Extension of the design of the optimum noise source reflection coefficient to lossy series feedback impedances

This paper presents an extension to lossy series feedback impedances of an analytical procedure in order to design the magnitude of the optimum noise source reflection coefficient Γ_Sopt for 2-port networks. Some examples with microwave packaged devices are presented. The minimum in |Γ_Sopt| is discussed by taking the loss of series feedback into account. Analytical design for |Γ_Sopt| with a lossy series feedback impedance is still possible provided that the quality factor Q of the feedback is large enough. Q also affects the minimum noise figure F_min of the feedback network; however, a decrease in F_min relatively to the value of the active device in use, can still be achieved. The results improve the understanding of the feedback applied to microwave devices and they can be used to look into the noise performance of any type of microwave devices