Tunable bridged-T filter
AssigneeMotorola, Inc.
InventorGilberto J. Hernandez
Life of this patent
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Abstract
A tunable filter (300) includes first (302) and second (304) “bridged-T” resonators. The first (302) and second (304) resonators are capacitively coupled together via bandwidth control/coupling section (306). A biasing section (314) provides the proper biasing and decoupling for the filter (300). Filter (300) provides for low-side injection mode operation, and provides for a very deep zero on the lower side of the passband resulting in excellent selectivity. Filter (300) provides for excellent selectivity while reducing the number of inductors and varactors needed in the filter circuit. A high side injection mode filter (500) similar to filter (300) is also described in the disclosure.
Claims8
A tunable filter, comprising:
- first and second bridged-T resonator sections;
- and
- a coupling section that couples the first bridged-T resonator section to the second bridged-T resonator section;
- wherein the first bridged-T resonator section comprises:
- an input port;
- a varactor having first and second terminals;
- a first capacitor coupled between the input port and the first terminal of the varactor;
- an inductor coupled between the second terminal of the varactor and a ground;
- and
- a second capacitor coupled between the second terminal of the varactor and the coupling section.
Dependencies are inferred from the claim text.