RADAR APPARATUS AND METHOD OF DETERMINING SIGN OF VELOCITY

• US 20150185244A1
• Filed: 12/23/2014
• Published: 07/02/2015
• Est. Priority Date: 12/26/2013
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: INOUE, Daisuke, YAMASHITA, Tatsuya, ICHIKAWA, Tadashi, KATO, Satoru, HASEGAWA, Kazuo
• Granted Patent: US 9,817,121 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01P 3/68 using optical means, i.e. using infrared, visible, or ultraviolet light G01P3/80 takes precedence ; by reflection of waves G01S17/58
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 7/4917 superposing optical signals in a photodetector, e.g. optical heterodyne detection

Abstract

A radar apparatus which can simply determine the sign of velocity of an object is provided. Laser light reflected by the object undergoes quadrature optical heterodyne detection performed by mixers, optical detectors, and a π/2 phase shifter, whereby I and Q component signals are output. A frequency analyzer performs FFT on a complex signal composed of the I component signal (real part) and the Q component signal (imaginary part) to thereby obtain its frequency spectrum. Since the frequency spectrum is calculated without being folded back even in a region where the frequency is negative, the sign of the Doppler frequency fd can be determined. When the Doppler frequency fd is positive, the sign of the velocity of the object is a direction toward the radar apparatus. When the Doppler frequency fd is negative, the sign of the velocity of the object is a direction away from the radar apparatus.

Claims

1. A radar apparatus which radiates laser light toward an object and detects and analyzes the laser light reflected by the object, comprising:

detector which includes first detector for mixing received laser light and pre-transmission laser light so as to perform optical heterodyne detection, and second detector for shifting the phase of one of the received laser light and the pre-transmission laser light by 90° and

mixing the phase-shifted one laser light with the other laser light so as to perform optical heterodyne detection; and

frequency analyzer for producing a complex signal while using electric signals output from the first detector and the second detector as an I component signal and a Q component signal, obtaining a Doppler frequency fd through frequency analysis of the complex signal, and determining the sign of velocity of the object from the sign of the Doppler frequency fd.

2. A radar apparatus according to claim 1, further comprising:

transmitter for radiating toward the object laser light whose intensity is modulated by a periodic signal having a frequency f0 lower than a lowest frequency at which the Doppler frequency fd produced as a result of movement of the object can be measured; and

phase difference detector for detecting a phase difference between the periodic signal and a component of the electric signal from the detector, the frequency of the component being f0, to thereby measure a distance to the object.

3. A radar apparatus according to claim 1, further comprising:

transmitter for radiating laser light toward the object, the laser light being frequency-modulated such that the frequency of the laser light changes continuously, wherein

the frequency analyzer further includes a device for producing a complex signal while using electric signals output from the first detector and the second detector as an I component signal and a Q component signal, and measuring a frequency shift corresponding to a distance to the object through frequency analysis of the complex signal, to thereby measure the distance to the object.

4. A radar apparatus according to claim 1, wherein the detector is constituted by an optical integrated circuit.

5. A radar apparatus according to claim 2, wherein the detector is constituted by an optical integrated circuit.

6. A radar apparatus according to claim 3, wherein the detector is constituted by an optical integrated circuit.

7. A method of determining the sign of velocity of an object by radiating laser light toward the object and detecting and analyzing the laser light reflected by the object, comprising:

mixing received laser light and pre-transmission laser light so as to perform optical heterodyne detection to thereby generate an I component signal;

shifting the phase of one of the received laser light and the pre-transmission laser light by 90° and

mixing the phase-shifted one laser light with the other laser light so as to perform optical heterodyne detection to thereby generate a Q component signal; and

obtaining a Doppler frequency fd through frequency analysis of a complex signal composed of the I component signal and the Q component signal, and determining the sign of velocity of the object from the sign of the Doppler frequency fd.