December 2, 1997

BF P640 F
AN 179
High Gain , Hi gh IP3 G PS L NA us ing
BF P640 F Si Ge: C Tr ans is to r
Applic atio n N ote
Revision: Rev 1.2,
2011.09.29
RF and P r otecti on D evic es
Edition 2011-09-29
Published by
Infineon Technologies AG
81726 München, Germany
© Infineon Technologies AG 2011.
All Rights Reserved.
LEGAL DISCLAIMER
THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE
IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL
NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN
FUNCTIONALITY, CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES
COMPONENT. THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY
FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION. INFINEON TECHNOLOGIES
HEREBY DISCLAIMS ANY AND ALL WARRANTIES AND LIABILITIES OF ANY KIND
(INCLUDING WITHOUT LIMITATION WARRANTIES OF NON-INFRINGEMENT OF
INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD-PARTY) WITH RESPECT TO ANY AND
ALL INFORMATION GIVEN IN THIS APPLICATION NOTE.
Information
For further information on technology, delivery terms and conditions and prices please contact
your nearest Infineon Technologies Office (www.infineon.com).
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Due to technical requirements components may contain dangerous substances. For information
on the types in question please contact your nearest Infineon Technologies Office.
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Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Application Note No. 179
Revision History: 2009-01-12, Rev 1.0
2009-01-16, Rev 1.1
2011-09-29, Rev 1.2
Previous Version:
Page
Subjects (major changes since last revision)
4
Correction of errors (V1.0 =>V1.1)
4
Correction of errors in „Summary Of Performance Data‟ (V1.1 => V1.2)
Trademarks
SIEGET® is a registered trademark of Infineon Technologies AG.
Additional Information:
More details about Infineon RF Transistors may be found at www.infineon.com/RF
Direct link to RF Transistor Datasheets / Specifications: www.infineon.com/rf.specs
For S-Parameters, Noise Parameters, SPICE models: www.infineon.com/rf.models
For Application Notes: www.infineon.com/rf.appnotes
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
1
High Gain, High Third-Order Intercept Low Noise Amplifier for 1575 MHz
GPS Applications using the BFP640F SiGe:C Low Noise RF Transistor
Overview
 Infineon Technologies‟ BFP640F is a high gain, low noise Silicon-Germanium-Carbon (SiGe:C)
Heterojunction Bipolar Transistor (HBT) suitable for a broad range of Low Noise Amplifier
(LNA) applications.
2

This circuit is targeted for 1575 MHz „L1‟ frequency GPS applications. The LNA has high
linearity / high Third Order Intercept (IP3) performance, useful in reducing the magnitude of
potential spurious signals generated in the LNA by strong out-of-band signals. Additional
charge storage (capacitance) is used to achieve a reduction in Third-Order distortion, with the
penalty of increased turn-on / turn-off times. Reference [1] describes in detail how additional
charge storage reduces Third Order product levels. Both In-Band and Out-Of-Band IP3 tests
are performed, with the Out-Of-Band test being done in such a way as to enable prediction of
levels of a potential spurious signal falling at the desired 1575.42 MHz GPS frequency if the
amplifier is injected with signals that could be present in or around a multi-band mobile phone.
Amplifier is Unconditionally Stable (1 > 1.0) from 10 MHz – 12 GHz.

External parts count (not including BFP640F transistor) = 10; 5 capacitors, 3 resistors, & 2 chip
inductors. All passives are „0402‟ case size.
Summary Of Performance Data
(T=25 C, network analyzer source power  -25 dBm, VCC = 2.8 V, VCE = 2.4 V, IC=8.6 mA, ZS=ZL=50  )
Frequency
* NF ** IIP3 ** OIP3 IP1dB OP1dB
MHz
dB[s11]2 dB[s21]2 dB[s12]2 dB[s22]2 dB dBm
dBm dBm dBm
900
- 3.4
17.9
-32.5
-4.8
----------1575
-11.8
18.4
-24.9
-11.7
0.7
+5.8
+24.2 -14.1 +3.3
1800
-18.0
13.9
-20.0
-16.0
0.7
--------2400
-15.6
14.8
- 22.3
- 5.5
0.8
--------* does not extract PCB loss. If PCB loss (at input) were extracted, noise figure would be ~ 0.1 dB lower.
