US 11,901,160 B2
Variable capacitor for RF power applications
Thomas Fink, Staufen (CH); Kevin Häuser, Karlsruhe (DE); Holger Maune, Darmstadt (DE); Daniel Kienemund, Klein-Gerau (DE); Joachim Binder, Karlsruhe (DE); Rolf Jakoby, Rosbach v. d. Höhe (DE); and Nicole Bohn, Karlsdorf-Neuthard (DE)
Assigned to Comet AG, Flamatt (CH)
Appl. No. 17/437,446
Filed by COMET AG, Flamatt (CH)
PCT Filed Mar. 3, 2020, PCT No. PCT/EP2020/055594
§ 371(c)(1), (2) Date Sep. 9, 2021,
PCT Pub. No. WO2020/182551, PCT Pub. Date Sep. 17, 2020.
Claims priority of application No. 19162035 (EP), filed on Mar. 11, 2019.
Prior Publication US 2022/0189739 A1, Jun. 16, 2022
Int. Cl. H01J 37/32 (2006.01); C04B 35/468 (2006.01); H01G 4/12 (2006.01); C04B 35/64 (2006.01); H01G 7/06 (2006.01)
CPC H01J 37/32183 (2013.01) [C04B 35/468 (2013.01); C04B 35/64 (2013.01); H01G 4/1218 (2013.01); H01G 7/06 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A radio-frequency (RF) power variable capacitor, capable of operating at at least 50 W, comprising at least two electrodes separated by a dielectric, wherein the capacitance of the capacitor is variable by varying a voltage, denoted by Vc, applied across the at least two electrodes, and wherein:
the dielectric comprises a high dielectric constant-low dielectric constant (HDK-NDK) composite ceramic;
the HDK component forms at least 80% by weight, of the material of the dielectric and comprises an active matrix wherein the active matrix comprises a HDK ferroelectric ceramic material, chosen from barium titanate, strontium titanate, barium-strontium titanate, calcium titanate and barium zirconate titanate;
the NDK component less than 20% by weight, of the dielectric and comprises an acoustic resonance reduction agent (ARRA), wherein the ARRA comprises a metal oxide ceramic which is stable at 1200° C., and wherein the ARRA is distributed throughout the active matrix; and
the active matrix material has a mean grain size between 1.5 μm and 5 μm.