ADS LNA Simulation Example

ADS LNA simulation example

ADS documentation

• Apart from the handed-out ADS tour: a lot more info on ADS and simulation tricks, know-how on http://www.agilent.com

Project data

• Project name: LNA_PRJ• Technology: CMOS 0.25 um (included via netlist

statement)• Number of networks: 9 (plus one sub-network)

• Description: Shows how to simulate all important specifications of a (common-source cascode) LNA. Output matching is not done, because after the LNA no external (50 Ohm) filter is anticipated: hence no need for matching (which cost 3 dB in gain)

Simulation of MOS characteristics

Set gate and drain voltage sweep limits as needed. If the transistor instance name changes (for example, MOSFET2 instead of MOSFET1), then the MOS_Gm equation must also be changed. If a library part is used on this schematic, then the MOS_Gm equation will have to be set to something like A1.Device.Gm.

FET Curve Tracer

MOSFET_NMOSMOSFET1

Width=100 umLength=0.25 umModel=nfet

DCDC1

Other=Step=0.1Stop=2.5Start=0SweepVar="VDS"

DCParamSweepSweep1

Step=0.1Stop=1.4Start=0SimInstanceName[6]=SimInstanceName[5]=SimInstanceName[4]=SimInstanceName[3]=SimInstanceName[2]=SimInstanceName[1]="DC1"SweepVar="VGS"

PARAMETER SWEEP

MeasEqnMeas1MOS_Gm=MOSFET1.Gm

EqnMeas

NetlistIncludeNetlistInclude1IncludeFiles[1]=generic025.lib

NETLIST INCLUDE

VARVAR1

VDS=0VGS=0

EqnVar

V_DCSRC1Vdc=VDS

V_DCSRC3Vdc=VGS

I_ProbeIDS

Schematic: FET_curve_tracer

Example of simulation output

m 1VDS=IDS.i=0.010VGS=0.900000

1.000m 1VDS=IDS.i=0.010VGS=0.900000

1.000

0.5 1.0 1.5 2.00.0 2.5

5

10

15

20

25

30

35

0

40

VGS=0.000VGS=0.100VGS=0.200VGS=0.300VGS=0.400VGS=0.500VGS=0.600VGS=0.700

VGS=0.800

VGS=0.900

VGS=1.000

VGS=1.100

VGS=1.200

VGS=1.300

VGS=1.400

VDS

IDS

.i, m

A

m 1

Device I-V Curves

m 2VDS=MOS_Gm =0.003VGS=0.500000

2.300m 2VDS=MOS_Gm =0.003VGS=0.500000

2.300

0.5 1.0 1.5 2.00.0 2.5

0.000

0.005

0.010

0.015

0.020

0.025

0.030

-0.005

0.035

VGS=0.000VGS=0.100VGS=0.200VGS=0.300VGS=0.400VGS=0.500

VGS=0.600

VGS=0.700

VGS=0.800

VGS=0.900VGS=1.000VGS=1.100VGS=1.200VGS=1.300VGS=1.400

VDS

MO

S_G

m

m 2

DC Transconducta nce ve rsus VDS

DC transfer curves to determine proper biasing voltage Vgs

DC and S-parameter simulation

Vdra in

Vga te

The S pa ra me te rs a re s imula te d to c he c k ga ina nd s ta bility.

I_P robeID

Te rmTe rm2

Z=300 OhmNum=2 V_DC

S RC1Vdc =2.5 V

V_DCS RC2Vdc =0.75 V

MOSFET_NMOSMOSFET1

Trise=Width=100 umLength=.25 umModel=nfet

MuP rimemup1mu_loa d=mu_prime (S )

MuP

rime

Mumu1mu_s ourc e =mu(S )

