Dielectric substrate with selectively controlled effective permittivity and loss tangent

1. A substrate for an RF device, comprising:

a plurality of layers of dielectric material cofired in a stack, each of said plurality of layers formed from a material having a permittivity and having a pattern of perforations formed in at least one perforated area; and

said perforated areas of each respective one of said plurality of layers at least partially aligned with one another in said stack to lower at least one of an effective value of a permittivity and a loss tangent in at least one spatially defined region of said substrate, wherein said effective permittivity varies in a predetermined manner across a surface of said substrate defined by said spatially defined region in accordance with a variation of said pattern of said perforations.

2. The substrate according to claim 1 wherein said plurality of layers are comprised of a ceramic tape.

3. The substrate according to claim 1 wherein said plurality of layers are comprised of a low temperature type cofired ceramic tape.

4. The substrate according to claim 1 wherein said perforations of each said perforated area are aligned with one another.

5. The substrate according to claim 1 wherein said pattern of perforations is excluded from at least one outermost layer of said substrate.

6. A substrate for an RF device, comprising:

a plurality of layers of dielectric material cofired in a stack, each of said plurality of layers formed from a material having a permittivity and having a pattern of perforations formed in at least one perforated area; and

said perforated areas of each respective one of said plurality of layers at least partially aligned with one another in said stack to lower at least one of an effective value of a permittivity and a loss tangent in at least one spatially defined region of said substrate, wherein said pattern of perforations for each of said plurality of layers is arranged so that said effective value of permittivity is substantially the same at each measurable point of said spatially defined region of said substrate.

7. The substrate according to claim 1 wherein said pattern of perforations is varied among said plurality of layers.

8. The substrate according to claim 1 wherein said pattern of perforations is offset from layer to layer.

9. The substrate according to claim 1 wherein said pattern of perforations is formed in a plurality of said perforated areas of each said layer to produce a plurality of said spatially defined regions, each having at least one of an effective value of permittivity and a loss tangent lower than a permittivity and loss tangent for said dielectric material.

10. The substrate according to claim 9 wherein said pattern of perforations in said plurality of perforated areas produces different values for at least one of said effective permittivity and said loss tangent in at least a first one of said spatially defined regions as compared to at least a second one of said spatially defined regions.

11. A substrate for an RF device, comprising:

a plurality of layers of dielectric material cofired in a stack, each of said plurality of layers formed from a material having a permittivity and having a pattern of perforations formed in at least one perforated area; and

said perforated areas of each respective one of said plurality of layers at least partially aligned with one another in said stack to lower at least one of an effective value of a permittivity and a loss tangent in at least one spatially defined region of said substrate, wherein said pattern of perforations in each of said layers causes said effective permittivity to selectively vary in a predetermined manner across a surface of said substrate defined by said spatially defined region.