We Claim:
1. A method for forming adaptive reception beams for a detection system comprising a multi-sensor antenna, the 5 forming of adaptive beams making it possible to eliminate a spurious signal or a noise, characterized in that it comprises:
- a first step (11) of forming N interlocked sub-antennas, each sub-antenna n comprising a number of
) identical sensors, the phase centers of the sub-antennas exhibiting a given offset relative to one another;
- a second step (12) of forming, for each sub-antenna n, M primary reception beams, from the sensors
J forming the sub-antenna concerned;
a third step (13) of forming M secondary reception beams, each secondary beam m being formed from the primary beams m corresponding, for the N sub-antennas, to the same direction of observation, this
i step is performed by implementing an adaptive processing of the signals produced by the primary reception beams;
the sensors forming one and the same sub-antenna being determined so that the phase centers of any two sub-antennas n and n' are separated from one another by a distance less than the spatial correlation distance of the noise or of the spurious signal that is to be eliminated.
2. The method as claimed in claim 1, wherein, the operation of the detection system being a narrowband mode of operation, the third step (13) carries out the following operations:
- a first operation (51) of estimating, for each primary beam m, the covariance matrix r(m) of the signals Vn(m,t) (54) formed in the direction m for all
the N sub-antennas; the estimated covariance matrix r(m) then being inverted;
- a second operation (52) of determining, for each
-> beam m, the phase-shift vector d(m) defined by the
following relationship:
[d(m)]n=exp(i2*^0m8n) c
in which fo designates the center frequency of the
signal and Um a unitary vector in the direction of pointing of the beam m;
- a third operation (53) of actually forming the M adaptive secondary reception beams by determining the signal Vs(m,t) corresponding to each of the beams m, the signal Vs(m,t) being defined by the relationship:
3. The method as claimed in claim 1, wherein, the operation of the detection system being a wideband mode of operation, the third step (13) implements an initial operation of breaking down the spectral band of the received signal into spectral sub-bands k so that the signal corresponding to each sub-band is a narrowband signal; then, for each spectral sub-band, the following operations:
- a first operation (51) of estimating, for each secondary beam m, the covariance matrix r(m,t,k) of the signals Vn(m,t,k) (54) formed in the direction m for all the N sub-antennas; the estimated covariance matrix r(m,t,k) then being inverted;
- a second operation (52) of determining, for each
-> beam m, the phase-shift vector d(m,k) defined by the
following relationship:
method following this additional step (14) being implemented in parallel, ; on each of the duly formed Doppler beams.
6. The method as claimed in claim 5, wherein the Doppler analysis applied is an analysis by multi-copy correlation which consists in correlating the received signal with copies of the transmitted signal affected by different given delays.
7. The method as claimed in any one of the preceding claims, wherein, each of . the sub-antennas exhibiting a spatial ambiguity, in a idirection m' , in relation to the direction m considered, the operation 53 then consists in computing, in addition to the signal Vs(m,t), the signal Vs(m',t) defined by the following relationship: ;
r . -i +
in which m' corresponds to the ambiguous direction in relation to the main direction m.
8. An application of the method as claimed in any one of the preceding claims to a system comprising a linear antenna formed by sensors separated from one another by a constant distance d; i the step (11) of forming N interlocked linear sub-antennas being performed by associating the signals received by sensors separated from one another by N -d, the sub-antennas being offset from one another by a distance d; the phase centers of the sub-antennas thus produced exhibiting an offset d relative to one another.
9. An application of the method as claimed in any one of claims 1 to 7 to a system comprising a planar
antenna formed by sensors arranged in rows and columns and separated from one another by a constant distance d; the step (11) of forming N interlocked planar sub-antennas being performed by associating the signals 5 received by sensors positioned on rows and columns separated from one another by N -d, the phase centers of the sub-antennas thus produced exhibiting an offset d in rows or in columns relative to one another.