and Southeastern Michigan
present…
Important Characteristics of
Digital Oscilloscopes
Vince Woerdeman,
Agilent Technologies
and
RADAR Pulse Measurements
with Digital Oscilloscopes
Marty Gubow,
Agilent Technologies
5:30 – 6:00 Pizza and Refreshments
6:00 – 7:00 Technical Presentation
This is a FREE event.
Non-Members Welcome!
1
Agenda
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Evaluating a Scope’s Performance
Characteristics
ƒ What Bandwidth is needed?
ƒ What Sample Rate is needed?
ƒ How does Nyquist’s Theorem and
aliasing apply to oscilloscopes?
ƒ Acquisition Errors and Interleave
Distortion
ƒ What are other important
characteristics?
Page 2
Evaluating Performance Characteristics
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ƒ Is Full Scope Functionality Retained?
ƒ Required Number of Channels?
ƒ Required Bandwidth/Acquisition Performance?
ƒ Waveform Update Rate, Decode Update Rate, Probing,
Ease-of-use, Display Quality, Triggering, etc.?
Page 3
“Rule-of-thumb” Bandwidth Suggestion
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Scope Bandwidth
Suggested Bandwidth = 5X Highest Clock Rate
Allows capture of the 5th harmonic with minimum attenuation.
Page 4
Accurate Bandwidth Determination
Step #1:
Determine
fastest
rise/fall style
times of device-under-test.
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to edit
Master
subtitle
Step #2: Determine highest signal frequency content (fKnee).
fKnee = 0.5/RT (10% - 90%)
fKnee = 0.4/RT (20% - 80%)
Step #3: Determine degree of required measurement accuracy.
Required
Accuracy
20%
Gaussian
Response
BW = 1.0 X fKnee
Maximally-flat
Response
BW = 1.0 X fKnee
10%
BW = 1.3 X fKnee
BW = 1.2 X fKnee
3%
BW = 1.9 X fKnee
BW = 1.4 X fKnee
Step #4: Calculate required bandwidth.
Source: Dr. Howard W. Johnson, “High-speed Digital Design – A Handbook of Black Magic”
Page 5
System Bandwidth Calculation
Example
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Determine the minimum required bandwidth of an
oscilloscope with an approximate Gaussian frequency
response to measure a 500ps rise-time (10-90%):
fKnee = (0.5/500ps) = 1GHz
3% Accuracy: Scope Bandwidth = 1.9
1.4 x 1GHz = 1.9GHz
1.4GHz
20% Accuracy: Scope Bandwidth = 1.0 x 1GHz = 1.0GHz
Page 6
Analog Bandwidth Comparisons
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style
Whattodoes
a 100 MHz
clock
signal really look like?
Rise Time = 495ps
Rise Time = 550ps
Rise Time = 750ps
Rise Time = 2.5ns
100MHz Scope
500MHz
Scope
Page 7
1GHz
Scope
2GHz
Scope
How Much Sample Rate is Required?
Engineer
FredMaster
has total
trust instyle
Dr. Nyquist and says:
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to edit
subtitle
“2X over the scope’s
bandwidth.”
Engineer Betty doesn’t trust Dr. Nyquist and says:
“10X to 20X over the
scope’s bandwidth.”
The truth lies somewhere in between!
Page 8
Nyquist’s Sampling Theorem
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Nyquist’s sampling theorem states that for a
limited bandwidth (band-limited) signal with
maximum frequency fmax, the equally spaced
sampling frequency fs must be greater than twice
of the maximum frequency fmax, i.e.,
fs > 2·fmax
in order to have the signal be uniquely
reconstructed without aliasing.
The frequency 2·fmax is called the Nyquist
sampling rate (fS). Half of this value, fmax, is
sometimes called the Nyquist frequency (fN).
Dr. Harry Nyquist
Page 9
Nyquist’s Basic Rules…
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But not-so-simple for DSO technology
1. fMAX < fS/2
9
The highest frequency sampled MUST be less than fS/2…
9
This is NOT the same as oscilloscope bandwidth.
2. Samples MUST be equally spaced
9
The forgotten rule!
