The novelty of this system is to modularize a combined microwave coupling and convection hot air system with the convection baffle doubling up as a matchplate with the use of one singular motor drive assembly.

The matchplate is a fixed metal plate, the dimensions of which are coordinated to create edge coupling to all the resonant modes that exist within the cavity over the frequency range of 2455 ± 20MHz.

For the matchplate to serve a dual role as convection baffle we have constructed parts from mica/glass. In this case, as the phase modulator and convection fan system rotates at high speed [nominally 2000 rpm], air recirculates and skirmishes both top and bottom elements. Air is restricted from exiting the sides of the baffle due to the mica/glass inserts. Mica/glass is needed here to allow microwave to propagate through these areas via edge coupling.

Then, by rating the top and bottom heating elements at the appropriate wattage, they can both be used either individually or together as an in-line impedance microwave control system as described in our Patent for Magnetron Control, USA Patent No. 5742032, European Patent No. 0764390.

The construction and integration of parts proved to be a very critical factor in the operation of the system. The phase modulator was positioned at ?/4 from the launchbox back wall with the convection fan at ?/2 from the back wall. This relationship provided the optimum impedance and power transfer between the magnetron and matchplate without creating any unwanted reflective components back to the magnetron.

A convection element was fitted so that its circumference was greater than the launchbox opening thus allowing the element to be outside the high microwave field region and so prevent any unwanted microwave coupling or microwave reflection.

The modularized system as designed is therefore eligible to fit to the back wall of any size of oven cavity. Only the dual convection baffle/matchplate would need to be of different size in order to effectively couple to the propagating modes that exist within the cavity. This makes the whole assembly a one-tooled item to fit all applications.

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