阅读说明：本技术 用于磁共振成像的射频功率变换器和射频发射系统 (Radio frequency power converter and radio frequency transmission system for magnetic resonance imaging ) 是由 刘渝 王凯 邢昊洋 伍贤超 谢欣 杨栋梁 于 2019-08-30 设计创作，主要内容包括：本发明的实施例提供一种用于磁共振成像的射频功率变换器和射频发射系统。该射频功率变换器包括印刷电路板,该印刷电路板包括第一电路层、接地层以及位于第一电路层和接地层之间的一个或多个中间层,第一电路层上形成有多个并联连接的平面螺旋式电感,多个电感的一端互相连接且分别连接有第一电容的一端,多个电感的另一端分别连接有多个第二电容的一端,该多个第二电容的另一端均接地。(Embodiments of the invention provide a radio frequency power converter and a radio frequency transmit system for magnetic resonance imaging. The radio frequency power converter comprises a printed circuit board, wherein the printed circuit board comprises a first circuit layer, a grounding layer and one or more intermediate layers positioned between the first circuit layer and the grounding layer, a plurality of plane spiral inductors connected in parallel are formed on the first circuit layer, one ends of the inductors are mutually connected and are respectively connected with one ends of first capacitors, the other ends of the inductors are respectively connected with one ends of a plurality of second capacitors, and the other ends of the second capacitors are all grounded.)

1. The utility model provides a radio frequency power converter for magnetic resonance imaging, includes printed circuit board, printed circuit board includes first circuit layer, ground plane and is located one or more intermediate levels between first circuit layer and the ground plane, be formed with the spiral inductance in a plurality of parallel connection's plane on the first circuit layer, the one end interconnect of a plurality of inductances just is connected with the one end of first electric capacity respectively, the other end of a plurality of inductances is connected with the one end of a plurality of second electric capacities respectively, the other end of a plurality of second electric capacities all grounds.

2. The radio frequency power converter of claim 1, wherein the first circuit layer is a top layer circuit board of the printed circuit board.

3. The radio frequency power converter of claim 1, wherein the first capacitance and a plurality of second capacitances are disposed on one of the one or more intermediate layers.

4. The rf power converter of claim 1, wherein the intermediate layer in which the first capacitor and the plurality of second capacitors are located and the ground layer are adjacent line layers.

5. The radio frequency power converter of claim 4, wherein the first and second plurality of capacitors are each a patch capacitor formed on the intermediate layer.

6. The RF power converter of claim 5, wherein the plurality of inductors are connected to the first capacitor or the plurality of second capacitors, respectively, by first vias disposed on the printed circuit board, and wherein the first capacitor and the plurality of second capacitors are connected to the ground plane by second vias disposed on the printed circuit board, respectively.

7. The rf power converter of claim 1, wherein the first and second capacitors are each a standard capacitor soldered to the first circuit layer.

8. The radio frequency power converter of claim 1, wherein each planar spiral inductor is generally square in shape with a side of less than 5 cm.

9. The RF power converter according to any one of claims 1-8, wherein the RF power converter is an RF power divider, wherein one end of the plurality of inductors connected to the first capacitor is configured to receive a power signal to be divided, and one end of the plurality of inductors respectively connected to the plurality of second capacitors is configured to output a plurality of power division signals obtained by dividing the received power signal to be divided.

10. The RF power converter according to any one of claims 1 to 8, wherein the RF power converter is an RF power combiner, wherein one end of each of the plurality of inductors connected to the plurality of second capacitors is configured to receive a power signal to be combined, and one end of each of the plurality of inductors connected to the first capacitor is configured to output a power combined signal obtained by combining the plurality of power signals to be combined.

11. A radio frequency transmit system for magnetic resonance imaging, comprising:

a radio frequency generator for outputting a radio frequency power signal;

the driving amplifier is used for carrying out primary amplification on the radio frequency power signal;

the rf power divider of claim 9, wherein one end of the plurality of inductors connected to the first capacitor is configured to receive a primary amplified rf power signal from the driver amplifier, and one end of the plurality of inductors respectively connected to the plurality of second capacitors is configured to output a plurality of power division signals obtained by dividing the primary amplified rf power signal;

a plurality of final-stage amplifiers for amplifying the plurality of power division signals, respectively;

the rf power combiner of claim 10, wherein one end of each of the plurality of inductors connected to the plurality of second capacitors is configured to receive the power division signals amplified by the plurality of final amplifiers, and one end of each of the plurality of inductors connected to the first capacitor is configured to output a power combination signal, and the power combination signal is a power combination signal obtained by combining the plurality of amplified power division signals.

12. The radio frequency transmission system according to claim 11, further comprising a secondary radio frequency power combiner, which includes the radio frequency power combiner according to claim 10, wherein ends of a plurality of inductors of the secondary radio frequency power combiner, which are respectively connected to the plurality of second capacitors, are used for respectively receiving the plurality of power combined signals output by the plurality of radio frequency power combiners, ends of the plurality of inductors of the secondary radio frequency power combiner, which are connected to the first capacitor, are used for outputting a secondary power combined signal, and the secondary power signal is a secondary power combined signal obtained by combining the plurality of power combined signals.

