Cirrus Logic Inc.

Cirrus Logic International Semiconductor Limited

Emmanuel Philippe Christian Hardy

John Paul Lesso

Toru Ido

James Thomas Deas

This application describes a noise reduction apparatus () for a microphone device () having an acoustic port (). The apparatus has a spectrum peak detect block () for receiving a microphone signal (S) and determining, from the microphone signal, at least one characteristic of a resonance peak () associated with the acoustic port of the microphone. The at least one characteristic may comprise a resonance frequency (f) and/or quality factor (Q). A noise reduction block () is configured to process the microphone signal based on the resonance characteristic so as to reduce noise in the processed microphone signal due to said resonance. The noise reduction block may apply a function which is the inverse of the determined resonance characteristic.

Apparatus and methods for monitoring a microphone

This application describes an apparatus () for monitoring for blockage of an acoustic () port of a microphone device (). The apparatus has a spectrum peak detect block () for receiving a microphone signal (S) and determining, from the microphone signal, a resonance frequency (f) and a quality factor (Q) of a resonance () associated with the acoustic port. A condition monitoring block () is configured to determine any change in resonance frequency and quality factor and to determine a blockage status for the microphone based on said detect changes. The condition monitoring block identifies a change in blockage status if there is a change in quality factor.

This application relates to an apparatus () for monitoring an operating temperature condition of a microphone device () having an acoustic port (). The apparatus includes a spectrum peak detect block () for receiving a microphone signal (S) and determining, from the microphone signal, a resonance frequency (f) and a quality factor (Q) of a resonance () associated with the acoustic port of the microphone. A condition monitoring block () is configured to determine any change in resonance frequency and quality factor with respect to respective reference values of resonance frequency and quality factor and to determine a temperature condition for the air temperature within the acoustic port based on said determined changes.

This application relates to audio amplifier circuitry (). An amplifier module () is located in a signal path between an input () and an output (). A detection module () is configured to detect a characteristic of a load () electrically coupled, in use, to the output. A distortion setting controller () is provided for selecting one of a plurality of stored distortion settings {p} based on the detected characteristic of the load; and a pre-distortion module () is configured to apply a first transfer function to a signal in the signal path prior to said amplifier module. The first transfer function is based on the selected distortion setting and for at least one of the stored distortion settings the corresponding first transfer function comprises a non-linear distortion function.

Amplifiers

This application relates to circuitry for processing sense signals generated by MEMS capacitive transducers for compensating for distortion in such sense signals. The circuitry has a signal path between an input () for receiving the sense signal and an output () for outputting an output signal based on said sense signal. Compensation circuitry () is configured to monitor the signal at a first point along the signal path and generate a correction signal (Scorr); and modify the signal at at least a second point along said signal path based on said correction signal. The correction signal is generated as a function of the value of the signal at the first point along the signal path so as to introduce compensation components into the output signal that compensate for distortion components in the sense signal. The first point in the signal path may be before or after the second point in the signal path. The monitoring may be performed in an analogue or a digital part of the signal path and in either case the modification may be applied in an analogue or a digital part of the signal path.

Signal processing for MEMS capacitive transducers

This application relates to analog-to-digital converters (ADCs). An ADChas a first converter () for receiving an analog input signal (AIN) and outputting a time encode signal (DT), such as a pulse-width-modulated (PWM) signal, based on input signal and a first conversion gain setting (GIN). In some embodiments the first converter has a PWM modulator () for generating a PWM signal such that the input signal is encoded by pulse widths that can vary continuously in time. A second converter () receives the time encoded signal and outputs a digital output signal (DOUT) based on the time encoded signal (DT) and a second conversion gain setting (GO). The second converter may have a first PWM-to-digital modulator (). A gain allocation block () generates the first and second conversion gain settings based on the time encoded signal (DT). The gain allocation block () may have a second PWM-to-digital modulator () which may be of lower latency and/or lower resolution that the first PWM-to-digital modulator ().

Analogue-to-digital converter

This application relates to analogue-to-digital converters (ADCs). An ADChas a first converter () for receiving an analogue input signal (AIN) and outputting a time encode signal (DT), such as a pulse-width-modulated (PWM) signal, based on input signal and a first conversion gain setting (GIN). In some embodiments the first converter has a PWM modulator () for generating a PWM signal such that the input signal is encoded by pulse widths that can vary continuously in time. A second converter () receives the time encoded signal and outputs a digital output signal (DOUT) based on the time encoded signal (DT) and a second conversion gain setting (GO). The second converter may have a first PWM-to-digital modulator (). A gain allocation block () generates the first and second conversion gain settings based on the time encoded signal (DT). The gain allocation block () may have a second PWM-to-digital modulator () which may be of lower latency and/or lower resolution that the first PWM-to-digital modulator ().

This application relates to circuitry for processing sense signals generated by MEMS capacitive transducers for compensating for distortion in such sense signals. The circuitry has a signal path between an input () for receiving the sense signal and an output () for outputting an output signal based on said sense signal. Compensation circuitry () is configured to monitor the signal at a first point along the signal path and generate a correction signal (S); and modify the signal at at least a second point along said signal path based on said correction signal. The correction signal is generated as a function of the value of the signal at the first point along the signal path so as to introduce compensation components into the output signal that compensate for distortion components in the sense signal. The first point in the signal path may be before or after the second point in the signal path. The monitoring may be performed in an analogue or a digital part of the signal path and in either case the modification may be applied in an analogue or a digital part of the signal path.

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Edinburgh, United Kingdom

Emmanuel Philippe Christian Hardy