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Humanbe Final Paper
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A thesis for comprehensive income taxation in the Philippines
Table of Figures Figure 1 (ock diagram of sys"em...............................................................................................# Figure 2 Po+er s%''(y schema"ics..............................................................................................., Figure 3 R- mode( of coi(.........................................................................................................5 Figure 4 R- mode( of sma(( coi(...............................................................................................5 Figure 5 (ame con"ro( schema"ics..............................................................................................4 Figure 6 (ock diagram of P/P2M mod%(a"ion sys"em.......................................................10 Figure 7 Schema"ic of P/P2M mod%(a"ion sys"em..............................................................10 Figure 8 P%(se 2id"h Mod%(a"ion %sing a com'ara"or..............................................................1# Figure P2M circ%i" %sing an o'am' in"egra"or "o crea"e "he "riang(e +a&e..................... ....13 Figure 1! P2M circ%i" %sing P7P and 7P7 "ransis"ors "o crea"e "he "riang(e +a&e........... .....13 Figure 11 -oi( "i' gain &s. "i' "o drain 'hase (ag.................................................... ...................15 Figure 12 Schema"ic of de(ay mod%(a"ion....................................................... ..........................15 Figure 13 8ra'h of s+i"ching +a&eform for M*S9 ga"e.....................................................16 Figure 14 Schema"ics of &ariab(e de(ay b%ffer....................................................... ...................14
1 - "bstra#t sing a &io(e" corona of ioni;ed air< a '(asma "+ee"er crea"es a mass(ess< omnidirec"iona( s'eaker "ha" a((o+s for highfide(i"y re'rod%c"ion of high fre)%ency a%dio. he goa( of "his 'ro=ec" is "o crea"e a (o+'o+er< (o+cos" &ersion of one of "he mos" idea( s'eakers e&er in&en"ed.
2 - $ntrodu#tion
2.1 - Advantage of plasma speakers over conventional high-frequency speakers
-on&en"iona( high fre)%ency s'eakers ha&e a n%mber of dra+backs. *ne of "he mos" diffic%(" iss%es "o address is "he mass of "he s'eaker. he &oice coi(< s%s'ension sys"em< and cone or dome of a con&en"iona( s'eaker a(( mo&e "o genera"e so%nd. oge"her< "hey add %' "o m%ch more mass "han "ha" of "he air "he s'eaker dri&es. D%e "o "he iner"ia of "his mass< "he s'eaker can>" res'ond )%ick(y eno%gh "o ra'id(y changing in'%" signa(s. Since a significan" amo%n" of m%sic consis"s of ra'id s"ar"ing and s"o''ing signa(s< "he "ransien" res'onse< "he abi(i"y of s'eaker "o re'rod%ce )%ick changes< s%ffers. his is es'ecia((y "r%e of highfre)%ency signa(< +hich in&o(&e )%icker changes in "he signa(. !no"her dra+back is "ha" highfre)%ency s'eakers are &ery direc"iona(. hey ac" a(mos" as a s'o"(igh" and direc" so%nd in a narro+ beam. his crea"es a ?s+ee" s'o"@ for "he s'eaker< o%"side of +hich "he fre)%ency res'onse de"eriora"es. !("ho%gh for cer"ain a''(ica"ions "his direc"iona(i"y is desirab(e< i" means "ha" on(y one (is"ener or a sma(( gro%' +o%(d be ab(e "o hear "he a%dio signa(s re'rod%ced fai"hf%((y. he '(asma "+ee"er 'ro&ides a so(%"ion "o bo"h of "hese 'rob(ems. P(asma "+ee"ers crea"e so%nd by mod%(a"ing "he radi%s of a s'here of ioni;ed air ca((ed a corona. -hanging "he si;e of "he corona ca%ses osci((a"ions in "he air aro%nd i" and crea"es so%nd. Since "he corona is a '(asma f(ame ins"ead of me"a( and fabric< i" does no" s%ffer "o near(y "he same eA"en" from iner"ia( effec"s as con&en"iona( s'eakers. $"s "ransien" res'onse is near(y 'erfec". !ddi"iona((y< "he corona ac" as an omnidirec"iona( 'oin" so%rce +hen genera"ing so%nd BCoye< '1#. 2here&er yo% s"and
1
aro%nd "he s'eaker< in a(( "hree dimensions< yo% recei&e "he o'"ima( fre)%ency res'onse of "he s'eaker.
2.2 - Our plasma tweeter vs. other plasma tweeters produced
8i&en "he ad&an"ages of "he '(asma "+ee"er< i" is no s%r'rise "ha" many 'rod%c"ion mode(s eAis". Eo+e&er< "he reason "ha" "he "echno(ogy has no" been +ide(y %"i(i;ed is a combina"ion of i"s 'rohibi"i&e cos" and high main"enance. Mos" 'rod%c"ion '(asma "+ee"ers "o da"e %se &ac%%m "%be "echno(ogy +hich adds "o "he eA'ense< main"enance re)%iremen"s< and 'o+er cons%m'"ion of "he s'eaker. *%r goa( in "his 'ro=ec" +as "o make a '(asma "+ee"er o%" of so(ids"a"e com'onen"s. his main"ains "he idea(i"ies of "he s'eaker +hi(e red%cing "he cos"s drama"ica((y. he (o+er 'o+er cons%m'"ion and red%ced hea" genera"ion afforded by "he %se of so(ids"a"e com'onen"s is ano"her ad&an"age.
