Method and apparatus for demodulating multi-level QAM signal
US6028475A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 12, 1998 |
| Grant date | Feb 22, 2000 |
| Priority date | — |
| Expiry date | Aug 12, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/38
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Disclosed is a demodulating apparatus for preventing a reduction in reliability of demodulated data even if a signal point of a multi-level QAM signal is detected, because of influence from fading or noises, in a position where such a signal is not normally existent. To this end, a modulated signal modulated by a multi-level QAM modulation system is orthogonally detected, and analog signals of I and Q channels placed in an orthogonal relationship with each other are outputted. By an identification device, the analog demodulated signals are digitized and then outputted as digital demodulated signals of I and Q channels. If a signal point outside a normal signal point arrangement is detected among the outputs, a digital demodulated signal within a normal signal point arrangement is substituted for the detected signal and then original code data is reproduced.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.