Patent ID: 7358737

Claim:
A method of effecting magnetic resonance experiments comprising: providing a location for a sample mounted in a static magnetic field, providing adjacent to the location a transmit coil for generating a required radio-frequency magnetic field, said field being created by the coil carrying radio-frequency current of required frequency, amplitude and phase, said requirements being essentially independent of changes in the electrical characteristics and electrical and physical environment of the coil; providing a transmitter for creating a radio-frequency signal of said required frequency that produces in the transmit coil a radio-frequency current that generates a radio-frequency magnetic field, the transmitter including a radio-frequency amplifier for setting its said signal to a desired average size, and a modulator that enables the said radio-frequency signal to be set in amplitude and phase by a known value of signal input to the modulator that serves as a measure of the said signal's amplitude and phase; providing a current detector for supplying values of the amplitude and phase of the actual radio-frequency current in the said transmit coil; providing adjacent to the location of the sample a receive coil for receiving a radio-frequency signal from the sample generated in response to the transmitted radio frequency magnetic field and the static magnetic field; providing a receiver for receiving and presenting for analysis the received radio-frequency signal from the receive coil, said receiver including an amplifier for amplifying its radio frequency-signal; wherein the transmit coil is arranged to be energised by the transmitter with a transmit radio-frequency signal of the required frequency and of which there is a known measure of amplitude and phase; wherein the transmit coil is arranged to be connected to a current detector which provides a measure of the amplitude and phase of current in the transmit coil; wherein the method includes: measuring the current in the transmit coil with said current detector to provide values of the amplitude and phase of the current; comparing in a comparison step the transmitter's known value of signal input, that serves as a measure of required amplitude and phase, with the values of the amplitude and phase of the measured current, to determine a difference therebetween; using the said difference to reset the amplitude and phase of the transmit radio-frequency signal input such that the amplitude and phase of the current in the coil are to high accuracy equal to the required value.