TELKOM
NIKA Indonesia
n
Journal of
Electrical En
gineering
Vol.12, No.6, Jun
e
201
4, pp. 4184 ~ 4
1
8
9
DOI: 10.115
9
1
/telkomni
ka.
v
12i6.474
2
4184
Re
cei
v
ed O
c
t
ober 1
2
, 201
3; Revi
se
d Decem
b
e
r
29, 2013; Accept
ed Ja
nua
ry 1
9
, 2014
X-Band 5-bit MMIC Digital Attenuator with Low Phase
Shift
Chen
gpeng Liu*
1
, Xin Xu
2
, Zhengrong
He
3
Sichu
an Institu
t
e of Solid Stat
e Circuits,
Ch
in
a Electron
ics T
e
chn
o
lo
g
y
Gro
up Cor
p
.,
Cho
ngq
in
g 40
0
060, P. R. Chin
a
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: lcp54
91
3@1
63.com
1
,shen
l
and
eh
ai@
126.
com
2
, hzr7352
5@sin
a
.com
3
A
b
st
r
a
ct
T
h
is p
a
p
e
r pr
esents th
e x-
ban
d
5-bit M
M
IC di
gital
att
enu
ator w
i
th
l
o
w
phas
e s
h
if
t. Phas
e
compensation
techniques were us
ed
in t
h
e MMIC design to reduce the
phase shift. This
attenuator
is
fabricate
d
w
i
th 0.2
µ
m GaAs P
H
EMT
process
.
Measur
e
m
ent
results of the
deve
l
op
ed MM
IC chips i
n
the
x
-
ban
d show
that the 5-bit MMIC digita
l atten
uator has
0.5
d
B
reso
lutio
n
a
nd 15.5
d
B dyn
a
mic attenu
ati
o
n
rang
e, inp
u
t return l
o
sses
w
a
s less than
10dB
and
ou
tput return l
o
s
s
es w
a
s less
than 1
3dB for
al
l
attenuation st
ates, RMS is les
s
than
0.2dB; insertion loss is
less than
3.
8dB; phas
e shift error is
less than
5°for 35 atten
u
a
tion states; T
he MMIC ch
ip si
z
e
is
1.58 mm×
2
.95 mm×
0
.
1
mm.
Ke
y
w
ords
: X-ban
d, 5-bit, dig
i
tal attenu
ator, low
phase s
h
ift
Copy
right
©
2014 In
stitu
t
e o
f
Ad
van
ced
En
g
i
n
eerin
g and
Scien
ce. All
rig
h
t
s reser
ve
d
.
1. Introduc
tion
MMIC va
riab
le attenu
ators a
r
e
re
qui
red in
ma
ny
comm
uni
cat
i
on sy
st
em
s su
ch as
cellul
a
r-pho
n
e
s to co
ntrol
the sign
al level and
adj
ust
the system
power bu
dge
t. An attenuator
spe
c
ially is a
key device
of the modul
e use
d
in
cel
l
ular-ph
one
s
becau
se the
attenuator i
s
to
control of the amplitude [1
-4].
The atten
uat
or h
a
s two
types of
control
metho
d
, analo
g
at
tenuator an
d
digital
attenuator.
Di
gital attenu
ators offer bett
e
r lin
ea
rity, high p
o
wer
han
dling, a
nd e
a
s
y an
d a
c
curate
control of att
enuatio
n, So
MMIC di
gital
attenuators
h
a
ve gain
ed lo
ts of interest
in re
ce
nt yea
r
s
[5].
The re
quirem
ents of the MMIC digital attenuat
ors to be de
signe
d are a
s
followi
ng: smal
l
size, high attenuation accuracy, low insertion ph
ase shift, high reli
ability and low cost [6].
In this pap
er,
we de
scri
be
s an M
M
IC d
i
gital attenuat
or with l
o
w
p
hase shift in X-ban
d.
The 5
-
bit digit
a
l attenuato
r
has
obtaine
d
excelle
nt
perf
o
rma
n
ces a
n
d
impleme
n
ts in 0.2um Ga
As
PHEMT MMIC.
2. Circuit
Desi
gn
Publish
ed lit
eratu
r
e o
n
M
M
IC digital
a
ttenuat
ors m
a
inly rely o
n
three
ba
sic
types of
topologi
es: i)
Tee attenuat
or; ii) Bridge
d
-
Tee atten
uat
or; iii) Pi attenuator. All of them relay o
n
a
sign
al throug
h eithe
r
a by
pass li
ne
or
an atten
uatio
n cell
with
RF switche
s
[
7
, 8]. Figu
re
1,
Figure 2 an
d
Figure
3 sh
ow the top
o
l
ogie
s
of
Tee
attenuator, Bridge
d-T
ee attenuator an
d
Pi
attenuator.
