Saab-scania Ab

Arne Torby

An antenna array for directional determination comprises two pairs of elongated end-firing log-periodic antenna elements, each pair fixed symmetrically to a reference plane and preferably forwardly convergent to it. The two antenna elements of one pair converge forwardly at an angle b, those of the other pair converge at a preferred angle a=1.5 b. In one embodiment each pair is connected with a 90.degree.--hybrid, and from the detected and amplified signals across individual elements of each pair there is obtained a difference signal designated L.sub.1 for the b-angle pair, L.sub.2 for the a-angle pair. A third difference signal L.sub.3 is obtained from L.sub.2 -L.sub.1. The magnitude of each difference signal depends upon value of an angle V between a symmetry line in the plane of symmetry, symmetrical to the antenna elements, and the projection in that plane of a line through the array and a detected radiation source. An indication of V is taken on the basis of L.sub.1 if L.sub.1, L.sub.2 and L.sub.3 are on the same side of zero. A more precise indication of V is then taken on the basis of L.sub.2 by comparing absolute value of L.sub.2 with the absolute value of an adjustably variable reference signal. Other signal processing arrangements are disclosed that produce the same effective lobe sharpening.

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Linkoping, Sweden

Arne Torby