LOW-NOISE BAND-PASS BALANCED MICROWAVE AMPLIFIER Russian patent published in 2013 - IPC H03F1/32 

FIELD: radio engineering, communication.

SUBSTANCE: in the disclosed low-noise band-pass balanced microwave amplifier, having two single-stage transistor amplifiers connected between input and output cascade-connected three-decibel directional couplers, the outputs of the transistor amplifiers are connected to inputs of the output three-decibel directional coupler through transmission lines, connected in series with band-pass filters, which reflect energy beyond the pass band, wherein the phase incursion ϕ of each transmission line at a frequency lying in the region of the rise of the amplitude-frequency characteristic of input matching circuits of the transistor amplifiers is $$\varphi =\left[arctg\left(\frac{-j{X}_f}{jZ}\right)+arctg\left(\frac{-j{X}_T}{jZ}\right)\right].$$

EFFECT: improved intermodulation selectivity of radio receivers while maintaining high sensitivity.