# US 2018/0324012 A1 · Synchronization method of an active load modulation clock within a transponder > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0324012 A1 - Document ID: US20180324012A1 - Status: Published application - Kind: A1 - Application number: 15/966,948 - Filed: 2018-04-30 - Published: 2018-11-08 - Earliest claimed: 2017-05-02 - Assignees: Stmicroelectronics Razvoj Polprevodnikov D.O.O. - Applicants: STMicroelectronics razvoj polprevodnikov d.o.o. - Inventors: Maksimiljan Stiglic; Kosta Kovacic - Web page: https://patentgrep.com/patent/US20180324012A1 ## CPC - H04L 27/2071: {in which the data are represented by the carrier phase, e.g. systems with differential coding} - 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} - H04B 5/77: for interrogation - H04L 27/04: Modulator circuits; Transmitter circuits - H04L 27/361: {Modulation using a single or unspecified number of carriers, e.g. with separate stages of phase and amplitude modulation} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS - H04B: TRANSMISSION ## Abstract A method of wireless communication includes transmitting frames from a transponder to a reader and synchronizing between a reader carrier frequency and an active load modulation (ALM) carrier frequency within each transmitted frame. Each transmitted frame includes ALM carrier bursts generated from subcarrier modulation by binary phase shift keying (BPSK) data encoding and producing signal oscillations at a transponder antenna after each ALM carrier burst generation, The synchronizing occurs at each phase change of the data encoding when no burst is generated during a half period of the subcarrier preceding the phase change and a half period of the subcarrier following this phase change. The transponder antenna has a moderate quality factor sufficient to naturally damp the signal oscillations so that the synchronizing is performed without performing any controlled signal oscillations damping. ## Claims ### Claim 1 A method of wireless communication, the method comprising: transmitting frames from a transponder to a reader; and synchronizing between a reader carrier frequency and an active load modulation (ALM) carrier frequency within each transmitted frame; wherein each transmitted frame includes ALM carrier bursts generated from subcarrier modulation by binary phase shift keying (BPSK) data encoding and producing signal oscillations at a transponder antenna after each ALM carrier burst generation; wherein the synchronizing occurs at each phase change of the data encoding when no burst is generated during a half period of the subcarrier preceding the phase change and a half period of the subcarrier following this phase change; and wherein the transponder antenna has a moderate quality factor sufficient to naturally damp the signal oscillations so that the synchronizing is performed without performing any controlled signal oscillations damping. ### Claim 2 (depends on 1) The method according to claim 1, wherein the transponder antenna has a quality factor smaller than or equal to 8. ### Claim 3 (depends on 2) The method according to claim 2, wherein the transponder antenna has a quality factor greater than or equal to 4. ### Claim 4 (depends on 1) The method according to claim 1, wherein the transponder antenna has a quality factor greater than or equal to 4. ### Claim 5 (depends on 1) The method according to claim 1, wherein the ALM carrier is provided by a digital phase locked loop that includes a digitally controlled oscillator, the digital phase locked loop receiving the reader carrier and being in a hold mode in which a feedback loop of the digital phase locked loop is opened between each synchronization and in a lock mode in which the feedback loop is closed for performing each synchronization. ### Claim 6 (depends on 5) The method according to claim 5, wherein the transponder antenna has a quality factor between 4 and 8 and wherein the wireless communication is compliant with an ISO/IEC 14443 type B protocol ### Claim 7 (depends on 1) The method according to claim 1, wherein the wireless communication is compliant with an ISO/IEC 14443 type B protocol. ### Claim 8 A method of wireless communication, the method comprising: generating a plurality of frames from subcarrier modulation by binary phase shift keying (BPSK) data encoding, the plurality of frames that each including active load modulation (ALM) carrier bursts; producing signal oscillations at a transponder antenna after each ALM carrier burst generation; providing an ALM carrier using a digital phase locked loop that includes a digitally controlled oscillator; and synchronizing between a reader carrier frequency and an ALM carrier frequency at each phase change of the data encoding when no burst is generated during a half period of the subcarrier preceding the phase change and a half period of the subcarrier following this phase change, the digital phase locked loop receiving a reader carrier and being in a hold mode in which a feedback loop of the digital phase locked loop is opened between each synchronization and in a lock mode in which the feedback loop is closed for performing each synchronization, wherein the transponder antenna has a moderate quality factor sufficient to naturally damp the signal oscillations so that the synchronizing is performed without performing any controlled signal oscillations damping. ### Claim 9 (depends on 8) The method according to claim 8, wherein the transponder antenna has a quality factor smaller than or equal to 8. ### Claim 10 (depends on 9) The method according to claim 9, wherein the transponder antenna has a quality factor greater than or equal to 4. ### Claim 11 (depends on 8) The method according to claim 8, wherein the wireless communication is compliant with an ISO/IEC 14443 type B protocol. ### Claim 12 A transponder, comprising: an antenna; a transmitter configured to transmit frames including active load modulation (ALM) carrier bursts to a reader through the antenna, the transmitter including an encoder configured to perform binary phase shift keying data encoding, the transmitter also including a modulator configured to perform a subcarrier modulation with the data encoding and to generate the ALM carrier bursts leading to signal oscillations at the antenna after each burst generation; and a synchronization circuit configured to perform, within each transmitted frame, synchronization between a reader carrier frequency and a carrier frequency of the ALM carrier bursts at each phase change of the data encoding when no burst is generated during a half period of the subcarrier preceding the phase change and a half period of the subcarrier following this phase change; wherein the antenna has a moderate quality factor sufficient to naturally damp the signal oscillations and permit the synchronization without performing any controlled signal oscillations damping. ### Claim 13 (depends on 12) The transponder according to claim 12, wherein the antenna has a quality factor smaller than or equal to 8. ### Claim 14 (depends on 13) The transponder according to claim 13, wherein the antenna has a quality factor greater than or equal to 4. ### Claim 15 (depends on 12) The transponder according to claim 12, wherein the antenna has a quality factor greater than or equal to 4. ### Claim 16 (depends on 12) The transponder according to claim 12, wherein the synchronization circuit comprises a digital phase locked loop. ### Claim 17 (depends on 16) The transponder according to claim 16, wherein the digital phase locked comprises a digitally controlled oscillator and a controller configured to put the digital phase locked loop in hold mode in which a feedback loop of the digital phase locked loop is opened between each synchronization and to close the feedback loop for performing each synchronization. ### Claim 18 (depends on 12) The transponder according to claim 12, wherein the transponder is configured to wirelessly communicate towards the reader according an ISO/IEC 14443 type B protocol.