Page 10
Ideal Brick-wall Response w/ BW @ Nyquist (fN)
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0dB
Attenuation
-3dB
fN
Frequency
Page 11
fS
Gaussian Response w/ BW @ fS/2 (fN)
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0dB
Attenuation
-3dB
Aliased Frequency Components
fN
Frequency
Page 12
fS
500MHz scope sampling @ 1GSa/s (BW = fSS/2 = fNN)
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Page 13
Maximally-Flat
Response
w/ BW
Gaussian Response
w/ BW
@ f@
/4fS(f/2.5
/2)(fN/1.25)
S/2
N)
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0dB
Attenuation
-3dB
Aliased Frequency Components
Aliased Frequency Components
fS/4
fS/2.5
fN
Frequency
Page 14
fS
500-MHz scope (2 GSa/s vs. 4 GSa/s)
Input = 100 MHz clock with 1 ns edge speeds
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2 GSa/s (fBW = fS/4 = fN/2)
4 GSa/s (fBW = fS/8 = fN/4)
Page 15
6-GHz scope (20 GSa/s vs. 40 GSa/s)
1.25 GHz clock with 100 ps edge speeds
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20 GSa/s (fBW = fS/3.3)
40 GSa/s (fBW = fS/6.6)
Page 16
Complying with Nyquist’s Rule #1 (fS > 2 x fMAX)
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ƒ 2X sampling violates Rule #1
ƒ 2.5X to 5X sampling sufficiently satisfies Rule #1
ƒ > 5X sampling provides further compliance with Rule
#1… IF additional error sources are not introduced
that violate Rule #2
Engineers often overlook Rule #2…
“Samples MUST be evenly spaced”
Page 17
Real-time Non-interleaved ADC System
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Input
ADC #1
ACQ
MEM
To CPU
Analog
Amplifier
Sample
Clock
Page 18
Sample Rate > 4 x fBW (Non-interleaved)
Sin(x)/x
Input Signal
Interpolated
Waveform
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Sample
Clock
= Input Signal
= Sample Clock
= Sin(x)/x Interpolated Waveform
= Real-time Digitized Point
Page 19
Real-time Interleaved ADC System
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Input
ADC #1
ACQ
MEM
To CPU
Analog
Amplifier
Input
½ Clock
Delay
ADC #2
ACQ
MEM
Accurate ADC interleaving requires:
1.
Matched vertical response of each ADC
2.
Precise phased-delayed clocking
Page 20
Sample
Clock
To CPU
SR > 8 x fBW (Perfectly Interleaved)
Sin(x)/x
Interpolated
Waveform
Input Signal
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Clock #1
Clock #2
= Input Signal
= Sample Clock
= Sin(x)/x Interpolated Waveform
= Real-time Digitized Point
Page 21
SR > 8 x fBW (Poorly Interleaved)
Sin(x)/x
Interpolated
Waveform
Input Signal
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Clock #1
Clock #2
= Input Signal
= Sample Clock
= Sin(x)/x Interpolated Waveform
= Real-time Digitized Point
Page 22
Testing for Interleave Distortion
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subtitle
style
distortion
violates
Nyquist’s Rule #2:
“Samples must be evenly spaced”
1. Effective bits analysis using sine waves
2. Visual sine wave test
3. Spectrum analysis
4. Measurement stability/repeatability
Page 23
1-GHz Sine Wave on 1-GHz BW Scopes
4 GSa/s (non-interleaved)
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20 GSa/s (interleaved)
Interleave Distortion
4 GSa/s produces superior results compared to 20 GSa/s
Page 24
2.5-GHz Sine Wave on a 3-GHz Scope
20 GSa/s (Single-chip ADC)
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40 GSa/s (Dual-interleaved ADC chip-set)
Vp-p (σ) = 2.4
mV
Vp-p (σ) = 1.8 mV
Precision ADC interleaving technology produces improved measurements
Page 25
2.5-GHz Sine Wave on a 2.5-GHz Scope
10 GSa/s (Single-chip ADC)
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40 GSa/s (Quad-interleaved ADC chip-set)
Interleave Sampling Distortion
Vp-p (σ) = 9.1
mV
Vp-p (σ) = 12.0 mV
Poor ADC interleaving technology produces degraded measurements
Page 26
FFT Analysis of 2.5-GHz Sine Wave at 40 GSa/s
3-GHz Scope
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2.5-GHz Scope
10-GSa/s Distortion (-32 dB)
40-GSa/s Distortion
Page 27
400-MHz Clock Sampled @ 40 GSa/s
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3-GHz Scope
2.5-GHz Scope
Rise Time (avg.) = 250ps
Rise Time (range) = 35ps
Rise Time (σ) = 3.3ps
Rise Time (avg.) = 254ps
Rise Time (range) = 60ps
Rise Time (σ) = 10ps
Page 28
FFT Analysis of 400-MHz Clock at 40 GSa/s
3-GHz to
Scope
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2.5-GHz Scope
10-GSa/s Distortion
(27 dB below 5th harmonic)
Page 29
40-GSa/s Distortion
Other Oscilloscope Characteristics to Consider
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ƒ Waveform Update Rate
ƒ Advance Analysis
ƒ Display Quality
ƒ Ease-of-use
ƒ Probing
ƒ Price
Page 30
InfiniiMax Active Probe Extension
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Allows for environmental chamber testing up 105 degrees C.