2.3 - Overview of our design with block diagram
igure 1 – Block diagram of system
#
*%r "+ee"er sys"em consis"s of fo%r main %ni"s Big%re 1. he f(ame con"ro( %ni" con"ro(s "he f(o+ of c%rren" in"o "he corona. he f(ame mod%(a"ion %ni" de"ermines "he fre)%ency a" +hich 'o+er is s%''(ied "o "he corona. 8e""ing "he righ" fre)%ency is a cri"ica( s"e' in making '(asma. ! high 'o"en"ia( gradien" is needed "o make '(asma. o crea"e "his gradien"< +e %se a resonan" coi( +i"h high F. he coi( ac"s simi(ar(y "o a "es(a coi( and '(asma is crea"ed a" a shar'ened "i' a" one end. 2hen +e hi" "he resonan" fre)%ency< "he "i' is a" a 'o"en"ia( of be"+een #0 and 30 kG and "he '(asma is crea"ed. o de"ermine "he righ" fre)%ency< "he f(ame mod%(a"ion %ni" has feedback coming from "he corona. ! ha(f circ(e of +ire s%rro%nds and is ca'aci"i&e(y co%'(ed "o "he corona. he signa( from "he feedback (oo' (e"s %s kno+ "he fre)%ency a" +hich "he corona osci((a"es< +hich is "he resonan" fre)%ency of "he coi(. 2hen "he "+ee"er is "%rned on< a s%dden im'%(se en"ers "he coi( and "he coi( na"%ra((y osci((a"es a" i" "he resonan" fre)%ency for a sma(( 'eriod of "ime. D%ring "his "ime< "he f(ame mod%(a"ion %ni" 'icks %' "he signa( and comm%nica"es "he resonan" fre)%ency "o "he f(ame con"ro( %ni"< osci((a"ing "he '(asma a" "he correc" fre)%ency and kee'ing i" going. $n addi"ion "o main"aining "he correc" fre)%ency for "he coi(< "he f(ame mod%(a"ion %ni" a(so mod%(a"es "he si;e of "he f(ame based on a signa( in'%". his in'%" may be connec"ed "o an a%dio de&ice "ha" may or may no" be 'assed "hro%gh a 'ream' s"age. he 'ream' s"age am'(ifies "he c%rren" from a%dio de&ices and has a high 'ass fi("er "ha" se(ec"s "he higher fre)%encies a" +hich "he '(asma +orks bes". he 'o+er s%''(y %ni" 'o+ers "he coi( and as +e(( as "he circ%i"ry in "he o"her %ni"s.
3
3 - Power Su%%l& he 'o+er s%''(y for "he '(asma "+ee"er ser&es as a high &o("age s%''(y for "he resonan" coi(< and (o+ &o("age rai(s for "he $->s and (ogic (e&e( circ%i"ry. o"h s%''(ies %se a simi(ar bridge rec"ifier sys"em Big%re #. or "he (o+ &o("age s%''(ies< "he cen"er "a' of "he "ransformer o%"'%" +as "ied "o gro%nd< "o a((o+ bo"h 'osi"i&e and nega"i&e rai(s. o achie&e a higher &o("age on "he 'osi"i&e high &o("age rai(< "he nega"i&e rai( +as "ied "o gro%nd. he iso(a"ion "ransformer o%"'%"s "he same &o("age as "he +a(( o%"(e"s< b%" a((o+s %s "o reference an arbi"rary gro%nd. 2i"h an in'%" of 1#0G RMS< "his rec"ifier a((o+s %s a D- &o("age of 140G< s%fficien"(y (arge "o 'rod%ce "he '(asma corona.
170V !C
470uF 250V
470uF 250F
4N4004
Isolation Transformer 120V 60Hz - 120V 2A
7812
12V
AC
1000uF 50V
7805
5V
7"12
-12V
7"05
-5V
100uF 50V 1N4001
120V 60Hz - 28V 2A
igure 2 – Power supply schematics
,
4 - Corona Control he cen"er of "he '(asma "+ee"er is "he corona< a sma(( f(ame of ioni;ed air. $"s osci((a"ions 'rod%ce "he so%nd< so being ab(e "o s%s"ain a corona is "he firs" s"e' in b%i(ding "he "+ee"er. he f(ame con"ro( sys"em ens%res "ha" "he coi( is osci((a"ing a" "he 'ro'er fre)%encies "o 'rod%ce '(asma. he mos" s"riking "hing abo%" "he corona sys"em is "he resonan" coi(. he coi( is connec"ed on(y a" one end< +i"h "he o"her end (ef" free in "he air. he corona f(ame is emi""ed from "he free end< a sing(e 'oin" s'ark arcing in"o "he air. he f(ame is "he res%(" of "he high &o("age a" "he coi( "i'< +hich ca%ses "he s%rro%nding air "o break do+n in"o ions< forming a 'a"h "o gro%nd< +here gro%nd is a 'oin" of ;ero 'o"en"ia( +i"h regard "o "he "i'< and no" necessari(y an ear"h gro%nd. o reach s%ch a high 'o"en"ia(< +e need a &ery highF fi("er. or "he '(asma "+ee"er< "he se(fresonance of "he coi( is "his fi("er. he coi( can be considered as a series R- circ%i" Big%re 3: #
$
Vin
Vout C
igure 3 – RLC model of coil
he ind%c"ance is "he ind%c"ance of "he coi(< and "he resis"ance is "he resis"ance in "he +ire of "he coi(. he ca'aci"ance< ho+e&er< is "he res%(" of m%("i'(e fac"ors. $n sma(( coi(s< "he se(fresonance is d%e "o ca'aci"ance be"+een ad=acen" "%rns of +ire. Eo+e&er< "his ca'aci"ance +o%(d be""er be mode(ed by ha&ing "he ca'aci"or in 'ara((e( +i"h "he ind%c"or and resis"or Big%re ,: #
