A radar device includes a transmitting antenna unit, a modulator, a receiving antenna unit, a receiver, and a processor. The transmitting antenna unit includes transmitting antennas. The modulator generates transmission signals respectively provided to the transmitting antennas by executing phase-shift keying through diverging the common signal into diverged signals having the number being equal to the number of the transmitting antennas and rotating respective phases of the diverged signals. The receiving antenna unit includes at least one receiving antenna. The receiver generates a received code of at least one received signal. The received code is acquired by encoding an appearance pattern of a peak of at least one received signal on a Doppler frequency axis. The processor generates information related to an object, according to the received code generated by the receiver. The modulator executes the phase-shift keying by using a linear block code as an assigned code.
1 . A radar device comprising:
a transmitting antenna unit including a plurality of transmitting antennas;
an oscillator configured to generate a common signal having a continuous wave;
a modulator configured to generate a plurality of transmission signals respectively provided to the plurality of transmitting antennas by executing phase-shift keying, the phase-shift keying including
diverging the common signal into a plurality of diverged signals, number of the plurality of diverged signals being equal to number of the plurality of transmitting antennas, and
rotating respective phases of the plurality of diverged signals by different amounts of phase rotation;
a receiving antenna unit including at least one receiving antenna;
a receiver configured to
acquire at least one received signal received by the receiving antenna unit,
generate a received code by encoding an appearance pattern of a peak of the at least one received signal on a Doppler frequency axis; and
a processor configured to generate information related to an object that reflects a wave radiated from the transmitting antenna unit, according to the received code generated by the receiver,
wherein
an assigned code is defined as a code acquired by encoding an appearance pattern of a peak that is expected to appear on the Doppler frequency axis when the object is stationary, and
the modulator is further configured to execute the phase-shift keying using a linear block code as the assigned code.
2 . The radar device according to claim 1 , wherein the modulator is further configured to execute the phase-shift keying by using the assigned code having a minimum Hamming distance being two or larger with respect to a code group having a cyclic code acquired by cyclically shifting the assigned code.
3 . The radar device according to claim 1 , wherein the modulator is further configured to execute the phase-shift keying by using the assigned code having a minimum Hamming distance being three or larger with respect to a code group having a cyclic code acquired by cyclically shifting the assigned code to be three or larger.
4 . The radar device according to claim 1 , wherein the modulator is further configured to execute the phase-shift keying by using the assigned code having a code polynomial being divisible by a polynomial having a length larger than or equal to a code length of the code polynomial.
5 . The radar device according to claim 1 , wherein the modulator is further configured to execute the phase-shift keying by satisfying C<D, where:
C denotes maximum number of overlapping bits in a code group having a cyclic code acquired by cyclically shifting the assigned code; and
D denotes a shortest Hamming distance in the code group.
6 . The radar device according to claim 1 , wherein the modulator is further configured to execute the phase-shift keying by using one of a Hamming code, a cyclic redundancy check code, a Bose-Chaudhuri-Hocquenghem code, a cyclic Golay code, and a M-sequence code as the assigned code.
7 . The radar device according to claim 1 , wherein the modulator is further configured to execute a bit expansion in which a one-bit symbol being 0 or 1 is added to the assigned code so that the assigned code has a code length being in a power of two.
8 . The radar device according to claim 1 , wherein the modulator is further configured to execute the phase-shift keying by
setting a code group having arbitrary cyclic codes acquired by cyclically shifting the assigned code, number of the arbitrary cyclic codes being larger than or equal to number of a plurality of objects overlapped each other, and
generating a result of a logical sum operation of the assigned code and each of the arbitrary cyclic codes as a distinct code to be used as the assigned code.
9 . The radar device according to claim 1 , further comprising:
a metric calculator configured to acquire a function of cross-correlation between the assigned code and the received code.
