Multi-nuclear imaging radio frequency power amplifier and multi-nuclear magnetic resonance imaging hardware system

Abstract

The present application relates to the technical field of data processing. Disclosed are a multi-nuclear imaging radio frequency power amplifier and a multi-nuclear magnetic resonance imaging hardware system. The multi-nuclear imaging radio frequency power amplifier comprises: a radio frequency signal input end, a radio frequency switch, a pre-compensation circuit, a voltage-controlled attenuator, a voltage-controlled phase shifter, a broadband radio frequency power amplifier, a broadband directional coupler and a radio frequency signal output end; a first output abnormality protection control circuit; a second output abnormality protection control circuit; an amplitude control circuit; and a phase control circuit. By means of the multi-nuclear imaging radio frequency power amplifier in the present invention, nonlinear correction can be performed on the amplitude and phase of a broadband radio frequency power amplifier, such that the broadband radio frequency power amplifier keeps meeting the requirements for high linearity and high power at an operating frequency point of a corresponding nuclide, so as to ensure the linear relationship between input and output signals of a radio frequency power amplifier and adequate signal strength, thereby avoiding the generation of artifacts due to signal distortion, and ensuring the accuracy and clarity of magnetic resonance imaging.

Description

Multi-core imaging RF power amplifier and multi-core magnetic resonance imaging hardware system Technical Field

[0001] The present invention relates to the technical field of power amplifiers, and in particular to a multi-core imaging radio frequency power amplifier and a multi-core magnetic resonance imaging hardware system. Background Art

[0002] Magnetic resonance metabolic imaging (MRI) uses tracers or molecular probes to reflect the molecular metabolic characteristics of an organism or organ by measuring the concentrations of these tracers and their metabolites. This allows for the study of metabolic abnormalities in various diseases, including cognitive impairment, tumors, and neurodegenerative diseases, facilitating diagnosis and monitoring of treatment efficacy. MRI has broad potential in clinical applications. For example, MRI with deuterium (2H) metabolism holds great promise for the study of the mechanisms and early diagnosis of tumors and neurodegenerative diseases. MRI with fluorine-19 (19F) metabolism is widely used in areas such as cell labeling, molecular imaging, and blood pool functional imaging.

[0003] As a core component of MRI radiofrequency systems, RF power amplifiers are required to have high output power and excellent linearity at the frequencies corresponding to the imaging nuclides, providing sufficient signal power and accurate signal transmission for high-quality imaging. For MRI multi-nuclear metabolic imaging, to meet the imaging requirements of different nuclides, RF power amplifiers need to operate within a wide frequency band. However, broadband RF power amplifiers span several octaves, and the parasitic parameters of the power transistors themselves lead to impedance dispersion, making it incompatible with achieving good power output and efficiency output across a wide frequency range. Furthermore, within this wide frequency range, phase differences at different frequencies can cause phase reversal, meaning that linear phase correction is not monotonic, increasing the difficulty of linearization correction.

[0004] Summary of the Invention

[0005] Based on this, it is necessary to address the technical problem that the existing RF power amplifier is difficult to maintain high linearity and high power at the operating frequency of the corresponding nuclide, and propose a multi-nuclear imaging RF power amplifier and a multi-nuclear magnetic resonance imaging hardware system.

[0006] In a first aspect, a multi-core imaging RF power amplifier is provided, which includes: an RF signal input end, an RF switch, a pre-compensation circuit, a voltage-controlled attenuator, a voltage-controlled phase shifter, a broadband RF power amplifier, a broadband directional coupler, and an RF signal output end, wherein the RF signal input end is connected to one end of the RF switch, the other end of the RF switch is connected to the RF input port of the voltage-controlled attenuator, the output end of the voltage-controlled attenuator is connected to the RF input port of the voltage-controlled phase shifter, the output end of the voltage-controlled phase shifter is connected to the input end of the broadband RF power amplifier, the output end of the broadband RF power amplifier is connected to the input end of the broadband directional coupler, and the through end of the broadband directional coupler is connected to the RF signal output end;

[0007] a first output abnormality protection control circuit from one end of the radio frequency switch to a reflection monitoring end of the broadband directional coupler;

[0008] a second output abnormality protection control circuit from one end of the radio frequency switch to the output monitoring end of the broadband directional coupler;

[0009] an amplitude control circuit from the output monitoring terminal to the voltage control terminal of the voltage-controlled attenuator, wherein the amplitude control circuit is used to perform nonlinear correction on the amplitude of the broadband radio frequency power amplifier;

[0010] A phase control circuit is provided from the output monitoring terminal to the voltage control terminal of the voltage-controlled phase shifter, wherein the phase control circuit is used to perform nonlinear correction on the phase of the broadband radio frequency power amplifier.

