Multi-carrier high speed modem
US4943980A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 2, 1989 |
| Grant date | Jul 24, 1990 |
| Priority date | — |
| Expiry date | May 2, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/2657
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A modem system includes a transmitter section having generators for successively generating sets of carrier signals where each carrier signal of a set has a different frequency and a modulator for modulating each carrier signal of a set with a different portion of digital data to be transmitted where all such portions used to modulate a set of carrier signals comprise a frame of digital data. Also included are an adder for successively combining together the modulated carrier signals of each set to produce a frame waveform, an inverse Fast Fourier Transform circuit for transforming each waveform from a frequency domain signal to a time domain signal, a rotate and match buffer circuit for rotating each transform waveform so that its beginning point amplitude and slope substantially match the ending point amplitude and slope of the immediately preceding transformed waveform, and a transmitter for successively and continuously transmitting the transformed and rotated waveforms over a telephone channel. The modem system also includes a receiver section having a circuit for receiving from the telephone channel transmitted signals, a rerotate circuit for rerotating each received waveform…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.