Radio wave arrival direction estimation apparatus

Patent metadata

Field	Value
Publication number	US-11467243-B2
Application number	US-202117165083-A
Country	US
Kind code	B2
Filing date	Feb 2, 2021
Priority date	Aug 3, 2018
Publication date	Oct 11, 2022
Grant date	Oct 11, 2022

Abstract

Two antennas receive three kinds of radio waves with different frequencies. A computation unit determines the arrival direction of the three kinds of radio waves arriving at the two antennas after propagating along two mutually different paths from a single transmit point in accordance with receive signals of the three kinds of radio waves with different frequencies received individually by the two antennas.

First claim

The invention claimed is:

1. A radio wave arrival direction estimation apparatus comprising:
a first antenna and a second antenna, each of the first and second antennas being configured to receive a first radio wave, a second radio wave, and a third radio wave, each of the first, second, and third radio waves having different frequencies; and
a processor configured to determine an arrival direction of the first, second, and third radio waves arriving at each of the first and second antennas,
wherein each of the first, second, and third radio waves propagate along a first path to each of the first antenna and the second antenna, and along a second path to each of the first antenna and the second antenna,
wherein the first path and the second path are mutually different paths from a single transmit point,
wherein the processor is configured to, for each of the first, second, and third radio waves received by each of the first and second antennas:
convert each of the first, second, and third radio waves into two complex signals;
compute a product of a complex conjugate of the corresponding two complex signals;
compute a quotient of the corresponding two complex signals; and
determine the arrival direction based on the corresponding product and the corresponding quotient.

2. The radio wave arrival direction estimation apparatus according to claim 1 , wherein the processor is configured to:
compute an approximation of a straight line by using a first set of three points on a complex plane and a center point of a circumference of a circle passing through a second set of three points on the complex plane; and
determine the arrival direction of each of the first, second, and third radio waves received by each of the first and second antennas based on an inclination of an approximation of the straight line and the center coordinate of the circumference of the circle,
wherein each point of the first set of three points corresponds to the product of a respective one of the first, second, and third radio waves, and
wherein each point of the second set of three points corresponds to the quotient of a respective one of the first, second, and third radio waves.

3. The radio wave arrival direction estimation apparatus according to claim 1 , wherein a distance between the first and second antennas is equal to or less than ¼ of a shortest wavelength of the first, second, and third radio waves.

4. The radio wave arrival direction estimation apparatus according to claim 2 , wherein a distance between the first and second antennas is equal to or less than ¼ of a shortest wavelength of the first, second, and third radio waves.

5. The radio wave arrival direction estimation apparatus according to claim 1 , wherein a fractional bandwidth of each of the first, second, and third radio waves is equal to or less than 5%.

6. The radio wave arrival direction estimation apparatus according to claim 2 , wherein a fractional bandwidth of each of the first, second, and third radio waves is equal to or less than 5%.

7. The radio wave arrival direction estimation apparatus according to claim 1 , wherein the first, second, and third radio waves are microwaves or millimeter waves.

8. The radio wave arrival direction estimation apparatus according to claim 2 , wherein the first, second, and third radio waves are microwaves or millimeter waves.

9. The radio wave arrival direction estimation apparatus according to claim 1 , wherein the first, second, and third radio waves conform to a wireless communication protocol.

10. The radio wave arrival direction estimation apparatus according to claim 2 , wherein the first, second, and third radio waves conform to a wireless communication protocol.

11. The radio wave arrival direction estimation apparatus according to claim 1 , wherein the first, second, and third radio waves are in a 2.4 GHz ISM band.

12. The radio wave arrival direction estimation apparatus according to claim 2 , wherein the first, second, and third radio waves are in a 2.4 GHz ISM band.

Assignees

• Murata Manufacturing Co

Inventors

• Takizawa Koichi

Classifications

• G01S3/043

  Receivers · CPC title

• G01S3/72

  Diversity systems specially adapted for direction-finding · CPC title

• G01S3/74 Primary

  Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals (systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14) · CPC title

• G01S3/46 Primary

  using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems · CPC title