Inverse synthetic aperture, multiband radar detection of hidden objects with spatially structured tracking of object carrier

A system for detecting and classifying concealed items, comprising:

• a three-dimensional (3D) geometric tracker, configured to detect within a monitor area a position of a subject and an orientation of the subject, and correspondingly generate a subject 3D position data and a subject 3D orientation data;
• a multiband inverse synthetic aperture array radar (ISAR) system, coupled to the 3D geometric tracker, comprising:
• a plurality of first frequency band radar receivers (RXs), respectively located at different first frequency receiving positions that are within and/or adjacent the monitoring area, and
• a plurality of second frequency band radar RXs, respectively located at different second frequency receiving positions that are within and/or adjacent the monitoring area,
• wherein the multiband ISAR system is configured to:
• transmit, from a first position, a first frequency band radar signal that is generated based at least in part on a first transmit oscillator signal and is configured to illuminate the subject sufficiently to produce, in instances of a concealed item on the subject, a plurality of different angles of scatter of the first frequency band radar signal from the concealed item, at least two of which are received at respective ones among the plurality of first frequency band radar RXs, including:
• a first angle of scatter of the first frequency band radar signal, received at a first of the first frequency band radar RXs as a received first angle of scatter of the first frequency band radar signal, and
• a second angle of scatter of the first frequency band radar signal, received at a second of the first frequency band radar RXs as a received second angle of scatter of the first frequency band radar signal,
• transmit, from a second position, a second frequency band radar signal that is based at least in part on a second transmit oscillator signal and is configured to illuminate the subject sufficiently to produce, in the instances of a concealed item on the subject, a plurality of different angles of scatter of the second frequency band radar signal from the concealed item, at least two of which are received by respective ones among the plurality of second frequency band RCs, including:
• a first angle of scatter of the second frequency band radar signal, received at a first of the second frequency band radar RXs as a received first angle of scatter of the second frequency band radar signal, and
• a second angle of scatter of the second frequency band radar signal, received at a second of the second frequency band radar RXs as a received second angle of scatter of the second frequency band radar signal,
• wherein the multiband ISAR system further comprises:
• a first interferometer, configured to generate a first frequency first angle interferometric measurement, based at least in part on the received first angle of scatter of the first frequency band radar signal and a first oscillator signal that is synchronous with the first transmit oscillator signal,
• a second interferometer, configured to generate a first frequency second angle interferometric measurement, based at least in part on the received second angle of scatter of the first frequency band radar signal and a third oscillator signal that is synchronous with the first transmit oscillator signal,
• a third interferometer, configured to generate a second frequency first angle interferometric measurement, based at least in part on the received first angle of scatter of the second frequency band radar signal and a third oscillator signal that is synchronous with the second transmit oscillator signal,
• a fourth interferometer, configured to generate a second frequency second angle interferometric measurement, based at least in part on the received second angle of scatter of the second frequency band radar signal and a fourth oscillator signal that is synchronous with the second transmit oscillator signal;
• a processing logic, configured to perform a tomographic image construction process, comprises steps that include:
• constructing a first frequency tomographic image of the concealed item on the subject, which comprises a tomographic combining of the first frequency first angle interferometric measurement and the first frequency second angle interferometric measurement that includes an aligning of the first frequency first angle interferometric measurement and the first frequency first angle interferometric measurement, which is configured such that instances of ambiguities arise and is further configured to include resolving, based at least in part on the subject 3D position data and the subject 3D orientation data, of said instances of ambiguities the first frequency
• construct a second frequency tomographic image of the concealed item on the subject, by a tomographic processing that is based at least on the second frequency first angle interferometric measurement and the second frequency second angle interferometric measurement and further based at least in part on the subject 3D position data and the subject 3D orientation data the first frequency;
• and
• a processing logic, which is configured to determine, based at least in part on the first frequency tomographic image, or the second frequency tomographic image, or both, whether a threat likelihood meets a trigger threshold and, in response to a positive determination, to activate an alarm.