A distributed aperture radar system comprising first and second small aperture radar devices (10, 201,20, 202) that are physically distributed from one another and connected to a radar control processing unit, the first small aperture radar device (10, 201) comprising a first plurality of transmit 1 (TX 1,1, TX 1,2) and receive (RX 1,1, RX 1,2) antennas coupled to a first signal processor component that is configured to generate at least a first mono-static multiple-input-multiple-output, MIMO, virtual array aperture and a first bi-static MIMO virtual array aperture in response to a first radar signal transmitted, respectively, from the first small aperture radar device (10,201) or the second small aperture radar device (20, 202); the second small aperture radar device (20, 202) comprising a second plurality of transmit (TX 2,1, TX 2,2) and receive (RX 2,1, RX 2,2) antennas coupled to a second signal processor component that is configured to generate at least a second mono-static MIMO virtual array aperture and a second bi-static MIMO virtual array aperture in response to a second radar signal transmitted, respectively, from the second small aperture radar device or the first small aperture radar device; and wherein the radar control processing unit is configured: to control respective transmitter modules (11, 21) in the first and second distributed radar devices to operate by transmitting MIMO waveforms for use in constructing a virtual aperture from a combination of the distributed apertures formed by the distributed transmit and receive antennas; to coherently combine virtual array apertures from the first and second distributed radar devices to construct an extended bi-static MIMO virtual array aperture that is larger than the first or second bi-static MIMO virtual array apertures, and to construct a bi-static MIMO forward difference virtual array aperture by performing forward difference co-array processing on the extended bi-static MIMO virtual array aperture to fill in holes in the extended bi-static MIMO virtual array aperture, thereby mitigating or suppressing spurious sidelobes caused by gaps or holes in the extended bi-static MIMO virtual array aperture. the first small aperture radar device (10, 201) comprising a first plurality of transmit 1 (TX 1,1, TX 1,2) and receive (RX 1,1, RX 1,2) antennas coupled to a first signal processor component that is configured to generate at least a first mono-static multiple-input-multiple-output, MIMO, virtual array aperture and a first bi-static MIMO virtual array aperture in response to a first radar signal transmitted, respectively, from the first small aperture radar device (10,201) or the second small aperture radar device (20, 202); the second small aperture radar device (20, 202) comprising a second plurality of transmit (TX 2,1, TX 2,2) and receive (RX 2,1, RX 2,2) antennas coupled to a second signal processor component that is configured to generate at least a second mono-static MIMO virtual array aperture and a second bi-static MIMO virtual array aperture in response to a second radar signal transmitted, respectively, from the second small aperture radar device or the first small aperture radar device; and wherein the radar control processing unit is configured: to control respective transmitter modules (11, 21) in the first and second distributed radar devices to operate by transmitting MIMO waveforms for use in constructing a virtual aperture from a combination of the distributed apertures formed by the distributed transmit and receive antennas; to coherently combine virtual array apertures from the first and second distributed radar devices to construct an extended bi-static MIMO virtual array aperture that is larger than the first or second bi-static MIMO virtual array apertures, and to construct a bi-static MIMO forward difference virtual array aperture by performing forward difference co-array processing on the extended bi-static MIMO virtual array aperture to fill in holes in the extended bi-static MIMO virtual array aperture, thereby mitigating or suppressing spurious sidelobes caused by gaps or holes in the extended bi-static MIMO virtual array aperture. to control respective transmitter modules (11, 21) in the first and second distributed radar devices to operate by transmitting MIMO waveforms for use in constructing a virtual aperture from a combination of the distributed apertures formed by the distributed transmit and receive antennas; to coherently combine virtual array apertures from the first and second distributed radar devices to construct an extended bi-static MIMO virtual array aperture that is larger than the first or second bi-static MIMO virtual array apertures, and to construct a bi-static MIMO forward difference virtual array aperture by performing forward difference co-array processing on the extended bi-static MIMO virtual array aperture to fill in holes in the extended bi-static MIMO virtual array aperture, thereby mitigating or suppressing spurious sidelobes caused by gaps or holes in the extended bi-static MIMO virtual array aperture.