Wideband multi-channel quadrature amplitude modulation of cable television signals
US7068730B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | May 6, 2005 |
| Grant date | Jun 27, 2006 |
| Priority date | — |
| Expiry date | May 6, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/34
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Wideband, direct-to-RF multi channel QAM modulation is described whereby IFFT processing is employed to modulate a plurality of encoded symbol streams in parallel onto a like plurality of uniformly spaced carriers. A high-frequency master clock and high-performance, high-frequency D/A converters are employed. The IFFT modulation process yields a multi-channel multiplex at an intermediate “baseband” frequency. The multi-channel multiplex is then synchronously converted to analog form and synchronously frequency shifted upward by one-half the master clock frequency using a quadrature doubly-balanced mixing scheme. The resultant multi-channel encoded multiplex occupies a frequency band centered around one half the master clock frequency. Multi-rate techniques can be employed to yield high-speed digital processing from digital logic incapable of operating directly at the master clock frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.