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AN RFMD® APPLICATION NOTE
SGA-8343 GPS Application Circuits
RFMD Worldwide Applications
Design Application Note -- AN-061
Abstract
RFMD’s SGA-8343 is a high performance SiGe amplifier designed for operation from DC to 6GHz. This application note illustrates application circuits for GPS (Global Positioning System) frequency band (1575MHz). The first application circuit is optimized for noise performance; the second one is optimized for input return loss. Introduction The application circuits were
designed to achieve the optimum combination of NF, input return loss, and stability. All recommended components are standard values available from well-known manufacturers. Components specified in the bill of materials (BOM) have known parasitics which in some cases are critical to the circuit’s performance. Deviating from the recommended BOM may result in a
performance shift due to varying parasitics. Matching component placement is critical to each circuit’s performance.
Circuit Details
SMDI will provide the detailed layout (AutoCAD format) to users wishing to use the exact same layout and PCB material shown
in the following circuits. The circuits recommended within this application note were designed using the following PCB stack
up:
Material: GETEKTM ML 200C
Core thickness: 0.031”
Copper cladding: 1 oz. both sides
Dielectric constant: 4.1
Dielectric loss tangent: 0.0089 (at 1GHz)
Customers not wishing to use the exact material and layouts shown in this application note can design their own PCB using the
critical transmission line impedances and phase lengths shown in the BOMs and layouts.
NOTE: Many of our sample evaluation boards may come with an additional substrate and copper layer for mechanical stability.
It has been assumed that the backside layer has no effect on the RF performance or circuit design.
RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc.
091113
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support, contact RFMD at (+1) 336-678-5570 or [email protected]
1 of 7
SGA-8343 GPS Application Circuits
Design Considerations and Trade-Offs - Biasing Techniques
All HBT amplifiers are subject to device current variation due to the decreasing nature of the internal VBE with increasing temperature. In the absence of an active bias circuit or resistive feedback, the decreasing VBE will result in increased base and
collector currents. As the collector current continues to increase under constant VCE conditions, the device may eventually
exceed its maximum dissipated power limit resulting in permanent device damage. The designs included in this application
note contain passive bias circuits that stabilize the device current over temperature and desensitize the circuit to device process variation. The passive bias circuits used in these designs include a dropping resistor in the collector bias line and a voltage divider from the collector-to-base. Using this scheme, the amplifier can be biased from a single supply voltage. The
collector dropping resistor is sized to drop >20% VCE, depending on the desired VCE. The voltage divider from collector-to-base,
in conjunction with the dropping resistor, will stabilize the device current over temperature. The effectiveness increases with
increasing voltage drop in collector bias line. Configuring the voltage divider such that the shunt current is 5-10 times larger
than the desired base current desensitizes the circuit to beta variation. These two feedback mechanisms are sufficient to
insure consistent performance over temperature and device process variations. Note that the voltage drop is clearly dependent on the nominal collector current and can be adjusted to generate the desired VCE from a fixed supply rail. The user should
test the circuit over the operational extremes to guarantee adequate performance. An active bias circuit can be implemented if
the user does not wish to sacrifice the voltage required by the aforementioned passive circuit. There are various active bias
schemes suitable for HBTs. The user should choose an active bias circuit that best meets his/her cost, complexity, and performance requirements.
Other Application Circuits Available (see AN-044)
1.
2.
3.
800MHz to 1000MHz, single-ended with series feedback, optimized for NF and S11<-10dB.
1800MHz to 2000MHz, single ended, optimized for NF and S11<-8dB.
2400MHz to 2500MHz, single-ended, optimized for NF and S11<-10dB.
