obse ed in an o dina y asymme ic e lec i i y DFB lase
wi hou
L/4
phaseshi was due o
a
mode pa i ion be ween
he DFB mode and Fab y-Pe o modes caused by insu icien
AR coa ing a one end o he lase .
So
a TE-TM mode
pa i ion as shown in Fig.
3
has no been obse ed.
In he
44
shi ed DFB lase he h eshold gain di e ence
AaL
among TE modes
o
among TM modes is a ound
0.7
when op imally de~igned,~ i.e.,
KL
is 1.25, while he mode
selec ion be ween TE and TM mode p o ided by he di e -
ence in he coupling coe icien and he mode con inemen
ac o is e y small. Theo e ical calcula ion assuming
a
ec-
angula shaped co uga ion using
a
model by S ei e
e
aL4
showed ha he e was no di e ence in he coupling coe icien
be ween TE and TM modes o he ac i e laye hickness
d,
o
0.15pm. Fo
a
hinne
d,
o
0.1
pm he e was
a
sligh di e -
ence. Howe e , e en in his case, he
AKL
o op imum
KL
o
1.25 was only
0.06,
which co esponded o he h eshold gain
di e ence
AaL
be ween TE and TM mode o only
0.07.
The
di e ence in mode
loss
owing o he mode con inemen ac o
could no be as la ge because o he small abso p ion coe i-
cien o he cladding laye s. The mode selec ion be ween TE
and TM mode in a
1/4
shi ed DFB lase is much smalle han
ha in an o dina y asymme ic e lec i i y DFB lase in which
TE-TM mode selec ion is p o ided by he ace e lec i i y.
Fig.
4
shows he ime a e aged spec a o
a
1/4
shi ed DFB
lase unde modula ion measu ed using a pola ise . We can
iden i y a small ampli ude TM emission. This small ampli ude
TM emission is e idence o TM mode lasing wi h a e y small
p obabili y, o he o de o
IO-’’,
unde modula ion due o
he gain o e shoo .
n
TM
h
I
I
I
wa eleng h,
p
m
1
30
131 132
Fig.
4
Time a e aged spec a unde modula ion
TM spec um was measu ed using
a
Clan-Thompson pola ise
We ha e de eloped a e y-low- h eshold-cu en high-
e iciency
i/4
shi ed DFB lase ha ing bandwid h o
11
GHz.
Howe e , ansmission expe imen e ealed ha he e exis ed
a mode pa i ion be ween TE and TM mode. This mode pa i-
ion is due o a small h eshold gain di e ence be ween TE
and TM mode. To make ull use o he a ac i e ea u e o
he
1/4
shi ed DFB lase , Le., he la ge h eshold gain di e -
ence be ween modes, we mus inco po a e a s ong mode
selec ion mechanism be ween TE and TM mode. This is espe-
cially impo an o a lase o be used in se e al Gbi /s
sys ems unde a di ec modula ion scheme.
The au ho s wish o hank M. Ma suda o his ab ica ion
o he
144
shi ed co uga ions, and
S.
Isozumi, T. Kusunoki,
T. Tanahashi,
H.
Sudo and M. Sugano o hei co-ope a ion
in his wo k. They also wish o hank T. Misugi, M. Kobay-
ashi, and T. Saku ai o hei encou agemen .
H.
ISHIKAWA
K. KAMITE
K. KIHARA
H.
SODA
H.
IMAI
Fuji su Labo a o ies L d.
10-1
Mo inosa o- Wakumiya, A sugi, Japan
496
26 h Feb ua y
1988
Re e ences
ISHIKAWA, H., SODA, H., WAKAO, K., KIHARA, K., KAMITE, K., KOTAKI,
Y.,
MATSUDA,
M.,
SUDO,
H., YAMAKOSHI,
s.,
ISOZUMI,
s.,
and
IMAI,
H.:
‘Dis ibu ed eedback lase emi ing a 1.3 pm o gigabi commu-
nica ion sys ems’,
J.
Ligh wa e Technol.,
1987,
LT-5,
pp. 848-855
KAMITE, K.,
sum,
H., YANO, M., ISHIKAWA, H.,
and
IMAI,
H.:
‘Ul a-
high speed InGaAsP/InP DFB lase s emi ing a 1.3pm wa e-
leng h,
IEEE
J.
Quan um Elec on.,
1987,
QE-23,
pp. 10561058
SODA, H., KOTAKI, Y.,
sum,
H., ISHIKAWA, H., YAMAKOSHI,
s.,
and
IMAI,
H.:
‘S abili y in single longi udinal mode ope a ion in
GaInAsP/InP phase-adjus ed DFB lase s’,
IEEE
J.
