Design, Fabrication and Testing of a Corrugated Horn Antenna for Millimetre Wave Plasma Diagnostics

In the situation of energy scarcity, fusion plasma energy is one of the vital energy sources. It has many benefits like availability, safety, sustainability as compared to conventional energy sources.

Fusion plasma diagnostics are a set of methods to know the parameters of plasma. It helps in controlling the plasma position, measurement of plasma rotation through Doppler frequency shifts and to prevent the position of plasma with maintaining the gap with the side walls.

Millimetre-wave reflectometry is one of the most efficient methods of plasma diagnostics. It is an important technique to know the plasma characteristics which include, plasma density, plasma current, temperature, pressure and position, total energy contained by plasma, etc. and to control its density.

The antenna is the most crucial part of reflectometry system to detect the transmitted and reflected signals. Such an antenna should have several characteristics like high radiation efficiency, high gain, low cross-polar isolation, Gaussian-like radiation pattern, etc. All these requirements are fulfilled by a corrugated horn antenna which allows propagation of linearly polarized HE11 mode which leads to lower cross-polarization over a wideband of frequencies and many other inherent advantages.

Dr Dhaval A Pujara, Professor Department of EC Engineering, Institute of Technology, Nirma University along with his team, designed and fabricated a Corrugated Horn Antenna. The Board of Research in Nuclear Sciences, Dept. of Atomic Energy, Govt. of India, funded this research project. Fabrication of the horn was done at the Space Applications Centre (SAC-ISRO), Ahmedabad and tested in a sophisticated laboratory of the Institute for Plasma Research (IPR), Bhat, Gandhinagar.
The D-band (110 GHz – 140 GHz) corrugated horn antenna underwent every single aspect of designing, simulation, tolerance analysis and fabrication. All the design parameters and different fabrication methods for the corrugated horn antenna were also studied. The simulations were performed using CST MWS2017, HFSSv2016, and MATLAB software. The fabrication of corrugated horn antenna was quite challenging due to its inner structure with grooves of millimetre dimensions. The measured results were in close agreement with the simulated results.