Post on 17-Dec-2015
1
Important Characteristics of Important Characteristics of Digital OscilloscopesDigital Oscilloscopes
andand
RADAR Pulse Measurements RADAR Pulse Measurements with Digital Oscilloscopeswith Digital Oscilloscopes
Important Characteristics of Important Characteristics of Digital OscilloscopesDigital Oscilloscopes
andand
RADAR Pulse Measurements RADAR Pulse Measurements with Digital Oscilloscopeswith Digital Oscilloscopes
5:30 – 6:00 Pizza and Refreshments6:00 – 7:00 Technical Presentation
This is a FREE event. Non-Members Welcome!
and Southeastern Michigan present…
Vince Woerdeman, Agilent Technologies
Marty Gubow, Agilent Technologies
Click to edit Master subtitle style
Page 2
AgendaAgenda
Evaluating a Scope’s Performance Characteristics What Bandwidth is needed? What Sample Rate is needed? How does Nyquist’s Theorem and
aliasing apply to oscilloscopes? Acquisition Errors and Interleave
Distortion What are other important
characteristics?
Click to edit Master subtitle style
Page 3
Evaluating Performance CharacteristicsEvaluating Performance Characteristics
Is Full Scope Functionality Retained?
Required Number of Channels?
Required Bandwidth/Acquisition Performance?
Waveform Update Rate, Decode Update Rate, Probing, Ease-of-use, Display Quality, Triggering, etc.?
Click to edit Master subtitle style
Page 4
“Rule-of-thumb” Bandwidth Suggestion“Rule-of-thumb” Bandwidth Suggestion
Suggested Bandwidth = 5X Highest Clock Rate
Allows capture of the 5th harmonic with minimum attenuation.
Scope Bandwidth
Click to edit Master subtitle style
Page 5
Accurate Bandwidth DeterminationAccurate Bandwidth Determination
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
Gaussian Response
Maximally-flat Response
20% BW = 1.0 X fKnee 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.
Step #1: Determine fastest rise/fall times of device-under-test.
Source: Dr. Howard W. Johnson, “High-speed Digital Design – A Handbook of Black Magic”
Click to edit Master subtitle style
Page 6
System Bandwidth CalculationSystem Bandwidth Calculation
fKnee = (0.5/500ps) = 1GHz
3% Accuracy: Scope Bandwidth = 1.9 x 1GHz = 1.9GHz
20% Accuracy: Scope Bandwidth = 1.0 x 1GHz = 1.0GHz
Example
Determine the minimum required bandwidth of an oscilloscope with an approximate Gaussian frequency response to measure a 500ps rise-time (10-90%):
3% Accuracy: Scope Bandwidth = 1.4 x 1GHz = 1.4GHz
Click to edit Master subtitle style
Page 7
Analog Bandwidth ComparisonsAnalog Bandwidth Comparisons
What does a 100 MHz clock signal really look like?
100MHz Scope
Rise Time = 2.5ns500MHzScope
Rise Time = 750ps
1GHzScope
Rise Time = 550ps2GHzScope
Rise Time = 495ps
Click to edit Master subtitle style
Page 8
How Much Sample Rate is Required?How Much Sample Rate is Required?
The truth lies somewhere in between!
Engineer Fred has total trust in Dr. Nyquist and says:
“2X over the scope’s bandwidth.”
Engineer Betty doesn’t trust Dr. Nyquist and says:
“10X to 20X over the scope’s bandwidth.”
Click to edit Master subtitle style
Page 9
Nyquist’s Sampling TheoremNyquist’s Sampling Theorem
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
Click to edit Master subtitle style
Page 10
Nyquist’s Basic Rules…Nyquist’s Basic Rules…
1.fMAX < fS/2
The highest frequency sampled MUST be less than fS/2…
This is NOT the same as oscilloscope bandwidth.
2.Samples MUST be equally spaced
The forgotten rule!
