# US 9,048,979 B2 · RF carrier synchronization and phase alignment methods and systems

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- Number: US 9,048,979 B2
- Document ID: US9048979B2
- Status: Granted
- Kind: B2
- Application number: 14/043,789
- Filed: 2013-10-01
- Published: 2014-04-03
- Granted: 2015-06-02
- Earliest claimed: 2012-10-01
- Assignees: PhasorLab, Inc.
- Applicants: Joshua C. Park
- Inventors: Joshua C. Park
- Web page: https://patentgrep.com/patent/US9048979B2

## CPC

- H04W 56/006: {using known positions of transmitter and receiver}
- G01S 3/18: derived directly from separate directional antennas
- H04B 7/0413: MIMO systems
- H04L 7/0016: {correction of synchronization errors}
- H04L 25/02: Details {; arrangements for supplying electrical power along data transmission lines (systems for transmitting signals via power distribution lines H04B3/54)}
- H04L 27/0014: {Carrier regulation (of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657)}
- H04L 27/364: {Arrangements for overcoming imperfections in the modulator, e.g. quadrature error or unbalanced I and Q levels}
- H04W 56/0035: {detecting errors in frequency or phase}
- H04W 64/006: {with additional information processing, e.g. for direction or speed determination}
- H04L 2027/003: {at baseband only}
- H04L 2027/0046: {Open loops}
- H04L 2027/0053: {Closed loops}
- H04L 2027/0067: {Phase error detectors}
- 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
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A method comprising generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency; obtaining baseband signal samples of the baseband information signal having a baseband signal magnitude and a baseband signal phase; determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold; and, applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase.

## Claims

### Claim 1

A method comprising:
generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency;
obtaining baseband signal samples of the baseband information signal having an in-phase signal sample and a quadrature signal sample;
determining an offset frequency rotation based on an estimated correlation between the in-phase signal samples and the quadrature signal samples;
processing the baseband information signal using the offset frequency rotation;
determining an offset phase associated with the estimated correlation between the in-phase signal samples and the quadrature signal samples;
processing the baseband information signal using the offset phase; and
determining the offset phase based on a symmetry property of the estimated correlation, the symmetry property being measured with respect to a plurality of frequency offsets.

### Claim 2

A method comprising
generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency;
obtaining baseband signal samples of the baseband information signal having an in-phase signal sample and a quadrature signal sample;
determining an offset frequency rotation based on an estimated correlation between the in-phase signal samples and the quadrature signal samples;
processing the baseband information signal using the offset frequency rotation;
determining an offset phase associated with the estimated correlation between the in-phase signal samples and the quadrature signal samples;
processing the baseband information signal using the offset phase; and
determining the offset frequency rotation and offset phase with respect to a maximum value of the estimated correlation, wherein the estimated correlation is calculated using a plurality of candidate phase offsets over a first range and candidate frequency rotations over a second range.

### Claim 3 (depends on 2)

The method of claim 2 further comprising updating the offset frequency rotation and the offset phase by recalculating a maximum value of the estimated correlation, wherein at least one of the first range and the second range is reduced.