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Agenda
Spectrum Analyzer Basics
Overview:
What is spectrum analysis?
What measurements do we make?
Theory of Operation:
Spectrum analyzer hardware
Specifications:
Which are important and why?
Features
Making the analyzer more effective
Summary
Appendix
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Overview
Types of Tests Made
.
Modulation
Noise
Distortion
Spectrum Analyzer Basics
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Overview
Frequency versus Time Domain
Amplitude
(power)
Time domain
Measurements
Spectrum Analyzer Basics
Frequency Domain
Measurements
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Overview
Different Types of Analyzers
Fourier Analyzer
A
Parallel filters measured
simultaneously
LCD shows full
spectral display
f1
Spectrum Analyzer Basics
f2
f
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Overview
Different Types of Analyzers
Swept Analyzer
A
Filter 'sweeps' over range
of interest
LCD shows full
spectral display
f1
Spectrum Analyzer Basics
f2
f
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Theory of Operation
Spectrum Analyzer Block Diagram
RF input
attenuator
IF gain
IF filter
detector
mixer
Input
signal
Log
Amp
Pre-Selector
Or Low Pass
Filter
video
filter
local
oscillator
sweep
generator
Crystal
Reference
Spectrum Analyzer Basics
CRT display
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Theory of Operation
MIXER
Mixer
f sig
input
RF IF
LO
f LO+ f sig
f LO- f sig
f sig
f LO
f LO
Spectrum Analyzer Basics
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Theory of Operation
IF FILTER
IF Filter
Input
Spectrum
IF Bandwidth
(RBW)
Display
Spectrum Analyzer Basics
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Theory of Operation
Detector
DETECTOR
amplitud
e
"bins"
Positive detection: largest value
in bin displayed
Negative detection: smallest value
in bin displayed
Sample detection: last value in bin
displayed
Spectrum Analyzer Basics
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Theory of Operation
Video Filter
VIDEO
FILTER
Spectrum Analyzer Basics
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Theory of Operation
Other Components
LO
SWEEP
GEN
RF INPUT
ATTENUATOR
Spectrum Analyzer Basics
frequency
LCD DISPLAY
IF GAIN
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Theory of Operation
How it all works together
fs
0
Signal Range
1
2
LO Range
f LO
f LO- f s
3 (GHz)
f LO+ f s
fs
IF filter
mixer
0
1
input
fs 2
4
3
3.6
5
6
detector
6.5
3.6
f IF
sweep generator
A
LO
f LO
0
4
3
5
3.6
Spectrum Analyzer Basics
6
(GHz)
1
2
3 (GHz) f
LCD display
6.5
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Theory of Operation
Front Panel Operation
Primary functions
(Frequency, Amplitude,
Span)
Softkeys
8563A
SPECTRUM ANALYZER
9 kHz - 26.5 GHz
Control functions
(RBW, sweep time,
VBW)
