Radar device
A radar device includes: a transmission beam controller that selects, every first period, a transmission beam set used for transmission of a radar signal from among a plurality of transmission beam sets each including at least two transmission beam directions; and a radar transmitter that transmits the radar signal in a predetermined transmission period by using the selected transmission beam set, wherein the transmission beam controller switching, every second period within the first period, among the at least two transmission beam directions included in the transmission beam set.
1. A radar device comprising:
a transmission beam controller, which, in operation, selects a transmission beam set used for transmission of a radar signal from among a plurality of transmission beam sets, each of the plurality of transmission beam sets including at least two transmission beams having different directions, the transmission beams of the plurality of transmission beam sets having different directions from each other, the transmission beam controller, in operation, switches the at least two transmission beams included in the selected transmission beam set; and
a radar transmitter, which, in operation, transmits the radar signal in a predetermined transmission period by using at least one of the at least two transmission beams included in the selected transmission beam set, wherein
the transmission beam controller, in operation, switches, in each of multiple first periods, the selected transmission beam set from one of the plurality of transmission beam sets to another of the plurality of transmission beam sets,
the transmission beam controller, in operation, switches, in each of multiple second periods within each of the multiple first periods, from a transmission beam from one of the at least two transmission beams included in the selected transmission beam set to another of the at least two transmission beams included in the selected transmission beam set, and
each of the transmission beams included in the selected transmission beam set within each of the multiple first periods is transmitted in at least two of the multiple second periods within each of the multiple first periods.
2. The radar device according to claim 1 , further comprising:
a receiver, which, in operation, receives a reflected signal which is the radar signal reflected by a target;
a coherent integration processor, which, in operation, performs, in each of the multiple second periods, coherent integration with respect to the received reflected signal; and
a Doppler frequency analyzer, which, in operation, performs Doppler frequency analysis with respect to a coherent integration result.
3. The radar device according to claim 2 , wherein
a length of each of the multiple second periods is equal to a multiplication result of the predetermined transmission period and an additional amount of the reflected signal in the coherent integration processor; and
a length of each of the multiple first periods is equal to a multiplication result of one of the multiple second periods, a number of the transmission beams included in transmission beam set in the one of the multiple second periods, and an additional amount of the coherent integration result in the Doppler frequency analyzer.
4. The radar device according to claim 1 , wherein
a length of each of the multiple second periods has a variable length.
5. The radar device according to claim 4 , wherein
the length of each of the multiple second periods varies depending on a directivity gain of a corresponding one of the transmission beams; and
a second period of the multiple second periods that has a longest length is for a transmission beam in which the directivity gain is lowest out of the at least two transmission beams having different directions.
6. The radar device according to claim 4 , wherein
in a case where the radar device is mounted in a vehicle, the length of a second period of the multiple second periods for a transmission beam corresponding to a front direction of the vehicle is longer than for a transmission beam corresponding to a lateral direction of the vehicle out of the at least two transmission beams having different directions.
7. The radar device according to claim 1 , wherein
in a case where the radar device is mounted in a vehicle, the transmission beam controller adjusts a number of the transmission beams included in each of the plurality of transmission beam sets in accordance with a speed of the vehicle; and
the number of the transmission beams in a case where the speed of the vehicle is equal to or lower than a predetermined threshold value is larger than that in a case where the speed of the vehicle exceeds the predetermined threshold value.
8. The radar device according to claim 1 , wherein
in a case where the radar device is mounted in a vehicle, the transmission beam controller adjusts a number of the transmission beams included in each of the plurality of transmission beam sets and a length of each of the multiple second periods in accordance with speed of the vehicle;
the number of the transmission beams in a case where the speed of the vehicle exceeds a predetermined threshold value is smaller than that in a case where the speed of the vehicle is equal to or lower than the predetermined threshold value; and
the length of each of the multiple second periods in the case where the speed of the vehicle exceeds the predetermined threshold value is longer than in the case where the speed of the vehicle is equal to or lower than the predetermined threshold value.
9. The radar device according to claim 1 , wherein a length of each of the multiple first periods is integral multiple of a length of each of the multiple second periods.
10. A radar device comprising:
a transmission beam controller, which, in operation, selects a transmission beam set used for transmission of a radar signal from among a plurality of transmission beam sets, each of the plurality of transmission beam sets including at least four transmission beams having different directions, the transmission beam controller, in operation, switches the at least four transmission beams included in the selected transmission beam set; and
a radar transmitter, which, in operation, transmits the radar signal in a predetermined transmission period by using at least one of the at least four transmission beams included in the selected transmission beam set, wherein
the transmission beam controller, in operation, selects, in each of multiple first periods, the transmission beam set used for transmission of the radar signal, and switches, in each of multiple second periods within each of the multiple first periods, from a transmission beam from one of the at least four transmission beams included in the selected transmission beam set to another of the at least four transmission beams included in the selected transmission beam set,
each of the transmission beams included in the selected transmission beam set within each of the multiple first periods is transmitted in at least two of the multiple second periods within each of the multiple first periods, and
each of transmission beams selected from the at least four transmission beams in one period of the multiple first periods is different from each of transmission beams selected from the at least four transmission beams in another period of the multiple first periods.
