Method and system for target detection using MIMO radar
A method of sensing a target in a target detection system having processing circuitry and a multiplexer coupled to the processing circuitry and to a plurality N T of transmit antennas forming a sparse transmit uniform linear array (ULA), the multiplexer being configured to generate multiplexed and phase modulated transmit signals (T 1 . . . T NT ) based on signals from a local oscillator. The processing circuitry receives signals via a plurality N R of receive antennas forming a dense receive ULA. The method includes transmitting the transmit signals via the transmit antennas as a general radiation pattern corresponding to a block circulant probing signal matrix, and receiving via the receive antennas receive signals resulting from backscattering of the transmit signals transmitted towards K targets. The method further includes processing the received reflection signals to determine the presence, range and/or angular position of a target within a field of view of the transmit antennas.
1. A method of sensing a target in a target detection system comprising processing circuitry and a multiplexer coupled to the processing circuitry and to a plurality NT of transmit antennas forming a sparse transmit uniform linear array (ULA), the multiplexer being configured to generate multiplexed and phase modulated transmit signals (T 1 . . . T NT ) based on signals from a local oscillator, the processing circuitry being further coupled for receiving signals via a plurality N R of receive antennas forming a dense receive ULA, the method comprising:
transmitting the plurality of transmit signals via the transmit antennas so as to form a general radiation pattern corresponding to a block circulant probing signal matrix, wherein an eigenvector matrix of the block circulant probing signal matrix is a Discrete Fourier Transform (DFT) matrix with orthonormal eigenvectors;
receiving via the receive antennas receive signals resulting from backscattering of the plurality of transmit signals transmitted towards K targets;
processing the received reflection signals to determine the presence, range and/or angular position of a target within a field of view of the transmit antennas; and
performing beam pattern adaptation to generate an adapted radiation pattern corresponding to an adapted block circulant probing signal matrix.
2. The method according to claim 1 , wherein the block circulant probing signal matrix {tilde over (S)} is given by
{tilde over (S)} =( {tilde over (s)} 1 . . . {tilde over (s)} i c . . . {tilde over (s)} I c )=( B 1 . . . B b . . . B N B )
where each block circulant matrix B b ∈ N T ×N T is parametrized by a single column vector c b ∈ N T ×1 .
3. The method according to claim 1 further comprising generating Quadrature Phase Shift Keyed (QPSK) signals based on pulse signals from the local oscillator.
4. The method according to claim 3 , further comprising multiplexing with the multiplexor the QPSK signals over a plurality of transmit channels, for transmission via the transmit antennas.
5. The method according to claim 4 , wherein the number of transmit channels is two.
6. The method according to claim 1 , wherein the beam pattern adaptation is performed in a single execution of an adaptation procedure.
7. The method according to claim 1 , wherein performing beam pattern adaptation includes determining an overall auto-correlation function as a superposition of N B block matrix vector auto-correlation function r(τ)=Σ b=1 N b r c b (τ), where r c b (τ)=Σ γ=1 N T [c b ] γ+τ [c b H ] γ is a block matrix vector auto-correlation function, τ is a relative shift between vector elements, N T is the number of transmit antennas and c b is a column vector which parametrizes the b-th block circulant matrix.
8. The method according to claim 1 , wherein performing beam pattern adaptation includes initializing desired beam pattern P d (φ) to a prior beam pattern from a prior target detection, or else when there is no prior beam pattern from a prior target detection the desired beam pattern is set as a constant.
9. The method according to claim 8 , further comprising generating a Fourier series approximation of desired beam pattern P d (φ), the Fourier series approximation including Fourier coefficients.
10. The method according to claim 9 , further comprising discretizing the Fourier coefficients.
11. The method according to claim 10 , further comprising mapping the discrete Fourier coefficients to an adapted block circulant probing signal matrix using the Na basis functions.
12. The method according to claim 11 , further comprising applying target detection using a matched filter output threshold and repeating the following step on the basis of the target detection applied:
determining an overall auto-correlation function as a superposition of block matrix vector auto-correlation function r(τ)=Σ b=1 N b r c b (τ), where r c b (τ)=Σ γ=1 N T [c b ] γ+τ [c b H ] γ is a block vector auto-correlation function, τ is a relative shift between vector elements, N T is the number of transmit antennas and C b is a column vector which parametrizes the b-th block circulant matrix.
13. A detection system for sensing a target, the system comprising:
a multiplexer coupled to a plurality N T of transmit antennas forming a sparse transmit uniform linear array (ULA), and a plurality N R of receive antennas forming a dense receive ULA, the multiplexer being configured to generate multiplexed transmit signals (T 1 . . . T NT ) based on signals from a local oscillator; and
processing circuitry, the processing circuitry being coupled to the multiplexer, the transmit antennas and the receive antennas and being configured to perform the method of claim 1 .
14. A vehicle comprising the detection system according to claim 13 .