter Settings
Fig. 6 WinIQSIM2 Filter Settings
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3. Graphic Display
Fig. 7 WinIQSIM Graphic Setting
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Be sure to run NPR before WINIQSIM / WINIQSIM2 at restart to a avoida TCP/IP warning. After pressing the UPDATE button in the WinIQSimgraphics window the following display appears.
Fig. 8 WinIQSIM Graphic Display
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The WinIQSIM2 graphic display is automatically updated when a pa-rameter is changed in NPR.
Fig. 9 WinIQSIM2 Graphic Setting and Display
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4. To transfer the signal to the AMIQ press the WinIQSim menu itemAMIQ ->TRANSMISSION or the short cut key AMIQ.
Fig. 10 WinIQSIM AMIQ Transmission
Fig. 11 WinIQSIM2 SMU Transmission
5. NPR can set up the analyzer for Noise Power Ratio measurement of aspecified notch automatically (see Performing NPR Measurements). Fol-lowing analyzer parameters are affected.
DetectorRMS
Resolution bandwidth: manual < 30ms depending on sample rate.
Sweep time > 0.5s
Channel bandwidth = notch width * 0.8.
Channel spacing = notch width * 1.1
Center frequency is moved so adjacent channel fits inside notch.
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The analyzer (e.g. FSP) would show following display. The adjacentchannel fits perfectly into the second notch (cu1 - ACP upper). If thenotch's mid frequency is smaller than the generator's center fre-quency then cl1 - ACP lower channel is used.
Fig. 12 FSP ACP Display
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Parameters
Sampling Parameters
Fig. 13 Sampling Parameters
SAMPLE RATE Configures the AMIQ D/A converter sample rate. This value
affects the LINE SPACING display. A noise and notch pattern can beminimized by decreasing and expanded by increasing the sample rate.Range: 10 kHz - 105 MHz.
NOISE BW/ SAMP.RATE Configures the noise bandwidth to sample rate ra-tio. This limits the noise bandwidth to prevent upper and lower side bandaliasing effects from influencing the signal. Range: 0.01 to 1.
Noise Bandwidth
Sample Rate / 2
CenterFrequency
NBW / SRate< 1
Notch
Sample Rate / 2
Fig. 14 Noise BW / Sample Rate
NOISE BANDWIDTH (NBW) Displays the valid spectral area for customnotch insertion, which is:
NBW = Sample Rate * NBW / Srate
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FFTLENGTH the number of points in the frequency domain axis that areinversely Fourier transformed into time domain mode for download to
WinIQSIM. This value affects the LINE SPACING display.
Fig. 15 FFT Length
FFT lengths greater than 128kS are marked with an exclamation markto indicate that the Calc FFT function takes unproportionally long in casememory runs out and Windows uses the memory swapping option. Thelatest WinIQSIM revision 3.5 can only display FFT lengths up to 128kScorrectly. An FFT length of 4MS requires an AMIQ 04. Following warning
occurs when decreasing the FFT length:
Fig. 16 FFT Length Warning
No changes take place after pressing NO. After pressingYES all the not-
ches defined previously are deleted. This step is necessary because asmaller FFT length decreases resolution and can leads to an erraticnotch list display.
LINE SPACING Displays the frequency resolution of FFT lines, which is:
LINESPACING = SAMPLERATE/ FFTLENGTH
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Notch Related Parameters
Fig. 17 NPR Notch Related Parameters
NOTCH COUNT Specifies the number of notches within the current noise band-
width. With AUTOCALC NOTCHES the number of notches is restricted to:
NOTCHCOUNTNBW/ NOTCHWIDTH
NOTCH WIDTH The notch width is limited by the current noise bandwidth.
With AUTO CALC NOTCHES all notches have equal widths. If the notchwidth is smaller than the line spacing no notch will be generated. Range:
0.01 MHz - Noise Bandwidth.NOTCH DEPTH With AUTO CALC NOTCHES all notches have equal depths.
Range: 0 - 100 dB.
NOTCH OFFSET Specifies a frequency offset that is added to the notch
center frequencies with AUTO CALC NOTCHES. Avoid effects from insuffi-ciently suppressed carriers by moving the notch out of the danger zo-ne.
foffs
Fig. 18 NPR Notch Offset
AUTO CALC NOTCHES Automatically produces notches with the specifiedparameters to fit perfectly into the noise bandwidth range. The NotchCountis reduced, if necessary.
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Phase / Magnitude Distribution
Fig. 19 Phase / Magnitude Distribution
PHASE DISTRIBUTION
- RANDOM (CONST. SEED) I/Q-phase arrays are filled with random val-
ues between - and +. The random generator always starts withConst.Seed.
- RANDOM (CONTINUE) as above except that the random generator'sseed depends on the last value.
- PARABOLIC I- and Q- phase arrays are filled with an unsymmetrical
chirp signal ranging from - to +. This signal can be used to simulatea wobble generator.
- CONSTANT I/Q phase arrays are filled with constant values. This sig-
nal results in one or more peaks in time domain mode due to identicalphases of numerous frequency lines.
CUSTOM Loads a custom phase / magnitude configuration (*.pmc) file. Af-ter loading the *.pmc file the FFT length input field is dimmed and thenumber of FFT elements in the file is used. The file has the structureshown below.
4096 Element count (usually based on 2n)
0 -3.145e0 0.95
magnitude (range 0 to 1.0)
index nr (range 0 to element count)
phase offset (range )
......
4095 2.4567e0 0.34
Notch List
All active fields (not dimmed) of the notch list can be edited except Notchindex. If there are more than 10 items use the scroll bar to display the de-sired notch configuration line. Since all values are based on a discrete 2
N
array it is likely that a straight value, e.g. 10.00000 is locked to the nearestpoint in the array, e.g. 9.987654. The resolution depends on the FFT length.
Fig. 20 Notch List
Note: All values displayed in one line depend on each other.The last in-put value reconfigures the other ones to make sense.
NOTCH Displays the notch index number.
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CENTER FREQ Edit notch center frequency. Range:
fcarrier NBW / 2 fcenter fcarrier+ NBW / 2
WIDTH Specifies the notch width. Range: 0 - NBW.
START FREQUENCY The start frequency is calculated as:
fstart = fcenter Width / 2
STOP FREQUENCY The stop frequency is calculated as:
fstop = fcenter+ Width / 2
START INDEX Notch's first frequency line number. Range:
FFT Length / 2 - FFT length * (NBW / SRate) / 2 Start Index