# US 11,451,311 B2 · Method for antenna calibration and active antenna system for use in antenna calibration > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,311 B2 - Document ID: US11451311B2 - Status: Granted - Kind: B2 - Application number: 17/291,104 - Filed: 2018-11-05 - Published: 2022-01-06 - Granted: 2022-09-20 - Earliest claimed: 2018-11-05 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget LM Ericsson (publ) - Inventors: Ang Feng; Jinlai He; Yaxin Xing; Guangsheng Guo - Web page: https://patentgrep.com/patent/US11451311B2 ## CPC - H04B 17/12: of transmit antennas, e.g. of the amplitude or phase - H01Q 3/267: {Phased-array testing or checking devices} - H04B 1/7075: with code phase acquisition - H04B 7/0408: using two or more beams, i.e. beam diversity - H04B 7/06: at the transmitting station - H04B 17/14: of the whole transmission and reception path, e.g. self-test loop-back - H04J 13/0022: {PN, e.g. Kronecker} - H04B: TRANSMISSION - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) ## Abstract A method for antenna calibration for an active antenna system is disclosed. According to an embodiment, test signals are generated for multiple antennas of the active antenna system. The test signals are transmitted via the multiple antennas. A first signal that results from the transmission of the test signals is received over the air. A second signal is received from a coupler network of the active antenna system. The coupler network is configured to generate coupled signals of the test signals and combine the coupled signals into the second signal. Calibration information for compensating an influence of the coupler network is determined based on the first and second signals. An active antenna system is also disclosed for use in antenna calibration. ## Claims ### Claim 1 A method for antenna calibration for an active antenna system, the method comprising: generating test signals for a plurality of antennas of the active antenna system; transmitting the test signals via the plurality of antennas; receiving, over the air, a first signal that results from the transmission of the test signals; receiving a second signal from a coupler network of the active antenna system that is configured to generate coupled signals of the test signals and combine the coupled signals into the second signal; and determining calibration information for compensating an influence of the coupler network, based on the first and second signals. ### Claim 2 (depends on 1) The method of claim 1, wherein generating the test signals comprises: generating a root sequence; generating spreading codes for the plurality of antennas; and calculating, for each of the plurality of antennas, a product between the root sequence and one of the spreading codes. ### Claim 3 (depends on 2) The method of claim 2, wherein the generating of the root sequence, the generating of the spreading codes and the calculating of the products are performed by the active antenna system. ### Claim 4 (depends on 2) The method claim 2, wherein generating the root sequence comprises: generating an initial root sequence in frequency domain; and transforming the initial root sequence into the root sequence by inverse fast Fourier transformation, IFFT. ### Claim 5 (depends on 4) The method of claim 4, wherein the initial root sequence is a pseudo noise sequence. ### Claim 6 (depends on 5) The method of claim 5, wherein the pseudo noise sequence is one of: a Zadoff-Chu sequence; an M-sequence; and a Gold sequence. ### Claim 7 (depends on 2) The method of claim 2, wherein the spreading codes are generated by using one of: Hadamard matrix and Walsh matrix. ### Claim 8 (depends on 1) The method of claim 1, wherein the test signals are generated for the plurality of antennas simultaneously; and wherein the test signals are transmitted via the plurality of antennas simultaneously. ### Claim 9 (depends on 1) The method claim 1, wherein the plurality of antennas are divided into subgroups; and wherein the generating of the test signals, the transmitting of the test signals, the receiving of the first signal and the receiving of the second signal are performed for each of the subgroups respectively. ### Claim 10 (depends on 9) The method of claim 9, wherein the subgroups include common subgroups and one additional subgroup; wherein a union set of the common subgroups is a set of the plurality of antennas and wherein an intersection between any two of the common subgroups is an empty set; and wherein the one additional subgroup includes, for each subgroup in the common subgroups, a member from the subgroup. ### Claim 11 (depends on 1) The method of claim 1, wherein determining the calibration information comprises: obtaining first inphase and quadrature, IQ, data from the first signal; obtaining second IQ data from the second signal; and determining, as the calibration information, a phase difference between the first and second IQ data. ### Claim 12 An active antenna system comprising: a plurality of antennas; a digital signal generator configured to generate digital signals for the plurality of antennas; a plurality of transmitters configured to process the digital signals into test signals for transmission via the plurality of antennas; a coupler network connected between the plurality of transmitters and the plurality of antennas and configured to generate coupled signals of the test signals and combine the coupled signals into a feedback signal; and a feedback receiver configured to receive the feedback signal. ### Claim 13 (depends on 12) The active antenna system of claim 12, wherein the digital signals are training sequences. ### Claim 14 (depends on 12) The active antenna system of claim 12, wherein the digital signal generator is configured to generate the digital signals based on multi-carrier code division multiple access. ### Claim 15 (depends on 14) The active antenna system of claim 14, wherein the digital signal generator comprises: a root sequence generator configured to generate a root sequence; a spreading code generator configured to generate spreading codes for the plurality of antennas; and a multiplication unit configured to calculate, for each of the plurality of antennas, a product between the root sequence and one of the spreading codes. ### Claim 16 (depends on 15) The active antenna system of claim 15, wherein the root sequence is stored in a common memory shared between the plurality of antennas. ### Claim 17 (depends on 15) The active antenna system of claim 15, wherein the root sequence generator is configured to generate the root sequence by: generating an initial root sequence in frequency domain; and transforming the initial root sequence into the root sequence by inverse fast Fourier transformation, IFFT. ### Claim 18 (depends on 12) The active antenna system of claim 12, wherein the digital signal generator is configured to generate the digital signals for the plurality of antennas simultaneously. ### Claim 19 (depends on 12) The active antenna system of claim 12, wherein the plurality of antennas are divided into subgroups; and wherein the digital signal generator is configured to generate the digital signals for each of the subgroups respectively. ### Claim 20 (depends on 19) The active antenna system of claim 19, wherein the subgroups include common subgroups and one additional subgroup; wherein a union set of the common subgroups is a set of the plurality of antennas and wherein an intersection between any two of the common subgroups is an empty set; and wherein the one additional subgroup includes, for each subgroup in the common subgroups, a member from the subgroup.