A sigma-delta based open-loop frequency modulator
نویسندگان
چکیده
A constant-envelope, continuous phase modulation architecture is presented in which a sigma-delta modulator is combined with an open-loop modulator. Compared to existing architectures, Σ∆ based open-loop modulation can be implemented with minimal analog circuitry. The architecture is demonstrated with a discrete implementation performing frequency modulation at a carrier frequency of 120 MHz. By increasing the Σ−∆ modulation frequency, the quantization noise is filtered out by the VCO and disappears beneath the measurement noise floor.
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