Referrin
g to
FIG.5. the
schematic of th
e x-
ba
nd
MM
IC digital
atte
nuator with
lo
w p
h
a
s
e
shift is
sh
own. To a
c
hiev
e goo
d pe
rfo
r
man
c
e, th
e
circuit
config
uration
a
s
well as the p
r
o
c
e
s
s
con
d
ition
s
, sh
ould be
sele
cted prop
erly.
The di
gital
attenuator consi
s
ts
of swit
ch
ed P
H
EMTs, capa
citors, resi
st
ors,
and
microstri
p
lin
es. When
PHEMT i
s
ON-s
tate,a s
m
all
res
i
s
t
ance R
ON
,
ideally zeroed, appe
ars
betwe
en sou
r
ce
and
drai
n
ports;
whe
n
PHEMT is
O
FF-state, th
e simplifie
d e
quivalent mo
del
sho
w
s a hig
h
resi
st
an
ce
R
OFF
and a Parallel ca
pa
citor C
OFF
betwee
n
sou
r
ce an
d
drain
port
s
;T
he
s
w
itc
h
ed
PHEMT
s
in
th
e
c
i
rc
u
i
t ar
e con
t
r
o
lle
d th
ro
ug
h
8k
Ω
re
sist
ors of the
ga
te pole
s
,
whi
c
h
provide
en
ou
gh radio f
r
eq
uen
cy isol
ation bet
wee
n
t
he gate
of e
a
ch
switch
ed
PHEMT a
n
d
the
control so
urces. And the lo
w value re
si
stors a
r
e
u
s
e
d
to form the topologi
es for a
ttenuators [9].
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
X-Band 5
-
bit MMIC Digital
Attenuator wit
h
Low Pha
s
e
Shift (Chen
gp
eng Liu
)
4185
Figure 1. Tee
Attenuator
Figur
e 2. Brid
ged-Tee Attenuator
Figure 3. Pi Attenuator
Figure 4. Simple Tee Atten
uator
Figure 5. Sch
e
matic of the
Digital Attenu
ator
The five requ
ired
attenuati
on bits are t
he 0.5dB, 1
d
B
, 2dB, 4dB
and 8
d
B, pro
v
iding a
dynamic rang
e from
0.5dB
to 15.5dB
. T
e
e attenu
ator
(Figure 1
)
i
s
selecte
d
for 0.
5dB-bit, 1
d
B-bit
and
2dB-bit a
ttenuator,
Te
e attenu
ator i
s
cho
s
e
n
b
e
cause of
its
g
ood
pe
rform
a
nce
in
inserti
o
n
loss, input/ou
t
put VSWR
and ha
s bett
e
r attenu
ate pre
c
isi
on tha
n
other. The
Tee attenua
tor
use
d
in
0.5d
B-bit an
d 1d
B-bit is Simp
le Tee
atten
uator (Fig
ure
4), com
pare
to
typical T
e
e
attenuator, th
e Simple Tee
attenuator wi
thout R1
and
parall
e
l PHE
M
T swit
ch, the attenuator
cell
is re
pre
s
e
n
te
d only by R2
to the grou
n
d
. The Tee
a
ttenuator u
s
e
d
in 2dB-bit negle
c
t the
R1,
microstri
p
lin
es len
g
ths a
r
e use
d
to ha
ve no pha
se
shift betwe
en
the two states. The 4dB
-bit
and
8dB-bit is acqui
red
by
usin
g Pi
atten
uator (Fi
gure
3), b
e
cau
s
e
o
f
two
switch
e
s
, Pi atten
uat
or
has mo
re
in
sertion
lo
ss,
b
u
t Pi attenu
a
t
or i
s
ro
b
u
st
to the tem
p
e
r
ature va
riati
on a
n
d
proce
ss.
becau
se th
e
differen
c
e
bet
wee
n
p
a
ra
siti
c
com
pone
nts
ca
su
sed
by
the O
N
-state
and
OF
F-sta
t
e
operation
s
of
the switching
PHEMTs of t
he di
gi
tal Atte
nuator
cau
s
e
s
the
differen
c
e
between
the
pass p
hases.
