A tunable capacitor using an immiscible bifluidic dielectric

Author

Choi, S.O. ; Yoon, Y.K. ; Allen, M.G. ; Hunt, A.T.

Author_Institution

Sch. of Electr. & Comput. Eng., Georgia Inst. of Technol., Atlanta, GA, USA

Volume

2

fYear

2004

fDate

6-11 June 2004

Firstpage

873

Abstract

A tunable capacitor using two immiscible fluids of different dielectric constants as a dielectric material are investigated and the feasibility of its RF application is demonstrated. Large capacitance change is obtained when the two fluids have large differences of dielectric constant. When deionized water and air are used as the two fluids, the tunability (T[%]=100×(C_water-C_air)/C_air) shows a maximum of 6700% at low frequency. Silicone oil (dielectric constant of 2.5) and air is used for the high frequency application to ensure low dielectric loss in the RF frequency range. Nominal tunability and Q-factor at 2.5 GHz is 15.7% and 17.4, respectively. Barium strontium titanate (BST) nano powder mixture with silicone oil (43 wt% of BST) shows 12% more tunability than that of a pure silicone oil capacitor (due to the high permittivity contribution of BST) without concomitant Q-factor degradation. A tunable resonator consisting of the fluidic tunable capacitor combined with a line inductor is fabricated and a tuning bandwidth of 15% (0.27 GHz) is obtained at 1.8 GHz.

Keywords

Q-factor; barium compounds; capacitance; capacitors; cavity resonators; dielectric liquids; dielectric losses; dielectric resonators; microfluidics; micromechanical resonators; permittivity; silicones; strontium compounds; 0.27 GHz; 1.8 GHz; 2.5 GHz; BST; BaSrTiO₃; Q-factor; RF application; barium strontium titanate nanopowder mixture; capacitance; deionized water; dielectric constants; dielectric loss; fluidic tunable capacitor; immiscible bifluidic dielectrics; line inductor; microfluidics; permittivity; silicone oil capacitor; tunable resonator; tuning bandwidth; Barium; Binary search trees; Capacitance; Capacitors; Dielectric constant; Dielectric losses; Dielectric materials; Petroleum; Q factor; Radio frequency;

fLanguage

English

Publisher

ieee

Conference_Titel

Microwave Symposium Digest, 2004 IEEE MTT-S International

ISSN

0149-645X

Print_ISBN

0-7803-8331-1

Type

conf

DOI

10.1109/MWSYM.2004.1339108

Filename

1339108