Power control device of radio frequency power amplifier and radio frequency transmission system of MRI system

Abstract

The present invention provides a power control device of a radio frequency power amplifier and a radio frequency transmitting system of a magnetic resonance imaging system. The power control device comprises: a power control module, which is used to receive a control voltage to control the output power of the radio frequency power amplifier; a voltage detection module, which is used to detect the working voltage provided to the radio frequency power amplifier and output the detection voltage; and a voltage adjustment module, which is used to adjust the control voltage received by the power control module based on the detection voltage to adjust the output power of the radio frequency power amplifier.

Description

Technical Field

[0001] The present invention generally relates to the field of medical imaging, and more particularly to a power control device for a radio frequency power amplifier and a radio frequency transmission system for a magnetic resonance imaging (MRI) system. Background Art

[0002] Magnetic resonance imaging systems have been widely used in the field of medical diagnosis, and they mainly include a main magnet, a gradient field system, an RF transmission link, an RF transmission coil assembly, and an RF receiving link. The RF transmission link generally includes an RF generator and an RF power amplifier assembly, wherein the RF generator generates an RF pulse signal, which is amplified by the RF amplifier and then transmitted to the RF transmission coil. The RF transmission coil responds to the amplified RF pulse signal to transmit an RF excitation pulse to the object to be scanned (e.g., a patient).

[0003] During the imaging process, image quality problems, such as image distortion, may be caused by nonlinearity of the radio frequency link. Therefore, how to improve the linearity of the radio frequency link has attracted the attention of those skilled in the art. Summary of the invention

[0004] The object of the present invention is to overcome the above and / or other problems in the prior art.

[0005] An embodiment of the present invention provides a power control device for a radio frequency power amplifier, comprising:

[0006] A power control module, which is used to receive a control voltage to control the output power of the radio frequency power amplifier;

[0007] a voltage detection module, which is used to detect the operating voltage provided to the RF power amplifier and output a detection voltage; and

[0008] A voltage adjustment module is used to adjust the control voltage received by the power control module based on the detection voltage to adjust the output power of the radio frequency power amplifier.

[0009] Optionally, the voltage adjustment module includes a voltage conversion unit and an adjustable voltage generating unit, and the voltage conversion unit is used to receive the adjustable reference voltage generated by the adjustable voltage generating unit, and convert the detection voltage into the control voltage based on the adjustable reference voltage.

[0010] Optionally, the voltage conversion unit includes a first conversion unit and a second conversion unit, the first conversion unit is used to scale down the detection voltage to a first voltage, and the second conversion unit is used to convert the first voltage into the control voltage based on the adjustable reference voltage.

[0011] Optionally, the first conversion unit comprises a proportional amplifier.

[0012] Optionally, the second conversion unit includes a reference voltage terminal, an input terminal and an output terminal, the reference voltage terminal of the second conversion unit is used to receive the adjustable reference voltage from the adjustable voltage generating module, the input terminal of the second conversion unit is used to receive the first voltage, and the output terminal of the second conversion unit is used to output the control voltage after calculating the first voltage and the adjustable reference voltage.

[0013] Optionally, the power control module includes a variable voltage attenuator, and the second conversion unit includes an inverter circuit and an adder circuit, the inverter circuit is used to convert the first voltage into a negative voltage, and the adder circuit is used to add the negative voltage to the adjustable reference voltage to generate the control voltage.

[0014] Optionally, the power control module comprises a voltage gain amplifier, and the second conversion circuit comprises a subtractor circuit for subtracting the first voltage from the adjustable reference voltage to generate the control voltage.

[0015] Optionally, the adjustable reference voltage is determined based on a drop value between an operating voltage of the RF power amplifier and a desired operating voltage.

[0016] Optionally, the power control module is used to receive a first RF power signal, and attenuate the first RF power signal based on the control voltage to output a second RF power signal to the RF power amplifier, and the RF power amplifier is used to amplify the second RF signal.

[0017] Another embodiment of the present invention further provides a radio frequency transmission system of a magnetic resonance imaging system, comprising:

[0018] A radio frequency signal generator, which is used to transmit a radio frequency power signal;

[0019] a power control module, configured to receive the radio frequency power signal and attenuate the radio frequency power signal based on a control voltage thereof to output an attenuated radio frequency power signal;

[0020] a radio frequency power amplifier, which is used to amplify the attenuated radio frequency power signal to output a high-power radio frequency signal; and

[0021] A voltage adjustment module is used to adjust the control voltage received by the power control module based on the change of the operating voltage of the radio frequency power amplifier, so as to adjust the high-power radio frequency signal.

