V. V. Biryukov – Dr.Sc. (Eng.), Professor, Department of Physics and Technology of Optical Communication,

Nizhny Novgorod State Technical University n.a. R.E. Alekseev

V. L. Vaks – Ph.D. (Phys.-Math.), Head of Terahertz Spectroscopy Department, Institute for Physics of Microstructures of the Russian Academy of Sciences; Professor, Department of Physics and Technology of Optical Communication,

Nizhny Novgorod State Technical University n.a. R.E. Alekseev

K. I. Kisilenko – Senior Lecturer, Department of Physics and Technology of Optical Communication,

Nizhny Novgorod State Technical University n.a. R.E. Alekseev

V. A. Malakhov – Dr.Sc. (Eng.), Professor, Department of Physics and Technology of Optical Communication,

Nizhny Novgorod State Technical University n.a. R.E. Alekseev

A. N. Panin – Leading Engineer, Institute for Physics of Microstructures of the Russian Academy of Sciences

S. I. Pripolzin – Leading Engineer, Institute for Physics of Microstructures of the Russian Academy of Sciences A. S. Raevskij – Dr.Sc. (Phys.-Math.), Professor, Head of Department of Physics and Technology of Optical Communication, Nizhny Novgorod State Technical University n.a. R.E. Alekseev E-mail: raevsky_as@mail.ru

V. V. Shcherbakov – Ph.D. (Eng.), Associate Professor, Department of Physics and Technology of Optical Communication, Nizhny Novgorod State Technical University n.a. R.E. Alekseev

The article presents the results of calculation and measurement of the main characteristics of the Cassegrain antenna, intended for using in the high-speed wireless communication system at a frequency of 220 GHz.

To calculate the geometric parameters of the antenna at the initial design stage, the method of geometric optics is used. Further calculation of the Cassegrain antenna characteristics is carried out using the CST Microwave Studio program, which is designed for three-dimensional electrodynamic modeling of microwave devices and provides the ability to calculate each individual element as part of the design.

The proposed method, compared with a technique based on the principles of geometric optics, makes it possible to determine tolerances for manufacturing of individual antenna elements, to take into account inaccuracies in manufacturing and tuning of the antenna, such as mismatch of the geometric symmetry axes of a horn, a subreflector and a primary mirror, offset of the antenna elements in the focal plane and along the axis of symmetry of the antenna, and also it allows you to trace changes in the antenna characteristics when changing a frequency.

Using the proposed calculation method, a Cassegrain antenna has been designed and manufactured. It has a diameter of primary and auxiliary mirrors of 200 mm and 16 mm, respectively. A pyramidal horn fed by a rectangular waveguide section of 1,092 x 0,546 mm has been used as an irradiator for the antenna system. Experimental study of the Cassegrain antenna has been carried out according to the standard measurement method in the far-field zone. Comparison of the calculation results and measurements of the antenna parameters makes it possible to propose a procedure for calculating the Cassegrain antenna, which allows saving the computation time and computing resources. First, the geometrical parameters of the antenna are calculated using the geometric optics method, based on the required gain. Then the antenna feed is calculated. Next, using the three-step method, the antenna characteristics are calculated, in order to achieve the maximum gain value by performing parametric optimization of its geometrical parameters. The final step is calculation using the one-step method in order to obtain a more accurate value of the antenna gain.

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