Quan um Elec-
on.,
1987,
QE-23,
pp. 804-814
STREIFER,
w.,
SCIFRES,
D. R.,
and
BRUNHAM,
R.
D.:
‘TM-mode coup-
ling coe icien s in guided-wa e dis ibu ed eedback lase s’,
IEEE
J.
Quan um Elec on.,
1976,
QE-12,
pp. 7478
SWITCH ED-CAPACITOR NEURAL
NETWORKS
FOR
LINEAR PROGRAMMING
Indexing e ms: Neu al ne wo ks, Swi ched-capaci o ne -
wo ks, Linea p og amming sol e s, Ci cui heo y and design
A ci cui o online sol ing
o
linea p og amming p oblems
is p esen ed. The ci cui uses swi ched-capaci o echniques
and is hus sui able o monoli hic implemen a ion. The con-
nec ion o he p oposed ci cui o analogue neu al ne wo ks
is also ou lined.
In oduc ion:
I has been shown ha bo h linea and nonlin-
ea p og amming p oblems can be sol ed by using analogue
ci cui s wi h a neu al-like s uc u e.’,’ These ci cui s exhibi
s ong po en ial o hose applica ions whe e online op i-
misa ion is equi ed as is he case in obo ics, sa elli e guid-
ance, e c. B eadboa d p o o ypes ha e been buil using
o - he-shel ci cui componen s.
‘G~
Since he equi ed
componen -coun is e y high e en o simple examples, i
makes sense o explo e he possible ealisa ion o hese ci cui s
using ully in eg a ed echniques.
Nonlinea p og amming sol e s a e pa icula examples o
he b oade amily o analogue neu al ne wo ks, which is o
inc easing in e es because i seems o pa e he way
o
ana-
logue a i icial in elligence
ci cui ^.'.^
Howe e , he ield o
analogue neu al ne wo ks is jus eme ging and e y li le has
been done on he p ac ical implemen a ion o he di e en
classes o such ne wo ks. In
a
e y ecen le e , Tsi idis and
Anas assiou’ p oposed
a
echnique o he
VLSI
implemen a-
ion o
a
ype o analogue neu al ne wo k using
a
swi ched-
capaci o neu al cell. The p oposed echnique is adequa e o
sol ing op imisa ion p oblems ha can be o mula ed in an
explici o m,’ bu no eadily applicable o linea and nonlin-
ea p og amming p oblems.
A
di e en s a egy is equi ed o
his ype o analogue neu al ne wo k, since he equa ions
desc ibing ma hema ical p og amming p oblems a e implici
in
na u e and do no admi o being cas in an explici o m.’
In his le e we p opose a me hod o he ealisa ion o
linea p og amming sol e s using swi ched-capaci o ech-
niques. The p oposed ci cui s a e membe s o he gene al
amily o analogue neu al ne wo ks, being mo e adequa e o
monoli hic implemen a ion han p e ious linea p og amming
sol e p oposals.
P oblem o mula ion
and
p oposed ci cui s uc u e:
The
gene al linea p og amming p oblem can be s a ed as
ollows.6 Minimise a scala cos unc ion
@(x)
=
1
aixi
i=
1
subjec o
a
se o
p
cons ain s,
n
LXx)
=
1
bji
xi
2
0
i=
1
l<j<p
(2)
whe e
x
is he ec o o a iables o he p oblem,
p
and
n
a e
in ege numbe s and
a
and
bj,
o each
j,
a e ec o s o coe i-
cien s.
ELECTRONICS LETTERS
14 h
Ap il
1988
Vol.
24
NO.
8
Au ho ized licensed use limi ed o: Uni e sidad de Se illa. Downloaded on Ma ch 31,2020 a 14:34:02 UTC om IEEE Xplo e. Res ic ions apply.
By using he concep o he penal y unc ion' and applying
a g adien s a egy we ob ain he ollowing nume ical algo-
i hm o sol e he abo e gene al linea p og amming p oblem,
whe e
a
is an a bi a y posi i e cons an ,
q
is an in ege
numbe o he i e a ion coun and unc ions
w( )
and
pj
a e
de ined as ollows,
1
0
o he wise
i j
2
0
o
e e y
j
w(n
=
{
(4)
whe e
No e ha he in oduc ion o he unc ion
w( )
means
a
modi ica ion o he adi ional way o combining
and
@
o
de ine penal y unc ions.' This modi ica ion is impo an o
imp o e he con e gence o he algo i hm.
Using eqns.
4
and
5
and eqns.
