Philips msp34xx Service Manual
APPLICATION NOTE IC
Micronas
MSP 34xx Family
Recommendations for
Applications with
Intercarrier IF-Signals
Edition March 15, 2000
6251-495-2AN
MICRONAS
APPLICATION NOTE IC MSP 34xx Family
Recommendations for Applications
with Intercarrier IF-Signals
In order to avoid clipping effects at the IF-A/D converter of the MSP, the video, chroma, and sync signal
components, which are included in the intercarrier
sound-IF-signal (see Fig. 1, left), should not exceed
300 mVpp at the ANA_IN1/2+ MSP IF-input. Such clipping can cause a high NICAM error rate and loss of
SNR performance with FM signals.
Basic Recommendations
1. If an intercarrier IF-input signal is used (see Fig. 1,
left) for the IF-input of the MSP family, it is recommended to use a simple IF-amplifier and a bandpass- or highpass-filter in front of the MSP IF-input
to attenuate the video, chroma, and sync signal
components.
2. For the European market, a bandpass ranging from
5.3 MHz to 6.7 MHz should be used to eliminate the
video and chroma signal components.
3. For the M-standards, a bandpass ranging from
4.3 MHz to 4.7 MHz is recommended. Instead of a
bandpass filter, a highpass filter at 5.3 MHz (or at
4.3 MHz for standard M) can also be used.
4. Due to the filter loss and additional tolerances of the
sound carrier (normally 100 mVpp with a 1 Vpp
intercarrier signal), an analog gain of about +9 dB or
more is required as well. Tests have shown that the
filter attenuation at the chroma carrier frequency
should be about −12 dB or mor e re lat iv e to t he m ain
sound carrier.
5. The filtered IF-signal (sound carrier) at the MSP
input should have a minimum level of 100 mVpp.
6. For standard NICAM-L, with a 6.5 MHz AM soundcarrier, a Quasi Split Sound (QSS) IF-Demodulator
is recommended to avoid loss of AM-performance
caused by the video and chroma signal components.
Examples for Bandpass Filter Circuits
The diagrams on the following pages show examples
for the IF-spectrum, for the circui t, and the frequency
characteristic of such bandpass filters.
Micronas 1
MSP 34xx Family APPLICATION NOTE IC
Fig. 1: Spectrum of typical intercarrier IF-signal (left) and
Quasi Split Sound (QSS) IF (right) for PAL, NICAM B/G
Fig. 2: Measured input-spectrum (left) and
output-spectrum (r i ght )
with the bandpass for the European Market (PAL, NICAM B/G)
2 Micronas
Loading...