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Introduction to sampling scopesIntroduction to sampling scopes
©© Copyright 2010, PSECopyright 2010, PSE-- PRIGGEN SPECIAL ELECTRONICPRIGGEN SPECIAL ELECTRONIC
Real-time scope Vs Sampling scope
2
Real-time Oscilloscopes
•Can capture single instantaneous or
repetitive events
•Lower ADC resolution, but high
sample rate increases error
•Long record length
•Advanced triggers to capture
intermittent events
•Serial bus decoding
•Ideal for general use and fault
diagnosis
•Real-time GS/s sampling is
EXPENSIVE
Sampling Oscilloscopes (9000 series)
•Can only capture repetitive
waveforms
•Have lower sample rate to increase
ADC resolution
•Lower noise floor
•Wider bandwidth for lower budget
•Lower intrinsic jitter
•Eye diagrams and mask testing
•Best choice for TDR/TDT
measurement
•Lower cost of ownership
Analog Oscilloscope
3
Analog Oscilloscope
Attenuator
Input signalDisplay
Vert AmpAmplifier
Horz AmpTrigger
Real-time scope Vs Sampling scope
4
Real-time DSO
Sampling Oscilloscope
Attenuator
Amplifier
Input signal
Input signal
Memory
Sample and Hold
A/D
A/D
Amplifier
Memory
5
Analog bandwidth
“Analog bandwidth” is the maximum frequency that can pass through the front end of an oscilloscope
-3 dB
Frequency Hz (log)
Am
plit
ud
e d
B
0 dB
12 GHz
Bandwidth and rise time
• Choose a scope with enough bandwidth for the application:
• Signal transition time
• Signal data rate
• Signal transient time (rise and fall time)
• Effects of too little bandwidth:
• Amplitude and timing errors
• Loss of high frequency aberrations
• Errors in automatic measurements
6
Bandwidth and data rate
• Calculating bandwidth from Data rate:
7t
V
1st harmonic
3rd harmonic
5th harmonic
Application example:PCIe R1.0a has a data rate of 2.5 Gbps (1.25 GHz frequency)
Bandwidth required to see 5 harmonics is 1.25 GHz x 5 = 6.25 GHz
3rd Harmonic = 3 x Bit rate2
5th Harmonic = 5 x Bit rate2
8
Nyquist and sampling rate 1
Analog
signalSampled
signal
2 samples
Sampling is the process of converting an analog signal into a numerical
sequence of digital numbers measured in Samples per Second
Nyquist theorem states that the sample rate must be at least twice
fundamental frequency
9
Nyquist and sampling rate 2
4 samples
More sample points retains signal quality and avoids aliasing of the signal
10
Nyquist and sampling rate 3
7 samples
11
Nyquist and sampling rate 4
15 samples
Sampling methods - Real time
Data points are acquired from a single acquisition to build one screen image
The sample rate is larger than the incoming frequency (Nyquist / Shannon)
Single shot acquisition
Sampling methods – Equivalent time 2
Data points are acquired randomly from many cycles to build one screen image
The sample rate is smaller than the incoming frequency
Random Interleaved Sampling
Sampling methods – Equivalent time 1
Data points are acquired sequentially from many cycles to build one screen image
PicoScope 9000 sample rate is 200 kS/s, bandwidth is 12 GHz
Sequential Sampling – as used with PicoScope 9000
Trigger Point
Trigger-Delay40ns Sample Points
Trigger delay to the first sample point
PicoScope 9000 Applications
SIGNAL ANALYSIS
• Electrical standards compliance testing
• Eye-diagram analysis
• Spectrum analysis• Statistical analysis
SIGNAL ANALYSIS
• Electrical standards compliance testing
• Eye-diagram analysis
• Spectrum analysis• Statistical analysis
R & D
• Microwave & RF characterisation
• High-energy physics
• Digital design• PCB and connector transmission line testing
R & D
• Microwave & RF characterisation
• High-energy physics
• Digital design• PCB and connector transmission line testing
TIMING ANALYSIS
• Automatic parametric measurements
• Pulsed RF switches
• Compliance testing
TIMING ANALYSIS
• Automatic parametric measurements
• Pulsed RF switches
• Compliance testing
HIGH-SPEED DIGITAL COMMUNICATIONS
• Design and verification of telecom and datacoms elements
• Manufacturing and testing for ITU / ANSI conformance
• Crosstalk analysis
• TDR/TDT
HIGH-SPEED DIGITAL COMMUNICATIONS
• Design and verification of telecom and datacoms elements
• Manufacturing and testing for ITU / ANSI conformance
• Crosstalk analysis
• TDR/TDT
SEMICONDUCTOR TESTING
• Microwave & RF characterisation• High-energy physics
• Digital design
• Informative waveform displays
SEMICONDUCTOR TESTING
• Microwave & RF characterisation• High-energy physics
• Digital design
• Informative waveform displays
MANUFACTURING
• Limit and mask testing• Testing for ITU / ANSI conformance
• Automatic test systems
• Auto-calibration routine
MANUFACTURING
• Limit and mask testing• Testing for ITU / ANSI conformance
• Automatic test systems
• Auto-calibration routine
17
PicoScopePicoScope 9201A9201A
andand
Picoscope 9211A Picoscope 9211A (TDR/TDT)(TDR/TDT)
PicoScope 9000 Block diagram
18
Sampling Diodes
19
PicoScope 9211A front panel
20
Electrical inputsClock recovery trigger
Direct trigger
Prescaled trigger
PicoScope 9211A rear panel
21
Multifunction signal
generators
USB Connection
DC Power input
Ethernet Connection
Direct Trigger
PicoScopePicoScope
90009000
Synthesized SW Generator
Power Splitter
The power of wide-bandwidth sampling oscilloscopes is largely useless without fast, low-jitter triggering.