1
and 2 in eqn.
3
we ob ain
he ollowing ela ionship o each componen o
x:
is an a bi a y posi i e cons an .
whe e sgn
(.)
is he well-known sign unc ion.
IV
I
ll
II
'qdd
phose
Fig.
1
Block diag am
o
p oposed linea p og amming sol e
Fig.
1
shows he concep ual block diag am o he imple-
men a ion o he gene al linea p og amming p oblem using
swi ched-capaci o echniques. No e ha one in eg a o is
equi ed pe p og am a iable. The
p
cons ain unc ions a e
ob ained ia a se o summe s whose inpu s a e he in eg a o
ou pu s. The nonlinea unc ions
w( )
gi en in eqn. 4, and
=
+(I
-
sgn
(L))
a e espec i ely ob ained om he
ou pu s o he summe s ia he block a he bo om o he
Figu e on he igh , hence o h called he cons ain block.
Fig. 2 shows a de ail o he i h in eg a o block. A wo-
phase clock signal is used o con ol he analogue swi ches.
The inpu swi ches a e di ec ly con olled by one o he phases
( he e en clock phase) and he swi ches connec ed o he
op-amp nega i e inpu lead a e con olled by he ou pu s o
he cons ain block. These ou pu s a e de ined du ing he odd
clock phase. By elemen a y analysis in ol ing cha ge conse -
a ion p inciples i is clea ha he ci cui in Fig. 2 imple-
men s eqn.
6.
The summe block appea ing in Fig.
1
can be
implemen ed by using echniques epo ed elsewhe e.'
Fig.
2
De ail
o
in eg a o block
P ac ical esul s:
The p oposed ci cui has been compu e
simula ed using DIANA' and a de ailed mac omodel
o
he
op-amps.' The simula ed p og amming p oblems a e lis ed in
Table
I,
whe e bo h he heo e ical solu ion and he one com-
pu ed by DIANA a e shown o e e y example. Also included
in Table
1
is he numbe o clock pe iods equi ed o he
ci cui o each i s inal s a e. In all he cases, he ini ial s a e
was he o igin o he p og am a iable space. As can be seen i
is possible o ob ain a e y app oxima e solu ion in ela i ely
ew clock pe iods.
Conclusions:
A ci cui s uc u e is p oposed
o
implemen ing
linea p og amming p oblems using swi ched-capaci o ech-
niques. This s uc u e is based on
a
educed se o basic cells
ha a e in e connec ed ollowing
a
dense egula pa e n. The
esul ing ci cui s exhibi
a
e y high modula i y and in his
sense can be conside ed as membe s o he gene al amily o
analogue neu al ne wo ks. The me hod is alid o any linea
p og amming p oblem and is also sui able o monoli hic
implemen a ion,
a
signi ican ad an age as compa ed o p e-
ious analogue neu al linea p og amming sol e s.'*2
Acknowledgmen s:
This esea ch has been suppo ed by
Spanish CICYT unde con ac no. ME87-0004.
A. RODRIGUEZ-VAZQUEZ
9 h
Feb ua y
1988
A. RUEDA
J.
L. HUERTAS
R. DOMINGUEZ-CASTRO
Depa amen o de Elec icidad y Elec bnica
Facul ad de Fisica
Uni e sidad de Seuilla
Anda. Reina Me cedes sjn, 41012-Se illa, Spain
Table
1
THEORETICAL AND SIMULATION RESULTS FOR
TWO
PROBLEMS
Scala unc ion Simula ed Numbe o
cons ain s solu ion DIANA pe iods
and Theo e ical solu ion using clock
@
=
,
+
2
2
=
5
+
u,
2
=
5
-
u2
@
=
3 ,
+
(1/2) ,
-
(1/2) 3
l
=
35/12
-
(5/12) 1
+
~2
1
=
-5
~1
=
-4.99
0.03
40
2
=
3512
-
(5/2)~1
-
VZ
u2
-5
02
=
-5.03
0.08
,
=
6
+
1
+
2
+
3
01
=
-6
VI
=
-5.88
0.3
2
=
6
-
V,
-
02
-
~3
2
=
0
2
=
-0.04
0.11 40
3
=
6
+
1
+
2
-
2 3
4
=
6
-
01
-
02
+
203
s
=
6
+
VI
-
2~2
+
03
6
=
6
-
01
+
2~2
-
03
j
=
0
3
=
-0.01
0.15
ELECTRONICS LETTERS
14 h Ap il
1988
Vol.
24
No.
