Radar apparatus
Provided is a radar apparatus that detects a target object with high accuracy. The radar apparatus includes: transmission circuitry, which, in operation, alternately outputs a first transmission signal with a first central frequency and a second transmission signal with a second central frequency higher than the first central frequency for each transmission period; and one or a plurality of transmission antennas, which, in operation, transmit the fast transmission signal and the second transmission signal. The second central frequency is higher than a frequency (1+1/Nc) times the first central frequency, where Nc is an integer indicating a number of times of transmission of each of the first transmission signal and the second transmission signal for the each transmission period within a predetermined duration.
1. A radar apparatus, comprising:
transmission circuitry, which, in operation, outputs a first transmission signal with a first central frequency and a second transmission signal with a second central frequency for each transmission period, the second central frequency being higher than the first central frequency; and
one or a plurality of transmission antennas, which, in operation, transmit the first transmission signal and the second transmission signal, wherein:
the second central frequency is higher than a frequency (1+1/N c ) times the first central frequency, where N c is an integer indicating a number of times of transmission of each of the first transmission signal and the second transmission signal for the each transmission period within a predetermined duration.
2. The radar apparatus according to claim 1 , wherein the second central frequency is lower than a frequency 1.25 times the first central frequency.
3. The radar apparatus according to claim 1 , wherein the second central frequency is lower than a frequency (7/6) times the first central frequency.
4. The radar apparatus according to claim 1 , wherein the one or plurality of transmission antennas alternately transmit the first transmission signal and the second transmission signal for the each transmission period.
5. The radar apparatus according to claim 1 , wherein the one or plurality of transmission antennas simultaneously transmit the first transmission signal and the second transmission signal for the each transmission period.
6. The radar apparatus according to claim 5 , wherein:
the one or plurality of transmission antennas are a plurality of transmission antennas, and
a number of transmission antennas transmitting the first transmission signal and a number of transmission antennas transmitting the second transmission signal are identical or differ by one in the plurality of transmission antennas.
7. The radar apparatus according to claim 1 , further comprising:
a reception antenna, which, in operation, receives a first reflected wave signal and a second reflected wave signal, the first reflected wave signal being the first transmission signal reflected by a target, the second reflected wave signal being the second transmission signal reflected by the target; and
reception circuitry including first Doppler frequency analysis circuitry, second Doppler frequency analysis circuitry, and determination circuitry, the first Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a first Doppler frequency from the first reflected wave signal, the second Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a second Doppler frequency from the second reflected wave signal, the determination circuitry being circuitry, which, in operation, determines a number of times of aliasing of the first Doppler frequency and a number of times of aliasing of the second Doppler frequency, wherein
the determination circuitry estimates a first peak position of the first Doppler frequency, the first peak position being observed in the first reflected wave signal,
the determination circuitry estimates a second peak position of the second Doppler frequency based on a ratio of the first central frequency to the second central frequency, and
the determination circuitry determines a number of times of aliasing of a Doppler frequency of the target based on a degree of agreement between the second peak position and a third peak position observed in the second reflected wave signal.
8. The radar apparatus according to claim 1 , wherein:
the one or plurality of transmission antennas are a plurality of transmission antennas, and
the transmission circuitry gives a Doppler shift amount with intervals to at least one of the first transmission signal and the second transmission signal that are transmitted from the plurality of transmission antennas, the intervals being obtained by unequally dividing a Doppler frequency range based on which a number of times of aliasing of a Doppler frequency is determined.
9. The radar apparatus according to claim 8 , wherein in a case where the intervals of the Doppler shift amount are
Δ
f
DDM
=
1
T
rs
(
N
t
+
δ
)
,
[
1
]
where Nt is an integer indicating a number of the plurality of transmission antennas, δ is an integer of one or more, and T rs is a transmission period in which a set of the first transmission signal and the second transmission signal is transmitted, the second central frequency is higher than a frequency
N
C
N
C
-
(
N
t
+
δ
)
[
2
]
times the first central frequency, the intervals being unequally divided.
