Digital modulator
US4049909A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 29, 1975 |
| Grant date | Sep 20, 1977 |
| Priority date | — |
| Expiry date | Oct 29, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/205
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A modulator for differentially encoded phase-shift keyed digital data is implemented entirely by digital means. Baseband serial binary data are illustratively transformed into dibit pairs which are assigned discrete quaternary carrier-wave phase shifts. A "staircasing" shift register whose weighted outputs are combined to form a quantized phase-modulated carrier wave is advanced by a relatively high-speed counter through a frequency divider network. The division rate of the divider is selectively accelerated in each baud interval in accordance with the assigned dibit coding. The resultant quantized carrier wave is then lowpass filtered prior to application to a telephone transmission line. By controlling the division rate of the divider rather than the advancement rate of the shift register, gradual transitions are imparted to the output carrier wave with minimal harmonic distortion.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.