[0011] Furthermore, the first output abnormality protection control circuit includes a first amplitude detector, a first operational amplifier and a first D flip-flop;

[0012] The input end of the first amplitude demodulator is connected to the reflection monitoring end, the output end of the first amplitude demodulator is connected to one input end of the first operational amplifier, the other input end of the first operational amplifier is connected to a preset reflection protection reference voltage, the output end of the first operational amplifier is connected to the input end of the first D-type flip-flop, and the output end of the first D-type flip-flop is connected to the switch control end of the radio frequency switch;

[0013] The second output abnormality protection control circuit includes a second amplitude detector, a second operational amplifier and a second D-type contactor;

[0014] The input end of the second amplitude demodulator is connected to the output monitoring end, the output end of the second amplitude demodulator is connected to one input end of the second operational amplifier, the other input end of the second operational amplifier is connected to a preset forward protection voltage reference value, the output end of the second operational amplifier is connected to the input end of the second D trigger, and the output end of the second D trigger is connected to the switch control end of the radio frequency switch.

[0015] Furthermore, the amplitude control circuit includes a third operational amplifier, wherein the output terminal of the second amplitude detector is connected to one input terminal of the third operational amplifier, the other input terminal of the third operational amplifier is connected to a preset first voltage reference value, and the output terminal of the third operational amplifier is connected to the voltage control terminal of the voltage-controlled attenuator, wherein the first voltage reference value refers to the reference voltage after the RF input signal is converted by the amplitude detector;

[0016] The phase control circuit includes a fourth power amplifier and a phase detector, wherein the input end of the phase detector is connected to the output monitoring end, the output end of the phase detector is connected to one input end of the fourth op amp, the other input end of the second op amp is connected to a preset second voltage reference value, and the output end of the fourth op amp is connected to the voltage control end of the voltage-controlled phase shifter, wherein the second voltage reference value is a reference voltage after the RF input signal is converted by the phase detector.

[0017] Furthermore, the multi-core imaging RF power amplifier includes: an RF signal input end, a first power divider, a second power divider, a first selection switch, each analog negative feedback network, a second selection switch, a broadband RF power amplifier, a broadband directional coupler and an RF signal output end, wherein the RF signal input end is connected to the input end of the first power divider, one output end of the first power divider is connected to the input end of the first selection switch, the output end of the first selection switch is connected to the input end of the analog negative feedback network, the output end of the analog negative feedback network is connected to the input end of the second selection switch, the output end of the second selection switch is connected to the input end of the broadband RF power amplifier, the output end of the broadband RF power amplifier is connected to the input end of the broadband directional coupler, the output end of the broadband directional coupler is connected to the RF signal output end, and the other output end of the first power divider is connected to the input end of the second power divider;

[0018] a switch selection circuit extending from an output terminal of the second power divider to a switch control terminal of the first selection switch and a switch control terminal of the second selection switch, wherein the switch selection circuit is configured to synchronously control the conduction states of the first selection switch and the second selection switch, thereby selecting different analog negative feedback networks corresponding to different conduction states, each analog negative feedback network being configured to perform linearization correction for a signal of a specific frequency;

[0019] From the other output end of the second power divider and the coupling end of the broadband directional coupler to the analog negative feedback control circuit of the analog negative feedback network.

[0020] Furthermore, the switch selection circuit includes: a frequency identification circuit and a switch control circuit, wherein an output end of the second power divider is connected to an input end of the frequency identification circuit, an output end of the frequency identification circuit is connected to an input end of the switch control circuit, and an output end of the switch control circuit is connected to the first selection switch and the second selection switch.

[0021] Furthermore, the switch selection circuit includes: a first amplitude phase detector, a second amplitude phase detector, and an adaptive controller, wherein the other output end of the second power divider is connected to the input end of the first amplitude phase detector, the output end of the first amplitude phase detector is connected to the adaptive controller, the coupling end of the broadband directional coupler is connected to the input end of the second amplitude phase detector, the output end of the second amplitude phase detector is connected to the input end of the adaptive controller, and the output end of the adaptive controller is connected to the analog negative feedback network.

[0022] Furthermore, the multi-core imaging RF power amplifier includes: an RF signal input end, a first broadband directional coupler, a delay line, a synthesizer, a broadband RF power amplifier, a second broadband directional coupler, a power splitter, a first selection switch, each analog predistorter and an RF signal output end, wherein the RF signal input end is connected to the input end of the first broadband directional coupler, the output end of the first broadband directional coupler is connected to the input end of the delay line, the output end of the delay line is connected to an input end of the synthesizer, the output end of the synthesizer is connected to the input end of the broadband RF power amplifier, the output end of the broadband RF power amplifier is connected to the input end of the second broadband directional coupler, the output end of the second broadband directional coupler is connected to the RF output end, the coupling end of the first broadband directional coupler is connected to the input end of the power splitter, and one output end of the power splitter is connected to the input end of the first selection switch;

[0023] an analog predistortion control circuit connected from the output of the first selection switch to another input of the synthesizer, the analog predistortion control circuit being used to perform linearization correction on a signal of a specific frequency;

[0024] A nonlinear distortion identification circuit is connected from the coupling end of the second broadband directional coupler to the switch control end of the first selection switch, wherein the nonlinear distortion identification circuit is used to control the conduction and closing of the first selection switch.

