Radio Frequency System and Method for Monitoring Engine-Out Exhaust Constituents

Abstract

A radio frequency system and method for monitoring an engine-out exhaust emission constituent. The system comprises a housing containing the emission constituent, one or more radio frequency sensors extending into the housing and transmitting and receiving radio frequency signals, and a control unit for controlling the radio frequency signals and monitoring changes in the emission constituent based on changes in one or more parameters of the radio frequency signals. In one embodiment, the control unit measures a rate of change in one or more of the parameters of the radio frequency signals for monitoring a rate of change of the emission constituent including for example the emission rate, accumulation rate, and/or depletion rate of the emission constituent.

1 . A radio frequency system for monitoring an engine-out exhaust emission constituent comprising:
 a housing containing the emission constituent;   one or more radio frequency sensors extending into the housing and transmitting and receiving radio frequency signals; and   a control unit for controlling the radio frequency signals and monitoring changes in the emission constituent based on a measurement of a shift in at least the phase of the radio frequency signals.   
     
     
         2 . The radio frequency system of  claim 1 , wherein the radio frequency signals span a radio frequency signal range and the control unit measures the shift in the phase of the radio frequency signals in predefined regions of the radio frequency signal range. 
     
     
         3 . The radio frequency system of  claim 1 , wherein the control unit measures the shift in the phase of the radio frequency signals in one or more predefined radio frequency signal ranges corresponding to one or more predefined spatial regions in the housing. 
     
     
         4 . The radio frequency system of  claim 1 , wherein the control unit also measures changes in the magnitude or amplitude of the radio frequency signal. 
     
     
         5 . The radio frequency system of  claim 4 , wherein one or more emission constituents are monitored by measuring changes in the magnitude and the shift in the phase of the radio frequency signal in one or more predefined radio frequency signal ranges. 
     
     
         6 . The radio frequency system of  claim 1 , wherein the control unit measures a rate of the shift in at least the phase of the radio frequency signals for monitoring a rate of change of the emission constituent. 
     
     
         7 . The radio frequency system of  claim 1 , wherein the power transmitted to the one or more radio frequency sensors is varied to improve the radio frequency signals. 
     
     
         8 . The radio frequency system of  claim 6 , wherein the control unit monitors the emission rate, accumulation rate, and/or depletion rate of the emission constituent. 
     
     
         9 . A method for monitoring an emission constituent in a radio frequency system including a housing containing the emission constituent, one or more radio frequency sensors extending into the housing and transmitting and receiving radio frequency signals; and a control unit, the method comprising the step of controlling the radio frequency signals and monitoring changes in the emission constituent based on a measurement of a shift in at least the phase of the radio frequency signals. 
     
     
         10 . The method of  claim 9 , wherein the radio frequency signals span a radio frequency signal range and further comprising the step of measuring the shift in at least the phase of the radio frequency signals in predefined regions of the radio frequency signal range. 
     
     
         11 . The method of  claim 10 , further comprising the step of measuring the shift in at least the phase of the radio frequency signals in one or more predefined radio frequency signal ranges corresponding to one or more predefined spatial regions in the housing. 
     
     
         12 . The method of  claim 11 , wherein the predefined spatial regions correspond to predefined spatial regions sensitive to the phase of the radio frequency signal. 
     
     
         13 . The method of  claim 11 , wherein the predefined spatial regions correspond to predefined spatial regions exhibiting a favorable behavior for the phase of the radio frequency signal. 
     
     
         14 . The method of  claim 10 , further comprising the step of sampling the shift in at least the phase of the radio frequency signals in one or more predefined narrow radio frequency signal ranges to decrease the measurement response time. 
     
     
         15 . The method of  claim 14 , wherein the one or more predefined narrow radio frequency signal ranges correspond to one or more predefined resonant modes of the radio frequency signal. 
     
     
         16 . The method of  claim 9 , further comprising the step of measuring changes in the magnitude or amplitude of the radio frequency signal. 
     
     
         17 . The method of  claim 16 , wherein one or more emission constituents are monitored by measuring changes in the magnitude and phase of the radio frequency signal in one or more predefined radio frequency signal ranges. 
     
     
         18 . The method of  claim 9 , further comprising the step of measuring a rate of the shift in at least the phase of the radio frequency signals for monitoring a rate of change of the emission constituent. 
     
     
         19 . The method of  claim 9 , further comprising the step of comparing the rate of change of the emission constituent with expected values of the rate of change of the emission constituent. 
     
     
         20 . The method of  claim 10 , further comprising the step of monitoring the emission rate, accumulation rate, and/or depletion rate of the emission constituent.