Radar device
A plurality of transmission antennas include Nt1 transmission antennas arranged in a first direction and Nt2 transmission antennas arranged in a second direction orthogonal to the first direction, a plurality of reception antennas include Na1 reception antennas arranged in the first direction and Na2 reception antennas arranged in the second direction. In the first direction, an inter-element space between any two of the Nt1 transmission antennas and an inter-element space between any two of the Na1 reception antennas are each a value which is a product of a first space and an integer and are all values different from each other, and in the second direction, an inter-element space between any two of the Nt2 transmission antennas and an inter-element space between any two of the Na2 reception antennas are each a value which is a product of a second space and an integer and are all values different from each other.
1. A radar device comprising:
a radar transmitter which, in operation, transmits a plurality of radar signals at predetermined transmission cycles from a plurality of transmission antennas; and
a radar receiver which, in operation, receives a plurality of reflected wave signals being the plurality of radar signals reflected on a target, by using a plurality of reception antennas, wherein
the plurality of transmission antennas include Nt1 transmission antennas arranged in a first direction and Nt2 transmission antennas arranged in a second direction orthogonal to the first direction,
the plurality of reception antennas include Na1 reception antennas arranged in the first direction and Na2 reception antennas arranged in the second direction,
in the first direction, each of distances between adjacent two of the Nt1 transmission antennas and adjacent two of the Na1 reception antennas is an integer multiple of a first distance, and all of the distances between the adjacent two of the Nt1 transmission antennas and the adjacent two of the Na1 reception antennas are different from each other, and
in the second direction, each of distances between adjacent two of the Nt2 transmission antennas and adjacent two of the Na2 reception antennas is an integer multiple of a second distance, and all of the distances between the adjacent two of the Nt2 transmission antennas and the adjacent two of the Na2 reception antennas are different from each other.
2. The radar device according to claim 1 , wherein
a sum of all of distances between the adjacent two of the transmission antennas in the first direction is smaller than a smallest value of all of distances between the adjacent two of the reception antennas in the first direction, Nt1 being three or more, or
a sum of all of distances between the adjacent two of the reception antennas in the first direction is smaller than a smallest value of all of distances between the adjacent two of the transmission antennas in the first direction, Na1 being three or more.
3. The radar device according to claim 1 , wherein
the radar receiver receives the plurality of reflected wave signals as signals received by using a virtual reception array formed by the plurality of transmission antennas and the plurality of reception antennas,
the virtual reception array includes Nt1×Na1 virtual antenna elements arranged in the first direction, and
in the virtual reception array, each of distances between adjacent two of the Nt1×Na1 virtual antenna elements arranged in the first direction is a first integer multiple of the first distance, the first integer being one or more, and distances between adjacent two of the Nt1×Na1 virtual antenna elements arranged in the first direction include second integer multiples of the first distance, the second integers including all integers from 1 to a first predetermined value.
4. The radar device according to claim 1 , wherein
the radar receiver receives the plurality of reflected wave signals as signals received by using a virtual reception array formed by the plurality of transmission antennas and the plurality of reception antennas,
the virtual reception array includes Nt2×Na2 virtual antenna elements arranged in the second direction, and
in the virtual reception array, each of distances between adjacent inter element spaces each between any two of the Nt2×Na2 virtual antenna elements arranged in the second direction is a first integer multiple of the first distance, the first integer being one or more, and distances between adjacent two of the Nt2×Na2 virtual antenna elements arranged in the second direction include second integer multiples of the first distance, the second integers including all integers from 1 to a second predetermined value.
5. The radar device according to claim 1 , wherein
at least one of the plurality of transmission antennas and the plurality of reception antennas is formed of a plurality of sub-arrayed antenna elements,
a width of each of the plurality of sub-arrayed antenna elements in the first direction is one wavelength or more, and a difference between at least one of distances between the adjacent two of the Nt1 transmission antennas and at least one of distances between the adjacent two of the Na1 reception antennas is smaller than one wavelength, and
a width of each of the plurality of sub-arrayed antenna elements in the second direction is one wavelength or more, and a difference between at least one of distances between the adjacent two of the Nt2 transmission antennas and at least one of distances between the adjacent two of the Na1 reception antennas is smaller than one wavelength.
