Size miniaturization of 3 dB branch line coupler by using open stubs

In this paper a miniaturized 3 dB branch line coupler (BLC) is proposed. The miniaturization is done by adding open stub to the series and parallel transmission line of the conventional 3 dB coupler such that the proposed T-shaped structure is equivalent to the conventional 3 dB branch line coupler. The equivalent circuit is obtained by comparing the ABCD parameters of the T-shaped and conventional transmission line. As the area is less there is a possibility of coupling between the stubs of series and parallel transmission line. Based on the flexibility of the designer the structure is designed in a way to minimal the effect of coupling between the stubs of the series and parallel transmission lines. The proposed structure has reduced size than the conventional coupler and has fair response at 2.5 GHz.