GB1412352A - Follow-up system for microwave antennae - Google Patents

Abstract

1412352 Mode couplers LICENTIA-PATENT VERWALTUNGS GmbH 19 March 1973 [17 March 1972] 13083/73 Heading H1W [Also in Division H4] A direction-finder system, in which higher order modes produced in a waveguide are utilized to provide azimuth and elevation angular deviation data concerning a distant transmitter, comprises a transistion between an aerial feed waveguide of non-square crosssection, e.g. circular, or cruciform, or octagonal and a succeeding waveguide of square crosssection, and a mode coupler adapted to extract the deviation data from the received signal. The mode coupler may be provided with a branch network and the deviation data signal be applied to a comparator network. The system may be used with either linearly or circularly polarized radiation, and it is particularly suitable for tracking a communications satellite from a ground station. As described, a mode coupler H, Figs. 4, 5, comprises a square cross-section wave guiding member tapering from its front part, where it receives any H 20 and H 02 mode waves from the square cross-section waveguide (arising from angular deviations of the transmitter), to its rear part. The H 20 and H 02 mode waves are capable of propagation only in the front part of the coupler, so that standing waves are set up which are coupled out by eight elements K1 to K4 (H 20 waves) and K5 to K8 (H 02 waves). The couplers comprise longitudinally extending bars B which are evenly spaced around the coupler, as shown. Each bar is connected at its middle to a co-axial wave guide member L, which extends to a coupling loop in a cavity HO. The pairs of elements (K1, K2), (K3, K4), (K5, K6), (K7, K8) provide inputs to respective hybrids HY1, HY2, HY3, HY4, in which said cavities HO are comprised. Outputs from the hybrids HY1, HY2 are combined in a hybrid HY5 to provide at a port 4 thereof an output PH20 equivalent in amplitude to the original H 20 waves. The hybrids HY3, HY4 are similarly coupled to a hybrid HY6, and an output PHO2 equivalent in amplitude to the original H 02 waves appears at a port 4 thereof. In a first arrangement for processing the PH20 and PH02 outputs they are combined in a directional coupler R, Fig. 10, having variable coupling attenuation α K . A variable phase shifter Ph is inserted in the PH02 line. The directional coupler R provides outputs which are respresentative of the angular deviations of the transmitter in orthogonally disposed planes. In a second arrangement, the PH20 and PH02 outputs are coupled through a hybrid (HY7), Fig. 11 (not shown), and in a third arrangement the outputs from that hybrid are coupled through a further hybrid (HY8), Fig. 12 (not shown), a variable phase shifter and a variable attenuator being connected in circuit between the said two hybrids.