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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

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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

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Analog Oscilloscope

Attenuator

Input signalDisplay

Vert AmpAmplifier

Horz AmpTrigger

Real-time scope Vs Sampling scope

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Real-time DSO

Sampling Oscilloscope

Attenuator

Amplifier

Input signal

Input signal

Memory

Sample and Hold

A/D

A/D

Amplifier

Memory

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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

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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

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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

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Nyquist and sampling rate 2

4 samples

More sample points retains signal quality and avoids aliasing of the signal

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Nyquist and sampling rate 3

7 samples

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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

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PicoScopePicoScope 9201A9201A

andand

Picoscope 9211A Picoscope 9211A (TDR/TDT)(TDR/TDT)

PicoScope 9000 Block diagram

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Sampling Diodes

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PicoScope 9211A front panel

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Electrical inputsClock recovery trigger

Direct trigger

Prescaled trigger

PicoScope 9211A rear panel

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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

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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

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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

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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

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Applications: LabVIEW, C++, VB

COM Server (ActiveX)

Oscilloscope Controls

USBLAN

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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

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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

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TDR

• Why use TDR

• Predict performance

• Directly measures pulse transmission through a signal

• Path or device with TDT

• Verify performance against standard specification

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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

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… 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

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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

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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)