Radar apparatus
A pulse transmission controller generates transmission timing signals for a high-frequency radar transmission signal in every transmission cycle. A transmission phase shifter gives a transmission signal generated by a modulator phase shifts each corresponding to a transmission cycle on the basis of the transmission timing signals generated at intervals that are equal to the transmission cycle. A reception phase shifter gives a reception signal that is output from an A/D converter reception phase shifts that are opposite in direction to the respective transmission phase shifts given by the transmission phase shifter on the basis of the transmission timing signals generated at intervals that are equal to the transmission cycle.
1. A radar apparatus comprising:
a code generator that generates complementary code sequences in every 2n transmission cycles using two or more code sequences having a prescribed code length, n being an integer that is larger than or equal to 1;
a modulator that generates a baseband transmission signal in every transmission cycle by modulating the complementary code sequences;
a transmission phase shifter that gives a phase shift to the baseband transmission signal in every 2n transmission cycles; and
an RF transmitter that converts a phase-shift-added baseband transmission signal into a radio-frequency radar transmission signal and transmits the radio-frequency radar transmission signal from a transmission antenna.
2. The radar apparatus according to claim 1 , wherein:
the code generator generates m sets of complementary code sequences in every two transmission cycles using 2m code sequences, m being an integer that is larger than or equal to 1; and
the transmission phase shifter gives a phase shift to the baseband transmission signal in every two transmission cycles.
3. The radar apparatus according to claim 1 , wherein:
the code generator generates m sets of complementary code sequences in every four transmission cycles using 2m first code sequences and 2m second code sequences obtained by inverting the polarity of the 2m first code sequences, m being an integer that is larger than or equal to 1; and
the transmission phase shifter gives a phase shift to the baseband transmission signal in every four transmission cycles.
4. The radar apparatus according to claim 1 , further comprising:
a radar receiver that detects presence/absence of a target on the basis of a reflection wave signal of the radio-frequency radar transmission signal reflected from the target,
wherein the radar receiver comprises:
an RF receiver that receives the reflection wave signal with a reception antenna, and converts the received reflection wave signal into a baseband reception signal;
a reception phase shifter that gives the baseband reception signal an opposite phase shift that is opposite in polarity to the phase shift in every 2n transmission cycles;
a correlation value calculator that calculates correlation values between an opposite-phase-shift-added baseband reception signal and the complementary code sequences; and
a coherent integrator that adds together the correlation values a prescribed number of times.
5. A transmission method of a radar transmission signal, comprising:
generating complementary code sequences in every 2n transmission cycles using two or more code sequences having a prescribed code length, n being an integer that is larger than or equal to 1;
generating a baseband transmission signal in every transmission cycle by modulating the complementary code sequences;
giving a phase shift to the baseband transmission signal in every 2n transmission cycles;
converting a phase-shift-added baseband transmission signal into a radio-frequency radar transmission signal; and
transmitting the radio-frequency radar transmission signal from a transmission antenna.
6. The transmission method of a radar transmission signal according to claim 5 , wherein:
m sets of complementary code sequences are generated in every two transmission cycles using 2m code sequences, m being an integer that is larger than or equal to 1; and
the baseband transmission signal is given a phase shift in every two transmission cycles.
7. The transmission method of a radar transmission signal according to claim 5 , wherein:
m sets of complementary code sequences are generated in every four transmission cycles using 2m first code sequences and 2m second code sequences obtained by inverting the polarity of the 2m first code sequences, m being an integer that is larger than or equal to 1; and
the baseband transmission signal is given a phase shift in every four transmission cycles.
8. A target detection method of a radar apparatus, comprising:
receiving, with a reception antenna, a radio-frequency reflection wave signal reflected from a target;
converting the received reflection wave signal into a baseband reception signal;
giving an opposite phase shift to the baseband reception signal in every 2n transmission cycles, n being an integer that is larger than or equal to 1;
calculating correlation values between an opposite-phase-shift-added baseband reception signal and complementary code sequences;
subjecting the correlation values to coherent integration a prescribed number of times; and
detecting presence/absence of the target on the basis of a value obtained by the coherent integration, wherein:
the radio-frequency reflection wave signal is a radio-frequency radar transmission signal transmitted from a transmission antenna of the radar apparatus;
the radio-frequency radar transmission signal is a signal obtained by frequency-converting a phase-shift-added baseband transmission signal;
the phase-shift-added baseband transmission signal is obtained by giving a phase shift to the baseband transmission signal in every 2n transmission cycles;
the phase shift is opposite in polarity to the opposite phase shift;
the baseband transmission signal is generated by modulating complementary code sequences; and
the complementary code sequences are generated in every 2n transmission cycles using two or more code sequences having a prescribed code length.