N
Abs ac —
In-ci cui es ing me hodologies a e equi ed o
ackle he e alua ion o embedded adio- equency ci cui s.
This pape p esen s design conside a ions o he es ci cui y
p oposed o implemen a me hodology o on-chip es ing a
low-noise ampli ie . The scheme being p oposed includes an
oscilla o as he s imulus gene a o , he e-design o he LNA
inpu swi ch o es con ollabili y, and an RMS-DC con e e
o measu e he LNA’s ou pu powe . Simula ion esul s o
1dB comp ession and hi d-o de in e cep poin s show a good
ag eemen wi h he expec ed ones.
Index Te ms — RF, es abili y and es echniques, low noise
ampli ie .
I.
I
NTRODUCTION
ew on-chip es me hodologies a e equi ed o ackle
he di icul ies ound when es ing he new
gene a ion o in eg a ed sys ems comp ising adio-
equency (RF) ci cui s. This is pa icula ly ue a
p oduc ion s ages whe e he es equi emen s a e no as
exhaus i e as hose equi ed a he de eloping phase. Lowe
es equipmen cos is enabled by pa i ioning es esou ces
be ween on-chip and ex e nal equipmen . Howe e , new
highly s uc u ed design o es abili y (D T) app oaches a e
necessa y o imp o e accessibili y o deeply embedded
co es including he RF ones [1].
Di e en me hodologies ha e been p oposed add essing
he es ing o RF on -ends [2 – 7]. These can be di ided in
wo g oups o app oaches:
- in oduc ion o es esou ces wi hin each one o he
anscei e blocks
- ea ing he en i e RF on -end as a single block seen
om he base-band inpu and ou pu elemen s, a e
c ea ing a loop-back signal pa h by connec ing he PA
ou pu in o he LNA inpu .
The echniques in he i s g oup allow diagnosing which
blocks in a RF on -end a e de ec i e, and o p opaga e es
signals wi hou being a ec ed by he o he blocks inse ed
in he signal pa h, bu imply a highe o e head in es
ci cui y.
The wo k p esen ed he ein has been pa ly suppo ed by he Po uguese
go e nmen , Fundação pa a a Ciência e a Tecnologia, and ca ied-ou
unde he amewo k o p ojec s NanoTEST (2A702 - MEDEA+, phase 2)
and Ne wo k o Excellence IST-1-507893-NOE TARGET (Top Ampli ie
Resea ch G oups in a Eu opean Team).
J. Machado da Sil a, Gab iel Pinho, and J. S. Ma os a e wi h
Uni e sidade do Po o, Faculdade de Engenha ia, and INESC Po o,
Campus FEUP, Rª D . Robe o F ias nº 378, 4200-465, Po o, Po ugal
(phone:+351225081400; ax:+351225081443; e-mail: {jms, gab iel,
jsm}@ e.up.p ).
On he o he hand, he ones in he second g oup minimize
he ci cui y o e head bu don’ allow iden i ying which
block(s) a e beha ing inco ec ly. Fu he mo e, some
a chi ec u es and seconda y e ec s, such as an inc ease in
powe consump ion, may impai he use o loop-back
echniques [7].
In [8] echniques o measu e di e en pe o mance
cha ac e iza ion pa ame e s o he low-noise ampli ie
(LNA) we e p esen ed, which ely bo h on he inclusion o
es auxilia y esou ces and on eusing he unc ionali y o
al eady exis ing blocks.
One o hose echniques consis s on applying o he LNA
a sequence o s imuli wi h di e en ampli udes and
measu ing he ou pu ampli ude o each inpu le el. The
ob ained se o coo dina es (V
in
, V
ou
) allows inding he 3
d
o de polynomial ha bes i s he LNA’s ans e unc ion,
i.e., coe icien s a
0
, a
1
, a
2
and a
3
in (1).
...
3
3
2
210
++++=
inininou
aaaa
νννν
(1)
The LNA inpu ol ages which lead o he 1dB
comp ession (P
1dB
) and hi d-o de in e cep (IP
3
) poin s a e
hen calcula ed a e he polynomial coe icien s using,
espec i ely,
3
1
20
1
1
1
3
4
10 a
a
a
A
dB










−=
(2)
and
3
1
3
4
a
a
A
IP
=
(3)
LNA
Mixe
PA
Mixe
T/R
O
LO
Powe
RMS-DC
IF
A
RSSI
S
T
Fig. 1. T anscei e a chi ec u e wi h LNA’s es in as uc u e.