$
Vin
Vout
C
igure ! – RLC model of small coil
5
his sys"em does no" dis'(ay "he se(fresonan" 'ro'er"ies "ha" "he ac"%a( coi( does. he ca'aci"ance< ins"ead< can be a""rib%"ed "o "he ca'aci"ance be"+een "he "i' of "he coi( and "he res" of "he %ni&erse. !" "he "i' of "he coi(< "here are a (arge n%mber of 'a"hs "o gro%nd "hro%gh "he air< and "hese 'a"hs crea"e a cer"ain ca'aci"ance be"+een "he "i' of "he coi( and "he s%rro%ndings. his ca'aci"ance "o gro%nd ca%ses "he coi( "o resona"e< +i"h a (arge am'(ified o%"'%" a" "he resonan" fre)%ency. he "ransfer f%nc"ion of "his sys"em from Gin "o Go%" can be +ri""en as: V out V in
1
B sD =
Cs
Ls + R +
1 Cs
=
1 LCs
#
+ RCs +
1
B1
he fo((o+ing gra'h is "he ode Bmagni"%de and 'hase '(o" for "his sys"em B%sing reasonab(y "y'ica( &a(%es:
rom "he ode '(o"< i" is c(ear "ha" "he coi( has a &ery "a((< shar' resonance 'eak. his 'eak is de'enden" on "he ca'aci"ance of "he "i'< and so is no" a" a fiAed &a(%e. Moreo&er< once "he '(asma
6
has s"ar"ed< "he ca'aci"ance is changed< +hich changes "he fre)%ency of resonance. his makes i" im'ossib(e "o dri&e "he coi( +i"h a fiAed fre)%ency osci((a"or. ! feedback sys"em +as %sed "o dri&e "he coi( a" i"s resonan" fre)%ency:
170V 100uH $F )'o*e
$esonant Coil
100% li&'t (ul( )urrent limiter
F+,2N"0
ate !ri.er /C710
5 o'm %
100*
igure " – Flame control schematics
he (oo' aro%nd "he coi( "i' Big%re 5< %''er righ" is a sim'(e (oo' o f +ire< going aro%nd "he coi( "i' and disconnec"ed a" one end< +hich is ca'aci"i&e(y co%'(ed "o "he "i' Bsho+n abo&e as do""ed. he FF#70 is a 'o+er M*S9< ra"ed for 00G maAim%m GDS< 5 2 'o+er dissi'a"ion B+hen %sed +i"h a hea"sink< and a ga"e charge of 1# n-. ! sma(( ga"e charge is re)%ired for fas" s+i"ching< as "he resonan" fre)%ency of "he coi( is in "he range of 5 10 ME;. 2hen "he s'eaker is "%rned on< "he coi( recei&es a 140G s"e'< ca%sing i" "o resona"e a" i"s na"%ra( fre)%ency. 2i"ho%" "he feedback sys"em< "his osci((a"ion +o%(d decay %n"i( "he coi( reached a s"eady &o("age of 140 G. $ns"ead< "he feedback (oo' 'icks %' "he osci((a"ions< ca%sing "he ga"e dri&er "o dri&e "he M*S9. he ga"e dri&er< +hich can s%''(y %' "o !< is re)%ired "o )%ick(y charge "he ga"e of "he M*S9< o&ercoming "he ga"e ca'aci"ance. 2hen "he M*S9 is s+i"ched on< i" shor"s "he in'%" of "he coi( "o gro%nd. 2hen s+i"ching a" "he resonan" fre)%ency< "he in'%" "o "he coi( becomes a s)%are +a&e a" "he resonan" fre)%ency. !s a high(y se(ec"i&e fi("er< "he coi( 'asses on(y "he firs" f%ndamen"a( fre)%ency< i"s resonan" fre)%ency. he o%"'%" is a high(y am'(ified sin%soid< +hich can reach am'(i"%des on "he order of 10<000G. $" is diffic%(" "o meas%re "his &o("age direc"(y< as any 'robe 'ro&ides an addi"iona( 'a"h "o gro%nd < by'assing "he
4
ca'aci"ance of "he "i'. Eo+e&er< "he &o("age of "he feedback +ire can reach am'(i"%des of o&er 500G. he &o("age a" "he "i' is eno%gh "o ca%se "he s%rro%nding air "o break do+n in"o ions< forming "he corona of '(asma. here are "imes +hen "he s'eaker +i(( "%rn on< ye" "he f(ame +i(( no" form. $n s%ch a case< "he coi( is s"i(( resona"ing a" high &o("ages< b%" "he "i' is no" a high eno%gh &o("age "o ini"ia"e "he '(asma corona. his can be d%e "o &arying condi"ions in "he air< a 'oor 'oin" on "he coi( "i'< or being s(igh"(y off "he resonan" fre)%ency. $n s%ch a case< i" is re)%ired "o s"ar" "he f(ame man%a((y by "o%ching "he "i' of "he coi( brief(y +i"h scre+dri&er. !" 5ME;< "he scre+dri&er ac"s as a 'a"h "o gro%nd "ha" is easier "o arc "o "han "he s%rro%nding air. he '(asma arcs "o "he "i' of "he scre+dri&er< forming a 'a"h for "he '(asma "o eA"end from. his ini"ia( barrier co%(d be o&ercome by %sing an im'%(se of &o("age "hro%gh "he coi(< raising "he "i' &o("age eno%gh "o ini"ia"e "he corona. *nce s"ar"ed< "he &o("age re)%ired "o s%s"ain "he corona is (o+er< s%ch "ha" "he ini"ia( osci((a"ions are eno%gh "o kee' "he '(asma going.
