GB1395638A - Waveguide arrangements - Google Patents

Abstract

1395638 Waveguide mode filters NIPPON TELEGRAPH & TELEPHONE PUBLIC CORP 11 July 1972 [19 July 1971] 32320/72 Heading H1W In order to suppress TE 02 mode energy in a waveguide for transmission of the circular electric TE 01 mode, the waveguide is divided, over a certain length, by a diametral septum into two parts within which the TE 02 mode velocities are unequal whilst the TE 01 mode velocities are equal. As shown in Fig. 2, a septum 2 divides the circular waveguide into a lower part 20 of radius R 0 and an upper part of smaller radius R<SP>1</SP>. As a result of the unequal radii, the TE 02 mode propagates at different velocities in the two parts whereby a differential phase change of 180 degrees is produced with consequent destructive interference. The upper part 10 contains an elongated dielectric U- shaped element 3 of radius R 3 =0À5426 R<SP>1</SP> at which radius the TE 01 mode has maximum electric field strength and the TE 02 mode zero field strength. The effect of the element 3 is to equalize the velocities of the TE 01 mode in the two parts of the waveguide whereby energy in this mode is transmitted unaffected to the rest of the system. The septum may have pads of dissipative material at its extremities for absorption of the unwanted TE 02 component (Fig. 9, not shown). The element 3 may be replaced by a pair of rods adjacent the septum (Fig. 6a, not shown). The two waveguide parts 10, 20 may have equal radius and the lower part 20 may be loaded with a lining of dielectric or magnetic material to produce the necessary differences in phase velocities (Fig. 6b, not shown). The dielectric element 3 may be replaced by a magnetic element having a radius R = 0À3428 R<SP>1</SP> which has the same effect.