Design o Embedded Tes ing o a LNA
José Machado da Sil a, Gab iel Pinho, José S. Ma os
Acei e pa a ap esen ação na XX Con e ence on Design o Ci cui s and In eg a ed Sys ems, Lisboa, No emb o 2005
To embed his es scheme in he ci cui a ypology such
he one p esen ed in Fig.1 can be used, whe e an ampli ude
con olled oscilla o is equi ed o gene a e he di e en
ampli ude s imuli.
The local oscilla o (LO) used in he up-con e e
(mixe ) and he powe ampli ie (PA) i sel , can be used o
p o ide his unc ionali y, p o ided a loop-back scheme
exis s o connec he PA ou pu o he LNA inpu , and a
scheme o con ol he signal ampli ude is a ailable. In his
case he PA’s beha iou has o be aken in o accoun in he
cha ac e iza ion o he es s imulus, and e en ually he non-
linea i ies o some PA con igu a ions may impai he
iabili y o his solu ion due o he highe di icul y in
ob aining low ampli ude s imuli. This would imply also
highe powe consump ion du ing es ing.
To measu e he LNA’s ou pu powe , loga i hmic
ampli ie s could be used o allow o a wide dynamic
a ia ion o he signal powe o be ep esen ed wi hin a
limi ed ol age ange. The ecei ed signal s eng h indica o
(RSSI) block exis ing in ypical ecei e s’ a chi ec u es
associa ed o he in e media e equency (IF) ampli ie can
also be ( e)used o his pu pose. Bu in his case ei he he
mixe beha iou is also included in he measu e pa h, o a
swi ching mechanism has o be included o bypass i .
Howe e , as he in e media e equency is usually much
smalle han he LNA’s cen e equency, his app oach can
be comp omised.
One o he ad an ages b ough in by he second g oup o
es app oaches desc ibed be o e elies on he es ing
in e ace being made mainly a he baseband equency, and
hus a oids in e e ing and dealing di ec ly wi h high
equency signals. In o de o include a RF es
me hodology wi hin he global es s a egy o he in eg a ed
sys em, using he same es in as uc u e, i is desi able ha
obse a ion and con ol be made a low equencies.
The wo k p esen ed he ein add esses he implemen a ion
o he me hod p esen ed in [8], acco ding he scheme shown
in Fig.1, i. e., he design o a a iable ampli ude oscilla o
(VAO), o he swi ch o connec i o he LNA inpu , as well
as o he RMS-DC con e e o measu e he LNA’s ou pu
powe .
Sec ion II o he pape in oduces he LNA o be es ed.
Sec ions III o V desc ibe he oscilla o , he swi ch, and he
RMS-DC con e e o be included in he ci cui o es ing
pu poses. P elimina y simula ion esul s a e p esen ed in
sec ion VI. Finally concluding ema ks a e highligh ed in
sec ion VII.
II.
T
HE
LNA
Fig. 2 shows he scheme o he LNA o be es ed. I is a
cascode LNA wi h induc i e sou ce degene a ion [9]
designed wi h a 0.18 µm MOS echnology, uned a
435MHz, a equency used in he s anda d Eu opean
spec um o gene al eleme y and elecommand
applica ions.
M
1
M
2
M
3
L
1
L
2
R
2
C
2
C
1
C
3
L
3
R
3
i
o
V
DD
I
p
Fig. 2 – MOS LNA used in he simula ions.
I s nominal cha ac e is ics a e: inpu e lec ion coe icien
S
11
≈ -35 dB, powe gain S
21
≈ 15dB (Fig. 3), inpu 1dB
comp ession poin P
i1dB
= -10 dBm, and hi d-o de
in e cep ion poin IP
3
= 0.18 dBm.
Fig. 3 – S11 and S21 pa ame e s o he LNA.
One o he c i ical aspec s in RF on-chip implemen a ions
conce ns he implemen a ion o spi al induc o s on silicon,
bo h in e ms o he maximum ealisable induc ance alue
and quali y ac o (Q). Values o L om 1nH o 20nH wi h
Q=5 a e common wi h con en ional echnologies [9]. Q
alues up o abou 16 ha e been epo ed using newe
echnologies which p o ide a highe numbe o me al le els,
o equencies abo e 2GHz [10].
In he p esen wo k he model shown in Fig. 4 is used o
he induc o s conside ing Q alues a ound 5. L
S
and R
S
a e,
espec i ely, he spi al induc ance and he se ies esis ance,
C
S
models he eed- h ough pass c ea ed be ween he wo
e minals due o di ec capaci i e coupling, C
OX
is he oxide
capaci ance be ween he spi al and he silicon subs a e, and
R
Si
ep esen s subs a e losses. Al hough pa e ned g ound
shielding [10] can be used o minimize hese losses, i was
decided o include hem anyway.
