# US 2021/0333389 A1 · Synthetic-aperture-radar-signal processing device, method, and program

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- Number: US 2021/0333389 A1
- Document ID: US20210333389A1
- Status: Published application
- Kind: A1
- Application number: 16/625,154
- Filed: 2017-06-23
- Published: 2021-10-28
- Earliest claimed: 2017-06-23
- Assignees: NEC Corporation
- Applicants: NEC Corporation
- Inventors: Daisuke IKEFUJI; Osamu HOSHUYAMA
- Web page: https://patentgrep.com/patent/US20210333389A1

## CPC

- G01S 13/9019: {Auto-focussing of the SAR signals}
- G01S 13/90: using synthetic aperture techniques {, e.g. synthetic aperture radar [SAR] techniques}
- G01S 13/9023: {combined with interferometric techniques}
- 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 synthetic-aperture-radar-signal processing device includes a range bin selection unit which selects, from an observed image, range bins including a signal from an isolated reflection point, a phase evaluation unit which evaluates phases in an azimuth direction in the range bins, a window function multiplication unit which designs a window function on the basis of results of the evaluation by the phase evaluation unit and multiply the range bins by the window function, and a phase error correction unit which corrects the observed image by estimating a phase error from the range bins multiplied by the window function.

## Claims

### Claim 1

A synthetic-aperture-radar-signal processing device comprising:
a range bin selection unit which selects, from an observed image, range bins including a signal from an isolated reflection point;
a phase evaluation unit which evaluates phases in an azimuth direction in the range bins;
a window function multiplication unit which designs a window function on the basis of results of the evaluation by the phase evaluation unit and multiply the range bins by the window function; and
a phase error correction unit which corrects the observed image by estimating a phase error from the range bins multiplied by the window function.

### Claim 2 (depends on 1)

The synthetic-aperture-radar-signal processing device according to claim 1, wherein the phase evaluation unit includes
an evaluated range bin selection unit which selects a range bin from among the range bins as an evaluated range bin,
a phase calculation range determination unit which determines a calculation range of the phases in the evaluated range bin,
a phase calculation unit which obtains the phases in the calculation range of the evaluated range bin, and
a linearity judgment unit which judges whether the phases obtained by the phase calculation unit form a linear line.

### Claim 3 (depends on 2)

The synthetic-aperture-radar-signal processing device according to claim 2, wherein the linearity judgment unit includes
a regression line calculation unit which obtains a regression line of the phases obtained by the phase calculation unit,
a correlation coefficient calculation unit which obtains a correlation coefficient between the phases and the regression line, and
a threshold judgment unit which performs threshold judgment on the correlation coefficient to judge whether the phases form the linear line.

### Claim 4 (depends on 2)

The synthetic-aperture-radar-signal processing device according to claim 2, wherein the linearity judgment unit includes
a regression line calculation unit which obtains a regression line of the phases obtained by the phase calculation unit,
an error calculation unit which calculates an error between the phases obtained by the phase calculation unit and the regression line, and
a threshold judgment unit which performs threshold judgment on the error to judge whether the phases form the linear line.

### Claim 5 (depends on 2)

The synthetic-aperture-radar-signal processing device according to claim 2, wherein
the phase calculation unit calculates phases on a frequency axis in the evaluated range bin in the calculation range, and
the linearity judgment unit includes
a gradient calculation unit which calculates a gradient vector of the phases,
a standard deviation calculation unit which calculates a standard deviation of the gradient vector, and
a threshold judgment unit which performs threshold judgment on the standard deviation to judge whether the phases form the linear line.

### Claim 6 (depends on 1)

The synthetic-aperture-radar-signal processing device according to claim 1, wherein
the phase evaluation unit selects a plurality of range bins from the range bins selected by the range bin selection unit, and
the phase error correction unit corrects the observed image by calculating, for a respective one of the plurality of range bins, a range in which the phases in the azimuth direction form the linear line.

### Claim 7 (depends on 1)

The synthetic-aperture-radar-signal processing device according to claim 1, further comprising:
an amplitude evaluation unit which determines a range in which an amplitude value in the azimuth direction is higher than a threshold value, in the range bins selected by the range bin selection unit, wherein
the amplitude evaluation unit outputs the range bins within the range, to the phase evaluation unit.

### Claim 8

A synthetic-aperture-radar-signal processing method comprising:
selecting, from an observed image, range bins including a signal from an isolated reflection point;
evaluating phases in an azimuth direction in the range bins;
designing a window function on the basis of results of the evaluation and multiplying the range bins by the window function; and
correcting the observed image by estimating a phase error from the range bins multiplied by the window function.