[0025] Furthermore, the analog predistortion control circuit includes various analog predistorters, a second selection switch, and a third selection switch;

[0026] The output end of the first selection switch is connected to the input end of the second selection switch, the output end of the second selection switch is connected to the input end of the analog predistorter, the output end of the analog predistorter is connected to the input end of the third selection switch, and the output end of the third selection switch is connected to the other input end of the synthesizer;

[0027] The multi-core imaging RF power amplifier also includes a frequency identification circuit and a switch control circuit; the other output end of the power divider is connected to the input end of the frequency identification circuit, the output end of the frequency identification circuit is connected to the input end of the switch control circuit, and the output end of the switch control circuit is respectively connected to the switch control end of the second selection switch and the switch control end of the third selection switch, and the switch control circuit is used to synchronously control the conduction and closing of the second selection switch and the third selection switch.

[0028] Furthermore, the nonlinear distortion identification circuit further includes a phase detector and a comparator;

[0029] The coupling end of the second broadband directional coupler is connected to the input end of the phase detector, the output end of the phase detector is connected to one input end of the comparator, the other input end of the comparator is a preset critical value of the broadband RF power amplifier during nonlinear distortion, and the output end of the comparator is connected to the switch control end of the first selection switch.

[0030] In a second aspect, a multi-nuclear magnetic resonance imaging hardware system is provided, wherein the multi-nuclear magnetic resonance imaging hardware system includes the multi-nuclear imaging radio frequency power amplifier described above.

[0031] The multi-core imaging RF power amplifier proposed in the present invention includes: an RF signal input end, an RF switch, a pre-compensation circuit, a voltage-controlled attenuator, a voltage-controlled phase shifter, a broadband RF power amplifier, a broadband directional coupler, and an RF signal output end, wherein the RF signal input end is connected to the input end of the RF switch, the output end of the RF switch is connected to the RF input port of the voltage-controlled attenuator, the output end of the voltage-controlled attenuator is connected to the RF input port of the voltage-controlled phase shifter, the output end of the voltage-controlled phase shifter is connected to the input end of the broadband RF power amplifier, the output end of the broadband RF power amplifier is connected to the input end of the broadband directional coupler, and the through end of the broadband directional coupler is connected to the RF The invention relates to a directional coupler for RF power amplifiers, ... BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] in:

[0034] FIG1 is a first structural block diagram of a multi-core imaging RF power amplifier according to an embodiment;

[0035] FIG2 is a second structural block diagram of a multi-core imaging RF power amplifier according to one embodiment;

[0036] FIG3 is a third structural block diagram of a multi-core imaging RF power amplifier according to one embodiment;

[0037] FIG4 is a block diagram of a broadband RF power amplifier according to an embodiment;

[0038] FIG5 is a structural block diagram of a multi-nuclear magnetic resonance imaging hardware system in another embodiment. DETAILED DESCRIPTION

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of the application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0040] Please refer to Figure 1, which is a schematic diagram of a multi-core imaging RF power amplifier applied to a multi-core magnetic resonance imaging hardware system provided by an embodiment of the present invention, comprising: an RF signal input terminal, an RF switch, a pre-compensation circuit, a voltage-controlled attenuator, a voltage-controlled phase shifter, a broadband RF power amplifier, a broadband directional coupler, and an RF signal output terminal, wherein the RF signal input terminal is connected to the input terminal of the RF switch, the output terminal of the RF switch is connected to the RF input port of the voltage-controlled attenuator, the output terminal of the voltage-controlled attenuator is connected to the RF input port of the voltage-controlled phase shifter, the output terminal of the voltage-controlled phase shifter is connected to the input terminal of the broadband RF power amplifier, the output terminal of the broadband RF power amplifier is connected to the input terminal of the broadband directional coupler, and the through terminal of the broadband directional coupler is connected to the RF signal output terminal;

[0041] a first output abnormality protection control circuit from the switch control terminal of the radio frequency switch to the reflection monitoring terminal of the broadband directional coupler;

[0042] a second output abnormality protection control circuit from the switch control terminal of the radio frequency switch to the output monitoring terminal of the broadband directional coupler;

[0043] an amplitude control circuit extending from the output monitoring terminal to the voltage control terminal of the voltage-controlled attenuator, wherein the amplitude control circuit is used to perform nonlinear correction on the amplitude of the broadband RF power amplifier;

[0044] A phase control circuit is provided from the output monitoring terminal to the voltage control terminal of the voltage-controlled phase shifter, wherein the phase control circuit is used to perform nonlinear correction on the phase of the broadband radio frequency power amplifier.

