Automatic impedance matching of HF transmitter and receiver equipment in nuclear spin tomography system

摘要

The HF equipment is matched to an antenna (4) via a variable matching circuit (5) with a matching network (8) and two adjustable control elements (6,7). The reflection factor at the matching circuit input connected to the transmitter or receiver is measured with the antenna interacting with an investigation object. An electronic controller (12) computes and adjusts the control element parameters. The controller computer is associated with the matching network as a linear four gate device with the input and output and the two control element connections as the four gates. The computer determines the complex antenna reflection factors from the complex reflection factors at the matching circuit input for any control element parameter setting and determines the parameter setting to be selected for a complex reflection factor of at least approximately null at the matching circuit's input gate taking account of the antenna reflection factor. The control characteristic of each control element and the electrical interactions in the matching network are stored.