Self-synchronization circuit for a FFSK or MSK demodulator
First Claim
1. In a demodulating receiver, a self-synchronization circuit for generating a carrier reference signal from an incoming Fast FSK or MSK signal comrising:
- first means for splitting the incoming signal into two circuit paths;
second means for frequency shifting the incoming signal in each circuit path by a frequency signal substantially equal to the carrier frequency to provide an in-phase signal along one circuit path and a quadrature phase signal along the other circuit path, the frequency shifting means having an oscillator circuit controllable in frequency and phase;
first multiplier means for multiplying the in-phase and quadrature signals;
clock recovery circuit means for determining the clock frequency from the output of the first multiplier means; and
second multiplier means for multiplying the output of the first multiplier means and the clock recovery circuit means for providing a carrier phase signal to the controllable oscillator circuit.
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Accused Products
Abstract
The self-synchronization circuit splits the incoming signal into two circuit paths where the signals are frequency shifted by a frequency signal equal to the carrier frequency so as to provide an in-phase signal in one circuit path and a quadrature signal in the other circuit path. The frequency shifting circuit includes at least a controllable oscillator. The output of a first multiplier which multiplies the in-phase and quadrature signals, is fed to a clock recovery circuit which determines the clock frequency. A second multiplier multiplies the output of the first multiplier with the clock recovery circuit output to provide a signal which controls the controllable oscillator. In addition, a frequency discriminator utilizes the in-phase and quadrature signals to initially coarse control the controllable oscillator frequency. The frequency shifting signals may be obtained from the controllable oscillator feeding phase shifting circuits, or they may be obtained from a combined circuit including a fixed oscillator with phase shifting circuits together with the controllable oscillator and appropriate mixing circuits.
125 Citations
4 Claims
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1. In a demodulating receiver, a self-synchronization circuit for generating a carrier reference signal from an incoming Fast FSK or MSK signal comrising:
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first means for splitting the incoming signal into two circuit paths; second means for frequency shifting the incoming signal in each circuit path by a frequency signal substantially equal to the carrier frequency to provide an in-phase signal along one circuit path and a quadrature phase signal along the other circuit path, the frequency shifting means having an oscillator circuit controllable in frequency and phase; first multiplier means for multiplying the in-phase and quadrature signals; clock recovery circuit means for determining the clock frequency from the output of the first multiplier means; and second multiplier means for multiplying the output of the first multiplier means and the clock recovery circuit means for providing a carrier phase signal to the controllable oscillator circuit. - View Dependent Claims (2, 3, 4)
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Specification