But not-so-simple for DSO technologyBut not-so-simple for DSO technology
Click to edit Master subtitle style
Page 11
Ideal Brick-wall Response w/ BW @ Nyquist (fN)Ideal Brick-wall Response w/ BW @ Nyquist (fN)
fSfN
-3dB
Frequency
0dB
Att
en
uat
ion
Click to edit Master subtitle style
Page 12
Gaussian Response w/ BW @ fS/2 (fN)Gaussian Response w/ BW @ fS/2 (fN)
Frequency
-3dB
Att
en
uat
ion
0dB
fN fS
Aliased Frequency Components
Click to edit Master subtitle style
Page 13
500MHz scope sampling @ 1GSa/s (BW = fS/2 = fN)500MHz scope sampling @ 1GSa/s (BW = fS/2 = fN)
Click to edit Master subtitle style
Page 14
Frequency
-3dB
Att
en
uat
ion
0dB
fN fS fS/4
Gaussian Response w/ BW @ fS/4 (fN/2)Gaussian Response w/ BW @ fS/4 (fN/2)
fS/2.5
Maximally-Flat Response w/ BW @ fS/2.5 (fN/1.25)Maximally-Flat Response w/ BW @ fS/2.5 (fN/1.25)Gaussian Response w/ BW @ fS/2 (fN)Gaussian Response w/ BW @ fS/2 (fN)
Aliased Frequency Components
Aliased Frequency Components
Click to edit Master subtitle style
Page 15
500-MHz scope (2 GSa/s vs. 4 GSa/s)500-MHz scope (2 GSa/s vs. 4 GSa/s)
2 GSa/s (fBW = fS/4 = fN/2)
4 GSa/s (fBW = fS/8 = fN/4)
Input = 100 MHz clock with 1 ns edge speeds
Click to edit Master subtitle style
Page 16
6-GHz scope (20 GSa/s vs. 40 GSa/s)6-GHz scope (20 GSa/s vs. 40 GSa/s)
20 GSa/s (fBW = fS/3.3)
40 GSa/s (fBW = fS/6.6)
Input = 1.25 GHz clock with 100 ps edge speeds
Click to edit Master subtitle style
Page 17
Complying with Nyquist’s Rule #1 (fS > 2 x fMAX)Complying with Nyquist’s Rule #1 (fS > 2 x fMAX)
2X sampling violates Rule #1
2.5X to 5X sampling sufficiently satisfies Rule #1
> 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”
Click to edit Master subtitle style
Page 18
Real-time Non-interleaved ADC SystemReal-time Non-interleaved ADC System
ADC #1 ACQMEM
SampleClock
To CPUInput
AnalogAmplifier
Click to edit Master subtitle style
Page 19
Sample Rate > 4 x fBW (Non-interleaved)Sample Rate > 4 x fBW (Non-interleaved)
Sample Clock
= Input Signal
= Sample Clock
= Sin(x)/x Interpolated Waveform
= Real-time Digitized Point
Sin(x)/x Interpolated WaveformInput Signal
Click to edit Master subtitle style
Page 20
Real-time Interleaved ADC SystemReal-time Interleaved ADC System
ADC #1 ACQMEM
SampleClock
To CPU
AnalogAmplifier
ADC #2 ACQMEM
½ ClockDelay
Input
To CPU
Input
Accurate ADC interleaving requires:
1. Matched vertical response of each ADC
2. Precise phased-delayed clocking
Click to edit Master subtitle style
Page 21
SR > 8 x fBW (Perfectly Interleaved)SR > 8 x fBW (Perfectly Interleaved)
Clock #1
Clock #2
= Input Signal
= Sample Clock
= Sin(x)/x Interpolated Waveform
= Real-time Digitized Point
Sin(x)/x Interpolated WaveformInput Signal
Click to edit Master subtitle style
Page 22
SR > 8 x fBW (Poorly Interleaved)SR > 8 x fBW (Poorly Interleaved)
Clock #1
Clock #2
= Input Signal
= Sample Clock
= Sin(x)/x Interpolated Waveform
= Real-time Digitized Point
Sin(x)/x Interpolated WaveformInput Signal
Click to edit Master subtitle style
Page 23
Testing for Interleave DistortionTesting for Interleave Distortion
1. Effective bits analysis using sine waves
2. Visual sine wave test
3. Spectrum analysis
4. Measurement stability/repeatability
Interleave distortion violates Nyquist’s Rule #2:
“Samples must be evenly spaced”
Click to edit Master subtitle style
Page 24
1-GHz Sine Wave on 1-GHz BW Scopes1-GHz Sine Wave on 1-GHz BW Scopes4 GSa/s (non-interleaved)4 GSa/s (non-interleaved)
20 GSa/s (interleaved)20 GSa/s (interleaved)
4 GSa/s produces superior results compared to 20 GSa/s
Interleave Distortion
Click to edit Master subtitle style
Page 25
2.5-GHz Sine Wave on a 3-GHz Scope2.5-GHz Sine Wave on a 3-GHz Scope20 GSa/s (Single-chip ADC)20 GSa/s (Single-chip ADC)
40 GSa/s (Dual-interleaved ADC chip-set)40 GSa/s (Dual-interleaved ADC chip-set)
Precision ADC interleaving technology produces improved measurements
Vp-p (σ) = 2.4 mV
Vp-p (σ) = 1.8 mV
Click to edit Master subtitle style
Page 26
Interleave Sampling Distortion
2.5-GHz Sine Wave on a 2.5-GHz Scope2.5-GHz Sine Wave on a 2.5-GHz Scope10 GSa/s (Single-chip ADC)10 GSa/s (Single-chip ADC)
Poor ADC interleaving technology produces degraded measurements
40 GSa/s (Quad-interleaved ADC chip-set)40 GSa/s (Quad-interleaved ADC chip-set)
Vp-p (σ) = 9.1 mV
Vp-p (σ) = 12.0 mV
Click to edit Master subtitle style
Page 27
FFT Analysis of 2.5-GHz Sine Wave at 40 GSa/sFFT Analysis of 2.5-GHz Sine Wave at 40 GSa/s
3-GHz Scope3-GHz Scope
2.5-GHz Scope2.5-GHz Scope
10-GSa/s Distortion (-32 dB)40-GSa/s Distortion
Click to edit Master subtitle style
Page 28
400-MHz Clock Sampled @ 40 GSa/s400-MHz Clock Sampled @ 40 GSa/s
3-GHz Scope3-GHz Scope
2.5-GHz Scope2.5-GHz Scope
Rise Time (avg.) = 254psRise Time (range) = 60psRise Time (σ) = 10ps
Rise Time (avg.) = 250psRise Time (range) = 35psRise Time (σ) = 3.3ps
Click to edit Master subtitle style
Page 29
FFT Analysis of 400-MHz Clock at 40 GSa/sFFT Analysis of 400-MHz Clock at 40 GSa/s
3-GHz Scope3-GHz Scope
2.5-GHz Scope2.5-GHz Scope
40-GSa/s Distortion10-GSa/s Distortion
(27 dB below 5th harmonic)
Click to edit Master subtitle style
Page 30
Other Oscilloscope Characteristics to ConsiderOther Oscilloscope Characteristics to Consider
Waveform Update Rate
Advance Analysis
Display Quality
Ease-of-use
Probing
Price
Click to edit Master subtitle style
Page 31
InfiniiMax Active Probe ExtensionInfiniiMax Active Probe Extension
Allows for environmental chamber testing up 105 degrees C.
Click to edit Master subtitle style
Page 32
Questions and AnswersQuestions and Answers
33
Oscilloscope Radar
Measurement Basics
Click to edit Master subtitle style
Page 34
AgendaAgenda
• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 35
Introduction
Radar Measurement Basics
Click to edit Master subtitle style
Page 36
Some Typical Radar ApplicationsSome Typical Radar Applications
• Surveillance
• Search and track
• Fire control
• Navigation
• Missile guidance
• Proximity fuses
• Altimeter
• Terrain avoidance
• Weather mapping
• Space
Radar Measurement Basics
Click to edit Master subtitle style
Page 37
The Wide Range of Measurement RequirementsThe Wide Range of Measurement Requirements
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)
Radar Measurement Basics
Click to edit Master subtitle style
Page 38
Simplified Pulse Doppler Radar Block DiagramSimplified Pulse Doppler Radar Block Diagram
PRFGENERATOR
DISPLAY
ADC S/H LPFVIDEO
AMP
COHO LIMITER LPF
ADC S/H LPF VIDEOAMP
0
SPLITTER
o
2ndIFA
IFBPF
2nd
L.O.
