GB1105503A - Improvements in or relating to antennae, e.g. radar antennae - Google Patents

Abstract

1,105,503. Aerials. STEPHENSON CORPORATION. 3 May, 1965, No. 18471/65. Heading H4A. [Also in Division H1] In a dish-type aerial for simultaneous transmission and reception the two equal halves 10, 12, Fig. 2, of a paraboloid of revolution which has been divided along an axial plane are spaced apart on either side of an intermediate septum 14, a radiator is disposed at the focus of the half 10 and a receptor at the focus of the half 12, and the said radiator and receptor are coupled to a transmitter and a receiver, respectively. As described, in an application for measuring the speed of vehicles using the Doppler effect, a strip 13 is bent into a parabola and is fastened to the edges of the halves 10, 12 which are spaced ## (#=mean operating wavelength) apart. The septum 14 carries a centrally-disposed dipole 16, the upper part of which co-operates with the half-paraboloid 10 and the lower part with the half-paraboloid 12 and it also carries a subsidiary dipole 18, Fig. 4 (not shown) which is encased in a hollow nylon screw 20 and which permits a predetermined amount of energy from the transmission side to be coupled into the receiving side. The upper part of the dipole 16 is coupled by waveguides 26, 27 to a reflex klystron 24 and the lower part thereof is coupled by wave-guides 28, 29 to a choke housing 30 and a microwave mixer detector assembly 32, which actuates a speed measuring device 34. The two waveguides 26, 28 constitute the upper and lower portions of a waveguide 25, Fig. 4 (not shown), with the septum 14 as a common wall. The sum of the heights of the waveguides 26, 28 and the thickness of the septum 14 is made less than the height of a standard waveguide with the object of reducing coupling between their outer walls and the dipoles.