[0022] Other features and aspects will become apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention may be better understood by describing exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0024] Figure 1 A schematic structural diagram of a magnetic resonance imaging system according to an embodiment is shown;

[0025] Figure 2 A schematic diagram showing a change in RF gain caused by a change in the operating voltage of an RF power amplifier in an example is shown;

[0026] Figure 3 shows a waveform diagram when the RF power pulse amplitude decreases;

[0027] Figure 4 shows a waveform diagram of a radio frequency power pulse when radio frequency oscillation occurs;

[0028] Figure 5 A module diagram of a radio frequency power control device according to an embodiment of the present invention is shown;

[0029] Figure 6 A module diagram of a radio frequency power control device according to another embodiment of the present invention is shown;

[0030] Figure 7 A module diagram of a radio frequency power control device according to another embodiment of the present invention is shown;

[0031] Figure 8 A module diagram of a radio frequency power control device according to another embodiment of the present invention is shown;

[0032] Fig. 9 A module diagram of a radio frequency transmitting system of a magnetic resonance imaging system according to an embodiment of the present invention is shown;

[0033] Fig.10 The radio frequency power pulse waveform obtained after the radio frequency power control device according to the embodiment of the present invention is used to adjust the output power of the radio frequency power amplifier is shown;

[0034] Fig.11 The gain curve of the radio frequency transmission link in the existing magnetic resonance imaging system is shown;

[0035] Fig.12 The gain curve of the radio frequency transmission link obtained after adopting the embodiment of the present invention is shown. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention will be described below. It should be noted that in the specific description of these embodiments, in order to provide a concise description, it is impossible for this specification to provide a detailed description of all the features of the actual embodiments. It should be understood that in the actual implementation of any embodiment, just as in the process of any engineering project or design project, in order to achieve the specific goals of the developer and to meet system-related or business-related restrictions, various specific decisions are often made, and this will also change from one embodiment to another. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the content disclosed by the present invention, some changes such as design, manufacturing or production based on the technical content disclosed in this disclosure are just conventional technical means, and should not be understood as insufficient content of this disclosure.

[0037] Unless otherwise defined, the technical or scientific terms used in the claims and the specification shall have the usual meaning understood by persons with ordinary skills in the technical field to which the invention belongs. The words "first", "second" and similar words used in the patent application specification and the claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "One" or "one" and other similar words do not indicate a quantitative limitation, but indicate the existence of at least one. "Include" or "comprises" and other similar words mean that the elements or objects appearing before "include" or "comprises" include the elements or objects listed after "include" or "comprises" and their equivalent elements, and do not exclude other elements or objects. "Connected" or "connected" and other similar words are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0038] Figure 1 A schematic structural diagram of a magnetic resonance imaging system (MRI) according to an embodiment is shown, and the magnetic resonance imaging system 100 includes a scanner 110. The scanner 110 is used to perform magnetic resonance scanning on an object (e.g., a human body) 16 to generate image data of a region of interest of the object 16, and the region of interest may be a predetermined imaging site or imaging tissue.

[0039] The magnetic resonance imaging system 100 may further include a controller 120, which is coupled to the scanner 110 to control the scanner 110 to perform the above-mentioned magnetic resonance scanning process. Specifically, the controller 120 may send a sequence control signal to relevant components of the scanner 110 (e.g., a radio frequency generator and a gradient coil driver to be described below) through a sequence generator (not shown in the figure), so that the scanner 110 performs a preset scanning sequence.

[0040] Those skilled in the art will appreciate that the above-mentioned "scanning sequence" refers to a combination of pulses with specific amplitude, width, direction and timing applied when performing magnetic resonance imaging scans, and these pulses may generally include, for example, radio frequency pulses and gradient pulses. The radio frequency pulse may include, for example, a radio frequency transmission pulse for exciting protons in the human body to resonate. The gradient pulse may include, for example, a slice selection gradient pulse, a phase encoding gradient pulse, a frequency encoding gradient pulse, etc. Generally, a plurality of scanning sequences may be pre-set in a magnetic resonance system so that a sequence that is compatible with clinical detection requirements may be selected, and the clinical detection requirements may include, for example, imaging sites, imaging functions, etc.