0.5dB-bit, 1
d
B-bit and
2
d
B-bit att
enu
ator have littl
e impa
ct on
the pha
se
sh
ift
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 12, No. 6, June 20
14: 4184 – 4
189
4186
error, throug
h
the optimization of
t
he ci
r
c
uit
,
sat
i
sf
a
c
t
o
ry
re
sult
s
a
r
e
obtaine
d. a p
hase corre
c
tion
unit conn
ecte
d in
parallel
with the
4dB
-bit and
8dB
-b
it attenuation
circuit u
n
it. Besid
e
the
R2
the
pha
se corre
c
tion unit stru
cture is the
sa
me with
Pi attenuator. In p
e
rfect
ca
se, microstri
p
lin
es
length
s
between O
N
an
d
OFF state
s
i
s
zero, In
realit
y, Lengths a
r
e also
used t
o
have no p
h
ase
shift betwe
en
the two state
s
, and u
s
e th
e same
confi
guratio
n in two cha
nnel [10
,
11].
The digital attenuato
r
uses
8 voltage co
n
t
rol
port to feed the PHEM
Ts’ gate pol
e
s
. In this
ca
se, when t
he control v
o
ltage
s are
set at -5
V,
whi
c
h is th
e
negative pi
nch
-
off voltage of
swit
che
d
PHEMT, the swi
t
ched PHEM
T will wo
rk at
its “off” state
(high resi
sta
n
ce
). Wh
en the
control voltag
es a
r
e set at 0V, The switched PHEM
T
will wo
rk at its “o
n”
state. So the req
u
ired
attenuation
can be obtai
ne
d by switchin
g the cont
rol voltages at th
e port.
The digital attenuato
r
is at the minimum
att
enuation st
ate, when the
control volta
ges P3,
P6 an
d P8
are 0
V, P1, P2
, P4, P5 a
n
d
P7 are
-5
V. In this
ca
se, t
he atten
uato
r
ha
s
a mi
nim
u
m
inse
rtion l
o
ss. The atten
u
a
tor i
s
at th
e
maximu
m
attenuation
stat
e, wh
en the
control voltag
es
P1, P2, P4,
P5 and P7 are 0 V, and P3,
P6 and P8 are -5V.
The ab
ove d
e
scriptio
n is
equally avail
able fo
r
the other states. The
control signal
with
the value of 0
V is taken a
s
“1”
and th
e control
sign
al
with the valu
e of -5 V i
s
ta
ken
as
“0.”
T
he
truth table
of the digitally-controlle
d mai
n
attenuati
o
n
states
sh
ows in T
able
1, whi
c
h i
s
ref
e
rred
to in Figure 4.
Table 1. Truth Table of Ma
in Attenuatio
n
States Shows (“1”a
s
0V.0
”AS -5V)
0.5dB
1dB
2dB
4dB
8dB
P1
P4
P2 P3
P5 P6 P7
P8
MIN
0
0
0 1
0 1 0
1
0.5dB
1
0
0 1
0 1 0
1
1
dB
0
1
0 1
0 1 0
1
2
dB
0
0
1 0
0 1 0
1
4
dB
0
0
0 1
1 0 0
1
8
dB
0
0
0 1
0 1 1
0
MAX
1
1
1 0
1 0 1
0
Usi
ng the
ne
w configu
r
ati
on, a di
gital
a
ttenuator ha
s be
en
reali
z
ed by 0.2
u
m
GaAs
pro
c
e
ss.
Th
e sim
u
lation
of ou
r digi
tal
attenuato
r
have
bee
n presented
ba
sed
on
the
ADS200
8.Bro
adba
nd a
nd
low p
h
a
s
e
shift performa
n
ce
wa
s
ach
i
eved by o
p
timization
of the
transmissio
n line paramete
r
s an
d the re
sistor value
s
.
The M
onte
Carl
o analysi
s
were al
so utilized
in the attenuator
design, the result
s
predi
cted tha
t
the design
has
stability again
s
t t
he pro
c
e
ss va
ri
ations. The l
a
yout of x-band
MMIC di
gital
attenuator
with lo
w p
h
a
s
e
shift a
s
sho
w
n in
Figu
re
6. RF
inp
u
t an
d outp
u
t a
r
e
at
the eithe
r
en
d with
com
p
l
e
menta
r
y pai
rs
of the
cont
rol
lin
es alon
g
one
edg
e. The chip si
ze
wa
s
1.58mm
×
2.9
5
mm.
Figure 6. The
Layout of x-band MMIC
Di
gi
tal Attenuator with Lo
w P
hase Shift
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
X-Band 5
-
bit MMIC Digital
Attenuator wit
h
Low Pha
s
e
Shift (Chen
gp
eng Liu
)
4187
3. Measur
e
d
Results
The ci
rcuit m
easure
m
ent
wa
s complet
ed by
u
s
ing
a com
pute
r
controlle
d test
system,
Whic
h
c
o
ns
ists
of computer platform, GPIB inte
rface,
Agilent PNA
-
X netwo
rk an
alyzer an
d da
ta
acq
u
isitio
n card.
