# US 9,520,632 B2 · CMOS band-pass filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,632 B2 - Document ID: US9520632B2 - Status: Granted - Kind: B2 - Application number: 14/166,755 - Filed: 2014-01-28 - Published: 2014-09-18 - Granted: 2016-12-13 - Earliest claimed: 2013-03-15 - Assignees: Tiawan Semiconductor Manufacturing Co., Ltd. - Applicants: Taiwan Semiconductor Manufacturing Company Limited - Inventors: Jun-De Jin; Tzu-Jin Yeh; Chewn-Pu Jou - Web page: https://patentgrep.com/patent/US9520632B2 ## CPC - H01P 1/207: Hollow waveguide filters (H01P1/212, H01P1/213, H01P1/215, H01P1/219 take precedence) - H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B) ## Abstract A band-pass filter is provided that is configured to output a signal with a frequency within a desired frequency range and to attenuate signals with frequencies outside the desired frequency range. The band-pass filter comprises a CMOS resonator that comprises a resonator cavity and a reflector. The band-pass filter also comprises an impedance convertor that is configured to inhibit at least some insertion losses on the band-pass filter. The band-pass filter also comprises a variable capacitor that is connected between the CMOS resonator and the impedance convertor. The desired frequency range of the band-pass filter can be tuned by adjusting the capacitance of the variable capacitor. ## Claims ### Claim 1 A band-pass filter, comprising: a first impedance converter connected to an input terminal and comprising a first transformer having a primary winding and a secondary winding; a second impedance converter connected to an output terminal; and a resonator connected to the first impedance converter via the first transformer and connected to the second impedance converter, the resonator comprising: a substrate; a first reflector comprising a first material disposed within a first trench in the substrate, the substrate surrounding sidewalls and a bottom surface of the first material; and a resonator cavity comprising: a second material disposed within a second trench in the substrate, the second material defining an inner trench; and a second instance of the first material disposed within the inner trench, wherein: the input terminal is connected to the primary winding of the first transformer and the resonator is connected to the secondary winding of the first transformer; and there is no current path from the input terminal to the resonator. ### Claim 2 (depends on 1) The band-pass filter of claim 1, the second impedance converter comprising a second transformer. ### Claim 3 (depends on 2) The band-pass filter of claim 2, the second transformer comprising: a primary winding connected to the resonator; and a secondary winding connected to the output terminal. ### Claim 4 (depends on 3) The band-pass filter of claim 3, the second impedance converter comprising a second capacitor connected in parallel with the secondary winding of the second transformer. ### Claim 5 (depends on 3) The band-pass filter of claim 3, comprising a second variable capacitor connected in series with the primary winding of the second transformer. ### Claim 6 (depends on 1) The band-pass filter of claim 1, the first impedance converter comprising a first capacitor connected in parallel with the primary winding of the first transformer. ### Claim 7 (depends on 6) The band-pass filter of claim 6, comprising a first variable capacitor connected in series with the secondary winding of the first transformer. ### Claim 8 (depends on 1) The band-pass filter of claim 1, the resonator comprising: a second reflector. ### Claim 9 (depends on 8) The band-pass filter of claim 8, at least one of the first reflector comprising a first acoustic Bragg reflector; or the second reflector comprising a second acoustic Bragg reflector. ### Claim 10 (depends on 1) The band-pass filter of claim 1, the resonator cavity comprising an n-type dopant in a first portion of the substrate, wherein the second material is in contact with the first portion of the substrate and in contact with an undoped portion of the substrate. ### Claim 11 (depends on 10) The band-pass filter of claim 10, wherein the n-type dopant is arsenic. ### Claim 12 (depends on 1) The band-pass filter of claim 1, comprising a first variable capacitor connected between the secondary winding of the first transformer and the resonator. ### Claim 13 (depends on 12) The band-pass filter of claim 12, comprising a second variable capacitor connected between the second impedance converter and the resonator, a capacitance of the second variable capacitor substantially matched to a capacitance of the first variable capacitor. ### Claim 14 (depends on 1) The band-pass filter of claim 1, the first material comprising tungsten. ### Claim 15 (depends on 1) The band-pass filter of claim 1, the first material comprising tungsten and the second material comprising silicon nitride. ### Claim 16 A band-pass filter, comprising: a CMOS resonator comprising a first reflector and a resonator cavity, the resonator cavity comprising: a substrate comprising a doped region and defining a first trench at a first end of the doped region and a second trench at a second end of the doped region opposite the first end, the first trench and the second trench having depths that exceed a depth of the doped region; and a first material, different than the substrate, disposed within the first trench and the second trench; and a first impedance converter. ### Claim 17 (depends on 16) The band-pass filter of claim 16, the first reflector comprising a first acoustic Bragg reflector. ### Claim 18 (depends on 16) The band-pass filter of claim 16, the first reflector comprising tungsten disposed within a third trench defined by the substrate, the substrate surrounding sidewalls and a bottom surface of the tungsten. ### Claim 19 (depends on 16) The band-pass filter of claim 16, wherein the first material defines a first inner trench within the first trench and a second inner trench within the second trench, and tungsten is disposed within the first inner trench and the second inner trench. ### Claim 20 A band-pass filter, comprising: a CMOS resonator comprising a first reflector and a resonator cavity, wherein: the resonator cavity comprises: a first material disposed within a first trench and a second trench defined by a substrate, the first material defining a first inner trench within the first trench and a second inner trench within the second trench; a second material disposed within first inner trench and the second inner trench; and a doped region of the substrate between the first trench and the second trench, wherein the doped region of the substrate contacts a first sidewall of the first material and an undoped region of the substrate contacts a second sidewall of the first material; and the first reflector comprises: the second material disposed within a third trench and a fourth trench defined by the substrate.