System for detecting the presence of a pure signal in a discrete noisy signal measured at a constant average noise level with a probability of false detection below a predetermined false detection level

• US 4,782,456 A
• Filed: 04/23/1986
• Issued: 11/01/1988
• Est. Priority Date: 04/23/1985
• Status: Expired due to Fees

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Original Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Inventors: Rambaut, Michel, Poussier, Emile
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Cosimano, Edward R.
• Application Number:
  US06/855,494
• Time in Patent Office: 923 Days
• Field of Search: 358/167, 364/571, 364/574, 364/554, 381/94
• US Class Current: 702/74
• CPC Class Codes: G01T 1/16 Measuring radiation intensity G01T1/29 takes precedence ; self-powered detectors G01T3/006; using an ionisation chamber filled with a liquid or solid, e.g. frozen liquid, dielectric G01T3/008

Abstract

A system for detecting the presence of a pure signal in a discrete noisy signal measured at a constant average noise level M, having a processor for measuring a counting rate N and for calculating a false detection probability PF as a function of the counting rate and an estimated average noise level M, and for comparing the probability with a predetermined false detection level TF. A pure signal is detectd when the probability is below the false detection level.

Claims

1. A system for detecting the presence of a pure signal in a discrete noisy signal measured at a constant average noise level, comprising:

in series a converter for converting radiation received thereby into electrical pulses, a shaping means, a binary counting scale, a processing means, and a signalling means;

said processing means comprising a processor, at least one memory, and an input-output circuit, said processor comprising means for measuring a counting rate N during successive equal time periods, means for estimating a value of an average noise level M, means for calculating a false detection probability PF as a function of said counting rate N and of the estimated average noise level M, and means for comparing said false detection probability PF with a predetermined false detection level TF, to thereby ascertain that a pure signal has been detected when said false detection probability PF is below said false detection level.

2. A system according to to claim 1, wherein the memory comprises a sequence of cells and contains a table for one value of the predetermined false detection level TF, a cell of subscript I containing a value M_I, such that the false detection probability for said average noise level M_I and a counting rate I is equal to the false detection level, the processor comprising means for comparing, following each measurement, a value M_N contained at subscript N of the table, in which N is the measured counting rate, with the estimated average noise level M, to thereby ascertain that a pure signal has been detected when M_N ≧

M.

3. A system according to claim 2, wherein the processor comprises means for evaluating the average noise level M for a mean value of k count rates preceding a final measurement, in which k is an integer.

4. A system according to claim 1, wherein the memory comprises a sequence of cells and contains a table for one value of the predetermined false detection level TF, a cell of subscript I containing an integral value T equal to the closest integer to kM_I, in which k is a given integer and M_I the average noise level such that the false detection probability for said average noise level and a counting rate I is equal to the false detection level, the processor comprising means for comparing, following each measurement, a value T_N contained at subscript N of the table, in which N is the measured counting rate at the integer T closest to kM, with the known average noise level, to thereby ascertain that a pure signal has been detected when T_N ≧

T.

5. A system according to claim 4, wherein the processor comprises means for evaluating the average noise level M by the mean value of k count rates preceding a final measurement, in which k is an integer and wherein the integer T, compared with a value T_N of the table, is equal to the sum of the k counting rates preceding the final counting rate N.