ASAHI KASEI
[AK4644]
[Filter Coefficient Setting]
1) When FIL1 and FIL2 are set to “HPF”
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
K: Filter gain [dB] (Filter gain of should be set to 0dB.)
Register setting
FIL1: F1AS bit = “0”, F1A[13:0] bits =A, F1B[13:0] bits =B
FIL3: F3AS bit = “0”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F1A13, F1B13, F3A13, F3B13; LSB=F1A0, F1B0, F3A0, F3B0)
1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
A = 10K/20 x
,
B =
1 + 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
Transfer function
Amplitude
2 − 2cos (2πf/fs)
1 + B2 + 2Bcos (2πf/fs)
Phase
1 − z −1
H(z) = A
(B+1)sin (2πf/fs)
θ(f) = tan −1
M(f) = A
1 + Bz −1
1 - B + (B−1)cos (2πf/fs)
2) When FIL1 and FIL2 are set to “LPF”
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
K: Filter gain [dB] (Filter gain of FIL1 should be set to 0dB.)
Register setting
FIL1: F1AS bit = “1”, F1A[13:0] bits =A, F1B[13:0] bits =B
FIL3: F3AS bit = “1”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F1A13, F1B13, F3A13, F3B13; LSB=F1A0, F1B0, F3A0, F3B0)
1
1 − 1 / tan (πfc/fs)
A = 10K/20
x
,
B =
1 + 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
Transfer function
Amplitude
2 + 2cos (2πf/fs)
Phase
1 + z −1
H(z) = A
(B−1)sin (2πf/fs)
θ(f) = tan −1
M(f) = A
1 + Bz −1
1 + B2 + 2Bcos (2πf/fs)
1 + B + (B+1)cos (2πf/fs)
MS0477-E-01
2006/10
- 40 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