### Claim 9 (depends on 8)

The synthetic-aperture-radar-signal processing method according to claim 8, wherein, when evaluating the phases,
selecting a range bin from among the range bins as an evaluated range bin,
determining a calculation range of the phases in the evaluated range bin,
obtaining the phases in the calculation range of the evaluated range bin, and
judging whether the obtained phases form a linear line.

### Claim 10 (depends on 9)

The synthetic-aperture-radar-signal processing method according to claim 9, wherein, when judging whether the phases form the linear line,
obtaining a regression line of the obtained phases,
obtaining a correlation coefficient between the phases and the regression line, and
performing threshold judgment on the correlation coefficient to judge whether the phases form the linear line.

### Claim 11 (depends on 9)

The synthetic-aperture-radar-signal processing method according to claim 9, wherein, when judging whether the phases form the linear line,
obtaining a regression line of the obtained phases,
obtaining a correlation coefficient between the phases and the regression line, and
performing threshold judgment on the correlation coefficient to judge whether the phases form the linear line.

### Claim 12 (depends on 9)

The synthetic-aperture-radar-signal processing method according to claim 9, wherein,
when obtaining the phases in the evaluated range bin, calculating phases on a frequency axis in the evaluated range bin in the calculation range, and
when judging whether the phases form the linear line,
calculating a gradient vector of the phases,
calculating a standard deviation of the gradient vector, and
performing threshold judgment on the standard deviation to judge whether the phases form the linear line.

### Claim 13 (depends on 8)

The synthetic-aperture-radar-signal processing method according to claim 8, wherein,
when evaluating the phases, selecting a plurality of range bins from the selected range bins, and
when correcting the observed image, calculating, for a respective one of the plurality of range bins, a range in which the phases in the azimuth direction form the linear line, to correct the observed image.

### Claim 14 (depends on 8)

The synthetic-aperture-radar-signal processing method according to claim 8, further comprising
determining a range in which an amplitude value in the azimuth direction is higher than a threshold value, in the selected range bins, wherein
when evaluating the phases, targeting the range bins within the determined range.

### Claim 15

A non-transitory computer readable recording medium storing a synthetic-aperture-radar-signal processing program, when executed by a processor, performs:
range bin selection processing of selecting, from an observed image, range bins including a signal from an isolated reflection point;
phase evaluation processing of evaluating phases in an azimuth direction in the range bins;
window function multiplication processing of designing a window function on the basis of results of the evaluation in the phase evaluation processing and multiplying the range bins by the window function; and
phase error correction processing of correcting the observed image by estimating a phase error from the range bins multiplied by the window function.

### Claim 16 (depends on 15)

The recording medium according to claim 15, the synthetic-aperture-radar-signal processing program further performs,
in the phase evaluation processing,
evaluated range bin selection processing of selecting a range bin from among the range bins as an evaluated range bin,
phase calculation range determination processing of determining a calculation range of the phases in the evaluated range bin,
phase calculation processing of obtaining the phases in the calculation range of the evaluated range bin, and
linearity judgment processing of judging whether the phases obtained in the phase calculation processing form a linear line.

### Claim 17 (depends on 16)

The recording medium according to claim 16, the synthetic-aperture-radar-signal processing program further performs,
in the linearity judgment processing,
regression line calculation processing of obtaining a regression line of the phases obtained in the phase calculation processing,
correlation coefficient calculation processing of obtaining a correlation coefficient between the phases and the regression line, and
threshold judgment processing of performing threshold judgment on the correlation coefficient to judge whether the phases form the linear line.

### Claim 18 (depends on 16)

The recording medium according to claim 16, the synthetic-aperture-radar-signal processing program further performs,
in the linearity judgment processing,
regression line calculation processing of obtaining a regression line of the phases obtained in the phase calculation processing,
error calculation processing of calculating an error between the phases obtained in the phase calculation processing and the regression line, and
threshold judgment processing of performing threshold judgment on the error to judge whether the phases form the linear line.

### Claim 19 (depends on 16)

The recording medium according to claim 16, the synthetic-aperture-radar-signal processing program further performs,
in the phase calculation processing, calculating phases on a frequency axis in the evaluated range bin in the calculation range, and
in the linearity judgment processing,
gradient calculation processing of calculating a gradient vector of the phases,
standard deviation calculation processing of calculating a standard deviation of the gradient vector, and
threshold judgment processing of performing threshold judgment on the standard deviation to judge whether the phases form the linear line.

### Claim 20 (depends on 15)

The recording medium according to claim 15, the synthetic-aperture-radar-signal processing program further performs,
in the phase evaluation processing, selecting a plurality of range bins from the range bins selected in the range bin selection processing, and
in the phase error correction processing, correcting the observed image by calculating, for a respective one of the plurality of range bins, a range in which the phases in the azimuth direction form a linear line.

### Claim 21

(canceled)