# US 2021/0243716 A1 · Distance estimation using signals of different frequencies > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0243716 A1 - Document ID: US20210243716A1 - Status: Published application - Kind: A1 - Application number: 16/781,762 - Filed: 2020-02-04 - Published: 2021-08-05 - Earliest claimed: 2020-02-04 - Assignees: Alibaba Group Holding Limited - Applicants: Alibaba Group Holding Limited - Inventors: SSU-PIN MA; Hueiming Steve Yang - Web page: https://patentgrep.com/patent/US20210243716A1 ## CPC - H04W 64/003: {locating network equipment} - G01S 1/0428: {Signal details} - G01S 1/68: Marker, boundary, call-sign, or like beacons transmitting signals not carrying directional information - G01S 11/02: using radio waves (G01S19/00 takes precedence) - H03L 7/07: using several loops, e.g. for redundant clock signal generation - H04J 3/0617: {the synchronising signal being characterised by the frequency or phase} - H04J 3/0664: {unidirectional timestamps} - H04J 3/0697: {Synchronisation in a packet node} - H04L 7/033: using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop - H04W 4/029: Location-based management or tracking services - H04W 56/0035: {detecting errors in frequency or phase} - G01S 5/0236: {Assistance data, e.g. base station almanac} - G01S 5/14: Determining absolute distances from a plurality of spaced points of known location - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H03L: AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES (generation of oscillations H03B) - 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) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A first signal generated from a signal generator may be synchronized with a local clock of a first device at a first time, and sent to a second device, the first signal having a first frequency. A second signal generated from the signal generator may be further synchronized with the local clock of the first device at a second time, the second signal having a second frequency different from the first frequency, and a difference between the second time and the first time being within a predetermined range of a predetermined time difference. The second signal may then be sent to the second device to enable the second device to determine a distance between the first device and the second device based at least in part on a phase difference between the first signal and the second signal. ## Claims ### Claim 1 A method implemented by a first device, the method comprising: synchronizing a first signal generated from a signal generator with a local clock of the first device at a first time, the first signal having a first frequency; sending the first signal to a second device; synchronizing a second signal generated from the signal generator with the local clock of the first device at a second time, the second signal having a second frequency different from the first frequency, and a difference between the second time and the first time being within a predetermined range of a predetermined time difference; and sending the second signal to the second device to enable the second device to obtain a first estimated value for a distance between the first device and the second device based at least in part on a phase difference between the first signal and the second signal. ### Claim 2 (depends on 1) The method of claim 1, further comprising sending information of the first frequency, the second frequency and the predetermined time difference to the second device. ### Claim 3 (depends on 1) The method of claim 1, wherein the signal generator comprises a fractional-N phase lock loop with a resetting circuit. ### Claim 4 (depends on 3) The method of claim 3, wherein synchronizing the first signal generated from the signal generator with the local clock of the first device at the first time comprises performing a reset on the fractional-N phase lock loop through the resetting circuit at the first time. ### Claim 5 (depends on 1) The method of claim 1, wherein synchronizing the first signal generated from the signal generator with the local clock of the first device comprises establishing a phase relationship between a phase of the first signal and the local clock. ### Claim 6 (depends on 1) The method of claim 1, further comprising: synchronizing a third signal generated from the signal generator with the local clock of the first device at a third time, the third signal having a third frequency different from the first frequency and the second frequency, and a difference between the second time and the third time being within the predetermined range of the predetermined time difference; and sending the third signal to the second device to enable the second device to obtain a second estimated value for the distance between the first device and the second device based at least in part on a phase difference between the second signal and the third signal. ### Claim 7 (depends on 6) The method of claim 6, further comprising obtaining a final estimated value for the distance between the first device and the second device based on the first estimated value and the second estimated value. ### Claim 8 One or more processor readable media storing executable instructions that, when executed by one or more processors of a first device, cause the one or more processors to perform acts comprising: changing a signal frequency of a signal generator to a first frequency; synchronizing signals generated from the signal generator with a local clock of the first device at a first time; receiving a first signal from a second device; changing the signal frequency of the signal generator to a second frequency; synchronizing the signals generated from the signal generator with the local clock of the first device at a second time, a difference between the second time and the first time being within a predetermined range of a predetermined time difference; receiving a second signal from the second device; and obtaining a first estimated value for a distance between the first device and the second device based at least in part on a phase difference between the first signal and the second signal. ### Claim 9 (depends on 8) The one or more processor readable media of claim 8, the acts further comprising receiving information of the first frequency, the second frequency and the predetermined time difference from the second device. ### Claim 10 (depends on 8) The one or more processor readable media of claim 8, wherein the signal generator comprises a fractional-N phase lock loop with a resetting circuit. ### Claim 11 (depends on 10) The one or more processor readable media of claim 10, wherein synchronizing the signals generated from the signal generator with the local clock of the first device at the first time comprises performing a reset on the fractional-N phase lock loop through the resetting circuit at the first time. ### Claim 12 (depends on 8) The one or more processor readable media of claim 8, the acts further comprising calculating the predetermined range based at least in part on a frequency of the local clock and a fractional value. ### Claim 13 (depends on 8) The one or more processor readable media of claim 8, wherein synchronizing the signals generated from the signal generator with the local clock of the first device comprises establishing a phase relationship between a phase of the signals and the local clock. ### Claim 14 (depends on 8) The one or more processor readable media of claim 8, the acts further comprising: calculating a clock frequency offset between the local clock of the first device and a local clock of the second device; and correcting the calculated distance based at least in part on the calculated clock frequency offset. ### Claim 15 (depends on 8) The one or more processor readable media of claim 8, the acts further comprising: changing the signal frequency of the signal generator to a third frequency, the third frequency being different from the first frequency and the second frequency; synchronizing the signals generated from the signal generator with the local clock of the first device at a third time, a difference between the second time and the third time being within the predetermined range of the predetermined time difference; receiving a third signal from the second device; and obtaining a second estimated value for the distance between the first device and the second device based at least in part on a phase difference between the second signal and the third signal. ### Claim 16 A system implemented by a first processor chipset, the system comprising: one or more processors; and memory storing executable instructions that, when executed by the one or more processors, cause the one or more processors to perform acts comprising: changing a signal frequency of a signal generator to a first frequency; synchronizing signals generated from the signal generator with a local clock of the processor chipset at a first time; receiving a first signal from a second processor chipset; changing the signal frequency of the signal generator to a second frequency; synchronizing the signals generated from the signal generator with the local clock of the first processor chipset at a second time, a difference between the second time and the first time being within a predetermined range of a predetermined time difference; receiving a second signal from the second processor chipset; and calculating a distance between the first processor chipset and the second processor chipset based at least in part on a phase difference between the first signal and the second signal. ### Claim 17 (depends on 16) The system of claim 16, the acts further comprising receiving information of the first frequency, the second frequency and the predetermined time difference from the second processor chipset. ### Claim 18 (depends on 16) The system of claim 16, wherein the signal generator comprises a fractional-N phase lock loop with a resetting circuit. ### Claim 19 (depends on 18) The system of claim 18, wherein synchronizing the signals generated from the signal generator with the local clock of the first processor chipset at the first time comprises performing a reset on the fractional-N phase lock loop through the resetting circuit at the first time. ### Claim 20 (depends on 16) The system of claim 16, the acts further comprising: calculating a clock frequency offset between the local clock of the first processor chipset and a local clock of the second processor chipset; and correcting the calculated distance based at least in part on the calculated clock frequency offset.