BSTJ 50: 4. April 1971: Statistical Circuit Design: A Case Study of the Use of Computer Aids in Circuit Design - Pulse Equalizers for the T2 Digital Transmission Line. (O'Neill, L.A.)

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Statistical Circuit Design:

A Case Study of the Use of Computer
Aids in Circuit Design—Pulse Equalizers
for the T2 Digital ‘Transmission Line

By L.A. O'NEILL,
(acuapt resived Deemer 1, 120)

Coneuter simulation makes i osonainiclty feasible to avalyee
computing tial soofineations ant eptoize fhe ivelt paremeters
‘using complizcled criteria related te aystem performance. Pavtharmoe,
te infance of marafocturing loferusece on aptinsed performance
fait be sterstioaty ravnitipni! (0 stabi eooyponent specifrsins
iors postion a tard Ths, the Aesipu em yet mere esiy
sviedfer aot « event il perform eagately se fhe eb

Ti ation, computes pus teat wate eae wrovideocevente wea
remente ef carat wsocoance dirig mgmfecrre to never thot the
product wil be satioluctony, These text facilites oan be rogramaed

ide a factory wvniaavon of the tndordual eicwits buved on

rate aystem performence
Ta uatrate these concep, it ie thown Low computer ads wore
tiie nthe design of the ptee npr for tho Te digital tremse
Inisins lite, The discussion of the eimobcer design sa intended to
veeate why ands shat romuner the wariowe funetione wore imple
ented, The stain! tolerenne gnalysie ond mavusactuving test
ihasee receive the grelest enpain x they are the most rezent dex
olepraents

‘Tolerstee grnlsoi 6 the snors reset develoomie in a eontinig
ior to design eituite anc eymeme reebeseally. Reale reeuires
the! yew rodel as slose'y as penile sheeple tleontnen Whe
the ceunene “notions suet bs ganas As sorqoss evovad
t has bonny eemsoiiesllydeceible Uo take avy and mote Zactrs
ito nest, The objesve thar is anieipate potentislprob-
1244 rm ama seoxene asenvtow, rooRAL, arm WPL

leas so Chak they say’ eliminstad in ube design phase rather than
tinexpecey bo dis then en tke vi eat ino servic, Senn~
Cand deg praetion into soogres through wevazal test phase, fest
wing breuieasde and poorctypes of lial cents then ‘sing
toupee nystenie fn ee ld since ad Ted serves teal. Icom
Dutor simulation fe len steplayed dari The design voce, i is trex
tqietly posite to detear design ceitneies wl mu ener sage, and
‘he eclir the probleu is eee the loge exzeacive isthe vorresive
ation

The impact chat the eax hus bad on this quest for renin is
snost readily iiotentl wth speie canople, The devga of the
pulse equalizers for the T2 digialtrunenisson ine evolved during the
fre dssine! fn the ited to this ewe The (he irprowements
[n compuvers nod compuletaided design techniques wae it possible
‘te ntreduee mare and ore eee dato tho eesign proves Titi,
the computer isl for analyse (op eilasion) of the euslaer
fad the evalaion of vnsplicalel yeriormance measuzce so tht the
‘tugnsoeeouls tzae desia deitians. Subzecuertly, when more pone
is eampnters beste wali, Cie untion af te ecsuputer Was ie
seeased so peosids ascomacie yinivation of cho cesui pucutelers.
Not, the influence o: mariactaing talesanzes ox ostinitl perfarm
sae’ ets sate enlly iwvostgatad ta steblis components sere
tions. When the arolu.spem en oopetmeted, dowd suewsuremente
‘nade ona Computer porated Trnamisein Measurement. el
[COTMS) mene weed to insure at une equctzes performed as pre
Ato, Finally, che equaizee were tested at WCo on COTM using
tveriteron Wi we representation ofthe one vse in the design pees
‘This iwuted tha the tamesselsre ie wuld also pooside te pee
Atal performance.

