AM compatible digital waveform demodulation using a dual FFT
US5633896A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 21, 1996 |
| Grant date | May 27, 1997 |
| Priority date | — |
| Expiry date | Feb 21, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04H2201/186
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
The invention provides a method and apparatus for demodulating a composite AM DAB waveform which contains digitally modulated carriers and which employ (1) a mixer for converting a received signal into two signals (the first of these two signals represents an in-phase component and the second of these two signals represents a quadrature component); (2) two analog-to-digital converters for converting the two signals into digital signals; and (3) two fast Fourier transform elements for extracting data separately from the two digital signals. Complementary digital carrier signals are recovered from the quadrature component, and non-complementary digital carriers are derived from a sum of the complementary data and the output of the in-phase component FFT process. Leakage of the AM signal through a highpass filter is prevented from interfering with the demodulation of the complementary carrier signals' use of separated demodulation channels.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.