AK2401 Datasheet, PDF (59/103 Pages) Asahi Kasei Microsystems – Direct Conversion Transceiver

[AK2401]
13.8.7. RDOC Function
The AK2401 has a real-time DC offset cancellation (RDOC) function that follows real-time DC offset
fluctuation and executes DC offset cancellation consistently. RDOC is enabled by setting RDOC bit = “1”
<Address0x26>. RDOC is effective for receiving a signal without amplitude fluctuation such as FM and
FSK.
■ RDOC Setting
Following registers are RDOC operation registers. These registers excluding RDOC_7[1:0],
RDOC_8[1:0] bits must be in the default setting. RDOC_7[1:0], RDOC_8[1:0] bits must be set to “11”
Register
RDOC_1
RDOC_2
RDOC_3
RDOC_4
RDOC_5
RDOC_6
RDOC_7
RDOC_8
RDOC_9
RDOC_10
RDOC_11
RDOC_12
RDOC_13
RDOC_14
RDOC_15
RDOC_16
RDOC_17
Address
0x26 D7
0x26 D6
0x26 D4-D3
0x26 D2-D1
0x27 D6-D4
0x27 D3-D2
0x27 D1-D0
0x28 D6-D5
0x28 D1-D0
0x44 D6-D5
0x44 D4-D3
0x44 D2-D0
0x45 D7-D0
0x46 D7-D6
0x46 D5-D4
0x46 D3-D2
0x46 D1-D0
Initial Value
“0”
“1”
“10”
“01”
“010”
“00”
“01”
“00”
“00”
“00”
“00”
“101”
“00000001”
“11”
“00”
“00”
“00”
Recommended
“0”
“1”
“10”
“01”
“010”
“00”
“11”
“11”
“00”
“00”
“00”
“101”
“00000001”
“11”
“00”
“00”
“00”
■ Local frequency offset (OFST2) control function
Set <Address0x28>RDOC_FM bit = ”1” when receiving non-modulated signal (CW) such as an FM radio.
It is automatically controlled so that frequency offset is added to the local signal. It is recommended to set
the frequency offset (OFST2 bits) to become 150Hz after divided by the local divider. It is necessary to
enable OFST2 during receiving, and the polarity of TX_PDN pin is related to the condition that enables
OFST2. Refer to 13.7.3 Frequency Offset Adjustment.
The operation status of this function can be output from LD pin or R_RDOC bit, but it is not normally used.
Here, the operation status output from the LD pin is output only when <Address 0×0C>LD bit = "1", and in
that case the lock detection output is not output.
This function can be OFF by setting RDOC_FM bit = “0” and OFST2 bits = all “0” if not receiving a
non-modulated signal (CW) such as a digital FSK radio.
017003093-E-00
59
2017/3