L
S
C
S
p
i
R
S
C
OX
C
OX
R
Si
R
Si
p
o
Fig. 4 – Induc o model used in he simula ions.
III.
A
N
A
MPLITUDE
C
ONTROLLED
O
SCILLATOR
To implemen he es s imulus gene a o a scheme based on
he Colpi s oscilla o is p oposed, as i is one o he uned
schemes used in RF ci cui s due o i s simplici y. Fig. 5
shows he scheme o he oscilla o a e being imp o ed
wi h acili ies o con ol he ampli ude o he ou pu signal,
on/o swi ching (M
3
, M
4
), and ou pu bu e ing (M
5
).
The ou pu ol age o he Colpi s oscilla o is, in a i s
app oach, p opo ional o he p oduc o bias cu en (I
B
)
and he ne ank equi alen esis ance R
eq
(Fig. 5.b). This
esis ance is ac ually de e mined by he induc o ’s se ies
pa asi ic esis ance and he o e all equi alen esis ance
seen a he LC ank e minals.
R
eq
L
C
o
2I
B
sin
ω
a)
b)
M
1
M
2
M
3
L
1
R
V
C
2
o
V
DD
V
B
C
1
M
4
M
5
V
C
V
C
I
B
Fig. 5 – Scheme o he Colpi s based a iable ampli ude
oscilla o .
Va ying I
B
would p o ide a mo e linea ampli ude
a ia ion hen ha ob ained a ying R
eq
, howe e , i was
ound p e e able o keep I
B
cons an and o in oduce a
means o con ol R
eq
as a wide a ia ion could be a ained,
namely down o lowe ol age le els. This ea u e is
p o ided by elemen R
V
in Fig. 5.a), which basically is a
ansis o ope a ing in linea mode con olled by i s ga e
ol age. Being he numbe and ampli udes o he se o
s imuli le els o be applied de e mined, elemen RV can
ac ually be implemen ed by a s ack o ansis o s digi ally
con olled. This way a, mo e con enien , digi al in e ace is
allowed.
T ansis o s M
3
and M
4
ope a e in swi ching mode and a e
used o swi ch-o he oscilla o when he ci cui ope a es in
no mal mission mode. This acili y p o ides bo h o a oid
powe consump ion and o c ea e a high impedance ou pu
in no mal mode ( he unc ionali y o swi ch S
T
in Fig. 1).
T ansis o M
5
p o ides ou pu bu e ing.
The dynamic ange equi ed o he oscilla o ’s ampli ude
is de e mined by he LNA’s gain comp ession
cha ac e is ic. The di e en oscilla o ’s ou pu ol age
ampli udes should be dis ibu ed wi h uni o m inc emen s
below and abo e he alue leading o he 1dB comp ession
poin , so ha he polynomial (1) ha bes i s he LNA’s
ans e unc ion can be ound accu a ely. Fo he LNA
unde conside a ion he P
i1dB
co esponding inpu ol age
alue is abou 200 mV (-10dBm @ 50 Ω) peak- o-peak.
Fig. 6 – Oscilla o ’s lowes and highes ou pu le els.
Fig. 6 shows he oscilla o ou pu ol age a he lowes
and highes le els which co espond o abou -21dBm and
-2dBm, espec i ely, obse ed a he LNA inpu .
The a iable ampli ude acili y could ha e been ob ained
main aining he oscilla o ope a ing wi h cons an
ampli ude, ollowed by a a iable gain ampli ie . This
would lead o a la ge and, e en ually, mo e powe hung y
and noisie ci cui .
IV.
LNA
I
NPUT
S
WITCHING
The ansmi / ecei e swi ches used in anscei e s ci cui s
a e ypically implemen ed using disc e e componen s such
as GaAs MESFETs and PIN diodes. Designs using CMOS
pass ansis o s and ansmission ga es ha e also been
p oposed [11], bu ha e he disad an age o p esen ing
highe inse ion loss and nonlinea i y. These handicaps can
be o e come i ansis o s a e no inse ed in he signal pa h,
and a e ins ead used in associa ion wi h passi e de ices. A
swi ch based in his p inciple is p oposed in [12].
Howe e , o equencies below 1GHz, as Q is lowe , he
induc ance se ies esis ance is esponsible o a highe
inse ion loss which deg ades he S
21
pa ame e . To
minimize his e ec a swi ch based on a se ies esona o is
used [13].
