Coil-resonator mutual inductance coupling tuning matching method and magnetic resonance wireless coupling coil structure

Abstract

The invention discloses a coil-resonator mutual inductance coupling tuning matching method and a magnetic resonance wireless coupling coil structure for tuning matching by adopting the method. A wireless coil is coupled with a resonator to improve a coil port impedance real part and reduce an imaginary part; the wireless coil is coupled with the other wireless coil which is arranged oppositely to reduce the port impedance real part of the coil, and the wireless coil and the port impedance real part act at the same time, so that the coil can achieve the tuning matching effect more conveniently and can transmit magnetic resonance signals more stably. Compared with an existing wireless coil signal transmission scheme, the wireless coupling coil signal transmission method achieves the purposes of being convenient to assemble, debug and use, reducing external interference and improving stability and coil performance while simplifying the tuning matching process of the wireless coupling coil.

Description

Technical Field

[0001] The present invention relates to a tuning and matching method and a signal transmission device structure, and in particular to a coil-resonator mutual inductance coupling tuning and matching method, and a signal transmission wireless coupling coil structure using a resonator assisted tuning and matching method. Background Art

[0002] The patient's comfort needs to be ensured during the magnetic resonance imaging process. With the application of technologies such as array coils, conventional magnetic resonance coils generally have the problem that the coils and electronic devices are large in size, heavy in weight, and relatively bulky, which may bring a bad experience to patients. The wireless coils used in magnetic resonance imaging can help reduce the weight of the coils, reduce costs, and improve patient comfort. Common wireless coils are based on the principle of inductive coupling, placing two coils relative to each other to transmit signals through mutual inductive coupling. However, similar wireless coil solutions have problems such as cumbersome tuning and matching processes, the working effect is greatly affected by external interference, the imaging area is affected, and the coupling coefficient is low, making it difficult to ensure the imaging quality and signal transmission efficiency of magnetic resonance. Therefore, it is very necessary to propose a new wireless coil structure solution.

[0003] The coils used in magnetic resonance usually use the LC resonant circuit method for tuning and matching. Although the LC resonant circuit method is mature and widely used, this solution will introduce more electronic components and cables, making the entire system more complicated and reducing patient comfort. In addition, the tuning and matching process of the LC resonant circuit is cumbersome, and the capacitors need to be repeatedly disassembled and assembled to ensure the tuning and matching effect, which is not suitable for the tuning and matching of wireless coupling coils. The existing mutual inductance coupling tuning and matching method needs to be expanded for the analysis of the impedance change process, and its operability is not strong and the application scenarios are limited. Therefore, it is necessary to propose a new tuning and matching method for the wireless coil structure.

[0004] Resonators used in magnetic resonance are usually used to amplify the magnetic resonance transmit and receive fields to improve the signal-to-noise ratio of imaging. In order to further expand the application scope of resonators, it is reasonable and worth studying to use resonators to assist tuning and matching when designing wireless coupled signal transmission coils. Summary of the invention

[0005] Purpose of the invention: In view of the problems that the tuning process of conventional signal transmission wireless coupling coils is cumbersome, greatly interfered by the external environment, and affects the imaging area, the present invention proposes a coil-resonator mutual inductance coupling tuning and matching method, and based on this, proposes a magnetic resonance wireless coupling coil structure to achieve the purpose of being convenient and practical, simplifying the tuning and matching process, and improving signal transmission efficiency.

[0006] Technical solution: The present invention proposes a coil-resonator mutual inductance coupling tuning and matching method, in which the first coil used for signal transmission increases the real part of the coil port impedance and reduces the imaginary part by coupling with the resonator, and reduces the real part of the coil port impedance by coupling with the second wireless coil placed oppositely. The two act simultaneously, so that the first wireless coil and the second wireless coil are both tuned and matched.

[0007] Preferably, connecting capacitors in series with the first wireless coil and the second wireless coil can further optimize the imaginary part of the port impedance.

