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Spectrum Analyzer Basics Copyright2000
Agenda
Overview:W hat is spectrum analysis?W hat m easurem ents do we m ake?
Theory of Operation:Spectrum analyzer hardware
Specifications:W hich are im portant and why?
FeaturesM aking the analyzer m ore effective
Sum m aryAppendix
Spectrum Analyzer Basics Copyright2000
O verviewTypes of Tests M ade .
M odulationM odulation
DistortionDistortion
NoiseNoise
Spectrum Analyzer Basics Copyright2000
O verviewFrequency versus Tim e Dom ain
time
Am plitude(power) frequ
ency
Tim e dom ainM easurem ents
Frequency Dom ainM easurem ents
Spectrum Analyzer Basics Copyright2000
O verviewDifferent Types of Analyzers
Parallel filters m easuredsim ultaneously
LCD shows fullspectral display
A
ff1 f2
Fourier Analyzer
Spectrum Analyzer Basics Copyright2000
O verviewDifferent Types of Analyzers
A
ff1 f2
Filter 'sweeps' over rangeof interest
LCD shows fullspectral display
Swept Analyzer
Spectrum Analyzer Basics Copyright2000
Theory of OperationSpectrum Analyzer Block Diagram
Pre-SelectorOr Low Pass
Filter
CrystalReference
LogAm p
RF inputattenuator
m ixerIF filter
detector
videofilter
localoscillator
sweepgenerator
IF gain
Inputsignal
CRT display
Spectrum Analyzer Basics Copyright2000
Theory of OperationM ixer
M IXER
fsig
LOf
fsig LOf
LOf fsig-
LOf fsig+RF
LOIF
input
Spectrum Analyzer Basics Copyright2000
IF FILTER
Display
InputSpectrum
IF Bandwidth(RBW )
Theory of OperationIF Filter
Spectrum Analyzer Basics Copyright2000
Theory of OperationDetector DETECTO R
Negative detection: sm allest value in bin displayed
Positive detection: largest value in bin displayed
Sam ple detection: last value in bindisplayed
"bins"
am plitude
Spectrum Analyzer Basics Copyright2000
Theory of OperationVideo Filter
VIDEOFILTER
Spectrum Analyzer Basics Copyright2000
Theory of OperationOther Com ponents
LCD DISPLAY
SW EEPG EN
LO
IF G AIN
frequency
RF INPUTATTENUATO R
Spectrum Analyzer Basics Copyright2000
Theory of OperationHow it all works together
3.6(GHz)
(GHz)
0 3 61 2 4 5
0 31 2
3 64 5
3.6
(GHz)0 31 2
fIF
Signal Range LO Range
fs
sweep generator
LO
LCD display
input
m ixer
IF filter
detector
A
f
fLO
fs
fs
fs
fLO-
fs
fLO+
fLO
3.6 6.5
6.5
Spectrum Analyzer Basics Copyright2000
Theory of OperationFront Panel Operation
8563ASPECTRUM ANALYZER 9 kHz - 26.5 GHz
RF Input Num erickeypad
Control functions(RBW , sweeptim e, VBW )
Prim ary functions(Frequency, Am plitude,
Span)Softkeys
Spectrum Analyzer Basics Copyright2000
Specifications
8563ASPECTRUM ANALYZER 9 kHz - 26.5 GHz
Frequency RangeAccuracy: Frequency & Am plitudeResolutionSensitivityDistortionDynam ic Range
Spectrum Analyzer Basics Copyright2000
SpecificationsFrequency Range
M easuring harm onics50 G Hz and beyond!M easuring harm onics50 G Hz and beyond!
