Resolving a multipath ambiguity in a tdm-mimo radar

A signal processing device comprising processing circuitry configured to resolve, in a virtual array signal comprising at least one range-Doppler bin, a first-order multipath ambiguity for a virtual array of time-division multiplexing, TDM, multiple-input multiple-output, MIMO, frequency-modulated continuous-wave, FMCW, radar, wherein:

• the TDM MIMO FMCW radar comprises at least one row of physical receivers with a first spacing in a first direction, and further comprises a plurality of physical transmitters arranged with a second spacing in said first direction, and
• the virtual array comprises a plurality of subarrays, each subarray generated by a combination of the row of physical receivers and one of the physical transmitters;
• whereby the signal device:
• obtains a virtual array signal of a range-Doppler bin relating to a scene, each element of the virtual array signal corresponding to one virtual antenna element of the virtual array;
• computes a full-array angle spectrum based on all elements of the virtual array signal;
• computes at least one single-subarray angle spectrum based on the virtual array signal restricted to one of the subarrays;
• assesses whether a peak in the full-array angle spectrum is co-located with a corresponding baseline peak in a computed single-subarray angle spectrum;
• whereby;
• if the peak and the baseline peak are co-located, concluding that the peak in the full-array angle spectrum represents a direct reflection in the scene;
• and,
• if the peak and the baseline peak are not co-located, concluding that the peak in the full-array angle spectrum represents a first-order multipath artefact.

A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out a method of resolving a first-order multipath ambiguity for a virtual array of a time-division multiplexing, TDM, multiple-input multiple-output, MIMO, frequency-modulated continuous-wave, FMCW, radar, wherein:

• the TDM MIMO FMCW radar comprises at least one row of physical receivers with a first spacing in a first direction, and further comprises a plurality of physical transmitters arranged with a second spacing in said first direction, and
• the virtual array comprises a plurality of subarrays, each subarray generated by a combination of the row of physical receivers and one of the physical transmitters, the method comprising:
• obtaining a virtual array signal of a range-Doppler bin relating to a scene, each element of the virtual array signal corresponding to one virtual antenna element of the virtual array;
• computing a full-array angle spectrum based on all elements of the virtual array signal;
• computing at least one single-subarray angle spectrum based on the virtual array signal restricted to one of the subarrays;
• assessing whether a peak in the full-array angle spectrum is co-located with a corresponding baseline peak in a computed single-subarray angle spectrum;
• if the peak and the baseline peak are co-located, concluding that the peak in the full-array angle spectrum represents a direct reflection in the scene;
• and,
• if the peak and the baseline peak are not co-located, concluding that the peak in the full-array angle spectrum represents a first-order multipath artefact.