WO2023000500A1 - Four-end-ring birdcage radio frequency coil system supporting three-nuclide imaging - Google Patents

Abstract

Embodiments of the present application disclose a four-end-ring birdcage radio frequency coil system supporting three-nuclide imaging, comprising: a first end ring, a second end ring, a third end ring and a fourth end ring which share the same center axis, at least one of the first end ring, the second end ring, the third end ring and the fourth end ring being provided with an excitation port, a plurality of first wires being connected between the first end ring and the second end ring, a plurality of second wires being connected between the second end ring and the third end ring, and a plurality of third wires being connected between the third end ring and the fourth end ring; and a double-tuned circuit electrically connected to the excitation port, and used for achieving resonant frequencies of two nuclides.

Description

Four-terminal ring birdcage RF coil system supporting triple-nuclide imaging

This disclosure claims the priority of the Chinese patent application with application number 202110837831.4 submitted to the China Patent Office on July 23, 2021, and the entire content of the above application is incorporated by reference in this disclosure.

technical field

The present application relates to nuclear magnetic resonance technology, for example, to a four-terminal ring birdcage radio frequency coil system supporting triple-nuclide imaging.

Background technique

Achieving high-quality imaging of biological endogenous weak signals faces many major technical challenges. Compared with traditional hydrogen-proton MRI (Magnetic Resonance Imaging, magnetic resonance), weak nuclides usually have lower gyromagnetic ratio and lower The spatial resolution, precise excitation of the magnetic field for biological signals at specific frequency points, and the highly sensitive detection method of magnetic resonance signals and multi-core receiving coils have become the focus of research.

Contents of the invention

The embodiment of the present application provides a four-terminal ring birdcage radio frequency coil system supporting three nuclide imaging, so as to simultaneously realize the resonant frequencies of three different nuclides, and exhibit good electromagnetic isolation performance between the mutual frequencies.

The embodiment of the present application provides a four-terminal ring birdcage radio frequency coil system supporting three-nuclide imaging, including:

A first end ring, a second end ring, a third end ring and a fourth end ring, the first end ring, the second end ring, the third end ring and the fourth end ring have a common central axis It is set that the second end ring is located between the first end ring and the third end ring, and the third end ring is located between the second end ring and the fourth end ring; the At least one of the first end ring, the second end ring, the third end ring, and the fourth end ring defines an excitation port;

A plurality of first wires, a plurality of second wires and a plurality of third wires are respectively parallel to the central axis; the plurality of first wires are connected between the first end ring and the second end ring, so The multiple second wires are connected between the second end ring and the third end ring, and the multiple third wires are connected between the third end ring and the fourth end ring;

A double tuning circuit is electrically connected to the excitation port, and the double tuning circuit is used to realize the resonant frequency of the two nuclides.

Description of drawings

Fig. 1 is a schematic diagram of a four-terminal ring birdcage radio frequency coil system supporting three-nuclide imaging provided by the embodiment of the present application;

Fig. 2 is a schematic diagram of the first end ring in Fig. 1 in the XY plane;

Fig. 3 is a schematic diagram of the second end ring in Fig. 1 in the XY plane;

Fig. 4 is the expanded schematic diagram of the birdcage radio frequency coil system in the XZ plane in Fig. 1;

Fig. 5 is the schematic diagram that another kind of birdcage radio frequency coil system that the embodiment of the application provides expands the birdcage radio frequency coil system in XZ plane;

6 is a schematic diagram of another birdcage radio frequency coil system deployed in the XZ plane of another birdcage radio frequency coil system provided by the embodiment of the present application;

7 is a circuit diagram of a double-tuned circuit in a four-terminal ring birdcage radio frequency coil system that supports three-nuclides imaging provided by an embodiment of the present application;

FIG. 8 is a schematic diagram of another four-terminal ring birdcage radio frequency coil system supporting three-nuclide imaging provided by an embodiment of the present application.

detailed description

In a multi-tuned coil system, the physical properties of ¹ H and non-proton elements are close, which will lead to strong coupling between elements and seriously reduce the sensitivity of the coil. In order to improve the signal-to-noise ratio (SNR, signal-to-noise ratio) and resolution, This results in a longer acquisition time and increases the inhomogeneity of the radio frequency (RF, Radio Frequency) field. An effective multi-core RF coil will help overcome the inhomogeneity of the RF field and the low SNR.

In order to deal with the above situation, the embodiment of the present application discloses a four-terminal ring birdcage radio frequency coil system supporting three-nuclide imaging.

