GB767067A - Microwave transmission line phase shifter - Google Patents

Abstract

767,067. Phase-adjustment of strip transmission lines. STANDARD TELEPHONES & CABLES, Ltd. Jan. 26, 1955, No. 2349/55. Class 40 (8). The electrical length of a strip transmission line is adjusted by inserting in the electromagnetic field a variable volume of dielectric material. The transmission line is of the type comprising a metallic strip conductor 1 separated from a ground plane conductor 2 by means of a dielectric layer 3 a small fraction of a quarterwavelength thick. To effect the desired adjustment a triangular dielectric slab 4 is inserted a variable amount into a gap in the dielectric layer 3. The slab 4 and the edges of the gap may be bevelled as shown, or, in a modification, the bevels may be complementary so that the slab 4 fills the gap completely when fully inserted. The slab 4 may have a higher dielectric constant than the layer 3. Alternative arrangements are described (Fig. 7, not shown) in which the dielectric layer 3 is continuous and the dielectric slab is inserted into the electromagnetic field adjacent the strip conductor 1 on the face remote from the ground conductor 2. The dielectric slab may have a variety of shapes and may be mounted on a pivot so that it may be rotated to and from its operative position. Several dielectric slabs may be ganged together by a mechanical linkage (Figs. 16, 17, not shown) which enables them to be moved through relatively different distances by a common actuating member. In the modification of Fig. 14, the electrical lengths of lines 18-22 are varied by different amounts upon displacement of the bevelled dielectric member 23. Where several lines 24-31, Fig. 15, form a junction the electrical lengths of the lines are varied by different amounts by rotating the bevelled dielectric member 32 about its pivot 33. In the construction shown in Fig. 12 a rat-race formed of strip transmission lines 9-12 is tuned to a desired centre frequency by means of a circular, bevelled dielectric member 4 which is movable towards and away from the transmission lines 9-12 upon a spigot 13. The invention may be applied to strip transmission lines of the type in which spaced ground conductors are provided on either side of the strip conductor.