Transcript No Slide Title

What is the Difference Between
Network and Spectrum Analyzers?
.
Amplitude
Amplitude Ratio
8563A
Measures
known
signal
Frequency
Network analyzers:




measure components, devices,
circuits, sub-assemblies
contain source and receiver
display ratioed amplitude and phase
(frequency or power sweeps)
offer advanced error correction
SPECTRUM ANALYZER
9 kHz - 26.5 GHz
Measures
unknown
signals
Frequency
Spectrum analyzers:




measure signal amplitude characteristics
carrier level, sidebands, harmonics...)
can demodulate (& measure) complex
signals
are receivers only (single channel)
can be used for scalar component test (no
phase) with tracking gen. or ext. source(s)
Spectrum Analysis Basics
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Overview
Types of Tests Made
Modulation
Noise
Distortion
Spectrum Analysis Basics
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Overview
Frequency versus Time Domain
Amplitude
(power)
Time domain
Measurements
Frequency Domain
Measurements
Spectrum Analysis Basics
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Overview
Different Types of Analyzers
Swept Analyzer
Filter 'sweeps' over range of interest
A
CRT shows full spectral
display
f1
f2
f
Spectrum Analysis Basics
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Theory of Operation
Spectrum Analyzer Block Diagram
RF input
attenuator
mixer
IF gain
IF filter
Input
signal
detector
Log
Amp
Pre-Selector
Or Low Pass
Filter
video
filter
local
oscillator
sweep
generator
Crystal
Reference
CRT display
Spectrum Analysis Basics
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Theory of Operation
Mixer
MIXER
input
f sig
RF
LO
f LO + f sig
f LO - f sig
IF
f sig
f LO
f LO
Spectrum Analysis Basics
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Theory of Operation
IF Filter
IF FILTER
Input
Spectrum
IF Bandwidth
(RBW)
Display
Spectrum Analysis Basics
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Theory of Operation
Detector
DETECTOR
amplitude
"bins"
Positive detection: largest value
in bin displayed
Negative detection: smallest value
in bin displayed
Sample detection: last value in bin displayed
Spectrum Analysis Basics
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Theory of Operation
Video Filter
VIDEO FILTER
Spectrum Analysis Basics
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Theory of Operation
Other Components
LO
SWEEP GEN
RF INPUT
ATTENUATOR
frequency
CRT DISPLAY
IF GAIN
Spectrum Analysis Basics
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Theory of Operation
How it all works together
f
0
LO Range
Signal Range
s
1
2
f
3 (GHz)
mixer
f
LO
-
f
f
s
f
LO
LO
s
0
f
s
IF filter
1
input
+
f
s
2
3
3.6
4
5
6
detector
6.5
3.6
f
sweep generator
IF
A
LO
f
LO
3
0
3.6
4
5
6
(GHz)
1
2
3 (GHz)
CRT display
6.5
Spectrum Analysis Basics
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f
Specifications
Sensitivity/DANL
Effective Level of Displayed Noise is a Function of RF Input
Attenuation
signal level
10 dB
Attenuation = 10 dB
Attenuation = 20 dB
Signal-To-Noise Ratio Decreases as
RF Input Attenuation is Increased
Spectrum Analysis Basics
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Specifications
Sensitivity/DANL: IF Filter (RBW)
Displayed Noise is a Function of IF Filter Bandwidth
100 kHz RBW
10 dB
10 kHz RBW
10 dB
1 kHz RBW
Decreased BW = Decreased Noise
Spectrum Analysis Basics
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Specifications
Sensitivity/DANL: VBW
Video BW Smoothes Noise for Easier Identification of Low
Level Signals
Spectrum Analysis Basics
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Specifications
Sensitivity/DANL
For Best Sensitivity Use:

Narrowest Resolution BW

Minimum RF Input Attenuation

Sufficient Video Filtering
(Video BW < .01 Res BW)
Spectrum Analysis Basics
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