  Several computational imaging systems have recently been proposed at
microwave and millimeter-wave frequencies enabling a fast and low cost
reconstruction of the scattering strength of a scene. The quality of the
reconstructed images is directly linked to the degrees of freedom of the system
which are the number of uncorrelated radiated patterns that sequentially sample
the scene. Frequency diverse antennas such as leaky chaotic cavities and
metamaterial apertures take advantage of the spectral decorrelation of
transmitted speckle patterns that stems from the reverberation within a medium.
We present a reconfigurable chaotic cavity for which the boundary conditions
can be tuned by exciting plasma elements, here commercial fluorescent lamps.
The interaction of electromagnetic waves with a cold plasma is strongly
modified as it is ionized. Instead of being transparent to incident waves, it
behaves theoretically as a metallic material. The independent states of the
cavity obtained using a differential approach further enhance the degrees of
freedom. This relaxes the need of a cavity with a large bandwidth and/or high
quality factor. Experimental results validate the use of fluorescent lamps and
its limitations are discussed. Images of various metallic objects are provided
to illustrate the potentialities of this promising solution.