13. The rf power converter of claim 11, wherein an output impedance of the rf power splitter is equal to an input impedance of a corresponding final amplifier, and an input impedance of the rf power combiner is equal to an output impedance of each final amplifier.

14. The rf power converter of claim 11, wherein the output impedance of the rf power splitter and the input impedance of the rf power combiner are each less than 10 ohms.

15. The rf power converter of claim 12, wherein each planar spiral inductor in the rf power divider and the rf power combiner is generally square in shape with a side of less than 4 cm.

Technical Field

The disclosed embodiments relate to medical imaging technology, and more particularly to a radio frequency power converter and a radio frequency transmit system for magnetic resonance imaging.

Background

MRI systems are widely used in medical diagnostics and mainly include a main magnet, a gradient amplifier, a gradient coil assembly, a radio frequency transmit chain module, a radio frequency coil assembly, a radio frequency receive chain module, and the like. The radio frequency transmission chain module generally includes a radio frequency generator for generating a radio frequency power signal and a radio frequency amplifier for amplifying the radio frequency power signal generated by the radio frequency generator, and the amplified radio frequency power signal is processed and transmitted to the radio frequency coil assembly. The radio frequency coil assembly may include a body coil as shown in fig. 104, but may also be a local transmit coil that is responsive to the amplified radio frequency power signal to transmit radio frequency excitation pulses to an object to be scanned, such as a patient.

Because of the limitations of the characteristics and performance of the amplifier device, the power required for exciting the rf transmitting coil cannot be achieved by simply using the amplifier, so the rf power divider is usually used to provide the rf input signals required by the multiple amplifier units, and the rf power combiner can be used at the output part to combine the rf output signals of the amplifier units and provide the combined rf output signals to the rf transmitting coil and its front-end circuit.

In general, in radio frequency high frequency applications such as the communication field, a conventional WilkinSon-type power divider or combiner is used, which includes multiple transmission lines (e.g., coaxial transmission lines, microstrip lines or striplines) each having a length of about one-fourth of its wavelength, and this requires very long transmission lines for implementation for lower frequency applications such as magnetic resonance imaging, which presents a great challenge for space saving and miniaturization.

In order to overcome the size limitation, the prior art also proposes to adopt a Lumped WilkinSon power divider or combiner, which uses Lumped capacitance and inductance elements to form an equivalent circuit of the traditional WilkinSon, because the capacitance and inductance required by the Lumped WilkinSon power divider or combiner in magnetic resonance imaging need to have specific values, while the standard Lumped capacitance and inductance currently sold in the market cannot be generally applied in magnetic resonance imaging, and even each inductance needs to be made manually in the production process of the magnetic resonance imaging device, which not only needs to add an additional material purchasing process, causes waste of manpower and time cost, but also causes the problem of inconsistent performance parameters due to manual fabrication, and thus needs to waste a great deal of energy for debugging.

The prior art also proposes that a magnetic core is sleeved on a shorter transmission line to be equivalent to a longer transmission line of a traditional Wilkinson device, and the mode can realize a compact and small device structure, but the transmission efficiency is greatly reduced due to the serious heating problem caused by the loss of the magnetic core.

Therefore, there is a need to provide a new radio frequency power converter for magnetic resonance imaging that solves at least one of the above mentioned problems.

Disclosure of Invention

One embodiment of the invention provides a radio frequency power converter for magnetic resonance imaging, which comprises a printed circuit board, wherein the printed circuit board comprises a first circuit layer, a ground layer and one or more intermediate layers positioned between the first circuit layer and the ground layer, a plurality of plane spiral inductors connected in parallel are formed on the first circuit layer, one ends of the inductors are connected with each other and are respectively connected with one end of a first capacitor, the other ends of the inductors are respectively connected with one ends of a plurality of second capacitors, and the other ends of the second capacitors are all grounded.

Optionally, the first circuit layer is a top circuit board of the printed circuit board.

Optionally, the first capacitance and the plurality of second capacitances are disposed on one of the one or more intermediate layers.

Optionally, an intermediate layer where the first capacitor and the plurality of second capacitors are located and the ground layer are adjacent circuit layers.

Optionally, the first capacitor and the plurality of second capacitors are patch capacitors formed on the intermediate layer, respectively.

Optionally, the first capacitor and the second capacitor form a fan-shaped structure with a fan angle of 110 degrees to 140 degrees respectively.

Optionally, the plurality of inductors and the first capacitor or the plurality of second inductors are connected through a first via hole disposed on the printed circuit board, and the first capacitor and the plurality of capacitors are connected to the ground layer through a second via hole disposed on the printed circuit board.

Optionally, the first capacitor and the plurality of second capacitors are standard capacitors soldered on the first circuit layer, respectively.

Optionally, each planar spiral inductor is in a square shape as a whole, and the side length of the square shape is less than 5 cm.