"The subsequent discursims is intended to aletrate why and how
ie various operntions are plemented in or o olin ease pre=
Airis of performee. Sie the isnot incended ws» histary of the
Inoject, ani vee develope divetiy soled to computer simula-
tigm as disousees, A.thogzh st © epecibe exami the diexssion ean
serve ase ie eo thes deeigners nf w her systems can prot rem the
fexpereree gine wih 12

21 Dain Requirements
A soto pulse equaliere was desigred ‘or the 72 digtel eran
‘coMRETER-MneD nglenRFR near 1216

‘oon Tne which opezstes at 63 milion hte por von Te equator
iat beset ofthe aypence shen in Fi. The Tanti i to eee
fhe pulse dispersed ty she cable ie 4 ehape esitale for desing
‘ohat level was teeenited. Tans gibisare Pon semsled endl regene
rtd fer retransmtsnn, The iapat aad autpus of Iypiea! equaice
fre shown in ig, 2 The upper trae en individual pulse wter caper
row ly the eable ga wexived et point A 5 Fig. {snd the lower isthe
“aime pale ar the ootput of the equalizer, poe

‘An weal ansmisnion consis of © sequeaee of thes puss toed
cone sizneling jlersul aparl. She this snterval eoresponds (2 one
Sivision ia Fig. 2 ie Se iden thot cyoulxed as well as Une
fqualiad pulser would ovetigp. Even if the causliver oumpat pulee
Ws samt exaely a ite peak, eae typial pulse hes nonsero values
ab adjacent sampling vines eepazeted by the signaling interval. These
onaero values fleriene will the dectsion made ne the neighboring
faring tisee; this i eles to interim! interference. The,
ne eoushges design wil be insereed bath by vatatins in sampling
tne and intersyanbal interference anes ajaen ye

"The pe-formancs aneamize Tor cuuinkacr vagy she ellel the
laflucnes of se many Snetors 2 ie ie teashlo to ade chat might
Ieee the camee: regeneratuey of Me urwmmubed iefenmation
Thos, t2: design criterion was erm rit, lie rate at which eots are
tasce io mpeneration. Since, for example, tae design requcereat for
fash zegenerttor may be lew sha or stu in 10" ransintted pulses,
fxcrsive eonpurer tine i required (ur wvurale ralimalion by aca.
Sling ersors antes, the probabahty of ereurrenee esl
This eeloulaion inches most soures of ilevienner, for exemple,
Interspmbol intarerene, sazapling iter, eral noise nd eros
{due io usighooring transmission paths ‘The probability of eran

=]

muee 1b age

a eee et 7 srcrnpearon 2h

ig La pale rept and eens
1045 ram anu srovea RESHICAL JOU, APL TT

4

er N

ig 9s iteeecee cally ete dion

Bat be ently

‘ease by noise can be kept los by muusmizing the wovwt-rae sopan
ration betwen aiaornt signal level; this ecpurtion is refermed to 8
the eye opering® The emer rata Wl bea innnaa if the eye opening
‘which i hversy properConal ve atersyzabolinverferee i empl
fb ile levgect point. Tei lm ad i Sache gt hone faeiora fa the
Crivorion tus makes raoeesay ta Uae wor La tain vealisic
preilion of performence

24 Characterisation of Pransnieson Hedin
72, the ora none a terse oie of Snead ies
‘within € multspair euble, The aperdim produced bya oable pair
tpends on physienl prnpetive eh an wie gouge, ene etiity of te
Sire, ecpactanes. deter marae] and length of cable betwern
egencratre; some of wish am affected by tomperature, To deci
fu equalizer thet compensates for dispersion, ris neecsary chat
‘the mesiurs be correctly vale. Ria ahaructereation reyuirs hs
many lilvidualeable pair be wrarsialy mearured ce that an average
‘eproventatigu ean_be ehosrn sha wil Tedeet the proper dispersion
Gf the pulses ns exble length wil temperature age vari. The aver-
Sing operat asn smooths the dit, ow minimiving the eect. of
Tressurctnnt cers. Pelynonsinle sre shen Sted to Doth the average
fom and pase charaevarzstion, ‘hue, any mmguinel eable can he
sinalaied by a proper elaine n? contents for the pelynom:nals

28 Reales Confusion
An dative eonfgunisua Jer ube aliner was seleted to raluoe
‘ie nrses of daaigns wees. to vover the entre Joes sarge, that iF,
conervTes smo scenes mxsics i

lowable cable nts The Tasie songuration contins up io three
onstant-R shiping networks sla automate line bud act (ALBO)
hetwork. A hrdjsi-7, eonelzat section, se shown in Fig. 8, pro-
thoes cea sero al prof ep poten the transom pata
for reshaping the cispersed pulses The ATRO i ten rimple Rl,
sctius whose singularities ave arigted to keep the aut ample
thi shape constant. Te vusible cletaents ia the ALO sve ressances
Ivhose valies ae detomined Uy the fervare zesiares of dno in 8
Teadhgek eontial lop, ‘Pie brick desertion 3 alee for the pee.
enn; for adutional detail see Ie 2.

