Design of an inductively decoupled microstrip array at 9.4 T.

By independent control of the phases and amplitudes of its elements, the microstrip transmission-line array can mitigate sample-induced RF non-uniformities, and has been widely used as the transceiver in parallel imaging applications. One major challenge in implementing the microstrip array is the reduction of mutual coupling among individual elements. The low-input impedance preamplifier is commonly used for the decoupling purpose. However, it is impractical in the transceiver array design. Although interconnecting capacitors can be utilized to reduce the mutual coupling, they only efficiently work for the neighbor elements. In addition, this approach is impractical at fields higher than 300 MHz, in which the required decoupling capacitance is commonly less than 0.5 pF. We propose a novel decoupling approach by using decoupling inductors in this study. Due to the fact that the decoupling inductance is independent of the resonant frequency, the microstrip arrays can be well decoupled at ultra-high fields. To verify the proposed approach, an eight-channel microstrip array is fabricated and tested at 9.4 T. For this prototype, couplings between elements are significantly reduced by using the interconnecting inductors. The phantom experiment shows that the inductively decoupled microstrip array has good parallel imaging performance.