Abstract :
This article designs a dual transformer, which can be coupled or tuned to two arbitrary frequencies. We formulate this problem as a minimization problem of the Reflection Coefficient Γ_in, which allows us to find the impedances Z_1 and Z_2=Z_o R_l/Z_1 of the sections of the transmission line. We use Convex Optimization and the Dichotomous Search algorithm that allows us to find the parameters of the transmission lines. We show several results, and we include the case for operating frequencies of 700MHz (Band 7 - LTE) and 1900MHz (Band 2 -LTE).