In
put and output
indu
ctan
ce
of 0.5
n
H
inclu
ded.
Ci
rcuit
pa
ram
e
ters
measurement
wa
s cond
ucted for
all 35
attenuation states.
T
he
eight
control voltages of
the
attenuator
we
re usi
ng Truth table.
Figure 7. Inse
rtion Lo
ss
Figure 8. Rel
a
tive Attenuation
Figure 9. Input Return L
o
ss
Figure 10. Ou
tput Return L
o
ss
Figure 11. RMS Amplitude Erro
r
Figure 12. Re
lative Phase
Shift
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 12, No. 6, June 20
14: 4184 – 4
189
4188
Figure 13. Dif
f
eren
ce bet
ween Max and
Min Phase Shift
The me
asure
d
insertion l
o
ss i
s
sho
w
n i
n
Fi
gu
re 7. T
he attenuat
or achi
eved a
minimum
inse
rtion lo
ss of 2.9~3.8dB
in
the entire
x-band. Referring to Figu
re
8, It can be see
n
that each
curve i
n
the figure
rep
r
e
s
e
n
ts a differe
n
t
att
enuation
setting in a roughly 0.5dB
step with ov
er
15.5dB dyna
mic rang
e, for which a p
r
ope
r
combi
n
ation of the
control voltag
es
wa
s cho
s
en.
Figure 9 and
Figure 1
0
show the m
e
a
s
ured inp
u
t and output return lo
sses fo
r 35 attenu
ation
states.
The
in
put return
lo
ss
wa
s al
way
s
less th
an
10
dB and
the
o
u
tput return
l
o
ss
wa
s al
wa
ys
less than 13d
B at any atte
nuation
settin
g
from x-
ban
d. RMS ampli
t
ude error i
s
sho
w
n in Fig
u
re
11, whi
c
h wa
s belo
w
0.2d
B. Figure 12, and Figu
re
1
3
sho
w
the Relative Phase
Shift, Differe
nce
between Max
and Min Phase Shift. ph
ase
shift error is very low,
Difference between max and
min pha
se sh
ift for all valu
es of attenuat
ion, the
value
is less than 5
°
for 35 atten
uation state
s
.
4. Conclu
sion
The the
o
ry, d
e
sig
n
, an
d m
easure
m
ent
o
f
a the x
-
ba
n
d
5-bit MMI
C
digital atten
u
a
tor
with
low p
h
a
s
e
sh
ift are p
r
e
s
en
ted. Phase compen
satio
n
techni
que
s
were
used in t
he MMIC de
sign
to reduce the phase shift. To ensure hi
gh yield,
Perf
ormance redundancy
opti
m
ization strat
egy
is u
s
e
d
in
de
sign. th
e
re
sults of
the
de
veloped
MMI
C
chip
s i
n
th
e x-b
and
sho
w
that
the
5-bit
MMIC digital
attenuato
r
h
a
s 0.5
d
B resolution a
nd
15.5dB dyn
a
m
ic atten
uati
on rang
e, in
put
return lo
sses wa
s le
ss t
han 1
0dB
a
nd outp
u
t re
turn lo
sse
s
wa
s le
ss th
an 13
dB for all
attenuation
st
ates,
RMS is
less than
0.2
d
B; inse
rt
ion l
o
ss is le
ss th
an 3.8dB; p
h
a
se
shift e
r
ro
r is
less than 5°f
o
r 35 attenua
tion states. T
he MMIC
chi
p
size i
s
1.5
8
mm×2.95
mm×0.1
mm. This
prop
osed MM
IC has
sho
w
n
excellent pe
rforma
n
c
e
cov
e
ring x-ban
d for digital atte
nuator.
Referen
ces
[1]
Goldfarb ME,
Platzker A. A w
i
de r
a
n
ge a
n
a
lo
g MMI
C
attenu
ator
w
i
th in
tegral 180° ph
ase
sh
ifter.
IEEE
T
r
ans. on Microw
ave T
heory
and T
e
ch
ni
que
s.
2007; 42(
1): 156-
158.
[2]
Juron
g
Hu, Xu
nin
g
Z
hu, Lon
g Che
n
. Electromag
netic Env
i
ronme
n
t and
T
a
rget Simulator for Rad
a
r
Te
s
t
.
T
E
LKOMNIKA Indon
esi
an Jour
nal
of Electrical E
ngi
ne
erin
g
. 201
3; 11
(7): 3699-
37
03
.
[3]
R Sh
ans
han
L
i
, Jia
n
Z
h
ou.T
r
ansmitter Stati
on
Remot
e
M
onitor
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