# US 2017/0254901 A1 · Carrier Phase Double Differencing GNSS Receiving System with Spatial Integrity Monitoring

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- Number: US 2017/0254901 A1
- Document ID: US20170254901A1
- Status: Published application
- Kind: A1
- Application number: 15/062,625
- Filed: 2016-03-07
- Published: 2017-09-07
- Earliest claimed: 2016-03-07
- Assignees: Mitsubishi Electric Research Laboratories, Inc.
- Applicants: Mitsubishi Electric Research Laboratories, Inc.
- Inventors: Kyeong Jin Kim
- Web page: https://patentgrep.com/patent/US20170254901A1

## CPC

- G01S 19/22: Multipath-related issues
- G01S 19/39: the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S 19/215: {issues related to spoofing}
- G01S 19/396: {Determining accuracy or reliability of position or pseudorange measurements}
- G01S 19/43: using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
- 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

## Abstract

A method and system determines a reference receiver for carrier phase differencing in a global navigation satellite system by first receiving measurements from at least five satellites at a set of antennas of a set of receivers. Right-hand circular polarization is applied at a first subset of antennas of a first subset of receivers and left-hand circular polarization is applied at a second subset of the antennas of a second subset of receivers to produce first and second phase lock loop (PLL) outputs. Line-of-sight and non-line-of-sight detection are applied to the first and second PLL outputs to indicate a presence of multipath. Then, whether or not the first subset of receivers are affected by multipath and polarization changing impairments are output, and carrier phase double differencing is performed using carrier phase measurements to indicate which receiver is used as a reference receiver for the carrier phase double differencing.

## Claims

### Claim 1

A method for determining a reference receiver for carrier phase differencing in a global navigation satellite system (GNSS), comprising:
receiving measurements from at least five satellites at a set of antennas of a set of receivers, wherein the set of antennas are arranged at fixed locations on a moving object;
applying right-hand circular polarization (RHCP) at a first subset of antennas of a first subset of receivers and left-hand circular polarization (LHCP) at a second subset of the antennas of a second subset of receivers to produce first and second phase lock loop (PLL) outputs;
applying line-of-sight (LOS) and non-line-of-sight (nLOS) detection to the first and second PLL outputs to indicate a presence of multipath;
outputting whether or not the first subset of receivers are affected by multipath and polarization changing impairments; and
performing carrier phase double differencing using carrier phase measurements to indicate which receiver is used as a reference receiver for the carrier phase double differencing.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
performing a two-sample Kolmogorov-Smirnov (KS) test to detect normal or abnormal integer ambiguity resolution;
constructing a database for a normal condition;
determining an optimum threshold at a target false alarm probability based on statistics of the KS test to monitor a quality of the integer ambiguity resolution.

### Claim 3 (depends on 1)

The method of claim 1, wherein the moving object is a train.

### Claim 4 (depends on 1)

The method of claim 1, wherein the set of receivers are coupled by tight time synchronization.

### Claim 5

A system for determining a reference receiver for carrier phase differencing in a global navigation satellite system (GNSS), comprising:
a set of antennas of a set of receivers configured to receive measurements from at least five satellites, wherein the set of antennas are arranged at fixed locations on a moving object;
a processor configured to apply right-hand circular polarization (RHCP) at a first subset of antennas of a first subset of receivers and left-hand circular polarization (LHCP) at a second subset of the antennas of a second subset of receivers to produce first and second phase lock loop (PLL) outputs, and to apply line-of-sight (LOS) and non-line-of-sight (nLOS) detection to the first and second PLL outputs to indicate a presence of multipath, and to output whether or not the first subset of receivers are affected by multipath and polarization changing impairments, and to perform carrier phase double differencing using carrier phase measurements to indicate which receiver is used as a reference receiver for the carrier phase double differencing.