Technique for communicating digitally modulated signals over an amplitude-modulation frequency band
US6445750B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 22, 1998 |
| Grant date | Sep 3, 2002 |
| Priority date | — |
| Expiry date | Apr 22, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/2646
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
In a communications system implementing an in-band on channel AM (IBOC-AM) (also known as “hybrid IBOC-AM”) scheme, digitally modulated signals are transmitted in a 30 kHz digital band centered at an analog host AM carrier frequency fc. The host AM carrier is assigned to the geographic area served by the communications system for AM radio broadcast. It is likely that a similar IBOC-AM scheme is implemented in an adjacent area which is assigned a second analog host AM carrier having a frequency which is either 20 kHz higher or lower than fc. In that case, the transmission of the digitally modulated signals are interfered by a similar transmission in the adjacent area. The interference is known as “second adjacent channel interference.” To reduce such interference, selected power profiles in accordance with the invention are used to allocate the relative transmission power to the digitally modulated signals in the digital band.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.