Radar apparatus

1. A radar apparatus comprising:

a transmitting portion including a plurality of transmitter elements that emits a transmitting signal as a radar wave toward an object;

a receiving portion including a plurality of receiver elements receiving a reflection signal that is a reflection of the transmitting signal by the object; and

an estimation portion,

wherein:

the estimation portion generates a virtual receiving array including virtual receiver elements whose number corresponds to a total number of receiver elements multiplied by a total number of transmitter elements;

the estimation portion divides the virtual receiving array into a plurality of identical sub-arrays;

the estimation portion generates covariance matrix data for each of the sub-arrays based on the reflection signal;

the estimation portion averages the covariance matrix data for each of the sub-arrays to decorrelate a direct reflection signal from the object and multipath reflection signal among the reflection signal and spatially smooths the reflection signal;

the estimation portion resolves the direct reflection signal from the object and the multipath reflection signal based on the result of spatial smoothing of the reflection signal; and

the estimation portion determines the direction of the object based on the direct reflection signal.

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

the transmitting portion includes at least two transmitter elements;

the receiving portion includes at least three receiver elements that are arranged in at least two rows in a first direction and at least three columns in a second direction perpendicular to the first direction; and

a first respective distance in the first direction between neighboring ones of all of the at least two transmitter elements corresponds to a second respective distance in the first direction between neighboring ones of all receiver elements in neighboring rows multiplied by a total number of rows of receiver elements.

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

in a case of an odd number of receiver elements, the transmitter elements are provided in an identical column.

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

in a case of an even number of receiver elements, a third respective distance in the second direction between neighboring ones of all of the at least two transmitter elements in neighboring rows corresponds to a fourth respective distance in the second direction between neighboring receiver elements in different rows multiplied by the number of rows of receiver elements.

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

in the virtual receiving array, a total number of virtual receiver elements is doubled in the first direction in comparison to the number of receiver elements in a receiving antenna in the first direction.

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

the transmitting antenna includes at least two transmitter elements;

a receiving antenna includes at least two groups of receiver elements wherein each group has at least two receiver elements that are arranged in at least two rows in a first direction and at least two columns in a second direction perpendicular to the first direction;

a first respective distance in the second direction between neighboring ones of all of the at least two transmitter elements in an identical same row corresponds to a twofold of a second respective distance in the second direction between neighboring ones of all receiver elements in one group; and

a third respective distance in the second direction in an identical row between structurally corresponding receiver elements of neighboring groups of receiver elements corresponds to the first respective distance in the second direction between neighboring ones of all of the at least two transmitter elements in the identical row multiplied by the number of transmitter elements in one row.

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

in the virtual receiving array, a total number of virtual receiver elements is doubled in the second direction in comparison to the number of receiver elements in the receiving antenna in the second direction.

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

the transmitter elements and the receiver elements are disposed in an identical plane and the first direction is a vertical direction and a second direction is a horizontal direction.

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

the estimation portion applies an eigenstructure technique to each of the covariance matrix data of the virtual receiving array.

10. The radar apparatus according to according to claim 9 , wherein:

the eigenstructure technique is a multiple signal classification algorithm.