Compact microstrip coupled-line directional coupler realized in thick-film technology

This paper presents the design of a compact 11-dB coupled-line directional coupler operating at center frequency of 1.2 GHz, which features improved frequency characteristics. A compact size of the coupler has been obtained by utilization of high-permittivity dielectric substrate while high performance has been ensured by application of method for the design of quasi-ideal coupled-line sections. Moreover, the circuit has been realized on alumina ceramic (Al2O3) substrate using thick-film technology what allows for low-cost and easy integration with passive and active circuits into hybrid microwave integrated circuit (MIC). The proposed circuit has been electromagnetically verified, manufactured and measured. The obtained results proved the usefulness and performance of the presented circuit.