TEM horn antenna

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Schematic representation of the structure of a TEM horn
Prototype of a TEM antenna. The second metal surface is on the underside. In between the existing as an insulator and for shaping plastic.

A TEM horn antenna ( English TEM horn antenna ) is a design of a very wideband Prüfantenne for microwaves and consisting of a combination of two electrically insulated from each other, the shape of a Exponentialtrichters approximated metal surfaces. In contrast to the similarly constructed in the outer shape of horn the two metallic outer surfaces of the TEM horn radiator constitute the active part of the antenna. It is thus a line-conducted electromagnetic wave, the transverse mode (TEM wave) directly radiated, which also the name derives from this antenna design. The structure of the TEM horn antenna is roughly comparable to a TEM cell "cut open" in the middle and normal to the direction of radiation . The feed can take place via a balun in order to connect the coaxial feed line symmetrically to the two metal surfaces.

The TEM horn antenna is used to generate fields in the context of EMC measurements and EMC tests for electromagnetic compatibility , especially when testing radiated interference immunity . The test object is exposed to radiation in the immediate vicinity of the antenna and the reaction of the test object is evaluated. Further applications are in the field of medical diagnostics such as the examination for the detection of breast cancer .

The shape and design of the two metal surfaces in the horn allows the field configuration in the vicinity of the antenna to be influenced and, for example, very homogeneous illumination of the test object to be achieved. The non-metallic areas of the horn are formed from non-conductive carrier materials such as glass fiber reinforced plastic to shape the antenna . The TEM wave emitted by the horn ensures that a field wave resistance of approx. 377 Ω is established in the near range as in the far field , and that conclusions from the near range to the far range are possible within the scope of the measurement. The usable frequency range, depending on the shape and size of the horn, is in the frequency range from a few 10  MHz to a few 100 GHz and, due to the broadband properties of the antenna, covers a few powers of ten.

Individual evidence

  1. ↑ Chriss A. Grosvenor, et al .: TEM Horn Antenna Design Principles . The National Institute of Standards and Technology (NIST), 2007 ( Online - Technical Note (NIST TN) - 1544).
  2. ^ TEM Horn Antenna for ultra-wide band microwave breast imaging. (PDF) Retrieved May 23, 2016 .