Vcc
+
V DROP
Ic
IB
+
V CE
I SHUNT
-
Figure 1. Passive Bias Circuit Topology
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7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
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SGA-8343 GPS Application Circuits
Vs
R4
6
Q1a
2
1
C4
R3
R2
R1
R5
5
3
R6
4
Q1b
C3
C5
C6
L2
L1
SGA-8343
Figure 2. Active Bias Circuit Topology
SGA-8343(Z)-EVB4 1575MHz Application Schematic
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7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
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SGA-8343 GPS Application Circuits
SGA-8343(Z)-EVB4 1575MHz Evaluation Board
091113
Ref. Des
Part Number
C1, 5, 7
ROHM MCH185A150J
Value
15pF
C2
ROHM MCH185A1R2C
1.2pF
C3, 4, 6
Samsung CL 10B104KONC
0.1uF
L1
TOKO LL 1608-FS39NJ
39nH
L2
TOKO LL 1608-FS1N8S
1.8nH
L3
TOKO LL 1608-FS3N9S
3.9nH
R1, 3
ROHM MCR03J222
2.2K
R2
ROHM MCR03J102
1.0K
R4
ROHM MCR03J620
62
R5
ROHM MCR03J100
10
Z1
non-critical
50
Z2
6.5 degrees at 1575MHz
50
Z3
7.8 degrees at 1575MHz
50
Z4
6.4 degrees at 1575MHz
50
Z5
6.4 degrees at 1575MHz
50
Z6
non-critical
50
Z7
11.1 degrees at 1575MHz
50
Z8
6.3 degrees at 1575MHz
50
Z9
26.0 degrees at 1575MHz
60
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
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SGA-8343 GPS Application Circuits
Typical Performance: Optimal S11 Application Circuit (V
S =3.3V, I CQ =10mA, 25C)
Gain vs. Frequency
NF vs. Frequency
2
18
1.8
16
1.6
dB
dB
20
14
1.4
12
1.2
1
10
1.5
1.52
1.54
1.56
1.58
1.5
1.6
1.52
1.54
1.56
P1dB vs. Frequency
1.6
1.58
1.6
OIP3 vs. Frequency
30
10
8
28
6
26
dBm
dBm
1.58
GHz
GHz
4
2
24
22
0
1.5
1.52
1.54
1.56
1.58
20
1.6
1.5
1.52
1.54
GHz
S11 vs. Frequency
1.56
GHz
S22 vs. Frequency
0
0
-5
-5
dB
dB
-10
-10
-15
-15
-20
-20
-25
1
1.2
1.4
1.6
1.8
1
2
1.2
1.4
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1.6
1.8
2
GHz
GHz
Freq (GHz)
P1dB (dBm)
OIP3 (dBm)
Gain (dB)
S11 (dB)
S22 (dB)
1.550
6.2
26.5
17.4
-17
-13
1.6
1.575
6.5
27.0
17.3
-20
-12
1.6
1.600
6.6
27.8
17.1
-21
-12
1.6
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
NF (dB)
5 of 7
SGA-8343 GPS Application Circuits
Optimal S11 Appl ication Circuit (V
S =3.3V, V CE
=2.7V, I CQ =10mA)
GND
Vs=+3.3V
(10mA)
62
2.2K
1K
0.1uF
10
1.3K
0.1uF
15pF
39nH
0.1uF
15pF
3.9nH
1.8nH
2.2pF
15pF
ECB-101766-B
SOT-343 - FB
Ref. Des.
Part Number
Value
Ref. Des.
Part Number
Value
C1, 5, 7
ROHM MCH185A150J
15 pF
Z1
C2
ROHM MCH185A2R2C
2.2 pF
Z2
4.6 degrees @ 1575 MHz
50
Z3
3.9 degrees @ 1575 MHz
50
C3, 4, 6
Samsung CL10B104KONC
0.1uF
non-critical
50
L1
TOKO LL1608-FS39NJ
39 nH
Z4
7.1 degrees @ 1575 MHz
50
L2
TOKO LL1608-FS1N8S
1.8 nH
Z5
6.4 degrees @ 1575 MHz
50
L3
TOKO LL1608-FS3N9S
3.9 nH
Z6
6.4 degrees @ 1575 MHz
50
R1
ROHM MCR03J132
1.3K
Z7
R2
ROHM MCR03J102
1.0K
Z8
R3
ROHM MCR03J222
2.2K
Z9
6.3 degrees @ 1575 MHz
50
R4
ROHM MCR03J620
62
Z10
26.0 degrees @ 1575 MHz
60
R5
ROHM MCR03J100
10
non-critical
3.2 degrees @ 1575 MHz
50
50
Optimal S11 Schematic
R4
R3
Vs=3.3V
C4
R2
R5
C5
Z10
C3
L2
C1
Z1
Z2
Z3
R1
L3
C6
C7
L1
Z4
Z5
SGA-8343
Z6
Z7
C2
pin 4 - Pad edge to via center
pin 2 - Pad edge
to grounding strip
Z9
Z8
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7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
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SGA-8343 GPS Application Circuits
Typical Performance: Optimal NF Application Circuit (V
S =3.3V, I CQ =10mA, 25C)
Gain vs. Frequency
NF vs. Frequency
2
18
1.8
16
1.6
dB
dBm
20
14
12
1.4
1.2
10
1
1.5
1.52
1.54
1.56
1.58
1.6
1.5
1.52
1.54
GHz
P1dB vs. Frequency
1.58
1.6
1.58
1.6
OIP3 vs. Frequency
30
8
28
6
26
dBm
10
dBm
1.56
GHz
4
2
24
22
0
20
1.5
1.52
1.54
1.56
1.58
1.6
1.5
1.52
1.54
1.56
GHz
GHz
S22 vs. Frequency
S11 vs. Frequency
0
0
-5
-10
dB
dB
-5
-10
-15
-20
-15
-25
-30
-20
1
1.2
1.4
1.6
1.8
1
2
1.2
1.4
1.8
2
GHz
GHz
091113
1.6
Freq (GHz)
P1dB (dBm)
OIP3 (dBm)
1.550
6.7
26.3
Gain (dB)
15.8
S11 (dB)
-10
S22 (dB)
-26
1.22
1.575
6.8
26.5
15.7
-11
-28
1.22
1.600
6.8
26.8
15.6
-11
-29
1.25
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support, contact RFMD at (+1) 336-678-5570 or [email protected]
NF (dB)
7 of 7
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