Digital MSK modulator
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorDon M. French
Life of this patent
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Abstract
A digital apparatus for performing minimum-shift-keying (MSK) modulation includes an oscillatory circuit which provides two frequencies related in a predetermined manner, and also includes a processing circuit which divides a stream of digital data to be transmitted into two parallel substreams, one substream comprising even numbered bits from the serial stream and the other substream comprising odd numbered bits from the serial stream. A combining circuit selects one of the frequencies provided by the oscillatory circuit according to the equivalence or divergence of the states of the digital substreams, and further provides as an output the selected frequency waveform or its inverse according to the state of one of the substreams.
Claims14
A digital minimum-shift-keying modulator, comprising:
- oscillatory circuit means responsive to a master clock signal of fixed frequency for providing a first digital waveform of variable frequency and a second digital waveform of variable frequency not equal to the first, wherein the first and second frequencies are related in a predetermined manner;
- processing circuit means responsive to a serial stream of digital data, the data stream having a variable clock frequency, f.sub.o, and comprising successive bit periods, the processing circuit means separating the serial stream into two substreams each having a clock frequency f.sub.o /2, one substream comprising the succession of even-numbered bit periods of the serial stream and the other substream comprising the succession of odd-numbered bit periods of the serial stream;
- and
- combining circuit means coupled to the oscillatory means and the processing means for selecting one digital waveform when the states of the substreams are equivalent or the other digital waveform when the states of the substreams are opposite, and for responding to the state of one substream when the selection is made to provide either the selected waveform or its inverse as an output.
Dependencies are inferred from the claim text.