A sigma-delta based open-loop frequency modulator

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.

• Type: Conference
• Year: 2003
• Where: ISCAS
• Authors: Denis Daly, Anthony Chan Carusone
• Keywords: ISCAS 2003, Modulation, Phase Modulation Architecture, Σ−∆ Modulation Frequency