Low frequenciesfor baseband and IFLow frequencies
for baseband and IF
Spectrum Analyzer Basics Copyright2000
SpecificationsAccuracy
AbsoluteAm plitude
in dBm
RelativeAm plitudein dB
RelativeFrequency
Frequency
Spectrum Analyzer Basics Copyright2000
SpecificationsAccuracy: Frequency Readout Accuracy
Typical datasheet specification:
Spans < 2 M Hz: (freq. readout x freq. ref. accuracy + 1% of frequency span + 15% of resolution bandwidth + 10 Hz "residual error")
+_
Frequency
Spectrum Analyzer Basics Copyright2000
SpecificationsAccuracy: Frequency Readout Accuracy Exam ple
Single M arker Exam ple:
1% of 400 kHz span15% of 3 kHz RBW10 Hz residual error
+_
2 GHz400 kHz span3 kHz RBW
Calculation: (2x10 Hz) x (1.3x10 /yr.ref.error)9 -7 ====
260 Hz4000 Hz450 Hz10 Hz
4720 HzTotal =
Spectrum Analyzer Basics Copyright2000
SpecificationsResolution: Resolution Bandwidth
3 dB3 dB BW
LO
M ixer
IF Filter/Resolution Bandwidth Filter
(RBW )Sweep
Detector
InputSpectrum
Display
RBW
Spectrum Analyzer Basics Copyright2000
SpecificationsResolution: RBW Type and Selectivity
3 dB
60 dB
60 dBBW
60 dB BW
3 dB BW
3 dB BW
Selectivity =
Spectrum Analyzer Basics Copyright2000
SpecificationsResolution: RBW Type and Selectivity
10 kHz
RBW = 10 kHzRBW = 1 kHzSelectivity 15:1
10 kHz
distortionproducts
60 dB BW= 15 kHz
7.5 kHz
3 dB
60 dB
Spectrum Analyzer Basics Copyright2000
SpecificationsResolution: Residual FM
Residual FM"Sm ears" the Signal
Spectrum Analyzer Basics Copyright2000
SpecificationsResolution: Noise Sidebands
Noise Sidebands can preventresolution of unequal signals
Phase Noise
Spectrum Analyzer Basics Copyright2000
SpecificationsResolution: RBW Determ ines M easurem ent Tim e
Penalty For Sweeping Too FastIs An Uncalibrated Display
Swept too fast
Spectrum Analyzer Basics Copyright2000
SpecificationsSensitivity/DANL
10 dB
Attenuation = 10 dB Attenuation = 20 dB
signal level
Effective Level of Displayed Noise is aFunction of RF Input Attenuation
Effective Level of Displayed Noise is aFunction of RF Input Attenuation
Signal-To-Noise Ratio Decreases asRF Input Attenuation is Increased
Spectrum Analyzer Basics Copyright2000
SpecificationsSensitivity/DANL
SignalEqualsNoise
Sensitivity is the Sm allest Signal ThatCan Be M easured
Sensitivity is the Sm allest Signal ThatCan Be M easured
2.2 dB
Spectrum Analyzer Basics Copyright2000
SpecificationsSensitivity/DANL
Narrowest Resolution BW
M inim um RF Input Attenuation
Sufficient Video Filtering(Video BW < .01 Res BW )
For Best Sensitivity Use:For Best Sensitivity Use:
Spectrum Analyzer Basics Copyright2000
SpecificationsDynam ic Range
+30 dBm
-115 dBm (1 kHz BW & 0 dB ATTENUATION)
M AXIM UM POW ER LEVEL
LCD-DISPLAY
RANG E80 dB
-10 dBm
-35 dBm
-45 dBm
INCREASINGBANDW IDTH O RATTENUATION
SECOND-ORDERDISTO RTION
M IXER COM PRESSION
THIRD-ORDER DISTORTION
SIGNAL/NOISERANGE105 dB
RANGE145 dB
M EASUREM ENT
M INIM UM NOISE FLOOR
70 dB RANGEDISTORTION
80 dB RANGEDISTORTION
0 dBcNOISESIDEBANDS
60 dBc/1kHz
SIGNAL /3rd ORDER
SIGNAL/ 2nd ORDERSIGNAL/NOISESIDEBANDS
Spectrum Analyzer Basics Copyright2000
FeaturesM odulation M easurem ents: FFT
LIN
CENTER 100 M Hz SPAN 0 Hz
M ARKER1 kHz-26 dBc
10 dB/
CENTER 100 M Hz SPAN 10 kHz
M ARKER1 kHz-26 dBc
Swept Frequency Dom ain FFT Frequency Dom ain
Spectrum Analyzer Basics Copyright2000
FeaturesM odulation M easurem ents: AM /FM Detector with Speakers
8563ASPECTRUM ANALYZER 9 kHz - 26.5 GHz
Spectrum Analyzer Basics Copyright2000
FeaturesNoise M easurem ents: Noise M arker & Video Averaging
8563ASPECTRUM ANALYZER 9 kHz - 26.5 GHz
1.025 M HzM KR-135.75 dBm /Hz
AVG10
Spectrum Analyzer Basics Copyright2000
FeaturesStim ulus Response: Tracking Generator
DUT
SourceReceiver
IF
LO
CRTDisplay
Tracking Generator
Tracking
RF in
Spectrum Analyzer
TG out
Adjust
DUT
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