10. The radar apparatus according to claim 9 , further comprising:
a reception antenna, which, in operation, receives a plurality of first reflected wave signals and a plurality of second reflected wave signals, each of the plurality of first reflected wave signals being the first transmission signal reflected by a plurality of targets, each of the plurality of second reflected wave signals being the second transmission signal reflected by the plurality of targets; and
reception circuitry including first Doppler frequency analysis circuitry, second Doppler frequency analysis circuitry, and determination circuitry, the first Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a first Doppler frequency from the plurality of first reflected wave signals, the second Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a second Doppler frequency from the plurality of second reflected wave signals, the determination circuitry being circuitry, which, in operation, determines a number of times of aliasing of the first Doppler frequency and a number of times of aliasing of the second Doppler frequency, wherein
the determination circuitry determines a number of times of aliasing of each Doppler frequency of the plurality of targets based on intervals of peak positions between the plurality of targets and the intervals of the Doppler shift amount based on a Doppler frequency estimated by one of the first Doppler frequency analysis circuitry and the second Doppler frequency analysis circuitry, the one of the first Doppler frequency analysis circuitry and the second Doppler frequency analysis circuitry being circuitry in which the plurality of first reflected wave signals and the plurality of second reflected wave signals are demultiplexed.
11. The radar apparatus according to claim 9 , further comprising:
a reception antenna, which, in operation, receives a plurality of first reflected wave signals and a plurality of second reflected wave signals, each of the plurality of first reflected wave signals being the first transmission signal reflected by a plurality of targets, each of the plurality of second reflected wave signals being the second transmission signal reflected by the plurality of targets; and
reception circuitry including first Doppler frequency analysis circuitry, second Doppler frequency analysis circuitry, and determination circuitry, the first Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a first Doppler frequency from the plurality of first reflected wave signals, the second Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a second Doppler frequency from the plurality of second reflected wave signals, the determination circuitry being circuitry, which, in operation, determines a number of times of aliasing of the first Doppler frequency and a number of times of aliasing of the second Doppler frequency, wherein
the reception circuitry includes direction estimation circuitry, which, in operation, performs directional estimation based on a Doppler frequency estimated by one of the first Doppler frequency analysis circuitry and the second Doppler frequency analysis circuitry, the one of the first Doppler frequency analysis circuitry and the second Doppler frequency analysis circuitry being circuitry in which the plurality of first reflected wave signals and the plurality of second reflected wave signals are demultiplexed.
12. The radar apparatus according to claim 5 , further comprising:
a reception antenna, which, in operation, receives a first reflected wave signal and a second reflected wave signal, the first reflected wave signal being the first transmission signal reflected by a target, the second reflected wave signal being the second transmission signal reflected by the target; and
reception circuitry including first Doppler frequency analysis circuitry, second Doppler frequency analysis circuitry, and determination circuitry, the first Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a first Doppler frequency from the first reflected wave signal, the second Doppler frequency analysis circuitry being circuitry, which, in operation, estimates a second Doppler frequency from the second reflected wave signal, the determination circuitry being circuitry, which, in operation, determines a number of times of aliasing of the first Doppler frequency and a number of times of aliasing of the second Doppler frequency, wherein
the reception antenna includes a first reception antenna and a second reception antenna,
the first Doppler frequency analysis circuitry processes the first reflected wave signal received by the first reception antenna in one transmission period of an even-numbered transmission period and an odd-numbered transmission period, and processes the first reflected wave signal received by the second reception antenna in another transmission period of the even-numbered transmission period and the odd-numbered transmission period, and
the second Doppler frequency analysis circuitry processes the second reflected wave signal received by the second reception antenna in the one transmission period, and processes the second reflected wave signal received by the first reception antenna in the other transmission period.
13. The radar apparatus according to claim 5 , further comprising:
a plurality of reception antennas including a first reception antenna and a second reception antenna;
first reception circuitry, which, in operation, mixes a signal received by the first reception antenna for each first period by using the first transmission signal to output a first reflected wave signal, and, which, in operation, mixes the signal received by the first reception antenna for each second period by using the second transmission signal to output a second reflected wave signal, the first reflected wave signal being a signal reflected by a target, the second reflected wave signal being a signal reflected by the target, the second period differing from the first period; and
second reception circuitry, which, in operation, mixes a signal received by the second reception antenna for the each first period by using the second transmission signal to output the second reflected wave signal, and, which, in operation, mixes the signal received by the second reception antenna for the each second period by using the first transmission signal to outputs the first reflected wave signal.
