Daewoo DTE-29G3ZZR, Service Manual, Page: 54 / 68

Appendix Service manual CP-795
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Phase and AM discrimination
The filtered sound IF signals are demodulated by means of the phase and amplitude discriminator block.
On the output, the phase and amplitude is available for further processing. AM signals are derived from
the amplitude information, whereas the phase information serves for FM and NICAM demodulation.
NICAM decoder
In case of NICAM - mode, the phase samples are decoded according the DQPSK - coding scheme. The
output of this block contains the original NICAM bitstream.
DSP section
All audio baseband functions are performed by digital signal processing (DSP). The DSP section controls
the source and output selection, and the signals processing.
Sound Mode switching
In case of NICAM transmission, the controlling software read the bit error rate and the operation mode
from the NICAM Decoder. When the set is in “Auto detection” mode ( default mode after ATSS ) the
controlling software set automatically the sound mode ( NICAM mono, NICAM Dual 1 or NICAM Dual
2 ) depending on the transmitted mode.
In case of 2 Carrier FM transmission, the controlling software read the transmission mode and the signal
quality level from the Stereo Detection Register. When the set is in “Auto detection” mode the controlling
software set automatically the sound mode ( mono, Stereo, Dual 1, Dual 2 ) depending on the transmitted
mode.
In “Auto detection” mode the controlling software evaluate the signal quality and automatically switch to
the analogy sound carrier 1, if the transmission quality is too poor. To avoid unwanted automatic
switching the threshold levels mono to stereo and stereo to mono is different.
In “forced mono “ mode ( Red OSD in recall section ), the controlling software configure the MSP3415D
to demodulate only the analogue (FM or AM) sound carrier 1, no matter the signal quality. The sound
mode “ forced “ or “ Autodetect” is stored for each programme.