LA7578N 데이터 시트보기 (PDF) - SANYO -> Panasonic
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LA7578N Datasheet PDF : 18 Pages
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LA7578N
If this phase distortion (θ) appears, the PLL VCO will be modulated in synchronization with the error voltage, which causes the
generation of a buzz. At Sanyo, this buzz generated by the phase distortion (θ) is called ‘‘Nyquist buzz.’’ The LA7578N includes a
new Nyquist buzz canceller circuit that suppresses this Nyquist buzz generated by the phase distortion (θ) in an effort to greatly
improve the buzz characteristics. Fig. 3 shows the PLL detection system in the LA7578N, which uses this Nyquist buzz canceller
circuit.
Fig. 3 PLL Detector with Nyquist Buzz Canceller
In the PLL detection system with the Nyquist buzz canceller, even if phase distortion such as that shown in A is generated, the
phase distortion in the APC detection output can be eliminated by generating and adding in a quasi-reverse phase buzz signal.
Nyquist buzz
Quasi-reverse phase buzz
Fig. 4 Nyquist Buzz Canceller Waveforms
The effect of this Nyquist buzz canceller circuit is to broadly suppress the buzz (fH harmonic ) generated as a sideband of the SIF
beat signal (4.5 MHz). As a result, great improvements can be made in regard to the buzz beat generated during demodulation of
Japan audio multiplexing (L-R) and the buzz characteristics during demodulation of U.S. MTS (Multichannel TV Sound) (L-R).
Furthermore, because this Nyquist buzz cancellation method has no effect on the time constant of the PLL loop, it is also possible
to try to improve various characteristics, by making it possible to, for example, design an APC filter that is not readily affected by
flyback pulses (F.B.P), etc.
No.4037-8/18
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