5 - 'a(ing Sound *nce a s"eady corona is formed< "he neA" s"e' is "o osci((a"e i" "o make so%nd. y changing "he heigh" of "he corona< i" eAer"s 'ress%re on "he s%rro%nding air< res%("ing in a 'oin" so%rce of so%nd. he so%nd radia"es in a(( direc"ions< in con"ras" "o con&en"iona( "+ee"ers< +hich %se a cone< 'rod%cing a high(y direc"iona( so%nd. he f(ame is a(so essen"ia((y mass(ess< ha&ing "he same densi"y of "he air i" is mo&ing. his crea"es a &ery c(ear< '%re so%nd< +i"ho%" "he direc"iona(i"y of s"andard "+ee"ers. !(( me"hods of 'rod%cing so%nd re&o(&e aro%nd changing "he heigh" of "he f(ame. his is done by changing "he &o("age a" "he "i' of "he coi(. y changing "he &o("age< +e change "he 'o"en"ia( a" "he "i'< and "h%s "he dis"ance of "he 'a"h "ha" m%s" be ioni;ed "o reach a gro%nd 'o"en"ia(. here are se&era( +ays "o change "he &o("age a" "he "i'< some more 'rac"ica( and s%ccessf%( "han o"hers. $n -o(in Coye>s 9based '(asma "+ee"er< he o&er(aid "he a%dio signa( +i"h "he high &o("age rai( dri&ing "he coi(. y am'(ifying his a%dio and o&er(aying i" on"o "he D- rai( +i"h a "ransformer< he +as ab(e "o &ary his high &o("age rai( a" a%dio fre)%encies. his &aried "he am'(i"%de of "he s)%are +a&e dri&ing "he coi(. he am'(i"%de mod%(a"ion +as a" a m%ch (o+er
fre)%ency "han "he fre)%ency of "he s)%are +a&e< so "ha" i" did no" disr%'" "he resonan" 'eak of "he coi(. his me"hod< a("ho%gh s%ccessf%(< re)%ires (arge am'(ifica"ion of "he a%dio signa(< as +e(( as co%'(ing "hro%gh a "ransformer< +hich is an added eA'en se for "he s'eaker. !no"her 'ossib(e me"hod "ha" +as s%gges"ed +as "o mod%(a"e "he araday cage aro%nd "he "i' of "he coi(. Since "he araday cage is ac"ing as a gro%nd "o "he "i' of "he coi(< changing i"s &o("age +o%(d change "he 'o"en"ia( be"+een "he "i' and gro%nd. his +o%(d re)%ire mod%(a"ing "he cage a" high &o("ages< on "he order of 1<000 G. he idea of ha&ing a s%''osed(y gro%nded shie(d osci((a"ing +i"h a%dio fre)%ency a" "ha" high a &o("age did no" a''ea( "o %s< bo"h for safe"y concerns and noise emissions. he firs" a""em'" "o osci((a"e "he '(asma in&o(&ed %sing '%(se +id"h mod%(a"ion "o dri&e "he M*S9 ga"e. y &arying "he d%"y cyc(e of "he signa( dri&ing "he ga"e< +e co%(d &ary "he &o("age in'%" "o "he coi(. his sys"em in&o(&ed synchroni;ing "he feedback signa( +i"h "he ga"e signa( by %sing a P< "o com'ensa"e for "he de(ay "hro%gh "he circ%i". 2hi(e conce'"%a((y so%nd< "he im'(emen"a"ion seemed c(ose "o im'ossib(e d%e "o in"erference from "he osci((a"ing coi(. he fina( sys"em %sed in&o(&ed mani'%(a"ing "he de(ay inheren" in "he feedback (oo'< ins"ead of "rying "o remo&e i". y 'assing "he signa( "hro%gh a b%ffer< +e co%(d change "he de(ay "hro%gh "he b%ffer< and "hereby change s(igh"(y "he osci((a"ing fre)%ency "ha" dro&e "he coi(. his sys"em is "he one "ha" +as fina((y im'(emen"ed "o 'rod%ce so%nd in o%r s'eaker.
".1 - lame #odulations $sing %&& and %'#
$n "his design of "he '(asma "+ee"er< "he f(ame mod%(a"ion %ni" is com'osed of a P s"age and a P2M s"age. he a%dio signa( is in'%""ed "hro%gh "he P2M s"age +here "he am'(i"%de of "he signa( is "rans(a"ed in"o "he d%"y cyc(e of "he c%rren" 'o+ering "he corona. he higher "he am'(i"%de< "he (arger "he d%"y cyc(e< "he bigger "he f(ame. Eo+e&er< "o com'ensa"e for "he 'hase changes in&o(&es in "he circ%i"ry< a P s"age is %sed. he P "akes in'%" from "he corona and from "he f(ame con"ro( %ni".
igure ( – Block diagram of PLL/PW modulation system
5)1)1 - P*ase +o#(ed +oo%
*%r firs" idea +as "o %se a 'hase(ocked (oo' BP "o dri&e "he osci((a"or a" a fiAed 'hase B"h%s a fiAed fre)%ency. 2e +o%(d a(so mod%(a"e "he +id"h of "he dri&ing '%(ses "o ad=%s" "he "iming of "he c(ass9 s+i"ching +a&eform. his '%(se+id"h mod%(a"ion BP2M +o%(d change "he am'(i"%de of "he f%ndamen"a( fre)%ency a" "he in'%" "o "he coi(. he f(ame heigh" +o%(d "h%s be changed dynamica((y.
