Receiver for phase shift modulated carrier signals
First Claim
1. Apparatus for providing a local oscillator signal with a frequency which is at all times equal to a constant multiple of the frequency of a reference waveform, comprising:
- means, responsive to said reference waveform, for providing an interrupt signal upon the occurrence of a predetermined point in each cycle of said reference; and
digital processing means for providing said local oscillator signal, said digital processing means being responsive to said interrupt signal for determining the number of pulses of said local oscillator signal provided during one cycle of said reference waveform and for modulating the frequency of said local oscillator such that the number of local oscillator pulses provided during one cycle of said reference waveform is maintained to substantially equal said constant, said digital processing means comprising a microprocessor adapted to provide said local oscillator signal, and responsive to said interrupt signal for determining the number of local oscillator pulses provided during one cycle of said reference and for modulating the number of local oscillator pulses provided to maintain this number to substantially equal said constant.
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Accused Products
Abstract
Method and apparatus are disclosed for providing a local oscillator signal which is in phase and frequency synchronism with a carrier signal wherein the frequency of the carrier is a constant multiple of the frequency of a reference waveform. A phase detector detects the phase of the local oscillator relative to the carrier and provides a signal to a microprocessor indicative of this phase. The microprocessor provides the local oscillator and responds to a reference waveform threshold detector to determine the number of local oscillator pulses provided during one cycle of the reference and to maintain this number to equal the constant multiple. The microprocessor further responds to the phase detector to adjust the phase of the local oscillator and thereby maintain phase synchronism with the carrier.
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Citations
9 Claims
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1. Apparatus for providing a local oscillator signal with a frequency which is at all times equal to a constant multiple of the frequency of a reference waveform, comprising:
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means, responsive to said reference waveform, for providing an interrupt signal upon the occurrence of a predetermined point in each cycle of said reference; and digital processing means for providing said local oscillator signal, said digital processing means being responsive to said interrupt signal for determining the number of pulses of said local oscillator signal provided during one cycle of said reference waveform and for modulating the frequency of said local oscillator such that the number of local oscillator pulses provided during one cycle of said reference waveform is maintained to substantially equal said constant, said digital processing means comprising a microprocessor adapted to provide said local oscillator signal, and responsive to said interrupt signal for determining the number of local oscillator pulses provided during one cycle of said reference and for modulating the number of local oscillator pulses provided to maintain this number to substantially equal said constant. - View Dependent Claims (2, 3)
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4. Apparatus for synchronizing a local oscillator signal to the phase and frequency of a carrier signal wherein the instantaneous frequency of said carrier is a constant first multiple of the instantaneous frequency of a reference waveform, said apparatus comprising:
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means, responsive to said reference waveform, for providing an interrupt signal upon the occurrence of a predetermined point in each cycle of said waveform; means for detecting the phase of said local oscillator relative to said carrier; and digital processing means, responsive to said interrupt means, for providing said local oscillator signal and for maintaining the frequency of said local oscillator signal to be a constant multiple of the frequency of said reference by determining the number of local oscillator pulses provided between occurrences of said interrupt signal and maintaining this number to substantially equal said constant, said digital processing means also being responsive to said detector means to determine whether said oscillator signal leads or lags said carrier and, thereafter, to advance a lagging local oscillator and retard a leading local oscillator. - View Dependent Claims (5, 6, 7)
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8. A method for providing a local oscillator signal which is in phase and frequency synchronism with a carrier signal, wherein the frequency of said carrier signal is a first multiple of the frequency of a reference waveform, and wherein said reference waveform is known to have a lower limit frequency giving rise to a lower limit carrier frequency, said method comprising the steps of:
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(a) providing a first oscillating signal of frequency equal to a second multiple of said lower limit carrier frequency; (b) adding a number of servo pulses to said first oscillating signal to provide a composite signal; (c) dividing the frequency of said composite signal by said second multiple to provide said local oscillator signal; (d) periodically determining the number of said composite signal pulses during each cycle of said reference waveform; (e) modulating the number of said servo pulses to be added to said first oscillating signal based on determination of step (d) such that the number of composite signal pulses provided during each cycle of said reference is regulated to equal the arithmetic sum of said first multiple and said second multiple; (f) periodically determining whether said local oscillator leads said carrier signal and, if so, inhibiting one said servo pulse from being added to said first oscillating signal; and (g) periodically determining whether said local oscillator lags said carrier signal and, if so, adding one additional said servo pulses to said first oscillating signal. - View Dependent Claims (9)
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Specification