Arc-cosine phase modulators
First Claim
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1. A phase modulator responsive to an input signal and to a carrier signal comprising:
- first means for developing a signal proportional to the inverse hyperbolic tangent of said input signal;
second means, responsive to said first means and to said carrier signal for generating a signal which is proportional to a sum of two signals that are exponentially related to the output signal of said first means and which is amplitude modulated with said carrier signal; and
third means for hard limiting the output signal of said second means.
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Abstract
Arc-cosine phase modulation is achieved by transforming the baseband signal with a tanh-1 transformation function, by modulating a carrier signal with a quadrature sum of two exponential signals related to the inverse hyperbolic tangent signal, and by hard limiting and filtering the modulated signal.
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Citations
10 Claims
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1. A phase modulator responsive to an input signal and to a carrier signal comprising:
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first means for developing a signal proportional to the inverse hyperbolic tangent of said input signal; second means, responsive to said first means and to said carrier signal for generating a signal which is proportional to a sum of two signals that are exponentially related to the output signal of said first means and which is amplitude modulated with said carrier signal; and third means for hard limiting the output signal of said second means.
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2. A circuit for generating phase modulated signals responsive to a modulating input signal and to a carrier signal comprising:
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first means for developing a signal proportional to the inverse hyperbolic tangent of said input signal; second means, responsive to said first means and to said carrier signal, for generating a signal proportional to said carrier signal and to a sum of two signals which are exponentially related to the output signal of said first means; third means for hard limiting the output signal of said second means; and fourth means for filtering the output signal of said third means. - View Dependent Claims (3, 4, 5, 6, 7, 8)
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9. A circuit for developing two signals which are phase modulated with respect to a carrier signal with equal but oppositely signed phase angles relating to the arc-cosine of an input signal comprising:
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an inverse hyperbolic tangent circuit responsive to said input signal for developing a signal proportional to tanh-1 of said input signal; a differential amplifier stage, responsive to the output signal of said inverse hyperbolic tangent circuit and to a carrier signal, for generating a first output signal proportional to said carrier signal and to an exponential term related to the output signal of said inverse hyperbolic tangent circuit, and for generating a second output signal proportional to said carrier signal and to an exponential term related to the negative of the output signal of said inverse hyperbolic tangent circuit; first quadrature summation stage for developing a sum signal of said first output signal of said differential stage and a 90°
phase shifted replica of said second output of said differential amplifier stage;a second quadrature summation stage developing a sum signal of said second output signal of said differential amplifier stage and a 90°
phase shifted replica of said first output signal of said differential amplifier stage;means for hard limiting the output signals of said first and second quadrature summation stages; and means for filtering the output signals of said means for hard limiting. - View Dependent Claims (10)
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Specification