Overcome High-Speed Analog Measurement Challenges

8/13/2019 Overcome High-Speed Analog Measurement Challenges

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Overcome High-Speed Analog

Measurement ChallengesPresenter


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Agenda

High-Speed Test Challenges

Oscilloscope/Digitizer Performance Requirements

Automated Test Challenges Addressing Automated Test Challenges With the

Industrys Highest Performance PXI Digitizers


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There are two kinds of designers . . .

those that have signal integrity problems

. . . and those that will.

Sun Microsystems


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Source: EE Times survey

Signal integrity is criticalCircuit board traces become transmission lines

Impedance discontinuities along the signal path:

Create reflections Degrade signal edges

Increase crosstalk

EMI goes up Ground bounce increases with highercurrent


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What Is Signal Integrity?

A digital signal with good integrity has: Clean, fast transitions Stable, valid logic levels

Accurate placement in time

Free of transients

The term integrity means complete and unimpaired.


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Measuring Signal Integrity

Visual tool to observe signalintegrity on a clocked bus, usuallymeasured using anoscilloscope/digitizer

Overlays waveform traces frommany successive unit intervals

Signal integrity factors causeblur:

Jitter (horizontal) Noise (vertical)

Eye Diagram


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Oscilloscopes/Digitizers Provide Insight

Into the Analog Domain

Displays waveform details,edges, and noise

Detects and displays transients

Precisely measures timingrelationships


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Oscilloscope/Digitizer

Performance Requirements


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Signal Integrity Versus Signal Fidelity

Signal integrity: Is my circuit operating as expected?

Signal fidelity: Can I trust my measurement system to

give an accurate representation of my signal?

How do you know if your measurement setupprovides good signal fidelity?


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Measurement Bandwidth

Oscilloscope Bandwidth Must have sufficient

bandwidth to capture high-

frequency components

Bandwidth specified at -3 dBpoint

The 5 Times Rule

For less than2 percent

measurement error

Bandwidth 5thHarmonic>


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Sample Rate

Sample Rate Determines how frequently an

oscilloscope takes a sample

Faster sample rate, greaterresolution and waveform detail

Wider margins in production testmay demand less oversampling

Required Sample RateSample

Rate 2.5 X fHighest>For sin(x)/x interpolation

Sample

Rate 10 X fHighest>For linear interpolation


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Vertical Resolution

Vertical resolutionrefers to how manydifferent voltagechanges you canmeasure

100 200150500

Time (ms)

0

1.25

5.00

2.50

3.75

6.25

7.50

8.75

10.00

Amplitude (V)

16-bit resolution

3-bit resolution

000

001

010

011

100

101

110

111

| ||||

However

vertical resolution alone doesnt tell the whole story!


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Characterizing Acquisition Performance

Sources of rrorDifferential Nonlinearity

Integral NonlinearityMissing Codes

Aperture Uncertainty

Noise

How do we characterizethe impact of theseerror sources?


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Effective Number of Bits (ENOB)

Characterizes how closely a digitized waveform actuallyrepresents the analog input signal

Higher effectivenumber of bitsprovides better

voltageresolution


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ENOB: Figure of Merit for High-Speed Digitizers

Why use ENOB?

Accounts for all of the following error sources:

Differential nonlinearity

Integral nonlinearity

Missing codesAperture uncertainty

Noise

Indicates the impact of noise and distortion sources

across signal frequencies

ENOB typically degrades with increasing signal

frequency


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Value of Looking Into ENOB

NI PXIe-5185/86 Digitizer A Digitizer B

Analog Bandwidth 3 GHz and 5 GHz 3 GHz 1.5 GHz

Sample Rate 12.5 GS/s 8 GS/s 4 GS/s

Vertical Resolution 8-bit ADC 10-bit ADC 10-bit ADC

Which would you expect to provide better vertical resolution?

Sampling Jitter 500 fs RMS 1200 fs RMS 1200 fs RMS

RMS Noise 0.35% full scale Not specified 0.5% full scale

ENOB6 bits at 2.5 GHz

5.5 bits at 5 GHz

4.5 bits at 1.8

GHz

Not specified

above 410 MHz

Form Factor 3U PXI Express 6U CompactPCI 3U PXI


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ENOB for High Speed Measurements

Input the same 5 Gbit/s signalto both instruments

High ENOB translates intomore margin and better

repeatability!

