# US 2017/0082468 A1 · Method and apparatus for interference reduction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0082468 A1 - Document ID: US20170082468A1 - Status: Published application - Kind: A1 - Application number: 15/268,911 - Filed: 2016-09-19 - Published: 2017-03-23 - Earliest claimed: 2015-09-21 - Assignees: ABB AB - Applicants: ABB Limited - Inventors: Ray KEECH - Web page: https://patentgrep.com/patent/US20170082468A1 ## CPC - G01F 1/584: {constructions of electrodes, accessories therefor} - G01F 1/60: Circuits therefor - H04L 25/08: Modifications for reducing interference; Modifications for reducing effects due to line faults {; Receiver end arrangements for detecting or overcoming line faults} - H04L 43/028: by filtering - H04L 5/06: the signals being represented by different frequencies (combined with time-division multiplexing H04L5/26) - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method and apparatus are for processing a periodic data-carrying signal to reduce periodic interference at either of a first fundamental frequency or a second fundamental frequency, the second fundamental frequency being different from the first fundamental frequency. The periodic data-carrying signal is derived from an excitation signal having an excitation frequency, the excitation frequency being a sub-multiple of the first fundamental frequency. The data-carrying signal is subjected to both a comb filter to reject interference at the first fundamental frequency, and an averaging/integrating filter to reject interference at the second fundamental frequency. A comb filter delay period is related to the first fundamental frequency and the averaging/integrating filter averages or integrates over a period related to the second fundamental frequency. ## Claims ### Claim 1 A method of processing a periodic data-carrying signal to reduce periodic interference at either of a first fundamental frequency or a second fundamental frequency, the second fundamental frequency being different from the first fundamental frequency, the periodic data-carrying signal being derived from an excitation signal having an excitation frequency, the excitation frequency being a sub-multiple of the first fundamental frequency, the method comprising: subjecting the data-carrying signal to both a comb filter operation to reject interference at the first fundamental frequency, and an averaging/integrating filter operation to reject interference at the second fundamental frequency; wherein the comb filter operation has a comb filter delay period related to the first fundamental frequency; and wherein the averaging/integrating filter operation averages or integrates over a period related to the second fundamental frequency. ### Claim 2 The method as claimed in claim herein the excitation frequency is given by: (the first fundamental frequency)/n, where n is an integer. ### Claim 3 (depends on 1) The method as claimed in claim 1, wherein the comb filter delay period is given by: 1/(2×the excitation frequency) or 1/(the excitation frequency) ### Claim 4 (depends on 1) The method as claimed in claim 1, wherein the averaging/integrating filter operation averages or integrates over a period given by: m/(the second fundamental frequency), where m is an integer. ### Claim 5 (depends on 1) The method as claimed in claim 1, wherein the comb filter operation further rejects interference at harmonics of the first fundamental frequency. ### Claim 6 (depends on 1) The method as claimed in claim 1, wherein the averaging/integrating filter operation further rejects interference at harmonics of the second fundamental frequency. ### Claim 7 (depends on 1) The method as claimed in claim 1, wherein the comb filter operation precedes the averaging/integrating filter operation. ### Claim 8 (depends on 1) The method as claimed in claim 1, wherein the averaging/integrating filter operation precedes the comb filter operation. ### Claim 9 (depends on 1) The method as claimed in claim 1, wherein the first fundamental frequency is 50 Hz and the second fundamental frequency is 60 Hz. ### Claim 10 (depends on 1) The method as claimed in claim 1, wherein the first fundamental frequency is 60 Hz and the second fundamental frequency is 50 Hz. ### Claim 11 (depends on 1) The method as claimed in claim 1, wherein the excitation signal has an alternating form, for example a form selected from a group comprising: a square wave, a non 50:50 pulse, a sine wave, a triangular wave, a saw-tooth wave. ### Claim 12 (depends on 1) The method as claimed in claim 1, wherein the data-carrying signal is produced by an electromagnetic flowmeter. ### Claim 13 (depends on 12) The method as claimed in claim 12, wherein the method is performed by said flowmeter. ### Claim 14 (depends on 1) The method as claimed in claim 1, wherein the method is performed by a signal processing device or a signal processing circuit separate from the device that produces the