[0041] In one example, the scanner 110 may include a main magnet assembly 111 , a bed 112 , a radio frequency generator 113 , a radio frequency transmission coil 114 , a gradient coil driver 115 , a gradient coil assembly 116 , a radio frequency power amplifier 119 , and a data acquisition unit 117 .

[0042] The main magnet assembly 111 generally includes an annular superconducting magnet defined in a housing, and the annular superconducting magnet is installed in an annular vacuum container. The annular superconducting magnet and its housing define a cylindrical space surrounding the object 16, such as Figure 1 The scanning cavity 118 is shown. The main magnet assembly 111 generates a constant magnetic field, namely, the B0 field, along the Z direction of the scanning cavity 118. Generally, a relatively uniform portion of the B0 field is formed in the central region of the main magnet.

[0043] The bed 112 is used to carry the object 16 and respond to the control of the controller 120 to move along the Z direction to enter and exit the above-mentioned scanning cavity 118. For example, in one embodiment, the imaging volume of the object 16 can be positioned in the central area of ​​the scanning cavity where the magnetic field strength is relatively uniform, so as to facilitate scanning and imaging of the imaging volume of the object 16.

[0044] The magnetic resonance imaging system 100 transmits a static magnetic pulse signal to the subject 16 located in the scanning cavity by using the formed B0 field, so that the precession of protons in the resonance volume in the subject 16 is ordered, and a longitudinal magnetization vector is generated.

[0045] The RF generator 113 and the RF power amplifier 119 can be used as part of the RF transmission link, wherein the RF generator 113 is used to respond to the control signal of the controller 120 to generate a RF pulse, which is usually a small RF signal with low power. The small RF signal can be amplified by the RF power amplifier 119 and then applied to the RF transmitting coil 114. In one embodiment, a signal transmission module is also included between the RF generator 113 and the RF power amplifier, which may include, for example, a RF attenuation controller, and the above-mentioned small RF signal can be attenuated by the RF attenuation controller and then amplified by the RF power amplifier. The above-mentioned RF pulse may include, for example, a RF excitation pulse. The RF transmitting coil 114 may include, for example, a body coil usually arranged along the inner ring of the main magnet, or a head coil dedicated to head imaging. The RF transmitting coil 114 can be connected to a transmit / receive (T / R) switch. By controlling the transmit / receive switch, the body coil can be switched between the transmit mode and the receive mode. In the transmit mode, the RF transmitting coil 114 is used to respond to the RF excitation pulse to transmit the RF field B1 orthogonal to the static magnetic field B0 to the object 16 to excite the nuclei in the body of the object 16, so that the longitudinal magnetization vector is converted into a transverse magnetization vector. In the receive mode, the body coil can be used to receive magnetic resonance signals from the object 16.

[0046] When the radio frequency excitation pulse ends, a free induction decay signal is generated in the process that the transverse magnetization vector of the object 16 gradually returns to zero, that is, a magnetic resonance signal that can be collected.

[0047] The gradient coil driver 115 is used to respond to a gradient pulse control signal or a shim control signal sent by the controller 120 to provide appropriate current / power to the gradient coil assembly 116 .

[0048] The gradient coil assembly 116 forms a changing magnetic field in the imaging space to provide three-dimensional position information for the magnetic resonance signal, and is used to generate a compensation magnetic field for the B0 field to shim the B0 field.

[0049] The gradient coil assembly 116 may include three gradient coils, and the three gradient coils are used to generate magnetic field gradients tilted to three spatial axes (e.g., X-axis, Y-axis, and Z-axis) that are perpendicular to each other. More specifically, the gradient coil assembly 116 applies a magnetic field gradient in a slice selection direction (e.g., Z-direction) to select a layer in the imaging volume. It is understood by those skilled in the art that the layer is any one of a plurality of two-dimensional slices distributed along the Z-direction in the three-dimensional imaging volume, and the above-mentioned "Z-direction" is usually a direction that can extend from the head to the feet when the patient is positioned on the bed 112. When the imaging is scanned, the radio frequency transmission coil 114 transmits a radio frequency excitation pulse to the layer of the imaging volume and excites the layer. The gradient coil assembly 116 applies a magnetic field gradient in a phase encoding direction (e.g., Y-direction) to phase encode the magnetic resonance signal of the excited layer. The gradient coil assembly 116 applies a gradient field in a frequency encoding direction (e.g., X-direction) of the object 16 to frequency encode the magnetic resonance signal of the excited layer.