8
497
Au ho ized licensed use limi ed o: Uni e sidad de Se illa. Downloaded on Ma ch 31,2020 a 14:34:02 UTC om IEEE Xplo e. Res ic ions apply.
Re e ences
1
TANK,
D.
w., and HOPFIELD,
J.
J.:
‘Simple “neu al” op imiza ion
ne wo ks: an A/D con e e , signal decision ci cui , and a linea
p og amming ci cui ’,
IEEE T ans.,
1986,
CAS33,
pp. 53>541
KENNEDY,
M.
P.,
and
CHUA,
L.
0.:
‘Uni ying he Tank and Hop ield
linea p og amming ci cui and he canonical nonlinea p og am-
ming ci cui o Chua and Lin’,
IEEE
T ans.,
1987,
CAS-34,
pp.
21G214
3 WILSON, G.
:
‘Quad a ic p og amming analogs’,
IEEE
T ans.,
1986,
4
TSIVIDIS,
Y.:
‘MOS analog IC design-new ideas, ends and obs a-
cles’. P oceedings o he 1986 Eu opean Con . on Solid-s a e Ci -
cui s, 1986, pp. 113-115
5
TSIVIDIS,
Y.,
and
ANASTASIOU,
D.: ‘Swi ched-capaci o neu al ne -
wo ks’,
Elec on. Le .,
1987,
23,
pp. 958-959
6
VANDERPLAATS,
G. .: ‘Nume ical op imiza ion echniques o
enginee ing design: wi h applica ions’ (McG aw-Hill, New Yo k,
1984)
7 GREGORIAN, R., and
TEMFS,
G. c.: ‘Analog
MOS
in eg a ed ci cui s
o
signal p ocessing’ (Wiley-In e science, 1986)
8
ARNOUT,
G.,
REYNAERT,
PH.,
CLAESEN,
L.,
and DIJMLUGOL, D.:
‘DIANA V7E use ’s guide’. ESAT Labo a o y, Ka holieke Uni-
e si ei Leu en, 1983
PBREZ-VERDI~,
B.,
HUERTAS,
J.
L.,
and
RODRIGUEZ-V~ZQUEZ,
A.: ‘A
new nonlinea ime-domain op-amp mac omodel using h eshold
unc ions and digi ally-con olled ne wo k elemen s’,
IEEE
J.
Solid-s a e Ci cui s,
22,
o
be
published
2
CAS-33,
pp. 907-91
1
9
second s uc u e (58N). We ha e measu ed o he hi d s uc-
u e (SON) shee concen a ions as high as
8
x
10”
cm-’ wi h
mobili ies o 3500cmZ/Vs.
The p ocessing o hese MESFETs was simila o ha
epo ed p e iously.6 The MESFETs had a ga e leng h o
0.7 pm wi h a 4.0pm sou ce/d ain spacing. The
1/V
cha ac e -
is ics o 58N-s uc u e MESFET ha ing a 100pm ga e wid h
a e shown in Fig. 1. A d ain sa u a ion cu en o 870mA/mm
and comple e pinch
o
a a ga e ol age o -3.5V is
achie ed.
Fo
he 48N s uc u e MESFET, a d ain cu en o
680mA/mm wi h a pinch
o
ol age o
-
3.0V was measu ed.
Fo de ices on he SON-s uc u e wi h a shee concen a ion
o
8.0
x
1012cm-z, we measu ed cu en s as high as l.OA/
mm bu hey could no be pinched-o . Fig. 2 shows he a ia-
ion o he ansconduc ance wi h ga e ol age o he
58N-s uc u e MESFET. The la ge bandgap AlInAs con ines
he ca ie s in he channel, esul ing in he b oad peak in he
ansconduc ance agains ga e ol age and imp o ed linea i y
o high-powe FETs. Ex insic ansconduc ances as high as
325 mS/mm we e achie ed. Fo he 48N-s uc u e MESFETs,
we achie ed ansconduc ances be ween 250 and 3
10
mS/mm.
A ga e/d ain b eakdown ol age o 3.2V was measu ed a a
leakage cu en o 0.5 pA/pm o ga e wid h o he 58N s uc-
u e. Highe b eakdown ol ages can be ob ained wi h hicke
undoped AlInAs laye s, bu a a sac i ice o ansconduc ance.
g=o
-
HI
G
H
-
C
U
R
R
E
NT
P
U
LS
E
-
DOPED
Ga
I
n
As
MESFET
Indexing e ms: Semiconduc o de ices and ma e ials, Field-
e ec ansis o s, Gallium compounds
We epo he DC and mic owa e pe o mance
o
pulse-
doped GaInAs powe MESFETs. Fo a 0.7pm ga e-leng h
de ice, a
maximum
d ain-cu en densi y o 870mA/mm and
a peak ansconduc ance o 325 mS/mm we e measu ed. A
maximum s able gain o ll.7dB a 26GHg and an ex apo-
la ed , o 33 GHz we e ob ained. These alues a e he highes
epo ed
o
MESFETs ha ing ga es as long as 0.7
pm.
