AN131 - A Low Cost Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the SiGe BFP640

A pp li c at io n N o t e, R e v . 1. 2 , N ov e m be r 2 00 7
A p p li c a t i o n N o t e N o . 1 3 1
A Lo w C o s t , T w o S ta g e L N A f o r 5 t o 6 G H z
" 8 0 2 . 1 1a " A pp l i c a t i o n s u s i n g t h e S i G e B F P 6 4 0
R F & P r o t e c ti o n D e v i c e s
Edition 2007-11-27
Published by
Infineon Technologies AG
81726 München, Germany
© Infineon Technologies AG 2009.
All Rights Reserved.
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Application Note No. 131
Application Note No. 131
Revision History: 2007-11-27, Rev. 1.2
Previous Version: 2002-11-16, Rev. 1.1
Page
Subjects (major changes since last revision)
All
Small changes in figure descriptions
Application Note
3
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
1
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications
using the SiGe BFP640
Overview
•
•
•
•
•
The Silicon-Germanium BFP640 is evaluated on a PCB to show the feasibility of a very low-cost, discrete TwoStage LNA design in the 5 - 6 GHz range.
The Printed Circuit Board Used is PCB 640-052402 Revision A. Standard FR4 material is used. Note that the
PCB allows for the tune / test of each stage separately, prior to integrating the two stages. This is achieved
with a third SMA RF connector positioned between the two stages.
Low-cost, standard SMT passive components are used
Total PCB area used for both stages is approximately 100 mm². Note that further reduction in PCB area is
possible.
Achieved > 20 dB gain, 1.4 dB Noise Figure at 5450 MHz, on 3.3 V supply, drawing 15.9 mA. Note noise figure
result does NOT "back out" FR4 PCB losses - if the PCB loss at LNA input were extracted, Noise Figure
Results would be approximately 0.3 dB lower.
PCB Cross - Section Diagram
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Figure 1
PCB - Cross Sectional Diagram
Application Note
4
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Summary of Data for Two-Stage Cascade
T = 25 °C, network analyzer source power = -35 dBm
Table 1
Summary of Data for Two-Stage Cascade
Parameter
Result
Comments
Frequency Range
5 - 6 GHz
Various portions of this range are usable on a
worldwide basis for 802.11b, HiperLAN
DC Current
15.9 mA
Low current consumption
DC Voltage, VCC
3.3 V
Collector-Emitter Voltage, VCE ≅ 2.9 V, each stage
BFP640 BVCEO of 4.0 V would permit higher
voltage operation. Higher bias voltage would
improve linearity and slightly increase gain
Gain
22.7 dB @ 5150 MHz
22.4 dB @ 5250 MHz
22.1 dB @ 5350 MHz
21.6 dB @ 5470 MHz
20.2 dB @ 5825 MHz
Cascade Noise Figure
1.4 dB @ 5150 MHz
1.4 dB @ 5250 MHz
1.4 dB @ 5350 MHz
1.4 dB @ 5470 MHz
1.5 dB @ 5825 MHz
Input P1dB
-14.7 dBm @ 5350 MHz
See input power sweep vs. gain plot, Figure 6.
Input 3 Order Intercept
+4.6 dBm @ 5350 MHz
Please see plots Figure 13 & Figure 14
Input Return Loss
12.2 dB @ 5150 MHz
13.3 dB @ 5250 MHz
14.5 dB @ 5350 MHz
16.0 dB @ 5470 MHz
19.9 dB @ 5825 MHz
Good broadband input match
Output Return Loss
9.7 dB @ 5150 MHz
10.5 dB @ 5250 MHz
12.2 dB @ 5350 MHz
13.8 dB @ 5470 MHz
19.9 dB @ 5825 MHz
Good broadband output match
Reverse Isolation
34.9 dB @ 5150 MHz
34.0 dB @ 5250 MHz
34.5 dB @ 5350 MHz
34.7 dB @ 5470 MHz
33.7 dB @ 5825 MHz
rd
Application Note
5
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Bill of Material
Table 2
Bill of Material, Complete Two-Stage Cascade
Reference
Designator
Value
Manufacturer
Case Size
Function
C1, C2, C7
1.5 pF
Various
0402
DC blocking
C4. C5, C9,
C10
1.5 pF
Various
0402
RF bypass / RF block
C3, C6, C8,
C11
0.033 µF
Various
0402
Low frequency ground at base (input ThirdOrder Intercept improvement), low
frequency decoupling / blocking
L1, L4
6.2 nH
Murata LQP15M tight
tolerance inductor
(former Murata part
number = LQP10A)
0402
RF choke to DC bias on base of Q1 and Q2
L2, L5
5.6 nH
Murata LQP15M tight
tolerance inductor
0402
RF choke to collector of Q1 and Q2; also
influences output match of each stage
L3
1.3 nH
Murata LQP15M tight
tolerance inductor
0402
Output matching, stage 1
L6
1.5 nH
Murata LQP15M tight
tolerance inductor
0402
Output matching, stage 2
R1, R4
10 Ω
Various
0402
For stability, output matching
R2, r5
43 kΩ
Various
0402
DC bias for base of Q1 and Q2
R3, R6
30 Ω
Various
0402
Drop supply voltage by approx. 0.3 V,
provide DC feedback for bias
compensation (beta variation, temperature,
etc.)
