Daewoo DWP-28W2ZZF Service Manual download pdf (Page 56)

Appendix Service manual WP-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.

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Daewoo DWP-28W2ZZF Service Manual Page 56