
1
(2
f
Z
p
1
C)
C =
1
Z
(2
f
C
2
p
)
L =
1
Z
(2
f
C
1
p
)
L =
2
1
(2
f
Z
p
2
C)
C =
2
SBOS531D – AUGUST 2010 – REVISED MAY 2012
The following steps can be used to quickly design the passive passband filter. (Note that these steps produce an
approximate result.)
1. Choose the filter characteristic impedance, ZC:
–
For –6-db passband attenuation: R1 = R2 = ZC
–
For 0-db passband attenuation: R1 = ZC, R2 = 10 ● ZC
2. Calculate values for C1, C2, L1, and L2 using the following equations:
Table 4. Recommended Component Values for Fourth-Order Passive Bandpass Filter (0-db Passband
Attenuation)
FREQUENCY
CHARACTERISTIC
RANGE
IMPEDANCE
R1
R2
C1
C2
L1
L2
FREQUENCY BAND
(kHz)
(
Ω)
(
Ω)
(
Ω)
(nF)
(
μH)
(
μH)
CENELEC A
35 to 95
1k
10k
4.7
1.5
1500
4700
CENELEC B, C, D
95 to 150
1k
10k
1.7
1
1200
1500
SFSK
63 to 74
1k
10k
2.7
2.2
2200
Table 5. Recommended Component Values for Fourth-Order Passive Bandpass Filter (–6-db Passband
Attenuation)
FREQUENCY
CHARACTERISTIC
RANGE
IMPEDANCE
R1
R2
C1
C2
L1
L2
FREQUENCY BAND
(kHz)
(
Ω)
(
Ω)
(
Ω)
(nF)
(
μH)
(
μH)
CENELEC A
35 to 95
1k
4.7
1.5
1500
4700
CENELEC B, C, D
95 to 150
1k
1.7
1
1200
1500
SFSK
63 to 74
1k
2.7
2.2
2200
Copyright 2010–2012, Texas Instruments Incorporated
27
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