AN138

A pp li c at i on N ot e , R ev . 1 . 2 , J an ua ry 2 00 8
A p p li c a t i o n N o t e N o . 1 3 8
D u a l - B a n d ( L 1 + L 2) G P S Lo w N o i s e A m p l i f i e r
u s i n g th e S i G e B F P 64 0 H B T R F T r an s i s t o r
R F & P r o t e c ti o n D e v i c e s
Edition 2008-01-10
Published by
Infineon Technologies AG
81726 München, Germany
© Infineon Technologies AG 2009.
All Rights Reserved.
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Application Note No. 138
Application Note No. 138
Revision History: 2008-01-10, Rev. 1.2
Previous Version: 2005-08-09, Rev. 1.1
Page
Subjects (major changes since last revision)
All
Small changes in figure descriptions
Application Note
3
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
1
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe
BFP640 HBT RF Transistor
Applications
•
GPS Low Noise Amplifiers (LNAs) for 3 V systems, where reception of both L1 (1575.42 MHz) and L2
(1227.6 MHz) GPS signals is required.
Overview
The Infineon BFP640 SiGe Heterojunction Bipolar Transistor in SOT343 package is shown in a low-cost LNA
circuit suitable for dual band GPS applications operating from a 3 V power supply. PC board is fabricated from
standard, low-cost, commercial grade glass-epoxy material ("FR4"). 0402 case-size passive components are
used.
Target Specifications
Gain @ 1227.6 MHz => >18 dB; Gain @ 1575.42 MHz => > 17 dB; OP1dB > +3 dBm; Noise Figure (NF) < 3 dB;
VCC = 3.0 Volts, I < 15 mA.
Remarks
(T = 25 °C)
•
•
•
•
•
Amplifier is unconditionally stable from 5 MHz - 8 GHz (K>1). See plot on Page 7
19.9 dB gain at 1227.6 MHz, 18.5 dB gain at 1575.42 MHz
Noise Figure = 1.1 dB for both L1 and L2 frequencies1)
9.1 mA current consumption at 3.0 V
Output P1dB meets target at 1575 MHz, but is slightly low at 1227 MHz. OP1dB can be improved by increasing
current; do this by reducing value of resistor R2 (see Figure 2)
Summary of Results
Table 1
Summary of Results, T = 25 °C
Frequency
(MHz)
dB[s11]² dB[s21]² dB[s12]² dB[s22]² NF1)
dB
IIP3
OIP3
IP1dB
OP1dB
dBm
dBm
dBm
dBm
1227.6
11.3
19.9
27.6
18.9
1.1
---
---
-17.6
+1.3
1575.4
17.2
18.5
25.6
11.3
1.1
+5.7
+24.2
-14.4
+3.1
Cross Sectional Diagram of PC Board
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PCB - Cross Sectional Diagram
1) Note that PCB loss is not extracted. If PCB loss were extracted, NF would be 0.1 to 0.2 dB lower
Application Note
4
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Schematic Diagram
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Schematic Diagram
Application Note
5
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Noise Figure, Plot, 1100 MHz to 1700 MHz, Center of Plot (x-axis) is 1400 MHz.
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Figure 3
Noise Figure
Application Note
6
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Noise Figure, Tabular Data
From Rohde & Schwarz FSEK3 + FSEB30
System Preamplifier = MITEQ SMC-02
Table 2
Noise Figure
Frequency
Noise Figure
1100 MHz
1.13 dB
1125 MHz
1.13 dB
1150 MHz
1.14 dB
1175 MHz
1.11 dB
1200 MHz
1.12 dB
1225 MHz
1.12 dB
1250 MHz
1.12 dB
1275 MHz
1.11 dB
1300 MHz
1.11 dB
1325 MHz
1.11 dB
1350 MHz
1.10 dB
1375 MHz
1.11 dB
1400 MHz
1.09 dB
1425 MHz
1.10 dB
1450 MHz
1.09 dB
1475 MHz
1.08 dB
1500 MHz
1.07 dB
1525 MHz
1.09 dB
1550 MHz
1.09 dB
1575 MHz
1.07 dB
1600 MHz
1.08 dB
1625 MHz
1.08 dB
1650 MHz
1.08 dB
1675 MHz
1.10 dB
1700 MHz
1.11 dB
Application Note
7
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Scanned Image of PC Board
Figure 4
Image of PC Board
Application Note
8
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Scanned Image of PC Board, Close-In Shot.