170V
100uH $F )'o*e
$esonant Coil
100% li&'t (ul( )urrent limiter Auio in
A!8561
-)s3
HC4046
F+,2N"0 -ate !ri.er /C710
5 o'm %
VC
100*
#612
igure ) – !chematic of PLL/PW modulation system
10
he P circ%i"ry consis"s of a 'hase com'ara"or< a com'ensa"or ne"+ork< and a &o("age con"ro((ed osci((a"or BG-*. he 'hase com'ara"or is "y'ica((y an H*R ga"e or a simi(ar circ%i". $" o%"'%"s a s)%are +a&e +i"h a d%"y ra"io 'ro'or"iona( "o "he 'hase difference be"+een "he "+o in'%"s. he com'ara"or ne"+ork is 'rimari(y a (o+'ass fi("er "o fi("er "he '%(ses from "he 'hase com'ara"or "o gi&e a s(o+(ychanging signa( "ha" re'resen"s 'hase. he com'ensa"or a(so se"s "he dynamics and s"abi(i"y of "he feedback (oo'. he com'ensa"or can be ei"her 'assi&e Bresis"ors and ca'aci"ors or ac"i&e Bo'am's '(%s 'assi&e com'onen"s. ina((y< "he G-* "akes "he o%"'%" of "he com'ensa"or ne"+ork and 'rod%ces a s)%are+a&e +i"h a fre)%ency direc"(y re(a"ed "o "he in'%" &o("age. 2e res"ric" "he range of "he G-* "o inc(%de on(y a sma(( fre)%ency band aro%nd "he na"%ra( fre)%ency of "he coi(. h%s< +e are ab(e "o a&oid (ocking on "o ra"iona( m%("i'(es of "he na"%ra( fre)%ency. he o%"'%" from "he G-* is fed "o "he P2M sys"em "o add in "he a%dio. Eo+e&er< in o%r im'(emen"a"ion< +e had "oo m%ch d iffic%("y ge""ing a c(ean signa( from "he 'hase com'ara"or. he na"%re of "he H*R ga"e made "he o%"'%" ha&e 50I d%"y ra"io if "he in'%" is 0 degrees o%" of 'hase< or if one in'%" is a(+ays ;ero. h%s< i" is diffic%(" "o (ock on "o "he 0 degrees 'hase difference.
5)1)2 - Pulse ,idt* 'odulation
he s)%are +a&e in'%" "o "he ga"e dri&er de"ermines "he fre)%ency a" +hich "he M*S9 s+i"ches and "he amo%n" of "ime 'er cyc(e "ha" is on. 2hen "he 9 is on< "he resonan" coi( recei&es no c%rren". herefore "he d%"y cyc(e of "he 9 de"ermines ho+ m%ch 'o+er is going "o "he coi( and< as a res%("< ho+ big "he '(asma f(ame is. -hanging "he si;e of "he '(asma f(ame is "he mechanism by +hich "he "+ee"er 'rod%ces so%nd. y mod%(a"ing "he d%"y cyc(e of "he s)%are +a&e in'%" "o "he ga"e dri&er +e can con"ro( "he so%nd o%"'%" of "he "+ee"er. o do "his +e %sed '%(se +id"h mod%(a"ion BP2M.
11
igure * – Pulse Width odulation using a comparator
! com'ara"or com'ares "he a%dio in'%" "o a "riang(e +a&e. he fre)%ency of "he "riang(e +a&e de"ermines "he fre)%ency of "he s)%are +a&e o%"'%" and m%s" be "he same fre)%ency as "he resonan" coi(. Since "he resonan" fre)%ency is abo%" 5 ME;< a fas" com'ara"or is needed. $n o%r case< +e %sed "he !D561. he a%dio in'%" is a" "he m%ch (o+er fre)%ency. 2hen "he a%dio signa( is high< i" is a" a higher &o("age "han "he "riang(e +a&e for a grea"er 'ercen"age of "he cyc(e and res%("s in a s)%are +a&e o%"'%" +i"h a (arge d%"y cyc(e. 2hen "he a%dio signa( is (o+< "he d%"y cyc(e of "he o%"'%" is sma((er. o"h in'%"s "o "he com'ara"or are biased "o #.5G< so "ha" a gro%nded in'%" +i(( 'rod%ce a 50I d%"y cyc(e. 7o"e "ha" e&en "ho%gh "he '(asma f(ame f(ickering a" a fre)%ency of abo%" 5ME;< "his is far beyond "he range of hearing. 2ha" +e can eA'ec" "o hear are "he a%dio fre)%ency mod%(a"ions of "he '(asma "ha" are ca%sed by "he changes in "he d%"y cyc(e of "he P2M o%"'%". he neA" s"e' af"er +e had decided on +hich com'ara"or "o %se +as "o find a +ay "o crea"e "he "riang(e +a&e in'%". he "riang(e +a&e is crea"ed %sing "he s)%are +a&e o%"'%" of "he P "ha" is a(ready ma"ched "o "he resonan" fre)%ency of "he coi(. he sim'(es" and mos" con&en"iona( choice is "o %se an o' am' in"egra"or "o crea"e "he "riang(e +a&e. his +as im'(emen"ed as sho+n in "he diagram be(o+. nfor"%na"e(y "his circ%i" did no" (i&e %' "o eA'ec"a"ions. he o' am' +o%(d no" +ork +e(( a" high fre)%encies. he "riang(e +a&e genera"ed a" 5 ME; +as no" 're""y. !(so< i" +as 'rone "o being dis"%rbed by "he in"erference crea"ed by "he '(asma "+ee"er. he o%"'%" +as a(mos" a(( noise +hen %sed in "he "+ee"er circ%i"< and "ho%gh be""er shie(ding migh" ha&e he('ed< e&en "he bes" case res%(" from "he o' am' "riang(e +a&e genera"or +as no" idea(.
