Radar apparatus

1. A radar apparatus installed on a vehicle with a predetermined detection limit angle (±θc) to a front area of the vehicle, the radar apparatus transmitting radar waves externally from the vehicle, receiving reflected waves of the transmitted radar waves, and detecting information about a target which has reflected the radar waves, the radar apparatus characterized by:

a relative velocity calculating unit that calculates a relative velocity (Vr) between the target and a radar-apparatus-installed vehicle based on information about the target which has reflected the radar waves;

a radar-apparatus-installed vehicle velocity acquiring unit that acquires a velocity (Vn) of the radar-apparatus-installed vehicle; and

a determining unit that compares a ratio (−Vr/Vn) of the relative velocity (Vr) to the velocity (Vn) of the radar-apparatus-installed vehicle with a determination value (α) that is a cosine (cos θc) of the detection limit angle (±θc) or the cosine (cos θc) plus a correction value including a measurement error, in which when a determination is made that the ratio (−Vr/Vn) exceeds the determination value (α), a determination is made that the target is a real target of a stationary object or a crossing object crossing a traveling route in the front area of the radar-apparatus-installed vehicle, and when a determination is made that the ratio (−Vr/Vn) is the determination value (α) or less, a determination is made that the target is a ghost of the stationary object or the crossing object.

2. The radar apparatus according to claim 1 , wherein:

determination by the determining unit is performed for a plurality of times; and

when a determination is made that the target is the real target for a predetermined number of times, a confirmation is made that the target is the real target.

3. The radar apparatus according to claim 1 , wherein:

determination by the determining unit is performed for a plurality of times; and

when a determination is made that the target is a ghost of the real target for a predetermined number of times, a confirmation is made that the target is a ghost of the real target.

4. A radar apparatus installed on a vehicle, the radar apparatus transmitting radar waves externally from the vehicle, receiving reflected waves of the transmitted radar waves, and detecting information about a target which has reflected the radar waves, the radar apparatus characterized by:

a radar-apparatus-installed vehicle velocity acquiring unit that calculates a velocity (Vn) of the radar-apparatus-installed vehicle;

an azimuth angle calculating unit that calculates an azimuth angle (θest) of a main target to be a basis based on information about the target which has reflected the radar waves;

a grating angle calculating unit that calculates a left grating angle (θgrt 1 ) and a right grating angle (θgrt 2 ) to the main target;

an estimated longitudinal velocity calculating unit that calculates a main estimated longitudinal velocity (Vy_est) of the main target, a first estimated longitudinal velocity (Vy_grt 1 ) of a first target having the left grating angle (θgrt 1 ), and a second estimated longitudinal velocity (Vy_grt 2 ) of a second target having the right grating angle (θgrt 2 );

a first determining unit that compares the main estimated longitudinal velocity (Vy_est) of the main target with the velocity (Vn) of the radar-apparatus-installed vehicle, in which when the main estimated longitudinal velocity (Vy_est) of the main target and the velocity (Vn) of the radar-apparatus-installed vehicle are substantially equal, a determination is made that the main target is a real target; and

a second determining unit that compares the first estimated longitudinal velocity (Vy_grt 1 ) of the first target with the velocity (Vn) of the radar-apparatus installed vehicle, in which when the first estimated longitudinal velocity (Vy_grt 1 ) of the first target and the velocity (Vn) of the radar-apparatus-installed vehicle are substantially equal, a determination is made that the target determined whose longitudinal velocity is equal to the radar-apparatus-installed vehicle velocity is a ghost of a stationary object, or that compares the second estimated longitudinal velocity (Vy_grt 2 ) of the second target with the velocity (Vn) of the radar-apparatus-installed vehicle, in which when the second estimated longitudinal velocity (Vy_grt 2 ) of the second target and the velocity (Vn) of the radar-apparatus-installed vehicle are substantially equal, a determination is made that the target determined whose longitudinal velocity is equal to the radar-apparatus-installed vehicle velocity is a ghost of a stationary object.

5. The radar apparatus according to claim 4 , wherein

the left grating angle (θgrt 1 ) and the right grating angle (θgrt 2 ) are calculated by Expressions (1) and (2)

θgrt1=asin(sin(θest)−λ/ d )  (1)

θgrt2=asin(sin(θest)+λ/ d )  (2)

where, λ is a wavelength [m] and d is an antenna element gap [m].

6. The radar apparatus according to claim 4 , wherein:

a relative velocity (Vr) between the target and the radar-apparatus-installed vehicle is found based on information about the target which has reflected the radar waves; and

the main estimated longitudinal velocity (Vy_est), the first estimated longitudinal velocity (Vy_grt 1 ), and the second estimated longitudinal velocity (Vy_grt 2 ) are calculated by Expressions (3), (4), and (5) below

Vy _est=− Vr /cos θest  (3)

Vy _grt1=− Vr /cos θgrt1  (4)

Vy _grt2=− Vr /cos θgrt2  (5).

7. The radar apparatus according to claim 4 , wherein:

determination by the first determining unit is performed for a plurality of times; and

when a determination is made that the target is the real target for a predetermined number of times, a confirmation is made that the target is the real target.

8. The radar apparatus according to claim 4 , wherein:

determination by the second determining unit is performed for a plurality of times; and

when a determination is made that the target is a ghost of the real target for a predetermined number of times, a confirmation is made that the target is a ghost of the real target.