14. The radar apparatus according to claim 1 , wherein:
the first transmission signal and the second transmission signal are chirp signals, and
the chirp signal of the first central frequency and the chirp signal of the second central frequency have an identical frequency sweep bandwidth.
15. The radar apparatus according to claim 14 , wherein the chirp signal of the first central frequency and the chirp signal of the second central frequency have different frequency sweep bandwidths.
16. The radar apparatus according to claim 5 , further comprising:
a first reception antenna, which, in operation, receives a first reflected wave signal that is the first transmission signal reflected by a target;
a second reception antenna, which, in operation, receives a second reflected wave signal that is the second transmission signal reflected by the target;
first reception circuitry, which, in operation, processes the first reflected wave signal; and
second reception circuitry, which, in operation, processes the second reflected wave signal, wherein
the transmission circuitry includes first transmission circuitry, which, in operation, outputs the first transmission signal, and second transmission circuitry, which, in operation, outputs the second transmission signal,
the one or plurality of transmission antennas include a first transmission antenna, which, in operation, transmits the first transmission signal, and a second transmission antenna, which, in operation, transmits the second transmission signal,
the first transmission antenna, the first transmission circuitry, the first reception antenna, and the first reception circuitry are included in a first chip, and
the second transmission antenna, the second transmission circuitry, the second reception antenna, and the second reception circuitry are included in a second chip.
17. The radar apparatus according to claim 5 , further comprising:
a first reception antenna, which, in operation, receives a first reflected wave signal and a second reflected wave signal, the first reflected wave signal being the first transmission signal reflected by a target, the second reflected wave signal being the second transmission signal reflected by the target;
a second reception antenna, which, in operation, receives the first reflected wave signal and the second reflected wave signal;
first reception circuitry processes the first reflected wave signal received by the first reception antenna in one transmission period of an even-numbered transmission period and an odd-numbered transmission period, and processes the second reflected wave signal received by the first reception antenna in another transmission period of the even-numbered transmission period and the odd-numbered transmission period; and
second reception circuitry processes the second reflected wave signal received by the second reception antenna in the one transmission period, and processes the first reflected wave signal received by the second reception antenna in the other transmission period, wherein
the transmission circuitry includes first transmission circuitry, which, in operation, outputs the first transmission signal, and second transmission circuitry, which, in operation, outputs the second transmission signal,
the one or plurality of transmission antennas include a first transmission antenna, which, in operation, transmits the first transmission signal, and a second transmission antenna, which, in operation, transmits the second transmission signal,
the first transmission antenna, the first transmission circuitry, the first reception antenna, and the first reception circuitry are included in a first chip, and
the second transmission antenna, the second transmission circuitry, the second reception antenna, and the second reception circuitry are included in a second chip.
18. A radar apparatus, comprising:
transmission circuitry, which, in operation, gives a Doppler shift amount with intervals to a first transmission signal with a first central frequency and a second transmission signal with a second central frequency, the second central frequency being higher than the first central frequency, the intervals being obtained by unequally dividing a Doppler frequency range based on which a number of times of aliasing of a Doppler frequency is determined; and
a plurality of transmission antennas, which, in operation, transmits the first transmission signal and the second transmission signal each being a signal to which the Doppler shift amount is given, wherein
the transmission circuitry outputs the first transmission signal and the second transmission signal for each transmission period,
the second central frequency is higher than a frequency (1+1/N c ) times the first central frequency, where N c is an integer indicating a number of times of transmission of each of the first transmission signal and the second transmission signal for the each transmission period within a predetermined duration, and
in a case where the intervals of the Doppler shift amount are
Δ
f
DDM
=
1
T
rs
(
N
t
+
δ
)
,
[
3
]
where Nt is an integer indicating a number of the plurality of transmission antennas, δ is an integer of one or more, and T rs is a transmission period in which a set of the first transmission signal and the second transmission signal is transmitted, the second central frequency is higher than a frequency
N
C
N
C
-
(
N
t
+
δ
)
[
4
]
times the first central frequency, the intervals being unequally divided.