Digital Q-Meter for continuous-wave NMR
AssigneeJefferson Science Associates, LLC
InventorsJames Maxwell, Hai Dong, Christopher Keith, Chris Cuevas
Life of this patent
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Abstract
A method to perform continuous-wave NMR measurements of nuclear magnetization at high magnetic fields, above 2.5 T, without analog down-mixing is described. An FPGA controls a digital clock pulse which is used to stimulate a resonant circuit and provide a reference signal. An algorithm determines the real portion of a resonant circuit signal near the Larmor frequency of the species of interest using only two measurements of the waveform per cycle. The FPGA automatically alters a variable capacitance to tune the resonant circuit to the Larmor frequency.
Claims14
A method of digitally acquiring continuous-wave NMR measurements above 5 MHz and up to a desired sampling frequency comprising an algorithm to produce real and imaginary components of a signal from two measurements each of the signal and a reference waveform per cycle, the two measurements being 90 degrees separated in time.
A method of digitally acquiring continuous-wave NMR measurements above 5 MHz and up to a desired sampling frequency wherein the NMR measurements are acquired using a field programmable gate array (FPGA) comprising the following steps:
- a) for the first point of the frequency sweep, reading reference samples x1, y1 and signal samples x2, y2 in each ADC, and averaging many points to reduce noise;
- b) determining amplitude and phase of reference and signal;
- c) calculating the total signal component and real component;
- d) tuning the capacitance of the LCR circuit to the center, Larmor frequency;
- and
- e) tuning the delay so that the reference and signal are in phase;
- and obtaining Q-curves.
Dependencies are inferred from the claim text.