[0008] Preferably, the mutual inductance coefficient can be changed by changing the distance between the wireless coils and the relative position of the wireless coils and the resonator, and the coil port impedance can be adjusted to achieve a better tuning and matching effect.

[0009] According to the above tuning and matching method, the present invention proposes a magnetic resonance wireless coupling coil structure, including a coupling coil group, a resonator, a support structure and a suspension rail group. Among them, the resonator is any resonator with a three-dimensional structure that works at the magnetic resonance frequency, that is, a resonator with a certain internal space to place the wireless coupling coil. The wireless coupling coil group is fixed on the suspension rail, the suspension rail group is fixed on the resonator or on the support structure, and the resonator is connected to the support structure. The wireless coupling coil group includes a wireless coupling coil unit, and the coupling between the wireless coupling coils and between the coil and the resonator is changed by adjusting the fixed position of the wireless coupling coil unit on the suspension rail to achieve tuning and matching of the wireless coupling coil.

[0010] Preferably, the coupling coil group is composed of two coupling coil units with the same structure. Each wireless coupling coil unit includes a coil, a coil frame, a circuit board and a suspension arm. In one wireless coupling coil unit, the coil is wound on a slotted coil frame, the circuit board is fixed on the coil frame, the coil is connected to the coaxial cable through the circuit board, and the coil frame is connected to the suspension arm.

[0011] Preferably, the capacitor welded on the circuit board is connected in series with the coil to form a series resonance, so as to optimize the imaginary impedance of the coil port.

[0012] Preferably, in order to determine the position of the coil, the wireless coupling coil group is connected and fixed to the two suspension rails through a suspension arm, and the coupling conditions between the wireless coupling coils and the coupling conditions between the wireless coupling coils and the resonator are changed by adjusting the fixed position of the suspension arm on the suspension rail to achieve tuning and matching of the wireless coupling coil.

[0013] Preferably, on the support of the overall structure, the support structure includes a support connector and a tripod. The support connector is connected and fixed to the resonator frame and the support connector is connected and fixed to the tripod respectively. A series of positioning holes are arranged on the tripod, and the height adjustment of the resonator can be achieved by selecting positioning holes at different positions and fixing the support connector.

[0014] The present invention provides a method for manufacturing and using a wireless coupling coil structure for signal transmission, comprising the following steps:

[0015] Step 1: Make a resonator with set operating frequency:

[0016] According to the application scenario, a resonator with a set shape and operating frequency is designed and manufactured. The resonator coil is wound on the frame and tuned using lumped elements.

[0017] Step 2: Assemble the resonator, support structure and suspension rail assembly:

[0018] Connect and fix the resonator to the supporting structure parts.

[0019] The suspension rail assembly is secured to the frame or support structure of the resonator.

[0020] Step 3: Make a wireless coupling coil unit:

[0021] According to the resonator structure, combined with simulation and experimental results, the size of the coupling coil is determined, and the parts of the wireless coupling coil unit are designed and manufactured. The coil is wound on a coil frame, and the coil frame is connected to the suspension arm.

[0022] Step 4: Install the wireless coupling coil unit and adjust the position to verify the tuning and matching effect:

[0023] The two wireless coupling coil units are respectively installed on the suspension rail group through the suspension arms, the positions of the two units on the rails are adjusted, and the two coupling coils are connected to the vector analyzer for testing to obtain the best input reflection coefficient and transmission coefficient and achieve the best tuning and matching effect.

[0024] Furthermore, for the magnetic resonance wireless coupling coil structure, the method further includes:

[0025] Step 5: Connect the wireless coupling coil structure to the magnetic resonance system for signal testing:

[0026] The wireless coupling coil structure is placed outside the imaging area. The magnetic resonance receiving coil is connected to a wireless coupling coil via a coaxial cable, and the spectrometer is connected to another wireless coupling coil via a coaxial cable for signal testing and use.

