Frequency-Dimension Virtual Array Expansion in MIMO Radars for Improved Angular Resolution

Poor angular resolution is a major problem in modern radar systems. The multiple input and multiple output (MIMO) radar uses N transmitters and N receivers to equivalently form N2virtual elements to expand the aperture. However, this level of virtual array expansion is not enough to further improve the angular resolution and reduce the number of transceiver elements. In this work, we use an additional dimension to further expand the virtual array. By stimulating the array with k different frequencies, we can expand the virtual elements to N2kin addition to MIMO operation. The simulation results show that with 4 transmitters and 4 receivers, we can achieve 0.35° angular resolution when exciting the array with 1-GHz and 4-GHz signals. Furthermore, we set up a proof-of-concept frequency-modulated continuous-wave (FMCW) radar experiment with 1 transmitter and 4 receivers to achieve 12.3° angular resolution. Our proposed virtual array expansion technique can significantly reduce the number of transceivers and antenna elements in MIMO radars and improve angular resolution.