The present application will be described below in conjunction with accompanying drawings 1-8 and embodiments.

The study of aproton (x-nuclear) MRI has attracted great interest in recent years, partly due to the growing popularity of ultra-high-field MRI. Among them, magnetic resonance ²³ Na, ³¹ P and other multi-nuclide imaging is an important unique imaging technology for magnetic resonance molecular imaging to non-invasively obtain life information such as tissue physiology and metabolism. Compared with protons, ²³ Na, ³¹ P and other x nuclei (eg, ¹⁹ F) imaging is challenging, and dual-resonant or multi-resonant RF coils are often used to meet this requirement.

Double tuned coils can be designed in many ways, such as using pin diode control in a single coil structure to build a double tuned circuit or a trap circuit to achieve dual frequencies, or in a traditional birdcage structure for a desired frequency of birdcage coils every other One leg or pillar is tuned to achieve dual frequencies, but this method relies on strong mutual coupling between the grids and it is difficult to maintain the symmetry of the coils.

Alternatively, a geometric structure mode in which two independent coils are combined is used to generate an orthogonal magnetic field to realize dual frequencies isolated from each other. Or, use alternately nested birdcage structures.

By constructing completely different conductor geometries to generate resonant modes at two frequencies, the dual birdcage coil for this combined structure is a combination of a smaller diameter birdcage within a larger diameter birdcage , the large birdcage is tuned to a higher resonant frequency, while the small birdcage is tuned to a lower frequency, forming a double-tuned birdcage coil. One of the strongest sources of inductive coupling between birdcage units is the proximity of the end rings. Also, misalignment of the rings at both ends can result in splitting of the linear modes at two frequencies.

Figure 1 is a schematic diagram of a four-terminal ring birdcage radio frequency coil system supporting three-nuclide imaging provided by the embodiment of the present application, Figure 2 is a schematic diagram of the first end ring in Figure 1 in the XY plane, and Figure 3 is a schematic diagram of Figure 1 The schematic diagram of the second end ring in the XY plane. Figure 4 is a schematic diagram of the expansion of the birdcage RF coil system in Figure 1 in the XZ plane. Referring to Figure 1-Figure 4, the four-terminal ring birdcage radio frequency supporting three-nuclide imaging The coil system refers to a birdcage radio frequency coil system that can support three nuclide imaging. The birdcage radio frequency coil system includes four end rings, namely the first end ring 11, the second end ring 12, and the third end ring 13 and the fourth end ring 14. The first end ring 11 , the second end ring 12 , the third end ring 13 and the fourth end ring 14 are arranged concentrically with the central axis K. The second end ring 12 is located between the first end ring 11 and the third end ring 13 , and the third end ring 13 is located between the second end ring 12 and the fourth end ring 14 . Along the extension direction of the central axis K, the first end ring 11 , the second end ring 12 , the third end ring 13 and the fourth end ring 14 are arranged in sequence. At least one of the first end ring 11 , the second end ring 12 , the third end ring 13 and the fourth end ring 14 defines an excitation port 15 . The birdcage radio frequency coil system also includes multiple first wires 21 , multiple second wires 22 and multiple third wires 23 . The first conducting wire 21 , the second conducting wire 22 and the third conducting wire 23 are all parallel to the central axis K. The first wire 21 is connected between the first end ring 11 and the second end ring 12, the second wire 22 is connected between the second end ring 12 and the third end ring 13, and the third wire 23 is connected to the third end ring 13 and the fourth end ring 14. The birdcage RF coil system also includes a double-tuning circuit 30 electrically connected to the excitation port 15, and the double-tuning circuit 30 is used to realize the resonant frequency of the two nuclides.

The embodiment of the present application provides a four-terminal ring birdcage radio frequency coil system that supports three-nuclide imaging. The structure formed by the first end ring 11, the second end ring 12 and the first wire 21 can be regarded as the first birdcage cage structure. The structure formed by the second end ring 12 , the third end ring 13 and the second wire 22 can be regarded as a second birdcage structure. The structure formed by the third end ring 13 , the fourth end ring 14 and the third wire 23 can be regarded as a third birdcage structure. Therefore, the birdcage RF coil system provided by the embodiment of the present application adds two extra end rings to a type of birdcage coil in the related art, which can be regarded as a combination of three birdcage structures. And set up double harmonic circuit 30 at excitation port 15, build the birdcage structure of double harmonic circuit 30 to realize the resonant frequency of two kinds of nuclides at the same time, except realizing the birdcage structure of the resonant frequency of two kinds of nuclides, all the other birdcage structures The resonant frequency of another nuclide can be realized, and the resonant frequency of three different nuclides can be realized at the same time, and the mutual frequency shows good electromagnetic isolation performance, and no additional lossy components such as diode switches are included.