[0045] The broadband directional coupler uses a microstrip dual-broadband directional coupler, which employs two identical mirror-symmetrical structures to monitor forward power and reflected power, respectively. The output of the broadband RF power amplifier passes through the broadband directional coupler and is output from the through port (RFout). The forward power is monitored via the output monitoring terminal (FWD), and the reflected power is monitored via the reflection monitoring terminal (REF). Unused ports require a 50Ω load for impedance matching. The first output abnormality protection control circuit shuts off and latches the RF input signal via the RF switch to prevent damage to the system caused by excessive reflected power. The second output abnormality protection control circuit protects the broadband RF power amplifier from output abnormalities by controlling the RF switch. The phase control circuit regulates the voltage-controlled phase shifter to correct the phase nonlinearity of the broadband RF power amplifier. The amplitude control circuit regulates the voltage-controlled attenuator to correct the amplitude nonlinearity of the broadband RF power amplifier.

[0046] To meet the application bandwidth of RF power amplifiers for multi-nuclear magnetic resonance imaging (MRI), the aforementioned circuits are insufficient to meet the high linearity requirements. Therefore, a pre-compensation circuit is needed to balance the nonlinearity of the broadband RF power amplifier output. The compensation method is as follows: First, the nonlinear distortion of the power amplifier must be analyzed and modeled. Without introducing other linearization correction schemes, an open-loop frequency domain scan is performed on the broadband RF power amplifier to obtain the nonlinear distortion curve of the broadband RF power amplifier itself within the frequency range. Based on the characteristics of the nonlinear distortion, a loss linearization model can be established to compensate for the nonlinear characteristics of the broadband RF power amplifier, offsetting the nonlinear distortion of the broadband RF power amplifier and thus improving the linearity and stability of the broadband RF power amplifier. The pre-compensation circuit can be understood as a compensation circuit that is opposite to the gain and phase curves of the power amplifier output and is used to balance the nonlinearity of the power amplifier output.

[0047] The multi-nuclear imaging radio frequency power amplifier of the present invention can perform nonlinear correction on the amplitude and phase of the broadband radio frequency power amplifier, so that it maintains high linearity and high power requirements at the operating frequency of the corresponding nuclide, ensures the linear relationship and sufficient signal strength of the input and output signals of the radio frequency power amplifier, avoids signal distortion and artifacts, and ensures the accuracy and clarity of magnetic resonance imaging.

[0048] In a preferred implementation, the first output abnormality protection control circuit includes a first amplitude detector, a first operational amplifier, and a first D flip-flop;

[0049] The input end of the first amplitude demodulator is connected to the reflection monitoring end, the output end of the first amplitude demodulator is connected to one input end of the first operational amplifier, the other input end of the first operational amplifier is connected to a preset reflection protection reference voltage, the output end of the first operational amplifier is connected to the input end of the first D-type flip-flop, and the output end of the first D-type flip-flop is connected to the switch control end of the radio frequency switch;

[0050] The second output abnormality protection control circuit includes a second amplitude detector, a second operational amplifier and a second D-type contactor;

[0051] The input end of the second amplitude demodulator is connected to the output monitoring end, the output end of the second amplitude demodulator is connected to one input end of the second operational amplifier, the other input end of the second operational amplifier is connected to a preset forward protection voltage reference value, the output end of the second operational amplifier is connected to the input end of the second D trigger, and the output end of the second D trigger is connected to the switch control end of the radio frequency switch.

[0052] Specifically, as shown in Figure 1, in the first output abnormality protection control circuit, the reflected power at the reflection monitoring terminal (REF) is compared with the reflection protection reference voltage (VRef1). When the reflected power exceeds the reflection protection reference voltage, the D flip-flop shuts down and latches the RF input signal to prevent excessive reflected power from damaging the system. In the second output abnormality protection control circuit, the power signal at the output monitoring terminal (FWD) undergoes amplitude and phase power conversion after passing through a resistor power divider. The converted voltage is then compared with the forward protection voltage reference value (VRef2) to determine whether the output power exceeds the threshold, thereby protecting the broadband RF power amplifier in the output abnormality state.

[0053] In a preferred implementation, the amplitude control circuit includes a third operational amplifier, wherein the output terminal of the second amplitude detector is connected to one input terminal of the third operational amplifier, the other input terminal of the third operational amplifier is connected to a preset first voltage reference value, and the output terminal of the third operational amplifier is connected to the voltage control terminal of the voltage-controlled attenuator, wherein the first voltage reference value refers to the reference voltage after the RF input signal is converted by the amplitude detector;

[0054] The phase control circuit includes a fourth power amplifier and a phase detector, wherein the input end of the phase detector is connected to the output monitoring end, the output end of the phase detector is connected to one input end of the fourth op amp, the other input end of the second op amp is connected to a preset second voltage reference value, and the output end of the fourth op amp is connected to the voltage control end of the voltage-controlled phase shifter, wherein the second voltage reference value is a reference voltage after the RF input signal is converted by the phase detector.

[0055] Specifically, as shown in Figure 1, in the amplitude control circuit, the voltage after amplitude conversion of the second amplitude detector output is compared with the amplitude value (VRef3) of the RF input signal to obtain a conditioned error signal, and the voltage-controlled attenuator is regulated by the error signal to complete the nonlinear correction of the amplitude; in the phase control circuit, the voltage after phase conversion of the phase detector output is compared with the phase value (VRef4) of the RF input signal, and the voltage-controlled phase shifter is regulated by the amplified error signal to achieve phase nonlinear correction of the broadband RF power amplifier.