L
1
C
1
C
2
O
IM
M
1
M
2
PA
LNA
L
2
VAO
Fig. 7 – An enna swi ch.
Fig. 7 shows he scheme o his swi ch, oge he wi h he
in e ace wi h he VAO and he PA’s ou pu swi ch (IM
block p o ides o impedance ma ching wi h he an enna).
In ecei ing mode bo h M
1
and M
2
a e o , leading L
1
and
C
2
o c ea e a se ies esona o which gi es pa h o he
an enna’s signal and whose inpu and ou pu impedances
ma ches he 50 Ω equi emen . In his case he oscilla o ’s
ansis o M
4
is on, leading M
5
o be o and p esen ing a
high impedance ou pu .
In es mode bo h M
1
and M
2
a e on, leading L
1
and C
1
o
o m a pa allel ank esona ing a he ansmi ing equency
ha c ea es an open ci cui (ac ually 230 Ω). (The same
happens when he PA ope a es in ansmi ing mode.) When
he swi ch is open he oscilla o can be swi ched on o apply
he es s imulus o he LNA inpu . As he swi ch’s ou pu
impedance is essen ially capaci i e, induc o L
2
is included
o adap his impedance o he oscilla o .
Fig. 8 shows S
11
and S
21
pa ame e s o LNA including
he swi ch in he ecei ing mode. The swi ch exhibi s an
inse ion loss o 0.94 dB in on mode and 10.5 dB isola ion
in o mode.
Fig. 8 – S11 and S21 LNA’s pa ame e s, including he swi ch.
Fig. 9 illus a es he wa e o ms obse ed a he an enna
and LNA inpu s, showing ha low dis o ion and low
in e e ence a e in oduced by he inpu swi ch, and he
VAO.
Fig. 9 – Wa e o ms a he an enna and LNA inpu s.
V.
RMS-DC
C
ONVERTER
Fig. 10 shows he scheme o he RMS-DC con e e being
p oposed o de ec he LNA’s ou pu ms ol age. Basically
i is a hal -wa e ec i ie using a diode-connec ed P-channel
MOS ansis o s in a common N-well. The bias ol age V
B
is se o allow measu emen s o be pe o med e en o he
lowes ol age le els. As he es is pe o med using a
known wa e o m i is easy o ela e he measu ed DC
ol age wi h he ac ual ms ol age alue.
RMS
-
DC
ou pu
C
1
V
DD
V
B
LNA
ou pu
M
C
2
R
Fig. 10 – Schema ic o he RMS-DC con e e .
The measu ed ms alue would no be co ec i he LNA
ope a ion eaches deep dis o ion, bu , o pe o m he
p oposed es i is no necessa y o use o high ol age
le els. Fo he highes ol age le els being used, he LNA
ou pu wa e o m s a s o comp ess i s o he nega i e
hal -cycles. Due o his ac , o ob ain a mo e accu a e
measu e, he nega i e hal -cycles a e cap u ed connec ing
he ec i ie ’s e e ence o V
DD
. A ull-wa e ec i ie would
equi e a mo e complica ed ci cui .
VI.
T
EST
S
IMULATION
R
ESULTS
Using he es ci cui y p esen ed be o e, a sequence o 11
equally spaced ol age le els spanning he en i e oscilla o
dynamic ange a e gene a ed con olling p ope ly he
oscilla o . Fig. 11 shows he LNA’s powe ans e
unc ions ob ained obse ing bo h he LNA’s (*) and he
RMS-DC (•) ou pu ol ages, oge he wi h he i s o de
ideal cha ac e is ic (–). I can be seen ha he alues
ob ained wi h he RMS-DC con e e lead o lowe ou pu
powe s o he highe inpu ol ages. This is due, as said
be o e, o he ac ha nega i e cycles s a dis o ing be o e
he posi i e ones. Anyway, a he poin o 1dB comp ession
his e ec is s ill small allowing a measu e o P
1dB
o be
ob ained wi h a -0.5dB e o . Would he posi i e cycles be
de ec ed ins ead, he cu e gi en by he RMS-DC con e e
would be abo e he LNA’s ue cu e wi h a la ge e o .
Fig. 11 – LNA’s powe ans e cha ac e is ic ob ained obse ing
i s ou pu di ec ly (*), using he RMS-DC de ec o (•), and
conside ing only he linea ideal cha ac e is ic.