Page 31
Questions and Answers
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Page 32
Oscilloscope
Radar
Measurement
Basics
33
Agenda
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• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Page 34
Radar Measurement Basics
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Introduction
Page 35
Radar Measurement Basics
Some Typical Radar Applications
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• Surveillance
• Proximity fuses
• Search and track
• Fire control
• Navigation
• Missile guidance
• Altimeter
• Terrain avoidance
• Weather mapping
• Space
Page 36
Radar Measurement Basics
The Wide Range of Measurement
Requirements
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Parameter
Typical Range
• Frequency………………………………..100MHz - 95GHz
• Pulse Width (PW)……………………….10nsec to Infinite
(CW)
• Pulse Repetition Frequency …………30Hz to 300KHz
• Rise Time………………………………...1nsec - 100nsec
• Duty Cycle……………………………….0.01% - 100%
• Peak Power………………………….…..1W - 50MW
• Pulse Compression…………………….FM, Phase Coded
• Frequency Agility……………………….100MHz - 2GHz (BW)
Page 37
Radar Measurement Basics
Simplified Pulse Doppler Radar
Block Diagram
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COHO
BPF
RF
BPF
AMP
STALO
PRF
GENERATOR
Antenna
PULSED
DUPLEXER
PREDRIVER POWER
AMP
TRANSMITTER
PULSE
MODULATOR
RECEIVER
PROTECTION
Transmitter/Exciter
LNA
ADC
DI
SP
LA
Y
Doppler
and
Range
FFT
Processor
S/H
LPF
VIDEO
AMP
FREQUENCY
AGILE L.O.
o
0
SPLITTER
COHO LIMITER LPF
o
90
2nd
IFA
1st
IFA
IF
BPF
IF
BPF
2nd
L.O.
ADC
S/H
LPF
VIDEO
AMP
Receiver/Signal Processor
Page 38
Radar Measurement Basics
Active Electronically Steered
Antenna
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ont
r
F
e
Wav
Transceiver
Animation
Page 39
Radar Measurement Basics
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Page 40
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Page 41
Agenda
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• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Jitter Measurements
• Time Domain Measurements
Page 42
Radar Measurement Basics
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Pulsed Power and Power Spectrum
Measurements
Page 43
Radar Measurement Basics
Why Measure Power?
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• High peak power influences the expense of the
system
$
$
Modulator,
PFN, etc.
Output
Stage
• Power determines the absolute
range
R
∝
4
Pt
R
Page 44
Radar Measurement Basics
Instruments Used to Measure
Power
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• Power
Meter
• Vector Signal
Analyzer
• Spectrum
Analyzer
Radar Measurement Basics
Page 45
Agenda
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• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Page 46
Radar Measurement Basics
Noise Figure
-theto
degradation
in thesubtitle
signal-to-noise
Click
edit Master
style ratio as the signal passes
through the network
S
N
in
Noise Figure, F =
S
N
G
(S/N)in
(S/N)out
T = 290°K
Page 47
Radar Measurement Basics
out
N8975A Noise Figure Analyzer
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• Wide frequency range
(1.5GHz/3GHz/26.5GHz)
• Graphical data display
• Ease of use
• Variable IF bandwidths
• Intuitive user interface
• Smart Noise Source (cal
files stored in EEPROM
and internal temperature
sensor)
Page 48
Radar Measurement Basics
Agenda
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• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Jitter Measurements
• Time Domain Measurements
Page 49
Radar Measurement Basics
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Component Test
Page 50
Radar Measurement Basics
Why make Network Analyzer
measurements on a Radar
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• Verify specifications of “building blocks” for more
complex RF systems
• Ensure distortionless transmission of
communications signals
• Linear: constant amplitude/linear phase /
constant group delay
• Non-linear: harmonics, intermodulation,
compression, AM-to-PM conversion
• Ensure a good match when absorbing
power (e.g. an antenna)
Page 51
Radar Measurement Basics
The Need for Both Magnitude and
Phase
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S21 style
1. Complete
characterization of
linear networks
S11
S22
S12
2. Complex impedance
needed to design
matching circuits
4. Time-domain
characterization
Mag
3. Complex values
needed for device
modeling
High-frequency transistor model
Time
5. Vector-error correction
Error
Base
Collector
Emitter
Page 52
Radar Measurement Basics
Measured
Actual
PNA Performance Network Analyzer