[0056] In one embodiment, the multi-core imaging RF power amplifier includes: an RF signal input terminal, a first power divider, a second power divider, a first selection switch, each analog negative feedback network, a second selection switch, a broadband RF power amplifier, a broadband directional coupler and an RF signal output terminal, wherein the RF signal input terminal is connected to the input terminal of the first power divider, an output terminal of the first power divider is connected to the input terminal of the first selection switch, the output terminal of the first selection switch is connected to the input terminal of the analog negative feedback network, the output terminal of the analog negative feedback network is connected to the input terminal of the second selection switch, the output terminal of the second selection switch is connected to the input terminal of the broadband RF power amplifier, and the output terminal of the broadband RF power amplifier is connected to the broadband directional coupler. The first power divider is connected to the input end of the coupler, the output end of the broadband directional coupler is connected to the RF signal output end, and the other output end of the first power divider is connected to the input end of the second power divider; a switch selection circuit is connected from one output end of the second power divider to the switch control end of the first selection switch and the switch control end of the second selection switch, wherein the switch selection circuit is used to synchronously control the conduction state of the first selection switch and the second selection switch, thereby selecting different analog negative feedback networks corresponding to different conduction states, each of the analog negative feedback networks being used to perform linearization correction for a signal of a specific frequency; and an analog negative feedback control circuit is connected from the other output end of the second power divider and the coupling end of the broadband directional coupler to the analog negative feedback network.

[0057] In a preferred implementation, the switch selection circuit includes: a frequency identification circuit and a switch control circuit, wherein an output end of the second power divider is connected to an input end of the frequency identification circuit, an output end of the frequency identification circuit is connected to an input end of the switch control circuit, and an output end of the switch control circuit is connected to the first selection switch and the second selection switch.

[0058] In a preferred implementation, the switch selection circuit includes: a first amplitude phase detector, a second amplitude phase detector, and an adaptive controller, wherein the other output end of the second power divider is connected to the input end of the first amplitude phase detector, the output end of the first amplitude phase detector is connected to the adaptive controller, the coupling end of the broadband directional coupler is connected to the input end of the second amplitude phase detector, the output end of the second amplitude phase detector is connected to the input end of the adaptive controller, and the output end of the adaptive controller is connected to the analog negative feedback network.

[0059] Specifically, as shown in Figure 2, the RF input signal first passes through a 3dB power splitter 1, which splits the RF input signal into two paths. One path is transmitted to the input end of the first selector switch, and the other path is further divided into two equal signals by power splitter 2. One path is used for frequency identification. That is, the signal is identified by the frequency identification circuit. After identification, the switch control circuit outputs the selector switch control signal, which is used to synchronously control the conduction state of selector switch 1 and selector switch 2. Different conduction states of the selector switches correspond to different analog negative feedback networks. Each analog negative feedback network performs linear correction for signals of a specific frequency. The other path of power splitter 2 is output to amplitude and phase detector 1, which identifies and transforms the amplitude and phase of the input signal and inputs it to the adaptive controller. The coupling end of the broadband directional coupler couples the input signal and transmits it to amplitude and phase detector 2, which identifies and transforms the amplitude and phase of the input signal. The converted amplitude and phase information is compared and processed by the adaptive controller. The processed signal serves as the control signal of the analog negative feedback control network to control the analog negative feedback network. After selecting the conduction state by selecting switch 1, the corresponding analog negative feedback network will adjust the amplitude and phase of the input signal according to the control signal. The corrected signal is transmitted to the broadband RF power amplifier by selecting the corresponding conduction state by selecting switch 2, realizing adaptive segmented analog negative feedback linearization correction, so that the broadband RF power amplifier can achieve narrowband linearization correction at multiple frequency points, ensuring the high linearity and high stability of the power amplifier during imaging of different radionuclides.

[0060] In one embodiment, the multi-core imaging RF power amplifier includes: an RF signal input end, a first broadband directional coupler, a delay line, a synthesizer, a broadband RF power amplifier, a second broadband directional coupler, a power splitter, a first selection switch, various analog predistorters, and an RF signal output end, wherein the RF signal input end is connected to the input end of the first broadband directional coupler, the output end of the first broadband directional coupler is connected to the input end of the delay line, the output end of the delay line is connected to an input end of the synthesizer, the output end of the synthesizer is connected to the input end of the broadband RF power amplifier, the output end of the broadband RF power amplifier is connected to the input end of the second broadband directional coupler, the output end of the second broadband directional coupler is connected to the RF output end, the coupling end of the first broadband directional coupler is connected to the input end of the power splitter, and one output end of the power splitter is connected to the input end of the first selection switch;

[0061] an analog predistortion control circuit connected from the output of the first selection switch to another input of the synthesizer, the analog predistortion control circuit being used to perform linearization correction on a signal of a specific frequency;

[0062] A nonlinear distortion identification circuit is connected from the coupling end of the second broadband directional coupler to the switch control end of the first selection switch, wherein the nonlinear distortion identification circuit is used to control the conduction and closing of the first selection switch.

