Quadrature feeding is essential in magnetic resonance imaging radio frequency (MRI-RF) coils, to improve the homogeneity of the magnetic field of surface coil, the signal to noise ratio (SNR) of the image by a factor of √ 2, and to create a circularly polarized magnetic field inside the volume coil. The quadrature feeding is incorporated, using hybrid coupler. However, at 63.87 MHz the Larmor frequency of hydrogen proton, corresponding to 1.5 Tesla, the size of the hybrid coupler and other microwave circuits become large. So, to minimize its physical size, a coaxial cable transmission line with lumped capacitive loading has been proposed. The size of the proposed hybrid coupler is reduced by 68%, as compared to the conventional hybrid coupler. The proposed device is then fabricated as a both rigid and flexible structure, which provides isolation (S 41) of around 19 dB and a 90 • phase difference between coupled and the through ports. Both structures provide return loss S 11 > −15 dB and coupling at output ports S 21 , S 31 around 3 dB.

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