In an embodiment, referring to FIGS. 1-4 , the birdcage RF coil system further includes multiple first capacitors 51 , multiple second capacitors 52 , multiple third capacitors 53 and multiple fourth capacitors 54 . A plurality of first capacitors 51 are connected in series in the first end ring 11, a plurality of second capacitors 52 are connected in series in the second end ring 12, a plurality of third capacitors 53 are connected in series in the third end ring 13, and a plurality of The fourth capacitor 54 is connected in series with the fourth terminal ring 14 . In the embodiment of the present application, the first capacitor 51, the second capacitor 52, the third capacitor 53, and the fourth capacitor 54 are connected in series to the first end ring 11, the second end ring 12, the third end ring 13, and the fourth end respectively. In the ring 14, the birdcage RF coil system is a high-pass configuration tuning structure, which can change the resonant frequency of the nuclide by adjusting the capacitance values of the first capacitor 51, the second capacitor 52, the third capacitor 53 and the fourth capacitor 54.

Exemplarily, referring to FIG. 1 , the end rings (such as the first end ring 11 , the second end ring 12 , the third end ring 13 and the fourth end ring 14 ) include a plurality of arc-shaped conductors 10 . With reference to Fig. 2, the gap between adjacent two arc-shaped conductors 10 is used as excitation port 15, and one end of excitation source 40 can be electrically connected with an arc-shaped conductor 10, and the other end of excitation source 40 can be adjacent to another The arc-shaped conductor 10 is electrically connected to the circular arc conductor 10, and the excitation source 40 applies an excitation signal to the end ring through the excitation port 15.

For example, referring to FIG. 2 , in the first end ring 11 , the first capacitor 51 is connected between two adjacent arc-shaped conductors 10 . Referring to FIG. 3 , in the second end ring 12 , the second capacitor 52 is connected between two adjacent arc-shaped conductors 10 . Similarly, in the third end ring 13 , the third capacitor 53 is connected between two adjacent arc-shaped conductors 10 . In the fourth end ring 14 , the fourth capacitor 54 is connected between two adjacent arc-shaped conductors 10 .

In an embodiment, referring to FIG. 1-FIG. 2 , the first end ring 11 has two excitation ports 15 (respectively marked as excitation port A and excitation port B), and there will be two corresponding double-tuning circuits 30 . The phase difference between the two excitation ports 15 in the first end ring 11 is 90°. A double tuning circuit 30 is electrically connected to an excitation port 15 in the first end ring 11 . In the embodiment of the present application, the first end ring 11 is provided with two excitation ports 15 with a phase difference of 90°, and the first end ring 11 is excited in an orthogonal excitation manner. Dual tuning circuit 30 achieves the resonant frequencies of the two nuclides.

In one embodiment, referring to FIGS. 1 and 3 , the excitation port 15 in the first end ring 11 generates the resonant frequency of the first species and the resonant frequency of the second species. The second end ring 12 has two excitation ports 15 (denoted as excitation port C and excitation port D respectively), and the phase difference between the two excitation ports 15 in the second end ring 12 is 90°. The two excitation ports 15 in the second end ring 12 generate the resonant frequency of the third species. The resonant frequency of the third nuclide is lower than the resonant frequency of the first nuclide, and the resonant frequency of the third nuclide is lower than the resonant frequency of the second nuclide. In the embodiment of the present application, the second end ring 12 is provided with two excitation ports 15 with a phase difference of 90°, and the second end ring 12 is excited by an orthogonal excitation method. On the basis that the dual harmonic circuit 30 realizes the resonant frequency of the two nuclides, the excitation port 15 in the second end ring 12 generates the resonant frequency of the third nuclide. Since the second end ring 12 (inner end ring) generating a lower frequency is placed inside the first end ring 11 (outer end ring) generating a higher frequency, the transmission efficiency is improved.

