GB1023112A - Improvements in or relating to a microwave antenna - Google Patents

Abstract

1,023,112. Aerials. LABORATORY FOR ELECTRONICS Inc. May 9, 1963 [May 10 1962], No. 18470/63. Heading H4A. [Also in Division H1] The invention relates to an aerial for an airborne Doppler navigation system and provides a pencil beam which may be switched to a plurality of directions 11-14, Fig. 1 (not shown), inclined to, and symmetrical about, the vertical axis. The aerial comprises a plurality of identical waveguides 41, Fig. 2, each connected to a pair of feed waveguides 21, 22, by slots in these latter. Each of the waveguides 41 radiates through slots inclined to the longitudinal axis and the angle of inclination and depth of slot is varied along the guide such that the coupling coefficient g(n) of the nth slot from either end of the waveguide is given by g(n) = sin<SP>2</SP> + n#/N+1 + D N+1 where N is the total number of slots in the guide and D is an empirical constant. Such an arrangement gives an asymmetric tapered amplitude distribution providing a beam of suitable width and side lobe level. The coupling between the radiating waveguides 41 and the feed waveguides 21 and 22 is arranged in a corresponding manner. Formulae are derived for the variation of slot angle and depth, and to relate the spacing of the slots in the waveguides 41 and 21, 22, to the angles between the directions 11-14 and the X and Y axes. As described, the beam is switched in turn to only three of these directions by energizing in turn three of the four input ports 31-34 of the array, the fourth port being terminated in a matched load. A microwave switch (see Division H1) is described with reference to Fig. 5 (not shown) for connecting these three ports in turn to a common feed.