Method for preventing electrical short in impedance tuners using mechanical stop

摘要

Mechanical vertical stops, in form of metallic or plastic screws or dowel pins are introduced as permanent limits and attached on the tuning probes or the vertical axis of slide screw impedances tuners; the vertical stops are adjusted in order to prevent the probes from getting closer to the center conductor than a certain limit; this limit is calculated to prevent corona discharge at a specified maximum RF power and a required maximum reflection factor (Gamma). The adjustment method uses measured data of Gamma as a function of the vertical position of the probe to estimate and adjust for the requested gap to be maintained between the probes (at their lowest position) and the center conductor at any given RF power. The technique can be used in automatic, stepper controlled, as well as in manual, micrometer screw controlled, tuners.

主权项

1. A method for preventing electrical short in slide screw impedance tuners;
said tuners having an input (test) port and an output (idle) port, a slotted airline (slabline) between said ports, and a mobile carriage travelling parallel to the axis of said slabline and having an adjustable vertical axis and a metallic tuning probe attached to said axis, said probe having a concave bottom surface matching axially the round center conductor of said slabline,
and being insertable vertically into the slot of said airline,and being movable both vertically, towards said center conductor, and horizontally, parallel to the axis of said slabline; and at least one adjustable vertical limit screw, attached to said vertical axis or probe and limiting said probe's movement towards said center conductor; said method comprising two steps:
a) in a first step the smallest gap between the bottom surface of said metallic tuning probe and said center conductor of the slabline of said tuner is determined, for safe (non electrically-shorted) operation, andb) in a second step said limit screw(s) is (are) adjusted in order to prevent the tuning probe from approaching said center conductor closer than said gap.