11. The radar device according to claim 10 , further comprising:
a receiver, which, in operation, receives a reflected signal which is the radar signal reflected by a target;
a coherent integration processor, which, in operation, performs, in each of the multiple second periods, coherent integration with respect to the received reflected signal; and
a Doppler frequency analyzer, which, in operation, performs Doppler frequency analysis with respect to a coherent integration result.
12. The radar device according to claim 11 , wherein
a length of each of the multiple second periods is equal to a multiplication result of the predetermined transmission period and an additional amount of the reflected signal in the coherent integration processor; and
a length of each of the multiple first periods is equal to a multiplication result of one of the multiple second periods, a number of the transmission beams included in transmission beam set in the one of the multiple second periods, and an additional amount of the coherent integration result in the Doppler frequency analyzer.
13. The radar device according to claim 10 , wherein
a length of each of the multiple second periods has a variable length.
14. The radar device according to claim 13 , wherein
the length of each of the multiple second periods varies depending on a directivity gain of a corresponding one of the transmission beams; and
a second period of the multiple second periods that has a longest length is for a transmission beam in which the directivity gain is lowest out of the at least four transmission beams having different directions.
15. The radar device according to claim 13 , wherein
in a case where the radar device is mounted in a vehicle, the length of a second period of the multiple second periods for a transmission beam corresponding to a front direction of the vehicle is longer than for a transmission beam corresponding to a lateral direction of the vehicle out of the at least four transmission beams having different directions.
16. The radar device according to claim 10 , wherein
in a case where the radar device is mounted in a vehicle, the transmission beam controller adjusts a number of the transmission beams included in each of the plurality of transmission beam sets in accordance with a speed of the vehicle; and
the number of the transmission beams in a case where the speed of the vehicle is equal to or lower than a predetermined threshold value is larger than that in a case where the speed of the vehicle exceeds the predetermined threshold value.
17. The radar device according to claim 10 , wherein
in a case where the radar device is mounted in a vehicle, the transmission beam controller adjusts a number of the transmission beams included in each of the plurality of transmission beam sets and a length of each of the multiple second periods in accordance with speed of the vehicle;
the number of the transmission beams in a case where the speed of the vehicle exceeds a predetermined threshold value is smaller than that in a case where the speed of the vehicle is equal to or lower than the predetermined threshold value; and
the length of each of the multiple second periods in the case where the speed of the vehicle exceeds the predetermined threshold value is longer than in the case where the speed of the vehicle is equal to or lower than the predetermined threshold value.
18. The radar device according to claim 10 , wherein a length of each of the multiple first periods is integral multiple of a length of each of the multiple second periods.
19. A radar device comprising:
a transmission beam controller, which, in operation, selects a transmission beam set used for transmission of a radar signal from among a plurality of transmission beam sets, each of the plurality of transmission beam sets including at least two transmission beams having different directions, the transmission beam controller, in operation, switches the at least two transmission beams included in the selected transmission beam set; and
a radar transmitter, which , in operation, transmits the radar signal in a predetermined transmission period by using at least one of the at least two transmission beams included in the selected transmission beam set, wherein
the transmission beam controller, in operation, selects, every first period, the transmission beam set used for transmission of the radar signal, and switches, every second period within the first period, from a transmission beam from one of the at least two transmission beams included in the selected transmission beam set to another of the at least two transmission beams included in the selected transmission beam set,
the length of the second period varies depending on a directivity gain of a corresponding one of the transmission beams, and
the second period has a longest length for a transmission beam in which the directivity gain is lowest out of the at least two transmission beams having different directions.
20. A radar device comprising:
a transmission beam controller, which, in operation, selects a transmission beam set used for transmission of a radar signal from among a plurality of transmission beam sets, each of the plurality of transmission beam sets including at least two transmission beams having different directions, the transmission beam controller, in operation, switches the at least two transmission beams included in the selected transmission beam set; and
a radar transmitter, which, in operation, transmits the radar signal in a predetermined transmission period by using at least one of the at least two transmission beams included in the selected transmission beam set, wherein
in a case where the radar device is mounted in a vehicle, the transmission beam controller adjusts a number of the transmission beams included in each of the plurality of transmission beam sets in accordance with a speed of the vehicle, and
the number of the transmission beams in a case where the speed of the vehicle is equal to or lower than a predetermined threshold value is larger than that in a case where the speed of the vehicle exceeds the predetermined threshold value.