[0063] In a preferred implementation, the analog predistortion control circuit includes various analog predistorters, a second selection switch, and a third selection switch;

[0064] The output end of the first selection switch is connected to the input end of the second selection switch, the output end of the second selection switch is connected to the input end of the analog predistorter, the output end of the analog predistorter is connected to the input end of the third selection switch, and the output end of the third selection switch is connected to the other input end of the synthesizer;

[0065] The multi-core imaging radio frequency power amplifier further includes a frequency identification circuit and a switch control circuit;

[0066] The other output end of the power divider is connected to the input end of the frequency identification circuit, the output end of the frequency identification circuit is connected to the input end of the switch control circuit, the output end of the switch control circuit is respectively connected to the switch control end of the second selection switch and the switch control end of the third selection switch, and the switch control circuit is used to synchronously control the conduction and closing of the second selection switch and the third selection switch.

[0067] In a preferred implementation, the nonlinear distortion identification circuit further includes a phase detector and a comparator;

[0068] The coupling end of the second broadband directional coupler is connected to the input end of the phase detector, the output end of the phase detector is connected to one input end of the comparator, the other input end of the comparator is a preset critical value of the broadband RF power amplifier during nonlinear distortion, and the output end of the comparator is connected to the switch control end of the first selection switch.

[0069] Specifically, as shown in Figure 3, the RF input signal first passes through a broadband directional coupler 1, and then through a delay line to be synthesized with the corrected signal. The synthesized signal is then input into a broadband RF power amplifier. The delay line is mainly used to compensate for the delay caused by the signal on the correction channel passing through various devices, so that the two signals can maintain synchronization when finally superimposed. The signal at the coupling end of the qualitative coupler 1 is divided into two paths by a power divider. One path uses a frequency recognition circuit to identify the frequency. According to different frequency switching control circuits, different control signals are output to synchronously control the conduction state of the selection switch 2 and the selection switch 3. Different conduction states of the selection switches correspond to different analog predistorters. Each analog predistorter will perform linearization correction on signals of a specific frequency. The other signal of the power divider serves as the input of the selection switch 1; the output of the broadband RF power amplifier is coupled by the directional coupler 2 and then passed through the amplitude detector for amplitude identification. After identification, it is compared with the preset reference value (VRef). The reference value is the critical value at which the power amplifier begins to exhibit nonlinear distortion. That is, when the power amplifier exhibits nonlinear distortion, a control signal will be output to control the selection switch 1 to be turned on. After turning on, the input signal will be transmitted by the selection switch 2 to the analog predistorter of the corresponding frequency for signal identification and processing. The identified and processed signal is synthesized and compensated with the signal of the other input of the synthesizer through the selection switch 3, thereby completing the signal compensation and realizing the linearization correction of the broadband RF power amplifier.

[0070] As an example, as shown in Figure 4, a broadband RF amplifier uses a cascaded amplification structure. A low-power input signal is amplified by the preamplifier and driver stages, achieving the output power required by the final stage. This power is then evenly distributed to the final-stage power transistors via a power divider. Finally, a power combiner is used for combined output. A broadband matching circuit transforms the impedance between the power transistors and the transmission link, ensuring maximum power transmission efficiency. The tank circuit (CBB) design utilizes the charge and discharge characteristics of capacitors during pulsed operation to provide sufficient peak current for the driver and final-stage power transistors, ensuring the stability of the power amplifier during long pulse output.

[0071] In one embodiment, the multi-nuclear magnetic resonance imaging hardware system includes at least one of the multi-nuclear imaging radio frequency power amplifiers described above. Specifically, the multi-nuclear imaging radio frequency power amplifier used in the multi-nuclear magnetic resonance imaging hardware system can adopt a multi-stage amplification structure and a unique linearization correction method, so that it can maintain excellent linearity even at higher power output. Suitable devices are selected for the application frequency and corresponding matching circuits are designed to meet the imaging applications of different nuclides. The structural block diagram of the multi-nuclear magnetic resonance imaging hardware system is shown in Figure 5. The main magnet is the core of the multi-nuclear magnetic resonance imaging hardware system, which is used to provide the static magnetic field required for the atomic nuclei to produce nuclear magnetic resonance phenomena. The main function of the gradient system is to spatially encode the magnetic resonance signal. The output signal of the gradient power amplifier controls the gradient coil to generate corresponding gradient magnetic fields in the X, Y, and Z directions for generating frequency encoding and phase encoding. The control system is used to schedule and control the various modules of the entire system, so that each module can realize the corresponding function and signal control, and display the final image. The radio frequency system is a key factor in determining the signal-to-noise ratio and image uniformity. This is also the main structure that distinguishes magnetic resonance multi-nuclear metabolic imaging from conventional magnetic resonance imaging. It includes a radio frequency power amplifier, a radio frequency transceiver control switch, and a radio frequency coil. The small radio frequency signal output by the spectrometer generates sufficient radio frequency power to excite the multi-nuclear radio frequency coil through the multi-nuclear imaging radio frequency power amplifier, thereby generating a radio frequency magnetic field to deflect the atomic nuclei. The receiving coil receives the magnetic resonance signal transmitted back from the patient's body and hands it over to the low-noise amplifier for amplification and processing. The processed signal is processed and imaged by the spectrometer system. The multi-nuclear imaging radio frequency power amplifier designed by the present invention can optimize the existing multi-nuclear magnetic resonance imaging hardware system. The proposed multi-nuclear imaging radio frequency power amplifier replaces the original 1H imaging and multi-nuclear imaging power amplifiers, and can optimize the multi-nuclear magnetic resonance imaging hardware system transmission chain from the original two-way to a single-way, reducing system costs and simplifying the operation process.

