Generating a signal

Patent metadata

Field	Value
Publication number	US-9760337-B2
Application number	US-201414272879-A
Country	US
Kind code	B2
Filing date	May 8, 2014
Priority date	May 8, 2013
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A method for generating a signal for a transmission antenna in a magnetic resonance imaging system includes generating a real part and an imaginary part of a baseband signal, generating a real part and an imaginary part of variations in frequency and in phase, and performing a complex multiplication of the baseband signal with the variations in frequency and in phase and a radiofrequency carrier signal for modulation. The method also includes modifying the modulated signal, and may include establishing a characteristic angle for a phase shift of the modified signal, and correcting the modulation based on the established angle in a closed-loop control.

First claim

The invention claimed is:

1. A method for generating a signal for a transmission antenna in a magnetic resonance imaging system, the method comprising:
generating a real and imaginary part of a baseband signal;
generating a real and imaginary part of variations in frequency and in phase;
performing a complex multiplication of the baseband signal with the variations in frequency and in phase and a radiofrequency carrier signal for modulation;
modifying the modulated signal;
establishing an angle characteristic of a phase shift of the modified signal; and
correcting the modulation based on the established angle in a closed-loop control,
wherein the correcting comprises adding to an output signal of a phase accumulator that is used in the generation of a real and imaginary part of the variations in frequency and in phase.

2. The method of claim 1 , wherein a difference between a phase angle of the demodulated modified signal and a phase angle of the baseband signal is used when establishing the characteristic angle.

3. The method of claim 2 , wherein a phase angle of a manipulated variable of the closed-loop control is used when establishing the characteristic angle.

4. The method of claim 3 , wherein a difference between a phase angle of the manipulated variable and a phase angle of the baseband signal is used when establishing the characteristic angle.

5. The method of claim 2 , further comprising compensating for time retardation of elements of the closed-loop control.

6. The method of claim 5 , wherein the phase accumulator is a first phase accumulator, and
wherein values are accumulated from the established angle using a second phase accumulator when correcting the modulation.

7. The method of claim 6 , further comprising determining the values accumulated in the second phase accumulator based on a table with assignments between angle intervals and values.

8. The method of claim 2 , wherein establishing the characteristic angle comprises determining the characteristic angle based on a table with assignments between real and imaginary part intervals and angles.

9. The method of claim 1 , wherein a phase angle of a manipulated variable of the closed-loop control is used when establishing the characteristic angle.

10. The method of claim 9 , wherein a difference between a phase angle of the manipulated variable and a phase angle of the baseband signal is used when establishing the characteristic angle.

11. The method of claim 1 , further comprising compensating for time retardation of elements of the closed-loop control.

12. The method of claim 1 , wherein the phase accumulator is a first phase accumulator, and
wherein values are accumulated from the established angle using a second phase accumulator when correcting the modulation.

13. The method of claim 12 , further comprising determining the values accumulated in the second phase accumulator based on a table with assignments between angle intervals and values.

14. The method of claim 12 , wherein modifying the modulated signal comprises modifying the modulated signal using a circulator, and wherein the method further comprises determining input values for the second phase accumulator based on a temperature of the circulator during a time period between two signal pulses of the signal.

15. The method of claim 14 , wherein the residual established angle is fed to the second phase accumulator as an input value at the end of a signal pulse.

16. The method of claim 1 , wherein establishing the characteristic angle comprises determining the characteristic angle based on a table with assignments between real and imaginary part intervals and angles.

17. A signal generation module for a magnetic resonance imaging system, the signal generation module being configured to generate signals, the signal generation module comprising:
a controller configured to:
generate a real and imaginary part of a baseband signal;
generate a real and imaginary part of variations in frequency and in phase;
perform a complex multiplication of the baseband signal with the variations in frequency and in phase and a radiofrequency carrier signal for modulation;
modify the modulated signal;
establish an angle characteristic of a phase shift of the modified signal; and
correct the modulation based on the established angle,

wherein the correction comprises addition to an output signal of a phase accumulator that is used in the generation of a real and imaginary part of the variations in frequency and in phase.

18. A magnetic resonance imaging system comprising:
a signal generation module configured to generate signals, the signal generation module comprising:
a controller configured to:
generate a real and imaginary part of a baseband signal;
generate a real and imaginary part of variations in frequency and in phase;
perform a complex multiplication of the baseband signal with the variations in frequency and in phase and a radiofrequency carrier signal for modulation;
modify the modulated signal;
establish an angle characteristic of a phase shift of the modified signal; and
correct the modulation based on the established angle,

wherein the correction comprises addition to an output signal of a phase accumulator that is used in the generation of a real and imaginary part of the variations in frequency and in phase.

Assignees

• Demharter Nikolaus
• Siemens Ag

Inventors

• Demharter Nikolaus

Classifications

• G01R33/3607 Primary

  RF waveform generators, e.g. frequency generators, amplitude-, frequency- or phase modulators or shifters, pulse programmers, digital to analog converters for the RF signal, means for filtering or attenuating of the RF signal · CPC title

• A61B5/055

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• G06F5/01 Primary

  for shifting, e.g. justifying, scaling, normalising {(digital stores in which the information is moved stepwise, e.g. shift-registers G11C19/00; digital stores in which the information circulates G11C21/00)} · CPC title