Optionally, the radio frequency power converter is a radio frequency power divider, wherein one end of the plurality of inductors connected to the first capacitor is configured to receive a power signal to be divided, and one end of the plurality of inductors respectively connected to the plurality of second capacitors is configured to output a plurality of power division signals obtained by dividing the received power signal to be divided.

Optionally, the radio frequency power converter is a radio frequency power combiner, wherein one end of each of the plurality of inductors, which is connected to the plurality of second capacitors, is used to receive a power signal to be combined, and one end of each of the plurality of inductors, which is connected to the first capacitor, is used to output a power combined signal obtained by combining the plurality of power signals to be combined.

Another embodiment of the present invention also provides a radio frequency transmit system for magnetic resonance imaging, comprising:

a radio frequency generator for outputting a radio frequency power signal;

the driving amplifier is used for carrying out primary amplification on the radio frequency power signal;

in the radio frequency power divider, one end of each of the plurality of inductors, which is connected to the first capacitor, is configured to receive a radio frequency power signal after primary amplification from the driver amplifier, and one end of each of the plurality of inductors, which is connected to the plurality of second capacitors, is configured to output a plurality of power distribution signals obtained by distributing the radio frequency power signal after primary amplification;

a plurality of final-stage amplifiers for amplifying the plurality of power division signals, respectively;

in the primary rf power combiner, one end of each of the plurality of inductors, which is connected to the plurality of second capacitors, is configured to receive the power distribution signals amplified by the plurality of final amplifiers, and one end of each of the plurality of inductors, which is connected to the first capacitor, is configured to output a power combination signal, where the power combination signal is a power combination signal obtained by combining the plurality of amplified power distribution signals.

Optionally, the radio frequency power combiner further includes a secondary radio frequency power combiner, which includes the radio frequency power combiner of claim 11, wherein ends of the plurality of inductors in the secondary radio frequency power combiner, which are respectively connected to the plurality of second capacitors, are used to respectively receive the plurality of power combined signals output by the plurality of radio frequency power combiners, ends of the plurality of inductors in the secondary radio frequency power combiner, which are connected to the first capacitor, are used to output a secondary power combined signal, and the secondary power signal is a secondary power combined signal obtained by combining the plurality of power combined signals.

Optionally, the output impedance of the rf power splitter is equal to the input impedance of the corresponding final stage amplifier, and the input impedance of the rf power combiner is equal to the output impedance of each final stage amplifier.

Optionally, the output impedance of the rf power splitter and the input impedance of the rf power combiner are both less than 10 ohms.

Optionally, each planar spiral inductor in the rf power divider and the rf power combiner is generally square, and a side of the square is less than 4 cm.

Drawings

The invention will be better understood by reading the following description of non-limiting embodiments, with reference to the attached drawings, in which:

fig. 1 shows a cross-sectional view of a radio frequency power converter of a first embodiment of the present invention;

fig. 2 shows a schematic diagram of the structure of a radio frequency power converter of a first embodiment of the present invention;

FIG. 3 shows an equivalent circuit of the radio frequency power converter shown in FIG. 2;

fig. 4-7 show performance test curves for a radio frequency power combiner with two-way signals according to a first embodiment;

fig. 8 shows a schematic diagram of the structure of a radio frequency power converter of a second embodiment of the present invention;

FIGS. 9-12 show performance test curves for a radio frequency power combiner with two-way signals according to a second embodiment;

figure 13 shows an exemplary block diagram of a radio frequency power combiner and radio frequency power divider of a third embodiment of the present invention applied in a radio frequency transmit chain of magnetic resonance imaging;

figure 14 diagrammatically shows a magnetic resonance imaging system;

figure 15 shows a block diagram of one embodiment of a radio frequency transmit system that may be used in the magnetic resonance imaging system described above;

figure 16 shows a block diagram of another embodiment of a radio frequency transmit system that may be used in the magnetic resonance imaging system described above.

Detailed Description

While specific embodiments of the invention will be described below, it should be noted that in the course of the detailed description of these embodiments, in order to provide a concise and concise description, all features of an actual implementation may not be described in detail. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions are made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.

Unless otherwise defined, technical or scientific terms used in the claims and the specification should have the ordinary meaning as understood by those of ordinary skill in the art to which the invention belongs. The use of "first," "second," and similar terms in the description and claims of the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The terms "a" or "an," and the like, do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprise" or "comprises", and the like, means that the element or item listed before "comprises" or "comprising" covers the element or item listed after "comprising" or "comprises" and its equivalent, and does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, nor are they restricted to direct or indirect connections.

First embodiment

A first embodiment of the invention provides a radio frequency power converter for magnetic resonance imaging that can be used to distribute or combine radio frequency power. Fig. 1 shows a cross-sectional view of a radio frequency power converter of a first embodiment of the invention, which, as shown in fig. 1, includes a printed circuit board 10, the printed circuit board 10 including a first circuit layer 102, a ground layer 106, and a plurality of intermediate layers 104 between the first circuit layer 102 and the ground layer 106.