1stIFA
IFBPF
LNA
STALO
COHO BPF AMPRFBPF
Doppler
and
Range
FFT
Processor
PREDRIVERAMP
PULSEDPOWER
TRANSMITTER
DUPLEXER
Transmitter/Exciter
Receiver/Signal Processor
Antenna
90o
PULSEMODULATOR
RECEIVERPROTECTION
FREQUENCYAGILE L.O.
Radar Measurement Basics
Click to edit Master subtitle style
Page 39
Active Electronically Steered AntennaActive Electronically Steered Antenna
Transceiver
Wave Front
Radar Measurement Basics
Animation
Click to edit Master subtitle style
Page 40
Click to edit Master subtitle style
Page 41
Click to edit Master subtitle style
Page 42
AgendaAgenda
• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Jitter Measurements
• Time Domain Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 43
Pulsed Power and Power Spectrum Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 44
Why Measure Power?Why Measure Power?
• High peak power influences the expense of the system
R
$ $
Modulator,PFN, etc.
OutputStage
• Power determines the absolute range
RPt
4
Radar Measurement Basics
Click to edit Master subtitle style
Page 45
Instruments Used to Measure PowerInstruments Used to Measure Power
• Vector Signal Analyzer
• Spectrum Analyzer
• Power Meter
Radar Measurement Basics
Click to edit Master subtitle style
Page 46
AgendaAgenda
• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 47
Noise FigureNoise Figure
-the degradation in the signal-to-noise ratio as the signal passes through the network
Noise Figure, F =
SN in
SN out
(S/N)in
(S/N)out
T = 290°K
Radar Measurement Basics
G
Click to edit Master subtitle style
Page 48
N8975A Noise Figure AnalyzerN8975A Noise Figure Analyzer
• 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)
Radar Measurement Basics
Click to edit Master subtitle style
Page 49
AgendaAgenda
• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Jitter Measurements
• Time Domain Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 50
Component Test
Radar Measurement Basics
Click to edit Master subtitle style
Page 51
Why make Network Analyzer measurements on a RadarWhy make Network Analyzer measurements on a Radar
• 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)
Radar Measurement Basics
Click to edit Master subtitle style
Page 52
The Need for Both Magnitude and PhaseThe Need for Both Magnitude and Phase
4. Time-domain characterization
Mag
Time
5. Vector-error correction
Error
MeasuredActual
2. Complex impedance needed to design matching circuits
3. Complex values
needed for device modeling
1. Complete characterization of linear networks
High-frequency transistor model
Collector
Base
Emitter
S21
S12
S11 S22
Radar Measurement Basics
Click to edit Master subtitle style
Page 53
PNA Performance Network Analyzer FamilyPNA Performance Network Analyzer Family
• Up to 35 s/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 calibration
Radar Measurement Basics
Click to edit Master subtitle style
Page 54
AgendaAgenda
• Introduction
• Pulsed Power and Power Spectrum
Measurements
• Noise Measurements
• Component Measurements
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Jitter Measurements
• Time Domain Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 55
Evaluating I/QDemodulator Errors
Radar Measurement Basics
Click to edit Master subtitle style
Page 56
•Magnitude is an absolute value•Phase is relative to a reference signal
Phase
Ma
g
0 deg
Polar Display -- Magnitude and Phase Represented TogetherPolar Display -- Magnitude and Phase Represented Together
Radar Measurement Basics
Animation
Click to edit Master subtitle style
Page 57
Magnitude Change Phase Change
Frequency ChangeBoth Change
0 deg
0 deg
Phase
Mag
0 deg 0 degPhase
Signal Changes or ModificationsSignal Changes or Modifications
Radar Measurement Basics
Click to edit Master subtitle style
Page 58
89640 Vector Signal Analyzer89640 Vector Signal Analyzer
• Tuners covering dc to 6.0 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).
Radar Measurement Basics
Click to edit Master subtitle style
Page 59
PSG Performance Signal Generator FamilyPSG Performance Signal Generator Family
• 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
Radar Measurement Basics
Click to edit Master subtitle style
Page 60
AgendaAgenda
Radar Measurement Basics
• Introduction
• Power Measurements
• Noise Measurements
• Component Test
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Click to edit Master subtitle style
Page 61
Pulsed ComponentMeasurements
AgendaAgenda
Radar Measurement Basics
Click to edit Master subtitle style
Page 62
Pulsed Transfer Functions in the Time DomainPulsed Transfer Functions in the Time Domain
Amplifier
Radar Measurement Basics
Click to edit Master subtitle style
Page 63
AgendaAgenda
Radar Measurement Basics
• Introduction
• Power Measurements
• Noise Measurements
• Component Test
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Click to edit Master subtitle style
Page 64
Time Domain Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 65
Why Measure Pulse Parameters?Why Measure Pulse Parameters?
