A 190GHz active millimeter-wave imager

The design and testing of a 190 GHz imaging system is presented. The system features two beam-scanning antennas; the first transmits a horizontal fan beam and the second receives a vertical fan beam. By correlating the signals from the antennas, an estimate of the millimeter-wave reflectivity at the intersection of the fan beams is obtained. Each fan beam is scanned by rotating a small subreflector within the antenna; this simple rotation motion allows rapid scanning. The system is portable, currently approximately 0.6m × 0.6m × 2m high; the key size constraint is imposed by the 450 mm aperture length of the antennas. The imager has an angular resolution of 0.25° and a field of view of 14°×14°, resulting in a raw image of approximately 50 × 50 pixels. The raw image is processed using super-resolution techniques. Images will be presented which show the capability of the system to image metallic and ceramic objects beneath clothing. These images were obtained by illuminating the scene with signals from a frequency-doubled Gunn oscillator. While this paper focuses on active imaging, the system can also operate in passive mode with reduced sensitivity.

[1]  Doc Ewen,et al.  Radiometric one-second camera (ROSCAM) airborne evaluation , 1999, Defense, Security, and Sensing.

[2]  Duncan A. Robertson,et al.  Compact real-time (video rate) passive millimeter-wave imager , 1999, Defense, Security, and Sensing.

[3]  J. W. Archer,et al.  176-200-GHz RECEIVER MODULE USING INDIUM PHOSPHIDE AND GALLIUM ARSENIDE MMICs , 2004 .

[4]  Bradley T. Blume,et al.  Passive millimeter-wave imaging model application and validation , 1997, Defense, Security, and Sensing.

[5]  Larry Yujiri,et al.  Passive millimeter-wave camera flight tests , 2000, Defense, Security, and Sensing.

[6]  Christopher A. Martin,et al.  Real-time passive millimeter-wave imaging from a helicopter platform , 2000, Defense, Security, and Sensing.

[7]  Erich N. Grossman,et al.  Active millimeter-wave imaging for concealed weapons detection , 2003, SPIE Defense + Commercial Sensing.

[8]  L. Yujiri,et al.  Passive Millimeter Wave Imaging , 2003, 2006 IEEE MTT-S International Microwave Symposium Digest.

[9]  G.P. Timms,et al.  A beam-scanning dual-polarized fan-beam antenna suitable for Millimeter wavelengths , 2005, IEEE Transactions on Antennas and Propagation.

[10]  Dennis Lo,et al.  Passive millimeter-wave camera , 1997, Defense, Security, and Sensing.

[11]  David D. Ferris,et al.  Overview of current technology in MMW radiometric sensors for law enforcement applications , 2000, Defense, Security, and Sensing.