[0050] The data acquisition unit 117 is used to respond to the data acquisition control signal of the controller 120 to acquire the above-mentioned magnetic resonance signal (for example, received by the body coil or the surface coil). In one embodiment, the data acquisition unit 117 may include, for example, a radio frequency preamplifier, a phase detector and an analog / digital converter, wherein the radio frequency preamplifier is used to amplify the magnetic resonance signal, the phase detector is used to perform phase detection on the amplified magnetic resonance signal, and the analog / digital converter is used to convert the phase-detected magnetic resonance signal from an analog signal to a digital signal.

[0051] The magnetic resonance imaging system 100 includes an image reconstruction unit 130, which can reconstruct a series of two-dimensional slice images of the imaging volume of the object 16, that is, the above-mentioned image sequence, based on the above-mentioned digitized magnetic resonance signals. Specifically, the reconstruction unit can communicate with the controller 120 to perform the above-mentioned image reconstruction.

[0052] The magnetic resonance imaging system 100 includes a processing unit 140, which can perform any required image processing on any image in the above-mentioned image sequence, such as image correction, determining display parameters of the image, etc. The above-mentioned image processing can be an improvement or adaptive adjustment made to the image in any aspect of contrast, uniformity, clarity, brightness, etc. Specifically, the processing unit 140 can perform the above-mentioned image processing based on communication with the controller 120.

[0053] In one embodiment, the controller 120, the image reconstruction unit 130, and the processing unit 140 may include a computer and a storage medium, respectively or in common, on which a predetermined control program and a data processing program to be executed by the computer are recorded. For example, the storage medium may store programs for implementing imaging scanning, image reconstruction, image processing, etc. For example, the storage medium may store programs for implementing the image display method of the embodiment of the present invention. The above-mentioned storage medium may include, for example, a ROM, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, or a non-volatile memory card.

[0054] The magnetic resonance imaging system 100 may include a display unit 150, which may be used to display an operation interface and various data or images generated during data processing. On the one hand, the display unit 150 may display the above-mentioned sequence of images in a certain arrangement through the display unit 150 by responding to a display control signal of the controller 120 (the display control signal may be generated by responding to an operation from a doctor requesting to read an image), for example, the sequence of images may be arranged in the order of slice positions. On the other hand, the display unit 150 may also communicate with the processing unit 140 (for example, through the controller 120) to display the above-mentioned sequence of images according to display parameters determined by the processing unit 140.

[0055] The magnetic resonance imaging system 100 also includes a console 160, which may include user input devices, such as a keyboard and a mouse, etc. The controller 120 can respond to control commands generated by the user based on operating the console 160 or an operating panel / button set on the main magnet housing, to communicate with the scanner 110, the image reconstruction unit, the processing unit 140, the display unit 150, etc.

[0056] For the transmission link, it is usually hoped that there is a stable gain between the RF power output by the RF power amplifier and the RF power generated by the front end (for example, the RF power generated by the RF generator and the RF input power of the RF power amplifier) ​​to ensure the fidelity of the RF signal transmission and avoid corresponding image problems.

[0057] The RF power amplifier usually provides the operating voltage through the power supply. Specifically, the operating voltage is generated by storing electrical energy through the capacitor component (Capacitor Bank) and charging the power supply. In the scheme of the present invention, it is found through experiments that when the signal strength of the transmitted RF pulse is large, the operating voltage provided to the RF power amplifier by the power supply will decrease. Analysis shows that this is because when the RF energy is large, the current absorbed is large, resulting in a decrease in the operating voltage of the RF power amplifier. When the operating voltage decreases, the gain of the RF power amplifier will also decrease. Figure 2 A schematic diagram showing a change in RF gain caused by a change in the operating voltage of an RF power amplifier in an example is shown.

