Doppler radar with ambiguous electronic scanning

1 . A radar with ambiguous electronic scanning designed to cover a given angular field, the radar with ambiguous electronic scanning comprising an active antenna comprising an array of elementary transmission antennas and an array of elementary reception antennas with a same angular opening, said transmission and reception arrays having a same radiation plane, characterized in that:

said transmission array is ambiguous with a number N ambTx of ambiguous lobes within said angular opening, N ambTx being greater than or equal to 2, producing a transmission radiating pattern;

said reception array comprises at least one ambiguous lobe within said angular opening, producing a reception radiating pattern, said transmission and reception arrays being arranged so that the product of the transmission and reception radiating patterns only produces a single main beam within the field defined by said angular opening;

wherein:

said transmission array comprises a number NTX of elementary antennas of angular opening Δθ, regularly spaced out by a distance LTX, producing an ambiguous angular radiating pattern of angular periodicity in θ such that sin θ is equal to λ/LTX, λ being the wavelength of said radar;

said reception array comprises a number NRX of elementary antennas of angular opening Δθ, regularly spaced out by a distance LRX, producing a potentially ambiguous angular radiating pattern of angular periodicity in θ such that sin θ is equal to λ/LRX;

the ambiguity periods of the transmission and reception arrays, respectively, being chosen to be different from one another, and in such a manner that, for any given pair of transmission and reception orientation directions, there is no more than one possible coincidence of ambiguous transmission and reception directions within said angular opening;

said radar being configured for covering the given angular field:

by moving by electronic scanning the main direction of a beam focused by all of the NTX transmission antennas within a field of ambiguity defined by sin θ=λ/LTX;

for each orientation direction of a transmission, using beam formation by computation based on the signals collected on the NRX reception antennas, by generating a set of beams focused in the main direction and each of the ambiguous directions formed by the transmission array.

2 . The radar as claimed in claim 1 , configured for covering the given angular field:

by forming transmission radiating patterns that are focused within a field limited to a transmission ambiguity field,

by simultaneously forming several transmission radiating patterns focused at reception in ambiguous transmission directions.

3 . The radar as claimed in claim 1 , characterized in that residual ambiguity lobes are rejected by Doppler filtering.

4 . The radar as claimed in claim 1 , characterized in that residual ambiguity lobes are rejected by selectivity in distance.

5 . The radar as claimed in claim 1 , characterized in that said active antenna is of a type active array with electronic scanning.

6 . The radar as claimed in claim 1 , characterized in that said active antenna is of a type with multiple inputs and outputs.

7 . A method of electronic scanning of a given angular field using a radar with ambiguous electronic scanning designed to cover a given angular field, the radar with ambiguous electronic scanning comprising an active antenna comprising an array of elementary transmission antennas and an array of elementary reception antennas with a same angular opening, said transmission and reception arrays having a same radiation plane, wherein:

said transmission array is ambiguous with a number N ambTx of ambiguous lobes within said angular opening, N ambTx being greater than or equal to 2, producing a transmission radiating pattern;

said reception array comprises at least one ambiguous lobe within said angular opening, producing a reception radiating pattern, said transmission and reception arrays being arranged so that the product of the transmission and reception radiating patterns only produces a single main beam within the field defined by said angular opening;

wherein the given angular field is covered:

by forming transmission radiating patterns that are focused within a field limited to a transmission ambiguity field,

by simultaneously forming several reception radiating patterns focused at reception in ambiguous transmission directions;

wherein:

said transmission array comprises a number NTX of elementary antennas of angular opening Δθ, regularly spaced out by a distance LTX, producing an ambiguous angular radiating pattern of angular periodicity in θ such that sin θ is equal to λ/LTX, A being the wavelength of said radar;

said reception array comprises a number NRX of elementary antennas of angular opening Δθ, regularly spaced out by a distance LRX, producing a potentially ambiguous angular radiating pattern of angular periodicity in θ such that sin θ is equal to λ/LRX;

the ambiguity periods of the transmission and reception arrays, respectively, being chosen to be different from one another, and in such a manner that for any given pair of transmission and reception orientation directions, there is no more than one possible coincidence of ambiguous transmission and reception directions within said angular opening;

and wherein the given angular field is covered:

by moving by electronic scanning the main direction of a beam focused by all of the NTX transmission antennas within a field of ambiguity defined by sin θ=λ/LTX;

for each orientation direction of a transmission, using beam formation by computation based on the signals collected on the NRX reception antennas, by generating a set of beams focused in the main direction and each of the ambiguous directions formed by the transmission array.

8 . The scanning method as claimed in claim 7 , wherein residual ambiguity lobes are rejected by Doppler filtering.

9 . The radar as claimed in claim 7 , characterized in that residual ambiguity lobes are rejected by selectivity in distance.