Measurement of the Amplitude and Polarization of the Electric Field by Electromagnetic Infrared Thermography

The ElectroMagnetic InfraRed (EMIR) method developed and used at ONERA provides a map of the amplitude of the electric field radiated by an antenna: a thin film of low conductivity is placed in front of the EM source, the electric field induces currents which heat the film by Joule effect; this heating is measured by an infrared camera. A low-frequency modulation of the signal associated with synchronous demodulation of the images allows eliminating the parasitic thermal phenomena. By using anisotropic films with conductivity patterns, we propose here for the first time a vector measurement of the electric field. In the case of linear polarization, this technique allows to obtain the field direction, and in the case of circular polarization, to measure the axial ratio. Furthermore, we show, with the help of a patterned array, that we can obtain the spatial structure of the near field, both in amplitude and direction.