Photoacoustic gas sensors with improved signal-to-noise ratio
AssigneeInvenSense, Inc.
InventorsJeremy Parker, Nishit Goel, Stephen Bart
Life of this patent
Estimating the term…
Abstract
A bi-directional photoacoustic gas sensor includes a first photoacoustic cell, where an electromagnetic radiation source emits radiation to interact with an external gas and generate pressure waves that are detected by a MEMS diaphragm. A second photoacoustic cell has an interior volume and acoustic compliance that corresponds to the interior volume and acoustic compliance of the first photoacoustic cell. Processing circuitry within a substrate uses a first acoustic signal, received by the first photoacoustic cell, and a second acoustic signal, received by the second photoacoustic cell, to determine a bi-directional response of the gas sensor to remove noise and improve the sensor's signal-to-noise ratio.
Claims21
A system for improving signal-to-noise ratio in a photoacoustic gas sensor, comprising:
- a first MEMS diaphragm;
- an electromagnetic radiation source configured to generate a photoacoustic signal from a gas of interest;
- a first photoacoustic cell defining a first volume, wherein the first MEMS diaphragm and the electromagnetic radiation source are located within the first volume, and wherein the first photoacoustic cell includes a first port configured to receive an external gas in the first volume;
- a first acoustic signal path, via the first port, to the first MEMS diaphragm;
- a second MEMS diaphragm;
- a second photoacoustic cell defining a second volume, wherein the second MEMS diaphragm is located within the second volume, wherein the second photoacoustic cell includes a second port to expose the second volume to an external environment;
- a second acoustic signal path, via the at least one port of the at least one photoacoustic cell, to the second MEMS diaphragm, wherein the first MEMS diaphragm receives a far-field acoustic noise signal via the first acoustic signal path and the first port and the second MEMS diaphragm receives the far-field acoustic noise signal via the second acoustic signal path, and wherein the first port and the second port are oriented at 180 degrees such that the first MEMS diaphragm has a first sensitivity to a far-field acoustic noise signal and the second MEMS diaphragm has a second sensitivity to the far-field acoustic noise signal;
- and
- processing circuitry configured to:
- receive a first signal from the first MEMS diaphragm based on the photoacoustic signal and the received far-field acoustic noise signal;
- receive a second signal from the second MEMS diaphragm based on the received far-field acoustic noise signal;
- scale the second signal based on the first sensitivity and the second sensitivity;
- and
- determine a bi-directional response based on the first signal and the scaled second signal, wherein noise of an output signal corresponding to a concentration of a gas of interest is reduced based on the bi-directional response.
Dependencies are inferred from the claim text.