Total PCB area used ≅ 50 mm²
Figure 5
Image of PC Board, Close-In Shot
Application Note
9
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Stability
Rohde and Schwarz ZVC Network Analyzer calculates and plots Stability Factor "K" in real time, from 5 MHz to
8 GHz. Note K>1 from 5 MHz to 8 GHz; minimum K value is approximately 1.1 at ≈ 6.6 GHz. Amplifier is
Unconditionally Stable over 5 MHz - 8 GHz frequency range.
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Figure 6
Plot of K(f)
Application Note
10
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Gain Compression at 1227 MHz and 1575 MHz
Amplifier is checked for output 1 dB compression point at VCC = 3 V, I = 9.1 mA (with VCE = 2.6 V). An Agilent
power meter was used to ensure accurate power levels are measured (as opposed to using Vector Network
Analyzer in "Power Sweep" mode).
1227 MHz:
Output P1dB ≅ + 1.3 dBm; Input P1dB = +1.3 dBm - (Gain - 1 dB) = +1.3 dBm - 18.9 dB = -17.6 dBm
1575 MHz:
Output P1dB ≅ + 3.1 dBm; Input P1dB = +3.1 dBm - (Gain - 1 dB) = +1.3 dBm - 17.5 dB = -14.4 dBm
Table 3
Gain Compression
POUT, dBm
Gain @ 1227 MHz, dB
Gain @ 1575 MHz, dB
-10.0
19.9
18.5
-9.0
19.9
18.5
-8.0
19.9
18.5
-7.0
19.8
18.5
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19.8
18.4
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19.8
18.4
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19.7
18.4
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19.7
18.4
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19.6
18.3
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19.5
18.3
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19.1
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18.6
17.9
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17.7
17.5
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16.3
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Figure 7
Plot of Gain Compression, Output Power in dB
Application Note
11
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Please Note - all plots are taken from Rohde and Schwarz ZVC Network Analyzer,
with T = 25 °C, source power ≈ -30 dBm
Input Return Loss, Log Mag
5 MHz - 8 GHz Sweep
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Plot of Input Return Loss
Application Note
12
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Input Return Loss, Smith Chart
Reference Plane = Input SMA Connector on PC Board
5 MHz - 8 GHz Sweep
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Smith Chart of Input Return Loss
Application Note
13
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Forward Gain
5 MHz - 8 GHz Sweep
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Plot of Forward Gain
Application Note
14
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Reverse Isolation
5 MHz - 8 GHz Sweep
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Plot of Reverse Isolation
Application Note
15
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Output Return Loss, Log Mag
5 MHz - 8 GHz Sweep
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Plot of Output Return Loss
Application Note
16
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Output Return Loss, Smith Chart
Reference Plane = Output SMA Connector on PC Board
5 MHz - 8 GHz Sweep
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Smith Chart of Output Return Loss
Application Note
17
Rev. 1.2, 2008-01-10
Application Note No. 138
Dual-Band (L1 + L2) GPS Low Noise Amplifier using the SiGe BFP640 HBT RF
Two-Tone Test, 1575 MHz
Input Stimulus for Amplifier Two-Tone Test.
f1 = 1575 MHz, f2 = 1576 MHz, -25 dBm each tone.
LNA response to two-tone test is below (spectrum analyzer screen-shot).
Input IP3 = -25 + (61.4 / 2) = +5.7 dBm. Output IP3 = +5.7 dBm + 18.5 dB gain = +24.2 dBm
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Figure 14
Tow-Tone Test, LNA Response @ 1575 MHz
Application Note
18
Rev. 1.2, 2008-01-10
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