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Development of Compact and Flexible Quadrature Hybrid Coupler Using Coaxial Cable with Capacitive Loading for 1.5t Indigenous MRI System

By Rohit Apurva, Niraj Yadav, Tapas Bhuiya, and Rajesh Harsh
Progress In Electromagnetics Research Letters, Vol. 93, 143-151, 2020


Quadrature feeding is an 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 63.87MHz 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 (S41) of around 19 dB and a 900phase difference between coupled and the through ports. Both structures provide return loss S11 > -15 dB and coupling at output ports S21, S31 around 3 dB.


Rohit Apurva, Niraj Yadav, Tapas Bhuiya, and Rajesh Harsh, "Development of Compact and Flexible Quadrature Hybrid Coupler Using Coaxial Cable with Capacitive Loading for 1.5t Indigenous MRI System," Progress In Electromagnetics Research Letters, Vol. 93, 143-151, 2020.


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