Pulsed resonance spectrometer system employing improved radio frequency pulse turn-off method and apparatus

Claim 2

A resonance spectrometer system comprising a high Q resonant circuit for applying a radio frequency magnetic field to a sample material coupled to said resonant circuit to produce resonance therein, pulse transmitter means coupled to said resonant circuit for providing a radio frequency signal to said resonant circuit to produce said radio frequency magnetic field, receiver means coupled to said resonant circuit for detecting the free induction decay signal induced in said resonant circuit from said sample after termination of said transmitter pulse, said receiver means being coupled to said resonant circuit during both the application of said radio frequency magnetic field to said sample and the detection of said free induction decay signal, means coupled to said transmitter means for changing the phaSe of said radio frequency signal to said resonant circuit, and means for terminating said radio frequency transmitter signal after said phase change and at that point in time after said phase reversal when the voltage across said high Q resonant circuit is near its zero crossing, to thereby substantially reduce ringing signals in said receiver means due to energy storage in said high Q resonant circuit after transmitter pulse termination.

Claim 3

A resonance spectrometer system as claimed in claim 1 wherein said resonance is the magnetic resonance of the sample.

Claim 4

A resonance spectrometer system as claimed in claim 2 wherein said resonant circuit comprises a radio frequency coil and said resonance is the magnetic resonance of nuclei in the sample.

Claim 5

A resonance spectrometer system as claimed in claim 2 wherein said resonant circuit comprises a microwave resonator and said resonance is electron paramagnetic resonance.

Claim 6

A resonance spectrometer system as claimed in claim 1 wherein said means for changing the phase of the radio frequency signal reverses the phase substantially 180* and said means for terminating said signal operates to terminate the signal in the region of the next zero crossing of the radio frequency voltage across said resonant circuit.

Claim 7

A resonance spectrometer system as claimed in claim 5 wherein said means for terminating said radio frequency transmitter signal comprises a timer circuit operative a selected time after said phase reversal.

Claim 8

A resonance spectrometer system as claimed in claim 5 wherein said means for terminating said radio frequency transmitter signal comprises means for measuring the voltage of said radio frequency across said resonant circuit after said phase reversal.

Claim 9

A resonance spectrometer system as claimed in claim 7 wherein said last means comprises a means for sensing the radio frequency voltage across said resonant circuit, and means for comparing said sensed voltage with a reference voltage.

Claim 10

A resonance spectrometer system as claimed in claim 1 wherein said transmitter means includes a radio frequency source and a phase shifter circuit coupled to said source for providing a first radio frequency signal and a second radio frequency signal shifted 180* from said first signal, said means for changing said phase of said radio frequency signal comprising means for selecting between said first and second radio frequency signals.

Claim 11

A magnetic resonance spectrometer system comprising a high Q resonant circuit for applying a radio frequency magnetic field to a sample material coupled to said resonant circuit to produce magnetic resonance therein, pulse transmitter means coupled to said resonant circuit for providing a radio frequency voltage to said resonant circuit to produce said radio frequency magnetic field, receiver means coupled to said resonant circuit for detecting the free induction decay signal induced in said resonant circuit from said sample after termination of said transmitter pulse, said receiver means being coupled to said resonant circuit during both the application of said radio frequency magnetic field to said sample and the detection of said free induction decay signal, means coupled to said transmitter means for reversing the phase of said radio frequency voltage to said resonant circuit substantially 180*, and means for terminating the pulse of radio frequency voltage to said resonant circuit when the radio frequency voltage across said resonant circuit is at the zero crossing region after said phase reversal to thereby substantially reduce ringing signals in said receiver means due to energy storage in said high Q resonant circuit after transmitter pulse termination.

Claim 12

A magnetic resonance spectrometer system comprising a high Q resonant circuit for applying a radio frequency magnetic field to a sample material coupled to said resonant circuit to produce magnetic resonance therein, pulse transmitter means coupled to said resonant circuit for providing a radio frequency voltage to said resonant circuit to produce said radio frequency magnetic field, receiver means coupled to said resonant circuit for detecting the free induction decay signal induced in said resonant circuit from said sample after termination of said transmitter pulse, said receiver means being coupled to said resonant circuit during both the application of said radio frequency magnetic field to said sample and the detection of said free induction decay signal, means coupled to said transmitter means for reversing the phase of said radio frequency voltage to said resonant circuit substantially 180*, and means for terminating the pulse of radio frequency voltage to said resonant circuit when the radio frequency voltage across said resonant circuit is at the zero crossing region after said phase reversal to thereby substantially reduce ringing signals in said receiver means due to energy storage in said high Q resonant circuit after transmitter pulse termination.

Claim 15

The method as claimed in claim 11 wherein said step of terminating said radio frequency pulse comprises the step of measuring a preselected time interval after said phase change.

Claim 16

The method as claimed in claim 11 wherein said step of terminating said radio frequency pulse comprises the step of measuring the voltage across said resonant circuit to determine the zero cross-over time.