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Recently, as result of improvements in Digital Signal
Processing (DSP) and Digital-to-Analog (D/A) conversion
technology, the analog sine wave can be generated by passing
the output of the digital sine wave through a Digital-to-Analog
Converter (DAC) and Low-Pass Filter (LPF). There are several
ways to achieve the goal. For example: Direct Digital Frequency
Synthesis Techniques (DDFS) and Loss-less Discrete Integrator
(LDI) biquad filter. But the hardware needed may be too large
to be acceptable in some
applications.
Therefore, this thesis finishes an analog oscillator using
oversampling D/A conversion techniques with small area and high
resolution. The oscillator structure is based on the digital
resonator which comes from LDI biquad circuit. The sine wave
can be acquired by passing the digital signals through
oversampling sigma-delta modulator D/A converter and LPF. By
setting the entire circuits to operate at the oversampled rate
and moving the delta-sigma modulator inside the resonator loop,
an efficient
implementation of the circuit can be accomplished. Besides, the
circuit has high resolution and it provides accurate control
over the oscillation frequency and amplitude. The sine wave
generated is quite neat. Both the simulation and experiments
prove the correction and reliability. The circuit is also
suitable for low frequency operation.
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