V.B. Bakeev, M.A. Minkin, E.G. Skorobogatov

Approaches to development of wideband active receiving antenna input circuits, ensuring a realization of a given sensitivity requirements were viewed. General functions of input matching-transforming circuit were analyzed. General requirements to amplifier-s noise characteristics and qualitative criterions of matching were formulated. Generalized equivalent circuit of active antenna-s chain in the form of cascade connection of passive and active four-terminal devices with inclusion of necessary noise generators was substantiated. General proportions for calculation of noise characteristics of elements and generalized equivalent circuit in a whole were obtained. Statement of the matching-transforming circuit synthesis problem as an optimization problem with appropriate criterions and additional constraints if necessary was substantiated. It was shown that there is a synthesis required: by signal-s maximum output power criterion under given constraints of acceptable noise level; by signal/(noise+interference) maximum criterion; by criterion of signal/noise relation maximum with acceptable output signal level (not less than given) ensured. Synthesis of matching-transforming circuit for matching a transmitter having certain (tabulated) output impedance with an input of a low-noise amplifier having certain parameters in a 250...850 MHz frequency band was viewed as an example. Preparatory synthesis of a circuit was implemented by method of real frequencies and final - by methods of parametrical optimization by signal-s input power maximum criterion with given constrains on acceptable noise level and power loss in elements (thus also a self-noise of a circuit) being taken into account.