emadi
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by Denis Daly
Abstract
A constant-envelope, continuous phase modulation architecture is presented in
which a sigma-delta modulator is combined with a direct modulator.
The main advantages of this architecture are that linearity of the oscillator s tuning device is ensured and implementation is simplified due to the use of discrete frequency switching in the oscillator.
The main disadvantage is that the quantization noise introduced by the S- modulator must be filtered out or spread out to ensure wireless noise specifications are met.
The architecture is simulated in an open-loop configuration implementing GMSK modulation for use in a GSM transceiver. A prototype, low-frequency implementation of the modulation architecture is constructed and experimental results are found to match simulations. By increasing the S- modulation frequency, the quantization noise is filtered out by the VCO and disappears beneath the measurement noise floor.
Abstract
A constant-envelope, continuous phase modulation architecture is presented in
which a sigma-delta modulator is combined with a direct modulator.
The main advantages of this architecture are that linearity of the oscillator s tuning device is ensured and implementation is simplified due to the use of discrete frequency switching in the oscillator.
The main disadvantage is that the quantization noise introduced by the S- modulator must be filtered out or spread out to ensure wireless noise specifications are met.
The architecture is simulated in an open-loop configuration implementing GMSK modulation for use in a GSM transceiver. A prototype, low-frequency implementation of the modulation architecture is constructed and experimental results are found to match simulations. By increasing the S- modulation frequency, the quantization noise is filtered out by the VCO and disappears beneath the measurement noise floor.