The first circuit layer 102, the intermediate layer 104 and the ground layer 106 are all wiring layers, and as an embodiment, the printed circuit board 10 may include 6 wiring layers, 4 intermediate layers 104 are disposed between the first circuit layer 102 and the ground layer 106, a dielectric layer 107 is disposed between adjacent wiring layers, and the dielectric layer 107 may be made of a board material such as epoxy resin, teflon, or the like, and is preferably made of a RogerS (RogerS) board material. In other embodiments, the number of line layers or the layer thickness of the dielectric layer 107 may be increased or decreased based on desired device dimensions, performance parameters, and the like. The line layers may be a conductive metal layer, which may be copper, disposed on the dielectric layer by, for example, deposition. Electronic circuits, such as capacitors, inductors, and the like, described below, may be formed on the conductive metal layer by methods such as etching.

Fig. 2 shows a schematic diagram of a structure of a radio frequency power converter according to a first embodiment of the present invention. As shown in fig. 2, the first circuit layer 102 is formed with a plurality of planar spiral inductors L1 connected in parallel, and the number of the inductors L1 may be determined based on the number of required branches of the power divider or the combiner. Although fig. 2 illustrates an example of forming a two-way power converter with two-way shunt inductances, it should be understood that more multiple ways of shunt inductances can be formed on the printed circuit board 10.

In one example, the first circuit layer 102 is a top circuit board of the printed circuit board 10, and the planar spiral inductor L1 is formed on the top circuit board, so that the planar spiral inductor L1 has a sufficient distance from the ground layer 106, and thus the size of the planar spiral inductor L1 can be sufficiently small while obtaining the required inductance, so that the power converter has a sufficiently compact structure.

In one embodiment, the planar spiral inductor L1 is formed by forming a planar metal strip having a width in a spiral shape on the first circuit layer 102. Each planar spiral inductor L1 is a square shape as a whole, and the side length of the square shape may be less than 5cm (e.g., 3-5 cm). The planar spiral inductor L1 has an end 1022 located inside and an end 1023 located outside thereof, respectively, and the two ends 1022, 1023 of the planar spiral inductor L1 are used for electrical connection with other circuit components, respectively, as will be described in detail below.

In the present embodiment, at least one of the intermediate layers 104 is formed with a first capacitor C1 and a plurality of second capacitors C2, specifically, each first capacitor C1 and each second capacitor C2 are respectively a patch capacitor formed on the intermediate layer 104, and specifically, may be a conductive metal sheet formed on the intermediate layer 14.

Further, the intermediate layer 104 where the first capacitor C1 and the plurality of second capacitors C2 are located may be a wiring layer adjacent to the ground layer 106 as a second circuit layer. In this way, the first capacitor and the second capacitor C2 are located at a suitable distance from the ground plane 106, so that the capacitor can be made small enough while obtaining a suitable capacitance, which facilitates a more compact power converter.

The first capacitor C1 may include a plurality of capacitors having a smaller capacitance, or may include a capacitor having a larger capacitance. May be based on wiring, size, performance, etc. requirements. For example, the power converter shown in fig. 2 includes two first capacitors C1, and the two first capacitors C1 are symmetrically arranged to facilitate wiring and ensure the operating efficiency of the power converter, and in other embodiments, only one first capacitor with a larger size may be designed to replace the two first capacitors C1.

Each of the first capacitors C1 and each of the second capacitors C2 is a fan-shaped structure formed on one of the intermediate layers 104. The circle center position of the sector shape is used as a connecting node of the capacitor, so that more power loss caused by overlarge node range can be avoided. As an example, the angle of the fan-shaped structure can be between 110 degrees and 140 degrees, and the radius can be between 15 mm and 25 mm.

One end 1023 of the plurality of inductors L1 is connected to each other and to one end of the first capacitor C1, the other end 1022 of the plurality of inductors L1 is connected to one end of the plurality of second capacitors C2, and the other ends of the plurality of second capacitors C2 are all grounded.

A first via (e.g., via 103 in fig. 1) may be disposed between the first circuit layer 102 and an intermediate layer (e.g., a second circuit layer) 104 formed with a first capacitance C1 and a second capacitance C2; a second via (e.g., via 105 in fig. 1) may be disposed between the ground plane 106 and the intermediate layer 104 formed with the first capacitor C1 and the second capacitor C2. The via holes are used for realizing signal communication among different circuit layers. For example, the ends 1022 of the two inductors L1 shown in fig. 2 are connected to each other and then connected to the first capacitor C1 through a first via; the end 1023 of each inductor L1 is connected to a corresponding second capacitor C2 by a first via; each of the first and second capacitors C1 and C2 may be connected to the ground plane 106 through a corresponding second via.