** In-band IIP3 result.
Turn-on time: ~ 1.5 milliseconds; Turn-Off Time ~ 30 microseconds. Please see pages 24 – 26.
3
Details of PC Board Construction
PC board is fabricated from standard, low-cost “FR4” glass-epoxy material. A cross-section diagram of
the PC board is given below.
PCB CROSS SECTION
TOP LAYER (RF TRACES)
0.010 inch / 0.254 mm
INTERNAL GROUND PLANE
0.031 inch / 0.787 mm ?
LAYER FOR MECHANICAL RIGIDITY OF PCB, THICKNESS HERE NOT
CRITICAL AS LONG AS TOTAL PCB THICKNESS DOES NOT EXCEED
0.045 INCH / 1.14 mm (SPECIFICATION FOR TOTAL PCB THICKNESS:
0.040 + 0.005 / - 0.005 INCH;
1.016 + 0.127 mm / - 0.127 mm )
BOTTOM LAYER
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
4
TSFP-4 Package Outline & Footprint. Dimensions in millimeters (mm).
Refer to BFP640F Datasheet [2] for emitter – base – collector pin assignments.
Application Note
5 / 28
Rev. 1.2, 2011-09-29
Application Note
6 / 28
C1
22pF
L1
22nH
R1
15 ohms
PCB = 640F-021904 Rev A
PC Board Material = Standard FR4
C2
1.8pF
C4
5.6pF
C5
0.1uF
( BFP640F Vce = 2.4 V )
L2
8.2nH
Q1
BFP640F SiGe:C
Low Noise Transistor
R2
47K
R3
27 ohms
J2
RF OUTPUT
Inductive Emitter Degeneration (Microstrip Inductors) for IP3 improvement, Low Frequency Stability Improvement & RF matching.
Width = 0.010 inch / 0.25 mm,
Length = 0.035 inch / 0.89 mm
J1
RF INPUT
Black rectangles are 50 ohm microstrip
tracks, not chip components !
C3
0.1uF
Inductors L1 & L2 are Murata LQP15M Series
I = 8.6 mA
5
J3
DC Connector
Vcc = 2.80 V
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Schematic Diagram
Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
6
Bill Of Material (BOM)
Reference
Designator
Value
C1
C2
C3
22pF
1.8pF
0.1uF
C4
Manufacturer
Function
„0402‟ chip capacitor
„0402‟ chip capacitor
„0402‟ chip capacitor
Various
Various
Various
5.6pF
„0402‟ chip capacitor
Various
C5
0.1uF
„0402‟ chip capacitor
Various
Input DC block
Output DC block, output match
Low frequency decoupling /
blocking cap; improves thirdorder intercept (TOI). Please
refer to Reference [1], pages
RF decoupling / blocking cap;
also has some influence on
stability and output match
Low frequency decoupling /
blocking cap; improves thirdorder intercept (TOI). Please
refer to Reference [1], pages
L1
22nH
„0402‟ case size chip inductor
Murata LQP15M Series or equivalent
Murata
L2
8.2nH
„0402‟ case size chip inductor
Murata LQP15M series or equivalent
Murata
R1
15
„0402‟ chip resistor
Various
R2
R3
47k
27
„0402‟ chip resistor
„0402‟ chip resistor
Various
Various
Q1
---
J1, J2
J3
---
Application Note
Description / Part #
BFP640F SiGe:C Low Noise RF
Transistor, TSFP-4 package
Infineon
Technologies
RF Edge Mount SMA Female Connector,
142-0701-841
MTA-100 Series 5 pin connector
640456-5
PC Board,
Part # 640F-021904 Rev A
7 / 28
RF Choke at LNA input (for DC
bias to base).