Exemplarily, the first nuclide is ¹ H, the second nuclide is ¹⁹ F, and the third nuclide is ²³ Na. A double harmonic circuit 30 is built at the excitation port of the high-pass birdcage on the outer end ring, and at the same time realizes the resonant frequencies of ¹ H and ¹⁹ F decoupled from each other. The inner end ring is also a high-pass structure, resonating at ²³ Na operating frequency. By adjusting the distance between the inner and outer end rings, the ¹ H, ¹⁹ F nuclides and ²³ Na nuclides have a good decoupling effect. Taking the application in the 3T system as an example, it can simultaneously support the precise excitation and reception of ¹ H/ ¹⁹ F/ ²³ Na/ signals. Wherein, the 3T system is a system with a magnetic field strength of 3T (T is a unit of magnetic field strength, Tesla).

Fig. 5 is the schematic diagram that another kind of birdcage radio frequency coil system that the embodiment of the application provides expands the birdcage radio frequency coil system in the XZ plane, referring to Fig. 5, the birdcage radio frequency coil system also includes a plurality of fifth capacitors 55, a plurality of A sixth capacitor 56 and a plurality of seventh capacitors 57 . A fifth capacitor 55 is connected in series with a first wire 21 , a sixth capacitor 56 is connected in series with a second wire 22 , and a seventh capacitor 57 is connected in series with a third wire 23 . In the embodiment of the present application, the fifth capacitor 55, the sixth capacitor 56, and the seventh capacitor 57 are respectively connected in series with the first wire 21, the second wire 22, and the third wire 23, and the birdcage RF coil system is a low-pass configuration. The tuning structure can change the resonant frequency of the nuclide by adjusting the capacitance values of the fifth capacitor 55 , the sixth capacitor 56 and the seventh capacitor 57 .

Exemplarily, with reference to FIG. 5 , the wires (such as the first wire 21, the second wire 22 and the third wire 23) include two linear conductors 20, and the fifth capacitor 55 is connected between two adjacent linear conductors 20. , the sixth capacitor 56 is connected between two adjacent linear conductors 20 , and the seventh capacitor 57 is connected between two adjacent linear conductors 20 .

Fig. 6 is the schematic diagram that another kind of birdcage radio frequency coil system that the embodiment of the application provides expands the birdcage radio frequency coil system in the XZ plane, referring to Fig. 6, the birdcage radio frequency coil system also includes a plurality of first capacitors 51, a plurality of A second capacitor 52 , a plurality of third capacitors 53 , a plurality of fourth capacitors 54 , a plurality of fifth capacitors 55 , a plurality of sixth capacitors 56 and a plurality of seventh capacitors 57 . In the embodiment of the present application, the birdcage RF coil system is a tuning structure with a mixed configuration, which can be adjusted by adjusting the first capacitor 51, the second capacitor 52, the third capacitor 53, the fourth capacitor 54, the fifth capacitor 55, and the sixth capacitor The capacitance values of the capacitor 56 and the seventh capacitor 57 change the resonant frequency of the nuclide.

Referring to FIG. 1 and FIG. 4 , along the extension direction of the central axis K, the length of the first wire 21 is smaller than that of the second wire 22 , and the length of the third wire 23 is shorter than that of the second wire 22 . In the embodiment of the present application, the lengths of the first wire 23 and the third wire 23 are both shorter than the length of the second wire 22, and the length of the wires at both ends is shorter than the length of the wire in the middle, so as to reduce the coupling effect between multiple nuclides.

In one embodiment, referring to FIG. 1 and FIG. 4 , along the extension direction of the central axis K, the length of the first wire 21 is equal to the length of the third wire 23 .

In one embodiment, referring to FIGS. 1-4 , the width of the first conducting wire 21 , the width of the second conducting wire 22 and the width of the third conducting wire 23 are equal. That is, the width of the first wire 21 is equal to the width of the second wire 22 , and the width of the second wire 22 is equal to the width of the third wire 23 . Improve the uniformity of the magnetic field strength.

In other embodiments, at least two of the first guide wire 21, the second guide wire 22 and the third guide wire 23 may have unequal widths to form an uneven magnetic field strength, so as to be suitable for nuclear magnetic resonance in areas such as the abdomen. imaging.