Fig. 3 shows an equivalent circuit of the rf power converter shown in fig. 2, and according to the above description, the present embodiment forms the rf power converter with the circuit structure shown in fig. 3 by designing the planar spiral inductor and the patch capacitor on the printed circuit board and electrically connecting them. The problem that standard inductance and capacitance elements are difficult to configure in the prior art is solved, the challenge of size design brought by adopting a transmission line type converter is overcome, a compact device structure is realized, and the problem of low efficiency brought by adopting a magnetic core type transmission line converter is also avoided.

As shown in fig. 3, when the rf power converter is used as a power divider, one end (i.e., port 1) of the two inductors L1 connected to the first capacitor C1 is used as an input end for receiving a power signal to be divided, and one ends (i.e., ports 2 and 3) of the two inductors L1 connected to the two second capacitors C2 are used for outputting a plurality of power division signals obtained by dividing the power signal to be divided.

When the radio frequency power converter is used as a power synthesizer, the ports 2 and 3 are used as input ends and are respectively used for receiving power signals to be synthesized, and the port 1 is used as an output end and is used for outputting a power synthesis signal obtained by synthesizing the multipath power signals to be synthesized.

In the embodiment, the planar spiral inductor and the standard capacitor are formed on the printed circuit board and are electrically connected to form the rf power converter having the circuit structure shown in fig. 3.

Fig. 4 to 7 show performance test curves of the radio frequency power combiner with two-way signals according to the first embodiment. In the graph shown in fig. 4, the horizontal axis represents frequency, and the vertical axis represents gain of two signals, as can be seen from fig. 4, at the center frequency (about 64MHz) of the magnetic resonance imaging, the gains of the two signals of the radio frequency power synthesizer are both 3.100dB, compared with the ideal gain (3.033dB), there is only a gain loss of 0.067, and the two curves of the gain loss of the output end relative to the two input ends respectively coincide, which indicates that the two signals have better consistency, i.e. better equal-amplitude and same-phase characteristics.

Fig. 5 shows the return loss (signal reflection) of the output (1, 1) and the two inputs (2, 2), (3, 3) of the rf power combiner, and it can be seen from fig. 5 that the return loss of the three ports is sufficiently small.

Fig. 6 shows a phase curve of the rf power combiner, wherein the horizontal axis represents frequency and the vertical axis represents phase, and as can be seen from fig. 6, the phase curves corresponding to the two signals are overlapped, which shows that the rf power combiner has better phase consistency.

Fig. 7 shows the isolation performance of the two signals of the rf power combiner, wherein the horizontal axis represents frequency, and the vertical axis represents the interference characteristics of the two signals, as can be seen from fig. 7, the interference signals of the two signals are small, and therefore, the rf power combiner has good electrical isolation characteristics.

Second embodiment

The radio frequency power converter for magnetic resonance imaging according to the second embodiment of the present invention, similar to the first embodiment, includes a printed circuit board 10, the printed circuit board 10 including a first circuit layer 102, a ground layer 106, and a plurality of intermediate layers 104 between the first circuit layer 102 and the ground layer 106.

The first circuit layer 102, the plurality of intermediate layers 104 and the ground layer 106 are all circuit layers, and a dielectric layer is disposed between adjacent circuit layers, and the dielectric layer may be made of a board material such as epoxy resin, teflon, RogerS (RogerS), and the like. In other embodiments, the number of line layers or the layer thickness of the dielectric layer may be increased or decreased based on desired device dimensions, performance parameters, and the like. The line layers may be a conductive metal layer, which may be copper, disposed on the dielectric layer by, for example, deposition. An inductive element, for example, may be formed on the conductive metal layer by a method such as etching.

Fig. 8 shows a schematic diagram of a structure of a radio frequency power converter according to a second embodiment of the present invention. As shown in fig. 8, the first circuit layer 102 is formed with a plurality of planar spiral inductors L1 connected in parallel, and the number of the inductors L1 may be determined based on the number of required branches of the power divider or the combiner. Although fig. 4 illustrates an example of forming a two-way power converter with two-way shunt inductances, it should be understood that more multiple ways of shunt inductances can be formed on a printed circuit board.

In one example, the printed circuit board 10 may include 6 circuit layers, and there are 4 intermediate layers 104 between the first circuit layer 102 and the ground layer 106, and the first circuit layer 102 is a top circuit board of the printed circuit board 10, and the planar spiral inductor L1 is formed on the top circuit board, and a plurality of intermediate layers are disposed between the top circuit board and the ground layer, so that there is a sufficient distance between the planar spiral inductor L1 and the ground layer 106, and thus, while obtaining the required inductance, the size of the planar spiral inductor L1 may be small enough, and the power converter has a sufficiently compact structure.

In one embodiment, the planar spiral inductor L1 is formed by forming a planar metal strip having a width in a spiral shape on the first circuit layer 102. Each planar spiral inductor L1 is in a square shape on the whole, and the side length of the square shape is 3-5 cm. The planar spiral inductor L1 has an end 1022 located inside and an end 1023 located outside thereof, respectively, and the two ends 1022, 1023 of the planar spiral inductor L1 are used for electrical connection with other circuit components, respectively, as will be described in detail below.

