Radar apparatus for vehicle and method of removing ghost of the same

1. A radar apparatus for vehicle, which senses a target positioned in front of a vehicle by including a plurality of transmitting antennas and a plurality of receiving antennas disposed on a substrate, the radar apparatus for vehicle comprising:

a transmitting unit configured to transmit a predetermined transmission signal to the front of the vehicle through the plurality of transmitting antennas;

a receiving unit configured to receive a reception signal generated from the transmission signal transmitted by the transmitting unit and reflected and returned by the target positioned in front of the vehicle through the plurality of receiving antennas and an added receiving antenna; and

a signal processing unit configured to remove a grating lobe ghost by using at least one of a digital beamforming result in which the reception signals received through the plurality of receiving antennas are added, and a digital beamforming result in which the reception signals received through the plurality of receiving antennas and the reception signal received through the added receiving antenna are added,

wherein the added receiving antenna has an interval different from an interval between the plurality of receiving antennas.

2. The radar apparatus for vehicle of claim 1 , wherein the signal processing unit comprises:

a calculating unit configured to calculate a gain difference of each lobe of which a gain value is equal to, or higher than, a predetermined gain value of an angular power spectrum obtained through the digital beamforming result in which the reception signals received through the plurality of receiving antennas are added and an angular power spectrum obtained through the digital beamforming result in which the reception signals received through the plurality of receiving antennas and the reception signal received through the added receiving antenna are added; and

a ghost removing unit configured to remove a corresponding grating lobe ghost by determining the lobe as the grating lobe ghost, when the calculated gain difference of each lobe is higher than a predetermined reference difference.

3. The radar apparatus for vehicle of claim 2 , wherein the calculating part calculates the gain difference of each lobe by mutually comparing gains of the lobes generated in the same angle of the angular power spectrum, and determines a lobe of which the gain difference of each lobe is zero as a main lobe.

4. The radar apparatus for vehicle of claim 1 , wherein the plurality of receiving antennas are long distance receiving antennas, and the added receiving antenna is one receiving antenna most adjacent to the long distance receiving antennas, among a plurality of short distance receiving antennas.

5. The radar apparatus for vehicle of claim 1 , wherein the signal processing unit removes the grating lobe ghost by using a comparison result obtained by comparing a lobe width of an angular power spectrum obtained through the digital beamforming result in which the reception signals received through the plurality of receiving antennas and the reception signal received through the added receiving antenna are added with a predetermined reference width.

6. The radar apparatus for vehicle of claim 5 , wherein the signal processing unit comprises:

a calculating unit configured to calculate a lobe width for at least one lobe of the angular power spectrum in a predetermined gain value; and

a determining unit configured to determine the lobe as the grating lobe ghost when the lobe width is equal to, or higher than, the reference width.

7. The radar apparatus for vehicle of claim 6 , wherein the signal processing unit further comprises a ghost removing unit configured to determine the lobe as a main lobe when the lobe width is lower than the reference width and to remove the lobe determined as the grating lobe ghost.

8. A method of removing a ghost of a radar apparatus for vehicle, which senses a target positioned in front of a vehicle by including a plurality of transmitting antennas and a plurality of receiving antennas disposed on a substrate, the method comprising:

transmitting a predetermined transmission signal to the front of the vehicle through the plurality of transmitting antennas;

receiving a reception signal generated from the transmission signal transmitted, reflected and returned by the target positioned in front of the vehicle through the plurality of receiving antennas and an added receiving antenna; and

removing a grating lobe ghost by using at least one of a digital beamforming result in which the reception signals received through the plurality of receiving antennas are added, and a digital beamforming result in which the reception signals received through the plurality of receiving antennas and the reception signal received through the added receiving antenna are added,

wherein the added receiving antenna has an interval different from an interval between the plurality of receiving antennas.

9. The method of claim 8 , wherein the removing comprises:

calculating a gain difference of each lobe of which a gain value is equal to, or higher than, a predetermined gain value of an angular power spectrum obtained through the digital beamforming result in which the reception signals received through the plurality of receiving antennas are added and an angular power spectrum obtained through the digital beamforming result in which the reception signals received through the plurality of receiving antennas and the reception signal received through the added receiving antenna are added; and

removing a corresponding grating lobe ghost by determining the lobe as the grating lobe ghost when the calculated gain difference of each lobe is higher than a predetermined reference difference.

10. The method of claim 9 , wherein the calculating comprises calculating the gain difference of each lobe by mutually comparing gains of the lobes generated in the same angle of the angular power spectrum, and determining a lobe of which the gain difference of each lobe is zero as a main lobe.

11. The method of claim 8 , wherein the plurality of receiving antennas are long distance receiving antennas, and the added receiving antenna is one receiving antenna most adjacent to the long distance receiving antennas, among a plurality of short distance receiving antennas.

12. The method of claim 8 , wherein the removing comprises removing the grating lobe ghost by using a comparison result obtained by comparing a lobe width of an angular power spectrum obtained through the digital beamforming result in which the reception signals received through the plurality of receiving antennas and the reception signal received through the added receiving antenna are added with a predetermined reference width.

13. The method of claim 12 , wherein the removing comprises:

calculating a lobe width for at least one lobe of the angular power spectrum in a predetermined gain value; and

determining the lobe as the grating lobe ghost when the lobe width is equal to, or higher than, the reference width.

14. The method of claim 13 , wherein the removing further comprises determining the lobe as a main lobe when the lobe width is lower than the reference width, and removing the lobe determined as the grating lobe ghost.