Low power measurement of power coupling out of Fabry-Perot resonator at mm wavelengths : Comparison between some techniques
Three different ways of coupling energy from a large Fabry-Perot resonator have been tested at freqüncies around 120 GHz, in the frame of quasi-optical gyrotron development. Coupling through annular slots in one of the mirrors, Cassegrain coupling and power extraction through a mirror perforated with parallel slits acting as a strip grating have been compared after propagation in a strongly overmoded circular waveguide by measuring the field pattern at different positions. With the use of slotted mirror or Cassegrain system the coupling is purely diffractive whereas, in the third case, the mirror can be considered as semi-transparent. Marcuvitz has given a formula for the transmission cöfficient of infinitely thin capacitive strip gratings, valid for the case a/lamda less than 1, and electric field perpendicular to the strips. The slits can be considered as waveguides propagating TE(no) modes. The measure of the radiated field dös not give directly the mode of propagation inside the tube but provides a good approximation.
Bibliographic Reference: Paper presented: Fourteenth International Conference on Infrared and Millimeter Waves, Würzburg (DE), Oct. 2-6, 1989
Availability: Available from (1) as Paper EN 35212 ORA
Record Number: 199010929 / Last updated on: 1994-12-01
Original language: en
Available languages: en