In this embodiment, the first circuit layer 102 is further soldered with a first capacitor 1026 and a plurality of second capacitors C4, specifically, each of the first capacitors C3 and each of the second capacitors C4 are standard capacitor elements soldered on the first circuit layer 102. The standard capacitor element may be a capacitor element manufactured according to a standard specified by a country or an organization, and has a stable capacitance value that can satisfy the requirements of a power converter in magnetic resonance imaging.

The first capacitor C3 may include a plurality of capacitors having a smaller capacitance, or may include a capacitor having a larger capacitance. May be based on wiring, size, performance, etc. requirements. For example, while the power converter shown in fig. 4 includes a first capacitor C3, in other embodiments, the first capacitor C3 may be replaced by a plurality of standard capacitor elements having a smaller capacitance connected in parallel.

One ends of the inductors (planar spiral inductors) L1 are connected to each other and to one end of the first capacitor C3, the other ends of the inductors L1 are connected to one ends of the second capacitors C4, and the other ends of the second capacitors C4 are all grounded.

Vias may be provided between the first circuit layer 102 and the ground plane 106. The vias are used to connect capacitive elements (e.g., first and second capacitors) on the first circuit layer 102 to the ground plane 106. On the first circuit layer 102, the connection between the inductor and the standard capacitor element can be electrically connected by a lead and a pad formed on the first circuit layer 102.

The equivalent circuit of the rf power converter according to the second embodiment of the present invention is the same as the circuit shown in fig. 3, and according to the above description, the present embodiment forms the rf power converter having the circuit structure shown in fig. 3 by forming the planar spiral inductor and the standard capacitor on the printed circuit board and electrically connecting them. The problem that a standard inductance element is difficult to configure in the prior art is solved, the challenge of size design brought by adopting a transmission line type converter is overcome, a compact device structure is realized, and the problem of low efficiency brought by adopting a magnetic core type transmission line converter is also avoided. Furthermore, by combining the planar inductance element and the standard capacitance element, a balance between performance stability and processing difficulty is achieved.

Figures 9-12 show performance test curves for a radio frequency power combiner with two-way signals according to a second embodiment. In the graph shown in fig. 9, the horizontal axis represents frequency, and the vertical axis represents gain of the two-way signal, and it can be seen from fig. 9 that at the center frequency of magnetic resonance imaging (about 64MHz), the gains of the two-way signal of the rf power synthesizer are both 3.159dB, which is very close to ideal gain (3.033dB), and therefore, the gain loss is small. And the two curves of the gain loss of the output end relative to the two input ends are superposed, which shows that the two paths of signals have better consistency, namely better equal-amplitude and same-phase characteristics.

Fig. 10 shows the return loss (signal reflection) of the output (1, 1) and the two inputs (2, 2), (3, 3) of the rf power combiner, and it can be seen from fig. 10 that the return loss of the three ports is sufficiently small.

Fig. 11 shows a phase curve of the rf power combiner, wherein the horizontal axis represents frequency and the vertical axis represents phase, and as can be seen from fig. 11, the phase curves corresponding to the two signals are overlapped, which shows that the rf power combiner has better phase consistency.

Fig. 12 shows the isolation performance of the two signals of the rf power combiner, wherein the horizontal axis represents frequency, and the vertical axis represents the interference characteristics of the two signals, as can be seen from fig. 12, the interference signals of the two signals are small, and therefore, the rf power combiner has good electrical isolation characteristics.

Third embodiment

A third embodiment of the present invention provides a radio frequency power converter for a magnetic resonance imaging system, which has a similar structure, principle, etc. to the radio frequency power converter of the first embodiment or the second embodiment, except that in the third embodiment, when the radio frequency power converter is a radio frequency power divider, its output impedance is less than 50 ohms, more specifically, less than 10 ohms; when the rf power converter is an rf power combiner, its input impedance is less than 50 ohms, more specifically less than 10 ohms.

In the conventional magnetic resonance imaging field, when testing and debugging the radio frequency transmission link, it is customary to design the input impedance and the output impedance of each device (including the radio frequency power combiner and/or the radio frequency power divider) in the link to be 50 ohms, which is convenient for testing each device separately. Taking the rf power combiner as an example, since the output impedance of the generally designed rf power amplifier is small (e.g., less than 10 ohms or even less than 5 ohms), in order to match the impedance of the rf power combiner with the rf power amplifier connected to the front end of the rf power combiner, a complex impedance matching network is required to transform the output impedance of the rf power amplifier to 50 ohms. Similarly, such a matching network is also required between the rf power amplifier and the rf power splitter.

In this embodiment, unlike a conventional rf power combiner or rf power divider, the input impedance and the output impedance of the rf power converter are small enough to directly implement impedance matching with an rf power amplifier for magnetic resonance imaging, without providing an impedance matching network between the rf power amplifier and the rf power converter, or with only a very simple impedance matching unit (e.g., a small section of transmission line) to implement impedance matching. During testing, the radio frequency power amplifier, the radio frequency power divider and the radio frequency power combiner connected with the radio frequency power amplifier can be tested as a whole.

