Improved IP3 behaviour of the 900MHz Low Noise Amplifier with the NFG425W

Philips Semiconductors B.V.
Gerstweg 2, 6534 AE Nijmegen, The Netherlands
Report nr.
Author
Date
Department
: RNR-T45-96-B-1025
: T.F. Buss
: 10 Dec. 1996
: P.G. Transistors & Diodes, Development
IMPROVED IP3 BEHAVIOUR
OF THE 900MHz LOW NOISE AMPLIFIER
WITH THE BFG425W
UPDATE OF REPORT RNR-T45-96-B-771
Abstract:
This application note contains an example of a Low Noise Amplifier with the new BFG425W Double Poly
RF-transistor. The LNA is designed for a frequency f=900MHz, VSUP~3.8V, ISUP=10mA. Measured
performance at f=900MHz: Noise Figure NF~1.7dB, gain S21 ~17dB and the input IP3=+3dBm.
Appendix I: 900MHz LNA circuit
Appendix II: Printlayout and list of used components & materials
Appendix III: Results of simulations and measurements
1
Philips Semiconductors B.V.
Introduction:
With the new Philips silicon bipolar double poly BFG400W series, it is possible to design low noise
amplifiers for high frequency applications with a low current and a low supply voltage. These amplifiers are
well suited for the new generation low voltage high frequency wireless applications. In this note an example
of such an amplifier will be given. This amplifier is designed for a working frequency of 900MHz.
Designing the circuit:
The circuit is designed to show the following performance:
transistor: BFG425W
V ce=2V, Ic=10mA, V SUP~3.5V
freq=900MHz
Gain~18dB
NF<=1.6dB
IP3>0dBm (input)
VSWRi<1:2
VSWRo<1:2
In the simulations the effect of extra RF-noise caused by the SMA-connectors was omitted, so in the practical
situation the NF is ~0.1dB higher. This LNA is also optimised for the highest IP3. The IP3 can be optimised
by:
I. an extra series C-decoupling of the base to the ground
II. increasing IC
With the solution I. an extra component is necessary, and with solution II, the Noise Figure of the LNA
increases and the optimum source impedance also.
The in- and outputmatching is realised with a LC-combination. Also extra emitter-inductance on both emitterleads (µ-strips) are used to improve the matching and the Noise Figure.
Designing the layout:
A lay-out has been designed with HP-MDS. Appendix II contains the printlayout.
Measurements:
Simulations (with realistic RF-models of al used parts) and measurements of the total circuit
(epoxy PCB) are done (Appendix III).
2
Philips Semiconductors B.V.
Appendix I: Schematic of the circuit
C3
C6
C4
R1
+VSUP
C2
R3
R4
Coil_2
Coil_1
R2
OUT
50Ω
C5
IN
50Ω
C7
C1
W1
BFG425W
µS4:
µS4
L1
µS4
L2
D1
L3
W2
Figure 1: LNA circuit
900MHz LNA Component list: 900MHz LNA Component list:
Component
Value
Purpose, comment
R1
8.2 kΩ
Bias (coll.-base)
R2
10 Ω
in series with coll. for better S22, stability and reducing gain.
R3
22 Ω
RF blocking
R4
150 Ω
Bias, series with coll., cancelling hFE spread
C1
8.2 pF
Input match (input to base)
C2
27 pF
900 MHz short (L1 to ground)
C3
27 pF
900 MHz short (L2 to ground)
C4
100 nF
RF decoupling collector bias
C5
22 pF
Output match (collector to output)
C6
100 nF
To improve IP3 (by decoupling LF IP3 products)
C7
3.3 pF
Output match, stability (collector to emitter)
Coil_1
22 nH
Input match (base-bias)
Coil_2
12 nH
Output match (collector-bias)
µs4
(see
next µ-stripline Emitter-induction
table)
3
Philips Semiconductors B.V.
µS4 Emitter inductance of µ-stripline and via-hole (see on former page: Schematic of the circuit):
Name
Dimension Description
L1
2.5mm
length µ-stripline; Z0~48Ω (PCB: ε r ~4.6,
H=0.5mm)
L2
1.0mm
length interconnect stripline and via-hole area
L3
1.0mm
length via-hole area
W1
0.5mm
width µ-stripline
W2
1.0mm
width via-hole area
D1
0.4mm
diameter of via-hole
4
Philips Semiconductors B.V.
Appendix II: Printlayout and list of used components & materials
RFin
C1
C5
C7
C6
L1
R2
C2
C4
R1
L2
Vsup
R4
R3
C3
900MHz LOW NOISE AMP.
Figure 2: Printlayout
900MHz LNA Component list:
Component:
PCB
R1
R2
R3
R4
C1
C2
C3
C4
C5
C6
C7
L1
L2
Value:
FR4: ε r ~4.6
8.2 kΩ
10 Ω
22 Ω
150 Ω
8.2 pF
27 pF
27 pF
100 nF
22 pF
100 nF
3.3 pF
22 nH
12 nH
size:
H=0.5mm
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0805 Philips
0603 Philips
0805 Philips
0603 Philips
0805CS Coilcraft
0805CS Coilcraft
5
RFout
Philips Semiconductors B.V.
