Cirrus Logic Inc.

Marjorie R Plisch

John L Melanson

Stephen Timothy Hodapp

Giri N K Rangan

A signal processing system utilizes chopping modulation technology to remove 1/f and other baseband noise from a baseband of a signal of interest. Chopping modulation and demodulation circuitry use direct and cross-over switches to modulate low frequency noise, such as 1/f noise, out of a signal baseband. Chopping circuits are particularly useful with low frequency baseband applications such as audio applications. In one embodiment, the direct switches coupled to respective input and output terminals of a differential amplifier have nonoverlapping conduction phases with cross-over switches coupled to the terminals of the differential amplifier. Additionally, the direct switches coupled to the respective input and output terminals have different duty cycles with respect to each other, and the cross-over switches coupled to the respective input and output terminals of the differential amplifier have different duty cycles with respect to each other to reduce noise transfer to an output of the system.

Signal processing system with baseband noise modulation chopper circuit timing to reduce noise

A digital-to-analog converter ('DAC') system utilizes chopping modulation technology to remove 1/f and other baseband noise from a baseband of a signal of interest. Chopping modulation and demodulation circuitry of the DAC operate at a chopping frequency equal to approximately one-half of a digital input signal sampling frequency. Chopping at one-half the sampling frequency allows fold back into the baseband of the input signal's frequency components and reduces fold back of noise, such as quantization noise, residing outside the baseband. In a further embodiment, a notch filter attenuates signals having frequencies around the chopping frequency prior to chopping to reduce fold back of noise into the baseband due to parasitic modulation. Coordination of chopping timing also reduces noises in the output of the DAC system.

Growing community of inventors

Austin, TX, United States of America

Marjorie R Plisch