1#
igure + – PW circuit using an op"amp integrator to create the triangle wa#e
2e decided +e needed ano"her +ay "o genera"e "riang(e +a&es. he me"hod +e decided on re(ies on a P7P and an 7P7 "ransis"or and a ca'aci"or connec"ed as sho+n in "he diagram.
igure 1, – PW circuit using P$P and $P$ transistors to create the triangle wa#e
he P7P "ransis"or has i"s base connec"ed "o gro%nd "hro%gh a 'o"en"iome"er. he 'o"en"iome"er de"ermines "he amo%n" of c%rren" "ha" 'asses "hro%gh "he co((ec"or of "he P7P.
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2hen "he 7P7 be(o+ is off< "he c%rren" charges %' "he ca'aci"or< crea"ing "he (inear< 'osi"i&e s(o'e ram' "ha" makes %' ha(f of "he "riang(e +a&e. he 7P7 "ransis"or is off +hen "he o%"'%" of "he P sec"ion is (o+. 2hen i">s high< c%rren" from "he P7P>s co((ec"or and "he ca'aci"or 'ass "hro%gh "he 7P7>s emi""er "o gro%nd. he cri"ica( 'ar" of "his circ%i" is "o make s%re "ha" "he c%rren" 'assing "hro%gh "he 7P7 +hen i">s on is e)%a( "o "+ice "he c%rren" 'assing "hro%gh "he P7P. 2hen "ha" ha''ens< a(( of "he c%rren" from "he P7P 'asses "hro%gh "he 7P7 and "he ca'aci"or discharges com'(e"e(y. !gain< since "he c%rren" is f(o+ing from "he ca'aci"or a" a cons"an" ra"e< a (inear< nega"i&e s(o'e ram' is crea"ed< forming "he o"her ha(f of "he "riang(e +a&e. he c%rren" "ha" f(o+s "hro%gh "he 7P7 "ransis"or +hen i" is on is con"ro((ed by ano"her 'o"en"iome"er connec"ed be"+een i"s base an d "he P o%"'%". his is ad=%s"ed %n"i( a "riang(e +a&e is crea"ed. sing "his me"hod< +e made a reasonab(y c(ean +a&eform "ha" +orks a" "he high fre)%encies re)%ired and "o(era"es "he high (e&e(s of in"erference from "he "+ee"er. 7one"he(ess< +e +ere no" ab(e "o mod%(a"e f(ame %sing "he P/P2M design. he sys"em is com'(eA for "he high fre)%ency and high F demands +e '%" on i". $" is more s%sce'"ib(e "o noise "han a sim'(er sys"em. D%e "o a(( of "hese fac"ors< i" +as no" ab(e "o +ork in "he '(asma "+ee"er sys"em and i" +as "oo com'(eA "o deb%g in "he "ime a&ai(ab(e. !no"her me"hod of f(ame mod%(a"ion +as needed.
".2 - elay #odulation
2i"h "he diffic%("y in %sing "he 'hase(ocked (oo' "o dri&e "he ga"e +i"h a '%(se +id"h mod%(a"ed signa(< +e needed "o find an a("erna"i&e so(%"ion. $n o%r mee"ing +i"h Coe So%sa< an engineer for inear echno(ogies< he no"iced "ha" "he ga"e dri&er added a significan" de(ay "o "he feedback (oo'. Ee s%gges"ed "ha" +e "ry &arying "he de(ay "hro%gh "he feedback (oo'< "o change s(igh"(y "he fre)%ency "ha" +as dri&ing "he coi(. -onsider "he ode '(o" of "he fre)%ency res'onse of "he resonan" coi(. !" (o+ fre)%encies< "he ca'aci"or is an o'en circ%i"< so "he o%"'%" is e)%a( "o "he in'%" +i"h ;ero 'hase de(ay. !" higher fre)%encies< "he sys"em becomes a secondorder (o+'ass fi("er +i"h 10 degrees 'hase< corres'onding "o a 10 degree (ag. !" resonance< "he 'hase shif" is 0 degrees. h%s< "he &o("age a" "he "i' Bo%"'%" is 0 degrees Bor J 'eriod behind "he in'%" &o("age. ig%re
1,
11 is a gra'h of "he magni"%de of "he "ransfer f%nc"ion B"he gain "hro%gh "he coi( &ers%s "he 'hase:
igure 11 – Coil tip gain #s% tip to drain phase lag
he magni"%de of "he res'onse a" "he coi( "i' changes in res'onse "o "he 'hase. Eo+e&er< %n(ike "he narro+ 'eak in "he bode '(o"< "his c%r&e is more +e((beha&ed "he res'onse changes s(o+(y +i"h a change in 'hase. $n addi"ion< "his c%r&e on(y sca(es &er"ica((y as "he 'arasi"ic resis"ance Ba(so F< "he )%a(i"y fac"or changes.
igure 12 – !chematic of delay modulation
he abo&e schema"ic i((%s"ra"es "he coi( dri&ing "o'o(ogy +i"h a(( "he con"ro( e(emen"s gro%'ed in"o "he ?de(ay@ b(ock. 7eg(ec"ing "he feedback (oo'< "his is "he "o'o(ogy of a c(ass9 R"y'e am'(ifier. or a "y'ica( c(ass9 am'(ifier< "he a''roAima"e s+i"ching +a&eforms Bfor one 'eriod are sho+n be(o+ Big%re 13:
15
igure 13 – &raph of switching wa#eform for '!F() gate
he GA +a&eform is no" eAac"(y 10 degrees a'ar" from "he ga"e dri&e &o("age d%e "o "he 'ec%(iari"ies of "his circ%i"< b%" for "his ana(ysis< +e +i(( ass%me "ha" i" is 10 degrees off.