Fig. 13 shows an exemplary block diagram of applying the rf power combiner and the rf power divider according to the third embodiment of the present invention to the rf transmit chain of the mri, as shown in fig. 13, the input impedance of the rf power divider 131 is still 50 ohms, the output impedances of the two output terminals are respectively 6.25 ohms, and the impedance matching with the corresponding input terminal of the rf power amplifier 133 is achieved by the impedance matching unit 132 with a simple structure. The output end of each rf power amplifier 133 realizes an output impedance of 6.25 by having a simple-structure impedance matching unit 134, and the impedances of the two input ends of the rf power combiner 135 are also 6.25 ohms and are matched with the output impedance of the corresponding impedance matching unit 134; the impedance of the input terminal of the rf power splitter 131 and the impedance of the output terminal of the rf power combiner 135 are both 50 ohms, which facilitates testing the rf power splitter 131, the impedance matching unit 132, the rf power amplifier 133, the impedance matching unit 134, and the rf power combiner 135 as an integrated functional module.

In this way, the impedance matching units 132 and 134 with simple structure may be used to replace the complex network matching unit, or when the output impedance is more accurate through the rf power divider or the rf power combiner, or the input impedance is more accurate through designing the rf power combiner, the impedance matching units 132 and 134 may be eliminated, at this time, the output impedance of the rf power divider or the input impedance of the rf power combiner may be directly equal to the optimal matching impedance (for example, generally less than 10 ohms) of the rf power amplifier 133, for example, the output impedance of the rf power divider 131 is equal to the input impedance of the corresponding final stage amplifier 133, and the input impedance of the rf power combiner 135 is equal to the output impedance of each final stage amplifier 133. Therefore, the rf power converter according to the third embodiment of the present invention can make the module structure of the transmission link more compact.

Moreover, the size of the rf power converter itself can be further reduced by changing the input impedance and the output impedance, for example, when the structure shown in fig. 13 is adopted, the size of the planar spiral inductor in the rf power divider and the rf power combiner can be further reduced compared with the first embodiment and the second embodiment, for example, the side length of the inductor can be reduced to less than 4cm (e.g., 2-4 cm).

Fourth embodiment

A fourth embodiment of the invention provides a radio frequency transmission system for magnetic resonance imaging, fig. 14 exemplarily shows a magnetic resonance imaging system, and as shown in fig. 14, the Magnetic Resonance Imaging (MRI) system 140 includes a main magnet assembly, a radio frequency transmission coil 142, a radio frequency transmission system 143, a gradient coil assembly 144, a gradient coil driver 145, a radio frequency receiving system 146, a controller unit 147, a data processing unit 148, and a scan bed 149.

The main magnet assembly typically comprises, for example, a superconducting magnet 141 having main magnet coils circumferentially disposed along the superconducting magnet 1411, which is mounted within an annular vacuum vessel and defines a cylindrical imaging space surrounding the object 200 to be scanned. A constant static magnetic field, such as static magnetic field B0, is generated along the Z-direction of the imaging volume. The MRI system 140 transmits a static magnetic pulse signal to the object to be scanned 200 placed in the imaging space using the formed static magnetic field B0, so that the precession of protons in the body of the object to be scanned is ordered, producing a longitudinal magnetization vector.

The radio frequency transmission coil 142 is generally disposed along the inner ring of the main magnet and is used for transmitting a radio frequency field B1 orthogonal to the static magnetic field B0 to the object 200 to be scanned in response to radio frequency excitation pulses transmitted from the radio frequency transmission system 143 to excite nuclei in the body of the object 200 to be scanned to convert longitudinal magnetization vectors into transverse magnetization vectors.

The radio frequency transmission system 143 is operative to transmit radio frequency excitation pulses to the radio frequency transmit coil 142 in response to pulse sequence control signals issued by the controller unit 147. Specifically, the controller unit 147 may generate a pulse sequence by, for example, a pulse sequence generator, and the rf transmitting system 143 generates rf excitation pulses according to the rf pulses in the pulse sequence generated by the pulse sequence generator and processes the rf excitation pulses. The radio frequency excitation pulse is in particular a radio frequency power signal. The rf transmission system 143 will be described in detail below with reference to fig. 15.

After the radio frequency excitation pulse is ended, a free induction decay signal, i.e., a magnetic resonance signal that can be acquired, is generated in the process of gradually returning the transverse magnetization vector of the object 200 to be scanned to zero.

In one embodiment, the radio frequency transmit system 143 a transmit/receive mode switch to switch the radio frequency transmit coil 142 between a transmit mode and a receive mode, wherein in the receive mode the radio frequency transmit coil 142 may be used to receive magnetic resonance signals from the subject 200 to be scanned, which may also be acquired via the radio frequency receive coil 210 disposed proximate to the subject 200 to be scanned.