Mu

DCDC1

DC

Ne tlis tInc ludeNe tlis tInc lude 1Inc lude File s [1]=ge ne ric 025.lib

NETLIST INCLUDE

DC_Fe e dDC_Fe e d1

S _P a ra mS P 1

S te p=10 MHzS top=3.0 GHzS ta rt=10 MHz

S-PARAMETERSDC_Bloc kDCBloc k1

Te rmTe rm1

Z=50 OhmNum=1

Schematic: DC_and_Sparams

Port-impedance: “term” for Sparam simulation

Port-impedance: “term” for Sparam simulation

Stabilitymeasures


freq0.000 Hz

Vgate750.mV

Vdra in1.19 V

freq0.000 Hz

ID.i4.35mA Dc conditions

m2fre q=dB(S (2,1))=8.982

2.000GHzm2fre q=dB(S (2,1))=8.982

2.000GHz

0.5 1.0 1.5 2.0 2.50.0 3.0

-40

-20

0

-60

20

freq, GHz

dB(S

(1,2

))dB

(S(2

,1))

m2

freq (10.00MHz to 3.000GHz)

S(1

,1)

S(2

,2)

S-parameters

Target for S11: 50 Ohm

gain

Reverse-isolation

DC and S-parameter simulation: cascode LNA

Vg a te

Vin

Vdra in

Vout

T he S pa ra m e te r s a r e s im ula te d to c he c k g a ina nd s ta b ility.D A_S m ithC ha r tM a tc h1_D C _a nd_S pa r a m s _c a s c a de

D A_S m ithC ha r tM a tc h1

Z 0= 50 O hmZ l= (50 .00- j*127.5) O hmZ s = 50 O hmF = 1.9 G H z

S _P a ra mS P 1

S te p= 10 M H zS top= 3 .0 G H zS ta r t= 10 M H z

S -P A R A M E T E R S

M uP r im em up1m u_loa d= m u_pr im e (S )

MuP

rime

D CD C 1

D C

M um u1m u_s our c e = m u( S )

Mu

I_P robeID

LL1

R =L= 1.05 nH

T e r mT e r m 2

Z = 100 O hmN um = 2

M e a s E q nM e a s 1Vds _c a s c a de = Vout- Vdra in

Eq nMe a s

D C _Bloc kD C Bloc k1

T e rmT e rm 1

Z = 50 O hmN um = 1

V_D CS R C 2Vdc = 0.75 V

MO S F E T _ N MO SMO S F E T 2

T ris e =W id th =1 0 0 u mLe n g th = 0 .2 5 u mMo d e l=n fe t

MO S F E T _ N MO SMO S F E T 1

T ris e =W id th = 1 0 0 u mLe n g th = 0 .2 5 u mMo d e l= n fe t



D C _F e e dD C _F e e d1

N e tlis tInc ludeN e tlis tInc lude 1Inc lude F ile s [1 ]= g e ne r ic 025 .lib

N E T L IS T IN C LU D E

Smith –chart component first disabled and shorted to see un-matched S11

Cascode LNA for improved stability and isolation and less miller effect

Schematic: DC_and_Sparams_cascode


m3freq=S(1,1)=0.793 / -37.940impedance = Z0 * (0.983 - j2.579)

1.900GHz


S(1

,1)

m3S

(2,2

)

Coil in source has right value, but inductive matching network needed

m2freq=dB(S(2,1))=9.109

2.000GHz

0.5 1.0 1.5 2.0 2.50.0 3.0

-80

-60

-40

-20

0

-100

20

freq, GHz

dB(S

(1,2

))dB

(S(2

,1))

m2

Improved isolation due to cascode stage (and thus stability)


• Same schematic but smith-chart component enabled

Vgate

Vin

Vdrain

Vout

The S parameters are s imulated to check gainand s tability.DA_SmithChartMatch_DC_and_Sparams_cascode

DA_SmithChartMatch1

Z0=50 OhmZl=(50+j*0) OhmZs=(50+j*0) OhmF=1 GHz

S_ParamSP1

Step=10 MHzStop=3.0 GHzStart=10 MHz

S -P ARAMETERS

MuPrimemup1mu_load=mu_prime(S)

MuP

rime

DCDC1

DC

Mumu1mu_source=mu(S)