PW determines resolving ability (small is better) -- BW ~ 1 / PW
PW affects average power (absolute range, large is better)
Unintentional AM and fast risetimes can reduce the life expectancy
PRI determines unambiguous range
of transmitter
R=P G G
P (4 )3
r
t t r
2
4
• PW determines resolving ability (small is better) - BW ~ 1/PW
• PW affects average power (absolute range, large is better)
• Unintentional AM and fast rise times can reduce the life expectancy of transmitter
• PRI determines unambiguous range
PW determines resolving ability (small is better) -- BW ~ 1 / PW
PW affects average power (absolute range, large is better)
Unintentional AM and fast risetimes can reduce the life expectancy
PRI determines unambiguous range
of transmitter
R=P G G
P (4 )3
r
t t r
2
4
Radar Measurement Basics
Click to edit Master subtitle style
Page 66
What are Important Pulse Parameters?What are Important Pulse Parameters?
Pulse RepetitionInterval (PRI),
PulseWidth
Risetime Falltime
Also: Duty Cycle
Pulse Shape (over and preshoot, droop)
Pulse Width Stability
PRI Stability
PulseOff Time
1
PRF
• Duty cycle
• Pulse shape (over and pre-shoot, droop)
• Pulse width stability
• PRI stability
Also:
Radar Measurement Basics
Click to edit Master subtitle style
Page 67
Definition of Pulse WidthDefinition of Pulse Width
Average Power During On-time of Pulse
-6dB
Pulse Width
Pulse Repetition Interval
Radar Measurement Basics
Click to edit Master subtitle style
Page 68
Time Domain MeasurementsTime Domain Measurements
Envelop parameters
• Rise time
• Fall time
• Pulse width
• Period
• On/off ratio
Modulation in the pulse
• Unintentional
- AM to PM
- Phase noise
• Intentional
- Chirp
- Barker coding
- Frequency agility
Radar Measurement Basics
Click to edit Master subtitle style
Page 69
Measuring with a Digital OscilloscopeMeasuring with a Digital Oscilloscope
Advantages
• General measurement tool
• Wide bandwidth
• Easy to understand
• Option to post process signal
Considerations
• Aliasing
• Dynamic range
• Flatness
• Memory depth
Radar Measurement Basics
Click to edit Master subtitle style
Page 70
Time Domain MeasurementsTime Domain Measurements
PRFGENERATOR
DISPLAY
ADC S/H LPFVIDEO
AMP
COHO LIMITER LPF
ADC S/H LPF VIDEOAMP
0
SPLITTER
o
2ndIFA
IFBPF
2nd
L.O.
1stIFA
IFBPF
LNA
STALO
COHO BPF AMPRFBPF
Doppler
and
Range
FFT
Processor
PREDRIVERAMP
PULSEDPOWER
TRANSMITTER
DUPLEXER
Transmitter/Exciter
Receiver/Signal Processor
Antenna
90o
PULSEMODULATOR
RECEIVERPROTECTION
FREQUENCYAGILE L.O.
Radar Measurement Basics
Click to edit Master subtitle style
Page 71
Infiniium OscilloscopeInfiniium Oscilloscope
• 4 channels
• Up to 64 MB deep memory
• Up to 40 GSa/s sample rate/channel
• Infiniium award-winning usability
• Full upgradeability
Radar Measurement Basics
Click to edit Master subtitle style
Page 72
AgendaAgenda
Radar Measurement Basics
• Introduction
• Power Measurements
• Noise Measurements
• Component Test
• Evaluating I/Q Demodulator Errors
• Pulsed Component Measurements
• Time Domain Measurements
• Jitter Measurements
Click to edit Master subtitle style
Page 73
Jitter Measurements
Radar Measurement Basics
Click to edit Master subtitle style
Page 74
What is Jitter?What is Jitter?
