Closed-Loop Control for Transmit Array Matching

Giorgos Katsikatsos¹, Klaas P. Pruessmann¹

A closed-loop controlled matching for Tx-arrays in ultra-high field has been implemented as an autonomous system to react to load changes in various stages of an MR experiment. Building blocks of the system are the L-matching networks, built from custom low-loss capacitors actuated by piezoelectric motors and controlled by an external computer. The feedback is provided by a network analyzer which triggers the re-matching procedure. The matching algorithm is based on previous knowledge about the matching circuit connected to the array and uses common objective functions to detect the best matching settings for arbitrary loads.