RF „Choke‟ at LNA output, for
DC bias to collector.
Also
influences
matching
and
stability.
For RF stability improvement.
Not a DC bias component.
DC biasing (base current).
DC biasing (provides DC
negative feedback to stabilize
DC operating point over
temperature
variation,
transistor hFE variation, etc.)
LNA active device.
Emerson /
Johnson
Input, Output RF connector
Tyco (AMP)
Infineon
Technologies
5 Pin DC connector header
Printed Circuit Board
Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
7
Scanned Images of PC Board
View of Entire PC Board
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Close-In View of LNA Section
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
8
Noise Figure Measurement Data
Noise Figure Plot, from Rohde and Schwarz FSEK3 + FSEM30
Rohde & Schwarz FSEK3
14 Jan 2009
Noise Figure Measurement
EUT Name:
Manufacturer:
Operating Conditions:
Operator Name:
Test Specif ication:
Comment:
BFP640F High Linearity GPS LNA - AN179
Inf ineon Technologies
T=25 C, V = 2.8 V, Vce = 2.4 V, I = 8.6 mA
Gerard Wevers
GPS
PCB = 640F-021904 Rev A; Preamp = MITEQ SMC-02
12 January 2009
Analyzer
RF Att:
Ref Lvl:
0.00 dB
-50.00 dBm
RBW :
VBW :
1 MHz
100 Hz
Range:
30.00 dB
Ref Lvl auto:
ON
Measurement
2nd stage corr:
ON
Mode:
Direct
ENR: 346A_1.ENR
Noise Figure /dB
1.30
1.20
1.10
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
1475 MHz
Application Note
20 MHz / DIV
10/ 28
1675 MHz
Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Noise Figure, Tabular Data
Taken With Rohde & Schwarz FSEM30 + FSEK3
System Preamplifier = MITEQ SMC-02
Frequency
1475 MHz
1485 MHz
1495 MHz
1505 MHz
1515 MHz
1525 MHz
1535 MHz
1545 MHz
1555 MHz
1565 MHz
1575 MHz
1585 MHz
1595 MHz
1605 MHz
1615 MHz
1625 MHz
1635 MHz
1645 MHz
1655 MHz
1665 MHz
1675 MHz
Application Note
Nf
0.75 dB
0.76 dB
0.72 dB
0.73 dB
0.74 dB
0.73 dB
0.72 dB
0.73 dB
0.73 dB
0.74 dB
0.74 dB
0.71 dB
0.73 dB
0.72 dB
0.69 dB
0.74 dB
0.74 dB
0.72 dB
0.75 dB
0.73 dB
0.71 dB
11/ 28
Temp
54.6 K
55.4 K
52.3 K
53.2 K
54.2 K
53.4 K
52.1 K
52.9 K
53.4 K
54.2 K
53.5 K
51.3 K
53 K
52.4 K
50.3 K
53.9 K
53.6 K
52.2 K
54.7 K
52.9 K
51.3 K
Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
9
Amplifier Compression Point Measurement
Gain Compression at 1575.42 MHz, VCC = +2.8 V, I = 8.6mA, VCE = 2.4V, T = 25C:
Rohde & Schwarz ZVB20 Vector Network Analyzer is set up to sweep input power to LNA in a
“Power Sweep” at a fixed frequency of 1575.42 MHz. ZVB20 Port 1, which provides INPUT
power to drive the LNA, has its power level calibrated with the NRP-Z21 power sensor to ensure
power level accuracy with the reference plane at the RF input connector of the amplifier. X-axis
of VNA screen-shot below shows input power to LNA swept from –30 to –5 dBm.
