GB585225A - Improvements in or relating to measurements in ultra high frequency electrical systems - Google Patents

Abstract

585,225. Coil-less resonators. FALLOON, S. W. H. W., BROWN, R. H. J., and WRIGHT, C. S. July 28, 1944, No. 14488. [Class 40 (iii)] - [Also in Group XXXVI] Apparatus for the measurement of standing wave voltages on a transmission line comprises a potential divider slidable along the line and formed by a stub line of quarter wave length and short-circuited at its free end, with a voltage measuring device including a rectifier connected to the stub at a predetermined distance from the short-circuited end. Alternatively the rectifier may be slidable along the line, the stub line being omitted. The main transmission line comprises a coaxial line formed by an inner conductor 1, Fig. 1, and an outer conductor 2, which is slotted to enable the inner conductor 3 of a stub line to be slid along the main line 1, 2 to measure standing wave voltages at different locations. The outer conductor 4 of the stub line is in intimate contact with the outer conductor 2, and the free end of the stub is short-circuited at 5. The length of the stub is one quarter of the wave-length of the energy in the main line 1, 2 and the voltage at a selected point is measured by means of a rectifier, which may be a crystal rectifier or a miniature diode with its anode lead 6 connected to the inner conductor 3 and its cathode 7 connected to the outer conductor 4 by by-pass condensers 8. The cathode 7 is connected to the core 9 of a screened cable which has its sheath 10 connected to the outer conductor 4 of the stub. The core 9 is connected through a meter 11 to a potentiometer 12 by means of which the peak voltage applied to the diode may be determined, which voltage is a known fraction of the voltage at the tapping point in the line 1, 2. When the peak standing wave voltages in the line 1, 2 are low enough to be applied to the rectifier, the stub line need not be used and the rectifier or diode may be inserted directly into the main transmission line so as to slide along it with its anode lead in contact with the inner conductor 1 and its cathode lead projecting through a slot in the outer conductor 2 and connected to one end of a screened cable, the sheath of which is in contact with the outer conductor 2. Instead of inserting the diode directly into the line or into the stub, it may be located at the far end of a half wave-length of screened cable 14, Fig. 2, with its'anode connected to the central conductor. The free end of the screened cable has its central conductor extended as a probe 15 which projects into the coaxial line under test through a slot 16 in the outer conductor.