GB1362926A - Mode interferometer squinting radar antenna - Google Patents

Abstract

1362926 Aerials UNITED AIRCRAFT CORP 8 Nov 1972 [21 Jan 1972] 51528/72 Heading H4A Apparatus for coupling electromagnetic waves between waveguides and a reflector comprises a first section of a pair of waveguides having means for providing a variable relative phase shift between waves therein, a second section of a pair of waveguides having means for providing a relative phase shift between waves therein. All the waveguides have the same primary dimensions and the two sections are coupled together by, for example, a short slot coupler. A fifth waveguide having a primary dimension which is substantially twice that of the corresponding primary dimension of the other waveguides is connected at one end to the said second section, and has a radiating aperture at its other end. As described, electromagnetic waves enter a complex waveguide assembly 21, Fig. 8, through openings 33, 34 and propagate along a section A in two separate similar waveguides, i.e., of rectangular cross-section, supporting the TE 10 mode. The waveguides continue into a section B, where a variable phase shifter 44 is disposed. This comprises a ferrite section 46 with electrical winding 48, and with matching sections 50, 52 at its ends. The current in the winding 48 is determined by a squint control circuit 54, which may be manually operated or may be automatically operated by a beam steering computer. In a further section C a short slot coupler is provided, such that half of the wave energy in each waveguide spills into the other, with a 90 degree phase lag. The waves continue along a section D in separate waveguides in one of which is a second phase shifter 61 with a winding 62 carrying a current from a source 64, which provides a constant phase shift of 90 degrees. The last section E is a single waveguide, having twice the width of the other waveguide sections, within which the two TE 10 mode waves from the section D combine to produce single TE 10 and TE 20 mode waves across the entire width of the section E (Figs. 1 to 4, not shown). A tuning screw 68 is provided to further the development of the TE 10 mode the section E. The phase centre of the resultant waves emanating from the open end 63 of the section E may be moved transversely by adjustment of the squint control circuit 54, thus providing scanning when the assembly is used as a feed for a parabolic reflector (Figs. 5 to 7, not shown).