Powe ampli ie s based on GaAs/AlGaAs HEMTs su e om
low d ain-sa u a ion cu en . Recen ly, mul ichannel and
pseudomo phic HEMTs ha e been de eloped o inc ease
cu en densi ies,‘-4 bu he low he mal conduc i i y o he
GaAs subs a e limi s he maximum achie able powe o hese
de ices. Imp o ed pe o mance can be ob ained by using
AlInAs/GaInAs he e os uc u e FETs, which combine high
mobili y wi h high shee -ca ie concen a ion. In addi ion,
he InP subs a e o e s highe he mal conduc i i y han
GaAs. The mic owa e pe o mance o AlInAs/GaInAs
HEMTs is beginning o su pass ha o GaAs/AIGaAs
HEMTs.*’ We ecen ly epo ed n -pulse-doped GaInAs
MESFETs o 0.7pm ga e leng h wi h excellen maximum
s able gains o 14dB a 26.5 GHz, and a maximum equency
o oscilla ion o g ea e han 100GHz.6 In his le e , we
epo he ab ica ion and pe o mance o n+-GaInAs-channel
MESFETs wi h bo h high cu en densi ies and high gains.
The pulse-doped GaInAs MESFET s uc u e was g own by
MBE on a semi-insula ing InP subs a e. The de ice s uc u e
consis ed o a 2500A AlInAs bu e laye ,
lOOA
o undoped
GaInAs, a 200A n+-GaInAs laye , 500A
o
undoped AIInAs,
and a
l00A
n+-GaInAs cap. All he laye s we e la ice
ma ched o InP. The undoped AlInAs laye educes he ga e
leakage cu en and inc eases he ba ie heigh . We ha e
g own h ee s uc u es wi h a ying elec on concen a ion.
Fo he i s s uc u e (48N), a Hall mobili y o 4100cm2/Vs
wi h an elec on concen a ion o 4.8
x
10’2cm~Z was mea-
su ed a 300K. A Hall mobili y o 4100cm2/Vs wi h an elec-
on concen a ion o 5.8
x
10’2cm-2 was measu ed o he
*
FATHIMULLA,
A,,
ABRAHAM,
J.,
and
LOUGHRAN,
T.: ‘High pe o mance
InGaAs/InAlAs HEMTs and MESFETs’. Submi ed o publica ion
(IEEE Elec on. De ice Le s.)
498
/
s
I-
2 5
g
=
-3
o
g
=-3
5
::e,;,
10
0
05
10
15
20 25
sou ce
d ain ol age,
V
Fig.
1
IIV
cha ac e is ics o a pulse-doped GalnAs MESFET
The mic owa e pe o mance o hese MESFETs o di e -
en sou ce/d ain ol ages and ga e ol ages was measu ed
o e he equency ange 0.5-26.5 GHz using an au oma ed
Cascade wa e p obe and an HP 8510 ne wo k analyse . Fig.
3 is a plo o he maximum s able gain (MSG) agains e-
quency compu ed om he measu ed S-pa ame e s. An MSG
o ll.7dB a 26.0GHz and an ex apola ed
mx
o o e
100GHz was ob ained. The cu en gain was also compu ed
om he measu ed S-pa ame e s. Ex apola ing a 6 dB/oc a e
oll-o ,
a cu en -gain cu o equency
C ,)
o 33GHz was
ob ained. The mic owa e-gain measu emen s we e pe o med
bo h be o e and a e isola ing he ga es om he edge o he
mesa.* A e ga e isola ion, we measu ed an inc ease in he
MSG, which we a ibu ed o a dec ease in he ga e-leakage
cu en .
350
lOOV
,
I I I
I
I
-3
5
-3
0
-2
5
-2
0
-1
5
-1
0
-0
5
0
ga e ol age,
V
111312/
Fig.
2
T ansconduc ance agains ga e ol age o pulse-doped GalnAs
MESFET
ELECTRONICS LETTERS 14 h
Ap il
1988
Vol.
24 No.
8
Au ho ized licensed use limi ed o: Uni e sidad de Se illa. Downloaded on Ma ch 31,2020 a 14:34:02 UTC om IEEE Xplo e. Res ic ions apply.