AK2401 Datasheet, PDF (46/103 Pages) Asahi Kasei Microsystems – Direct Conversion Transceiver

[AK2401]
It is recommended to use a FIR filter that can change coefficients freely when using a reference clock with
a frequency except 19.2MHz and 18.432MHz since the cut-off frequency varies.
* None of channel filters of the AK2401 have root-raised cosine characteristics. Therefore an external
root-raised cosine filter should be connected when demodulating the data. Insufficient attenuation
amount for ACS (Adjacent Channel Selectivity) should be compensated by a root-raised cosine filter if
using a F3 channel filter for a TETRA (Terrestrial Trunked Radio) system since the attenuation amount
of adjoining channels is only 50dB.
Table 3. Standard Channel Filter Frequency Characteristics
Filter Name
DFIL_
PROG
DFIL_SEL
[3:0](hex)
Pass
Band
[kHz]
Stop
Band
[kHz]
Pass
Band
Ripple
[kHz]
Recommended
Applications
F0
0
0
60
74
±0.7
TETRA
150kHz channel
F1
0
1
39
53
±0.5
TETRA
100kHz channel
F2
0
2
19.2 25.2
±0.2
TETRA
50kHz channel
F3
0
3
11
16.3
±0.1
TETRA
25kHz channel
F4
0
4
10
14
±0.2
Wide
25kHz channel (D)
F5
0
5
7.5 11.5
±0.2
Wide
25kHz channel (E)
F6
0
6
6
10
±0.2
Wide
25kHz channel (F)
F7
0
7
4.5
8.5
±0.2
Narrow
12.5kHz channel (G)
F8
0
8
3
7
±0.2
Narrow
12.5kHz channel (H)
F9
0
9~F
2
4
±0.2
Very Narrow
6.25kHz channel (J)
Programmable
FIR Filter
1
X
-
-
-
-
(X: Do not care)
RXLPF_FC
Recommended
Setting
1
1
1
1
0
0
0
0
0
0
-
20
0
-20
-40
-60
-80
-100
-120
-140
0
BPF F0 (Pass Band=60kHz)
TCXO=19.2MHz
TCXO=18.432MHz
50
100
150
200
250
300
Frequency [kHz]
20
0
-20
-40
-60
-80
-100
-120
-140
0
BPF F1 (Pass Band=39kHz)
TCXO=19.2MHz
TCXO=18.432MHz
50
100
150
200
250
300
Frequency [kHz]
017003093-E-00
46
2017/3