V.F. Mikhailov – Dr.Sc.(Eng.), Professor, Saint-Petersburg State University of Aerospace Instrumentation E-mail: vmikhailov@pochta.tvoe.tv

In present work the radiation from a circular waveguide for H11 is considered. The waveguide is covered by a flat homogeneous heat shield. This design of the radiator corresponds to the onboard antenna of the returned spaceships. To solve mentioned problem, we used the concept of the angular spectrum of plane waves. In the first approximation, it is considered that the field propagation in the radiator’saperture does not depend on the electrical and geometrical parameters of the dielectric heat shield. We obtained the relations that describe the radiation pattern of a circular waveguide with dielectric heat protection and a different type of heat loss, which take into account the electrical parameters of the heat shield and its thickness.
The problem of obtaining an analytical description the characteristics of the radiation of a circular waveguide closed by a flat homogeneous dielectric plate is solved. The characteristics of radiation are: radiation field; conductivity of aperture’s radiation; fields of surface waves, leaky waves, lateral waves, and energy characteristics. As far as in this formulation we had to consider the resonance region, it is necessary to get an accurate solution of the Maxwell’s equations. Among the known analytical methods we had an opportunity to use the method of integral transformations and the method of eigenfunctions. Both methods are used in this work. Also we made an assumption that the electrical parameters of the dielectric plate (thermal protection) and the geometric dimensions do not depend on time, which practically corresponds to real situations. We obtained the relations that describe the radiation pattern of a circular waveguide with dielectric heat protection, which take into account the electrical parameters of the heat shield and its thickness. We also received expressions for the fields of the lateral, surface and leaky waves, which made it possible to calculate the power emitted by these fields. As a result we could estimate the electrical parameters of a circular waveguide.
We obtained relations for separating the singular points of the integrands into poles corresponding to surface, leaky, and lateral waves. The above waves can have a certain effect on the radiation pattern. To determine this conclusion, analytical relations were obtained for determining the poles of the integrands, which completely describe the surface, leaky, and lateral waves.
The obtained expressions for the conductivity of the aperture of a circular waveguide closed by a dielectric plate made enable to determine the reflection of the radiated power superinduce by this plate. Unfortunately, all the analytical relations we obtained were gigantic and their use becomes possible only in the case of numerical integration. Numerical calculations were carried out for some of the relations. The results showed that the power of the lateral waves is equal to zero. They therefore follows that the radiation field of surface and leaky waves is absent, i.e. they don’t influence on the radiation pattern. Further researches in this area should be devoted predominantly to develop computer programs for counting the basic radiation characteristics.

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