The behaviour of
an open-ended

This applicator and system were developed with intense use of the QuickWave™ modelling software. In particular, field pattern studies which would have simply been impossible to conduct experimentally were necessary for the optimisation.

A scenario with two closely located 2450 MHz applicators (of a type called “FERA”) is shown above. Dimensions are about 120×120×180 mm. In the microwave enclosure below the applicators there is a 120 mm high load (in red), with 30 mm air above and 40 mm below. The load permittivity is 6 and its power penetration depth is 100 mm.

The movie shows the dominating magnetic field directed perpendicularly to the vertical cross section marked yellow, in that central section. The intensity colour scale is: magenta = +100 %, green = 0, dark blue = –100 %. In the power pattern image, dark blue = 0 and the boundary dark/lighter blue = 10 %. The top image shows the momentaneous vertically directed standing electric field maxima and the middle image shows the power deposition pattern.

There are two applicator modes: a dominating evanescent hybrid mode with index 2 in the shown cross section and 1 in the 180 mm direction, and a compensating propagating TE10 mode having constant electric field in the cross section plane, parallel to it. The magnetic fields counteract at the applicator opening walls, resulting in a “focused” propagating Poynting vector straight down from the centre of the applicator opening. Since the load height is comparable to the power penetration depth, a standing wave pattern results in it. 

Another very important feature is also seen in the movie to the left: there is very little energy coupling to the adjacent un-energised applicator with waveguide feed. Under all normal loading conditions, less than 1 % is cross-coupled between any adjacent applicators. This contributes to a high system efficiency and protects magnetron generators from damaging each other.

The FERA applicators are very versatile and are currently employed in four different projects. An example is shown here.