[0027] Beneficial effects: The present invention has the following advantages:

[0028] 1. The present invention proposes a new tuning and matching method, which simplifies the tuning and matching process of wireless coupling coils and does not require a large number of lumped components. By changing the size and relative position of the coupling coil, the mutual inductance between the coil and the resonator changes, and the port impedance of the coil changes accordingly, so that the tuning and matching of the two coupling coils can be more conveniently achieved;

[0029] 2. The wireless coupling coil proposed by the present invention has a simple structure, a small size, a simple use, debugging and assembly process, a stable structure, is easy to move and use, and has a relatively low production cost;

[0030] 3. The wireless coupling coil structure proposed in the present invention, the wireless coupling coil group is placed in the internal space of the resonator with a three-dimensional structure, and the resonator used is covered with shielding materials such as copper tape and copper wire, which can isolate interference from the outside of the resonator to a certain extent. In addition, the slight movement and deformation of the coil has little effect on the mutual inductance coefficient. Under this tuning scheme, the change in the coil port caused by this change is very small, thereby ensuring the stability of the tuning and matching of the wireless coupling coil, reducing its influence by external environmental interference, improving the coil quality factor to a certain extent, and ensuring the transmission efficiency of the signal between the coils. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A circuit diagram and an equivalent circuit diagram of the coupling between the non-tuned coil and the resonator in the present invention;

[0032] Figure 2 A circuit diagram and an equivalent circuit of the coupling between the tuned coil and the non-tuned coil in the present invention;

[0033] Figure 3 It is a schematic diagram and an exploded view of the overall structure of the components of the present invention;

[0034] Figure 4 It is a schematic diagram of the structure of the wireless coupling coil unit in the present invention;

[0035] Figure 5 It is a schematic diagram of the support structure on one side of the present invention;

[0036] The figure includes: a coupling coil group 01, a coupling coil unit 01a, a coil 01a1, a coil frame 01a2, a circuit board 01a3, a suspension arm 01a4, a resonator 02, a bracket structure 03, a bracket connector 03a, a tripod 03b, a positioning hole array 03c, and a suspension guide rail group 04. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more clearly described, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0038] Example 1

[0039] The coil-resonator mutual inductance coupling tuning and matching method is: through the mutual inductance coupling between the wireless coil and the resonator, and between the wireless coils, the coil port impedance is optimized, the tuning and matching of the two coupled coils is achieved, and the stability of the performance of the wireless coupled coil is improved. Specifically, the first wireless coil increases the real part of the coil port impedance and reduces the imaginary part by coupling with the resonator, and reduces the real part of the coil port impedance by coupling with the second wireless coil placed opposite, and the two act simultaneously, so that the first wireless coil and the second wireless coil are both tuned and matched.

[0040] In this embodiment, by adjusting the distance between the wireless coils and the relative position between the wireless coils and the resonator, the coupling condition can be changed to change the port impedance of the coils to achieve tuning and matching, thereby simplifying the use of the wireless coils and the tuning and matching process. The principles involved in the tuning and matching process are described below:

[0041] 1. Non-tuned coil-resonator coupling: The circuit diagram of non-tuned coil-resonator coupling is as follows Figure 1 The equivalent circuit of a general coil affected by inductive coupling is shown in (a). Figure 1 As shown in (b), its port impedance Z can be expressed as:

[0042] Z=R e +jωL e

[0043] Among them, R e is the equivalent resistance, L e is the equivalent inductance. When coupled with a resonator with a specific characteristic frequency, the equivalent resistance and equivalent inductance are:

[0044]

[0045] Among them, ω is the angular frequency, M is the mutual inductance coefficient, R2, L2, C2 are the resistance, inductance and tuning capacitance of the resonator, L1 and R1 are the inductance and resistance of the inductive coupling coil. When working at the characteristic frequency of the resonator, we have:

[0046]

[0047] Then the equivalent resistance R e and equivalent inductance L e Under this condition, it can be expressed as:

[0048] L e =L1

[0049]

