MSP3405D Datasheet, PDF (12/71 Pages) List of Unclassifed Manufacturers – Multistandard Sound Processors

MSP 34x5D
PRELIMINARY DATA SHEET
4.1.4. 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 (DQPSK) demodulation.
4.1.5. Differentiators
FM demodulation is completed by differentiating the
phase information output.
4.1.6. Low-pass Filter Block
for Demodulated Signals
The demodulated FM and AM signals are further low-
pass filtered and decimated to a final sampling frequen-
cy of 32 kHz. The usable bandwidth of the final base-
band signals is about 15 kHz.
4.1.7. High Deviation FM Mode
By means of MODE_REG [9], the maximum FM-devi-
ation can be extended to approximately ±360 kHz. Since
this mode can be applied only for the MSP sound IF
channel 2, the corresponding matrices in the baseband
processing must be set to sound A. Apart from this, the
coefficient sets 380 kHz FIR2 or 500 kHz FIR2 must be
chosen for the FIR2. In relation to the normal FM-mode,
the audio level of the high-deviation mode is reduced by
6 dB. The FM-prescaler should be adjusted accordingly.
In high deviation FM-mode, neither FM-stereo nor FM-
identification nor NICAM processing is possible simulta-
neously.
4.1.8. FM-Carrier-Mute Function
in the Dual Carrier FM Mode
To prevent noise effects or FM identification problems in
the absence of one of the two FM carriers, the
MSP 3415 D offers a carrier detection feature, which
must be activated by means of AD_CV[9]. If no FM carri-
er is available at the MSPD channel 1, the correspond-
ing channel FM2 is muted. If no FM carrier is available
at the MSPD channel 2, the corresponding channel FM1
is muted.
4.1.9. DQPSK-Decoder (MSP 3415D only)
In case of NICAM-mode, the phase samples are de-
coded according the DQPSK-coding scheme. The out-
put of this block contains the original NICAM-bitstream.
4.1.10. NICAM-Decoder (MSP 3415D only)
Before any NICAM decoding can start, the MSP must
lock to the NICAM frame structure by searching and syn-
chronizing to the so-called Frame Alignment Words
(FAW).
To reconstruct the original digital sound samples, the NI-
CAM-bitstream has to be descrambled, deinterleaved,
and rescaled. Also, bit error detection and correction
(concealment) is performed in this NICAM specific
block.
To facilitate the Central Control Unit CCU to switch the
TV-set to the actual sound mode, control information on
the NICAM mode and bit error rate are supplied by the
the NICAM-Decoder. It can be read out via the I²C-Bus.
An automatic switching facility (AUTO_FM) between NI-
CAM and FM/AM reduces the amount of CCU-instruc-
tions in case of bad NICAM reception.
12
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