Ferroelectric varactors suitable for capacitive shunt switching
First Claim
1. A frequency selective filter, the filter comprising:
- at least two varactor shunt switches, wherein the varactor shunt switch comprises;
a substrate;
a patterned bottom metal layer deposited on said substrate;
a ferroelectric thin film is deposited on said patterned bottom metal layer; and
a top metal electrode deposited on said ferroelectric thin film, wherein said top metal electrode is patterned to form a coplanar waveguide transmission line, wherein the coplanar waveguide transmission lines of the at least two varactor shunt switches are connected in series.
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Abstract
A ferroelectric varactor suitable for capacitive shunt switching is disclosed. High resistivity silicon with a SiO2 layer and a patterned metallic layer deposited on top is used as the substrate. A ferroelectric thin-film layer deposited on the substrate is used for the implementation of the varactor. A top metal electrode is deposited on the ferroelectric thin-film layer forming a CPW transmission line. By using the capacitance formed by the large area ground conductors in the top metal electrode and bottom metallic layer, a series connection of the ferroelectric varactor with the large capacitor defined by the ground conductors is created. The large capacitor acts as a short to ground, eliminating the need for vias. The varactor shunt switches can be used to create a bandpass filter and a tunable notch filter. The bandpass filter is implemented by cascading the switches, and the bandpass filter implemented through the use of a resonance circuit.
25 Citations
13 Claims
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1. A frequency selective filter, the filter comprising:
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at least two varactor shunt switches, wherein the varactor shunt switch comprises;
a substrate;
a patterned bottom metal layer deposited on said substrate;
a ferroelectric thin film is deposited on said patterned bottom metal layer; and
a top metal electrode deposited on said ferroelectric thin film, wherein said top metal electrode is patterned to form a coplanar waveguide transmission line, wherein the coplanar waveguide transmission lines of the at least two varactor shunt switches are connected in series. - View Dependent Claims (2, 3, 4, 5)
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6. A notch filter, the notch filter comprising:
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at least two varactor shunt switches, wherein the varactor shunt switch comprises;
a substrate;
a patterned bottom metal layer deposited on said substrate;
a functionalized polymer thin film is spin coated on said patterned bottom metal layer; and
a top metal electrode deposited on said ferroelectric thin film, wherein said top metal electrode is patterned to form a coplanar waveguide transmission line, wherein the coplanar waveguide transmission lines of the at least two varactor shunt switches are connected in series. - View Dependent Claims (7, 8, 9, 10)
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11. A method of selective filtering a frequency, the method comprising:
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depositing an adhesion layer on a substrate;
depositing a pattern bottom metal layer on said adhesion layer;
covering said pattern bottom metal layer with a layer of thin film, wherein said pattern bottom metal layer comprises of at least two ground conductors and a shunt conductor;
topping said layer of thin film with a top metal electrode, wherein said top metal electrode comprises of at least two ground conductors and a center signal strip to form a varactor shunt switch; and
connecting the center signal strip in series to a center signal strip of another varactor shunt switch. - View Dependent Claims (12)
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13. A method of notch filtering a frequency, the method comprising:
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depositing an adhesion layer on a substrate;
depositing a pattern bottom metal layer on said adhesion layer;
covering said pattern bottom metal layer with a layer of thin film, wherein said pattern bottom metal layer comprises of at least two ground conductors and a shunt conductor;
topping said layer of thin film with a top metal electrode, wherein said top metal electrode comprises of at least two ground conductors and a center signal strip to form a varactor shunt switch; and
connecting the center signal strip in series to a center signal strip of another varactor shunt switch.
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Specification