Equipment connections for Direct Trigger Test
Key specifications of Direct Trigger:
� DC to 1 GHz trigger bandwidth� 100 mV p-p DC to 100 MHz, 400 mV p-p at
1 GHz sensitivity� <3.5 ps max RMS jitter
Typical picture of a 1 GHz1 GHz signal using Direct Trigger
HF Prescaled Trigger
The PicoScope 9000 HF (prescaled) trigger is an AC-coupled 10-GHz prescaler for triggering on high-speed data without cumbersome manual adjustment.
The heart of the trigger is a low-noise GaAs frequency divider. Low RMS jitter <3.5 ps typ. is possible.
PicoScopePicoScope
90009000
Synthesized SW Generator
Power Splitter
Equipment connections for prescaled trigger test
A 10 GHz sine-wave signal with prescaled trigger
Clock recovery trigger
Use when the trigger source is an NRZ signal (without a dedicated trigger input) input with a data rate between 12.3 Mbps and 2.3 Gbps
24
PicoScopePicoScope
90009000
Power Splitter
Recovered Clock RMS Trigger Jitter, maximum: 1 ps + 1.0% of Unit Interval
Equipment connections for clock recovery trigger test
Pulse Pattern Generator
A 1.32 Gbps pattern using clock recovery trigger
Pattern sync trigger
25
Use pattern sync menu to provide pattern lock trigger, and generate an eye line.
Pattern Lock Trigger:
…is the ability of the PicoScope9000A to internally generate and lock onto a pattern trigger.
Eye line:
…is used to average eye diagrams and to view specific bit trajectories. The Eye Line mode uses the pattern lock feature to establish a pattern sync trigger and then to use that trigger to walk through each bit of the data pattern
Building an eye diagram
26
The process of building an eye
diagram includes serial acquisitions
of the waveform database
The eye diagram is valuable for giving
a comprehensive view of all signal
integrity faults (except clock jitter):
►Noise
► Jitter
►Reflections
►Ringing
► Inter-symbol interference
►Power and ground coupling
NRZ Eye Diagram Measurements
The PicoScope 9000 quickly measures 42 fundamental parameters used to characterise non-return-to-zero (NRZ) signals. Up to four parameters can be measured simultaneously.
The PicoScope 9000 displaying 4 automatic measurements on a 2.5-Gbit NRZ eye diagram
Examples of NRZ Measurements
Measurement of 622-Mbit eye diagram
Measurement of 1.25-Gbit eye diagram
Measurement of 2.5-Gbit eye diagram
RZ Eye Diagram Analysis
The PicoScope 9000 quickly measures 43 fundamental parameters used to characterise return-to-zero (RZ) signals. Up to four parameters can be measured simultaneously.
The PicoScope 9000 measuring a 139-Mbit RZ eye diagram
Mask Test
For eye-diagram masks, such as those specified by the SONET and SDH standards, the PicoScope 9000 supports on-board mask drawing for visual comparison. The display can create grey-scaled or colour-graded displays to aid in analysing noise and jitter in eye-diagrams.
Mask test quickly characterises:
► Noise► Jitter► Aberrations► Rise time► Fall time
The on-board mask drawing capability allows simple, operator-independent visual comparison of signal with standard mask.
SONET/SDH (OC64/STM16)SONET/SDH (OC64/STM16)signal compared with the
standard mask, showing a compliant waveform
Mask Margins
Mask margins are used to determine the margin of compliance for a standard or scaled mask.
The PicoScope 9000 goes beyond basic testing with mask margin analysis for process monitoring.
