Multisection 3-dB Ultra-Broadband Directional Coupler Composed of Coupled-Line Sections Designed in PCB and MMIC Technologies

In this paper, we present a new 3-dB ultra-broadband directional coupler with bandwidth exceeding one frequency decade. The proposed topology is composed of three coupled-line sections and two transmission lines having unequal lengths. In comparison to the known solutions, the proposed approach requires weaker coupling of coupled-line sections which makes it easier to implement in technologies where the achievement of a strong coupling is not possible due to physical constrains. The ultra-broadband directional coupler has been designed in PCB and monolithic technologies as components operating at 1 GHz and 20 GHz center frequency, respectively. The obtained measurements and electromagnetic simulations feature good electrical properties of the developed designs and confirm applicability of the proposed concept.