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to edit Master subtitle style
Family
• Up to 35 μs/point
measurement speed
• 143 dB dynamic range
with direct receiver
access
• 128 dB dynamic range at
test ports
• 0.005 dB trace noise (10
kHz IF bandwidth
• 3, 6, 9, 20, 40, and 50
GHz microwave models
• 4 mixer-based receivers
enable TRL/LRM
Page 53 calibration
Radar Measurement Basics
Agenda
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• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Jitter Measurements
• Time Domain Measurements
Page 54
Radar Measurement Basics
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Evaluating I/Q
Demodulator Errors
Page 55
Radar Measurement Basics
Polar Display -- Magnitude and
Phase Represented Together
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M
a
g
Phas
e
0 deg
• Magnitude is an absolute value
• Phase is relative to a reference signal
Animation
Page 56
Radar Measurement Basics
Signal Changes or Modifications
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M
ag
Phase
Phase
0 deg
Magnitude Change
0 deg
Phase Change
0 deg
0 deg
Both Change
Frequency Change
Page 57
Radar Measurement Basics
89640 Vector Signal Analyzer
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• Tuners covering dc to 6.0
•
•
•
•
•
•
•
Page 58
Radar Measurement Basics
GHz Frequency Range
36-78 MHz bandwidth for
broadband signal formats.
>200MHz bandwidth with
54832B Infiniium scope
I/Q display formats
Analog AM/FM/PM
demodulation
Time Gated measurements
1.2Gbytes of capture
memory
Tight integration with ADS
(PC based design
applications).
PSG Performance Signal Generator Family
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• 250 kHz to 20 or 40 GHz Frequency Range in Coax
• Extension to 110 GHz with the 83550 Series
•
•
•
Multipliers
High power
Excellent phase noise
AM/FM/PM and pulse modulation capabilities
Page 59
Radar Measurement Basics
Agenda
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• Introduction
• Power Measurements
• Noise Measurements
• Component Test
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Page 60
Radar Measurement Basics
Agenda
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Pulsed Component
Measurements
Page 61
Radar Measurement Basics
Pulsed Transfer Functions in the
Time
Domain
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to edit
Master subtitle style
Amplifier
Page 62
Radar Measurement Basics
Agenda
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• Introduction
• Power Measurements
• Noise Measurements
• Component Test
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Page 63
Radar Measurement Basics
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Time Domain
Measurements
Page 64
Radar Measurement Basics
Why Measure Pulse Parameters?
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• PW determines resolving ability (small is better) BW ~ 1/PW
• PW affects average power (absolute range, large is
better)
R=
4
Pt G Gt
Pr (4 )
2
r
3
• Unintentional AM and fast rise times can reduce
the life expectancy of transmitter
• PRI determines unambiguous range
Page 65
Radar Measurement Basics
What are Important Pulse
Click
to edit Master subtitle style
Parameters?
Risetime
Falltime
Pulse
Width
Pulse
Off Time
Pulse Repetition
Interval (PRI),
Als
o:
1
PRF
• Duty cycle
• Pulse shape (over and preshoot, droop)
• Pulse width stability
• PRI stability
Page 66
Radar Measurement Basics
Definition of Pulse Width
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Average Power During On-time of Pulse
-6dB
Pulse Width
Pulse Repetition Interval
Page 67
Radar Measurement Basics
Time Domain Measurements
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Envelop parameters
Modulation in the pulse
• Rise time
• Unintentional
• Fall time
- AM to PM
• Pulse width
- Phase noise
• Period
• Intentional
• On/off ratio
- Chirp
- Barker coding
- Frequency agility
Page 68
Radar Measurement Basics
Measuring with a Digital
Oscilloscope
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Considerations
Advantages
• General measurement tool • Aliasing
• Wide bandwidth
• Dynamic range
• Easy to understand
• Flatness
• Option to post process
• Memory depth
signal
Page 69
Radar Measurement Basics
Time Domain Measurements
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COHO
BPF
RF
BPF
AMP
STALO
PRF
GENERATOR
Antenna
PULSED
DUPLEXER
PREDRIVER POWER
AMP
TRANSMITTER
PULSE
MODULATOR
RECEIVER
PROTECTION
Transmitter/Exciter
LNA
ADC
DI
SP
LA
Y
Doppler
and
Range
FFT
Processor
S/H
LPF
VIDEO
AMP
FREQUENCY
AGILE L.O.
o
0
SPLITTER
COHO LIMITER LPF
o
90
2nd
IFA
1st
IFA
IF
BPF
IF
BPF
2nd
L.O.
