Improved Measurements Overcome High-Speed Interconnect Challenges

1. Improved Measurements Overcome High-Speed Interconnect Challenges October 2013 Bob Buxton EuMW Seminars 2013

2. Agenda • Background • S-parameter measurements - frequency range considerations • Eye Diagrams and low frequency measurement data issues • De-embedding • Correlation – measurements and simulation • Setting emphasis levels • Superposition vs. true mode stimulus for active device measurement • Resources • Questions EuMW Seminars 2013

3. Background – challenge for SI Engineers • Compliance with higher data rate standards • Cost/performance trade-offs • Locating Defects • Measurement – simulation correlation • Dealing with test fixtures EuMW Seminars 2013

4. Challenges for SI Engineers Parallel Data Serial Data 8B/10B Encoder Driver Serializer Equalizer Channel Issues Parallel Data Clock/PLL Data Recovery 10B/8B Decoder De-Serializer Equalizer Jitter and Noise CR/PLL EuMW Seminars 2013

5. Types of Channel EuMW Seminars 2013

6. Channel Issues - Loss Tx Rx EuMW Seminars 2013

7. Channel Issues - Structures Channel artifacts (vias, impedance changes, ground plane issues etc.) EuMW Seminars 2013

8. Backplane Transmission Measurement EuMW Seminars 2013

9. Channel Issues – Crosstalk Tx Tx Tx Rx Rx Rx FEXT NEXT EuMW Seminars 2013

10. Importance of Maximum Frequency Range • Attenuating harmonics distorts signal • Ideally measure to 5th harmonic Harmonic Content of 28 Gbps NRZ clock signal EuMW Seminars 2013

11. High Frequency VNA impact – resolution • Rule of thumb (air dielectric) • Time = 1/BW • Distance (reflect) = 150mm/BW (GHz) • 40 GHz = 3.7 mm • 110 GHz = 1.4 mm • Non-air distance : divide by TWO MISMATCHES SEPARATED By 2 mm (AIR) span resolution 40 GHz 3.75 mm 50 GHz 3.0 mm 60 GHz 2.5 mm EuMW Seminars 2013

12. High Frequency VNA impact - causality • Lack of causality means output appears to occur prior to stimulus • Can cause unstable simulations • Higher frequency data improves causality Non-Causal Results EuMW Seminars 2013

13. Need for Low Frequency Data – 2 Reasons • DC Extrapolation • Sampling in the frequency domain and aliasing* • Max unambiguous time domain result: Tmax= 1/(2fs) • Need to consider multiple reflections * A Reverse Nyquist Approach to Understanding the Importance of Low Frequency Information in Scattering Matrices Daniel Dvorscak and Michael Tsuk, ANSYSInc, DesignCon 2013 EuMW Seminars 2013

14. VNA performance and DC Extrapolation • Series of measurements made on same 40 inch line • VNA 1 • 40 MHz to 40 GHz • Couplers for entire band • VNA 2 • 4 MHz to 40 GHz • Hybrid of bridges and couplers EuMW Seminars 2013

15. VNA performance and DC Extrapolation • DC extrapolation depends on quality of S-parameter measurement • Left trace from VNA limited low frequency performance • Coupler based • 92 dB DR at 40 MHz • Right trace from VNA with better low frequency performance • Bridges at LF • 115 dB DR at 4 MHz EuMW Seminars 2013

16. Impact on step response • Good low start frequency data improves DC extrapolation • Low start frequency sets frequency domain sampling for low pass step response and hence alias free range Aliasing due to 40 MHz sampling Slope due to poor DC extrapolation 40 MHz to 40 GHz data VNA 1 4 MHz to 40 GHz data VNA 2 EuMW Seminars 2013

17. Stability at low frequency also critical Low frequency data issues (drift/instability…) can have an out-sized effect on transformed data because of its criticality to large-distance-scale structure. EuMW Seminars 2013

18. Eye diagrams – 10 Gbit • 10 Gbit • data from VNA 1 • 40 MHz to 40 GHz • 10 Gbit • Data from VNA 2 • 4 MHz to 40 GHz EuMW Seminars 2013

19. Importance of Low Frequency Range • VectorStar displays a flat 25 ohm section as expected • Measured Data range from 25.11 to 25.28 ohms • Low noise on low frequency data give rock-steady results from sweep to sweep • (Composite picture of multiple screen captures showing measurements made on Beatty Standard) EuMW Seminars 2013

20. VectorStar Architecture: Two VNAs in One! > 2.5 GHz High Band MS4640A Block Diagram (Fully Loaded Configuration) optional < 2.5 GHz Low Band a2 a1 a1 a2 b2 b1 b2 b1 Bias 1 Bias 2 Port 2 Port 1 EuMW Seminars 2013

21. Unique Hybrid VNA Architecture • Two VNAs in parallel: Almost the only way to get 6 decades of coverage (from kHz to GHz frequencies) • Each receiver technology (sampler or mixer) used in its best range • Each coupling technology (coupler or bridge) used in its best range • Both share a common IF path and fully synthesized source

22. De-embedding Methods available within VectorStar Best Accuracy Requires good repeatability Backplanes EuMW Seminars 2013

23. Correlation - Measurement and Simulation • Use Channel Modeling Platform • Use time domain equipment to measure Eye and compare with simulated Eye EuMW Seminars 2013

24. Use of Channel Modeling Platform • A set of known structures • Feed data into models • Make measurements • Make comparison EuMW Seminars 2013

25. Correlation – Measurement and Simulation Simulated Using measured S-parameter data Input waveform with no emphasis Tx Rx Measured using Oscilloscope Simulated Using measured S-parameter data Input waveform with emphasis Measured using Oscilloscope EuMW Seminars 2013

