Circuit arrangement for the driving electronics of a magnetic resonance system
A circuit arrangement for driving a transmission coil arrangement with at least two individual transmission coils of a magnetic resonance system for supplying a radiofrequency signal for producing alternating electromagnetic fields over at least two channels, with in each case a digital section and an analog section, is provided. In the digital section, in an envelope generator, base frequency signals that respectively generate an envelope are provided. The circuit arrangement also includes an intermediate frequency oscillator that generates a common intermediate frequency, a frequency mixer per channel for mixing the common intermediate frequency into the base frequency signals, and in the analog sections of the channels, respectively, second frequency mixers that mix a common radiofrequency signal into each base frequency signal. The envelope is transmitted, with the mixed-in intermediate frequency signal, and the total signal thus obtained is respectively conducted to an individual transmission coil via a respective amplifier.
1. A magnetic resonance system for producing magnetic resonance images from at least one partial volume of an examination object, the magnetic resonance system comprising:
an arrangement of magnet systems operable to produce a homogeneous main magnetic field and additional gradient fields for spatial coding;
at least one transmission coil system comprising at least two individual transmission coils operable to produce alternating electromagnetic fields in order to induce a magnetic resonance signal in a prescribed partial volume of the examination object;
at least one receiver coil operable to measure the magnetic resonance signals emitted by the examination object; and
a computer system comprising control electronics including a memory for storing computer programs that control the magnetic resonance system in operation and evaluate the measured magnetic resonance signals,
wherein the control electronics comprise at least two separately drivable channels, and the at least two separately drivable channels have an individual signal profile that results from first mixing a base frequency for defining an envelope and an intermediate frequency for determining location, and then mixing the base frequency and mixed-in intermediate frequency with a radiofrequency for deflecting the magnetization, wherein a common intermediate frequency oscillator is present across channels for generating the intermediate frequency.
2. The magnetic resonance system of claim 1 , wherein the at least two separately drivable channels respectively have a first frequency mixer for initially mixing the base frequency and the intermediate frequency.
3. The magnetic resonance system of claim 1 , wherein the at least two separately drivable channels have a dedicated second frequency mixer per channel for further mixing in the radiofrequency.
4. The magnetic resonance system of claim 1 , wherein at least one frequency mixer of the first frequency mixers and the second frequency mixers is configured as a digital frequency mixer.
5. The magnetic resonance system of claim 1 , wherein at least one frequency mixer of the first frequency mixers and the second frequency mixers is configured as an analog frequency mixer.
6. The magnetic resonance system of claim 1 , wherein at least one frequency mixer of the first frequency mixers and the second frequency mixers is configured as a field-programmable gate array (FPGA).
7. The magnetic resonance system of claim 1 , wherein at least one frequency mixer of the first frequency mixers and the second frequency mixers is configured as an application-specific integrated circuit (ASIC).
8. The magnetic resonance system of claim 1 , wherein a digital-to-analog converter (DAC) is arranged in each channel between the respective first frequency mixers and the respective second frequency mixers.
9. The magnetic resonance system of claim 1 , wherein an amplifier is arranged in each channel downstream of the respective second frequency mixers.
10. The magnetic resonance system of claim 1 , wherein the at least one transmission coil system is configured as a movable local coil system.
11. The magnetic resonance system of claim 1 , wherein the at least one transmission coil system is configured as a permanently installed whole-body coil system.