Claims

1. A multi-core imaging radio frequency power amplifier, characterized in that, The multi-core imaging radio frequency power amplifier includes: a radio frequency signal input terminal, a radio frequency switch, a pre-compensation circuit, a voltage-controlled attenuator, a voltage-controlled phase shifter, a broadband radio frequency power amplifier, a broadband directional coupler, and a radio frequency signal output terminal. Among them, the radio frequency signal input terminal is connected to the input terminal of the radio frequency switch, the output terminal of the radio frequency switch is connected to the radio frequency input port of the voltage-controlled attenuator, the output terminal of the voltage-controlled attenuator is connected to the radio frequency input port of the voltage-controlled phase shifter, the output terminal of the voltage-controlled phase shifter is connected to the input terminal of the broadband radio frequency power amplifier, the output terminal of the broadband radio frequency power amplifier is connected to the input terminal of the broadband directional coupler, and the through end of the broadband directional coupler is connected to the radio frequency signal output terminal; A first output abnormal protection control circuit from the switch control terminal of the radio frequency switch to the reflection monitoring terminal of the broadband directional coupler; A second output abnormal protection control circuit from the switch control terminal of the radio frequency switch to the output monitoring terminal of the broadband directional coupler; An amplitude control circuit from the output monitoring terminal to the voltage control terminal of the voltage-controlled attenuator, where the amplitude control circuit is used to perform non-linear correction on the amplitude of the broadband radio frequency power amplifier; A phase control circuit from the output monitoring terminal to the voltage control terminal of the voltage-controlled phase shifter, where the phase control circuit is used to perform non-linear correction on the phase of the broadband radio frequency power amplifier.

2. The multi-core imaging radio frequency power amplifier according to claim 1, wherein The first output abnormal protection control circuit includes a first amplitude discriminator, a first operational amplifier, and a first D flip-flop; The input terminal of the first amplitude discriminator is connected to the reflection monitoring terminal, the output terminal of the first amplitude discriminator is connected to one input terminal of the first operational amplifier, the other input terminal of the first operational amplifier is connected to a preset reflection protection reference voltage, the output terminal of the first operational amplifier is connected to the input terminal of the first D flip-flop, and the output terminal of the first D flip-flop is connected to the switch control terminal of the radio frequency switch; The second output abnormal protection control circuit includes a second amplitude discriminator, a second operational amplifier, and a second D flip-flop; The input terminal of the second amplitude discriminator is connected to the output monitoring terminal, the output terminal of the second amplitude discriminator is connected to one input terminal of the second operational amplifier, the other input terminal of the second operational amplifier is connected to a preset forward protection voltage reference value, the output terminal of the second operational amplifier is connected to the input terminal of the second D flip-flop, and the output terminal of the second D flip-flop is connected to the switch control terminal of the radio frequency switch.

3. The multi-core imaging radio frequency power amplifier according to claim 2, wherein, The amplitude control circuit includes a third operational amplifier. Among them, the output terminal of the second amplitude discriminator is connected to one input terminal of the third operational amplifier, the other input terminal of the third operational amplifier is connected to a preset first voltage reference value, and the output terminal of the third operational amplifier is connected to the voltage control terminal of the voltage-controlled attenuator. The first voltage reference value refers to the reference voltage after the radio frequency input signal is converted by the amplitude discriminator; The phase control circuit includes a fourth power amplifier and a phase detector. Among them, the input end of the phase detector is connected to the output monitoring end, the output end of the phase detector is connected to one input end of the fourth operational amplifier, the other input end of the second operational amplifier is connected to a preset second voltage reference value, and the output end of the fourth operational amplifier is connected to the voltage control end of the voltage-controlled phase shifter. Among them, the second voltage reference value is the reference voltage after the radio frequency input signal is converted by the phase detector.

