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Abstract

A satellite communications system for dispersing energy over a wide bandwidth includes a transmitter, a communication link, and a receiver. The transmitter takes a digital data signal and modulates that signal at a prescribed carrier frequency. The modulated digital data signal is then spread over M adjacent digital channels (M.gtoreq.2 and being an integer multiple of 2), each channel containing the same information, to disperse the energy over a wide frequency range. The spectral bandwidth of the adjacent digital channels is chosen with compressed spacing to conserve bandwidth. Next, the spread modulated data signal is transmitted via the communication link to the receiver. In particular, a waveform generator at the transmitter generates a phase-aligned multichannel frequency diversity waveform according to a data clock at a predetermined phase relationship to the digital data. At the receiver, the spread modulated data signal received is mixed with a despreading waveform generated in a similar manner to the waveform spectrum generated at the transmitter to recover the modulated data signal. The despreading waveform is generated according to a symbol clock signal recovered from the received modulated data signal. A demodulator recovers the original digital data from the modulated data signal. To achieve higher spreading factors, multichannel frequency diversity may be utilized with known spread spectrum techniques to achieve high data recovery rates during adverse weather (fading) conditions at high radio frequencies in the microwave and higher regions of the radio spectrum.

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First Claim