# US 7,609,128 B2 · Switch circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,128 B2 - Document ID: US7609128B2 - Status: Granted - Kind: B2 - Application number: 11/802,360 - Filed: 2007-05-22 - Published: 2007-11-29 - Granted: 2009-10-27 - Earliest claimed: 2006-05-23 - Assignees: NEC Electronics Corporation - Inventors: Hiroshi Mizutani - Web page: https://patentgrep.com/patent/US7609128B2 ## CPC - H01P 1/15: by semiconductor devices - H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B) ## Abstract A branch path having a transmission line and a distributed constant line includes a resonant circuit. The resonant circuit resonates at a predetermined operating frequency when the branch path is in OFF state. At this time, the distributed constant line has a predetermined impedance. Further, an impedance of a node between the resonant circuit and distributed constant line can be set on a circle of a reflection coefficient 1 near short on the Smith chart. ## Claims ### Claim 1 A switch circuit, comprising: a first branch path provided between an input terminal and a first output terminal and including a first transmission line and a first distributed constant line; a second branch path provided between the input terminal and a second output terminal and including a second transmission line and a second distributed constant line; a first resonant circuit connected between the first transmission line and the first distributed constant line to resonate at a predetermined frequency while the first branch path is in OFF state; and a second resonant circuit connected between the second transmission line and the second distributed constant line to resonate at a predetermined frequency while the second branch path is in OFF state, wherein the first distributed constant line comprises a line of field effect transistor, which determines ON or OFF state of the first distributed constant line, the second distributed constant line comprises a line of field effect transistor, which determines ON or OFF state of the second distributed constant line. ### Claim 2 (depends on 1) The switch circuit according to claim 1, wherein the ON or OFF state of the field effect transistor included in the first and second distributed constant lines are determined based on a control signal from a control unit. ### Claim 3 (depends on 1) The switch circuit according to claim 1, wherein the first and second resonant circuits use a capacitance of a field effect transistor as a capacitor. ### Claim 4 (depends on 3) The switch circuit according to claim 3, wherein ON or OFF state of the field effect transistors included in the first and second resonant circuits are determined based on a control signal from a control unit. ### Claim 5 (depends on 1) The switch circuit according to claim 1, wherein the first and second resonant circuit use a capacitance of a diode as a capacitor. ### Claim 6 (depends on 5) The switch circuit according to claim 5, wherein a bias state of the diodes included in the first and second resonant circuits is determined based on a control signal from a control unit. ### Claim 7 A switch circuit, comprising: a first branch path provided between an input terminal and a first output terminal and including a first transmission line and a first distributed constant line; a second branch path provided between the input terminal and a second output terminal and including a second transmission line and a second distributed constant line; a first resonant circuit connected between the first transmission line and the first distributed constant line to resonate at a predetermined frequency while the first branch path is in OFF state; and a second resonant circuit connected between the second transmission line and the second distributed constant line to resonate at a predetermined frequency while the second branch path is in OFF state, wherein the first distributed constant line comprises a line of diode, which determines ON or OFF state of the first distributed constant line, and the second distributed constant line comprises a line of diode, which determines ON or OFF state of the second distributed constant line. ### Claim 8 (depends on 7) The switch circuit according to claim 7, wherein a bias state of the diode structure included in the first and second distributed constant lines is determined based on a control signal from a control unit. ### Claim 9 (depends on 8) The switch circuit according to claim 8, wherein the first and second resonant circuits use a capacitance of a field effect transistor as a capacitor. ### Claim 10 (depends on 9) The switch circuit according to claim 9, wherein ON or OFF state of the field effect transistors included in the first and second resonant circuits are determined based on a control signal from a control unit. ### Claim 11 (depends on 8) The switch circuit according to claim 8, wherein the first and second resonant circuit use a capacitance of a diode as a capacitor. ### Claim 12 (depends on 11) The switch circuit according to claim 11, wherein a bias state of the diodes included in the first and second resonant circuits is determined based on a control signal from a control unit. ### Claim 13 (depends on 1) The switch circuit according to claim 1, wherein the first and second resonant circuits use an inductance of the transmission line as an inductor. ### Claim 14 (depends on 1) The switch circuit according to claim 1, wherein the first and second resonant circuits use an inductance of a winding as an inductor. ### Claim 15 (depends on 1) The switch circuit according to claim 1, wherein the transmission line has a length of about λ/4, provided a propagated wavelength corresponding to a predetermined operational frequency band is λ. ### Claim 16 (depends on 7) The switch circuit according to claim 7, wherein the first and second resonant circuits use an inductance of the transmission line as an inductor. ### Claim 17 (depends on 7) The switch circuit according to claim 7, wherein the first and second resonant circuits use an inductance of a winding as an inductor. ### Claim 18 (depends on 7) The switch circuit according to claim 7, wherein the transmission line has a length of about λ/4, provided a propagated wavelength corresponding to a predetermined operational frequency band is λ.