초록 ▼

A system and method for transmitting digital information through a medium such as atmospheric free-space includes a transmitter which generates a signal based on a basis set of mutually orthogonal, spectrally-shaped, sequences of substantially equal length and having predetermined autocorrelation va

A system and method for transmitting digital information through a medium such as atmospheric free-space includes a transmitter which generates a signal based on a basis set of mutually orthogonal, spectrally-shaped, sequences of substantially equal length and having predetermined autocorrelation values. The sequences may resemble noise in at least some of their characteristics. The orthogonality or cross-correlation characteristics, the autocorrelation characteristics and the resemblance to noise are due to features derived from sequences of pseudo-random numbers which themselves resemble noise in at least some of their characteristics. The waveform set based on the sequences is modulated digitally. The modulated set may be summed together along with a wideband reference signal of reduced amplitude and optionally an FM analog signal to form a composite signal which is broadcast typically through free space to at least one receiver. The receiver separates the analog FM signal from the digital signal and thereafter demodulates the digital data-carrying waveforms and outputs a stream of digital data. It has been determined to be resistant to multipath degradation.

대표청구항 ▼

[ What is claimed is:] [1.] An apparatus for transmitting a digital signal which is robust to multipath degradation and intersymbol interference, the apparatus comprising:means for generating a basis set of sequences, each of said sequences comprises multi-valued codes to provide predetermined autoc

[ What is claimed is:] [1.] An apparatus for transmitting a digital signal which is robust to multipath degradation and intersymbol interference, the apparatus comprising:means for generating a basis set of sequences, each of said sequences comprises multi-valued codes to provide predetermined autocorrelation characteristics, each of said sequences being spectrally shaped with a shaping function and being substantially orthogonal to one another;means for data modulating and summing together the basis set of sequences to define a digital signal, the modulated set maintaining a preselected spectral shape through the modulating; andmeans for transmitting through a medium the digital signal to a receiver.