Methods and apparatus for velocity detection in MIMO radar including velocity ambiguity resolution
In accordance with described examples, a method determines if a velocity of an object detected by a radar is greater than a maximum velocity by receiving on a plurality of receivers at least one frame of chirps transmitted by at least two transmitters and reflected off of the object. A velocity induced phase shift (φ d ) in a virtual array vector S of signals received by each receiver corresponding to a sequence of chirps (frame) transmitted by each transmitter is estimated. Phases of each element of virtual array vector S are corrected using φ d to generate a corrected virtual array vector S c . A first Fourier transform is performed on the corrected virtual array vector S c to generate a corrected virtual array spectrum to detect a signature that indicates that the object has an absolute velocity greater than a maximum velocity.
1. A circuit comprising:
a port adapted to be coupled to a receiver and configured to receive chirps;
a processor coupled to the port and configured to:
estimate a phase shift (φ d ) in a virtual array vector S of signals based on the chirps received by the port;
correct phases of each element of virtual array vector S using φ d to generate a corrected virtual array vector S c ;
perform a Fourier transform on the corrected virtual array vector S c to generate a corrected virtual array spectrum; and
analyze the corrected virtual array spectrum to detect a signature that indicates that an object corresponding to the detected signature has an absolute velocity greater than a maximum velocity.
2. The circuit of claim 1 in which the processor is further configured to correct the corrected virtual array vector S c using a phase error vector corresponding to the detected signature and perform a second Fourier transform on a resulting matrix to determine if the signature is removed from the resulting matrix.
3. The circuit of claim 1 in which the processor is configured to calculate a velocity of the object using formulas
v
est
=
φ
d
λ
4
π
T
c
,
where T c is a chirp period and λ is a wavelength of the chirps and v true =v est +2v max , if v est <0, v true =v est −2v max , if v est >0, where v true is the correct velocity and v max is determined by the formula
v
max
=
λ
4
T
c
.
4. The circuit of claim 1 in which the processor further determines if the signature is caused by multiple objects by analyzing S c .
5. A method comprising:
receiving, by a receiver, chirps;
estimating a phase shift (φ d ) in a virtual array vector S of signals based on the received chirps;
correcting phases of each element of virtual array vector S using φ d to generate a corrected virtual array vector S c ;
performing a Fourier transform on the corrected virtual array vector S c to generate a corrected virtual array spectrum; and
analyzing the corrected virtual array spectrum to detect a signature that indicates that an object corresponding to the detected signature has an absolute velocity greater than a maximum velocity.
6. The method of claim 5 further comprising correcting the corrected virtual array vector S c using a phase error vector corresponding to the detected signature and performing a second Fourier transform on a resulting matrix to determine if the signature is removed from the resulting matrix.
7. The method of claim 5 further comprising determining a velocity of the object by using formulas
v
est
=
φ
d
λ
4
π
T
c
,
where T c is a chirp period and λ is a wavelength of the chirps v true =v est +2v max , if v est <0, or v true =v est −2v max , if v est >0, where v true is the correct velocity and v max is determined by the formula
v
max
=
λ
4
T
c
.
8. The method of claim 5 further comprising determining if the signature is caused by multiple objects by analyzing S c .
9. A radar system comprising:
a receiver configured to receive chirps;
a processor coupled to the receiver and configured to:
estimate a phase shift (φ d ) in a virtual array vector S of signals based on the received chirps;
correct phases of each element of virtual array vector S using φ d to generate a corrected virtual array vector S c ;
perform a Fourier transform on the corrected virtual array vector S c to generate a corrected virtual array spectrum; and
analyze the corrected virtual array spectrum to detect a signature that indicates that an object corresponding to the detected signature has an absolute velocity greater than a maximum velocity.
10. The radar system of claim 9 in which the processor is further configured to correct the corrected virtual array vector S c using a phase error vector corresponding the signature and perform a second Fourier transform on a resulting matrix to determine if the signature is removed from the resulting matrix.
11. The radar system of claim 9 in which the processor further determines a velocity of the object.
12. The radar system of claim 11 in which the processor further determines a velocity of the object using formulas
v
est
=
φ
d
λ
4
π
T
c
,
where T c is a chirp period and λ is a wavelength of the chirps and v true =v est +2v max , if v est < 0 , or v true =v est −2v max , if v est >0, where v true is the correct velocity and v max is determined by the formula
v
max
=
λ
4
T
c
.
13. The radar system of claim 9 in which the processor is further configured to determine if the signature is caused by multiple objects by analyzing S c .