VARIABLE SENSING USING FREQUENCY DOMAIN

• US 20120116698A1
• Filed: 11/11/2011
• Published: 05/10/2012
• Est. Priority Date: 11/14/2006
• Status: Active Grant

• Current Assignee: 2 Bit Incorporated
• Original Assignee: 2 Bit Incorporated
• Inventors: Lambert, Rodney J.
• Granted Patent: US 8,548,763 B2
• Time in Patent Office: Days
• US Class Current: 702/60
• CPC Class Codes: H03M 1/1042 the look-up table containing corrected values for replacing the original digital values H03M1/1052 takes precedence
• CPC Class Codes: H03M 1/122 Shared using a single converter or a part thereof for multiple channels, e.g. a residue amplifier for multiple stages

Abstract

Embodiments of a method and apparatus for variable sensing using the frequency domain are taught herein. An exposure of a system to a physical variable is determined by periodically sensing the physical variable to produce a plurality of digital samples. The plurality of digital samples is converted to respective frequency domain representations. The exposure is calculated using the frequency domain representations.

Claims

1-23. -23. (canceled)

24. An apparatus for monitoring a system exposed to a stimulus, the apparatus comprising:

a memory for storing data;

an input channel for sensory input;

a processor connected to the memory and the input channel, the processor programmed to;

receive the sensory input from the input channel as a sequential stream of data samples in a time domain wherein the sensory input is responsive to exposure of the system to the stimulus;

convert the sequential stream of data samples from the time domain to a frequency domain using a Fourier transform to obtain a plurality of complex Fourier coefficients at a respective frequency;

calculate an exposure of the system to the stimulus using magnitudes of at least some of the plurality of complex Fourier coefficients;

an output channel connected to the processor for transmitting an output of the processor external of the apparatus.

25. The apparatus of claim 24, further comprising:

a sensing element connected to the input channel.

26. The apparatus of claim 24 wherein the input channel includes amplification and anti-aliasing filters.

27. The apparatus of claim 24, further comprising:

a plurality of input channels for a respective sensory input related to the physical variable, wherein the input channel is one of the plurality of input channels.

28. The apparatus of claim 27 wherein the processor is programmed to:

use the exposure to trigger receipt of sensory input by a second one of the plurality of input channels.

29. The apparatus of claim 27 wherein the exposure of the system to the stimulus is a weighted value of outputs of each of the plurality of input channels.

30. The apparatus of claim 24 wherein the stimulus is other than an audio stimulus.

31. The apparatus of claim 24 wherein the processor is programmed to convert the sequential stream of data samples from the time domain to the frequency domain using the Fourier transform by:

assigning at least three windows for receiving the sequential stream of data samples, each of the windows having a same size;

sequentially filling a first window of the at least three windows with a first number of data samples corresponding to the size;

sequentially filling a second window of the at least three windows with a second number of data samples corresponding to the size, the second number of data samples including some of the first number of data samples at an end of the first number of data samples;

performing the Fourier transform on the first window while sequentially filling the second window;

sequentially filling a third window of the at least three windows with a third number of data samples corresponding to the size, the third number of data samples including some of the second number of data samples at an end of the second number of data samples;

performing the Fourier transform on the second window while sequentially filling the third window; and

performing the Fourier transform on the third window after sequentially filling the third window.

32. The apparatus of claim 31 wherein the processor is programmed to convert the sequential stream of data samples from the time domain to the frequency domain using the Fourier transform by:

applying a window function scalar to each of the first number of data samples, the second number of data samples and the third number of data samples based on a position of each within the first window, the second window or the third window.

33. The apparatus of claim 24, further comprising:

an analog-to-digital converter coupled between the input channel and the processor to digitize the sensory input to form the sequential stream of data samples.

34. The apparatus of claim 24, further comprising:

a digital-to-analog converter coupled to the output channel to convert the exposure to an analog output before transmitting the exposure external of the apparatus.

35. The apparatus of claim 24 wherein the sensory input responsive to the stimulus is one of acceleration, voltage or temperature.

36. The apparatus of claim 24 wherein the processor is configured to calculate the exposure by:

calculating a calibrated power magnitude for each of plurality of frequencies associated with each of the plurality of complex Fourier coefficients by multiplying a calibration scaler for a respective frequency with a square of a magnitude of a complex Fourier coefficient for the respective frequency; and

using each calibrate power magnitude to calculate the exposure.

37. The apparatus of claim 36 wherein the processor is configured to calculate a weighted power density spectrum as the exposure by:

scaling the calibrated power magnitude for each of the plurality of frequencies based on a relative impact that a respective frequency has on the system; and

summing the scaled, calibrated power magnitudes to obtain the weighted power density spectrum.

38. The apparatus of claim 37, further comprising:

correlating values of the weighted power density spectrum to a user-defined pattern via a correlation function.

39. The apparatus of claim 36 wherein the processor is configured to calculate the exposure by:

comparing the calibrated power magnitude at a first frequency to a threshold value;

generating an exposure value of one when the calibrated power magnitude at the first frequency is greater than or equal to the threshold value;

generating an exposure value of zero or a value of the calibrated power magnitude at the first frequency divided by the threshold value when the calibrated power magnitude at the first frequency is below the threshold value.

40. The apparatus of claim 36 wherein the processor is configured to calculate the exposure by:

comparing the calibrated power magnitude at a first frequency to an upper threshold value and a lower threshold value;

generating an exposure value of one when the calibrated power magnitude at the first frequency is greater than the upper threshold value or lower than the lower threshold value;

generating an exposure value of zero when the calibrated power magnitude at the first frequency greater than or equal to the lower threshold value and less than or equal to the upper threshold value.

41. A method of monitoring a system exposed to a stimulus, the method comprising:

receiving the sensory input from an input channel connected to a processor as a sequential stream of data samples in a time domain wherein the sensory input is responsive to exposure of the system to the stimulus;

using the processor to convert the sequential stream of data samples from the time domain to a frequency domain using a Fourier transform to obtain a plurality of complex Fourier coefficients at a respective frequency; and

calculating, using the processor, an exposure of the system to the stimulus using magnitudes of at least some of the plurality of complex Fourier coefficients.

42. The method of claim 41 wherein calculating the exposure comprises:

calculating a first exposure to a first frequency using a first magnitude of a complex Fourier coefficient at the first frequency;

calculating a second exposure to the first frequency using a second magnitude of the complex Fourier coefficient at the first frequency; and

calculating a recent exposure to the first frequency by adding the first exposure and the second exposure.

43. The method of claim 41, further comprising:

selectively storing the exposure in a memory connected to the processor based on a value of the exposure.