26. Setting Ideal Emphasis • Challenge: Difficult to find the ideal emphasis settings from the many possibilities • Problem: Searching for ideal settings while verifying the output waveform • takes an extremely long time • hard to explain why those settings are ideal. • Solution: Use VNA-captured S-parameter data to apply inverse DUT characteristics to input waveform EuMW Seminars 2013

27. Time and Frequency Domain – a merged solution DUT (27inch PCB) Tap Settings EuMW Seminars 2013

28. MS4640B now with: • Option 031 Dual Source Architecture • Option 043 DifferentialViewTM EuMW Seminars 2013

29. VectorStar PROVIDES • Broadest frequency span: 70 kHz to 70/110 GHz • Best time domain analysis capability • Widest range of calibration & de-embedding methods • Upgradeable in frequency range, port count & option additions • Choice of TMS or Superposition Good S-parameter Data Poor S-parameter Data EuMW Seminars 2013

30. with DifferentialView and Dual Source + + • True Mode Stimulus capability • Differential, common and mixed mode S-parameters • Adjust differential phase & amplitude • Instant view of results during parameter change + _ _ _ + + _ _ Differential Mode Common Mode Mixed Mode EuMW Seminars 2013

31. Superposition and True Mode Stimulus Time-coherent in phase and amplitude DUT DUT Port 1 Port 2 Port 3 Port 4 Port 1 Port 2 Port 3 Port 4 EuMW Seminars 2013

32. Applicability of the two methods EuMW Seminars 2013

33. Trade Offs • VectorStar MS4640B has a second source option and DifferentialViewTM for true mode stimulus measurement • Only recommended when device is non-linear EuMW Seminars 2013

34. To Use or Not Use True Mode Stimulus? • Amplifier in non-linear region • Difference between superposition and TMS apparent • Amplifier in linear region • Difference between superposition and TMS not discernable EuMW Seminars 2013

35. DifferentialViewTM for Signal Integrity Measurements • Broadest frequency span: 70 kHz to 70/110 GHz • Best time domain analysis capability • 4-port test set upgrades 2 port VectorStar to 4-port performance. • Widest range of calibration & de-embedding methods • Choice of TMS or Superposition Good S-parameter Data Poor S-parameter Data EuMW Seminars 2013

36. DifferentialViewTM for Broadband and mmWave Measurements • Compact size and high performance make the Anritsu mmWave modules ideal for broadband differential analysis EuMW Seminars 2013

37. DifferentialViewTM True Mode Stimulus Interface • DifferentialView offers easy configuration for differential and mixed mode measurements for thorough analysis EuMW Seminars 2013

38. DifferentialViewTM TMS Setup and Editing • DifferentialView menu provides real time display of measurement parameters • Immediately observe DUT performance changes with changes in setup • Example of modifying phase sweep parameters while observing effects EuMW Seminars 2013

39. VectorStarTMDual Source Option + + xN a1 b1 a2 b2 _ _ xN • Option 031 Dual Source eliminates the need for a transfer switch • Provides up to 7 dB of additional power at 70 GHz • MS4640B series improves noise floor specification as much as 9 dB • Combined, results in improved dynamic range performance up to 16 dB at 70 GHz! Dual Source VectorStar EuMW Seminars 2013

40. Measurements of Nonlinear Differential Devices + + xN a1 b1 a2 b2 _ _ xN Non-1800 Phase Offset at DUT Input 1800 Phase Offset at Test Port No TMS correction applied. Dual Source VectorStar • Characterizing differential devices with a 1800 offset is the goal of component designers • Nonlinear devices are sensitive to source mismatch • Source mismatch will shift stimulus signals to non-ideal offset • Without proper offset correction performance of device will vary • Anritsu white paper discusses this issue EuMW Seminars 2013

41. Measurements of Nonlinear Differential Devices + + xN a1 b1 a3 b3 _ _ xN 1800 Phase Offset at DUT Input 1800 Phase Offset at Test Port Opt 043 DifferentialViewTM: Measure mismatch and apply correction during measurement Dual Source VectorStar • Applying TMS correction within DifferentialView corrects offset shift • Monitoring the applied signals (a3/a1) will provide an indication on the success of correction EuMW Seminars 2013

42. DifferentialViewTMPhase Stability • Sweep to sweep phase variations from 1800 differential while driving nonlinear DUT at -12 dBm. 10 MHz to 50 GHz. • Measured result showing < 1 degree sweep to sweep stability EuMW Seminars 2013

43. Resource Materials • MS4640B Technical Data Sheet • Signal Integrity Application Brief • White Papers • Overcoming High Speed Interconnect Challenges • Signal Integrity: Frequency Range Matters • High Data rates Require New De-embedding Techniques • Superposition vs. True balanced: What’s Required for Your Signal Integrity Application • True Mode Stimulus and Stability • Application Note: Ideal Pre-Emphasis Constant Setting http://www.anritsu.com/en-us/products-solutions/products/ms4640b-series.aspx http://www.anritsu.com/en-US/Products-Solutions/Products/MP1800A.aspx EuMW Seminars 2013

44. Summary • Solutions available to 20, 40, 50, 70 and 110 GHz • 70 kHz start frequency and low frequency dynamic range of VectorStarTMcritical to signal integrity application and to ensuring measurement-simulation correspondence • MS4640B now offers DifferentialViewTM and 2nd internal source option for true mode stimulus measurements • Easy to use graphical set-up • Real-time view of measurement while making parameter changes • Advanced true mode stimulus corrections hold phase relationship at DUT • Upgradeable in frequency, port count and options • E.g. can add second source and DifferentialView later EuMW Seminars 2013