# US 11,308,291 B2 · Methods and apparatus for radio frequency sensing in diverse environments > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,308,291 B2 - Document ID: US11308291B2 - Status: Granted - Kind: B2 - Application number: 17/079,494 - Filed: 2020-10-25 - Published: 2021-04-15 - Granted: 2022-04-19 - Earliest claimed: 2018-10-13 - Assignees: Massachusetts Institute of Technology - Applicants: Massachusetts Institute of Technology - Inventors: Unsoo Ha; Junshan Leng; Alaa Khaddaj; Yunfei Ma; Tzu Ming Hsu; Zexuan Zhong; Fadel Adib - Web page: https://patentgrep.com/patent/US11308291B2 ## CPC - G06K 7/0008: {General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer} - G06K 19/07771: {the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object} - G06K 7/10009: {sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves} - G06K 17/0022: {arrangements or provisions for transferring data to distant stations, e.g. from a sensing device ("transfer between computer elements G06F13/00 "; data-transmission H04L)} - G06K 19/0723: {the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs} - G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS ## Abstract A system may sense the contents of a closed container, by analyzing a wireless signal that reflects from an RFID tag on the outside of the container. The frequency response of the tag's antenna may be affected by the relative permittivity of the contents and by the tag's environment. The frequency response may be measured in a line-of-sight environment and in a multipath environment. Channel estimates may be calculated, based on the measurements. Channel ratios may be calculated by dividing line-of-sight channel estimates by multipath channel estimates. The resulting channel ratios may be fed into a variational autoencoder, which in turn generates synthetic data that contains information about multipath environments but not the contents. The output of the variational autoencoder may be converted into synthetic channel estimates, which may in turn be employed for anomaly detection, or to train a classifier to classify contents of the container. ## Claims ### Claim 1 An apparatus for sensing content of a closed container without opening the container, the apparatus comprising: (a) a radio frequency transceiver; and (b) one or more computers; wherein (i) the radio frequency transceiver is configured to take measurements of a frequency response of an antenna, in such a way that a first subset of the measurements is taken while the radio frequency transceiver is in a first set of environments, and a second subset of the measurements is taken while the radio frequency transceiver is in a second set of environments, (ii) the frequency response comprises amplitude and phase of radiation that is reflected by the antenna at each frequency in a set of frequencies, and depends in part on permittivity of a material that does not physically touch the antenna and that is within a distance from the antenna, which distance is less than two wavelengths of a highest frequency in the set of frequencies, (iii) the antenna and the material are not part of, and do not physically touch, the apparatus, and (iv) the one or more computers are programmed to recognize, estimate or classify the material, based on the measurements of the frequency response, to calculate, based on the first subset of measurements, a first set of channel estimates of respective signal channels in the first set of environments, to calculate, based on the second subset of measurements, a second set of channel estimates of respective signal channels in the second set of environments, and to extract, from the first and second sets of channel estimates, information about the second set of environments, which information is not affected by the material; wherein the information comprises the content of the closed container without opening the container. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the antenna is part of a backscatter node. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the antenna is part of a radio frequency identification tag. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the second subset of measurements is affected, to a greater extent than is the first subset of measurements, by reflection of radio waves from surfaces other than the antenna. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the second subset of measurements is affected by multipath propagation more than is the first subset of measurements. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the material is solid. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the material is liquid. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the radio frequency transceiver is configured to transmit the radiation at each frequency in the set of frequencies, by performing frequency hopping. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the radio frequency transceiver is configured to transmit the radiation at each frequency in the set of frequencies, by performing orthogonal frequency-division multiplexing. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein: (A) the material is inside a closed container; and (B) the antenna and the apparatus are outside of the closed container. ### Claim 11 A method for sensing content of a closed container without opening the container, the method comprising: (a) taking measurements, with a radio frequency transceiver, of a frequency response of an antenna, in such a way that a first subset of the measurements is taken while the radio frequency transceiver is in a first set of environments, and a second subset of measurements is taken while the radio frequency transceiver is in a second set of environments; and (b) performing calculations to recognize, estimate or classify a material, based on the measurements of the frequency response, to calculate, based on the first subset of the measurements, a first set of channel estimates of respective signal channels in the first set of environments, to calculate, based on the second subset of the measurements, a second set of channel estimates of respective signal channels in the second set of environments, and to extract, from the first and second sets of channel estimates, information about the second set of environments, which information is not affected by the material; wherein (i) the frequency response comprises amplitude and phase of radiation that is reflected by the antenna at each frequency in a set of frequencies, and depends in part on permittivity of a material that does not physical touch the antenna and that is within a distance from the antenna, which distance is less than two wavelengths of a highest frequency in the set of frequencies, (ii) the antenna and material do not physically touch the radio frequency transceiver; and (iii) wherein the information comprises the content of the closed container without opening the container. ### Claim 12 (depends on 11) The method of claim 11, wherein the antenna is part of a backscatter node. ### Claim 13 (depends on 11) The method of claim 11, wherein the antenna is part of a radio frequency identification tag. ### Claim 14 (depends on 11) The method of claim 11, wherein the second subset of measurements is affected, to a greater extent than is the first subset of measurements, by reflection of radio waves from surfaces other than the antenna. ### Claim 15 (depends on 11) The method of claim 11, wherein the second subset of measurements is affected by multipath propagation more than is the first set of measurements. ### Claim 16 (depends on 11) The method of claim 11, wherein the material is solid. ### Claim 17 (depends on 11) The method of claim 11, wherein the material is liquid. ### Claim 18 (depends on 11) The method of claim 11, wherein the method further comprises transmitting the radiation at each frequency in the set of frequencies, by performing frequency hopping. ### Claim 19 (depends on 11) The method of claim 11, wherein the method further comprises transmitting the radiation at each frequency in the set of frequencies, by performing orthogonal frequency-division multiplexing. ### Claim 20 (depends on 11) The method of claim 11, wherein: (A) the material is inside a closed container; and (B) the antenna and the radio frequency transceiver are outside of the closed container.