Mu

I_ProbeID

LL1

R=L=1.05 nH

TermTerm2

Z=100 OhmNum=2

MeasEqnMeas1Vds_cascade=Vout-Vdrain

E qnMeas

DC_BlockDCBlock1

TermTerm1

Z=50 OhmNum=1

V_DCSRC2Vdc=0.75 V

MOSFET_NMOSMOSFET2

Tris e =Width=100 umLe ngth=0.25 umMode l=nfe t

MOSFET_NMOSMOSFET1


V_DCSRC3Vdc=1.8 V

V_DCSRC1Vdc=2.5 V

DC_FeedDC_Feed1

Netlis tIncludeNetlis tInclude1IncludeFiles[1]=generic025.lib

NETLIS T INCLUDE

Schematic: DC_and_Sparams_cascode

Use design guide to match input (I)

• In schematic, ADS Menu: DesignGuide→filter→smith chart control window

Set frequency at 1.9 GHzunmark: normalized impedances

Click On Zl

Fill in S11impedance

Use design guide to match input (II)

S1149.1-j128.95

After entry, press enter

Use design guide to match input (III)

Select series inductance

Move around smith chart until matched

Last step: build ADS circuit

Click on this button

Lumped Element Low P as s Filter Des ign As s is tantNeed Help? P leas e s ee the appropriate Des ignGuide Us er Manual

P ortP 2Num=2

LL1

R=1e-12 OhmL=10.756248 nH

P ortP 1Num=1

VARVAR1P arameters ="#1.9 GHz#50 Ohm#(49.10-j*128.9) Ohm#50 Ohm"

EqnVar

Automatically creates this sub-network

Repeat simulation of schematic:DC_and_Sparams_cascode

m2freq=dB(S(2,1))=13.063

2.000GHz

0.5 1.0 1.5 2.0 2.50.0 3.0

-80

-60

-40

-20

0

-100

20

freq, GHz

dB(S

(1,2

))dB

(S(2

,1))

m2

m3freq=S(1,1)=0.010 / -148.430impedance = Z0 * (0.983 - j0.010)

1.900GHz


S(1

,1) m3

S(2

,2)

Improved gain (4 dB) and minimum return loss due to input matching.


• Same schematic as previous schematic but with smith chart component replaced by coil (~ 10 nH)

Vgate

Vin

Vdra in

Vout

The S parameters a re s imulated to check ga inand s tability .

LL2

R=L=10.6 nH

S_ParamSP1

Step=10 MHzStop=3.0 GHzStart=10 MHz

S -P ARAMETERS

Mumu1mu_s ource=mu(S)

Mu

Netlis tIncludeNetlis tInclude1Inc ludeFiles [1]=generic025.lib

NETLIS T INCLUDE

MuPrimemup1mu_load=mu_prime(S)

MuP

rime

DCDC1

DC

I_ProbeID

LL1

R=L=1.05 nH

TermTerm2

Z=100 OhmNum=2

Meas EqnMeas 1Vds _cas cade=Vout-Vdrain

EqnMe a s

DC_BlockDCBlock1

TermTerm1

Z=50 OhmNum=1

V_DCSRC2Vdc=0.75 V

MOS FET_NMOSMOS FET2

Tris e=Width=100 umLe ngth=0.25 umModel=nfe t

MOS FET_NMOSMOS FET1


V_DCSRC3Vdc=1.8 V

V_DCSRC1Vdc=2.5 V

DC_FeedDC_Feed1

Schematic: DC_and_Sparams_cascode_match

AC simulation for noise figure

N o t ic e t h a t f o r t h is f irs tn o is e s im u la t io n t h e q u a lit yf a c t o r o f t h e t w o in d u c t o rsis in if it e (o n re a lis t ic : s e ef o r a m o re re a lis t ic n o is ef ig u re LN A _ n o is e _ re a l_ Q ).

V in V g a t e

V o u t

V d ra in

N e t lis t In c lu d eN e t lis t In c lu d e 1In c lu d e F ile s [1 ]= g e n e r ic 0 2 5 . lib

NETLIS T INC LUDE

LL1

R =L= 1 . 0 n H

LL2

R =L= 1 0 . n H

Te rmTe rm 2

Z = 1 0 0 O h mN u m = 2

M O S F E T _ N M O SM O S F E T 2

T r is e =W id th = 1 0 0 u mLe n g th = 0 .2 5 u mM o d e l= n fe t

A CA C 1

In c lu d e P o rt N o is e = y e sS o r t N o is e = S o r t b y v a lu eN o is e N o d e [2 ]= "V in "N o is e N o d e [1 ]= "V o u t "C a lc N o is e = y e sS t e p = 1 0 0 MH zS t o p = 3 G H zS t a rt = 1 0 0 MH zS w e e p V a r= "f re q "

