Miniaturization of Wideband Loose Coupled (10dB) BLC Using Dual Transmission Lines

This paper presents a design of miniaturized wideband branch line coupler (BLC) with loose coupling of 10dB using dual transmission lines as a feed network. The dual transmission line technique provides a size reduction of 27%. The size of the coupler is further reduced by folding the high impedance section (shunt quarter wavelength) of the coupler, as a result of which the overall size reduction of around 44% with FBW of 58.3% is achieved for the coupled output of 10±0.5dB. The proposed BLC is design on an Arlon substrate of dielectric constant (ε
_r
) = 3.5, thickness (h) =0.5 mm and loss tangent of 0.002.