A.O. Manichev - Ph.D. (Eng.), Head of Department, JSC «Almaz-Antey». E-mail: alex_manichev@inbox.ru A.N. Tyuvaev - Leading Engineer, JSC «Almaz-Antey». E-mail: okean87@mail.ru

The method of recurrence relations is widely used in the design of serial feed networks, which are often employed in highly effective phased array antennas (PAAs). It takes into account the mutual coupling between the channels in the main transmission line of the network at the first mode. However, this method has the following disadvantages. Firstly, it assumes the usage of the equivalent circuits of the coupling elements and therefore, as a rule, does not provide a high accuracy due to the difficulties in determining their parameters. Secondly, the calculation is performed only for regular serial feeds having the same inter-channel distance. Moreover, the load at the end of the main line of the network is supposed to be ideal. In order to eliminate the abovementioned disadvantages, a modification of the recurrence relations method was proposed. It-s based on the decomposition of the network into individual elements and the usage of the scattering matrices of the elements. The matrices can be either calculated through the use of electromagnetic simulation packages, or measured experimentally. The design of a feed network is described in detail at the example of three-port microwave devices (T-functions). Moreover, the synthesis of a serial feed that implements a specified amplitude distribution (this is one of the most important tasks in the design of a PAA feed) is considered. In the paper the synthesis is performed on the basis of the proposed modification of the recurrence relations method. The method was implemented in a software program intended for calculation of the characteristics and parameters of a serial feed network and their visualization. In addition to the basic calculations, the application provides a means for investigation of the charac-teristics of the feed network, which can-t be measured directly. For example, it is possible to determine the amplitudes of the reflected wave along the main transmission line of the network and detect the regions with a high reflected wave level. These regions are undesirable since they reduce the power-handling capacity of the feed network and increase the sensitivity of the amplitude-phase distribution at the outputs of the feed network to the destabilizing influence of the environment (e.g. temperature change). Furthermore, in addition to the method of recurrence relations, the application program implements the energetic method of the serial feeds calculation. The method makes it possible to optimize the portion of the power absorbed in the load at the end of the main transmission line (this operation is necessary at the preliminary stage of the serial feed design via modified recurrence relations me-thod). The proposed modification of the method of recurrence relations and the developed software significantly improve the accuracy of calculation of the serial feed networks parameters (including feeds with irregular element placement) and provides additional data important for practical realization.

 

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