Radar device, signal processor, and signal processing method
To provide a radar device capable of improving azimuth estimation accuracy by compensating the Doppler phase shift of a moving target in a TDMA FMCW MIMO radar device. Provided is a radar device that allows transmitting antennas to perform transmission by performing sequential switching such that antenna element numbers are anterior-posterior symmetrical centering on a reference time and synthesizes a beat signal at the reference time from a first beat signal received by a receiving antenna before the reference time and a second beat signal received after the reference time.
1. A radar device, comprising:
at least two transmitting antennas;
at least one receiving antenna;
a local oscillator, wherein the local oscillator outputs a local signal;
a transmission processing unit, wherein the transmission processing unit sequentially transmits the local signal as a transmission signal from a selected one of the transmitting antennas such that the transmitting antenna transmission times are anterior-posterior symmetrical centered on a reference time;
a reception processing unit, wherein the reception processing unit outputs a beat signal from an echo signal obtained from a reflection of the transmission signal from a target and the local signal, and wherein the echo signal is received by the receiving antenna; and
a signal processing unit that performs signal processing on the beat signal, wherein the signal processing unit synthesizes a synthesized beat signal at the reference time from a first beat signal received by the receiving antenna before the reference time and a second beat signal received after the reference time.
2. The radar device according to claim 1 , wherein the signal processing unit obtains an amplitude of the synthesized beat signal at the reference time by averaging an amplitude of the first beat signal and an amplitude of the second beat signal and obtains a phase of the synthesized beat signal at the reference time by adding a phase of the first beat signal and a phase of the second beat signal.
3. The radar device according to claim 1 , wherein the signal processing unit synthesizes a frequency spectrum of the synthesized beat signal at the reference time from a first frequency spectrum obtained by performing discrete Fourier transform on the first beat signal and a second frequency spectrum obtained by performing the discrete Fourier transform on the second beat signal.
4. The radar device according to claim 1 , wherein the signal processing unit sets the first beat signal or the second beat signal as the synthesized beat signal at the reference time if an average of an amplitude of the first beat signal and an amplitude of the second beat signal is equal to or less than a predetermined value.
5. The radar device according to claim 4 , wherein the predetermined value is a predetermined ratio of the amplitude of the first beat signal or the amplitude of the second beat signal.
6. The radar device according to claim 1 , wherein the radar device is mounted on a vehicle.
7. The radar device according to claim 1 , further comprising:
a plurality of switches, wherein one switch is provided for each of the transmission antennas, and wherein each switch is selectively connected to the local oscillator by the transmission processing unit.
8. The radar device according to claim 7 , further comprising:
a plurality of power amplifiers, wherein at least one power amplifier is located between each switch and each respective transmission antenna.
9. The radar device according to claim 1 , further comprising:
a plurality of receiving antennas.
10. The radar device according to claim 9 , further comprising:
a plurality of mixers, wherein one mixer is provided for each of the receiving antennas.
11. The radar device according to claim 1 , wherein the local signal output by the local oscillator increases linearly from a chirp start frequency over a ramp time.
12. The radar device according to claim 11 , wherein each transmission signal is transmitted for a time period that is equal to the ramp time.
13. A signal processor, comprising:
a signal processing unit configured to perform signal processing on a beat signal generated from an echo signal obtained from a reflection of a transmission signal that is sequentially transmitted from each transmitting antenna in a plurality of transmitting antennas at times that are anterior-posterior symmetrical centered around a reference time from a target and a local signal, the transmission signal being based on the local signal, wherein the signal processing unit synthesizes a synthesized beat signal at the reference time from a first beat signal received by the receiving antenna before the reference time and a second beat signal received after the reference time.
14. A signal processing method, comprising:
transmitting a local signal from a plurality of transmitting antennas by performing sequential switching such that transmission times of the transmitting antennas are anterior-posterior symmetrical centered around a reference time;
generating a first beat signal, wherein the first beat signal is generated by mixing the local signal with received signals received by at least a first receiving antenna generated from an echo signal obtained from a reflection of each of a first number of the transmission signals that are transmitted before the reference time;
generating a second beat signal, wherein the second beat signal is generated by mixing the local signal with received signals received by at least the first receiving antenna generated from an echo signal obtained from a reflection of each of the first number of the transmission signals that are transmitted after the reference time; and
outputting a distance and an azimuth angle to a target.