AM Stereo phase modulation decoder
US4362999A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 15, 1980 |
| Grant date | Dec 7, 1982 |
| Priority date | — |
| Expiry date | Oct 15, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04H20/49
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A decoder for obtaining the L-R information in an AM stereo radio receiver. The decoder is basically a four-quadrant multiplier that has one pair of inputs driven from a limiter that operates from the receiver intermediate frequency amplifier. The limiter also drives a tuned circuit which in turn drives the other two multiplier inputs in phase quadrature with the first input pair. The multiplier output is frequency modulation responsive which, when integrated, produces a phase modulation response. The integration is produced by a capacitor connected across the multiplier output terminals. The decoder also includes a large parallel connected inductor that resonates the integrating capacitor at a frequency at the low end of the audio range. This inductor acts as a d-c short at the decoder output and sets the decoder response to the setaudible stereo pilot signal. The inductor is simulated with integrated circuit components. A first transconductance amplifier coupled to the multiplier output, drives a capacitor which in turn drives a second transconductance amplifier that operates current sources which act as load elements for the multiplier. The resultant feedback loop creates an ind…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.