Matching and decoupling networks for receive-only MRI arrays

Mutual inductive coupling between elements of an MRI detector array greatly complicates the process of impedance matching of the array. This problem is even more severe in flexible arrays, where coupling matrix will change with the shape of the array. To overcome this problem a low noise amplifier can be integrated in each element with a network providing simultaneous noise matching and power mismatching for decoupling. This work describes the design of such impedance transforming networks that allow minimizing the influence of the inductive coupling and, at the same time, to ensure minimum noise Figure of the connected low noise preamplifier. Different circuit topologies are analyzed. Their performance with regard to bandwidth and noise Figure are compared. The networks ensure minimum noise Figure and decoupling level to about 28 dB. The presented analysis would be useful for MRI and antenna array designs where element coupling presents a practical problem.