Since "he ga"e is dri&en by a signa( based on feedback< "here is a re(a"ionshi' re(a"ing "he o&era(( 'hase de(ay of "he sys"em. Regard(ess of "he de(ay in "he feedback (oo'< "he ga"e dri&e '%(se is a(+ays 10 degrees a+ay from "he GA '%(se. here is a 10 degree de(ay be"+een a '%(se in GA and "he fo((o+ing ga"e '%(se. his de(ay comes from "he s%m of "he de(ay "hro%gh "he resonan" coi( and "he de(ay "hro%gh "he feedback (oo' circ%i"ry B"he de(ay b(ock. h%s< if "he feedback circ%i"ry and ga"e dri&er ha&e no de(ay< "he resonan" coi( m%s" o'era"e a" 10 degrees. rom "he abo&e gain'hase '(o"< "he gain of "he sys"em is &ery (o+ a" 10 degrees. $f "he circ%i"ry adds a de(ay of 0 degrees< "he coi( +o%(d o'era"e a" a 'hase shif" of 0 degrees< i"s resonan" 'oin". ! de(ay of 0 degrees corres'onds "o 50 ns a" 5 ME;. Garying "he de(ay aro%nd "his o'era"ing 'oin" +o%(d change "he o'era"ing 'hase of "he coi(< "h%s mod%(a"e "he o%"'%" am'(i"%de. 2e +an" "o mod%(a"e "he de(ay "hro%gh "he feedback (oo' "o dynamica((y change "he 'hase in "he coi(. h%s< +e +an" a com'onen" +i"h a sma(( b%" high(y&ariab(e de(ay. Coe So%sa
16
s%gges"ed %sing a highs'eed -M*S in&er"er Bs%ch as a 4,E-0, or 4,E-0, as "his de(ay. he de(ay "hro%gh "he ga"e is direc"(y re(a"ed "o "he s%''(y &o("age on "he ga"e. Eere are "he de(ays from $>s -D4,E-0, in&er"er:
Gdd: "'d< maA
#G 40 ns
,.5 G 1, ns
6G 1# ns
-M*S in&er"ers consis" of a com'(emen"ary M*S9 'air< +here "he P and 7channe( M*S9s are in a series "o"em'o(e config%ra"ion. $n m%("i'(es"age in&er"er chains< de(ay is ca%sed by "he charging of "he ga"e ca'aci"ance "hro%gh "he ons"a"e resis"ance of "he M*S9s in "he 're&io%s s"age. !" (o+er s%''(y &o("ages< (ess c%rren" f(o+s "hro%gh "he ons"a"e resis"ance< so "he ca'aci"ance of "he neA" s"age "akes (onger "o charge %'. h%s< "he de(ay "hro%gh "he chain increases as s%''(y &o("age dro's. Coe So%sa s%gges"ed "he fo((o+ing circ%i" "o %se "o mod%(a"e "he s%''(y &o("age on "he in&er"er: 5V
1N4001
100 o'm
47 uF Auio in 22 nF
74HC/04
igure 1! – !chematics of #aria*le delay *uffer
he 100 ohm resis"or is %sed "o 'ro&ide a D- c%rren" "o "he in&er"er< and is a(so %sed "o b ias "he in'%" signa(. ! (arge B,.4 % ca'aci"or is %sed "o co%'(e "he a%dio signa( "o "he 'o+er rai( of "he in&er"er. ! sma((er #.#n ca'aci"or is %sed "o by'ass "he s%''(y a" "he s+i"ching fre)%ency of 5 Mh;.
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2hen "es"ing "his circ%i" Borigina((y +i"ho%" "he diode chain< i" +o%(d +ork fine +i"ho%" an a%dio in'%". Eo+e&er< +hen a (o+im'edance o%"'%" +as connec"ed "o "he a%dio in'%"< "he coi( +o%(dn>" osci((a"e. 2e a""rib%"ed "he 'rob(em "o "he (ong R- de(ay d%e "o "he 100 ohm resis"or and "he (arge co%'(ing ca'aci"or. his R- "ime cons"an" mean" "he in&er"er "ook a (ong "ime "o s"ar" %'< disab(ing "he feedback (oo' %n"i( (ong af"er "he ini"ia( osci((a"ion died o%". 2e added "he diode chain "o by'ass "he 100 ohm resis"or +hen "he s%''(y of "he in&er"er +as s%fficien"(y be(o+ 5 Go("s. 2hen "he s%''(y reached 5G min%s "hree diode dro's< "he diodes sh%" off< and "he s%''(y co%(d be mod%(a"ed norma((y by "he in'%" signa(. he 'air of in&er"ers +as %sed< ins"ead of a sing(e in&er"er< "o a((o+ %s "o con"in%e "o %se "he nonin&er"ing in'%" of "he ga"e dri&er. 2hen %sing "he sing(e in&er"er and "he in&er"ing "ermina( of "he ga"e dri&er< +e fre)%en"(y des"royed o%r M*S9. his occ%rred +hen "he in&er"ers did no" recei&e eno%gh 'o+er ini"ia((y< ca%sing "he in&er"er "o o%"'%" (o+ regard(ess of in'%"< beca%se i" did no" ha&e a higher rai( "o o%"'%". he (o+ signa( "o "he in&er"ing in'%" of "he ga"e dri&er forced i" "o "%rn on "he M*S9< shor"ing "he high &o("age rai( "hro%gh "he M*S9. he (arge c%rren" f(o+ing "o gro%nd +o%(d "%rn on "he (igh" b%(b Ba sign "ha" some"hing +as +rong< as +e(( as o&erhea"ing and des"roying "he M*S9. his co%(d be remedied by a M*S9 ca'ab(e of 'assing higher c%rren"s< or more sim'(y by %sing "he d%a( in&er"er s"age as a b%ffer< s%ch "ha" if i" did no" recei&e 'o+er< "he M*S9 +o%(d sim'(y remain off.