Input 1 dB compression point = -14.1 dBm
Output 1dB compression point = -14.1 dBm + (Gain – 1dB) = -14.1 dBm + 17.4 dB = +3.3 dBm
Trc3 S21 dB Mag 1 dB / Ref 18 dB
Cal int PCal Smo Offs
3 of 4 (Max)
M 1 -29.14 dBm
• M 2 -14.06 dBm
S21
18.417 dB
17.416 dB
20
19
M1
18
M2
17
16
15
14
13
12
Ch1
Start -30 dBm
Freq 1.57542 GHz
Stop -5 dBm
1/12/2009, 10:25 PM
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
10
Amplifier Stability, Gain, Return Loss and Reverse Isolation Plots
Rohde and Schwarz ZVB Network Analyzer Calculates and plots stability factor “1” of the BFP640F
amplifier in real time. Stability Factor

1
1 is defined as follows [1]:
1 - |S11|2
=
| S22 – S11* det(S) | + |S21S12|
The necessary and sufficient condition for Unconditional Stability is 1 > 1.0. In the plot, 1 > 1.0
over 10 MHz – 12 GHz; amplifier is Unconditionally Stable over 10 MHz – 12 GHz frequency range.
Trc3 µ1 Lin Mag 100 mU/ Ref 1 U
Cal Smo Offs
3 of 4 (Max)
• M 1 1.975420 GHz 1.0320
M 2 900.00000 MHz 1.2660
M 3 1.800000 GHz 1.0449
M 4 2.400000 GHz 1.0532
µ1
1700
U
U
U
U
1600
1500
1400
M
1300
2
1200
1100
MM3 1M 4
1000
900
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/12/2009, 4:58 AM
[1]. “Fundamentals of Vector Network Analysis”, Michael Hiebel, 4th edition 2008, pages 175 – 177, ISBN
978-3-939837-06-0
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Input Return Loss, Log Mag
10 MHz – 12 GHz Sweep
Trc3 S11 dB Mag 5 dB / Ref 0 dB
Cal Smo Offs
3 of 4 (Max)
M 1 1.575420 GHz -11.799
M 2 900.00000 MHz -3.4089
M 3 1.800000 GHz -15.208
• M 4 2.400000 GHz -15.610
S11
10
dB
dB
dB
dB
5
0
M2
-5
-10
M1
M3 M4
-15
-20
-25
-30
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/12/2009, 4:55 AM
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Input Return Loss, Smith Chart
Reference Plane = Input SMA Connector on PC Board
10 MHz – 12 GHz Sweep
Trc3 S11 Smith
Ref 1 U
Cal Smo Offs
3 of 4 (Max)
1
S11
M1
33.486
-j14.511
6.962
2
M 2 900.00000 MHz 44.208
-j85.353
2.072
M 3 1.800000 GHz 38.358
-j10.375
5
8.522
• M 4 2.400000 GHz 41.066
-j12.458
5.323
0.5
0
0.2
0.5
1
1.575420 GHz
2
5
Ω
Ω
pF
Ω
Ω
pF
Ω
Ω
pF
Ω
Ω
pF
10
MM3 4
M1
-5
M2
-0.5
-2
-1
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/12/2009, 4:55 AM
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Forward Gain. Input / Output Matching Circuits of LNA reduce gain in 2.4 – 2.5 GHz band.
