A method for tuning a nuclear magnetic resonance (NMR) tool having an
operating frequency and equipped with an antenna, is disclosed
comprising: (a) transmitting a rf magnetic field to a sample under
investigation; (b) receiving an NMR signal from the sample within a
detection window; (c) determining mistuning of said antenna relative to
said operating frequency; (d) analyzing the received echo signal to
determine mistuning of the received signal from the operating frequency.
The mistuning of the received signals from the operating frequency may be
determined by analyzing any changes in phase of the echo along the echo
signal. The antenna tuning process may be automated by measuring
calibrated signal amplitudes at more than one frequency and identifying a
maximum amplitude. The system tuning may be maintained by repeating (a)
through-(d) while operating the tool and implementing a feedback loop.
