Container for active microwave heating

A package adapted for microwave defrosting and cooking or heating of frozen foods comprising:

• an oval tray having an open end, a closed base that is smaller than said open end, and side walls tapering outwardly from said closed base to said open end, said side walls comprising a microwave transparent material which extends from said closed base to said open end, and conductive, microwave opaque material which extends from said side walls onto said closed base and forms a lip at the edge of said closed base;
• said closed base comprising an annular base ring of conductive, microwave opaque material encompassing a first area of microwave transparent material, and a second area of microwave transparent material between said annular base ring and said lip, said annular ring and said lip being designed and adapted to establish boundary conditions at said ring and at said lip that produce a central energy maxima within said first area and a subsidiary energy maxima in said second area:
• an oval lid that covers the open end of said tray, said lid comprising microwave transparent material, a central patch of conductive, microwave opaque material;
• and at least two additional patches of conductive, microwave opaque material positioned between said central patch and said sidewalls, each of said additional patches comprising a section of an interrupted annular lid ring that is separated from said central patch by an annular ring of microwave transparent material, said annular lid ring being interrupted by microwave transparent material between ends of said patches of conductive material and said annular lid ring being separated from said side walls by an annular area of microwave transparent material, said central patch being designed and adapted to enhance microwave intensity under said lid in the central region of the container, and said interrupted annular ring being designed to provide localized enhancement of heating in the area beneath said annular lid ring;
• whereby said side walls, said base and said lid co-operate to produce more uniform heating within said container.

A package adapted for heating in a microwave oven comprising:

• a tray having an open end, a closed base and side walls extending from said closed base to said open end;
• said side walls comprising a microwave transparent material which extends from said closed base to said open end, and conductive, microwave opaque material which extends from said side walls onto said closed base and forms a lip at the edge of said closed base;
• said closed base comprising an annular base ring of conductive, microwave opaque material encompassing a first area of microwave transparent material, and a second area of microwave transparent material between said annular base ring and said lip, said annular base ring and said lip being designed and adapted to establish boundary conditions at said base ring and at said lip that produce a central energy maxima within said first area and a subsidiary energy maxima in said second area;
• a body of material to be heated positioned within said tray;
• a lid covering said open end of said tray and said body of material to be heated, said lid comprising microwave transparent material and a first, conductive, microwave opaque element, said element being separated from said side walls by a an annular area of said microwave transparent material and designed and adapted to enhance microwave intensity under said element;
• whereby said side walls, said base and said lid co-operate to produce more uniform heating within said container.