Phased-MIMO radar with frequency diversity for increased system flexibility

Phased-multiple-input multiple-output (MIMO) radar enjoys the advantages of MIMO radar in diversity gain without sacrificing the main advantage of phased-array radar in coherent transmit gain. However, a limitation of the phased-MIMO radar is that the beam steering is fixed in an angle for all the ranges. This limits the system performance to mitigate non-desirable range-dependent interferences. To overcome this disadvantage, this paper proposes a flexible phased-MIMO radar with frequency diversity. This approach divides the transmit antenna array into multiple subarrays that are allowed to overlap, each subarray coherently transmits a distinct waveform, which is orthogonal to the waveforms transmitted by other subarrays, at a distinct transmit frequency. Each subarray forms a range-dependent beam and all beams may be steered to different ranges or directions. The subarrays jointly offer flexible operating modes such as MIMO radar, phased-array radar, and phased-MIMO radar.