Radar apparatus and transmission method of radar apparatus
Provided is a radar apparatus that includes: a plurality of transmission antennas including a first transmission antenna, which is connected to a first feeding line, and a second transmission antenna, which is connected to a second feeding line different from the first feeding line; and transmission circuitry, which, in operation, performs multiplexing transmission of a transmission signal, to which a phase rotation amount corresponding to a Doppler shift amount is applied, from the plurality of transmission antennas. A phase deviation due to a line length difference between the first feeding line and the second feeding line is an odd multiple of π/2.
1 . A radar apparatus, comprising:
a plurality of transmission antennas including a first transmission antenna and a second transmission antenna, the first transmission antenna connected to a first feeding line, the second transmission antenna connected to a second feeding line different from the first feeding line; and
transmission circuitry, which, in operation, performs multiplexing transmission of a transmission signal from the plurality of transmission antennas, the transmission signal being a transmission signal to which a phase rotation amount corresponding to a Doppler shift amount is applied, wherein
a phase deviation due to a line length difference between the first feeding line and the second feeding line is an odd multiple of π/2.
2 . The radar apparatus according to claim 1 , wherein
the line length difference is a half wavelength of the transmission signal or an odd multiple of the half wavelength.
3 . The radar apparatus according to claim 1 , wherein:
the plurality of transmission antennas further includes a third transmission antenna, the third transmission antenna connected to a third feeding line,
the phase deviation due to the line length difference between the first feeding line and the second feeding line further includes an odd multiple of π/4, and
a phase deviation due to a line length difference between the first feeding line and the third feeding line is an odd multiple of π/4.
4 . The radar apparatus according to claim 1 , further comprising:
a plurality of reception antennas that receives a reflected wave signal, the reflected wave signal being the transmission signal reflected by a target object; and
reception circuitry, which, in operation, demultiplexes, from the reflected wave signals, a signal having been subjected to the multiplexing transmission, and discriminates, based on a direction estimation result after correction of the phase deviation for the signal having been demultiplexed, which of the first transmission antenna and the second transmission antenna each of a plurality of the signals having been demultiplexed corresponds to.
5 . The radar apparatus according to claim 4 , wherein:
the plurality of reception antennas includes a first reception antenna and a second reception antenna, and
the first reception antenna and the second reception antenna are arranged on a straight line in a direction in which the first transmission antenna and the second transmission antenna are arranged.
6 . The radar apparatus according to claim 1 , wherein
directional gains of the first transmission antenna and the second transmission antenna differ by a predetermined value or more in a direction in which received phases of reflected wave signals are in phase, the reflected wave signals being signals respectively transmitted from the first transmission antenna and the second transmission antenna and reflected by a target object.
7 . The radar apparatus according to claim 6 , wherein
main beam directions of the first transmission antenna and the second transmission antenna differ from each other.
8 . The radar apparatus according to claim 1 , wherein
at least one of a number of the Doppler shift amounts and/or an interval between the Doppler shift amounts is variably set for each transmission period in which the transmission signal is transmitted, the number of the Doppler shift amounts and the interval between the Doppler shift amounts being set for transmission of the transmission signal.
9 . The radar apparatus according to claim 8 , wherein
among the plurality of transmission antennas, a number of transmission antennas to which the Doppler shift amounts are assigned differs between an odd-numbered transmission period and an even-numbered transmission period.
10 . The radar apparatus according to claim 9 , wherein
at least one of the Doppler shift amounts is set to the odd-numbered transmission period and the even-numbered transmission period, the Doppler shift amounts being identical to each other.
11 . The radar apparatus according to claim 9 , wherein:
in one of the odd-numbered transmission period and the even-numbered transmission period, the plurality of transmission antennas is used to transmit the transmission signal, and
in another of the odd-numbered transmission period and the even-numbered transmission period, one of the plurality of transmission antennas is used to transmit the transmission signal.
12 . The radar apparatus according to claim 9 , wherein:
in one of the odd-numbered transmission period and the even-numbered transmission period, each of the intervals between the Doppler shift amounts is an equal interval on a Doppler frequency axis, and
in another of the odd-numbered transmission period and the even-numbered transmission period, the each of the intervals between the Doppler shift amounts is an unequal interval on the Doppler frequency axis.
13 . The radar apparatus according to claim 9 , wherein:
in one of the odd-numbered transmission period and the even-numbered transmission period, one of the Doppler shift amounts is assigned to each of the first transmission antenna and the second transmission antenna, and
in another of the odd-numbered transmission period and the even-numbered transmission period, one of the Doppler shift amounts is assigned to the first transmission antenna and a plurality of the Doppler shift amounts among the Doppler shift amounts is assigned to the second transmission antenna.
14 . The radar apparatus according to claim 8 , wherein
in one of the odd-numbered transmission period and the even-numbered transmission period, the Doppler shift amounts are assigned to the plurality of transmission antennas, the Doppler shift amounts being different from each other, and
in another of the odd-numbered transmission period and the even-numbered transmission period, the Doppler shift amounts are assigned to the plurality of transmission antennas, the Doppler shift amounts being identical to each other.
15 . A radar apparatus, comprising:
a plurality of transmission antennas; and
transmission circuitry, which, in operation, performs multiplexing transmission of a transmission signal from the plurality of transmission antennas, the transmission signal being a transmission signal to which a phase rotation amount corresponding to a Doppler shift amount is applied, wherein
at least one of a number of the Doppler shift amounts and/or an interval between the Doppler shift amounts is variably set for each transmission period in which the transmission signal is transmitted, the number of the Doppler shift amounts being set for transmission of the transmission signal, the interval between the Doppler shift amounts being set for the multiplexing transmission.
16 . The radar apparatus according to claim 15 , wherein
the interval between the Doppler shift amounts is an equal interval.
17 . The radar apparatus according to claim 15 , wherein
a transmission period in which the interval between the Doppler shift amounts is an equal interval and a transmission period in which the interval between the Doppler shift amounts is an unequal interval are included.
18 . A transmission method of a radar apparatus, the transmission method comprising:
applying a phase rotation amount corresponding to a Doppler shift amount to a transmission signal; and
performing multiplexing transmission of the transmission signal from a plurality of transmission antennas, wherein
the plurality of transmission antennas includes a first transmission antenna and a second transmission antenna, the first transmission antenna connected to a first feeding line, the second transmission antenna connected to a second feeding line different from the first feeding line, and
a phase deviation due to a line length difference between the first feeding line and the second feeding line is an odd multiple of π/2.
19 . The transmission method of radar apparatus according to claim 18 , wherein at least one of a number of the Doppler shift amounts and/or an interval between the Doppler shift amounts is variably set for each transmission period in which the transmission signal is transmitted, the number of the Doppler shift amounts and the interval between the Doppler shift amounts being set for transmission of the transmission signal.
20 . The transmission method of radar apparatus according to claim 19 , wherein among the plurality of transmission antennas, a number of transmission antennas to which the Doppler shift amounts are assigned differs between an odd-numbered transmission period and an even-numbered transmission period.