Miniaturization and bandwidth enhancement of a loose coupler by DGS

A 10 dB branch line coupler with a dumbbell shaped defected ground structure (DGS) is proposed in this paper. The 150 ohm transmission line of the proposed BLC above the substrate is of much small size than the conventional due to the DGS in the ground layer. The equivalent LC circuit of the proposed 150 ohm line is obtained. The proposed 150 ohm transmission line is now used in the 10 dB branch line coupler. The proposed 10 dB coupler is now of reduced size and from the simulation result it's seen that flatness of the response increases, in turn increasing the bandwidth.