A C

M O S F E T _ N M O SM O S F E T 1

T r is e =W id th = 1 0 0 u mLe n g th = 0 .2 5 u mM o d e l= n fe t

P _ A CP O R T1

F re q = f re qP a c = p o la r(d b m t o w (0 ), 0 )Z = 5 0 O h mN u m = 1

I_ P ro b eID

D C _ B lo c kD C B lo c k 1

V _ D CS R C 2V d c = 0 . 7 5 V

V _ D CS R C 3V d c = 1 . 8 V

V _ D CS R C 1V d c = 2 . 5 V

D C _ F e e dD C _ F e e d 1

Schematic: LNA_noise

Coils are ideal here: no losses included yet


Eqn NF=20*log((Vout.noise/(mag(Vout/Vin)))/PORT1.t1.v.noise)

Measurement equation used to calculated the noise figure

m1freq=NF=0.703

1.900GHz

0.5 1.0 1.5 2.0 2.50.0 3.0

1

2

3

4

0

5

freq, GHz

NF

m1

Noise figure versus frequency

AC simulation for noise figure with realistic coils

Both Induc tors nowhave a s e rie s re s is tormaking the qua lity fac torof the c ompone nt approx7

Vin Vga te

Vout

Vdra in

LL1

R=1.7L=1 nH

LL2

R=18L=10. nH

Ne tlis tInc ludeNe tlis tInc lude 1Inc ludeFile s [1]=gene ric025.lib

NETLIST INCLUDETermTerm2

Z=100 OhmNum=2

MOSFET_NMOSMOSFET2

Trise=Width=100 umLength=0.25 umModel=nfet

ACAC1

Inc ludeP ortNois e =ye sS ortNois e=S ort by va lueNois e Node[2]="Vin"Nois e Node[1]="Vout"Ca lcNois e=yesS te p=100 MHzS top=3 GHzS ta rt=100 MHzS weepVa r="fre q"

AC

MOSFET_NMOSMOSFET1

Trise=Width=100 umLength=0.25 umModel=nfet

P _ACP ORT1

Freq=freqP ac =pola r(dbmtow(0),0)Z=50 OhmNum=1

I_P robeID

DC_Bloc kDCBlock1

V_DCS RC2Vdc =0.75 V

V_DCS RC3Vdc =1.8 V

V_DCS RC1Vdc=2.5 V

DC_Fee dDC_Fee d1

Resistance in coils set to have a quality factor of about 7

Schematic: LNA_noise_real_Q


m1freq=NF=1.471

1.900GHzm1freq=NF=1.471

1.900GHz

0.5 1.0 1.5 2.0 2.50.0 3.0

2

3

4

1

5

fre q, GHz

NF

m1

Notice tha t the nois e figurehas degraded s ignificantlydue to the the rmal nois e of the s e rie s re s is tancesin the inductors

Example of sweeping a parameter

Vin Vga te

Vout

Vdra in

Netlis tInc ludeNetlis tInc lude1Inc ludeFile s [1]=gene ric025.lib

NETLIST INCLUDE

P aramS weepS weep1

S tep=0.5e-9S top=15e -9S ta rt=1e -9S imIns tanceName[6]=S imIns tanceName[5]=S imIns tanceName[4]=S imIns tanceName[3]=S imIns tanceName[2]=S imIns tanceName[1]="AC1"S weepVar="s ource ind"

PARAMETER SWEEPLL2

R=L=s ource ind

VARVAR1s ource ind=1e -9

E qnVar

LL1

R=L=1.0 nH

TermTerm2

Z=100 OhmNum=2

MOSFET_NMOSMOSFET2


ACAC1

Inc ludeP ortNois e=yesS ortNois e=S ort by va lueNois eNode [2]="Vin"Nois eNode [1]="Vout"CalcNois e=yesS tep=100 MHzS top=3 GHzS ta rt=100 MHzS weepVar="freq"