Q1, Q2
-
Infineon Technologies
SOT-343
BFP640F SiGe Transistor, fT = 36 GHz
J1, J2, J3
-
Johnson 142-0701-841
-
RF input / output connectors (J2 only used
when testing stages individually)
J4
-
AMP 5 pin header MTA100 series 640456-5
(standard pin plating) or
641215-5 (gold plated
pins)
-
DC connector
Application Note
Pins 1, 5 = ground
Pin 3 = VCC
Pins 2, 4 = no connection
6
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Schematic Diagram, Two-Stage Cascade
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Figure 2
Schematic Diagram
Application Note
7
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Noise Figure, Plot, Two-Stage Cascade, Center of Plot (x-axis) is 5500 MHz.
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Figure 3
Noise Figure
Application Note
8
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Noise Figure, Tabular Data, Two-Stage
From Rohde & Schwarz SFEK3 + FSEB30
System Preamplifier = MITEQ AFS3-04000800-10-ULN
Table 3
Noise Figure
Frequency
Noise Figure
5000 MHz
1.32 dB
5025 MHz
1.34 dB
5050 MHz
1.35 dB
5075 MHz
1.34 dB
5100 MHz
1.36 dB
5125 MHz
1.36 dB
5150 MHz
1.36 dB
5175 MHz
1.37 dB
5200 MHz
1.37 dB
5225 MHz
1.35 dB
5250 MHz
1.38 dB
5275 MHz
1.39 dB
5300 MHz
1.37 dB
5325 MHz
1.37 dB
5350 MHz
1.39 dB
5375 MHz
1.40 dB
5400 MHz
1.39 dB
5425 MHz
1.44 dB
5450 MHz
1.44 dB
5475 MHz
1.41 dB
5500 MHz
1.45 dB
5525 MHz
1.46 dB
5550 MHz
1.47 dB
5575 MHz
1.48 dB
5600 MHz
1.50 dB
5625 MHz
1.49 dB
5650 MHz
1.52 dB
5675 MHz
1.53 dB
5700 MHz
1.51 dB
5725 MHz
1.54 dB
5750 MHz
0.56 dB
5775 MHz
1.55 dB
5800 MHz
1.54 dB
5825 MHz
1.53 dB
5850 MHz
1.55 dB
5875 MHz
1.55 dB
5900 MHz
1.57 dB
Application Note
9
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Table 3
Noise Figure (cont’d)
Frequency
Noise Figure
5925 MHz
1.56 dB
5950 MHz
1.55 dB
5975 MHz
1.56 dB
6000 MHz
1.54 dB
Application Note
10
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Scanned Image of PC Board, Two-Stage Cascade
By swinging a capacitor tacked to the output of Stage 1 down or to the right, the individual stages may be tested
alone prior to integration. To test Stage 1 by itself, signal flow is from leftmost RF connector (input) to bottom RF
connector [output]; to test Stage 2 alone, signal flow is from bottom RF connector [input] to rightmost RF connector
[output]. The DC block between stages, C2, can be swung from output of Stage 1 down to lower RF connector to
test Stage 1 alone; likewise C2 can be swung from track leading to lower RF connector up to right at a 45 degree
angle to connect to input of Stage 2, to test Stage 2 alone.
Figure 4
Image of PC Board
Application Note
11
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Scanned Image of PC Board, Two-Stage Cascade, Close-In Shot
Figure 5
Image of PC Board, Close-In Shot
Application Note
12
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Power Sweep at 5350 MHz (CW)
Source Power (Input) swept from -25 to 0 dBm
Input P1dB ≅ -15.7 dBm
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Figure 6
Plot of Power Sweep at 5350 MHz
Application Note
13
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Input Return Loss, Log Mag
Cascade, 2 Stages
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Figure 7
Plot of Input Return Loss
Application Note
14
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Input Return Loss, Smith Chart
Cascade, 2 Stages
Reference Plane = PCB Input SMA Connector
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Figure 8
Smith Chart of Input Return Loss
Application Note
15
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Forward Gain
Cascade, 2 Stages
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Figure 9
Plot of Forward Gain
Application Note
16
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Reverse Isolation
Cascade, 2 Stages
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Figure 10
Plot of Reverse Isolation
Application Note
17
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Output Return Loss, Log Mag
Cascade, 2 Stages
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Figure 11
Plot of Output Return Loss
Application Note
18
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Output Return Loss, Smith Chart
Cascade, 2 Stages
Reference Plane = PCB Output SMA Connector
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Figure 12
Smith Chart of Output Return Loss
Application Note
19
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Two-Tone Third Order Intercept Test, 5350 MHz
Input Stimulus for Two-Tone Third Order Intercept Test.
f1 = 5349 MHz, f2 = 5350 MHz, -23 dBm each tone.
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Figure 13
Tow-Tone Test, Input Stimulus @ 5350 MHz
Application Note
20
Rev. 1.2, 2007-11-27
Application Note No. 131
A Low Cost, Two Stage LNA for 5 to 6 GHz "802.11a" Applications using the
Two-Tone Third Order Intercept Test, 5350 MHz
LNA Output Response to Two-Tone Test.
Input 3rd Order Intercept = -23 + (55.2 / 2) = +4.6 dBm
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Figure 14
Tow-Tone Test, LNA Response @ 5350 MHz
Application Note
21
Rev. 1.2, 2007-11-27
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