| 摘要 |
1,179,181. Waveguides. THOMSON-C.S.F. 10 Feb., 1967 [25 Feb., 1966], No. 6596/67. Heading H1W. [Also in Division H4] In a Cassegrain type aerial an active element 1, Fig. 10, is arranged to radiate elliptically polarized waves towards a subreflector 2 which transmits waves having a first kind of polarization but reflects towards a main reflector 3 waves having a second kind of polarization. In a first embodiment a rectangular waveguide (H), Figs. 11, 11a (not shown), in which the TE 10 mode is excited, feeds into an open-ended length of rectangular waveguide (G) which is coaxial with it but has been rotated by an angle (#) with respect to it. Consequently, both the TE 10 and the TE 01 modes are excited in the waveguide (G) and a phase difference is developed between them in transit to the radiating aperture because of their differing velocities in the waveguide (G). This embodiment is stated to be narrower in bandwidth than other embodiments. In a second embodiment (Figs. 12, 12a, not shown) energy from the feed waveguide (H) is extracted by a coupler (C) and is conveyed by a length of waveguide to the waveguide (G), where it is coupled in at a point (E), to excite the TE 01 mode therein in the required phase. In a third embodiment (Figs. 13, 13a, not shown) probes and a length of coaxial cable replace the couplers and waveguide used in the second embodiment. In a fourth embodiment, a rectangular feeder waveguide 1, Fig. 14, is directly connected to a radiating waveguide 23, and is excited in the TE 10 mode, part of the energy being picked up by a probe 7 which is coupled via a phase-shifter 6 to the sum port of a magictee 26. The difference port of the magic-tee is connected to a matching load 11, and its two output ports are coupled via connectors of equal electrical lengths to opposite slots 24, 25 in the waveguide 23, the slots being so disposed as to excite the TE 01 mode in the waveguide (Fig. 14a, not shown). |
