Dr. Gregory L. Charvat

Harmonic Radar

Harmonic Radar

This was a remote sensing project jointly developed by the Dow Chemical Company and the MSU Electromagnetics Research Group.

Harmonic radar:

  • Transmits at 917 MHz
  • Radiated transmission excites a radar ‘tag’
  • Tag receives 917 MHz, doubles the frequency, and re-radiates 1834 MHz back to the receiver
  • Useful for detecting a tagged target in a high clutter environment
  • Applications include detection of corrosion, remote sensing, tracking specific targets, etc.


A method for detecting a latent environmental effect (such as a corrosive environment under insulation) or a latent structural change (such as a crack in a concealed structural member) at a known remote concealed location. The method of the instant invention includes three steps. The first step is to use a harmonic electromagnetic transponder at the known remote concealed location of the latent environmental effect or the latent structural change, the harmonic electromagnetic transponder having a reactive portion which reacts to the latent environmental effect or latent structural change to modify the harmonic emission of the transponder. The second step is to remotely interrogate the transponder by directing electromagnetic radiation at the transponder. The third step is to use the harmonic emission of the transponder to remotely determine the latent environmental effect or the latent structural change.

(abstract from US Patent 7,145,453)