Frequency modulation using a phase modulator
US4503405A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 12, 1983 |
| Grant date | Mar 5, 1985 |
| Priority date | — |
| Expiry date | Sep 12, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03C3/00
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A frequency modulator circuit arrangement, comprising a phase modulator (1) having a carrier signal input (2) which is fed from a carrier signal generator (18) and a modulation signal input (3) which is fed from a modulation signal input terminal (6) via an integrated circuit (7), includes a controllable frequency divider (16) in the carrier signal path through the phase modulator enabling the arrangement to operate with input modulation signals containing d.c. components without the integrator circuit output signal reaching impossibly high values. If the integrator output signal exceeds a first threshold (at terminal 26), a D-type flip-flop (27) is tripped causing a switch 28 to close, reducing the charge in the integrator capacitor (10) via a resistor (22) and hence changing the phase shift produced by the phase modulator. The division factor of the divider is simultaneously changed for one or more divisions cycles to introduce a compensating steady phase shift. Similar operations occur when the integrator circuit exceeds a second, negative, threshold (at terminal 13), a switch 20 then being closed and the division factor being simultaneously changed in the opposite direction by …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.