6. The radar device according to claim 1 , wherein
the radar receiver receives the plurality of reflected wave signals as signals received by using a virtual surface-arranged array antenna in which elements are virtually arranged at positions indicated by inter-element vectors at all of elements in a virtual reception array formed by the plurality of transmission antennas and the plurality of reception antennas,
the virtual reception array includes Nt1×Na1 virtual antenna elements arranged in the first direction, and
in the virtual reception array, each of distances between adjacent two of the Nt1×Na1 virtual antenna elements arranged in the first direction is a first integer multiple of the first distance, the first integer being one or more, and distances between adjacent two of the Nt1×Na1 virtual antenna elements arranged in the first direction include second integer multiples of the first distance, the second integers including all integers from 1 to a first predetermined value.
7. The radar device according to claim 1 , wherein
the radar receiver receives the plurality of reflected wave signals as signals received by using a virtual surface-arranged array antenna in which elements are virtually arranged at positions indicated by inter-element vectors at all of elements in a virtual reception array formed by the plurality of transmission antennas and the plurality of reception antennas,
the virtual reception array includes Nt2×Na2 virtual antenna elements arranged in the second direction, and
in the virtual reception array, each of distances between adjacent two of the Nt2×Na2 virtual antenna elements arranged in the second direction is a first integer multiple of the first distance, the first integer being one or more, and distances between adjacent two of the Nt2×Na2 virtual antenna elements arranged in the second direction include second integer multiples of the first distance, the second integers including all integers from 1 to a second predetermined value.
8. The radar device according to claim 1 , wherein
the plurality of transmission antennas includes a total of Nt transmission antennas, Nt being a natural number and being three or more,
the plurality of transmission antennas are arranged such that the Nt1 transmission antennas are arranged in the first direction and the Nt2 transmission antennas are arranged in the second direction, wherein Nt1 and Nt2 satisfy a first condition that Nt equals Nt1+Nt2−1 and that Nt1×Nt2 has a takes the largest value under the first condition,
the plurality of reception antennas includes a total of Na reception antennas, Na being a natural number and being three or more, and
the plurality of reception antennas are arranged such that the Na1 reception antennas are arranged in the first direction and the Na2 reception antennas are arranged in the second direction, wherein Na1 and Na2 satisfy a second condition that Na equals Na1+Na2-1 and that Na1×Na2 has a largest value under the second condition.
9. The radar device according to claim 1 , wherein a set of the plurality of transmission antennas and a set of the plurality of reception antennas are each arranged in a L-shape, a T-shape, or a cross shape.
10. The radar device according to claim 1 , wherein
Nt1 is smaller than Na1, and
in the first direction, a largest value of all of distances between the adjacent two of the Nt1 transmission antennas is larger than a largest value of all of distances between the adjacent two of the Na1 reception antennas.
11. The radar device according to claim 1 , wherein
Na1 is smaller than Nt1, and
in the first direction, a largest value of all of distances between the adjacent two of the Na1 reception antennas is larger than a largest value of all of distances between the adjacent two of the Nt1 transmission antennas.
12. The radar device according to claim 1 , wherein
Nt2 is smaller than Na2, and
in the second direction, a largest value of all of distances between the adjacent two of the Nt2 transmission antennas is larger than a largest value of all of distances between the adjacent two of the Na2 reception antennas.
13. The radar device according to claim 1 , wherein
Na2 is smaller than Nt2, and
in the second direction, a largest value of all of distances between the adjacent two of the Na2 reception antennas is larger than a largest value of all of distances between the adjacent two of the Nt2 transmission antennas.