ADC
S/H
LPF
VIDEO
AMP
Receiver/Signal Processor
Page 70
Radar Measurement Basics
Infiniium Oscilloscope
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• 4 channels
• Up to 64 MB deep
memory
• Up to 40 GSa/s
sample rate/channel
• Infiniium awardwinning usability
• Full upgradeability
Page 71
Radar Measurement Basics
Agenda
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• Introduction
• Power Measurements
• Noise Measurements
• Component Test
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Page 72
Radar Measurement Basics
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Jitter
Measurements
Page 73
Radar Measurement Basics
What is Jitter?
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(a)
Threshold
(b)
Threshold
Jitter
(c)
-creates ambiguity in threshold
crossing
Threshold
Noise
Page 74
Radar Measurement Basics
Jitter Function
Ideal to
Pulse
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edit Master subtitle style
Train
Jitter signal viewed at
instants in time
Jitter function
Jitter magnitude
t1
t2
t3
t4
Page 75
Radar Measurement Basics
t5
What is Jitter?
• Jitter
is the deviation
a timing event
of a signal from its ideal position.
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to edit
Masterof subtitle
style
Ideal clock:
sin(2π f c t )
Jittered clock: sin (2π f c t + 43 π sin( 101 2π f c t ) )
4
3
Jitter:
2
3
π sin( 101 2π f c t )
UI
•
•
This is the traditional description of jitter,
commonly referred to Time Interval Error (TIE), or phase jitter.
Page 76
Radar Jitter Measurement
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PRI Reference
Trigger
PULSED
RADAR
Crystal Detector
Pulse Envelope
Jitter
Source
Page 77
Radar Measurement Basics
Digitizing
Oscilloscope
Ch1
Time Interval vs. Time Profile
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Peak-to-Peak Jitter Amplitude
Time
Interval
3.8 ns
17.9 KHz
Time
Jitter Periodic Rate
Page 78
Radar Measurement Basics
Histogram of Clock Period
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Probability Analysis
% Probability
Jitter Distribution
Period
MIN
-σ
MEAN
+σ
Peak-to-Peak
Page 79
Radar Measurement Basics
MAX
Histogram of Edge Jitter
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Page 80
“Real World” Jitter is Complex
Jittertoisedit
composed
random style
Click
Masterofsubtitle
and deterministic components
ƒ
Random Jitter (RJ) is
unbounded
•
•
•
•
ƒ
Due to thermal noise, shot
noise, etc.
Follows Gaussian
distribution
Requires statistical
analysis to be quantified
RJpp = 14.1 x Jrms for 1012 BER
DJ
Deterministic Jitter (DJ) is
bounded and composed
of:
•
•
Duty-Cycle-Distortion
(DCD)
Inter Symbol Interference
(ISI)
RJ
Page 81
Jitter Probability: BER
n ×σ random
=J
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pk − pk
deterministic
J
=
Page 82
How Do Real Time Scopes Measure
Jitter on Data?
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to edit Master subtitle style
NRZ
Serial
Data
Recovered
Clock
Jitter
Trend
Units in Time
Jitter
Spectrum
Units in Time
Jitter
Histogram
Page 83
Agilent EZJIT Jitter Measurement
Application
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Signal
Histogram
Trend
Spectrum
Page 84
Total Jitter Components
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TJ
Bounded (p-p)
DJ
• TJ: Total Jitter (Convolution of RJ &
DJ)
Unbounded (RMS)
RJ
PJ DCD ISI
• RJ: Random Jitter (rms)
• DJ: Deterministic Jitter (p-p)
¾
PJ: Correlated &
uncorrelated Periodic Jitter
due to cross-talk and EMI
¾
DCD: Duty Cycle Distortion
due to threshold offsets and
slew rate mismatches
¾
ISI: Inter-Symbol Interference
due to BW limitation and
reflections
Page 85
Where Does Jitter Come From?
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Transmitter
Media
Receiver
•Lossy interconnect (ISI)
•Impedance mismatches (ISI)
•Crosstalk (PJ)
•Thermal Noise (RJ)
•Voltage Offsets (DCD)
•Power Supply Noise (RJ, PJ)
•On chip coupling (PJ)
•Termination Errors (ISI)
•Thermal Noise (RJ)
•Incorrect Threshold (DCD)
•Power Supply Noise (RJ, PJ)
•On chip coupling (PJ)
Page 86
Into this…
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Page 87
Questions and Answers
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Page 88