Thermo Researching of X-band Microwave Amplifier

 
Timoshenkov V.P., Khlybov A.I., Rodionov D.V., Efimov A.G., Chaplygin Yu.A. (MIET)
 
Abstract - Modern new generation radar systems use the active phased array antenna (APAA), which are modularly designed to reduce the weight and size characteristics and the ability to achieve complex tactical and technical system requirements. In this connection, the task of increasing the integration, multifunctionality and reliability of APAA units, which consists of a set of microwave modules, is becoming topical. The APAA module contains a transmission channel and a receive channel. To control the amplitude in the receiving and transmitting channels, attenuators (ATT) serve, and for control of the phase - multi-phase phase shifters (FV). To translate the serial control code into parallel, the code converters serve. [1-2]. APAA X-band modules include several functional units, in which the most intense from the point of view of the thermal regime is the output power amplifier [3]. Analysis of the parameters of amplifiers such as the power consumption and efficiency of GaAs amplifiers shows that, for example, at an efficiency of 30% and an output power of 10 W, the total power dissipation of the 20W dissipates on the amplifier itself. The main part of this power comes from the transistors of the output stage. In this regard, the transmitters of APAA modules and in particular the power amplifiers operate in a pulsed mode with a duty cycle usually not exceeding 50%. However, even in this case, for long duration of the power pulse, the output power of the signal decreases because of the local heating of the output stage transistors. Ultimately, the duration of the output pulse or its duty cycle affects the heating of the transistors of the amplifier stages, which in turn leads to degradation of the output power. The purpose of this work is to study the thermal conditions of the power amplifier for topological optimization of the crystal, to reduce the internal electrothermal feedback, to determine the need for using heat removal systems, and to minimize intercrystal thermal effects. As the object of the study, the X-band amplifier of the company TRANSCOM which placed on a multilayer printed circuit board (Rogers RO 4003), was used. The thermal mode of the microwave amplifier for the APAA X-band transmit-receive module was studied. The experimental results of measuring the temperature on a GaAs crystal of an amplifier obtained with the SC5700 IR camera and the results of computer simulation of heat distribution are presented. It is shown that the use of a duty cicle of more than 30%, with a pulse duration of 2.5 μs can lead to significant output stage transistorsoverheating. Recommendations for removing heat from the crystals of the amplifier are given . The results of the experiment are in good agreement with the results of computer simulation. Recommendations for optimization / selection of the pulse width and duty cycle for the amplifiers of the APAA X-band module are given.

Keywords - microwave, module of active phased array antenna, thermo simulation, power amplifier.

Исследование теплового режима СВЧ усилителей мощности X диапазона

 
Тимошенков В.П., Хлыбов А.И., Родионов Д.В., Ефимов А.Г., Чаплыгин Ю.А. (Национальный исследовательский университет «МИЭТ», г. Москва)
 
Аннотация - Проведено исследование теплового режима СВЧ усилителя для приемо-передающего модуля АФАР Х диапазона. Представлены экспериментальные результаты измерения температуры на кристалле GaAs усилителя, полученные с помощью ИК-камеры SC5700 и результаты компьютерного моделирования распределения тепла. Показано, что использование скважности более 30%, при длительности импульса 2,5 мкс может привести к значительному перегреву, транзисторов выходного каскада. Даны рекомендации по способу отвода тепла от кристаллы усилителя. Результаты эксперимента хорошо совпадают с результатами компьютерного моделирования. Даны рекомендации по оптимизации/выбору длительности импульса и скважности для усилителей модуля АФАР Х-диапазона.

Ключевые слова - СВЧ, приемо-передающий модуль АФАР, тепловое моделирование, усилитель мощности.