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10-20
RF2617
Rev B4 010717
10
Application Schematic
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NC
GAIN
CONTROL
IN
SEL.
10 nF
CDMA-
FM IN
CDMA+
IF IN
SELECT
4.7 k
Ω
GC
10 nF
L1
L1
V
CC
OUT+
OUT-
V
CC
R2
500
Ω
C1
C2
Measurement
Reference Plane
Z
LOAD=500 Ω
Z
S=500 Ω
Z
IN, EFF=500 Ω
Z
IN=1 kΩ
Z
S=850 Ω
Z
S, EFF=333 Ω
Z
IN=850 Ω
Measurement
Reference Plane
Z
LOAD,EFF=250 Ω
Z
OUT=500 Ω
R1 sets the CDMA balanced input impedance. The effective input impedance is then 500
Ω.
R2 sets the balanced output impedance to 500
Ω. L1 and C2 serve dual purposes. L1 serves
as an output bias choke, and C2 serves as a series DC block. In addition, the values of L1
and C2 may be chosen to form an impedance matching network of the load impedance is not
500
Ω. Otherwise, the values of L1 and C1 are chosen to form a parallel-resonant tank circuit
at the IF when the load impedance is 500
Ω.
10 nF
10 nF
FM IF Filter
CDMA IF Filter
R1
1k
Ω
C2
C1
C2
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