data-carrying signal. ### Claim 15 Apparatus for processing a periodic data-carrying signal to reduce periodic interference at either of a first fundamental frequency or a second fundamental frequency, the second fundamental frequency being different from the first fundamental frequency, the periodic data-carrying signal being derived from an excitation signal having an excitation frequency, the excitation frequency being a sub-multiple of the first fundamental frequency, the apparatus comprising: a comb filter in series with an averaging/integrating filter, wherein the comb filter is configured to reject interference at the first fundamental frequency from the data-carrying signal, and the averaging/integrating filter is configured to reject interference at the second fundamental frequency from the data-carrying signal; wherein the comb filter has a comb filter delay period related to the first fundamental frequency: and wherein the averaging/integrating filter is configured to average or integrate over a period related to the second fundamental frequency. ### Claim 16 (depends on 15) The apparatus as claimed in claim 15, wherein the excitation frequency is given by: (the first fundamental frequency)/n, where n is an integer. ### Claim 17 (depends on 15) The apparatus as claimed in claim 15, wherein the comb filter delay period is given by: 1/(2×the excitation frequency) or 1/(the excitation frequency). ### Claim 18 (depends on 15) The apparatus as claimed in claim 15, wherein the averaging/integrating filter is configured to average or integrate over a period given by: m/(the second fundamental frequency), where m is an integer. ### Claim 19 (depends on 15) The apparatus as claimed in claim 15, wherein the comb filter is further configured to reject interference at harmonics of the first fundamental frequency. ### Claim 20 (depends on 15) The apparatus as claimed in claim 15, wherein the averaging/integrating filter is further configured to reject interference at harmonics of the second fundamental frequency. ### Claim 21 (depends on 15) The apparatus as claimed in claim 15, wherein the comb filter precedes the averaging/integrating filter. ### Claim 22 (depends on 15) The apparatus as claimed in claim 15, wherein the averaging/integrating filter precedes the comb filter. ### Claim 23 (depends on 15) The apparatus as claimed in claim 15, wherein the first fundamental frequency is 50 Hz and the second fundamental frequency is 60 Hz. ### Claim 24 (depends on 15) The apparatus as claimed in claim 15, wherein the first fundamental frequency is 60 Hz and the second fundamental frequency is 50 Hz. ### Claim 25 (depends on 15) The apparatus as claimed in claim 15, wherein the excitation signal has an alternating form, for example a form selected from a group comprising: a square wave, a non 50:50 pulse, a sine wave, a triangular wave, a saw-tooth wave. ### Claim 26 (depends on 15) The apparatus as claimed in claim 15, further comprising a signal generator configured to generate the excitation signal. ### Claim 27 (depends on 26) The apparatus as claimed in claim 26 being an electromagnetic flowmeter, the data-carrying signal being produced by said flowmeter in use. ### Claim 28 (depends on 15) The apparatus as claimed in claim 15 being a signal processing device or a signal processing circuit operable to receive and process a data-carrying signal produced by a device such as an electromagnetic flowmeter. ### Claim 29 A method of processing a periodic data-carrying signal to reduce periodic interference at either of a first fundamental frequency or a second fundamental frequency, the second fundamental frequency being different from the first fundamental frequency, the periodic data-carrying signal being derived from an excitation signal having an excitation frequency, the excitation frequency being a sub-multiple of the first fundamental frequency, the method comprising: subjecting the data-carrying signal to both a comb filter operation to reject interference at the first fundamental frequency, and an averaging/integrating filter operation to reject interference at the second fundamental frequency. ### Claim 30 Apparatus for processing a periodic data-carrying signal to reduce periodic interference at either of a first fundamental frequency or a second fundamental frequency, the second fundamental frequency being different from the first fundamental frequency, the periodic data-carrying signal being derived from an excitation signal having an excitation frequency, the excitation frequency being a sub-multiple of the first fundamental frequency, the apparatus comprising: a comb filter in series with an averaging/integrating filter, wherein the comb filter is configured to reject interference at the first fundamental frequency from the data-carrying signal, and the averaging/integrating filter is configured to reject interference at the second fundamental frequency from the data-carrying signal.