[0058] The decrease in RF gain results in: when the RF input power remains unchanged, the RF output power decreases, which is reflected in the decrease in the amplitude of the output RF pulse waveform, for example Figure 3 The waveform shown changes, which in turn affects the fidelity of RF signal transmission.

[0059] In the embodiments of the present invention, the nonlinear transmission problem of such RF signals can be solved by gain compensation. One of the gain compensation methods is closed-loop gain compensation, for example, the RF output signal at the output end is fed back to the RF transmission link to adjust the control parameters in the link to perform gain compensation. However, the closed-loop gain needs to be limited to a smaller range. For a larger gain drop caused by a larger drop in the operating voltage, such compensation is far from enough, unless a large cost is spent to increase the capacity of the capacitor component. Or increasing the loop compensation gain, which results in a reduction in the envelope bandwidth and oscillation of the RF signal. An example of such oscillation is as follows: Figure 4 As shown, such oscillations seriously affect the stability and fidelity of RF signal transmission.

[0060] Figure 5 FIG. 4 shows a module diagram of a radio frequency power control device according to an embodiment of the present invention. Figure 5 As shown, the radio frequency power control device includes a power control module 51 , a voltage detection module 53 and a voltage adjustment module 55 .

[0061] The power control module 51 is used to receive a control voltage to control the output power of the RF power amplifier 501 of the magnetic resonance imaging system. As described above, the RF power amplifier is usually arranged in the RF transmission link of the magnetic resonance imaging system, and is used to amplify the low-power RF signal generated by the front end of the link to output a high-power RF signal capable of exciting the RF transmission coil. When the RF input signal is consistent, the RF gain of the RF transmission link determines the RF output power of the RF power amplifier.

[0062] The RF power amplifier 501 can provide an operating voltage via a voltage source 502 . Specifically, the voltage source 502 is charged through a capacitor bank 503 . The charged voltage source 502 provides an operating voltage, such as a DC 165V voltage, to the RF power amplifier 501 .

[0063] The voltage detection module 53 is used to detect the working voltage provided to the RF power amplifier 501 and output the detection voltage. For example, the voltage detection module 53 receives the actual working voltage from the voltage input terminal of the RF power amplifier 501, and outputs the detected working voltage as the detection voltage to the voltage conversion module 55. In one case, when the intensity of the RF signal transmitted to the RF power amplifier 501 is too large so that more current is absorbed by the RF power amplifier 501, the working voltage of the RF power amplifier decreases, for example, from 165V to 150V, and the detection voltage output by the voltage detection module 53 is 150V.

[0064] Those skilled in the art will appreciate that some magnetic resonance imaging systems may be provided with a voltage detection alarm module, which is used to detect the operating voltage of the RF power amplifier and send an alarm signal when the operating voltage is abnormal. In the embodiment of the present invention, the operating voltage detected by the voltage detection alarm module can be directly input into the voltage adjustment module 55 through an electrical connection line. In this way, excessive waste of wiring resources is avoided. Of course, additional circuit modules can also be provided based on design requirements to detect the operating voltage, and the detected operating voltage can be input into the voltage adjustment module 55.

[0065] The voltage adjustment module 55 is used to adjust the control voltage received by the power control module 51 based on the detection voltage, so as to adjust the output power of the RF power amplifier 501 .

[0066] On the one hand, the voltage adjustment module 55 is used to convert the detection voltage and further adjust the converted voltage to be within the linear working range of the power control module 51. For example, the power control module 51 has a characteristic curve, which represents the change characteristics of the gain of the power control module 51 with the control voltage it receives, and the characteristic curve has a nonlinear working range and a linear working range. In the linear working range, the gain changes linearly with the control voltage.

[0067] For example, if the linear operating voltage of the power control module 51 ranges from -1V to 1V, the detection voltage (eg, the above-mentioned 165V or 150V voltage) is converted to a voltage between -1V and 1V by the voltage adjustment module 55 .

[0068] On the other hand, the voltage adjustment module 55 further adjusts the converted voltage to correspond to the desired operating voltage of the RF power amplifier 501. For example, when the gain of the RF transmission link is at an ideal value or an expected value, the operating voltage of the RF power amplifier 501 is 165V, and the 165V voltage is considered to be the desired operating voltage, and the corresponding control voltage is 0.5V. When the operating voltage of the RF power amplifier 501 drops to 150V, the control voltage is 0.2V. At this time, the voltage adjustment module 55 can adjust the control voltage of 0.2V to 0.5V.

