MSP 3400C
PRELIMINARY DATA SHEET
START
6.4.3. Automatic Search Function for FM-Carrier De-
tection
LOAD_SEQ_1/2
Channel 1:
The AM demodulation ability of the MSP 3400C offers
the possibility to calculate the “field strength” of the mo-
mentarily selected FM carrier, which can be read out by
the CCU. In SAT receivers, this feature can be used to
make automatic FM carrier search possible.
FM2 Parameter
Channel 2:
FM1 Parameter
Therefore, the MSPC has to be switched to AM-mode
(MODE_REG[8]), FM-Prescale must be set to
Audio Processing Init
7F =+127 , and the FM DC Notch must be switched
hex
dez
off. The sound-IF frequency range must now be
“scanned” in the MSPC-channel 2 by means of the pro-
grammable quadrature mixer with an appropriate incre-
mental frequency (i.e. 10 kHz).
Pause
Bilingual
After each incrementation, a field strength value is avail-
able at the quasi-peak detector output (quasi-peak de-
tector source must be set to FM), which must be ex-
amined for relative maxima by the CCU. This results in
either continuing search or switching the MSP 3400C
back to FM demodulation mode.
< –t
Set FM Matrix:
To NO_MATRIX
FM_
IDENT_CHECK
0x0018
Set Channel Matrix:
To SOUND A or B
Mono
Set FM Matrix:
During the search process, the FIR_REG_2 must be
loaded with the coefficient set “AUTOSEARCH”, which
enables small bandwidth, resulting in appropriate field
strength characteristics. The absolute field strength val-
ue (can be read out of “quasi peak detector output FM1”)
also gives information on whether a main FM carrier or
a subcarrier was detected, and as a practical conse-
quence, the FM bandwidth (FIR_REG_1/2) and the
deemphasis (50 µs or adaptive) can be switched auto-
matically.
To NO_MATRIX > –t & < t
Set Channel Matrix:
To SOUNDA
Stereo
Set FM Matrix:
To G/KMATRIX
> t
Set Channel Matrix:
To STEREO
Fig. 6–1: CCU software flow diagram: Standard B/G,
t = threshold value for stereo/bilingual detection
Due to the fact that a constant demodulation frequency
offset of a few kHz, leads to a DC-level in the demodu-
lated signal, a further fine tuning of the found carrier can
be achieved by evaluating the “DC Level Readout FM1”.
Therefore, the FM DC Notch must be switched on, and
the demodulator part must be switched back to FM-de-
modulation mode.
START
LOAD_SEQ_1/2
MSP-Channel 1:
FM2-Parameter
For a detailed description of the automatic search func-
tion, please refer to the corresponding MSP 3400C Win-
dows software.
MSP-Channel 2:
FM1-Parameter
Note: The automatic search is still possible by evaluat-
ing only the DC Level Readout FM1 (DC Notch On) as
it is described with the MSP 3410, but the above men-
tioned method is faster.
Audio Processing Init
STOP
6.4.4. Automatic Standard Detection
Fig. 6–2: CCU software flow diagram: SAT-mode
The AM demodulation ability of the MSP 3400 C en-
ables a simple method of deciding between standard
B/G (FM-carrier at 5.5 MHz) and standard I (FM-carrier
at 6.0 MHz). It is achieved by tuning the MSP 3400C in
the AM-mode to the two discrete frequencies and eva-
luating the field strength via the DC level register or the
quasi-peak detector output (Mode_Reg, DC Notch, FM
Prescale as described in section 6.4.3.).
6.4.2. Satellite Mode
Fig. 6–2 shows the simple flow diagram to be used for
the MSP 3400C in a satellite receiver. For FM-mono
operation, the corresponding FM carrier should prefer-
ably be processed at the MSPC-channel 2 or at the
MSPC-channel 1 with FIR gain = 0 dB.
28
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