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STEREOPHONIC ENCODER

IP.com Disclosure Number: IPCOM000005447D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2001-Oct-10
Document File: 1 page(s) / 48K

Publishing Venue

Motorola

Related People

Yoshio Sakaie: AUTHOR

Abstract

In the transmission of an AM stereophonic signal, It is possible to create distortion by amplitude modulating a phase-modulated and limlted quadrature signal by a signal of the form 1 + L+ A wherein the percentage modulation of the envelope is significantly different from the percentage modulation of the in-phase component of the quadrature signal.

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Volume 2 January 1982

STEREOPHONIC ENCODER By Yoshio Sakaie

   In the transmission of an AM stereophonic signal, It is possible to create distortion by amplitude modulating a phase-modulated and limlted quadrature signal by a signal of the form 1 + L+ A wherein the percentage modulation of the envelope is significantly different from the percentage modulation of the in-phase component of the quadrature signal.

   This type of distortion co;ild be prevented by the circuit shown in the figure wherein a quadrature generator 10 with input signals of L and R, provides an output signal at point 12 which is a pure quadrature signal, modulated by L-R and L+ R. This signal is limited in a limiter 14 to remove all amplitude variations. The limited signal is coupled to the transmitter modulation stage 16 where it is modulated, at a high level, by the sum signal 1 + L+ R from an envelope detector 18, the sum signal being derived from the in-phase (I) component of the quadrature signal.

   The sum signal derived from I is, however, first coupled to a comparator 20 for comparison with the output of a second envelope detector 22 which detects the amplitude modulation on the transmmitter output signal at a terminal 24. The error signal from the comparator20, which may be coupled through an amplifier 26, thus forces the percentage of amplitude modulation at terminal 24 to be the same as that at point 12.

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21

0 Motorola. Inc. 1982

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