[0069] In one embodiment, the power control module 51 includes a radio frequency power attenuator. It is understood by those skilled in the art that the radio frequency power attenuator can be used to pre-amplify (attenuate) the radio frequency signal of the excitation stage to pre-adjust the radio frequency power signal so that it meets the requirements of the input power of the lower stage, for example, the input power requirements of the radio frequency power amplifier, so as to ensure that the radio frequency power amplifier outputs the desired radio frequency power (or rated power). Specifically, the power control module 51 is used to receive a first radio frequency power signal RF1, and based on the control voltage, attenuate the first radio frequency power signal to output a second radio frequency power signal RF2. In one example, the first radio frequency power signal can be generated by a radio frequency generator in a radio frequency transmission link, and the frequency of the first radio frequency power signal can be the center frequency of magnetic resonance imaging. When different control voltages are input to the power control module 51, the power control module 51 has different attenuation coefficients (or gains) to attenuate the first radio frequency power signal to different degrees, so that the output second radio frequency power signal has different powers.

[0070] The RF power amplifier 501 has an RF input terminal and an RF output terminal. The RF input terminal of the RF power amplifier 501 is used to receive the second RF power signal RF2 output by the power control module 51, and amplify the second RF power signal so that the RF output terminal outputs an amplified RF power signal RF3 to excite the RF transmitting coil.

[0071] Therefore, when the first RF power signal remains unchanged, the embodiment of the present invention can control the power of the second RF power signal by adjusting the control voltage input to the power control module, thereby adjusting the RF output power of the RF power amplifier.

[0072] Figure 6 A block diagram of a radio frequency power control device according to another embodiment of the present invention is shown. Figure 6 As shown, this embodiment and Figure 5The principles and structures of the embodiments shown are similar, except that the voltage adjustment module 65 first converts the detection voltage to a voltage close to the linear operating voltage of the power control module 51, and then further converts it into a control voltage within the linear operating range of the power control module 51 through a secondary conversion. In this way, precise voltage conversion can be achieved using a simpler circuit.

[0073] In one embodiment, the voltage adjustment module 65 includes a voltage conversion unit 651 and an adjustable voltage generating unit 652. The adjustable voltage generating unit 652 may include an adjustable voltage source, and its output voltage may be adjusted by, for example, digital control or an adjustable resistor, etc. The voltage conversion unit 651 is used to receive the adjustable reference voltage generated by the adjustable voltage generating unit 652, and convert the detection voltage into the control voltage based on the adjustable reference voltage.

[0074] Further, for example, the voltage conversion unit 651 includes a first conversion unit 6511 and a second conversion unit 6512. The first conversion unit 6511 is used to scale down the detection voltage to a first voltage. This is only for the purpose of facilitating the understanding of the present invention and is not intended to limit the present invention. An example of the ratio may be 50:1, that is, when the detection voltage is the rated voltage of 165V, the first conversion unit converts it into 3.3V, and when the detection voltage drops to 155V, the first conversion unit 651 outputs a 3V voltage.

[0075] In one embodiment, the first conversion unit 6511 may include one or more stages of proportional operational amplifiers.

[0076] The second conversion unit 6512 is used to convert the first voltage into the control voltage based on the adjustable reference voltage. For example, if the linear operating voltage of the power control module ranges from -1V to 1V, the first voltage can be converted into a control voltage between -1V and 1V by, for example, one or more subtractors.

[0077] Specifically, the second conversion unit 6512 may include a reference voltage terminal, an input terminal and an output terminal. The reference voltage terminal is used to receive the adjustable reference voltage from the adjustable voltage generating module 652, the input terminal of the second conversion unit 6512 is used to receive the first voltage, and the output terminal of the second conversion unit 6512 is used to output the control voltage after calculating the first voltage and the adjustable reference voltage.

[0078] Figure 7 A block diagram of a radio frequency power control device according to another embodiment of the present invention is shown. Figure 7As shown, in this embodiment, the power control module 51 may include a variable voltage attenuator (VVA). The VVA device is a commonly used RF controller. Within its linear operating range, its gain decreases as the control voltage decreases, and the control voltage within its linear operating range is usually a negative voltage.