"To surumatae, the analysis objertive was to simulute how the
qualizee respond to various ele [nag temperature, and input
pulse shapes eo abst the pba o err cool be oalewaced. Thie
ShulssisTollaeed two paths, « distal simulation for exlu'asing the
fer rite of spotife equnTxad eanenieion channel, end a anelog
fimletion Jor Bovestigating the inuonec of equazer pancnoters
tor pes shape, ‘Me tw epronrhae wane oomined ita Ebr
uation Sia wee toed foe erat wotimoaater

24 Pale Trnsnosnion Program (CPP?

‘Tair digit onograne eas be ase for exlecnsoe Gre pee shape
fee opening, sas etror rus of w patlole epic atte to a
feed cehle, Tie roprsentaion of Ube qaustics miye oni of
tte exerineatelsnearszements, ot 4 combaaation of bth, With
‘hi Eile seostom, i posite rs imo lero pai
peviersanse prods by ehonging he ele star nen an oat
Duise shape, aswel ns ming arbitry ‘seu da nue the 20
ate eet,
1288 nua au, siete erewernar Format, aE

‘This prograss mae the prinipal too wa he nti) design phase
snd it wll ut oral invstgations other them iterative optziza-
Sion. The comptatoual upproceh is 19 vombive all che individual
represnsations of the vioue setions in m single att of Toss and
hase deta, Am inverse Fourier tranaform is then evwinted to dete
tine the equalize pulse chape. Irom this pulse shape the eye open-
ing and ereorzate are exleulite. ‘lhe pity tens change pee
entations is pativulacly valuable ix allveating the Sesion mame
mang the various ecetions of the system,

25 Hybrid Simatation

‘The equslies wor stmlaied iitially on ex analog computer be
‘use the tine resulted for eAipital eclevlation of Uwe pulse response
Svas tou long for fective Inne “ateraesion. The parallel eperation
fof the ule comune jraviler a rapid evanstion of the time
respanee of conannse¥ateme. Thue, oe dasigoer etn modify aqual-
Jace penile er sine nnviguretions while watehing the eect on

he psn renee THe willy rapidly ‘eras: wth the smalation
fnablea the eesignes 12 dclop incuition ckeut the erest operstion
fant apply tlie kowwledge tu ingunive thio sign. Tale interactive

fapohiity wae upigce om the analog eoruter at the star dhe
design phase "Todas, fener eigtal coxputre with arepbic diep-ay
Adeviees can alco sfode tome of this izzarcetive eapetity

"Th diptaleomater sas Uist converted 19 the aaalog in a bybsid
sin ulation to gonerate reality ieserse! sue shoes “ar equation
Jo Une se deeigies ou obsere= weal the inFuenceof para
or variiers a equalized pave shee ‘ht simslaion wes Conia
in its aopliration reese a ione gearesentative eilrion, eh at
rrr cae, wis seule! lo suapesty weight al fatoneintencing the
sign. When nnne proerful digits: computers teeane svaieble,
they were uel Jo protec ye ala fron the anclog eompucer inorder
tn compute the error rate. Finally, « wnce modern hybrid made it
possle te iuplenent pt talomle ope mizabon stot

‘Since oplinizaton was of prine impostanee, it was nenewary to
‘een mii te mubor of paranactere eo be wdjuee TE th
sur mat dane the time sequtea far eonvengnse ton uplionan ould
Toone exert, tne again making the Taman intereton inetee
tive. The bridge sertion: were representa! by x single zero, tx
pole network rusher thaw sitaultion 9 the actu! configuration. "Thi
Epprorimstion nssunses Unt he sores oad lun ats une comely
mmatehed. The ose of « simplifed repressatelon, of eoure, ecuires
cusrenaesmee 2qualanee mR 09

hat the optiniew parararters Iter be eonverte into the component
‘lcs for the bridget-T networks, gia program was writen chat
“ive! bom staneand pars tins the eon: valuee neazest the
Yalues compated font che oplinise parameters. The eeeions of the
Arquier tat wee not be apiniza mere ited by conshesing
Up setual network eonRguration. This yes dive vo chat the models
tard oul! be mede to conform ta she aneenured device pacar,
Dartvalaly, the ciodos ym Tae ATO.

