Real-time, cross-correlating millimetre-wave imaging system

A method of receiving millimetre wave radiation, said method including the steps of:

• scanning a field of view using a fan beam to receive millimetre wave radiation;
• rotating polarization of incident millimetre wave radiation through 90 degrees;
• and
• scanning said field of view using another fan beam to receive said polarization-rotated millimetre wave radiation, said fan beams intersecting and being geometrically orthogonal to each other, and said radiation being co-polarized.

An antenna for receiving millimetre wave radiation, said antenna including:

• a fan beam antenna for receiving millimetre wave radiation by scanning a field of view using a first fan beam;
• a filter for rotating polarization of incident millimetre wave radiation through 90 degrees;
• and
• another fan beam antenna for receiving said polarization-rotated millimetre wave radiation by scanning a field of view using a second fan beam, said fan beams intersecting and being geometrically orthogonal to each other, and said radiation being co-polarized.

A method of receiving millimetre wave radiation for generating an image, said method including the steps of:

• receiving millimetre wave radiation in accordance with first and second fan beams, wherein said first and second fan beams are geometrically orthogonal to each other and intersecting, said millimetre wave radiation received in accordance with said second fan beam being co-polarized with said millimetre wave radiation received in accordance with said first fan beam;
• downconverting components of said millimetre wave radiation received in accordance with said first and second beams to generate respective intermediate frequency (IF) signals;
• cross-correlating said IF signals;
• and
• filtering the resulting cross-correlated signal to provide a value proportional to brightness at each point in the scene.

An apparatus for receiving millimetre wave radiation for generating an image, said apparatus including:

• a receiver for receiving millimetre wave radiation in accordance with first and second fan beams, wherein said first and second fan beams are geometrically orthogonal to each other and intersecting, said millimetre wave radiation received in accordance with said second fan beam being co-polarized with said millimetre wave radiation received in accordance with said first fan beam;
• a downconverter for downconverting components of said millimetre wave radiation received in accordance with said first and second beams to generate respective intermediate frequency (IF) signals;
• a correlator for cross-correlating said IF signals;
• and
• a filter for filtering the resulting cross-correlated signal to provide a value proportional to brightness at each point in the scene.

A millimetre wave imaging method, said method including the steps of:

• receiving millimetre wave radiation, said receiving step including:
• receiving millimetre wave radiation by scanning a field of view using a fan beam;
• rotating polarization of incident millimetre wave radiation through 90 degrees;
• and
• receiving said polarization rotated millimetre wave radiation by scanning a field of view using another fan beam, said fan beams intersecting and being geometrically orthogonal to each other;
• processing said received millimetre wave radiation, said processing step including:
• receiving components of millimetre wave radiation from said antenna received in accordance with said fan beams;
• downconverting respective components of said received millimetre wave radiation received to generate respective intermediate frequency (IF) signals;
• cross-correlating said IF signals;
• and
• filtering the resulting cross-correlated signal to produce a filtered, cross-correlated signal proportional to brightness at each point in said field of view as said antenna beams are scanned;
• building up said image using said filtered, cross-correlated signal.

A millimetre wave imaging system, including:

• means for receiving millimetre wave radiation, said receiving means including:
• a fan beam antenna for receiving millimetre wave radiation by scanning a field of view using a fan beam;
• means for rotating polarization of incident millimetre wave radiation through 90 degrees;
• and
• another fan beam antenna for receiving said polarization rotated millimetre wave radiation by scanning a field of view using another fan beam, said fan beams intersecting and being geometrically orthogonal to each other;
• a millimetre wave receiver coupled to said antenna, including:
• first and second receivers respectively coupled to said fan beam antennas respectively for receiving millimetre wave radiation in accordance with said fan beams;
• downconverters for downconverting respective components of said received millimetre wave radiation received from said first and second receivers to generate respective intermediate frequency (IF) signals;
• a correlator for cross-correlating said IF signals;
• and
• a filter for filtering the resulting cross-correlated signal to produce a filtered, cross-correlated signal proportional to brightness in said field of view as said antenna beams are scanned;
• a processing unit for building up said image using said filtered, cross-correlated signal.