A BPF circuit designed as an example is shown below.
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Example of LPF circuit with 4 MHz cutoff (for reference) |
](64082.gif) |
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Frequency characteristic (reference value)
Freq[MHz] Gain[dB]
-------------------
0 -3
1 -4
2 -5
3 -5
fsc -4
4 -3
5 -8
10 -40
15 -50
20 -48
25 -48 |
R1=470Ω
R2=470Ω
R3=1kΩ
C1=150pF
C2= 10pF
C3=150pF
C4=0.01uF
L1=15uH
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Reduce the harmonic components as much as possible while
making sure to secure sufficient amplitude at fsc ±1 kHz.
Be particularly careful to sufficiently reduce the harmonic
components of 20MHz, which is the X'tal oscillation frequency.
The operation of this circuit has been verified using NECEL boards,
but the required characteristics of fscBPF depend to a large extent
on the board pattern.
Therefore, customers should use this circuit based on careful
verification that no image-related problems occur under various
input signal conditions.