Figure 7 is a circuit diagram of a dual-tuning circuit in a four-terminal ring birdcage radio frequency coil system that supports triple-nuclide imaging provided by an embodiment of the present application. Referring to Figure 7, the dual-tuning circuit 30 includes a first variable capacitor C1, a second The second variable capacitor C2, the third variable capacitor C3, the fourth variable capacitor C4, the fifth variable capacitor C5 and the inductance coil L1. The first plate of the first variable capacitor C1 is electrically connected to the first end of the excitation source 40 , and the second plate of the first variable capacitor C1 is electrically connected to the first plate of the second variable capacitor C2 . The second plate of the second variable capacitor C2 is electrically connected to the first end of the excitation port 15 (ie, an arc-shaped conductor 10 ). The first plate of the third variable capacitor C3 is electrically connected to the second end of the excitation source 40 , and the second plate of the third variable capacitor C3 is electrically connected to the first plate of the fourth variable capacitor C4 . The second plate of the fourth variable capacitor C4 is electrically connected to the second end of the excitation port 15 (that is, another arc-shaped conductor 10 ). The first plate of the fifth variable capacitor C5 is electrically connected to the second plate of the first variable capacitor C1, and the second plate of the fifth variable capacitor C5 is electrically connected to the second plate of the third variable capacitor C3. connect. A first end of the inductance coil L1 is electrically connected to the second plate of the first variable capacitor C1, and a second end of the inductance coil L1 is electrically connected to the second plate of the third variable capacitor C3. The fifth variable capacitor C5 is connected in parallel with the inductance coil L1.

Figure 8 is a schematic diagram of another four-terminal ring birdcage radio frequency coil system supporting three-nuclide imaging provided by the embodiment of the present application. Referring to Figures 1-8, the birdcage radio frequency coil system includes a birdcage radio frequency coil 100, a birdcage The radio frequency coil 100 includes the first end ring 11 , the second end ring 12 , the third end ring 13 , the fourth end ring 14 , the first wire 21 , the second wire 22 and the third wire 23 in the above embodiments. The birdcage radio frequency coil system can also include a shielding layer 60, the shielding layer 60 is positioned at the periphery of the birdcage radio frequency coil 100, the first end ring 11, the second end ring 12, the third end ring 13, the fourth end ring 14, the first The wire 21 , the second wire 22 and the third wire 23 are respectively located in the shielding layer 60 , and the shielding layer 60 can reduce the amplitude of the interference signal and protect the external radiation of the radio frequency signal.

In the above-mentioned multiple embodiments, the numbers of any two of the first conductive wires 21 , the second conductive wires 22 and the third conductive wires 23 are equal. In the above embodiments, the number of the first conductive wires 21 , the second conductive wires 22 and the third conductive wires 23 is 8 as an example, and in other embodiments, the number may be 4, 16 or 32.

Exemplarily, the shielding layer 60 forms a cylindrical surface around the central axis K, the diameter of the cylindrical surface is 20 cm, the length is 23 cm, and the thickness is 0.15 mm. The material of the shielding layer 60 can be pure copper. The first end ring 11 , the second end ring 12 , the third end ring 13 and the fourth end ring 14 may have a diameter of 18 cm. The length of the second wire 22 is 13 cm. By adjusting the capacitance values of the first capacitor 51 , the second capacitor 52 , the third capacitor 53 and the fourth capacitor 54 , the resonant frequency is ²³ Na (33.9 MHz) in the 3T system. The width and length of the wires in this setting method can be optimized to ensure the optimal emission field uniformity and high emissivity at the target frequency. The lengths of the first wire 21 and the third wire 23 are both 2.5 cm. The double-tuning circuit 30 realizes the accurate excitation and reception of ¹ H/ ¹⁹ F frequency (128.2MHz/120.6MHz), the excitation port A and the excitation port B keep the same circuit, and there may be small differences in circuit parameter values.

In an embodiment, the birdcage radio frequency coil system may further include a radio frequency transceiver switch, which is electrically connected to the excitation port, and the radio frequency transceiver switch is configured to excite and collect magnetic resonance nuclide signals, that is, to realize the integrated function of transceiver.

Claims (10)

