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.