Appendix III: Results of simulations and measurements
Conditions: V SUP=3.7V, IC=10mA, f=900MHz
Simulation (HP-MDS):
|S21|2 [dB]
17.2
2
|S12| [dB]
-28.0
VSWRi
2.2
VSWRo
1.7
Noise Figure [dB]
1.6
IP3 [dBm] (input)
+1.3
Measurements PCB:
17.3
-28.3
2.5
1.8
1.7
+3
Comment:
note 1
∆f=200KHz, note 2
note 1: The Noise Figure of the PCB is higher than the simulations (~0.1 dB). This is caused by the influence
of the SMA-connectors and the microstrips on the epoxy PCB.
note 2: The IP3 of the PCB is higher than the simulations. This can be explained by the deviation of the Spice
parameters, used in the IP3 simulations, from the sample transistor-parameters used in the LNA.
W=Wvia
CMP230
MSVIA
CMP286
MSVIA
L=Lvi
SUBST=s10mi
a
model
cap.100nF
L=1 nH
C=1 nF
l
SUBST=s10mi
OD=0.4
W=Wvia
mm
L=1 nH
SUBST=s10mi
l OD=0.4 mm
l
L=Lvi
W=Wvia
CMP287
MSTL
R=0.3 OH
C=100 nF
SUBST=s10mi
LOW NOISE AMP. WITH [email protected]/10mA
model
cap.100nF
l
R1=22 OH
SUBST=s10mi
CMP236
MSTL
l
CMP405
MSTL
SUBST=s10mi
L=L3
SUBST=s10mi
l
SB1/[email protected]/10mA
CMP203
cmc_0603_phi
W=Wvia
L=Lvi
l
SUBST=s10mi
a
CMP281
cmc_0603_phi
W=W3CMP408
L=L3MSTL
SUBST=s10mi
l
SUBST=s10mi
L=0.5 mm
W=0.5 mm
SUBST=s10mi
l
CMP394
coilcraft_l1008
CMP358
MSTL
CMP197
cmc_0603_phi
W=W50_Ohm
L=6 mm
l
SUBST=s10mi
1 2
l
1
2
CMP431
SUBST=s10mi
R_nor
l
L=L4
W=W4
CMP438
cmc_0603_phi
CMP359
MSTL
CMP266
MSVIA
l
Ccmc=Cout
CMP403
MSTL
L=0.5 mm
W=0.5 mm
CMP5
MSSUBSTRATE
PORTNUM=2
CMP270
PORT_SPAR
R=50
JX=0
SUBST=s10mi
Ccmc=Ccex
ER=4.6
HU=1.0E+3 m l
MUR=1
T=35um
COND=5.8e07
H=0.5mm
ROUGH=10 um
AGROUND
TAND=0.02
CMP350
MSTL
CMP351
MSTL
W=0.5
L=L1
SUBST=s10mi
mm
W=0.5
L=L1
SUBST=s10mi
mm
l
l
W2=0.5
CMP250
MSTAPER
mm
W2=0.5
W1=Wvia_e
SUBST=s10mi
L=L2
SUBST=s10mi
W1=Wvia_e
L=L2
l
l
CMP180
MSVIA
W=Wvia_e
OD=0.4
mm
CMP252
MSTAPER
mm
SUBST=s10mi
CMP210
MSVIA
W=Wvia_e
OD=0.4
mm
SUBST=s10mi
Figure 3: HP-MDS simulation circuit
6
SUBST=s10mi
CMP227
MSTL
l
SUBST=s10mi
l
Ccmc=Contkop
L=0.5 mm
W=0.5 mm
_cs
CMP257
TWOPORT
DATA=DEBBY_425_2V_10m_1c.spar.SP.,freq=freq
CMP383
R1=Rout
MSTL
Ccmc=Cin
CMP18
PORT_SPAR
smd
l
W=W50_Ohm
L=6 mm
CMP401
PORTNUM=1MSTL
R=50
JX=0
L=3 mm
W=0.5 mm
CMP409
MSTL
Lx=Lout
W=W3
l
l
AGROUN
CMP406
MSTL
CMP399
coilcraft_l1008
Lx=Li
n
L=100 uH
l
1 2
R1=11
k
smd
_cs
1 2
CMP429
R_nor
W=0.5 mm
L=0.5 mm
SUBST=s10mi
R=0.3 OH
CMP428
R_nor
Ccmc=Contkop
CMP235
L
R1=39 OH
1 2
CMP430
R_nor
CMP419
R
l
CMP263
C
CMP264
R
W=Wvia
CMP417
L
CMP418
C
a
CMP289
cmc_0603_phi
CMP265
L
CMP231
MSTL
AGROUND
l
OD=0.4
mm
W=Wvia