10 MHz – 12 GHz Sweep
Trc3 S21 dB Mag 10 dB / Ref 0 dB
S21
13
M 2 MM
20
Cal Smo Offs
3 of 4 (Max)
M 1 1.575420 GHz 18.379
M 2 900.00000 MHz 17.893
M 3 1.800000 GHz 17.522
• M 4 2.400000 GHz 14.750
M4
dB
dB
dB
dB
10
0
-10
-20
-30
-40
-50
-60
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/12/2009, 4:56 AM
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Reverse Isolation
10 MHz – 12 GHz Sweep
Trc3 S12 dB Mag 10 dB / Ref 0 dB
Cal Smo Offs
3 of 4 (Max)
M 1 1.575420 GHz -24.897
M 2 900.00000 MHz -32.494
M 3 1.800000 GHz -23.854
• M 4 2.400000 GHz -22.304
S12
20
dB
dB
dB
dB
10
0
-10
MM
13
-20
-30
M4
M2
-40
-50
-60
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/12/2009, 4:56 AM
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Output Return Loss, Log Mag
10 MHz to 12 GHz Sweep
Trc3 S22 dB Mag 5 dB / Ref 0 dB
Cal Smo Offs
3 of 4 (Max)
M 1 1.575420 GHz -11.705
M 2 900.00000 MHz -4.7874
M 3 1.800000 GHz -8.3500
• M 4 2.400000 GHz -5.4592
S22
10
dB
dB
dB
dB
5
0
M2
M4
-5
M3
-10
M1
-15
-20
-25
-30
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/12/2009, 4:57 AM
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Output Return Loss, Smith Chart
Reference Plane = Output SMA Connector on PC Board
10 MHz to 12 GHz Sweep
Trc3 S22 Smith
Ref 1 U
Cal Smo Offs
3 of 4 (Max)
1
S22
M1
43.356
-j24.148
4.184
2
M 2 900.00000 MHz 18.959
-j30.665
5.767
M 3 1.800000 GHz 34.326
-j30.637
5
2.886
• M 4 2.400000 GHz 17.108
-j16.684
3.975
0.5
0
0.2
0.5
1
1.575420 GHz
2
5
Ω
Ω
pF
Ω
Ω
pF
Ω
Ω
pF
Ω
Ω
pF
10
M1
M4
M3
-5
M2
-0.5
-2
-1
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/12/2009, 4:57 AM
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
11
Amplifier In-Band Third Order Intercept (TOI) Measurement
In-Band Third Order Intercept (IIP3) Test.
Input Stimulus: f1=1575 MHz, f2=1576 MHz, - 20 dBm each tone.
Input IP3 = -20 + (51.5 / 2) = +5.8 dBm. Output IP3 = +5.8 dBm + 18.4 dB gain = +24.2 dBm.
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
12
Amplifier Out-Of-Band Third Order Intercept Measurement
Amplifier Two-Tone Test (Third Order Product which falls @ GPS L1 Frequency 1575.42 MHz):
This test is a check for a Third-Order distortion product which falls on top of desired GPS “L1” frequency of
1575.42 MHz. Input Tones are as follows:
f1 = L1 + 138 MHz = 1713.42 MHz, -16 dBm
f2 = L1 + 276 MHz = 1851.42 MHz, -16 dBm
One third order product (2f1-f2) generated in the LNA due to the amplifier third-order nonlinearities can fall
right at the desired 1575.42 MHz frequency, as follows:
2f1 – f2 = 2(1713.42MHz) – 1851.42 MHz = 1575.42 MHz
Photo of Input Test Tones, from signal generators
f1 = 1713.42 MHz
P = -16.0 dBm
Application Note
f2 = 1851.42 MHz
P = -16.0 dBm
21/ 28
Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
Photo below shows partial output spectrum of the LNA after being driven by test tones shown on
previous page. Markers are placed at the peak input tone and the “Left Hand” Third Order Product which
falls at 1575 MHz. The difference in amplitudes (“delta”) is read. Note the product 2f 1 – f2 is 54.2 dB
below the input test tone.
The Input Third Order Intercept (IIP3) with respect to the left-side IM product at 1575.42 MHz is as follows:
IIP3 = -16 dBm + (43.3 / 2) = +5.7 dBm.
2f1 – f2 product
falls on GPS
frequency of
1575.42 MHz
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
This additional image below shows the partial output spectrum of the LNA subjected to the input test
tones shown two pages back, however the markers are placed at the peak tone and the “Right Hand”
Third Order Product which falls at 1989.42 MHz. This “right-hand side” product is likely less relevant to
GPS receivers as it is “far away” (in terms of frequency) from the desired “L1” GPS frequency of 1575.42
MHz. Note the product 2f2 – f1 is 37.2 dB below the input test tone.