A four-terminal ring birdcage RF coil system supporting triple-nuclide imaging, including: The first end ring (11), the second end ring (12), the third end ring (13) and the fourth end ring (14), the first end ring (11), the second end ring (12 ), the third end ring (13) and the fourth end ring (14) are arranged on the concentric axis (K), and the second end ring (12) is located between the first end ring (11) and the Between the third end ring (13), the third end ring (13) is located between the second end ring (12) and the fourth end ring (14); the first end ring ( 11), at least one of the second end ring (12), the third end ring (13) and the fourth end ring (14) has an excitation port (15); A plurality of first conducting wires (21), a plurality of second conducting wires (22) and a plurality of third conducting wires (23), respectively parallel to the central axis (K); the plurality of first conducting wires (21) are connected to Between the first end ring (11) and the second end ring (12), the plurality of second wires (22) are connected to the second end ring (12) and the third end ring (13) ), the plurality of third wires (23) are connected between the third end ring (13) and the fourth end ring (14); A double harmonic circuit (30) is electrically connected to the excitation port (15), and the double harmonic circuit (30) is used to realize the resonant frequency of the two nuclides. The system according to claim 1, further comprising a plurality of first capacitors (51), a plurality of second capacitors (52), a plurality of third capacitors (53) and a plurality of fourth capacitors (54); The plurality of first capacitors (51) are connected in series in the first end ring (11), the plurality of second capacitors (52) are connected in series in the second end ring (12), the A plurality of third capacitors (53) are connected in series in the third end ring (13), and a plurality of fourth capacitors (54) are connected in series in the fourth end ring (14). The system according to claim 1, further comprising a plurality of fifth capacitors (55), a plurality of sixth capacitors (56) and a plurality of seventh capacitors (57); One fifth capacitor (55) of the plurality of fifth capacitors (55) is connected in series to a corresponding first wire (21) of the plurality of first wires (21), and the plurality of first wires (21) is connected in series. A sixth capacitor (56) in the six capacitors (56) is connected in series to a corresponding second wire (22) in the plurality of second wires (22), and the plurality of seventh capacitors (57) One of the seventh capacitors (57) is connected in series to a corresponding third wire (23) of the plurality of third wires (23). The system according to claim 1, wherein, along the extension direction of the central axis (K), the length of each first wire (21) is less than the length of each second wire (22), and each third The length of the wire (23) is less than the length of each second wire (22). The system according to claim 4, wherein, along the extension direction of the central axis (K), the length of each first wire (21) is equal to the length of each third wire (23). The system according to claim 1, wherein the width of each first conducting wire (21), the width of each second conducting wire (22) and the width of each third conducting wire (23) are equal. The system according to claim 1, wherein the first end ring (11) has two excitation ports (15), and the two excitation ports (15) in the first end ring (11) ) with a phase difference of 90°; Two double harmonic circuits (30) are respectively electrically connected to two excitation ports (15) in the first end ring (11). The system according to claim 7, wherein each excitation port (15) of the two excitation ports (15) in the first end ring (11) produces the resonant frequency of the first species and the second The resonant frequency of the dinuclides; The second end ring (12) has two excitation ports (15), and the phase difference between the two excitation ports (15) in the second end ring (12) is 90°; The two excitation ports (15) in the second end ring (12) generate the resonant frequency of the third nuclide; the resonant frequency of the third nuclide is smaller than the resonant frequency of the first nuclide, and the resonant frequency of the third nuclide is lower than that of the first nuclide. The resonant frequency of the trinuclide is less than the resonant frequency of the second nuclide. The system according to claim 1, wherein said double tuning circuit (30) comprises a first variable capacitor (C1), a second variable capacitor (C2), a third variable capacitor (C3), a fourth variable capacitor Variable capacitance (C4), the fifth variable capacitance (C5) and inductance coil (L1); The first plate of the first variable capacitor (C1) is electrically connected to the first end of the excitation source (40), and the second plate of the first variable capacitor (C1) is connected to the second variable The first plate of the capacitor (C2) is electrically connected; The second plate of the second variable capacitor (C2) is electrically connected to the first end of the excitation port (15); The first pole plate of the third variable capacitor (C3) is electrically connected to the second end of the excitation source (40), and the second pole plate of the third variable capacitor (C3) is connected to the fourth The first plate of the variable capacitor (C4) is electrically connected; The second plate of the fourth variable capacitor (C4) is electrically connected to the second end of the excitation port (15); The first plate of the fifth variable capacitor (C5) is electrically connected to the second plate of the first variable capacitor (C1), and the second plate of the fifth variable capacitor (C5) is connected to the second plate of the fifth variable capacitor (C5). The second plate of the third variable capacitor (C3) is electrically connected; The first end of the inductance coil (L1) is electrically connected to the second plate of the first variable capacitor (C1), and the second end of the inductance coil (L1) is connected to the third variable capacitor ( C3) is electrically connected to the second plate. The system according to claim 1, further comprising a shielding layer (60), said first end ring (11), said second end ring (12), said third end ring (13), said first The four-terminal ring (14), the multiple first wires (21), the multiple second wires (22) and the multiple third wires (23) are respectively located in the shielding layer (60).

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