Digital pulse position modulation communications system with threshold extension
First Claim
1. In a digital pulse position modulation communications system including receiver means responsive to RF signals including a pulse position modulation communication signal transmitted from a communications signal source, coherent signal detector means responsive to IF pulse position modulation communications signals generated by said receiver means comprising:
- quadrature phase type coherent video detector means coupled to said receiver means and being operable to generate envelope detected video pulse position modulated communication signals in response to said IF pulse position modulated communications signals;
a split gate prf loop, coupled to said coherent video detector means and operating as a coherent signal detector in response to said envelope detected video pulse position modulated communications signals; and
signal filter means coupled to said prf loop for providing an output comprising said communications signal.
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Abstract
A digital pulse position modulation (PPM) communications system with threld extension including a radio receiver for achieving optimum coherent detection of a pulse position modulated communication signal including a coherent video detector coupled to the IF output of the radio receiver and a pulse repetition frequency loop locked to the detected video signals containing position modulation. The pulse repetition frequency loop includes a time discriminator, a filter, a voltage controlled oscillator, and a split gate generator providing a split gate no greater than the width of the applied video signal. The split gate is applied to the time discriminator resulting in the detected video signal being multiplied by itself or coherently detected. A low pass filter is connected to the output of the discriminator to provide a demodulated communications analog or quasi-analog output signal such as a voice signal, transmitted to the receiver from a digitally coded PPM communications transmitter.
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Citations
15 Claims
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1. In a digital pulse position modulation communications system including receiver means responsive to RF signals including a pulse position modulation communication signal transmitted from a communications signal source, coherent signal detector means responsive to IF pulse position modulation communications signals generated by said receiver means comprising:
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quadrature phase type coherent video detector means coupled to said receiver means and being operable to generate envelope detected video pulse position modulated communication signals in response to said IF pulse position modulated communications signals; a split gate prf loop, coupled to said coherent video detector means and operating as a coherent signal detector in response to said envelope detected video pulse position modulated communications signals; and signal filter means coupled to said prf loop for providing an output comprising said communications signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15)
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- phase shift means coupling said second IF signal to the other input of said second phase detector, and
circuit means coupling a pulse position modulation video signal pulse train from said second phase detector to said time discriminator.
- phase shift means coupling said second IF signal to the other input of said second phase detector, and
Specification