Wave guide element for an electrically controlled radar antenna

Claim 1

Waveguide antenna element of non-resonant type, provided with radiation openings in the form of slits, for use in constructing a wide-band, electrically controlled radar antenna having a lobe direction independent of a frequency of a fed-in electromagnetic field, the waveguide antenna element (V) including a feed opening (M) for the fed-in electromagnetic field, the feed opening dividing the waveguide antenna element in a longitudinal direction into a first part and a second part, the first and second parts being provided with absorbent terminations (A1, A2) at their outer ends, and a plurality of slits, the slits being arranged on a wide longitudinal side of the waveguide antenna element with their longitudinal directions substantially parallel to the longitudinal direction of the waveguide antenna element, the slits in the first part of the waveguide having centers separated by a first spacing (d 1 ), the first spacing being less than half a wavelength of the fed in field in the waveguide antenna element, and the slits in the second part of the waveguide having centers separated by a second spacing (d 2 ), the second spacing being greater than half the wavelength of the fed-in field, said first and second spacings being selected such that the lobe direction is substantially identical for the first and second parts.