AC

MOSFET_NMOSMOSFET1


P _ACP ORT1

Freq=freqP ac=pola r(dbmtow(0),0)Z=50 OhmNum=1

I_P robeID

DC_BlockDCBlock1

V_DCS RC2Vdc=0.75 V

V_DCS RC3Vdc=1.8 V

V_DCS RC1Vdc=2.5 V

DC_FeedDC_Feed1 Parameter

sweep block included

Schematic: LNA_noise_sweep

Matching inductor is varied from 1 to 15 nH(coils have infinite Q)


m1freq=NF=0.669sourceind=1.100000E-8

1.900GHz

0.5 1.0 1.5 2.0 2.50.0 3.0

2

4

6

0

8

freq, GHz

NF

m1

Lg ~ 10.7 nH close to the optimum value

Gain and 1dB compression simulation

Vin Vg a te

Vou t

Vdra in

Me a s E q nMe a s 1Vo u t_ dBm =d Bm (Vou t[1 ])

Eq nMe a s

VARVAR 1R F _powe r=-3 5

Eq nVa r

H a rm o n ic Ba la nc eH B1

S te p =1S top =10S ta rt=-50S we e pVa r="R F _po we r"O rd e r[1 ]=3F re q [1 ]=1 .9 G H z

HAR MO NIC BALANCE

V_D CS R C 1Vdc =2 .5 V

V_D CS R C 3Vdc =1 .8 V

N e tlis tInc lud eN e tlis tInc lud e 1In c lude F ile s [1 ]=ge n e ric 0 25 . lib

NE T LIS T INCLUDE

P _1 ToneP O R T1

F re q=1 .9 G H zP =d bm tow(R F _p owe r)Z =5 0 O h mN um =1

LL1

R =1 .7L=1 nH

LL2

R =18L=1 0 . nH

Te rmTe rm 2

Z =1 00 O hmN um =2

MOS FE T _ NMOSMOS FE T 2

T ris e =W id th =1 0 0 u mLe n g th =0 .2 5 u mMo d e l=n fe t

MOS FE T _ NMOSMOS FE T 1

T ris e =W id th =1 0 0 u mLe n g th =0 .2 5 u mMo d e l=n fe t

I_ P robeID

D C _Bloc kD C Bloc k 1

V_D CS R C 2Vdc =0 .75 V D C _F e e d

D C _F e e d1

From sources-freq. domain: P_1 tone source.RF_power is the sweep variable

Schematic: LNA_1dB_by_power_sweep

Initialization by means of Var (main menu) needed

HBcontroller

Meas eq.


Equation defining the line

Eqn Line =RF_power+dB_ga in[0]

m4ind De lta =de p De lta =-1.025de lta mode ON

0.000

m3RF_powe r=Line =8.016

-7.000

m4ind De lta =de p De lta =-1.025de lta mode ON

0.000

m3RF_powe r=Line =8.016

-7.000

-40 -30 -20 -10 0-50 10

-30

-20

-10

0

10

20

-40

30

RF_power

Vou

t_dB

m

m4Li

ne

m3

m1RF_power=Vout_dBm=9.265

-4.000

-40 -30 -20 -10 0-50 10

-30

-20

-10

0

10

-40

20

RF_power

Vou

t_dB

m

m1

Voltage gain ~ 15 dB

Input power for 1 dB compression

Simulation of IIP3

Vin Vg a te

Vd ra in

O rd e r 4 me a n s th a t Fre q [1 ] w illb e c a lc u la te d w ith 4 h a rmo n ic s

O u tp u t IP3 (O IP3 )

1 5 is th e s ma ll s ig n a l p o w e rg a in in d B o f th e LN A, w h ic h is ta k e n fro mth e 1 d B c o mp re s s io n s imu la tio ns c h e ma tic .