RF Input
Spectrum Analyzer Basics
Numeric
keypad
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Specifications
8563A
SPECTRUM ANALYZER
9 kHz - 26.5 GHz
Frequency Range
Accuracy: Frequency & Amplitude
Resolution
Sensitivity
Distortion
Dynamic Range
Spectrum Analyzer Basics
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Specifications
Frequency Range
Low frequencies
for baseband and IF
Measuring harmonics
50 GHz and beyond!
Spectrum Analyzer Basics
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Specifications
Accuracy
Absolute
Amplitude
in dBm
Relative
Amplitude
in dB
Frequency
Relative
Frequency
Spectrum Analyzer Basics
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Specifications
Accuracy: Frequency Readout Accuracy
Typical datasheet specification:
Spans < 2 MHz:
+
_
(freq. readout x freq. ref. accuracy
+ 1% of frequency span
+ 15% of resolution bandwidth
+ 10 Hz "residual error")
Frequency
Spectrum Analyzer Basics
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Specifications
Accuracy: Frequency Readout Accuracy Example
Single Marker Example:
2 GHz
400 kHz span
3 kHz RBW
Calculation:
Spectrum Analyzer Basics
-7
(2x10 9Hz) x (1.3x10
/yr.ref.error)
1% of 400 kHz span
15% of 3 kHz RBW
10 Hz residual error
Total =
=
=
=
=
+
_
260 Hz
4000 Hz
450 Hz
10 Hz
4720 Hz
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Specifications
Resolution: Resolution Bandwidth
Mixer
3 dB BW
3 dB
Detector
Input
Spectrum
LO
IF Filter/
Resolution Bandwidth Filter
(RBW)
Sweep
RBW
Display
Spectrum Analyzer Basics
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Specifications
Resolution: RBW Type and Selectivity
3 dB
3 dB BW
60 dB
60 dB
BW
Selectivity
Spectrum Analyzer Basics
=
60 dB BW
3 dB BW
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Specifications
Resolution: RBW Type and Selectivity
RBW = 1 kHz
Selectivity 15:1
RBW = 10 kHz
3 dB
distortion
products
7.5 kHz
60 dB
60 dB BW
= 15 kHz
10 kHz 10 kHz
Spectrum Analyzer Basics
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Specifications
Resolution: Residual FM
Residual FM
"Smears" the Signal
Spectrum Analyzer Basics
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Specifications
Resolution: Noise Sidebands
Phase Noise
Noise Sidebands can prevent
resolution of unequal signals
Spectrum Analyzer Basics
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Specifications
Resolution: RBW Determines Measurement Time
Swept too fast
Penalty For Sweeping Too Fast
Is An Uncalibrated Display
Spectrum Analyzer Basics
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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 Analyzer Basics
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Specifications
Sensitivity/DANL
Sensitivity is the Smallest Signal That
Can Be Measured
Signal
Equals
Noise
Spectrum Analyzer Basics
2.2 dB
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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 Analyzer Basics
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Specifications
Dynamic Range
+30 dBm
MAXIMUM POWER LEVEL
-10 dBm
MIXER COMPRESSION
-35 dBm
THIRD-ORDER DISTORTION
LCD-DISPLAY MEASUREMENT
SECOND-ORDER
RANGE
-45 dBm
DISTORTION
RANGE
145 dB
80 dB
SIGNAL/NOISE
NOISE
RANGE
105 dB
0 dBc SIDEBANDS
SIGNAL /3rd ORDER
DISTORTION
80 dB RANGE
INCREASING
SIGNAL/ 2nd ORDER
SIGNAL/NOISE
DISTORTION
BANDWIDTH OR
70 dB RANGE SIDEBANDS
ATTENUATION
60 dBc/1kHz
-115 dBm (1 kHz BW & 0 dB ATTENUATION)
Spectrum Analyzer Basics
MINIMUM NOISE FLOOR
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Features
Modulation Measurements: FFT
Swept Frequency Domain
FFT Frequency Domain
LIN
10 dB/
MARKER
1 kHz
-26 dBc
CENTER 100 MHz
Spectrum Analyzer Basics
MARKER
1 kHz
-26 dBc
SPAN 10 kHz
CENTER 100 MHz
SPAN 0 Hz
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Features
Modulation Measurements: AM/FM Detector with Speakers
8563A
Spectrum Analyzer Basics
SPECTRUM ANALYZER
9 kHz - 26.5 GHz
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Features
Noise Measurements: Noise Marker & Video Averaging
8563A
SPECTRUM ANALYZER
MKR 1.025 MHz
-135.75 dBm/Hz
Spectrum Analyzer Basics
9 kHz - 26.5 GHz
AVG
10
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Features
Stimulus Response: Tracking Generator
Receiver
Source
DUT
Spectrum Analyzer
RF in
CRT
Display
IF
DUT
LO
TG out
Tracking
Adjust
Tracking Generator
Spectrum Analyzer Basics
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