VII. C
ONCLUSIONS
Ci cui s o s imuli gene a ion, swi ching, and powe
de ec ion a e p oposed o implemen a me hod o es a
LNA o 1dB comp ession and hi d-o de in e cep ion
poin s. Thei de elopmen is based on c i e ia seeking o
minimize powe consump ion and simplici y. Ano he
design d i ing aspec add esses he acili y o con olling
he es ope a ion and o obse ing he ou pu measu es
using digi al o low equency signals, making i easie o
in e ace his es scheme wi h gene al pu pose es e s.
The pe o mance o hese ci cui s is highly dependen on
he cha ac e is ics o he echnology being used, as well as
o he ope a ing equency. This is he case, namely, o he
induc o s’ quali y ac o which can ac ually be highe a
equencies highe han hose conside ed in his wo k. This
could lead, o example, o op o ano he ypology o
implemen he inpu swi ch.
In spi e o he simplici y o he ci cui s being p oposed,
good measu emen esul s can be ob ained. This conce ns
namely he RMS-DC con e e , which is based on a simple
hal -wa e ec i ie . Al e na i e, e en ually mo e accu a e,
RMS-DC con e e s o ecei ed signal s eng h indica o
ci cui s would p o ide mo e accu a e esul s a he cos o a
much highe complexi y and powe consump ion.
Being a con olled oscilla o a ailable a he LNA inpu ,
he blocks placed a e he LNA along he ecei e chain
can also be es ed in sequence.
R
EFERENCES
[1] In e na ional Technology Roadmap o Semiconduc o s, 2004
Edi ion. h p://public.i s.ne .
[2] Benoî R. Veille e and Go don W. Robe s, “A Buil -In Sel -
Tes S a egy o Wi eless Communica ion Sys ems”,
P oceedings o he In e na ional Tes Con e ence, 1995.
[3] E.A. McShane, K. Shenai, B. Blaes, “A monoli hic RF
mic osys em in SOI CMOS o low-powe ope a ion in
adia ion-in ense en i onmen s“ P oceedings o he IEEE
Ae ospace Con e ence, Vol. 5, pp. 421-429, Ma ch 2000.
[4] D. Lupea, U. Pu sche, H.J. Jen schel, “Spec al Signa u e
Analysis – BIST o RF F on -Ends”, Ad ances in Radio
Science, pp. 155-160, Vol.1, 2003.
[5] R. Voo aka anam, S. Che ubal, A. Cha e jee, “A Signa u e
Tes F amewo k o Rapid P oduc ion Tes ing o RF
Ci cui s”, P oceedings o he Design Au oma ion and Tes
Con e ence in Eu ope, 2002.
[6] Je zy Dab owski, “BiST Model o IC RF-T anscei e F on -
End”, 2003, P oceedings o he 18 h IEEE In e na ional
Symposium on De ec and Faul Tole ance in VLSI Sys ems
(DFT’03), 2003.
[7] S. Oze , C. Olgaa d, A. O ailoglu, “Tes abili y Implica ions in
Low-cos In eg a ed Radio T anscei e s: A Blue oo h Case
S udy”, P oceedings o he In e na ional Tes Con e ence,
2001.
[8] G. Pinho, J. Machado Sil a, H. Mendonça, and J. S. Ma os, "A
Tes Me hodology o Compu e Typical LNA Cha ac e iza ion
Pa ame e s ", P oceedings o he XVIII Con e ence on Design
o Ci cui s and In eg a ed Sys ems, No embe 2004.
[9] Thomas H. Lee, The Design o CMOS Radio- equency
In eg a ed Ci cui s, Camb idge Uni e si y P ess, 1998.
[10] C. Pa ick Yue, S. Simon Wong, “Design S a egy o On-
Chip Induc o s o Highly In eg a ed RF Sys ems”,
P oceedings o he Design Au oma ion Con e ence, 1999.
[11] F. Huang, K. O, “A 0.5-µm CMOS T/R Swi ch o 900-MHz
Wi eless Applica ions”, IEEE Jou nal o Solid S a e Ci cui s,
ol. 36, no. 3, pp. 486-492, Ma ch 2001.
[12] Ni anjan A. Talwalka , C. Pa ick Yue, Hai ao Gan, and S.
Simon Wong, ”In eg a ed CMOS T ansmi –Recei e Swi ch
Using LC-Tuned Subs a e Bias o 2.4-GHz and 5.2-GHz
Applica ions”, IEEE Jou nal o Solid-s a e Ci cui s, Vol. 39,
No. 6, Juns 2004.
[13] T. Tokumi su, I. Toyoda, M. Aikawa, “Low Vol age High
Powe T/R Swi ch MMIC Using LC Resona o s”, IEEE
Mic owa e and Millime e s-Wa e Monoli hic Ci cui s
Symposium, pp. 27-30, 1993.