Miniaturized phase shifter using capacitor-loaded transmission line for MRI RF shimming

The radiofrequency (RF) shimming circuit consisting of power splitters and phase shifters is a well-recognized way to solve the inhomogeneity of the RF field in ultrahigh field MRI. However, phase shifters made of standard transmission lines are too large to be suitable for the RF shimming circuit. In this work, we propose miniaturized phase shifters based on the capacitor-loaded transmission line (CLTL), in which the physical size could be well reduced without sacrificing RF performance. A complete theoretical analysis was provided, and the proposed design was validated by electromagnetic simulation and bench test. The fabricated phase shifters have miniaturized sizes and exhibit low insertion loss.