"The progrean wed for oprizaizans was hesed on Ue general
purpose Hybrid Optiinwrien Prograns (HOP)? that was inodiied
Rovcifeally tor T2. For euch vowslver, a ALTO wee designed roxn-
Tao and then (he Axed liner seins were uplomized satomat
jeatly. The blk agra ot she ytwidsisultion of the equaliee is
thosra in Fig, 4. The eptimixstion yeugeam allows fo up t0 eight
Aliferns eabe lengths (thas ve sepeeentative oF The range of appli
tation of th sian) to be wun in desiging she fe eruliges
‘The Pulse Tunney Progcuan véevibed in Section 24 iz wed io
generate the uneqatisee pau ia) wl? onoue with exch eal. teh
Frou ic used to ave the eqaber scales 6h the eaaog eoxnuler
rh ie slap sections propery avjsstad for Uw eable. Te eval
fre the effet» theanal asus or sch equsbge”cesiqy er impulse
thred a2 an win pt The equ se pea are scape eed he
‘hermnal noi: comb Sra the sted uayole sjnse: chest ae
Teil fo compute come ta on ie lal eomsutes ‘The worst the
(Bat fdividusl error rates i r3ed om Uw 2asure af perfortucnoe
“or eask rene

‘inl ex io design ig determing sarsvly Means the eg
set mint pravite a reuouube larg pet for 26 opeimisalion
Soweay. Te Sinplesrzacoge fe ned (@ elect the west parameter
fev spetiisng wn oases, wl Tae exsire rows ys repeated unt
the Tentive impeoement ow performance is Inlew a presceeied
Timi "The strateey neyuiy sly a eealar pefaraance measaee for
foal esi and eoce 20: nine taal eer waves he errapted fo
tviont search procelui. This tf mach Lee antive to acaeur

Fig {tsi splorsmsation wd or tinioson and sleece analy
1280 rw moa seenENE MACKUEAL JOUNNAL, AME 3672

ment eron inkeret i unslog salaion, For wn 2 parameter optima
tation, n | I designs tauet be evulusted iitn!iy, The procedure
iteratively soplaes the worst of the » + 1 degre by another design
whieh is chosen slong the line comneetng Ue ara. pin with the
enter of gravity of the ther densus iu tte mlimenional parameter
speoe, The bert positon along th Fie ie deerminn? ly Laeeively
evaluating desis found by operations rues as “reeuton” aut the
enter of gravity, “eontrectin” towans it, “expanion” eway frum

"This dvign strategy resulted in a set of cyutlisers Ct sisi 1
roquefnents for 22 Held tria's. A nl design phase x71 necessary
itr we information gsined in the fl tens i salen aco so2ount
For this fina passe s digi uplamoution yengrem her just een
‘writen tha: posi dete that Be worurate 4me qreaae. A Mes
imation wa 20 lnngersequired fr huran interuetion we Ue von
SBrucwion hag been chosen. Ths, it wee poesibie to wsta w inst,
Algal apalys's wgosthm “or thi retsicted apolieaton

‘Taroughout te desig. pate, che ex low ber goncermed wich
the sealachility of the eondiguscion ata ite seit to parameter
aviation, Cee sho seige ha bees apizcived, at ie nesmmry ty
‘verily thatthe perforce wil ail bo auesats olen faring.
Tnitaciers ave eoneidesce. snd tha the somporoxt tolerauves ure

canal
‘Tolerance analysis ie required hosasae tho optimized parameter
values euatol be exactly nla ir wmtesture, The partnetar

lies te i exah benaiae aiumtnia are a's avalable only
in sere ranges with a sittin) epretd in each ennge that de>
ener apa the macavtsting proms und le eamne nt age

ye aller estensive analysis esi neeeeany to teeaente the
wsformaer of the actuel cious. Fit, prototype ercuits muct be
tested to be sure that che predicted performance his been obalned
Fach menufectuc eireit mst then bo tested to ensure thot it hoe
wn properly sisembled. ‘The computar can aid in eigenosing
proditions are ne reslizod anal len im automating the faery test
proche,

‘84 Tolerance Analyse
"The Monte Carls apgrutrh to tolerancs analysis esis of sie
Ioking the eystem ue investigation, raeowyPercuring che pan
oNtreTatbe ADCALIEEE MBSLON 251

ler values end displaying the aistribation of 3 oenlar peformance
Ineceure With this ayproue, he haece of eemaponent variations on
the nonlinear, err tate performer measure could be inveetigatd
with fewer cecum avd apprexintione then requir with more
oalytieal approaches, The mare erate sirtenming wich chi wpproaeh
is tie amount of eormputer Line erred to rye stately sie-
rifeant ‘fain. since aussi Lie i as eniiel Gein optimiza-
ion, the same lyr sinulation ro toed. To reduce Uhe number of
lanaysis re, the dosighrr un ilenaet it the ecnpaler while wate
fre geupie ela of x hstrann ofthe pesformnne rescue. Thus,

a picly tevin uuassntetory ei, and aso resize by the
Sinenstity 0 see display tne Geta when suTsient samples have
Thorn aceumnlated rather thao always geeurasting te amount of
at required ia pre-ecleiol cordence lint

