Elimination of phase noise and drift incident to up and down conversion in a broadcast communication system
US5109532A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 30, 1990 |
| Grant date | Apr 28, 1992 |
| Priority date | — |
| Expiry date | Jan 30, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D3/242
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Phase noise and drift in a broadcast communication system caused by imperfections in transmitter and receiver local oscillators used for up and down conversion of a frequency or phase modulated information signal is eliminated from a downconverted component that is provided for demodulation by adding a pilot frequency component to the modulated signal for mixing by the local oscillator in the transmitter and by frequency locking the local oscillator in the receiver, so that a signal at a frequency equal to the sum of the intermediate frequency and the pilot frequency provided by a phase-locked loop that tracks the pilot frequency component of the downconverted signal is maintained at a desired value. The downconverted signal is mixed with the sum signal provided by the phase-locked loop to provide a component for demodulation at the difference between the pilot frequency and the modulation frequency that is free from the phase noise and drift caused by the local oscillators. Since the phase noise and drift caused by the local oscillators affects the phases of the modulation frequency information component and the pilot frequency component equally, the frequency modulated informatio…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.