Phase locked loop frequency and phase modulators
US4543542A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 3, 1984 |
| Grant date | Sep 24, 1985 |
| Priority date | — |
| Expiry date | May 3, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/1976
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A signal generator is arranged to produce frequency or phase modulation at frequencies which extend from a high value down to zero, i.e. to a d.c. level shift. The output oscillator forms part of a phase locked loop which also includes a variable frequency divider. A modulation signal is applied to the loop, so that high frequency modulation signals directly modify the control signal which determines the frequency of the oscillator, and so that low frequency modulation signals alter the divisor value of the variable frequency divider so as to modify the frequency characteristics of the phase locked loop. Quantization noise is reduced by applying a masking signal to an analogue-to-digital converter which utilizes the low frequency modulation signals to alter the divisor value.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.