Mask hits/failures are easily viewed with red pixels
Mask test results show:
► Total waveforms► Failed samples► Mask hits► Mask margin value► Margin hits► Margin hits in polygon
Mask margins are used to determine the margin of compliance for a standard 2.5 Gbps STM16/OC48 eye diagram or scaled mask
Measurements and Tests
Graticule Measurements Marker Measurements Pulse Measurements
NRZ Eye Measurements RZ Eye Measurements Histogram Measurements
Types of Measurements
Types of Measurement Test
Limit Test Mask Test Mask Margin Test
10 by 8 display
graticule with
Grid, Axes,Frame
and Off options
Two X, Y, or XY
markers provide
absolute, delta or ratiometric
measurements
19 Amplitude, 29
Timing and 5 FFT measurements can be
performed
automatically
Measurement list
includes 42 NRZ
eye parameters
43 automatic
measurements are built for
characterisation
of RZ signals
Up to 15 statistical
measurements ofvertical and horizontal
histograms
Allows you to
automatically compare up to 4
measurement results
with pass or fail limits
Standard, auto
or custom masks can be used for
mask test
Test is used to
determine the margin
of compliance for a standard or scaled
mask
Programming the scope
33
Applications: LabVIEW, C++, VB
COM Server (ActiveX)
Oscilloscope Controls
USBLAN
34
TDRTDR
TDR
• What is TDR
• Time Domain Reflectometry
• Visualizes and measures the reflections of
• electrical energy by a circuit (PCB, cable, IC package)
• Like a radar ,but with probes connected directly
To the circuit
Impedance mismatches are observed
35
TDR
• TDR is the most straight forward way to
measure characteristic impedance
PCB Lines
Cables
Multiple-chip modules
Find and measure discontinuities or variations in impedance
In Connectors
Corners and vias on PCB
Transitions from connectors to PCB
36
TDR
• Why use TDR
• Predict performance
• Directly measures pulse transmission through a signal
• Path or device with TDT
• Verify performance against standard specification
37
TDR
• Compliance Applications
• Standard committees and trade associations
specify measurements to meet the signal integrity
and interoperability requirements
These specifications are developed for compliance
testing requirements and used to guarantee interoperability
between many vendor devices
38
… The theory …TDR Waveform Characteristics Details
TDR systems observe the superposition of incident and reflected signals at source
Time separation t1-t0 assures ability to discern difference
Timet0 t1
incidentV
reflectedV
Amplitude
… The theory …TDR Units: Rho Units; Z (is non-linear)
1
1refZ Z
ρ
ρ
+=
−
L ref
L ref
Z Z
Z Zρ
−=
+
0 ρ
- 1 ρ
reflected
incident
V
Vρ =
Time
+ 1 ρ
t0 t1
Characteristic (Z = Z0)
Amplitude
incidentV
reflectedV
1 for a Short
1 for an Open
ρ
ρ
= −
=
00 at Z Zρ = =
Measured ρρρρ Calculated ρρρρ Measured Z
TDR/TDT Testing
41
Time Domain Reflectometry (TDR) is a method of characterizing a transmission line or network by sending a signal into one end and measuring the electrical reflections.
A TDR step can also be used to make Time Domain Transmission (TDT) measurements. TDT is a technique that allows you to measure the response of a system by sending steps through a device and monitoring the output of the device.
The measurements are made on signals transmitted through the device, rather than reflections from the device (as in TDR).
An example of Z-profile of transmission line. Both markers provide
distance and Ohm measurements
TDR/TDT applications
42
TDR response from a PCB, showing three vias 5mm apart
Typical applications include:
Impedance
PicoScope 9000 Specifications
VERTICAL► DC to 12 GHz bandwidth► 29.2 ps rise time► Two channels► ±2 % vertical gain accuracy► 16-bit vertical resolution► <2.0 mV RMS noise► ±1 V input range
HORIZONTAL► Dual timebase 10 ps/div to 50 ms/div► ±0.2% ±15 ps time interval accuracy► <200 fs sampling interval► Up to 4 k-point/channel buffer size
OPERATIONAL► Power consumption: 15 W max► Weight: 1 kg ► Size: W170 x H40 x D255 mm
UTILITY► Autoscale► Automatic calibration► Windows XP, Vista and Windows 7► Built-in information system using Windows Help
TRIGGER► DC to 1 GHz full direct trigger► 10 GHz prescaled trigger ► <3.5 ps RMS jitter► 2.7 GHz Clock recovery► Pattern sync trigger
MEASUREMENTS and ANALYSIS► High-resolution cursors, automatic waveform
measurements, statistics and pass / fail limit tests► Waveform processing including FFT with five FFT
windows
TDR/TDT► Two channels► Vertical scales: Volts, Rho (2mrho/div to 2 rho/div),
Ohm (1 ohm/div to 100 ohm/div)► Horizontal scale: Time or distance (Meter, Foot,
inch)► TDR stimulus from internal or external generators
Signal Generators (9211A)► Modes: Step, Coarse timebase, Pulse, NRZ and
RZ► 100 ps risetime (typ) for Step (TDR)