ax5051 AXSEM, ax5051 Datasheet - Page 24

• Manufacturer Part Number: ax5051
• Description: Ax5051 Radio
• Manufacturer: AXSEM

24
Circuit Description
Registers
Register
CICDEC
DATARATEHI, DATARATELO
TMGGAINHI, TMGGAINLO
MODULATION
PHASEGAIN, FREQGAIN,
FREQGAIN2, AMPLGAIN
AGCATTACK, AGCDECAY
TXRATE
FSKDEV
5.9.
The encoder is located between the Framing Unit, the Demodulator and the Modulator. It
can optionally transform the bit-stream in the following ways:
The encoder is programmed using the register ENCODING, details and recommendations on
usage are given in the
Version 1.6
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Encoder
It can invert the bit stream.
It can perform differential encoding. This means that a zero is transmitted as no
change in the level, and a one is transmitted as a change in the level. Differential
encoding is useful for PSK, because PSK transmissions can be received either as
transmitted or inverted, due to the uncertainty of the initial phase. Differential
encoding / decoding removes this uncertainty.
It can perform Manchester encoding. Manchester encoding ensures that the
modulation has no DC content and enough transitions (changes from 0 to 1 and from
1 to 0) for the demodulator bit timing recovery to function correctly, but does so at a
doubling of the data rate.
It can perform Spectral Shaping. Spectral Shaping removes DC content of the bit
stream, ensures transitions for the demodulator bit timing recovery, and makes sure
that the transmitted spectrum does not have discrete lines even if the transmitted
data is cyclic. It does so without adding additional bits, i.e. without changing the
data rate. Spectral Shaping uses a self synchronizing feedback shift register.
AX5051
This register programs the bandwidth of the digital channel filter.
These registers specify the receiver bit rate, relative to the channel filter
bandwidth.
These registers specify the aggressiveness of the receiver bit timing recovery.
More aggressive settings allow the receiver to synchronize with shorter
preambles, at the expense of more timing jitter and thus a higher bit error rate
at a given signal-to-noise ratio.
This register selects the modulation to be used by the transmitter and the
receiver, i.e. whether ASK, PSK , FSK, MSK or OQPSK should be used.
These registers control the bandwidth of the phase, frequency offset and
amplitude tracking loops. Recommended settings are provided in the
Programming Manual.
These registers control the AGC (automatic gain control) loop slopes, and thus
the speed of gain adjustments. The faster the bit-rate, the faster the AGC loop
should be. Recommended settings are provided in the Programming Manual.
These registers control the bit rate of the transmitter.
These registers control the frequency deviation of the transmitter in FSK mode.
The receiver does not explicitly need to know the frequency deviation, only the
channel filter bandwidth has to be set wide enough for the complete
modulation to pass.
Programming Manual.
Remarks
Datasheet AX5051