[0050] Then the real part of the port impedance is equal to The imaginary part of the impedance is jωL1, where j represents the sign of the imaginary part. By taking the derivative of the expression of equivalent resistance with respect to angular frequency, it can be found that the equivalent resistance has a maximum value at the characteristic frequency. Therefore, at the characteristic frequency, the real part of the coil port impedance is the maximum value, while the imaginary part of the port impedance theoretically does not change. The coupling between the resonator and the coil can increase the real part of the coil port impedance, making it closer to the tuning matching state. On this basis, a capacitor C0 is connected in series with the coil, then the imaginary part of the port impedance Z i Change to:

[0051]

[0052] Therefore, the method of connecting capacitors in series can reduce the imaginary part of the port impedance and further optimize the coil port impedance.

[0053] 2. Tuned coil-non-tuned resonator coupling: The circuit diagram of tuned coil-non-tuned resonator coupling is as follows Figure 2 As shown in (a), the equivalent circuit of the tuning coil under this coupling condition is as follows Figure 2 As shown in (b), the real part of the coil port impedance Z r and the imaginary part Z i Respectively expressed as:

[0054]

[0055] Where R e2 With L e2 are the equivalent resistance and equivalent inductance of the coupled tuning coil respectively.

[0056] For a coil that has been tuned and matched at the working frequency, when it is coupled with a non-tuned resonator whose working frequency is lower than the magnetic resonance working frequency, the resistance, inductance and capacitance of the coil with different working frequencies are R3, L3 and C3 respectively, and the inductance and resistance of the tuned coil are L1 and R1 respectively. In the coil's own tuning and matching circuit, there is a parallel tuning capacitor C r And series matching capacitor C m For a tuned coil, if the eigenfrequency of the resonator coupled to it is lower than the coil operating frequency, according to the LC circuit resonant frequency calculation formula, when the two are coupled, at the coil's operating angular frequency ω, The value of is large, and there is ω 2 L1C r =1. Substituting the above series of expressions into the port impedance calculation formula, the equivalent inductance L in the equivalent circuit e2 This will reduce the coil parameters and change them. Let (1-ω 2 L e2 C r ) 2 The value of is greater than 0, then according to Z rExpression, the denominator of the real part of the impedance expression increases, which will reduce the real part of the coil port impedance.

[0057] In summary, for a coupled coil, the coupling of the resonator to it can increase the real part of its port impedance and reduce the imaginary part of its impedance, while the coupling of another coupled coil to it can reduce the real part of its port impedance. Combining the two can achieve the effect of port impedance optimization.

[0058] Example 2

[0059] Based on the tuning and matching technical principle disclosed in Example 1, this embodiment provides an example of a signal transmission wireless coupling coil structure for resonator-assisted tuning and matching applied to magnetic resonance. Figures 3 to 5 As shown, the signal transmission wireless coupling coil structure includes a coupling coil group, a suspension rail group, a resonator and a bracket structure. Wherein: the resonator is a volume resonator of any shape working at the magnetic resonance frequency. The wireless coupling coil group is positioned in the internal space of the resonator with a three-dimensional structure and vertically suspended on the suspension rail group. The suspension rail group is parallel to the horizontal plane and fixed on the resonator frame. The resonator frame is connected to the tripod through the bracket connector, and the tripod bears the load-bearing function of the entire structure.

[0060] like Figure 4 As shown, a wireless coupling coil unit 01a in the wireless coupling coil group 01 includes a coil 01a1, a coil frame 01a2, a PCB circuit board 01a3 and a suspension arm 01a4. A slot is left on the coil frame 01a2 so that the coil 01a1 can be accurately fixed on the coil frame 01a2. The PCB circuit board 01a3 is fixed on the coil frame 01a2, and the coil 01a1 is connected to the coaxial cable through the PCB circuit board 01a3.

[0061] like Figure 5 As shown, the support structure includes 03 support connector 03a and foot frame 03b. The two are connected and fixed to bear the weight. The positioning hole array 03c on the foot frame 03b is used to adjust the height of the resonator and the coil.

