FIELD: physics.
SUBSTANCE: in the method of detecting non-coherent signal packets with constant false alarm level, in which in each of N repetition periods the non-coherent packets the following is carried out: a window is created from Nw range elements lying symmetrically relative the inspected k-th range element, where 
interference power in the inspected range element is evaluated from the average value of squares of the envelope curve of interference 
in the window from Nw range elements, the square of the envelope curve is normalised in the inspected range element 
to interference power evaluation 
After that normalisation results 
are averaged in N repetition periods of the non-coherent packet. Availability of a non-coherent signal packet in the inspected range element is indicated by the averaged normalisation result overshooting the threshold level C. The following is carried out: from results of normalizing zk,n in N repetition periods of the non-coherent packet, an ordered sample 
is formed, elements of this sample with rank r from N-Ns+1 to N, where Ns<N, weighted with a fixed coefficient d, defined by permissible loss value of detecting a non-coherent signal packet in the presence of noise, are compared with an element of an ordered sample with rank N-Ns, that way checking fulfillment of the condition 
for r=N,…N-N2+1. If the given condition is met, a signal which is not synchronous with the repetition period is detected in the i-th repetition period of the non-coherent packet, where i is found from the expression 
The normalising result zk,i related to presence of the said signal which is not synchronous with the repetition period is excluded from the averaged normalizing results. The number of times m, where 0≤m<Ns, when the said condition is met is calculated. The threshold level C is varied depending on the number m so as to ensure the given probability value of false alarm.
EFFECT: lower level of false alarm.
2 dwg