Measurement Vendor T Vendor A

TIE Jitter 3.08 ps 11.4 ps

Eye Height 582 mV 521 mV


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Automated Test Challenges


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A digitizer providesfeatures optimized forautomated test

Test Throughout the Development Cycle

Production

TestValidationR&D

OscilloscopesQuick Visualization

Interactive Use

High Bandwidth

Modular DigitizersHigh Throughput

Integration

Compact Size

Very High Bandwidth (multi-GHz)

Customized measurements

Hybrid

Systems

The digitizing oscilloscopeprovides insight into theanalog domain


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Automated Test Challenges

System IntegrationCombining driver software from multiple

vendorsSharing of clocks and triggersFuture-proofing for upgraded capabilitySynchronizing channels in large systems

Reduced Test Times Peripheral buses not optimized for throughput

or latency

Limited Rack Space Stand-alone oscilloscopes can consume 7U to 8U

of rack space

Power Constraints


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Addressing Automated Test Challenges With the



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NI PXIe-5185 NI PXIe-5186Bandwidth 3 GHz 5 GHz

Sample Rate12.5 GS/s (1 ch)

6.25 GS/s (2 ch)

Channels 2

Vertical Resolution 8-Bit ADC

Data Throughput >700 MB/s

Form Factor 3-Slot, 3U PXI Express

CodevelopedbyNI and Tektronix


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Superior Acquisition Performance

State-of-the-art SiGe analog-to-digital converters and front-

end ASICs designed by Tektronix, manufactured by IBM

Same core technology is deployed across Tektronix

oscilloscopes offering

Tektronix, Enabling Technology is a trademark of Tektronix, Inc.


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NI PXIe-5185/86: Optimized for Automated Test

Simplified System IntegrationNI-SCOPE driver for all NI digitizersShare triggers using the matched trigger lines of the PXI

backplaneSupport for all popular application development environmentsMultimodule synchronization at 80 ps resolution over PXI

backplane Reduced Test Times

Data throughput rates >700 MB/s

Smallest Footprint Fit 10 channels in a single chassis

Minimal Power Consumption 45 W/ch power consumption (90 W per module)


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Reduce Test Times With PXI Express

Block

Size

NI PXIe-5186/5185

Digitizers

LXI GigabitEthernet

Oscilloscope

Test Time

Reduction

1 MB 496 MB/s 12.6 MB/s 39.4x

16 MB 700 MB/s 19.7 MB/s 35.5x33 MB 738 MB/s 20.3 MB/s 36.4x

Why the difference?


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Rack Space

1,951 in3

Power Consumption: 375 W

104 in3


Digital multimeter, battery simulator,signal generator, spectrum

analyzer, digitizer, switch, digital

I/O, coprocessor, RF transceiver,

embedded PC

4U Rack Height

Power Consumption: 790 W8U Rack Height



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Custom Measurements

NI LabVIEW Toolkits

Processing

Jitter Analysis Signal Processing Digital Filter Design Modulation Spectral Meas.

Upgrade to the latestprocessor technology

using embedded

controllers

Take advantage of

multicore processors

with LabVIEW

Perform inlineprocessing with

NI FlexRIO and

LabVIEW FPGA


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Summary

For high-speed digitizers, ENOB offers the best figure

of merit for comparing noise performance

Tektronix, Enabling Technology in the

NI PXIe-5185/86 delivers superior signal fidelity with

low noise and high ENOB

NI PXIe-5185/86 modules are optimized for automated

test

Tektronix, Enabling Technology is a trademark of Tektronix, Inc.


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For More Information

For NI PXIe-5185/86 product information, visit

ni.com/high-speed-digitizer.

To learn more about PXI and its benefits for

automated test, visit ni.com/automatedtest.
http://www.ni.com/high-speed-digitizerhttp://www.ni.com/automatedtesthttp://www.ni.com/automatedtesthttp://www.ni.com/high-speed-digitizerhttp://www.ni.com/high-speed-digitizerhttp://www.ni.com/high-speed-digitizerhttp://www.ni.com/high-speed-digitizerhttp://www.ni.com/high-speed-digitizer


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Overcome High-Speed Analog Measurement Challenges