Signal Procesing Systems and Methods Using Basis Functions and Wavelet Transforms

Abstract

According to embodiments, systems and methods are provided that use continuous wavelet transforms and basis functions to provide an optimized system for the determination of physiological information. In an embodiment, the basis functions may be used to refine an area of interest in the signal in frequency or in time, and the continuous wavelet transform may be used to identify a maxima ridge in the scalogram at scales with characteristic frequencies proximal to the frequency or frequencies of interest. In another embodiment, a wavelet transform may be used to identify regions of a signal with the morphology of interest while basis functions may be used to focus on these regions to determine or filter information of interest. In yet another embodiment, basis functions and continuous wavelet transforms may be used concurrently and their results combined to form optimized information or a confidence metric for determined physiological information.

1 . A system for determining physiological information comprising:
 a processor configured to:
 receive a signal; 
 select an area of interest in the received signal; 
 perform a wavelet transform of the signal for a plurality of scales selected based at least in part on the area of interest; 
 use a basis function to generate information about the signal based at least in part on the information generated using the wavelet transform; and 
 determine the physiological information based at least in part on the basis function. 
   
     
     
         2 . The system of  claim 1 , wherein the area of interest is a window in frequency about a maxima ridge in the signal proximal to an estimate of a pulse rate. 
     
     
         3 . The system of  claim 1 , wherein the processor is further configured to determine an optimized piece of physiological information based at least in part on the information generated by the basis functions and the wavelet transform. 
     
     
         4 . The system of  claim 3 , wherein the processor is further configured to calculate a confidence measure based on a difference between the information generated by the basis function and the wavelet transform. 
     
     
         5 . The system of  claim 1 , wherein the processor is further configured to:
 generate a basis function subset based at least in part on the expected range of frequencies of a pulse rate signal; and   generate cancellation components based at least in part on the basis function subset.   
     
     
         6 . The system of  claim 5 , wherein the processor is further configured to generate basis function components according to the inner product of the original signal and each basis function of the basis function subset. 
     
     
         7 . The system of  claim 5 , wherein the processor is further configured to perform an iterative cancellation process using the cancellation components and the signal to generate a plurality of remainder signals. 
     
     
         8 . The system of  claim 7 , wherein the processor is further configured to analyze the plurality of remainder signals to generate a basis function index. 
     
     
         9 . The system of  claim 8 , wherein the processor is further configured to:
 generate a basis function waveform based at least in part on the basis function index; and   select a component of interest based at least in part on the basis function waveform.   
     
     
         10 . The system of  claim 9 , wherein the physiological information is determined based at least in part on the selected component. 
     
     
         11 . A non-transitory computer-readable medium for use in determining physiological information, the non-transitory computer readable medium having computer program instructions recorded thereon for:
 receiving a signal;   selecting an area of interest in the signal;   performing a wavelet transform of the signal for a plurality of scales selected based at least in part on the area of interest;   using a basis function to generate information about the signal based at least in part on the information generated using the wavelet transform; and   determining the physiological information based at least in part on the basis function.   
     
     
         12 . The non-transitory computer readable medium of  claim 11 , wherein the area of interest is a window in frequency about a maxima ridge in the signal proximal to an estimate of a pulse rate. 
     
     
         13 . The non-transitory computer readable medium of  claim 11 , further comprising instructions for determining an optimized piece of physiological information based at least in part on the information generated by the basis functions and the wavelet transform. 
     
     
         14 . The non-transitory computer readable medium of  claim 13 , further comprising instructions for calculating a confidence measure based on a difference between the information generated by the basis function and the wavelet transform. 
     
     
         15 . The non-transitory computer readable medium of  claim 11 , wherein instructions for using a plurality of basis functions to generate information about the signal further comprises instructions for:
 generating, using processing equipment, a basis function subset based at least in part on the expected range of frequencies of a pulse rate signal; and   generating, using processing equipment, cancellation components based at least in part on the basis function subset.   
     
     
         16 . The non-transitory computer readable medium of  claim 15 , further comprising instructions for generating, using processing equipment, basis function components according to the inner product of the original signal and each basis function of the basis function subset. 
     
     
         17 . The non-transitory computer readable medium of  claim 15 , further comprising instructions for performing, using processing equipment, an iterative cancellation process using the cancellation components and the signal to generate a plurality of remainder signals. 
     
     
         18 . The non-transitory computer readable medium of  claim 17 , further comprising instructions for analyzing, using processing equipment, the plurality of remainder signals to generate a basis function index. 
     
     
         19 . The non-transitory computer readable medium of  claim 18 , further comprising instructions for:
 generating, using processing equipment, a basis function waveform based at least in part on the basis function index; and   selecting, using processing equipment, a component of interest based at least in part on the basis function waveform.   
     
     
         20 . The non-transitory computer readable medium of  claim 19 , wherein the physiological information is determined based at least in part on the selected component.