Patent EA-003062-B1 (EA)
Title: Ferroelectric varactor with built-in blocks
Inventor: SENGUPTA LOUISE C
IPC: H01G7/00
Filed: 1999-11-04
Abstract: 1. A voltage tunable dielectric varactor assembly (10) comprising a tunable ferroelectric layer (16) and first and second electrodes (18, 20) positioned adjacent to the tunable ferroelectric layer forming a tunable capacitor, characterized by: a first non-tunable dielectric layer (34) positioned adjacent to the first electrode; a third electrode (38) positioned adjacent to the first non-tunable dielectric layer, said third and first electrodes and said first non-tunable dielectric layer forming a first DC blocking capacitor; a second non-tunable dielectric layer (36) positioned adjacent to the second electrode; and a fourth electrode (44) positioned adjacent to the second non-tunable dielectric layer, said fourth and second electrodes and said second non-tunable dielectric layer forming a second DC blocking capacitor. 2. A voltage tunable dielectric varactor assembly (10) as recited in claim 1, wherein the capacitance between said first and second electrodes is less that the capacitance between sand first and third electrodes by a factor of at least about 20. 3. A voltage tunable dielectric varactor assembly (10) as recited in claim 1, wherein the tunable ferroelectric layer has a permittivity in a range from about 20 to about 2000. 4. A voltage tunable dielectric varactor assembly (10) as recited in claim 1, further comprising a substrate (12) for supporting said tunable ferroelectric layer and said first and second non-tunable dielectric layers. 5. A voltage tunable dielectric varactor assembly (10) as recited in claim 4, wherein the substrate comprises one of the group of: MgO, Alumina, LaAlO3, sapphire, and a ceramic. 6. A voltage tunable dielectric varactor assembly (10) as recited in claim 4, wherein: the substrate includes generally planar surface; the tunable ferroelectric layer is positioned on the generally planar surface of the substrate; the first and second electrodes are positioned on a surface of the tunable ferroelectric layer opposite the generally planar surface of the substrate, said first and second electrodes being separated to form a gap therebetween; the first and second non-tunable dielectric layers are positioned on the generally planar surface of the substrate; the third electrode is positioned on a surface of the first non-tunable dielectric layer opposite the generally planar surface of the substrate, said third and first electrodes being separated to form a second gap therebetween; and the fourth electrode is positioned on a surface of the second non-tunable dielectric layer opposite the generally planar surface of the substrate, said fourth and second electrodes being separated to form a third gap therebetween. 7. A voltage tunable dielectric varactor assembly (10) as recited in claim 6, wherein said second and third gaps are interdigital gaps. 8. A voltage tunable dielectric varactor assembly (10) as recited in claim 1, wherein the tunable ferroelectric layer comprises a barium strontium titanate composite ceramic. 9. A voltage tunable dielectric varactor assembly (10) as recited in claim 1, wherein the tunable ferroelectric layer comprises BSTO-MgO, BSTO-Al2O4, BSTO-CaTiO3, BSTO-MgSrZrTiO6, or combinations thereof. 10. A voltage tunable dielectric varactor assembly (10) as recited in claim 1, wherein the tunable ferroelectric layer has a tunability in a range from about 10% to about 80%. 11. A voltage tunable dielectric varactor assembly as recited in claim 7, wherein the tunable ferroelectric layer comprises one of: a tunable ferroelectric thick film; a tunable ferroelectric bulk ceramic; and a tunable ferroelectric thin film. 12. A voltage tunable dielectric varactor assembly (56) comprising a tunable ferroelectric layer (68) and first and second electrodes (60, 62) positioned on opposite sides of the tunable ferroelectric layer, characterized by: first and second non-tunable dielectric layers (74, 76), wherein the first nontunable layer is positioned adjacent to the first electrode and wherein the second non-tunable layer is positioned adjacent to the second electrode; a third electrode (80) positioned adjacent to a surface of the first nontunable dielectric layer opposite the first electrode; and a fourth electrode (78) positioned adjacent to a surface of the second nontunable dielectric layer opposite the second electrode. 13. A voltage tunable dielectric varactor assembly (56) as recited in claim 12, wherein the capacitance between said first and second electrodes is less that the capacitance between said first and third electrodes by a factor of at least about 20. 14. A voltage tunable dielectric varactor assembly (56) as recited in claim 12, wherein the tunable ferroelectric layer has a permittivity in a range from about 20 to about 2000. 15. A voltage tunable dielectric varactor assembly (56) as recited in claim 12, wherein the tunable ferroelectric layer has a tenability in a range from about 10% to about 80%. 16. A voltage tunable dielectric varactor assembly (56) as recited in claim 12, wherein the tunable ferroelectric layer comprises one of: a tunable ferroelectric thick film; a tunable ferroelectric bulk ceramic; and a tunable ferroelectric thin film. 17. A voltage tunable dielectric varactor assembly (56) as recited in claim 12, wherein said first and third electrodes and the first non-tunable dielectric layer form a first multilayer DC blocking capacitor (100); and said second and fourth electrodes and the second non-tunable dielectric layer form a second multilayer DC blocking capacitor (102). 18. A voltage tunable dielectric varactor assembly (56) as recited in claim 12, wherein the tunable ferroelectric layer comprises a barium strontium titanate composite ceramic. 19. A voltage tunable dielectric varactor assembly (56) as recited in claim 12, wherein the tunable ferroelectric layer comprises BSTO-MgO, BSTO-MgAl2O4, BSTO-CaTiO3, BSTO-MgTiO3, BSTO-MgSrZrTiO6, or combinations thereof.