Miniaturized coupled-line directional coupler designed with the use of photoimageable Thick-Film technology

A quarterwave-long coupled-line single-section directional coupler has been developed using the combination of Phtoimageable Thick-Film technology and Laminate technology in an asymmetric dielectric structure. In order to obtain a significant miniaturization of the directional coupler, a high permittivity thin dielectric film between coupled lines has been used. Such an approach allows achieving compact size of the designed circuit, especially at the lower frequency ranges. The presented approach has been verified by the electromagnetic simulations and measurements of a 3-dB single-section coupled-line directional coupler operating at the center frequency f₀ = 1 GHz.