Multiline Overview. Karl Bois, PhD Lead SI Engineer Servers & Blades. December 5th, 2016

Transcription

1 Multlne Overvew Karl Bos, PhD Lead SI Engneer Servers & Blades December 5th, 216

2 Why are we here? Orgnal Equpment Manufacturers (OEMs) and Orgnal Desgn Manufacturers (ODMs) have desgns that requre that the nterconnect such as the Prnted Crcut Board (PCB) has a requred electrcal performance Typcally, PCB constructons are desgned to a gven metrc of attenuaton per length (e.g. db/n) IPC D24B went to great lengths to provde four methods that correlated n behavor wth each other, but dd not yeld a consstent answer; that s correlaton but not agreement PCB assembly houses can chose whchever method they would lke and stll consder themselves to be IPC complant There s the opportunty to get t rght ths tme

3 Lmtatons of current technques SET2DIL: great hgh volume manufacturng mplementaton but lacks de-embeddng, va effect usually contamnate the results. 1X Thru: verfyng the fxture qualty of 1X thru s really hard, and the methodology s very user/mplementer dependent. Targeted for 1 Ohm test envronment. 2X thru: n ts raw form where only (SDD 21B -SDD 21A )/(L B -L A ) s used, t requres that the length L A be long enough to reduce the near/far end reflectons so that the subtracton can be relatvely close to that of a VNA. The coupon sze cannot be guaranteed to be >4 for L A, and there wll always be rpple n the measurements. SPP: NIST verfed for propagaton constant measurement. However user short-cuts (e.g. low bandwdth scopes) tend to produce results varablty. 3

4 What are tryng to acheve? Use a technque to determne frequency varyng propagaton and loss parameters of PCBs The technque must be smple but no corners must be cut n regards to accuracy The technque cannot have prebult assumptons for t to correlate to tradtonal measurements No specal launches No non-lnear operatons No requrement on mpedance Ths technque exsts snce 1991: Marks, R.B. A multlne method of network analyzer calbraton, IEEE Transactons on Mcrowave Theory and Technques, vol. 39, Jul. 1991, pp

5 Multlne n a nutshell Measure S-parameters of two (or more) TL lnes Lne 1 (length a) Lne 2 (length b) Compute propagaton and attenuaton constants Extract R s, e r and tan d Optonal 5

6 Theory X l T Y 1 S12 S21 S 11S22 S 11 M S 21 S22 1 M XT Y Wave Cascade Matrces T s a homogeneous transmsson lne The egenvalues of T are. 1,2 e l Complex propagaton s. T e 1 1 ln l l e l 6

7 Theory (2) X l T Y X l T Y M XT Y M XT Y 1 S12 S21 S 11S22 S 11 M S 21 S22 1 M 1 S12S 21 S11S 22 S 11 S 21 S22 1 T e l e l T e l e l M X XT 1 M M M 1 T T T

8 Theory (3) 1M 2M M s calculated from measurable parameters M and T have the same egenvalues, T s related to the propagaton constant,, T e ( l l ) e ( l l ) l 1 M,2 M e l So can be calculated as, ln l l where M 2 2M 8

9 Choosng the egenvalues l l 2M 1M e Choose the root that expresses a wave propagatng n postve drecton along TL. 9

10 Choosng the egenvalues (2) For each frequency pont, choose such that > 1

11 Optonal gong from complex propagaton constant to materal propertes c d e r c c R dc 2Z o f R s f d e r tand c If c can be found, All other quanttes are known 11

12 Sample measurement Alpha_measured Alpha_conductor Alpha_delectrc Alpha_reconstructed Frequency (GHz) 12

13 Comments and applcaton notes The lnes should not be multple wavelengths of each other Can brng some nose n the data Same methodology n choosng Thru-Reflect-Lne standards Only two lnes are requres and the length s not crtcal If there are more than two lnes, then a covarance matrx mplementaton proposed by Dr. DeGroot can be used to flter out measurement nose n a analytc and theoretcal manner. Hewlett Packard Enterprse s currently usng ths technque wth domestc and nternatonal ODMs wth great success. 13