The Input Third Order Intercept (IIP3) with respect to the right-side IM3 product at 1989.42 MHz is as
follows:
IIP3 (right side) = -16 dBm + (37.2 / 2) = +2.6 dBm.
2f2 – f1 product
Application Note
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Rev. 1.2, 2011-09-29
Application Note No. 179
BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
13
Amplifier Turn-On / Turn-Off Time Measurements
The amplifier is tested for turn-on / turn-off time. See diagram below. The RF signal generator runs
continuously at a power level sufficient to drive the output of the LNA to approximately 0 dBm when the
LNA has DC power ON.
Agilent DSO6104A
Digital Oscilloscope
+Vcc to amplifier
„Scope
Probe
+DC Pin
Amplifier
3 dB
Attenuator
Pad
RF Signal
Generator
Agilent
8473B
Detector
Ch. 1 (Trigger, edge)
1 Megaohm input Z
Ch. 2 ( 1 Megaohm or
50 ohm input Z)
! Note !
It may be necessary to set Ch. 2 Input Impedance to 50 ohms instead
of 1M ohm. 1M ohm setting may not allow detector to discharge
rapidly, depending on detector type and detector‟s output capacitance,
and might give erroneous results to turn-off time measurement, e.g.
could indicate excessively long turn-off times. The user can test turnoff time with Ch. 2 input impedance set to 1M ohm and then 50 ohms
and see if the two results differ.
1. Signal Generator set such that output power of Amplifier is ~ 0 dBm when LNA is
powered ON
2. Channel 1 of oscilloscope monitors input power supply voltage to Amplifier (+1.8,
+2.8 or +3.0 volts ON, depending on the amplifier, and 0 volts when OFF). Hook
oscilloscope probe to +Vcc pin on amplifier to monitor Vcc rising / falling edge.
3. Channel 2 of oscilloscope monitors rectified RF output of Amplifier
4. To make measurement of turn-on time, leave DC power supply on, disconnect and
“ground” +Vcc line to discharge amplifier, then insert Vcc line back into power supply.
This method will eliminate turn on time transient of power supply itself. Set up trigger of
O‟Scope to trigger on rising edge of Ch.1
5. To make measurement of turn-off time, with supply ON, reset o‟scope, setup trigger
to trigger on falling edge of Ch. 1, and simply remove +Vcc line / wire from the power
supply input to turn amplifier OFF.
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BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
a) Turn On Time:
Refer to oscilloscope screen-shot below. Upper trace (yellow, Channel 1) is DC power supply turn-on
step waveform whereas lower trace (green, Channel 2) is rectified RF output signal of the LNA stage.
Amplifier turn-on time is aproximately 1.5 milliseconds, or 1500 microseconds. Main source of
time delay in the LNA turn-on and turn-off events are the R-C time constants formed by (R2 + R3) x C4
and R3 x C5. Additional Charge Storage (e.g. relatively large values of C3 and C5) help to reduce
Third-Order distortion levels but increase turn-on / turn-off times of the amplifier. (Please refer to
Schematic diagram on page 6).
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BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
b) Turn-Off Time:
Rectified RF output signal (lower green trace) takes approximately ~ 30 microseconds to settle out
after power supply is turned off.
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BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
14
References
[1]. “A High IIP3 Low Noise Amplifier for 1900 MHz Applications Using the SiGe BFP620 Transistor”.
Applied Microwave and Wireless, July 2000. The article explains how additional charge-storage
(capacitance) placed across base-emitter and collector-emitter junctions can reduce the levels of thirdorder products generated during a two-tone intermodulation test; refer to the section entitled “Effect of
adding additional charge storage across the base-emitter junction” on pages 3 and 4.
[2]. BFP640F Datasheet, Infineon Technologies AG.
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BFP640F High Linearity 1575 MHz GPS LNA with 18 dB Gain, > +5 dBm IIP3
w w w . i n f i n e o n . c o m
AN179
Published by Infineon Technologies AG
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