ax50424 AXSEM, ax50424 Datasheet - Page 24

• Manufacturer Part Number: ax50424
• Description: Advanced Multi-channel Single Chip Uhf Receiver
• Manufacturer: AXSEM

24
Circuit Description
5.11. RX AGC and RSSI
AX50424
5.12. Automatic Frequency Control (AFC)
The
frequency to a carrier signal. For AFC adjustment, the frequency offset can be computed
with the following formula:
FSKMUL is the FSK oversampling factor, it depends on the FSK bit rate and deviation used. To
determine it for a specific case, see the
other than FSK, FSKMUL=1.
Version 1.3
∆
f
1. RSSI before the digital IF channel filter.
2. RSSI behind the digital IF channel filter.
=
AX50424
TRKFREQ
The gain of the receiver is adjusted in order to keep the analog IF filter output level
inside the working range of the ADC and demodulator. The register
contains the current value of the AGC and can be used as an RSSI. The step size of
this RSSI is 0.625 dB. The value can be used as soon as the RF frequency generation
sub-system has been programmed.
The demodulator also provides amplitude information in the
By combining both the
resolution (better than 0.1dB) RSSI value can be computed at the expense of a few
arithmetic operations on the micro-controller. Formulas for this computation can be
found in the
features two receiver signal strength indicators (RSSI):
2
16
has a frequency tracking register
BITRATE
AX50424
×
Programming Manual.
FSKMUL
AGCCOUNTER
.
AX50424
and the
TRKFREQ
Programming Manual. For modulations
TRK_AMPLITUDE
to synchronize the receiver
TRK_AMPLITUDE
registers, a high
AGCCOUNTER
Datasheet AX50424
register.