Threshold
Threshold
Threshold
Jitter
Noise
-creates ambiguity in threshold crossing
(a)
(b)
(c)
Radar Measurement Basics
Click to edit Master subtitle style
Page 75
Jitter FunctionJitter Function
t1 t2t3
t4 t5
Ideal PulseTrain
Jitter signal viewed atinstants in time
Jitter magnitudeJitter function
Radar Measurement Basics
Click to edit Master subtitle style
Page 76
What is Jitter? What is Jitter?
Ideal clock:
Jittered clock:
)2sin( tfc
)2sin(2sin 101
34 tftf cc
)2sin(101
34 tfcJitter:
UI32
• Jitter is the deviation of a timing event of a signal from its ideal position.
• This is the traditional description of jitter,
• commonly referred to Time Interval Error (TIE), or phase jitter.
Click to edit Master subtitle style
Page 77
Radar Jitter MeasurementRadar Jitter Measurement
PULSEDPULSEDRADARRADAR
JitterSource
Pulse Envelope
Trigger
Ch1
DigitizingOscilloscope
PRI Reference
Crystal Detector
Radar Measurement Basics
Click to edit Master subtitle style
Page 78
Time Interval vs. Time ProfileTime Interval vs. Time Profile
Time Interval
Time
Jitter Periodic Rate
17.9 KHz
3.8 ns
Peak-to-Peak Jitter Amplitude
Radar Measurement Basics
Click to edit Master subtitle style
Page 79
Histogram of Clock PeriodHistogram of Clock Period
Peak-to-Peak
% Probability
Period
Probability Analysis
Jitter Distribution
- +MEANMIN MAX
Radar Measurement Basics
Click to edit Master subtitle style
Page 80
Histogram of Edge JitterHistogram of Edge Jitter
Click to edit Master subtitle style
Page 81
“Real World” Jitter is Complex
Random Jitter (RJ) is unbounded• Due to thermal noise, shot
noise, etc.• Follows Gaussian distribution• Requires statistical analysis
to be quantified• RJpp = 14.1 x Jrms for 10-12
BER
Deterministic Jitter (DJ) is bounded and composed of:• Duty-Cycle-Distortion (DCD)• Inter Symbol Interference
(ISI)• Periodic Jitter (PJ) RJ
DJ
Jitter is composed of random and deterministic
components
Click to edit Master subtitle style
Page 82
Jitter Probability: BERJitter Probability: BER
randomticdeterminispkpk nJJ
=
Click to edit Master subtitle style
Page 83
How Do Real Time Scopes Measure Jitter on Data? How Do Real Time Scopes Measure Jitter on Data?
Jitter Trend
NRZ Serial Data
Recovered Clock
Jitter Spectrum
Units in Time
Units in Time
Jitter Histogram
Click to edit Master subtitle style
Page 84
Agilent EZJIT Jitter Measurement ApplicationAgilent EZJIT Jitter Measurement Application
Signal
Trend
Histogram
Spectrum
Click to edit Master subtitle style
Page 85
Total Jitter ComponentsTotal Jitter Components
• TJ: Total Jitter (Convolution of RJ & DJ)
• RJ: Random Jitter (rms)
• DJ: Deterministic Jitter (p-p)
PJ: Correlated & uncorrelated Periodic Jitter due to cross-talk and EMI
DCD: Duty Cycle Distortion due to threshold offsets and slew rate mismatches
ISI: Inter-Symbol Interference due to BW limitation and reflections
TJ
RJDJ
PJ DCD ISI
Unbounded (RMS)Bounded (p-p)
Click to edit Master subtitle style
Page 86
Where Does Jitter Come From?Where Does Jitter Come From?
Transmitter Receiver
•Thermal Noise (RJ)•Voltage Offsets (DCD)•Power Supply Noise (RJ, PJ)•On chip coupling (PJ)
•Lossy interconnect (ISI)•Impedance mismatches (ISI)•Crosstalk (PJ)
•Termination Errors (ISI)•Thermal Noise (RJ)•Incorrect Threshold (DCD)•Power Supply Noise (RJ, PJ)•On chip coupling (PJ)
Media
Click to edit Master subtitle style
Page 87
Into this…Into this…
Click to edit Master subtitle style
Page 88
Questions and AnswersQuestions and Answers