The gradient coil assembly 144 generally includes three sets of gradient coils disposed along the X-axis, Y-axis and Z-axis for respectively receiving power drive signals generated from the gradient coil drivers 145 to generate three-dimensional gradient magnetic fields in the imaging volume for three-dimensional encoding of the magnetic resonance signals, i.e., providing three-dimensional positional information of the magnetic resonance signals.

Based on the three-dimensionally encoded magnetic resonance signals, a medical image of a scanning site of the object to be scanned can be reconstructed, which will be described below.

The radio frequency receive system 146 is operative to receive magnetic resonance signals acquired by the radio frequency receive coil 210 or the radio frequency transmit coil 142 in a receive mode. Specifically, the rf receiving system 146 may include a rf preamplifier for amplifying the magnetic resonance signal received by the rf receiving coil or the rf transmitting coil, a phase detector 1062 for performing phase detection on the amplified magnetic resonance signal, and an analog/digital converter for converting the phase-detected magnetic resonance signal from an analog signal to a digital signal and sending the converted signal to the data processing unit 148.

The data processing unit 148 may perform preprocessing, reconstruction, etc. of the received digitized magnetic resonance signals to obtain the desired images or image data. The data processing unit 148 may include a computer and a storage medium on which a program of predetermined data processing to be executed by the computer is recorded. The data signal processing unit 148 may be connected to the controller unit 147 and perform data processing based on a control signal received from the controller unit 147.

The controller unit 147 may include a computer and a storage medium for storing a program executable by the computer, which when executed by the computer, may cause the respective components of the MRI system 140 to perform respective operations for performing an imaging scan of the object to be scanned 200.

Figure 15 shows a block diagram of one embodiment of a radio frequency transmit system 143 that may be used in the magnetic resonance imaging system 140 described above. As shown in fig. 15, the rf transmission system includes an rf generator 151, a driver amplifier 152, an rf power divider 153, a final amplifier 154, and a primary rf power combiner 155. For convenience of description and understanding, the rf power combiner 155 and the rf power divider 154 in fig. 15 are shown in the form of equivalent circuits, and in practice, the rf power combiner 155 and the rf power divider 154 may be the example of the first embodiment shown in fig. 1 and fig. 2, the example of the second embodiment shown in fig. 8, and the example of the third embodiment shown in fig. 13.

The rf generator 151 is configured to output an rf power signal S1, and the rf generator 151 may include a digital frequency synthesizer, a digital-to-analog converter, and the like. As previously mentioned, the radio frequency generator is used to generate a radio frequency pulse signal that is applied to the radio frequency transmit coil 142 to excite a portion to be imaged of an object to be scanned (e.g., a patient) during an MRI scan.

The driving amplifier 152 is used for primarily amplifying the rf power signal output from the rf generator 151.

The rf power divider 153 may be the rf power converter in any one of the first to third embodiments, wherein one end of each inductor L1 in the rf power divider, connected to the first capacitor (C1 or C3), is configured to receive the primary amplified rf power signal S2 from the driving amplifier 152, and one end of each inductor, connected to the corresponding second capacitor (C2 or C4), is configured to output a plurality of power division signals S3 obtained by dividing the signal S2.

Each power division signal S3 is amplified by a corresponding final amplifier 154.

The primary rf power combiner 155 is configured to combine the power distribution signal S4 amplified by each of the final amplifiers 154. The primary rf power combiner 155 may be the rf power converter in any one of the first to third embodiments, wherein one end of each inductor L1 in the primary rf power combiner 155, which is connected to the corresponding second capacitor (C2 or C4), is used to receive the power distribution signal S4 amplified by the corresponding final amplifier, and one end of each inductor L1, which is connected to the first capacitor (C1 or C3), is used to output the power combination signal S5, which is obtained by combining the amplified power distribution signals S4.

Fig. 16 shows a block diagram of another embodiment of the radio frequency transmission system 143 that can be used in the magnetic resonance imaging system 140, and as shown in fig. 16, the radio frequency transmission system further includes a secondary radio frequency power combiner 156, where the secondary radio frequency power combiner 156 may be a radio frequency power converter in any of the first to third embodiments, where one end of each inductor L1 connected to the corresponding second capacitor (C2 or C4) is used to receive a power combined signal S5 output by the primary radio frequency power combiner, one end of each inductor L1 connected to the first capacitor C1 or C3) in the secondary radio frequency power combiner is used to output a secondary power combined signal S6, and the secondary power combined signal S6 is obtained by combining the multiple power combined signals S5.

In other embodiments, the rf transmitting system 143 may further include other modules or units, such as an I/Q two-way switch bridge, for dividing the final power-combined signal into two paths to the rf transmitting coil 142.

As used herein, an element or step recited in the singular and proceeded with the word "a" or "an" should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to "one embodiment" of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments "compriSing," "including," "having" or "having" an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms "including" and "in which" are used as plain language equivalents of the respective terms "compriSing" and "characterized by". Furthermore, in the appended claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The scope of the invention is defined by the claims and may include other examples known to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.