GB628814A - Improvements in or relating to means for the phase displacement of a wave in a waveguide - Google Patents

Abstract

628,814. Waveguides ; directive radio systems. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. May 8, 1946, No. 13962. Convention date, March 22, 1944. [Classes 40 (v) and 40 (vii)] A rectangular waveguide carrying an H01 wave is coupled to a co-axial transmission line by means of a narrow conducting frame which is arranged in the guide with its long sides parallel to the electric vector at a point in the guide where the magnetic field is rotating. Mathematical analysis is given to show that in a guide. Fig. 4, in which the electric vector is parallel to the shorter side a, the planes along which the magnetic field is rotating are removed from the centre plane of the guide by b # a distance - arc cos -. For a guide dimen- # 2b sioned to give a maximum magnetic field, these planes lie at one third and two-thirds of the distance between the shorter sides. In Fig. 5 a narrow frame A, B, C, D is placed one-third of the distance from one of the shorter sides of a waveguide, and is coupled to an outgoing coaxial line. The frame is closed by the guide wall on the side AC. If the frame is rotated about CD, the phase of the wave fed to the coaxial line may be varied between 0 and 2# relative to the wave in the guide without any change in amplitude. This is used in the radio-goniometer shown in Fig. 6, in which a plane incident wave XY is received.by identihorns Q<1>, Q<2> and waveguides G<1>, G<2>, coupled by rotatable wire frames and coaxial lines to a receiver R. If one of the frames is turned to give a maximum indication in the receiver, the amount turned is an indication of the phase difference in the guides G<1>, G<2>, and from this the direction alpha of the incident wave can be calculated. Fig. 8 shows an arrangement for producing a directive beam which is rapidly swept to and fro across a sector of the horizon. A generator E feeds horn Q<2> directly, and also feeds horn Q<1> through a phase-shifting frame F, which is rapidly rotated to shift the phase through 180 degrees and cause the combined beam to oscillate. The Specification as open to inspection under Sect. 91 also describes a modulating device shown in cross-section in Fig. 10 (Cancelled), comprising a rectangular guide G<1> which receives a wave from a generator and is coupled to an emitting guide G2 by coaxial lines F<1>, F<2>, each connected to phase shifting frames a<1> ... d<1> and a2 ... d<2> arranged at <1>/3 and 2/3 the height of the guide. The frames are rotated at the same speed in the same direction and the result in the guide G<2> is the original wave amplitude modulated at the frequency of rotation of the frames. This effects modulation without altering the load on the generator. This subject-matter does not appear in the Specification as accepted.