A New Decoupling Method for Coil Elements on a Cylinder Surface

Introduction: Decoupling of multi-element coil is becoming increasingly important due to the parallel transmitting application. The conventional method to decouple coil elements distributed in the azimuthal direction is to use the Butler matrix to form the Eigen modes of the multi-element set-up [1]. Because the Eigen modes of the birdcage coil are orthogonal to each other, the elements after Butler matrix are decoupled. Although this method is theoretically applicable to any symmetrically arranged coil elements with arbitrary number of coil elements on the cylinder surface, the implementation of the Butler matrix is very expensive and requires a lot of efforts. Another state-of-the-art method is to use inductive coupled transformer to remove the coupling between arbitrary coil elements. This method has but the drawback of high power loss due to the lossy transformer. Capacitive decoupling [2] is easy to implement and capacitors with high Q-value are easy available. But because conventional capacitive decoupling requires galvanic connect coil elements together, the capacitive decoupling can be only used to a limited number of elements. In this paper we present a novel method to achieve decoupling between any coil elements up to a total element number of 6 or 8 without using inductance.