In p u t IP3 (IIP3 )To c a lc u la te th e in p u t IP3th e g a in o f th e LN A is n e e d e d

Vo u t

VARVAR 1

R F_ p o w e r=-3 5R F_ fre q =1 .9 G H zs p a c in g =1 MH z

E q nVa r

P_ n To n ePO R T1

P[2 ]=d b mto w (R F_ p o w e r)P[1 ]=d b mto w (R F_ p o w e r)Fre q [2 ]=R F_ fre q - s p a c in g /2Fre q [1 ]=R F_ fre q + s p a c in g /2Z=5 0 O h mN u m=1

H a rmo n ic Ba la n c eH B1

O rd e r[2 ]=4O rd e r[1 ]=4Fre q [2 ]=R F_ fre q -s p a c in g /2Fre q [1 ]=R F_ fre q +s p a c in g /2

HARMO NIC BALANCE

IP3 o u tip o 2ip o _ lo w e r=ip 3 _ o u t(Vo u t,{1 ,0 },{-1 ,2 },5 0 )

P0

Pin

IP 3out

IP3 o u tip o 1ip o _ u p p e r=ip 3 _ o u t(Vo u t,{1 ,0 },{2 ,-1 },5 0 )

P0

Pin

IP 3out

IP3 inIP3 in 1IP3 in 1 =ip 3 _ in (Vo u t,1 5 ,{1 ,0 },{2 ,-1 },5 0 )

P0

Pin

IP 3in

N e tlis tIn c lu d eN e tlis tIn c lu d e 1In c lu d e File s [1 ]=g e n e r ic 0 2 5 .lib

NE TLIS T INCLUDE

Me a s Eq nMe a s 2to n e s =[{1 ,0 },{0 ,1 },{2 ,-1 },{-1 ,2 }]

E q nM e a s

LL1

R =1 .7L=1 n H

Me a s Eq nMe a s 1Vo u t_ d Bm=d Bm(Vo u t[1 ])

E q nM e a s

MOS FE T_NMOSMOS FE T1

Tris e=W idth=100 umLength=0.25 umModel=nfe tL

L2

R =1 8L=1 0 .6 n H

V_ D CSR C 1Vd c =2 .5 V

V_ D CSR C 3Vd c =1 .8 V

Te rmTe rm2

Z=1 0 0 O h mN u m=2

MOS FE T_NMOSMOS FE T2

Tris e=W idth=100 umLength=0.25 umModel=nfet

I_ Pro b eID

D C _ Blo c kD C Blo c k 1

V_ D CSR C 2Vd c =0 .7 5 V D C _ Fe e d

D C _ Fe e d 1

Schematic: LNA_IIP3

From sources-freq. domain: P_ntone source.Two tones are defined

Predefined equationsDef. of tones of interest

Mix –function in ADS

• Purpose: Returns a component of a spectrum based on a vector of mixing indices.

• Synopsis mix(xOut, harmIndex{, Mix}) – where – xOut is a voltage or a current spectrum. – harmIndex is the desired vector of harmonic frequency

indices (mixing terms). – Mix is a variable consisting of all possible vectors of

harmonic frequency indices (mixing terms) in the analysis.• Example: y = mix(vOut, {2, -1})


IP 3in11.333

ipo_lower16.332

ipo_upper16.333

Notice tha t the upper and lower third orde r inte rceptpoints a re a lmos t symmetrica l (ipo_uppe r and ipo_lower). The input IP 3 (IP 3in1) is s imply 15 dBlower (the small s igna l ga in) than the output IP 3

freq

0.0000 Hz1.000MHz2.000MHz1.898GHz1.899GHz1.901GHz1.902GHz3.798GHz3.799GHz3.800GHz3.801GHz3.802GHz5.698GHz5.699GHz5.700GHz5.702GHz7.598GHz7.599GHz7.600GHz7.601GHz7.602GHz

MixMix(1) Mix(2)

012

-1012

-10123012301234

0-1-2210

-13210

-1321043210

This is the so-ca lled mix table of the ha rmonic ba lance s imula tion. Number 1 represents the RF tone (with spacing). Zero means tha t notone is present (DC). And two represents two times the RF s imula tion tone (of Freq[1] or Freq[2]).

m1freq=dBm(mix(Vout,tones))=-19.934

1.899GHz

m2freq=dBm(mix(Vout,tones))=-19.939

1.901GHz

1.8990 1.8995 1.9000 1.9005 1.90101.8985 1.9015

-80

-60

-40

-20

-100

0

freq, GHz

dBm

(mix

(Vou

t,ton

es)) m1 m2

Documents

ADS LNA Simulation Example