УДК 621.354.76  

Электродинамический расчет транзисторных СВЧ усилителей

 

А. А. Курушин

Национальный исследовательский университет МЭИ, 111250, г Москва, Красноказарменная, 14

 

Статья поступила в редакцию 23 сентября 2017 г.

 

Аннотация. Для моделирования транзисторных СВЧ усилителей  предлагается использовать электродинамический метод расчета, транзистор представляется в виде восьмиполюсника (четырехпортовой схемы). Это позволяет выполнить проектирование с учетом потерь на излучение и с учетом   взаимной связи между отдельными фрагментами согласующей структуры произвольной формы.

Ключевые слова: транзисторный СВЧ усилитель,  устойчивость,  согласование,  электродинамический расчет, FEKO.

Abstract.     For modeling of microwave transistor amplifiers we propose to use the electrodynamic method, where the transistor is represented by four-port scheme.            Design of Microwave Transistor Amplifiers (MTA) in last decades was based on matrix calculations and methods of the theory of circuits which was based on the theory of Kurokawa. According to this theory the stability coefficient and optimum reflection coefficients are defined through scattering matrix of the transistor.            The paper contains study of MTA using the Method of Moments. In the calculation in FEKO transistor is considered with 4 ports. A transistor created in Russia was used in MTA. The model of the transistor, given in table of S-parameters, is included in the structure of the microwave amplifier. This model, implemented as a four port structure, is called Non-radiating Networks and it is connected to the ports specified in the all structure. We considered two approaches to the modeling of microwave structures and have chosen the use of FEKO, in which the structure is divided into the radiating and Non-radiating Networks (transistor). Radiating structure with arbitrary shape retains all of its electrodynamic features. In this case, the relationship between the input and output matching structure is taken into account automatically, and it is possible to calculate the characteristics of the near and far fields of the structure that includes active elements. By using the four-port representation of a transistor, it is possible to perform the feedback in MTA as part of complex matching structure. Modeling and optimization of the microwave devices show that the inclusion of a microwave transistor by the schemes of Common Emitter, Common Collector and Common Base in microwave amplifier makes quasi-equivalence. Calculation study shows that the effect of the electrodynamic connection between the input and output matching structure is manifested not only by gain reduction but made Gain=0 on 32 GHz due to the resonance properties of the electrodynamic structure. Electrodynamic approach allows us to perform and optimize MTA with arbitrary matching structures.

Each of the elements, including shapes superimposed on each other, as well as with an arbitrary configuration, can be parameterized, which leads to a matching structure of a complex, unpredictable shape. Modeling MTA with the help of electrodynamic method allows us to consider MTA as the active antenna. We show how a current in input, output and feed-back matching structure contributes to the far-field. Directivity, efficiency and loss characteristics are also affecting gain and stability of MTA. Comparison of calculated frequency response shows that using feedback makes possible to receive the same features as in the case of tuning input and output matching circuits. It is seen that in the region of 25 – 35 GHz gain of MTA has the same values.  Synthesis of MTA by using feedback or by using input and output matching circuit leads to the same result. It can be shown that the maximum gain is achieved by any method and takes the same value at the selected frequency. It should be noted that at low frequencies it is considered that the scheme with Common Collector is the same pattern with Common Emitter, but with 100% feedback. So we believe that optimization of MTA on very high frequencies with Common Collector, Common Emitter and Common Base leads to the same result. It should also be noted that the polarization begins to play an important role in the construction of the microwave amplifier, which affects the gain and stability.

With the introduction of modern microwave CAD  in design process, the theory of Kurokawa  is transferred to the new electrodynamic level. Electrodynamic design of microwave structures, in which active elements are included, opens up new possibilities both for improving the performance of traditional structures and for creating such unique structures as waveguide multi-transistor microwave amplifiers. (Kurushin A., Podkovyrin S. Synthesis of Microwave Structure. IEEE Microwave Conference, Taipei, 3-6 Dec. 2001, DOI: 10.1109/APMC.2001.985650).

Key Words: microwave transistor amplifier; stability; matching; electrodynamic calculation; FEKO.

Ссылка на статью:

А. А. Курушин. Электродинамический расчет транзисторных СВЧ усилителей. Журнал радиоэлектроники [электронный журнал]. 2017. №11. Режим доступа: http://jre.cplire.ru/jre/nov17/15/text.pdf