Investigations of broadband multilayered coupled line couplers

In this paper two modified structures of multi- layered broadband 3 dB/´90deg coupled line couplers are proposed. The first structure is a broadside coupled stripline coupler with corrugated ground plane. The second investigated structure is a modified micro strip-slotline coupler. In comparison to basic configurations of couplers the improvement of operation bandwidth for proposed structures is achieved. The simulated results are experimentally verified and a good agreement is obtained. For the first structure the measured operation band is from 1.5 to 4.5 GHz with coupling and transmission equal 3plusmn1 dB and isolation and reflection losses better than 20 dB. For the second structure in operation band from 2.4 to 6.4 GHz the measured transmission and coupling are 3plusmn0.8 dB with isolation and reflection losses better than 20 dB.