[0062] Example 3

[0063] Based on the above-mentioned resonator-assisted tuning and matching signal transmission wireless coupling coil structure, this embodiment provides a method for manufacturing and using the structure, including the following steps:

[0064] Step 1: Make a resonator with set operating frequency:

[0065] According to the application scenario, a resonator with a set shape and operating frequency is designed and manufactured. The resonator coil is wound on the frame, and lumped elements are used to adjust the operating frequency.

[0066] Step 2: Assemble the resonator, support structure and suspension rail assembly:

[0067] Connect and fix the resonator to the supporting structure parts, and fix the suspension rail assembly to the frame or supporting structure of the resonator;

[0068] Step 3: Make a wireless coupling coil unit:

[0069] According to the resonator structure, the wireless coupling coil is designed through simulation and calculation, and the diameter of the coil, the winding wire diameter and the number of turns are determined, so that the mutual inductance between the coil and the resonator is large enough to ensure that the real part of the port impedance of the coil can be increased to a value higher than 50Ω. According to the simulation and calculation results, the physical object is made and the experiment is carried out. The first coil is placed in the resonator to observe whether its port impedance can be increased to a relatively high value. Then the second coil is placed in the resonator opposite to the first coil to observe whether the real part of the port impedance of the two coils can be reduced to 50Ω, and the capacitor is connected in series to optimize the imaginary part of the port impedance to achieve the coil tuning matching state.

[0070] Based on the above calculation, simulation and experimental results, the size of the coupling coil is determined, and the parts of the wireless coupling coil unit are designed and manufactured. The coil is wound on a coil frame, and the coil frame is connected to the suspension arm.

[0071] Step 4: Install the wireless coupling coil unit and adjust the position to verify the tuning and matching effect:

[0072] The two wireless coupling coil units are respectively installed on the suspension rail group through the suspension arms, the positions of the two units on the rails are adjusted, and the two wireless coupling coils are connected to the vector analyzer for testing to obtain the best input reflection coefficient and transmission coefficient and achieve the best tuning and matching effect.

[0073] Step 5: Connect the wireless coupling coil structure to the magnetic resonance system for signal testing:

[0074] The wireless coupling coil structure is placed outside the imaging area. The magnetic resonance receiving coil is connected to a wireless coupling coil via a coaxial cable, and the spectrometer is connected to another wireless coupling coil via a coaxial cable for signal testing and use.

[0075] Application Examples

[0076] In order to make the features of the present invention more clearly described, the following uses the structure of a signal transmission wireless coupling coil applied to a 2.13MHz portable magnetic resonance instrument as an example, selects important parameter values, and describes the specific implementation of the present invention in more detail.

[0077] The wireless coupling coil structure for signal transmission applied to 2.13MHz magnetic resonance, the resonator used for auxiliary tuning and matching is a 12-pin hat-type low-pass birdcage resonator with an upper diameter of 134mm, a lower diameter of 24mm, an overall height of 102mm, and a copper tape width of 5mm. A 21.5nF capacitor is welded on each leg to make its characteristic frequency 2.13MHz; the wireless coupling coil group for transmitting signals includes two coils with a diameter of 105mm, 2 turns, and a wire diameter of 1mm, which are fixed to the suspension rail by plastic screws; the tripod height is 185mm, the diameter of the positioning hole is 3.1mm, the center distance between each row of positioning holes is 5mm, and there are 8 rows in total.

[0078] The example of the signal transmission wireless coupling coil applied to 2.13MHz magnetic resonance is used to illustrate the principle and function of the present invention, but is not used to limit the present invention. All equivalent modifications based on the present invention should still be covered by the claims of the present invention.

Claims

1. A coil-resonator mutual inductance coupling tuning and matching method, characterized in that: The first wireless coil used for signal transmission increases the real part of the coil port impedance and reduces the imaginary part by coupling with the resonator, and reduces the real part of the coil port impedance by coupling with the second wireless coil placed oppositely. The two work simultaneously, so that the first wireless coil and the second wireless coil are both tuned and matched.