10 . The radar device according to claim 1 , further comprising:
a metric calculator configured to compare the received code with overlapping pattern data to calculate a difference between the received code and the overlapping pattern data,
wherein the overlapping pattern data preliminarily stores all or a part of expected values of the received code that are expected when a plurality of objects are present.
11 . The radar device according to claim 9 , wherein
the metric calculator is further configured to compare a calculation result of the function of the cross-correlation between the assigned code and the received code with correlation-calculation result data to calculate a difference between the calculation result and the correlation-calculation result data, and
the correlation-calculation result data preliminarily stores a part of all of calculation results of the cross-correlation between the received code expected when a plurality of objects are present and the assigned code by which the at least one received signal is acquired.
12 . The radar device according to claim 10 , wherein the metric calculator is further configured to calculate the difference between the received code and the overlapping pattern data based on a Hamming distance.
13 . The radar device according to claim 9 , further comprising:
an estimator configured to:
detect a first peak in a calculation result of the function of the cross-correlation between the assigned code and the received code through threshold processing or optimum processing, the threshold processing adopting a threshold value to extract the first peak from the calculation result, the optimum processing acquiring a maximum value, a minimum value or an extreme value of the calculation result to extract the first peak;
detect a second peak acquired by comparing the at least one received signal with correlation-calculation result data, the correlation-calculation result data preliminarily storing a part or all of calculation results of cross-correlation between the assigned code by which the at least one received signal is acquired and each of expected values of the received code that are expected when a plurality of objects are present; and
compare the first peak with the second peak to estimate an overlapping state of the object.
14 . The radar device according to claim 9 , further comprising:
an estimator configured to:
detect a first peak in a calculation result of the function of the cross-correlation between the assigned code and the received code;
detect a second peak acquired by comparing the calculation result with overlapping pattern data, the overlapping pattern data preliminarily storing all or a part of expected values of the received code expected when a plurality of objects are present; and
compare the first peak with the second peak to estimate an overlapping state of the object.
15 . The radar device according to claim 1 , wherein
the modulator is further configured to execute the phase-shift keying by using one of a Hamming code, a cyclic redundancy check code, a Bose-Chaudhuri-Hocquenghem code, and a cyclic Golay code as the assigned code.
16 . The radar device according to claim 1 , wherein
the assigned code is also used as an error correction code.
17 . The radar device according to claim 1 , wherein
the assigned code is a binary code, and
a number of bits set to “1” in the assigned code is equal to a number of the plurality of transmitting antennas.
18 . The radar device according to claim 1 , wherein
the processor is further configured to:
set the assigned code for each of the plurality of transmitting antennas; and
determine amount of phase rotation of a signal transmitted from each of the plurality of transmitting antennas according to the assigned code.
19 . The radar device according to claim 1 , wherein
a number of the respective phases used in the phase-shift keying is equal to two times of a number of the plurality of transmitting antennas.
20 . The radar device according to claim 1 , wherein
the processor is configured to:
execute analysis of cross-correlation relation between the assigned code that is output from the modulator and the received code that is output from the receiver; and
generate information of the object based on a result of the analysis.
21 . The radar device according to claim 1 , wherein
the processor is configured to:
execute separation of the plurality of transmitting signals by comparing (i) a result of an OR operation between the assigned code and a code group having cyclic codes acquired by cyclically shifting the assigned code, with (ii) the received code; and
evaluate reliability of a result of the separation.
22 . The radar device according to claim 20 , wherein
the processor includes a database that stores the assigned code, and
the processor is configured to read out the assigned code from the database prior to the analysis of the cross-correlation relation.
23 . The radar device according to claim 1 , further comprising
a metric calculator configured to compare the received code with overlapping pattern data to calculate a difference between the received code and the overlapping pattern data,
wherein
correlation-calculation result data is acquired by preliminarily calculating all or a part of a calculation result of cross-correlation between an expected value of the received code and the assigned code assumed in a case where multiple objects are present, and
the processor is further configured to estimate a peak in a cross-correlation between the calculation result and the correlation-calculation result data.