8-7
RF2870
Rev A8 030507
Application Schematic
Differential IF SAW Filter Topology
NOTES:
Differential IF tuning components are dependent on IF frequency board layout and board parasitics. Please consult
RFMD applications engineering for tuning assistance.
If any functional blocks are not being used, the unused pins can be left with no connection.
IF output matching component values are dependent on board layout, IF SAW filter and the IF frequency selected.
Please contact RFMD application engineering for assistance with IF output matching.
1. This resistor sets the mixer preamp and mixer currents. Lowering the resistance results in higher currents.
2. Sets internal bias voltage. Recommend 4.3k
Ω.
3. DC-blocking capacitor.
4. Determines trade-off between IIP3 and gain. Higher value inductor means lower gain and higher IIP3.
5. Cell LNA input matching for optimum IIP3. Low impedance path to ground at low frequency for optimum IIP3.
6. Mixer input matching.
7. For output matching and a DC supply bias choke.
8. Input or output matching.
9. Coupling of coils on the input, output and emitter of the LNA should be minimized to reduce the risk of oscillation. We
recommend separating the inductors and/or positioning them 90° relative to each other.
Layout Note:
To minimize losses and radiation, the RF signal traces should be as short as possible. The IF+ and IF- output traces
should be symmetrical. All bypass capacitors and matching capacitors must have a ground via very close to the capaci-
tor. Each capacitor should have its own ground via. All traces should be 50
Ω transmission lines. Position inductors to
reduce coupling. (See note 9.)
16
15
14
13
11
12
9
10
5
6
7
8
2
1
4
3
0.1
µF
4.3 k
Ω
6.8 k
Ω
3.0 pF
10 nH
100 pF
1.2 nH
33 nH
33 nF
LNA GAIN
ENABLE
TX BUF EN
3.9 nH
FL4
RF Saw
4
1
6
3
GND
GND
GND
GND
33 nF
2870310, Rev. 1
MIX GAIN
CELL LNA IN
2.2 nH
LO OUT
LO IN
1.2 pF
V
CC
V
CC
C1
R1
L1
L1
V
CC
C3
C2
C2
CDMA IF+
CDMA IF-
L2
IF Saw
4
5
9
10
Note 6
Note 3
Note 1
Note 2
Note 8
Note 8
Notes 7, 9
Notes 4, 9
Note 3
Notes 5, 9
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