GB604987A - Directive couplings between waveguides and co-axial lines - Google Patents

Abstract

604,987. Power meters. ALLAN, H. R., CURLING, C. D., COOK, A. H., SPENDLEY, W., ANDREWS; P:, and: WEIGHT, C. S. Dec. 11, 1945, No. 33457. [Class 37] [Also in Group XL (c) To form a directive, coupling between a wave guide and a coaxial line, for example for power measuring purposes, the inner, conductor of the axial line is extended into the wave-guide as a looped coupling terminated so that it responds to or excites both transverse electric and magnetic fields in the waveguide, and means are provided for separately adjusting the relative magnitude and phase of the -electric and magnetic excitations. ' In Fig. 1 the inner conductor 2 of a coaxial line 2, 3 is extended into a wave-guide 1 to form a loop 6 which is terminated by a resistor 7 inside a coaxial sleeve 8. Loop 6 respondsto both transverse magnetic and transverse electric components in the waveguide, and the magnitudes of the effects may be made equal by rotating the loop assembly in the boss 4. Phase control is obtained, by axial movement of resistor 7. When this has been effected, the loop responds to, or excites, energy flowing in one direction only in the guide. This may be used for injecting energy for test purposes into a wave-guide connecting a receiver to an aerial. Or, if two such units are arranged to respond to energy in opposite directions, the forward and backward power may be measured, from which the standing wave ratio may be derived. Instead of resistance 7, an alternating cable may be used, or discs of lossy dielectric may be mounted on the conductor 9 close to the loop, and phase adjustment may be effected by axial movement of a piston behind the discs. Alternatively, conductor 9 may be made of insulating material which is coated near loop 6 with resistive material and elsewhere with conducting material. Phase adjustment may alternatively be effected by an adjustable screw projecting into the wave-guide to form a byepass capacity to the resistive impedance. Instead of using two directive couplings for the separate measurement of forward and backward power, a single unit retatable into two balanced conditions may be used. In Fig. 3 a unit 2, 3, 6, 7, 9 functioning as in Fig. 1 is mounted in a conical member 12 rotatable in a boss 13 on a waveguide 1. The two effective positions are marked by springs 16, 17 engaging notches in adjustable rings 14, carried on member 12.