High order 1-bit digital sigma delta modulation for on chip analogue signal sources

This paper presents a digital oscillator, based on the ΣΔ modulation principle, that can produce high quality analogue stimuli. With the exception of a front end analogue filter, the proposed circuit is entirely digital, providing accurate control over the oscillation frequency and amplitude. The oscillator is achieved by the use of a ΣΔ modulator in the digital resonator loop. A novel topology for constructing stable high order 1 bit modulators is described. 4^th order lowpass and 8^th order bandpass oscillators are implemented in a field programmable gate array prototype. The experimental results demonstrate stability and feasibility, achieving more than 110 dB dynamic range for the generated signals.