4. A multi-core imaging radio frequency power amplifier, characterized in that, The multi-core imaging radio frequency power amplifier includes: a radio frequency signal input end, a first power divider, a second power divider, a first selection switch, each analog negative feedback network, a second selection switch, a broadband radio frequency power amplifier, a broadband directional coupler, and a radio frequency signal output end. Among them, the radio frequency signal input end is connected to the input end of the first power divider, one output end of the first power divider is connected to the input end of the first selection switch, the output end of the first selection switch is connected to the input end of the analog negative feedback network, the output end of the analog negative feedback network is connected to the input end of the second selection switch, the output end of the second selection switch is connected to the input end of the broadband radio frequency power amplifier, the output end of the broadband radio frequency power amplifier is connected to the input end of the broadband directional coupler, the output end of the broadband directional coupler is connected to the radio frequency signal output end, and the other output end of the first power divider is connected to the input end of the second power divider; A switching selection circuit from one output end of the second power divider to the switching control end of the first selection switch and the switching control end of the second selection switch. Among them, the switching selection circuit is used to synchronously control the conduction states of the first selection switch and the second selection switch, so as to select different analog negative feedback networks corresponding to different conduction states. Each analog negative feedback network is used to perform linearization correction on signals of a specific frequency; An analog negative feedback regulation circuit from the other output end of the second power divider and the coupling end of the broadband directional coupler to the analog negative feedback network.

5. The multi-core imaging radio frequency power amplifier according to claim 4, wherein, The switching selection circuit includes: a frequency identification circuit and a switching control circuit. Among them, one output end of the second power divider is connected to the input end of the frequency identification circuit, the output end of the frequency identification circuit is connected to the input end of the switching control circuit, and the output end of the switching control circuit is connected to the first selection switch and the second selection switch.

6. The multi-core imaging radio frequency power amplifier according to claim 4, wherein The switching selection circuit includes: a first amplitude and phase detector, a second amplitude and phase detector, and an adaptive controller. Among them, the other output end of the second power divider is connected to the input end of the first amplitude and phase detector, the output end of the first amplitude and phase detector is connected to the adaptive controller, the coupling end of the broadband directional coupler is connected to the input end of the second amplitude and phase detector, the output end of the second amplitude and phase detector is connected to the input end of the adaptive controller, and the output end of the adaptive controller is connected to the analog negative feedback network.

7. A multi-core imaging radio frequency power amplifier, characterized in that, The multi-core imaging radio frequency power amplifier includes: a radio frequency signal input end, a first broadband directional coupler, a delay line, a synthesizer, a broadband radio frequency power amplifier, a second broadband directional coupler, a power divider, a first selection switch, each analog pre-distortion device, and a radio frequency signal output end. Among them, the radio frequency signal input end is connected to the input end of the first broadband directional coupler, the output end of the first broadband directional coupler is connected to the input end of the delay line, the output end of the delay line is connected to one input end of the synthesizer, the output end of the synthesizer is connected to the input end of the broadband radio frequency power amplifier, the output end of the broadband radio frequency power amplifier is connected to the input end of the second broadband directional coupler, the output end of the second broadband directional coupler is connected to the radio frequency output end, the coupled end of the first broadband directional coupler is connected to the input end of the power divider, and one output end of the power divider is connected to the input end of the first selection switch; An analog pre-distortion control circuit from the output end of the first selection switch to the other input end of the synthesizer, and the analog pre-distortion control circuit is used to perform linearization correction on signals of specific frequencies; A non-linear distortion identification circuit from the coupled end of the second broadband directional coupler to the switch control end of the first selection switch, where the non-linear distortion identification circuit is used to control the conduction and closing of the first selection switch.

8. The multi-core imaging radio frequency power amplifier according to claim 7, characterized in that, The analog pre-distortion control circuit includes each analog pre-distortion device, a second selection switch, and a third selection switch; The output end of the first selection switch is connected to the input end of the second selection switch, the output end of the second selection switch is connected to the input end of the analog pre-distortion device, the output end of the analog pre-distortion device is connected to the input end of the third selection switch, and the output end of the third selection switch is connected to the other input end of the synthesizer; The multi-core imaging radio frequency power amplifier further includes a frequency identification circuit and a switch control circuit; The other output end of the power divider is connected to the input end of the frequency identification circuit, the output end of the frequency identification circuit is connected to the input end of the switch control circuit, and the output end of the switch control circuit is respectively connected to the switch control end of the second selection switch and the switch control end of the third selection switch. The switch control circuit is used to synchronously control the conduction and closing of the second selection switch and the third selection switch.

9. The multi-core imaging radio frequency power amplifier according to claim 8, wherein, The non-linear distortion identification circuit further includes a phase discriminator and a comparator; The coupled end of the second broadband directional coupler is connected to the input end of the phase discriminator, the output end of the phase discriminator is connected to one input end of the comparator, the other input end of the comparator is the critical value of the preset broadband radio frequency power amplifier in the case of non-linear distortion, and the output end of the comparator is connected to the switch control end of the first selection switch.

10. A multi-nuclear magnetic resonance imaging hardware system, characterized in that, The multi-nuclear magnetic resonance imaging hardware system includes at least one multi-core imaging radio frequency power amplifier as described in any one of claims 1 to 9.

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