Reverberation Chambers

The reverberation chamber is at the heart of many research avenues dedicated to understanding phenomena and implementing measurement protocols exploiting the fundamental properties of electromagnetic reverberation. The objective then is to propose measurement protocols for a wide variety of applications in the fields of EMC, the characterization of antennas or even materials.
Mesure SER d'une plaque en chambre réverbérante

The technical platform is made up of aset of several reverberation chambers of different sizes, 4 in number with all associated instrumentation (generation and shaping of signals, broadband amplification, advanced signal analysis, …).

Analysis and applications of technical platform

In terms of analysis of phenomena are mainly targeted :

  • etablishment of relevant statistical models depending in particular on the frequency of use (imperfectly reberberant versus perfectly reverberant) ;
  • understanding transient regime in a reverberation chamber particularly for the context of etablishing custom propagation channels ;
  • quantification of diffuse energy / coherent energy ;
  • proprieties of time reversal.

In terms of applications are primarily concerned :

  • characterization of antenna efficiency ;
  • analysis of the proprieties of EMC in radiated immunity or radiated emissivity in a reverberation chamber (development of protocols) ;
  • propagation channel stimulation ;
  • antenna radiation pattern measurement at least in the main radiation lobe ;
  • measurement of the absorbency of materials ;
  • bio-electromagnetic studies and in particular dosimetry in millimeter wave ;
  • material shielding effectiveness measurement (nested reverberation chambers).

Technical description

Reverberation chamber VHF (large reverberation chamber)

This technical platform is made up of the reverberation chamber (RC) comprising a Faraday cage provided with a mechanical stirrer as well as a set of measuring equipment allowing the installation and/or the development of measurement protocols.

Technical characteristics of RC :

  • operating frequency  > 200 MHz ;
  • enclosure dimensions  : 8.7 m x 3.7 m x 2.9 m (height) ;
  • mechanical stirrer consiting of planar blades articulated around a rotation axis ;
  • 2 technical panels each comprising : 4 N connectors, 2 SMA and 1.85 mm connectors and a 30 mm diameter waveguide ;
  • measurement system controlled by a measurement PC ;
  • control of measuring instruments Matlab.

Assistant measuring instruments :

  • RF generators, arbritrary wave generator (AWG) ;
  • amplifiers ;
  • wattmeter ;
  • digital oscilloscope ;
  • vector network analyzer 4 ports 20 GHz ;
  • spectrum analyzer ;
  • electric field probes.

Reverberation chamber SHF associated for measurements of shielding effictiveness of materials  (1 GHz - 34 GHz)

Characteristics of RC :

  • size : 65 cm × 66 cm × 67 cm (height) ;
  • material : AG3 (composed of Aluminium and Magnesium) ;
  • wall thickness : 1 cm ;
  • frequency band : 1 GHz to 34 GHz ;
  • 1 shielding gate ;
  • 2 technicals panels each comprising an 1.85 mm connector ;
  • 1 metal sample holder.

Chaotic reverberation chamber

Characteristics of chaotic reverberation chamber :

  • size : 1.75 m x 1.50 m x 2.00 m (height) ;
  • 2 technical panels each comprising : 2 N, SMA and 1.85 mm connectors and a 20 mm diameter waveguide ;
  • 2 stirrers (horizontal and vertical) ;
  • operating frequency > 600 MHz ;
  • 2 antenna supports ;
  • shielding door ;
  • metallic elements for chaoticity with attachment to the walls : 6 spherical caps and 6 hemispheres.

Assistant measuring instruments :

  • vector network analyzer 4 ports 67 GHz ;
  • same devices for the large reverberation chamber.

Reverberation chamber for animal exposition at 60 GHz (project ANSES CREOM)

Characteristics of reverberation chamber :

  • internals size : 580 mm × 592 mm × 595 mm ;
  • material : AG3 (composed of Aluminium and Magnesium) ;
  • wall thickness : 1 cm ;
  • frequency band : 55 GHz to 65 GHz ;
  • shielding door ;
  • stirrer ;
  • specificities for animal test compliance :
  • brightness : 8 windows of size 100 mm x 100 mm (top of the cage) ;
  • ventilation : 2 fans on the sides of the cage with an air flow of 5 m3/h.

 

Scientific results for the large reverberation chamber

A theoretical model(image theory) in pulsed regime of the behavior of the reverberation chamber has been proposed and validated experimentally.

Propagation channel parameter estimates have been developed in a reverberation chamber (including characterization ot the absorbency of materials).

A new method for measuring antenna radiation patterns has been developed in a reverberation chamber.

A new method for estimating the quality factor of the reverberation chamber has been developed.

A new method for mesuring the radiation efficiency of antennas from the estimation of the quality factor of the reberation chamber has been developed.

A new radar cross section (RCS) method has been developed in a reverberation chamber.

Calibration and uniformity of the temperature gradient for electromagnetic dosimetry applications.