Sensor signal multiplexer and digitizer with analog notch filter and optimized sample frequency
The described technology is generally directed towards a sensor signal multiplexer and digitizer with analog notch filter and optimized sample frequency, and corresponding methods of use and manufacture. In some examples, the disclosed technologies can be used to reduce vibration sensitivity of an inertial measurement unit (IMU). The disclosed sensor signal multiplexer can sample sensor inputs on multiple input channels at a first, higher frequency, and integrate samples for each channel in order to generate lower frequency sensor outputs. The lower frequency sensor outputs can be converted to digital form.
1 . A sensor signal path, comprising:
a multiplexer configured to operate at a first operating frequency and receive a plurality of sensor signals at a first sample frequency, wherein the multiplexer generates a multiplexed output;
a demultiplexer configured to demultiplex the multiplexed output, resulting in a plurality of demultiplexed sensor signals;
a plurality of integrators comprising a total number of integrators that is less than or equal to a total number of sensor signals of the plurality of sensor signals, wherein the plurality of integrators is configured to accumulate samples of the plurality of demultiplexed sensor signals, and to generate integrated outputs; and
an analog to digital converter configured to operate at a second operating frequency and generate a digital signal based on samples of the integrated outputs of the plurality of integrators, wherein the second operating frequency is lower than the first operating frequency, wherein the digital signal comprises a second sample frequency that is lower than the first sample frequency, wherein the second sample frequency is equal to the first sample frequency divided by a number of samples accumulated by an integrator of the plurality of integrators prior to resetting the integrator,
wherein the plurality of integrators and the analog to digital converter are configured to operate at the second operating frequency, wherein each of the plurality of integrators comprises a notch filter, wherein a notch frequency of the notch filter is a function of the second sample frequency divided by a number of output channels associated with the analog to digital converter, and wherein the number of output channels is at least two.
2 . The sensor signal path of claim 1 , wherein the demultiplexer is a first demultiplexer, and wherein the sensor signal path further comprises a second demultiplexer configured to sample the digital signal and output the digital signal via separate output channels, wherein each of the separate output channels corresponds to a sensor signal of the plurality of sensor signals.
3 . The sensor signal path of claim 1 , further comprising an amplifier coupled between the multiplexer and the demultiplexer, wherein the amplifier is configured to amplify the multiplexed output.
4 . The sensor signal path of claim 1 , wherein demultiplexer is a first demultiplexer, and wherein the sensor signal path further comprises a second multiplexer coupled between the plurality of integrators and the analog to digital converter, wherein the second multiplexer is configured to multiplex the integrated outputs of the plurality of integrators.
5 . The sensor signal path of claim 1 , wherein the multiplexer and the demultiplexer are configured to operate at the first operating frequency.
6 . The sensor signal path of claim 1 , wherein the notch frequency of the notch filter facilitates reducing vibration sensitivity of a sensor associated with the sensor signal path.
7 . The sensor signal path of claim 1 , wherein each respective integrator of the plurality of integrators is configured to reset after accumulating the number of the samples.
8 . The sensor signal path of claim 1 , wherein the plurality of sensor signals are generated by a plurality of sensors, and wherein the plurality of sensors comprises a number of sensors that is more than the total number of integrators.
9 . A method to process sensor signals, comprising:
receiving, by a multiplexer operating at a first operating frequency, a plurality of sensor signals, wherein each respective sensor signal of the plurality of sensor signals comprises a first sampling frequency;
accumulating respective samples from each respective sensor signal of the plurality of sensor signals;
integrating accumulated respective samples of each respective sensor signal, resulting in respective integrated outputs, wherein the respective integrated outputs comprise a second sampling frequency that is lower than the first sampling frequency; and
converting, by an analog to digital converter operating at a second operating frequency, the respective integrated outputs to a digital format to generate respective digital output data that is output via respective output channels,
wherein the second operating frequency is lower than the first operating frequency, wherein each output channel of the respective output channels is associated with a notch filter, wherein a notch frequency of the notch filter is a function of the first sampling frequency, a number of the respective samples accumulated from one of the respective sensor signals, based on the accumulating, prior to an integration reset, and a number of the respective output channels, and wherein the number of the respective output channels is at least two.
10 . The method to process sensor signals of claim 9 , further comprising sampling the plurality of sensor signals at the first sampling frequency, resulting in sensor output samples.
11 . The method to process sensor signals of claim 10 , wherein the sampling of the plurality of sensor signals comprises round-robin sampling of the plurality of sensor signals.
12 . The method to process sensor signals of claim 10 , further comprising multiplexing the plurality of sensor signals, resulting in a multiplexed sensor output.
13 . The method to process sensor signals of claim 12 , further comprising amplifying the multiplexed sensor output, resulting in an amplified multiplexed sensor output.
14 . The method to process sensor signals of claim 13 , further comprising demultiplexing the amplified multiplexed sensor output, resulting in multiple component amplified sensor outputs, and wherein the accumulating of the respective samples from each respective sensor signal of the plurality of sensor signals comprises accumulating the respective samples from the multiple component amplified sensor outputs.
15 . The method to process sensor signals of claim 9 , further comprising multiplexing the respective integrated outputs, resulting in a multiplexed integrated sensor output, and wherein the converting of the respective integrated outputs to the digital format comprises converting the multiplexed integrated sensor output to the digital format.
16 . The method to process sensor signals of claim 15 , further comprising demultiplexing the multiplexed integrated sensor output after the converting of the multiplexed integrated sensor output to the digital format, resulting in multiple component digital integrated sensor outputs that comprises the respective digital output data.
17 . The method to process sensor signals of claim 9 , wherein the plurality of sensor signals are received from microelectromechanical system (MEMS) sensors.
18 . The method to process sensor signals of claim 9 , wherein the notch frequency of the notch filter facilitates reducing vibration sensitivity of a sensor associated with the sensor signals.