Copyright © 2014 Wild River Technology LLC Slide 1 Wild River Technology LLC Alfred P. Neves phone A VNA Manifesto: A Primer for Practical Mastery Day 1: What Is an S-Parameter?

Copyright © 2014 Wild River Technology LLC Slide 2 Al Neves – Chief Technologist for WRT, WRT has been in business 3 years, based in Portland Oregon area, was SI Consultant WRT markets products for SI community Signal Integrity Practitioner, Test/Measurement Track Chair DesignCon

Copyright © 2014 Wild River Technology LLC Slide 3 DesignCon Presentation - 13-TH4: Managing S-parameter Data for 10 to 32 Gb/s Time-Domain Simulations. Thursday, 11:05am-11:45am Presentation - 13-TH5: Cracking the Code of 32 Gbpsec Differential Vias with Advanced Time Domain Methods. Thursday, 2:00pm-2:40pm Forum - VS-05: The Role of Improved Measurements and Tools in Assessing Simulation-Measurement Correspondence for 32 Gbps Systems. Wednesday, 3:45pm-5:15pm

Copyright © 2014 Wild River Technology LLC Slide 4 Methods of Improving 3D EM Model Development and Associated Time/Frequency Domain Measurements, EDI Con, China, 2013 “Methods of Improving Time/Frequency Domain Measurements Suited for 3D-EM Simulation”, DesignCon 2013 “Robust Method for Addressing 12 Gbps Interoperability for High-Loss and Crosstalk-Aggressed Channels” DesignCon 2012 “Measurement-Assisted Electromagnetic Extraction of Interconnect Parameters on Low-Cost FR-4 boards for 6-20 Gb/sec Applications”, 2009 DesignCon “Practical identification of dispersive dielectric models with generalized modal S-parameters for analysis of interconnects in Gb/s applications”, 2010 DesignCon “Developing Unified Methods of 3D Electromagnetic Extraction, System Level Channel Modeling, and Robust Jitter Decomposition in Crosstalk Stressed 10Gbpsec Serial Data Systems”, 2011 DesignCon

Copyright © 2014 Wild River Technology LLC Slide 5 VNA Measurement Approaches: RF versus Signal Integrity Common Applications of S-parameters Basic S-Parameter format Relating S11 to S21 vectorial relationships Interpreting and getting feel for S-parameters

Copyright © 2014 Wild River Technology LLC Slide 6 Usually narrow band Wide dynamic Range Requires sliding load cal kit or coaxial TRL Time Domain not important Passivity/causality Reciprocity/causality TDR/VNA/BERT correspondence Eye Diagrams RFSI YesNo, DC to Fstop YesNo SometimesNot often Not oftenYes

Copyright © 2014 Wild River Technology LLC Slide 7 … among others Loss Modeling – Surface Roughness, Improved Measurements for 3D EM solver correspondence Package Design Verification Channel Models for Simulation S-Parameters Models for Simulation System Design (Capitol Equipment example) Component Evaluation/Characterization (SERDES, TIA, Limiting Amps, Clocks, etc.,)

Copyright © 2014 Wild River Technology LLC Slide 8 nxnx Gaussian Noise S-Parameter Model of Channel Insertion Loss Return Loss Impedance Variations Resonance Crosstalk TX RX

Copyright © 2014 Wild River Technology LLC Slide 9 We demonstrate a method of opening eye with higher integrity

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Copyright © 2014 Wild River Technology LLC Slide 11 Cost vs. performance Stackup/Via design ASIC/IP vendor selection Connector selection Equalization settings Speed vs. Length Extending backplane EOL Standards compliance Increasing Equalization Increasing Channel Loss

Copyright © 2014 Wild River Technology LLC Slide 12 Line card Backplane Traces (Wline model) Traces (Wline model) Backplane (S-parameters) Backplane (S-parameters) Package Model (S-parameters) Package Model (S-parameters) SerDes (IBIS-AMI Model) SerDes (IBIS-AMI Model)

Copyright © 2014 Wild River Technology LLC Slide 13 Full system (multi-board) model Channels meet compliance specs? How much margin? Which channel is best? Worst? Why? Isolate & debug failing channels Eye Height vs. Eye Width Red: Send, Blue: Receive Eye Height vs. Backplane layer Eye Height vs. Connector row

Copyright © 2014 Wild River Technology LLC Slide 14 Linear networks can be completely characterized by parameters measured at the network ports without knowing the content of the networks. Any number of ports. The ports can be characterized with many parameters (Z, Y, S, ABDC). Each has a specific advantage. Z relies on open, Y relies on short, S, relies on matched impedance Each parameter set is related to 4 variables: 2 independent variables for excitation 2 dependent variables for response

Copyright © 2014 Wild River Technology LLC Slide 15 THRUSHORTOPENMATCHED PORT 1 PORT 3 PORT 2 PORT 4 Z relies on open, Y relies on short, S- parameter relies on matched impedance

Copyright © 2014 Wild River Technology LLC Slide 16 Circuit with lumped elements, rational polynomial and BB SPICE macro-models Distributed circuits (models with delays) Tabulated (discrete) Touchstone models SPICE simulators Electromagnetic analysis software Measurements (VNA or TDNA)

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Copyright © 2014 Wild River Technology LLC Slide 19 S ij = is the reflection coefficient of the ith port if i=j with all other ports matched S ij = is the forward transmission coefficient of the ith port if I>j with all other ports matched S ij = is the reverse transmission coefficient of the ith port if I<j with all other ports matched

Copyright © 2014 Wild River Technology LLC Slide 20 S 11 (b 1 /a 1 ) Forward reflection coefficient (input match, return loss, VSWR) S 21 (b 2 /a 1 ) Forward transmission coefficient (gain or loss) S 12 (b 1 /a 2 ) Reverse transmission coefficient (reverse isolation) S 22 (b 2 /a 2 ) Reverse reflection coefficient (output match, return loss, VSWR)

Copyright © 2014 Wild River Technology LLC Slide 21 PORT 1 PORT 3 PORT 2 PORT 4 Tip: Getting port definitions consistent when for more than 2 ports is non-trivial, especially when the other members of the SI team are addressing 3D EM and system simulations DUT

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Copyright © 2014 Wild River Technology LLC Slide 26.csv.snp Formatted and unformatted proprietary bit map images

Copyright © 2014 Wild River Technology LLC Slide 27 magnitude magnitude in dB phase TIP: We use Real/Imaginary Format exclusively, versus Mag/phase, Polar, etc.,

Copyright © 2014 Wild River Technology LLC Slide 28 Ratio%dB

Copyright © 2014 Wild River Technology LLC Slide 29 IF BW 1kHz 4 port SOLT Calibration, THRU paths 1 to 2, 3 to 4 No averaging, no smoothing Fstart 25MHz, Fstop 40GHz, 1600 points

Copyright © 2014 Wild River Technology LLC Slide 30 Display S-parameter Touchstone in text editor, Matlab, or some other tool of some measurement Export and Save a.csv S-parameter and import into Excel. You can create a simple viewer using Complex Math slide. Print out S2P file, examine frequency spacing, value of normalized impedance Confirm format is Real/Imaginary and Not Mag/Phase, confirm this on VNA setting

Copyright © 2014 Wild River Technology LLC Slide 31 Questions, discussion? Alfred P. Neves