# US 10,483,939 B2 · Downhole logging tool using resonant cavity antennas with real-time impedance matching > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,483,939 B2 - Document ID: US10483939B2 - Status: Granted - Kind: B2 - Application number: 15/765,671 - Filed: 2015-11-13 - Published: 2018-10-11 - Granted: 2019-11-19 - Earliest claimed: 2015-11-13 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: Li Pan; Luis Emilio San Martin; Rencheng Song - Web page: https://patentgrep.com/patent/US10483939B2 ## CPC - H03H 7/38: Impedance-matching networks - E21B 47/13: by electromagnetic energy, e.g. radio frequency - G01V 3/26: operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device (with electromagnetic waves G01V3/30) - G01V 3/30: operating with electromagnetic waves - H04B 1/0458: {Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages (matching circuits in general H03H)} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - H04B: TRANSMISSION ## Abstract A method of real-time impedance matching includes conveying a tool through a borehole where the tool includes a transmit cavity antenna and receive cavity antenna for transmitting and receiving signals through a subsurface formation. The tool also includes a cable for routing signals within the tool and at least one variable inductor or variable capacitor in an impedance-matching circuit. The method further includes measuring a reflection of a signal transmitted through the formation and determining a target impedance based on the impedance of the cable and the reflection. The method further includes adjusting the at least one variable inductor or variable capacitor such that the impedance of the matching circuit substantially equals the target impedance and receiving a signal from the formation via the adjusted impedance of the matching circuit. ## Claims ### Claim 1 A system for real-time impedance matching comprising: a transmit cavity antenna that transmits signals through a subsurface formation; an impedance-matching circuit comprising a variable inductor or a variable capacitor, wherein the impedance-matching circuit comprises three single pole triple throw switches, one throw on each switch coupled to a variable inductor, and another throw on each switch coupled to a variable capacitor; a cable that routes signals within the system; and a processor that: measures a reflection of a signal transmitted through the formation; determines a target impedance based on the impedance of the cable and the reflection; and adjusts the at least one variable inductor or capacitor such that the impedance of the matching circuit substantially equals the target impedance. ### Claim 2 (depends on 1) The system of claim 1, wherein adjusting the at least one variable inductor or variable capacitor causes the processor to select a circuit configuration to match the target impedance and adjust switches in the impedance-matching circuit such that the impedance-matching circuit mimics the selected circuit configuration. ### Claim 3 (depends on 2) The system of claim 2, wherein selecting the circuit configuration causes the processor to select the circuit configuration out of 8 potential circuit configurations, each comprising a variable inductor or variable capacitor. ### Claim 4 (depends on 1) The system of claim 1, wherein the switches are positioned such that every variable inductor and variable capacitor may be bypassed. ### Claim 5 (depends on 1) The system of claim 1, wherein the processor repeats said measuring, determining, and adjusting for different signal frequencies. ### Claim 6 (depends on 1) The system of claim 1, wherein the processor repeats said measuring, determining, and adjusting for different positions along a borehole. ### Claim 7 (depends on 1) The system of claim 1, wherein determining the target impedance, Zs, causes the processor to calculate Z S = Z 0 ⁡ ( - Γ S - 1 ) Γ S - 1 , where Z0 is the impedance of the cable and ΓS is the conjugate of the reflection. ### Claim 8 (depends on 1) The system of claim 1, wherein the cable is a coaxial cable. ### Claim 9 (depends on 1) The system of claim 1, wherein the tool is a high-frequency dielectric tool. ### Claim 10 A method of real-time impedance matching comprising: conveying a tool through a borehole, the tool comprising a transmit cavity antenna and receive cavity antenna for transmitting and receiving signals through a subsurface formation respectively, a cable for routing signals within the tool, and at least one variable inductor or variable capacitor in an impedance-matching circuit, wherein the impedance-matching circuit comprises three single pole triple throw switches, one throw on each switch coupled to a variable inductor, and another throw on each switch coupled to a variable capacitor; measuring a reflection of a signal transmitted through the formation; determining a target impedance based on the impedance of the cable and the reflection; and adjusting the at least one variable inductor or variable capacitor in such that the impedance of the impedance-matching circuit substantially equals the target impedance. ### Claim 11 (depends on 10) The method of claim 10, wherein adjusting the at least one variable inductor or variable capacitor further comprises selecting a circuit configuration to match the target impedance and adjusting switches in the impedance-matching circuit such that the impedance-matching circuit mimics the selected circuit configuration. ### Claim 12 (depends on 11) The method of claim 11, wherein selecting the circuit configuration comprises selecting the circuit configuration out of 8 potential circuit configurations, each comprising a variable inductor or variable capacitor. ### Claim 13 (depends on 10) The method of claim 10, further comprising repeating said measuring, determining, adjusting, and receiving at a different signal frequency. ### Claim 14 (depends on 10) The method of claim 10, further comprising repeating said measuring, determining, adjusting, and receiving at a different position along the borehole. ### Claim 15 (depends on 10) The method of claim 10, wherein determining the target impedance, Zs, comprises calculating Z S = Z 0 ⁡ ( - Γ S - 1 ) Γ S - 1 , where Z0 is the impedance of the cable and ΓS is the conjugate of the reflection. ### Claim 16 (depends on 10) The method of claim 10, further comprising logging data about the borehole based on the received signal. ### Claim 17 (depends on 10) The method of claim 10, wherein the reflection is a forward reflection and wherein the impedance-matching circuit is coupled to the transmit cavity antenna. ### Claim 18 (depends on 10) The method of claim 10, wherein the reflection is a backward reflection and wherein the impedance-matching circuit is coupled to the receive cavity antenna. ### Claim 19 (depends on 10) The method of claim 10, further comprising deriving a formation property based at least in part on received signals.