TDA5230 Datasheet, PDF (84/186 Pages) Infineon Technologies AG – Universal Low Power ASK/FSK Single Conversion Multi-Channel Image-Reject Receiver

TDA523x
Functional Description
The higher the output of ASKNP, the better the reliability of the related data bit. The
signal detector uses this value to distinguish between acceptable data and unacceptable
data (e.g. noise).
f_sys
T_nom / 16
from
limiter
FSK
noise
power
meter
f_sys
T_nom / 16
threashold
+
signal power
detector
enable
threshold
T_nom / 16
data
clock recovery to clock
slicer
recovery
from
MUX
matched
filter
shift
register
delayed
data
signal power meter
data
data slicer chip data
to
(+1 0 -1)
decoder framer
T_nom / 16
recovered
clock
Figure 41 Matched Filter, Signal/Noise Detection and Slicer units
The polarity of the Manchester code can be inverted by setting the SFR control bit
DATINV.
Signal and Noise Detector
The Signal and the Noise Detector compare the outputs of ASKNP and FSKNP (see
FSK Demodulator) with configurable thresholds.
The Signal Detection Mode must be configured based on whether ASK or FSK
modulation is used:
• Signal power detection (=Squelch) only (related registers SIGDET0, SIGDET1 and
ASKNP). This mode is generally used for ASK and recommended for FSK.
• Noise power detection only (related registers NDTHRES and FSKNP).
• Signal and noise power detection simultaneously.
• Signal and noise power detection simultaneously, but the FSK noise detect signal is
valid only if the SIGDETLO threshold is exceeded. This is the recommended FSK
mode, if minimum FSK Deviation is not sufficient to use signal power detection only.
Data Sheet
80
Version 4.0, 2007-06-01