[0079] The second conversion unit 6512 may include an inverting circuit and an adder circuit, wherein the inverting circuit is used to convert the first voltage output by the first conversion unit 6511 into a negative voltage, and the adder circuit is used to add the negative voltage to the adjustable reference voltage to generate the control voltage. For example, when the ideal operating voltage of the RF power amplifier is 165V, the first conversion unit 6511 converts it into a first voltage, i.e., 3.3V, and converts the first voltage into a negative voltage, i.e., -3.3V, through an inverting circuit. When the adjustable reference voltage is 2.8V, the output control voltage is -0.5V ((-3.3V) + 2.8V). When the operating voltage of the RF power amplifier drops to 150V, the first conversion unit 6511 converts it into a first voltage, i.e., 3V, and the inverting circuit converts the first voltage into a negative voltage, i.e., -3V. At this time, the control voltage is -0.2V ((-3V) + 2.8V). By changing the adjustable reference voltage, the control voltage can be adjusted. For example, by adjusting the adjustable reference voltage from 2.8V to 2.5V, the output control voltage can still be -0.5V ((-3V) + 2.5V).

[0080] Figure 8 A block diagram of a radio frequency power control device according to another embodiment of the present invention is shown. Figure 8 As shown, in this embodiment, the power control module 51 may include a variable gain amplifier (VGA). The VGA device is also a commonly used RF controller. Within its linear operating range, its gain decreases as the control voltage increases, and the control voltage within its linear operating range is usually a positive voltage.

[0081] The second conversion unit 6512 may include a subtractor circuit for subtracting the first voltage from the adjustable reference voltage to generate a control voltage. For example, when the ideal operating voltage of the RF power amplifier is 165V, the first conversion unit 6511 converts it to 3.3V, and when the adjustable reference voltage is 2.8V, the output control voltage is 0.5V (3.3V-2.8V), and when the operating voltage of the RF power amplifier drops to 150V, the first conversion unit 6511 converts it to 3V, and the control voltage at this time is 0.2V (3-2.8V). By changing the adjustable reference voltage, the control voltage can be adjusted. For example, if the adjustable reference voltage is adjusted from 2.8V to 2.5V, the output control voltage can still be 0.5V.

[0082] According to the example described above, the adjustable reference voltage is determined based on a drop value of the operating voltage of the RF power amplifier (or the voltage detected by the voltage detection module 53 ) compared to the expected operating voltage.

[0083] like Fig. 9 As shown, based on the embodiments described above, another embodiment of the present invention can also provide a radio frequency transmission system for a magnetic resonance imaging (MRI) system, which includes a radio frequency signal generator 97, a power control module 91, a radio frequency power amplifier 99 and a voltage adjustment module 95.

[0084] The RF generator 97 is used to transmit RF power signals, and its working principle is similar to Figure 1 The RF generator 113 is shown. The power control module 91 is used to receive the RF power signal and attenuate the RF power signal based on its control voltage to output the attenuated RF power signal. The working principle and working mode of the power control module 91 can be similar to the power control module 51 described in any of the above embodiments.

[0085] The RF power amplifier 99 is used to amplify the attenuated RF power signal to output a high-power RF signal. The voltage adjustment module 95 is used to adjust the control voltage received by the power control module 91 based on the change of the working voltage of the RF power amplifier 99 to adjust the high-power RF signal. The working principle and working method of the voltage adjustment module 95 can be similar to the voltage adjustment module 55 or 65 described in any of the above embodiments. In a specific embodiment, the voltage adjustment module can obtain the working voltage of the RF power amplifier in a variety of ways, including obtaining it by voltage detection.

[0086] In other embodiments, the radio frequency transmission system of the magnetic resonance imaging (MRI) system of the present invention may also include the radio frequency power control device of any of the above embodiments.

[0087] Fig.10The RF power pulse waveform obtained by adjusting the output power of the RF power amplifier using the RF power control device of the embodiment of the present invention is shown. Figure 3 As shown in the power reduction waveform, the embodiment of the present invention can accurately control the RF power amplifier to output the desired RF power.

[0088] Fig.11 shows the gain curve of the radio frequency transmission link in the existing magnetic resonance imaging system, Fig.12 The gain curve of the radio frequency transmission link obtained by using the embodiment of the present invention is shown. Fig.11 , 12 It can be seen that the gain curve obtained by the embodiment of the present invention is flatter and has significantly improved linearity.

