參數(shù)資料
型號: AK4671
廠商: Asahi Kasei Microsystems Co.,Ltd
元件分類: Codec
英文描述: Stereo CODEC with MIC/RCV/HP-AMP
中文描述: 立體聲編解碼器麥克風(fēng)/垃圾車/惠普腺苷
文件頁數(shù): 63/164頁
文件大?。?/td> 1792K
代理商: AK4671
[AK4671]
MS0666-E-00
2007/10
- 63 -
Digital Programmable Filter
(1)
High Pass Filter (HPF)
Normally, this HPF is used for a Wind-Noise Reduction Filter. This is composed of 2 steps of 1st order HPF. The
coefficient of both HPF is the same and set by F1A13-0 bits and F1B13-0 bits. HPFAD bit controls ON/OFF of the 1st
step HPF and HPF bit controls ON/OFF of the 2nd step HPF. When the HPF is OFF, the audio data passes this block by
0dB gain. The coefficient should be set when HPFAD=HPF bits = “0” or PMADL=PMADR=PMDAL=PMDAR bits =
“0”.
fs: Sampling frequency
fc: Cut-off frequency
Register setting (
Note 61
)
HPF: F1A[13:0] bits =A, F1B[13:0] bits =B
(MSB=F1A13, F1B13; LSB=F1A0, F1B0)
A =
1 + 1 / tan (
π
fc/fs)
1 + 1 / tan (
π
fc/fs)
1 / tan (
π
fc/fs)
B =
1
1 / tan (
π
fc/fs)
,
Transfer function
H(z) = A
1
z
1
1 + Bz
1
The cut-off frequency should be set as below.
fc/fs
0.0001 (fc min = 4.41Hz at 44.1kHz)
(2)
Low Pass Filter (LPF)
This is composed with 1st order LPF. F2A13-0 bits and F2B13-0 bits set the coefficient of LPF. LPF bit controls ON/OFF
of the LPF. When the LPF is OFF, the audio data passes this block by 0dB gain. The coefficient should be set when LPF
bit = “0” or PMADL=PMADR=PMDAL=PMDAR bits = “0”.
fs: Sampling frequency
fc: Cut-off frequency
Register setting (
Note 61
)
LPF: F2A[13:0] bits =A, F2B[13:0] bits =B
(MSB=F2A13, F1B13; LSB=F2A0, F2B0)
1
B =
1 + 1 / tan (
π
fc/fs)
A =
1 + 1 / tan (
π
fc/fs)
1
1 / tan (
π
fc/fs)
,
Transfer function
H(z) = A
1 + z
1
1 + Bz
1
The cut-off frequency should be set as below.
fc/fs
0.05 (fc min = 2205Hz at 44.1kHz)
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