__Keywords:__active phased antenna array receiving and transmitting module power amplifier thermal state

V.А. Kolomejcev, А.V. Ezopov, A.E. Semenov

With the advent of on-board APAA X – band has acquired a special urgency the task of ensuring the thermal regime of the active elements is due to the fact that a high packing density with high unit power and limited resources as a power plane and the overall results in the fact that radioactive elements operate in modes close to limit. Therefore, when creating a transceiver module (RTM), APAA must provide constructive solutions to most effectively take heat away from the active element and increase the level of radiated power, and, consequently, the target detection range. To find ways of optimizing the design of a mathematical model of the processes of heating, heat transfer and heat transfer of thermal power from the active elements in the cooling medium.
In formulating the mathematical model of thermal processes RTM was used, and the orthogonality principle of superposition. This provision allows for the calculation of the thermal field of such a complex system, which is the RTM, using a simple mathematical model, which is a two-layer rectangular plate with a surface heat source at different positions of the source in the volume of the plate. The number of possible locations of the heat source on the outer surface of the plate equal to the number of active elements, and the position and dimensions of the heat source corresponds to the location of the element.
The article gives the solution inside the boundary value problem of heat conduction for a two-layer rectangular plate with a surface heat source, carried out on the basis of Fourier transforms on the basis of orthonormal functions. The presented solution allows us to investigate the thermal field RTM APAA, taking into account the influence of the design features of the temperature of the microwave power amplifier.
Analyzing the calculations of thermal fields at different base materials for different cooling regimes – from natural convection to the air to force water cooling, you can see that from some of the values of the coefficient of heat transfer by convection and radiation, a far greater contribution to reducing the maximum temperature of the active element makes application of high heat reason than a further increase in the coefficient of heat transfer by convection and radiation.
Thus, this study shows that the most promising way of reducing the heating temperature of the active element and, consequently, increase the maximum achievable radiated microwave power is to intensify the process of removing heat from the active element in the cooling medium by increasing the thermal conductivity of the base. By increasing the thermal conductivity of the base reduced the unevenness of the thermal field RTM, which reduces the temperature of the active element, first, by reducing the average temperature of the module due to the intensification of heat transfer from the outer surface of the module, as in the cooling process make use of the parts of the module, which had remained cold and in the cooling process is not involved, and secondly, by reducing the maximum temperature due to more uniform temperature distribution inside the module.

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