METHOD AND SYSTEM FOR SIMULTANEOUSLY BROADCASTING AND RECEIVING DIGITAL AND ANALOG SIGNALS

摘要

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 (37). 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 (39). The modulated set may be summed together along with a wideband reference signal (41) of reduced amplitude and optionally an FM analog signal (7) to form a composite signal which is broadcast typically through free space to at least one receiver. The receiver separates the analog FM signal (11) 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.