[0089] In an embodiment of the present invention, the control voltage of the RF control module is adjusted based on the change of the working voltage of the RF power amplifier to adjust the RF power output by the RF power amplifier, and accurate gain compensation is achieved using a simple structure without causing additional problems. For example, it avoids the use of capacitor groups with higher costs and avoids RF oscillations.

[0090] Some exemplary embodiments have been described above. However, it should be understood that various modifications may be made. For example, if the described techniques are performed in a different order and / or if the components in the described systems, architectures, devices, or circuits are combined in different ways and / or replaced or supplemented by other components or their equivalents, suitable results may be achieved. Accordingly, other implementations also fall within the scope of the claims.

Claims

1. A power control device for a radio frequency power amplifier, comprising: A power control module, which is used to receive a control voltage to control the output power of the radio frequency power amplifier; a voltage detection module, which is used to detect the operating voltage provided to the RF power amplifier and output a detection voltage; and a voltage adjustment module, which is used to adjust the control voltage received by the power control module based on the detection voltage to adjust the output power of the radio frequency power amplifier, The voltage adjustment module converts the detection voltage into a linear operating range of the power control module, and adjusts the control voltage to correspond to a desired operating voltage of the RF power amplifier according to the converted detection voltage.

2. The device according to claim 1, characterized in that The voltage adjustment module includes a voltage conversion unit and an adjustable voltage generation unit. The voltage conversion unit is used to receive the adjustable reference voltage generated by the adjustable voltage generation unit and convert the detection voltage into the control voltage based on the adjustable reference voltage.

3. The device according to claim 2, characterized in that The voltage conversion unit includes a first conversion unit and a second conversion unit, the first conversion unit is used to scale down the detection voltage to a first voltage, and the second conversion unit is used to convert the first voltage into the control voltage based on the adjustable reference voltage.

4. The device according to claim 3, characterized in that The first conversion unit includes a proportional amplifier.

5. The device according to claim 3, characterized in that The second conversion unit includes a reference voltage terminal, an input terminal and an output terminal. The reference voltage terminal of the second conversion unit is used to receive the adjustable reference voltage from the adjustable voltage generating module, the input terminal of the second conversion unit is used to receive the first voltage, and the output terminal of the second conversion unit is used to output the control voltage after calculating the first voltage and the adjustable reference voltage.

6. The device according to claim 5, characterized in that The power control module includes a variable voltage attenuator, and the second conversion unit includes an inverter circuit and an adder circuit, the inverter circuit is used to convert the first voltage into a negative voltage, and the adder circuit is used to add the negative voltage to the adjustable reference voltage to generate the control voltage.

7. The device according to claim 5, characterized in that The power control module includes a voltage gain amplifier, and the second conversion circuit includes a subtractor circuit for subtracting the first voltage from the adjustable reference voltage to generate the control voltage.

8. The device according to claim 3, characterized in that The adjustable reference voltage is determined based on a drop value between an operating voltage of the radio frequency power amplifier and a desired operating voltage.

9. The device according to claim 1, characterized in that The power control module is used to receive a first RF power signal, and attenuate the first RF power signal based on the control voltage to output a second RF power signal to the RF power amplifier, and the RF power amplifier is used to amplify the second RF signal.

10. A radio frequency transmission system of a magnetic resonance imaging system, comprising the device according to any one of claims 1 to 9.

11. A radio frequency transmission system for a magnetic resonance imaging system, comprising: A radio frequency signal generator, which is used to transmit a radio frequency power signal; a power control module, configured to receive the radio frequency power signal and attenuate the radio frequency power signal based on a control voltage thereof to output an attenuated radio frequency power signal; a radio frequency power amplifier, which is used to amplify the attenuated radio frequency power signal to output a high-power radio frequency signal; and a voltage adjustment module, which is used to adjust the control voltage received by the power control module based on the change of the operating voltage of the radio frequency power amplifier, so as to adjust the high-power radio frequency signal, The voltage adjustment module converts the operating voltage of the RF power amplifier into a linear operating range of the power control module, and adjusts the control voltage to correspond to the desired operating voltage of the RF power amplifier according to the converted operating voltage.

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