The infvence of parame tolseases ont die erent rate to be exe
rcten (ron wpe ani von vestigated ta wid jn vie isking
the manutactsing jefe for lh be Buidged-I' sotions end
Ihe sloptive sections, The eomgues program ceprate tae following
esque of sperains aan seoumtsiks ee diesIovions under Ue
ses conto. A vol uf yerbares earsoneut velnee for rat design
Te telestod fzoay the sagsone sotniestion epesited by che oosninal
Salugs wes taleranoee he laieneap:

paves = Sigel + Tolerance % Ransom Nubes)
sokere the wan namabur in (ie range 1 ie select rm a sete
Aistnbution ‘Tle rempenent cisafotione weed i the snsequent ine
eeigaion are dceeibed iy Sel" $41.1 Senulation puree wars
tee somplal oon she pertur seer the hybrid computer these
tte pocrtiomsier vale, Bork an uaequalized pulse cn an impulse
fre applied so the sale ssmalaioy oo dating cerer ria, ax ding
‘the op nication phase ts pombe tw eezhnate che errr rae Fer one
flesign every Toe vide wih she nulatice

‘The dismurtinn gf sae information avtsvel [vom oleranee wale
se divided ncn chzee past, Un Setinn 3.12 onky he brlged-T seins
foe partuleal wil the ndeptie lan open, te delernize an accep le
fet af nus lerances Sor tw pssive conponnt, Tn Seston 1
{Ee relipive sccion operating lose loop Be wed Lo determine how
Costly tie ALBO dle muse be watched, Fizely, mn Seoticn 3.14 9
ised loop silo woe wit a corgpocents pertain deter.
Inne ansiepatd Yield an watts faite for a Jurory seveptence
1252, yn wth sve tmRNA sone, APA

st Component Distributions
One of Bie ss iil plein in tolezsace snalyse isto obtain
sweating eonyenent data. TF only telative compasiagn ie equi,

iV sulfcentte use orale npirisnncions la the asta estribations
but when one wample Yo ceurnily preiet yields, exact data is
recqined with temperntase effec saul aging aon in noon, Bin

nly relscive eomparions between various sete of tolerances were 2e-
(qited for tho aralysis deseiced in Seotir. 212, al pussve cou
Donent values wore aastou! manual ariel lh the nominal
Yaluos a5 the wean. ‘The stendard deviation of the uisribuvior wee
eben {o one halt dhe speifae tolerance

For proper rl lop opera af he ATO, i esata thet

Tosh wots ao ine tpi roe espn, Cale
the dysamie rvstsee uf the iivda diode, aaed to provide the
rine nase, i aggvocinnt'y Fre auras fatnoy af te cane

Carre, (is tracing exmact be cusinined. To provide adequate
trucking 27 was ces tacks a ect of mntcbed diodes, Tho oat
Gt ritshiog 9 ae will uf wours, sequal or Thy sllowaloe ees

re lye ys Ly tering wt
‘abide saan production

rove within eT
irae gh corel hi
Tine teobaietor oui Beate

‘The digler we tn Iw raateho age on thei mene
sto values ear the wpser re lower File cose lngp eurent.
‘The mateking operation wus sirulatel ia 780 eps The fa diade in
ch sot wus ape hy shea pir wf vosance velues from
measured ditribuvin Sov ns ode (ye Tie aa val eed be
felosted mndepessenily boeave Ue reietance ak uhe high enrzen level
Spend primarily en The hth site a the materia whe the
Tule rite scam hy err et ia i lw
level Phe rerainder of Te cet Be alae wang 9 uniform distr
Intions, Daving ie syed ling, Unity aera on the RoR

"Tae die matting init were ehngen tn zee net only the erin
Imatehing, but also the ehanges that would occur with experts
snd aging, For axcmple, i the oiginl match is asumed to be tro
‘me, the osnge may broaden to si abe becance of thee efeere. The
folercnoee nn te passive componente ware the sume as thow wed
in Seetion 3.1.2,

Afterall tolerances Lal een spite far the components, addi
tional investigations were performed tn determine anteipatd yield
and pesformanee variations at could be expote wil a typioal set