Phase distortion adaptive detector of minimum shift keying data
First Claim
1. In a minimum shift keying data detection system employing a pair of intelligence-defining symbols comprised of concatenate-like intervals of one or the other of first and second tones f1 and f2, said tones each having a respective phase, where f1 equals f2 /2 and where said interval comprises one-half cycle period of f1, an improved detection system for identifying respective ones of concatenate symbols applied thereto comprising:
- means for measuring the differential relationship of said phase of said first tone with respect to said phase of said second tone including;
first and second phase adjustable tone generators, each of said first and second tone generators generating first and second reference generator quadraturized outputs;
the quadraturized outputs from said first tone generators applied respective first inputs to respective first and second exclusive-OR gates;
the quadraturized outputs from said second tone generators being applied as respective first inputs to respective third and fourth exclusive-OR gates;
said concatenate symbols being applied as respective second inputs to each of said first, second, third and fourth exclusive-OR gates;
first, second, third and fourth up-down binary counters receiving the respective outputs from said first, second, third and fourth exclusive-OR gates;
means for providing a clock input to each of said counters, said clock input having a repetition rate in excess of the time duration of said inputted symbols;
means for phase locking the output of said first reference signal generator to the applied f2 tone;
means for sampling the respective quadraturized outputs of each of said f1 counters at said clock and averaging said samples for the duration of said f1 time input symbols;
means for comparing the absolute value of the averaged sampled output from said f1 counter to obtain a measure of the phase relationship of tone f1 with respect to tone f2 ; and
means for resetting each of said binary counters to zero at the conclusion of each concatenate input symbol-defining interval;
means to establish predistorted first and second cross-correlated tone reference waveforms in accordance with said differential phase relationship; and
means for correlating the concatenate tone-defined symbols applied to said detection system against respective ones of said predistorted tone reference waveforms to identify successively applied ones of said intelligence-defining symbols.
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Abstract
The minimum shift keying (MSK) data detection system described compensates for the differential phase shift distortion produced by passing the MSK signal through a voice grade audio channel such as a VHF AM transmitter and receiver. This distortion varies and is dependent on the particular transmitter and receiver being used. The detection system examines the preamble of the MSK signal and measures the differential phase shift of the two modulating tone. This measured value is then used to establish pre-distorted waveforms to which the incoming data is compared for detection.
10 Citations
4 Claims
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1. In a minimum shift keying data detection system employing a pair of intelligence-defining symbols comprised of concatenate-like intervals of one or the other of first and second tones f1 and f2, said tones each having a respective phase, where f1 equals f2 /2 and where said interval comprises one-half cycle period of f1, an improved detection system for identifying respective ones of concatenate symbols applied thereto comprising:
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means for measuring the differential relationship of said phase of said first tone with respect to said phase of said second tone including; first and second phase adjustable tone generators, each of said first and second tone generators generating first and second reference generator quadraturized outputs; the quadraturized outputs from said first tone generators applied respective first inputs to respective first and second exclusive-OR gates; the quadraturized outputs from said second tone generators being applied as respective first inputs to respective third and fourth exclusive-OR gates; said concatenate symbols being applied as respective second inputs to each of said first, second, third and fourth exclusive-OR gates; first, second, third and fourth up-down binary counters receiving the respective outputs from said first, second, third and fourth exclusive-OR gates; means for providing a clock input to each of said counters, said clock input having a repetition rate in excess of the time duration of said inputted symbols; means for phase locking the output of said first reference signal generator to the applied f2 tone; means for sampling the respective quadraturized outputs of each of said f1 counters at said clock and averaging said samples for the duration of said f1 time input symbols; means for comparing the absolute value of the averaged sampled output from said f1 counter to obtain a measure of the phase relationship of tone f1 with respect to tone f2 ; and means for resetting each of said binary counters to zero at the conclusion of each concatenate input symbol-defining interval; means to establish predistorted first and second cross-correlated tone reference waveforms in accordance with said differential phase relationship; and means for correlating the concatenate tone-defined symbols applied to said detection system against respective ones of said predistorted tone reference waveforms to identify successively applied ones of said intelligence-defining symbols. - View Dependent Claims (2, 3, 4)
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Specification