No Slide Titlewireless.ictp.it/school_2002/lectures/ermanno/HTML/... · 2008-01-25 · Title: No Slide Title Author: Lynn Denley-Bussard Created Date: 2/28/2002 10:29:56 PM

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


O verviewTypes of Tests M ade .

M odulationM odulation

DistortionDistortion

NoiseNoise


O verviewFrequency versus Tim e Dom ain

time

Am plitude(power) frequ

ency

Tim e dom ainM easurem ents

Frequency Dom ainM easurem ents


O verviewDifferent Types of Analyzers

Parallel filters m easuredsim ultaneously

LCD shows fullspectral display

A

ff1 f2

Fourier Analyzer


O verviewDifferent Types of Analyzers

A

ff1 f2

Filter 'sweeps' over rangeof interest

LCD shows fullspectral display

Swept Analyzer


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


Theory of OperationM ixer

M IXER

fsig

LOf

fsig LOf

LOf fsig-

LOf fsig+RF

LOIF

input


IF FILTER

Display

InputSpectrum

IF Bandwidth(RBW )

Theory of OperationIF Filter


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


Theory of OperationVideo Filter

VIDEOFILTER


Theory of OperationOther Com ponents

LCD DISPLAY

SW EEPG EN

LO

IF G AIN

frequency

RF INPUTATTENUATO R


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


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


Specifications


Frequency RangeAccuracy: Frequency & Am plitudeResolutionSensitivityDistortionDynam ic Range


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


SpecificationsAccuracy

AbsoluteAm plitude

in dBm

RelativeAm plitudein dB

RelativeFrequency

Frequency


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


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 =


SpecificationsResolution: Resolution Bandwidth

3 dB3 dB BW

LO

M ixer

IF Filter/Resolution Bandwidth Filter

(RBW )Sweep

Detector

InputSpectrum

Display

RBW


SpecificationsResolution: RBW Type and Selectivity

3 dB

60 dB

60 dBBW

60 dB BW

3 dB BW

3 dB BW

Selectivity =


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


SpecificationsResolution: Residual FM

Residual FM"Sm ears" the Signal


SpecificationsResolution: Noise Sidebands

Noise Sidebands can preventresolution of unequal signals

Phase Noise


SpecificationsResolution: RBW Determ ines M easurem ent Tim e

Penalty For Sweeping Too FastIs An Uncalibrated Display

Swept too fast


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



SignalEqualsNoise

Sensitivity is the Sm allest Signal ThatCan Be M easured

Sensitivity is the Sm allest Signal ThatCan Be M easured

2.2 dB



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:


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


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


FeaturesM odulation M easurem ents: AM /FM Detector with Speakers



FeaturesNoise M easurem ents: Noise M arker & Video Averaging


1.025 M HzM KR-135.75 dBm /Hz

AVG10


FeaturesStim ulus Response: Tracking Generator

DUT

SourceReceiver

IF

LO

CRTDisplay

Tracking Generator

Tracking

RF in

Spectrum Analyzer

TG out

Adjust

DUT

Documents

No Slide Titlewireless.ictp.it/school_2002/lectures/ermanno/HTML/... · 2008-01-25 · Title: No Slide Title Author: Lynn Denley-Bussard Created Date: 2/28/2002 10:29:56 PM