GDC21D003 Datasheet, PDF (57/77 Pages) Hynix Semiconductor – VSB Receiver

6.5.2 Gain & Offset Loop
There are three loops in phase tracker and these
loops are designed to be ON/OFF through I²C bus.
The first loop is Gain Loop. The Gain Loop
consists of multiplier and accumulator, and corrects
gain error caused by phase error with error value
from an error decision. The output of equalizer is
the first gain controlled by a multiplier. The second
amplitude
GDC21D003
loop is Offset Loop which consists of adder and
accumulator. The Offset Loop corrects offset error
caused by phase error with error value from an
error decision. The gain-corrected output is used to
remove offset error at Offset Loop and used at the
Hilbert transform filter to generate an
approximation of the Q signal. Figure 6.5.3 shows
the shape of coefficients of Hilbert Transform filter.
time
Figure 6.5.3 Coefficients of Hilbert Transform Filter
6.5.3 Phase Loop
The last loop is Phase Loop which consists of adder,
accumulator, Sine Cosine Table, and Complex
Multiplier. The gain & offset of corrected I and Q
signal is derotated at complex multiplier to correct the
phase error and Figure 6.5.4 shows the diagram of
complex multiplier for a derotation.
I’
+
I”
cos
-
Q’
sine
+
Q”
+
sine
cos
Figure 6.5.4 Complex Multiplier
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