Equivalent Circuit Block Diagram

Multinetwork PLL (Automatic Adjustment Control)

The LA7583’s PIF detector uses a multinetwork PLL and a buzz canceller. The multinetwork PLL is a PLL detector that was

developed in order to eliminate the need for adjustments in video detection.

This PLL detector offers the following features:

(1) Eliminates the need for adjustments in video detection.

(2) The PLL detection characteristics are unaltered.

a. Offers better waveform response characteristics in comparison with the quasi-synchronous detection method.

b. The harmonic wave component of the video signal (demodulated output) is reduced.

c. The 1/2 IF signal suppression ratio is improved.

(3) Audio buzz is greatly reduced by the buzz canceller.

A typical PLL detector consists of the blocks shown below.

In these blocks, if the VCO coil is not adjusted to the IF frequency, a phase difference will appear in the control loop. As a result,

the PLL detector detection axis will shift from the ideal 180 °. The group delay, DP characteristics, etc., deteriorate as a result.

LA7583

No.5177-5/16