Interference detection systems and methods

Abstract

Methods and systems for detecting interference in a signal are described. More specifically, in one aspect, a method for detecting interference in a signal is provided. The method comprises determining whether the signal has at least one of a time and a frequency characteristic that is outside a predefined range, and determining that an interference event has been detected if the signal has at least one of such characteristics.

1 . Apparatus for determining whether a signal representative of breath alcohol generated by a sensor has been corrupted by interference, said apparatus comprising a processor that processes the signal from the sensor to determine whether the signal generated by the sensor has been corrupted by interference, said processor programmed to determine whether the sensor signal has at least one of a time characteristic and a frequency characteristic outside respective predefined ranges.  
     
     
         2 . Apparatus in accordance with  claim 1  wherein said processor is further programmed to detect an interference event if the signal has at least one of a time and a frequency characteristic outside the predefined range.  
     
     
         3 . Apparatus in accordance with  claim 1  further comprising a high-pass filter for filtering the signal generated by the sensor, said processor is further programmed to determine whether the signal generated by the sensor has been corrupted by interference based on the high pass filtered signal.  
     
     
         4 . Apparatus in accordance with  claim 3  wherein said processor is further programmed to compare the high pass filtered signal to a predefined threshold.  
     
     
         5 . Apparatus in accordance with  claim 1  wherein the signal generated by the sensor is differentiated, said processor programmed to determine whether the signal generated by the sensor has been corrupted by interference based on the differentiated signal.  
     
     
         6 . Apparatus in accordance with  claim 5  wherein said processor is further programmed to compare the differentiated signal to a predefined threshold.  
     
     
         7 . Apparatus in accordance with  claim 1  wherein the signal generated by the sensor is transformed from a time domain signal to a frequency domain signal, said processor is programmed to determine whether the signal generated by the sensor has been corrupted by interference using the frequency domain signal.  
     
     
         8 . Apparatus in accordance with  claim 7  wherein said processor is further programmed to determine whether an interference event has occurred based on frequency components outside a pre-defined range.  
     
     
         9 . Apparatus in accordance with  claim 1  further comprising: 
 an amplifier configured to couple to the sensor for amplifying the signal generated by the sensor; and    a first analog-to-digital converter coupled to said processor for converting an analog signal from said amplifier to a digital signal.    
     
     
         10 . Apparatus in accordance with  claim 9  further comprising a high-pass filter coupled to said amplifier, and a second analog-to-digital converter coupled to said second converter for converting an analog signal from said filter to a digital signal, said high-pass filter and said second converter connected in parallel with said first converter.  
     
     
         11 . Apparatus in accordance with  claim 10  further comprising a high-pass filter coupled to said amplifier, and a comparator coupled to said filter, said processor coupled to said comparator.  
     
     
         12 . Apparatus in accordance with  claim 11  wherein said comparator and said high pass filter are connected in parallel with said first converter.  
     
     
         13 . Apparatus in accordance with  claim 1  wherein said processor determines a second order or higher order derivative of the signal in determining whether the signal has been corrupted by interference.  
     
     
         14 . A method for detecting interference in a signal that is representative of breath alcohol content, said method comprising: 
 determining whether the signal has at least one of a time and a frequency characteristic outside a predefined range; and    determining that an interference event has been detected if the signal has at least one of such characteristics.    
     
     
         15 . A method in accordance with  claim 14  further comprising: 
 filtering the signal using a high-pass filter; and    comparing the high-pass filtered signal to a pre-defined threshold.    
     
     
         16 . A method in accordance with  claim 14  further comprising 
 differentiating the signal; and    comparing the differentiated signal to a pre-defined threshold.    
     
     
         17 . A method in accordance with  claim 14  further comprising 
 transforming the signal from a time domain signal to a frequency domain signal; and    processing the frequency domain signal to determine whether any frequency component present is outside a pre-defined range.    
     
     
         18 . A method in accordance with  claim 14  wherein determining whether the signal has at least one of a time and a frequency characteristic further comprises determining whether a signal representative of breath alcohol content has at least one of a time and frequency characteristic that is outside a predefined range.  
     
     
         19 . A method in accordance with  claim 14  wherein determining whether the signal has at least one of a time and a frequency characteristic further comprises determining whether a signal representative of at least one of ethanol content, CO 2  content, temperature, pressure, breath flow, and position has at least one of a time and frequency characteristic that is outside a predefined range.  
     
     
         20 . A method in accordance with  claim 14  further comprising determining a second order or higher order derivative of the signal.  
     
     
         21 . An interference detector for detecting interference in a signal, said detector comprising a processor programmed to: 
 process a signal representative of breath alcohol content to determine whether the signal has been corrupted by interference; and    determine whether the signal has at least one of a time characteristic and a frequency characteristic outside respective predefined ranges.    
     
     
         22 . A detector in accordance with  claim 21  further comprising: 
 an amplifier coupled to said processor for amplifying the signal representative of breath alcohol content; and    a first analog-to-digital converter for converting an analog signal from said amplifier to a digital signal.    
     
     
         23 . A detector in accordance with  claim 22  further comprising: 
 a high pass filter coupled to said amplifier; and    a second analog-to-digital converter for converting an analog signal from said filter to a digital signal, said high pass filter and second converter are connected in parallel with said first converter.    
     
     
         24 . A detector in accordance with  claim 22  wherein at least one of said first converter and said second converter is coupled to said processor.  
     
     
         25 . A detector in accordance with  claim 20  further comprising: 
 a high-pass filter coupled to said amplifier; and    a comparator coupled to said high-pass filter, said high-pass filter and said comparator are connected in parallel with said first converter, said processor is coupled to said comparator.    
     
     
         26 . A detector in accordance with  claim 25  wherein said processor is programmed to determine whether the signal representative of breath alcohol content has been corrupted by interference based on a signal received from said high-pass filter.  
     
     
         27 . A detector in accordance with  claim 21  wherein signals representative of breath alcohol content are differentiated, said processor is programmed to determine whether the signal generated by said sensor has been corrupted by interference based on the differentiated signal.  
     
     
         28 . A detector in accordance with  claim 21  wherein said processor is further programmed to determine whether the signal has been corrupted by electro-magnetic interference.  
     
     
         29 . A detector in accordance with  claim 21  wherein said processor is programmed to determine a second order or higher order derivative of the signal in determining whether the signal has been corrupted by interference.