# US 2018/0321332 A1 · Magnetic field detection device and magnetic field detection method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0321332 A1 - Document ID: US20180321332A1 - Status: Published application - Kind: A1 - Application number: 15/770,195 - Filed: 2016-10-20 - Published: 2018-11-08 - Earliest claimed: 2015-11-04 - Assignees: TDK Corporation - Applicants: TDK Corporation - Inventors: Kei TANABE - Web page: https://patentgrep.com/patent/US20180321332A1 ## CPC - G01R 33/091: {Constructional adaptation of the sensor to specific applications} - G01R 33/0023: {Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration (G01R33/0017 takes precedence)} - G01R 33/025: Compensating stray fields {(G01R33/0017 takes precedence)} - G01R 33/09: Magnetoresistive devices - G01R 33/093: {using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00)} - G01R 33/095: {extraordinary magnetoresistance sensors} - A61B 5/05: Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves (measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract An object of the present invention is to selectively detect a detection magnetic field without separately providing a sensor for detecting an environmental magnetic field. A magnetic field detection device includes a magnetic field detection unit 10 that generates an output signal S1 according to a magnetic field, a first signal generation unit 20 that extracts a predetermined frequency component from the output signal S1 and generates a cancel signal S2 based on the predetermined frequency component, a first magnetic field generation unit 40 that applies a first cancel magnetic field to the magnetic field detection unit 10 based on the cancel signal S2, and a second signal generation unit 30 that generates a detection signal S3 based on the output signal S1 of the magnetic field detection unit 10 to which the first cancel magnetic field is applied. According to the present invention, a cancel signal is generated based on a frequency component of an output signal, and a first cancel magnetic field is applied to a magnetic field detection unit using the cancel signal. Therefore, it is not necessary to separately provide a sensor for detecting an environmental magnetic field. Because this configuration reduces the number of parts, downsizing and cost reduction can be realized. ## Claims ### Claim 1 A magnetic field detection device comprising: a magnetic field detection unit that generates an output signal according to a magnetic field; a first signal generation unit that extracts a predetermined frequency component from the output signal and generates a cancel signal based on the predetermined frequency component; a first magnetic field generation unit that applies a first cancel magnetic field to the magnetic field detection unit based on the cancel signal; and a second signal generation unit that generates a detection signal based on the output signal of the magnetic field detection unit to which the first cancel magnetic field is applied. ### Claim 2 (depends on 1) The magnetic field detection device as claimed in claim 1, wherein the predetermined frequency component includes a DC component. ### Claim 3 (depends on 1) The magnetic field detection device as claimed in claim 1, wherein the first signal generation unit includes a low-pass filter, a band elimination filter, a high-pass filter, or a band-pass filter. ### Claim 4 (depends on 1) The magnetic field detection device as claimed in claim 1, wherein the first signal generation unit includes an A/D converter that converts the output signal into a digital signal, and a digital filter that processes the digital signal. ### Claim 5 (depends on 1) The magnetic field detection device as claimed in claim 1, wherein the first magnetic field generation unit includes a first coil, and wherein the magnetic field detection unit is placed in an inner diameter portion of the first coil. ### Claim 6 (depends on 1) The magnetic field detection device as claimed in claim 1, further comprising a second magnetic field generation unit that applies a second cancel magnetic field to the magnetic field detection unit based on the output signal of the magnetic field detection unit to which the first cancel magnetic field is applied. ### Claim 7 (depends on 6) The magnetic field detection device as claimed in claim 6, wherein the magnetic field detection unit includes a magnetic field detection element that converts the magnetic field into a potential difference, and a first amplification circuit that amplifies the potential difference to generate the output signal. ### Claim 8 (depends on 7) The magnetic field detection device as claimed in claim 7, wherein the magnetic field detection element and the second magnetic field generation unit are integrated on a same sensor chip. ### Claim 9 (depends on 8) The magnetic field detection device as claimed in claim 8, wherein the first magnetic field generation unit is further integrated on the sensor chip. ### Claim 10 (depends on 7) The magnetic field detection device as claimed in claim 7, wherein the magnetic field detection unit further includes a second amplification circuit that is provided separately from the first amplification circuit and that amplifies the potential difference to generate the detection signal. ### Claim 11 A magnetic field detection method comprising: detecting a synthetic magnetic field having an environmental magnetic field superimposed on a detection magnetic field to generate an output signal; extracting a frequency component corresponding to the environmental magnetic field from the output signal to generate a cancel signal; and canceling the environmental magnetic field based on the cancel signal to extract a component corresponding to the detection magnetic field from the output signal.