System and method for automatic thresholding of signals in the presence of Gaussian noise
AssigneeInternational Business Machines Corporation
InventorPhilip C. D. Hobbs
Life of this patent
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Abstract
A system and method for detecting information signals by automatically thresholding input signals in the presence of noise of accurately known statistics concerning a predetermined acceptable false alarm rate data. A first subcircuit including a comparator and a servo amplifier is used for setting and adjusting a threshold value signal based on the input signal and the statistics concerning a predetermined acceptable false alarm rate. A second comparator is used for comparing the threshold value signal to the input signal, and outputting a signal corresponding to the difference therebetween.
Claims10
A method for detecting information signals by automatically thresholding input signals in the presence of noise of accurately known statistics concerning a predetermined acceptable false alarm rate data, comprising the steps of:
- setting a first threshold value signal based on the input signal and the statistics concerning the predetermined acceptable false alarm rate;
- comparing the input signal to a second threshold signal related to the first, and outputting a second false alarm rate;
- determining the frequency of said second false alarm rate;
- adjusting said first threshold value signal based on the predetermined acceptable false alarm rate and said frequency of said second false alarm rate;
- setting said second threshold signal to cause said second false alarm rate to be substantially larger that said first false alarm rate;
- converting the frequency of said predetermined acceptable false alarm rate to a current signal using a frequency-to-current converter means;
- and
- generating an output corresponding to said adjusted first threshold value signal, based on a difference between said current signal and a predetermined current using a servo amplifier means.
A system for automatically thresholding an input signal in the presence of gaussian noise to detect actual input signal events, comprising:
- (a) a first comparator having a first input for receiving the input signal and a second input for receiving a first reference signal having a threshold value level, said first comparator outputting a first threshold crossing rate representing the actual input signal events and having a first false alarm rate, said first threshold crossing rate being the difference between the input signal and said threshold value level;
- (b) a second comparator having a first input for receiving the input signal and a second input for receiving a second reference signal, said second comparator outputting a second threshold crossing rate having a second false alarm rate, said second threshold crossing rate being the difference between the input signal and said second reference signal;
- and
- (c) feedback means for generating said first and second reference signals, said second reference signal begin a function of said threshold value level, said feedback means comprising:
- (1) a frequency-to-current converter means for converting the frequency of said second threshold crossing rate to a current signal, said frequency-to-current converter comprising:
- (i) a frequency divider to generate a signal corresponding to a fixed fraction of said second threshold-crossing rate, and
- (ii) a charge pump connected to said frequency divider to alternately connect a pump capacitor from a reference ground potential to a node to thereby generate said current signal at said node;
- (2) servo amplifier means coupled to said node, for generating said threshold value level based on a difference between said current signal and a predetermined current;
- and
- (3) further means, coupled to said servo amplifier means, for generating said second reference signal based on said threshold value level.
A method for automatically thresholding an input signal in the presence of gaussian noise to detect actual input signal events, comprising the steps of:
- (a) comparing the input signal and a first reference signal having a threshold value level, and outputting a first threshold crossing rate representing the actual input signal events and having a first false alarm rate, said first threshold crossing rate being the difference between the input signal and said threshold value level;
- (b) comparing the input signal and a second reference signal, and outputting a second threshold crossing rate having a second false alarm rate, said second threshold crossing rate being the difference between the input signal and said second reference signal;
- and
- (c) generating said first and second reference signals, said second reference signal being a function of said threshold value level, by:
- (1) converting the frequency of said second threshold crossing rate to a current signal by:
- (i) generating a signal corresponding to a fixed fraction of said second threshold-crossing rate, and
- (ii) alternately connecting, at the rate of said signal generated in step (i), a pump capacitor from a reference ground potential to a node to thereby generate said current signal at said node, and
- (2) generating said threshold value level based on a difference between said current signal and a predetermined current.
Dependencies are inferred from the claim text.