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Electrically tunable electromagnetic bandgap ("TEBG") structures using a ferroelectric thin film on a semiconductor substrate, tunable devices that include such a TEBG structure, such as a monolithic microwave integrated circuit ("MMIC"), and a method producing such a TEBG structure are disclosed. T

Electrically tunable electromagnetic bandgap ("TEBG") structures using a ferroelectric thin film on a semiconductor substrate, tunable devices that include such a TEBG structure, such as a monolithic microwave integrated circuit ("MMIC"), and a method producing such a TEBG structure are disclosed. The present invention provides a semiconductive substrate having an oxide layer, a first conductive layer positioned on the oxide layer, a ferroelectric layer covering the first conductive layer, and a second conductive layer positioned on a surface of the tunable ferroelectric layer. The use of the ferroelectric layer, which have a DC electric field dependent permittivity, enables a small size, tunable EBG structure.

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What is claimed is: 1. An electrically tunable electromagnetic band gap structure comprising: a semiconductive substrate having an oxide layer and having generally a planar surface; a signal strip provided on the generally planar surface of the oxide layer; a tunable ferroelectric layer; and a patt

What is claimed is: 1. An electrically tunable electromagnetic band gap structure comprising: a semiconductive substrate having an oxide layer and having generally a planar surface; a signal strip provided on the generally planar surface of the oxide layer; a tunable ferroelectric layer; and a patterned metal layer having ground lines and an electrode on a surface of the tunable ferroelectric layer, said ground lines and said electrode being separated by a gap, and said signal strip and said electrode being separated by the tunable ferroelectric layer provided therebetween. 2. An electrically tunable electromagnetic bandgap structure as recited in claim 1, further comprising a pair of inductive strips provided on a generally planar surface of said tunable ferroelectric layer adjacent said electrode, each said pair of inductive strips and said electrode being separated by a spacing therebetween. 3. An electrically tunable electromagnetic band gap structure as recited in claim 1, further comprising a pair of inductive strips provided on a generally planar surface of said tunable ferroelectric layer adjacent said electrode, each said pair of inductive strips and said electrode being separated by a spacing therebetween, said pair of inductive strip being integral with a respective ground plane, said ground plane having a bottom electrode coplanar with said signal strip and being separated by a slotwidth therebetween. 4. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein the tunable ferroelectric layer has a permittivity greater than about 200. 5. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein the oxide layer has a permittivity of less than about 4. 6. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein the tunable ferroelectric layer has a permittivity in a range from about 200 to about 2000, and a tunability in a range from about 10% to about 80% at a bias voltage of about 10 V/μm. 7. An electrically tunable electromagnetic band gap structure as recited in claim 1, wherein the substrate comprises silicon, and said oxide layer is silicon dioxide. 8. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein the tunable ferroelectric layer comprises a perovskite. 9. An electrically tunable electromagnetic band gap structure as recited in claim 1, wherein the tunable ferroelectric layer comprise Barium-Strontium Titanate, BaxSr1-xTiO3 (BSTO), where x can range from zero to one. 10. An electrically tunable electromagnetic band gap structure as recited in claim 1, wherein the tunable ferroelectric layer comprise a BSTO-composite ceramic. 11. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein the tunable ferroelectric layer comprise BSTO--MgO, BSTO--MgAl2O4, BSTO--CaTiO3, BSTO--MgTiO3, BSTO--MgSrZrTiO6, and combinations thereof. 12. An electrically tunable electromagnetic bandgap structure as recited in claim 1, further comprising an RF input and an RF output for passing an RF signal through the signal strip under said electrode and in between said tunable ferroelectric layer and said oxide layer. 13. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein said electrode and signal strip comprises platinum, gold, copper, silver, aluminum, other Periodic Table Group I, III, and VIII elements, and combinations thereof. 14. An electrically tunable electromagnetic bandgap structure as recited in claim 1, provided in a monolithic microwave integrated circuit. 15. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein said structure is used in a reflective antenna. 16. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein said structure is used as a ground plane for a microstrip circuit. 17. An electrically tunable electromagnetic bandgap structure as recited in claim 1, wherein said structure is used as a frequency selective surface ("FSS") for spatial filtering. 18. A method of forming an electrically tunable electromagnetic bandgap structure, said method comprising: providing a semiconductive substrate having an oxide layer and having generally a planar surface; providing a signal strip on said generally planar surface of the oxide layer; providing a tunable ferroelectric layer; and providing a patterned metal layer having ground lines and an electrode on a surface of the tunable ferroelectric layer, said ground lines and said electrode being separated by a gap, and said signal strip and said electrode being separated by the tunable ferroelectric layer provided therebetween. 19. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, further comprises providing a pair of inductive strips on a generally planar surface of said tunable ferroelectric layer adjacent said electrode, each said pair of inductive strips and said electrode being separated by a spacing therebetween. 20. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, further comprises providing a pair of inductive strips on a generally planar surface of said tunable ferroelectric layer adjacent said electrode, each said pair of inductive strips and said electrode being separated by a spacing therebetween, said pair of inductive strip being integral with a respective ground plane, said ground plane having a bottom electrode coplanar with said signal strip and being separated by a slotwidth therebetween. 21. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the tunable ferroelectric layer has a permittivity greater than about 200. 22. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the oxide layer has a permittivity of less than about 4. 23. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the tunable ferroelectric layer has a permittivity in a range from about 200 to about 2000, and a tunability in a range from about 10% to about 80% at a bias voltage of about 10 V/μm. 24. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the substrate comprises silicon, and said oxide layer is silicon dioxide. 25. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the tunable ferroelectric layer comprises a perovskite. 26. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the tunable ferroelectric layer comprise Barium-Strontium Titanate, Ba xSr1-xTiO3 (BSTO), where x can range from zero to one. 27. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the tunable ferroelectric layer comprise a BSTO-composite ceramic. 28. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein the tunable ferroelectric layer comprise BSTO--MgO, BSTO--MgAl2O 4, BSTO--CaTiO3, BSTO--MgTiO3, BSTO--MgSrZrTiO 6, and combinations thereof. 29. The method of forming an electrically tunable electromagnetic band gap structure as recited in claim 18, further comprises providing an RF input and an RF output for passing an RF signal through the signal strip under said electrode and in between said tunable ferroelectric layer and said oxide layer. 30. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, wherein said electrode and signal strip comprises platinum, gold, copper, silver, aluminum, other Periodic Table Group I, III, and VIII elements, and combinations thereof. 31. The method of forming an electrically tunable electromagnetic band gap structure as recited in claim 18, further comprises including said structure in a monolithic microwave integrated circuit. 32. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, further comprises including said structure in a reflective antenna. 33. The method of forming an electrically tunable electromagnetic bandgap structure as recited in claim 18, further comprises using said structure used as a ground plane for a microstrip circuit. 34. The method of forming an electrically tunable electromagnetic band gap structure as recited in claim 18, further comprises using said structure as a frequency selective surface ("FSS") for spatial filtering. 35. An electrically tunable electromagnetic bandgap structure comprising: a substrate having a first permittivity and having a generally planar surface; first, second, and third electrodes positioned on the generally planar surface of the substrate, said first, second, and third electrodes being separated to form a pair of first gaps therebetween; a tunable dielectric layer positioned on the first, second, and third electrodes and in said first gaps, the tunable dielectric layer having a second permittivity greater than said first permittivity, and said second electrode being a signal strip; and fourth, fifth, and sixth electrodes positioned on a surface of the tunable dielectric layer, said fourth, fifth, and sixth electrodes being opposite the first, second, and third electrodes, and said fourth, fifth, and sixth electrodes being separated by a second gap therebetween. 36. An electrically tunable electromagnetic bandgap structure as recited in claim 35, wherein said second gap is narrower than said each one of said pair of first gaps. 37. An electrically tunable electromagnetic bandgap structure as recited in claim 35, wherein said second permittivity is in a range from about 200 to 2000, and tunability of the tunable dielectric layer is in a range from about 10% to about 80%. 38. An electrically tunable electromagnetic bandgap structure as recited in claim 35, wherein said first permittivity is less than about 4. 39. An electrically tunable electromagnetic bandgap structure as recited in claim 35, wherein said electrodes each comprise one of the group of platinum, gold, copper, silver, aluminum, other Periodic Table Group I, III, and VIII elements, and combinations thereof. 40. An electrically tunable electromagnetic bandgap structure as recited in claim 35, wherein the tunable ferroelectric layer comprises a perovskite. 41. An electrically tunable electromagnetic bandgap structure as recited in claim 35, further including an RF input and an RF output for passing an RF signal through the tunable dielectric layer in a first direction, and wherein the first and second gaps lie parallel to the first direction. 42. An electrically tunable electromagnetic bandgap structure as recited in claim 35, wherein said second and fifth electrodes are aligned vertically and have a similar width w.