6 - S*ielding and $nterferen#e 'ic"%re of araday cage< +i(( "ake "onigh" B5/1,/03 SKL
he resonan" coi( and corona "oge"her crea"e a (o" of in"erference. he 'o"en"ia( gradien" crea"ed by "he "+ee"er is s"rong eno%gh "o 'o+er a f(%orescen" (igh" b%(b "+o or "hree fee" a+ay. he signa( is s"rong eno%gh "o be make a -D '(ayer s"o' +orking and "o be 'icked %' by f(oa"ing osci((osco'e (eads many me"ers a+ay from "he "+ee"er. Shie(ding and designing circ%i"ry "ha" is no" affec"ed s"rong(y by in"erference +as an essen"ia( e(emen" of o%r 'ro=ec"< "ho%gh +e had many se"backs on "he +ay. he f(ame con"ro( and f(ame mod%(a"ion circ%i"s +ere shie(ded in a gro%nded me"a( boA< +hich seemed "o be
1
s%fficien" in o%r fina( design. *"her e(emen"s of "he '(asma "+ee"er (ike "he 'ream' circ%i"ry and one of "he i"era"ions of "he P2M s"age s%ffered from in"erference iss%es e&en +hen '(aced in "he shie(ded con"ainer. *ne so(%"ion +e "ried +as "o make a faraday cage "o '(ace aro%nd "he corona. 2e made a s'herica( cage o%" of "+o &ege"ab(e s"rainers. Eo+e&er< +hen '(aced aro%nd "he cage< "he f(ame made %ndesirab(e hissing so%nds. his si;e and 'roAimi"y of "he gro%nded cage "o "he '(asma +as mos" (ike(y "he ca%se of "he hissing. !no"her so(%"ion +as "o shie(d "he coi( i"se(f. Eo+e&er< +hen "he shie(d +as in '(ace< no '(asma co%(d be crea"ed. his +as 'erha's beca%se "he shie(d +as dra+ing 'o+er from "he coi( and no" eno%gh remained "o s"ar" "he f(ame. *%r "ime cons"rain"s (imi"ed %s "o shie(ding "he '(asma "+ee"er eno%gh so "ha" i" co%(d genera"e so%nd based on a%dio signa( in'%". More effec"i&e shie(ding is a sim'(e addi"ion "o o%r 'ro=ec" "ha" +o%(d (ike(y (ead "o im'ro&ed so%nd )%a(i"y. ! (arge me"a( gra"ing co%(d be %sed as a faraday shie(d for bo"h "he coi( and "he '(asma. Making s%re "ha" i" does no" ge" "oo c(ose "o ei"her "he f(ame for "he coi( is "he key and +i(( no" de"rac" from i"s abi(i"y "o shie(d "he com'onen"s. !s +e((< shie(ded +iring going "o "he in'%" a%dio de&ice +o%(d c%" do+n on some of "he noise.
7 - Con#lusion *%r goa( for "his 'ro=ec" +as "o crea"e a so(ids"a"e '(asma "+ee"er "ha" '(ayed a%dio so%nds and "his +e accom'(ished. he main "heme behind o%r designs +as "o make circ%i"s "ha" com'ensa"e for and e&en %se "he nonidea(i"ies of o%r com'onen"s and "ha" are ab(e "o hand(e "he demanding fre)%encies and 'o+er (e&e(s a" +hich "hey o'era"e. *%r fina( design crea"ed a '(asma f(ame abo%" 0.5 cm in diame"er. $" '(ays a%dio signa(s from 1 kE; "o fre)%encies 'as" o%r range of hearing. 8i&en in'%" signa(s from a signa( genera"or< i" crea"es a c(ean so%nd +i"h good high fre)%ency res'onse. he maAim%m &o(%me (e&e( +as reasonab(e "ho%gh no" (o%d. 2i"h in'%" direc"(y from a -D '(ayer "he '(asma "+ee"er '(ayed "he high fre)%ency com'onen"s of "he a%dio a" (o+ &o(%mes.
1
8 Future $m%ro.ements !("ho%gh are ini"ia( mode( +as ab(e "o 'rod%ce so%nds< "here are a (arge n%mber of im'ro&emen"s "ha" co%(d be made. *%r main goa( +as "o 'rod%ce a s'eaker "ha" co%(d be connec"ed "o an a%dio so%rce and 'rod%ce a%dio +i"h i"s o+n am'(ifica"ion. o "his eA"en"< "here are se&era( im'ro&emen"s "o a""ain s%ch 'erformance: •
-rea"e a 'ream' "ha" %ses ba(anced a%dio< s%ch "ha" "here are "+o cab(es< and < +hich carry o''osi"e signa(s. his +o%(d im'ro&e noiseimm%ni"y< as any noise 'icked %' by bo"h cab(es is ignored by commonmode re=ec"ion of "he 'ream'.
•
Re'(ace "he iso(a"ion "ransformer in "he 'o+er s%''(y +i"h a &ariac< a((o+ing a con"ro((ab(e f(ame heigh".
•
!""em'" "o s"abi(i;e and shie(d "he P/P2M %ni"< "o 'rod%ce so%nd &ia o%r origina( me"hod.
•
se a M*S9 +i"h a fas"er s+i"ching "ime "o increase "he dri&ing fre)%ency< "o dri&e a coi( of higher fre)%ency. his +o%(d e(imina"e some of "he s"a"ic 'rod%ced by "he f(ame.
•
e""er shie(d "he f(ame and coi(< "o red%ce in"erference< bo"h +i"hin o%r circ%i" and "o o%"side de&ices.
