Active and Passive RF Components for High-Power Systems

Abstract

In recent years, R&D for pulse compression and power distribution systems for the Next Linear Collider has led to the invention of many novel rf components, some of which must handle up to 600 MW of pulsed power at X-band. These include passive waveguide components, active switch designs, and non-reciprocal devices. Among the former is a class of multi-moded, highly efficient rf components based on planar geometries with overmoded rectangular ports. Multi-moding allows us, by means of input phasing, to direct power to different locations through the same waveguide. Planar symmetry allows the height to be increased to improve power handling capacity. Features that invite breakdown, such as coupling slots, irises and H-plane septa, are avoided. This class includes hybrids, directional couplers, an eight-port superhybrid/dual-mode launcher, a mode-selective extractor, mode-preserving bends, a rectangular mode converter, and mode-mixers. We are able to utilize such rectangular waveguide components in systems incorporating low-loss, circular waveguide delay lines by means of specially designed tapers that efficiently transform multiple rectangular waveguide modes into their corresponding circular waveguide modes, specifically TE 10 and TE 20 into circular TE 11 and TE 01. These extremely compact tapers can replace well-known mode converters such as the Marié type. Another component, a reflective TE 01-TE 02 mode converter in circular waveguide, allows us to double the delay in reflective or resonant delay lines. Ideas for multi-megawatt active components, such as switches, have also been pursued. Power-handling capacity for these is increased by making them also highly overmoded. We present a design methodology for active rf magnetic components which are suitable for pulse compression systems of future X-band linear colliders. We also present an active switch based on a PIN diode array. This component comprises an array of active elements arranged so that the electric fields are reduced and the power handling capability is increased. Novel designs allow these components to operate in the low-loss circular waveguide TE 01 mode. We describe the switching elements and circuits.

A compact rectangular waveguide TE10 to TE20 mode converter with coplanar and codirectional configuration

“…Thus, many kinds of mode converters are required to realize the excitation and extraction of higher order modes. Among these, rectangular TE 10 to TE 20 mode converter is basic and has been utilized as an intermediate employed in various applications, such as TE 01 and TE 21 launchers [1][2][3][4][5][6].…”

“…The existing TE 10 to TE 20 mode converters can in general be divided into the following types: (1) the "jog converter" composed of two oppositely oriented 45°bends, with a circular TE 01 -mode bend to realize mode coupling [1,7,8], (2) the right-angled H-plane converter composed of an overmoded waveguide and a standard one with one port short-circuited to realize mode excitation with lateral wall coupling [2,3,9,10], (3) the converter with input and output ports in different planes, utilizing a coupling aperture to realize mode conversion [4,11], (4) the converter utilizing power division and 180°phase difference between two paths by different path length or opposite transition structure [5,6], (5) the converter utilizing periodic dielectric rod arrays in a waveguide to realize unique dispersion property and mode conversion [12,13].…”