Digital signal transmission system using frequency division multiplex
US5610908A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 28, 1995 |
| Grant date | Mar 11, 1997 |
| Priority date | — |
| Expiry date | Jul 28, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/2634
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A frequency-division multiplexer for carrying an OFDM signal on a large number of closely-spaced carriers receives the digital data at an input (12), applies coding such as convolutional coding (14), time interleaves (16) the signals, and assembles them frame-by-frame in a matrix (18). The data are converted to parallel form by a shift register (18), frequency interleaved (24), differentially encoded (26), and quadrature-phase-modulated (28) on several hundred or more closely-spaced carriers. A first inverse Fast Fourier Transform (FFT) circuit (30) transforms this information from the frequency domain into the time domain. Instead of being transmitted directly, the resultant signals are then amplitude-limited (42) and applied to an FFT (44) to reconvert them into the frequency domain. The phases of the wanted signals are then re-set, and the amplitudes of the signals near the edges of the band are reduced, in correction circuits (46). The resultant signals are applied to a second inverse FFT (48) for transmission. The output of the second inverse FFT contains smaller power peaks than the output of the first inverse FFT (30). The output is converted to serial form by a shift regist…
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