2. A coil-resonator mutual inductance coupling tuning and matching method according to claim 1, characterized in that: Capacitors are connected in series to the first wireless coil and the second wireless coil to further optimize the imaginary part of the port impedance.

3. A coil-resonator mutual inductance coupling tuning and matching method according to claim 1, characterized in that: By changing the distance between the wireless coils and the relative position of the wireless coils and the resonator to change the mutual inductance coefficient, the coil port impedance is adjusted to achieve a better tuning and matching effect.

4. A magnetic resonance wireless coupling coil structure, characterized in that: The invention comprises a wireless coupling coil group (01), a resonator (02), a support structure (03) and a suspension rail group (04); the resonator (02) is connected to the support structure (03), the suspension rail group (04) is fixed on the resonator (02) or the support structure (03), the wireless coupling coil group (01) is fixed on the suspension rail group (04), and the wireless coupling coil group (01) comprises two wireless coupling coil units; the resonator (02) is a resonator with a three-dimensional structure that works at any magnetic resonance frequency, that is, a resonator with a certain internal space for placing the wireless coupling coil; by adjusting the fixed position of the wireless coupling coil unit on the suspension rail (04), the coupling between the wireless coupling coils and between the coil and the resonator (02) is changed to achieve tuning and matching of the wireless coupling coil.

5. The magnetic resonance wireless coupling coil structure according to claim 4, characterized in that: The wireless coupling coil unit comprises a coil (01a1), a coil frame (01a2), a circuit board (01a3) and a suspension arm (01a4); the coil (01a1) is wound on a slotted coil frame (01a2), the coil (01a1) is connected to a coaxial cable via a circuit board (01a3), the circuit board (01a3) is fixed on the coil frame (01a2), and the coil frame (01a2) is fixedly connected to the suspension arm (01a4).

6. The magnetic resonance wireless coupling coil structure according to claim 4, characterized in that: The capacitor welded on the circuit board (01a3) of the wireless coupling coil unit is connected in series with the coil (01a1) to form a series resonance, thereby optimizing the imaginary impedance of the coil port.

7. The magnetic resonance wireless coupling coil structure according to claim 4, characterized in that: The wireless coupling coil group is connected and fixed to two suspension rails in the suspension rail group (04) via a suspension arm (01a4), and the coupling conditions between the wireless coupling coils and the coupling conditions between the wireless coupling coils and the resonator are changed by adjusting the fixed position of the suspension arm (01a4) on the suspension rail.

8. The magnetic resonance wireless coupling coil structure according to claim 4, characterized in that: The resonator (02) is fixed on a support structure (03); the support structure (03) includes a support connector (03a) and a tripod (03b); the support connector (03a) is connected and fixed to the resonator frame, and the support connector (03a) is connected and fixed to the tripod (03b); a series of positioning holes (03c) are arranged on the tripod (03b), and the height adjustment of the resonator (02) is achieved by selecting positioning holes at different positions and fixing them to the support connector (03a).

9. A method for manufacturing and using a wireless coupling coil structure for signal transmission, characterized in that: The steps include: Step 1: Make a resonator with set operating frequency: According to the application scenario, a resonator with a set shape and operating frequency is designed and manufactured. The resonator coil is wound on the frame, and lumped elements are used to adjust the operating frequency. Step 2: Assemble the resonator, support structure and suspension rail assembly: Connect and fix the resonator to the supporting structure parts, and fix the suspension rail assembly to the frame or supporting structure of the resonator; Step 3: Make a wireless coupling coil unit: According to the resonator structure, combined with simulation and experimental results, the size of the coupling coil is determined, and the parts of the wireless coupling coil unit are designed and manufactured. The coil is wound on a coil frame, and the coil frame is connected to the suspension arm; Step 4: Install the wireless coupling coil unit and adjust the position to verify the effect: The two wireless coupling coil units are respectively installed on the suspension rail group through the suspension arms, the positions of the two units on the rails are adjusted, and the two coupling coils are connected to the vector analyzer for testing to obtain the best input reflection coefficient and transmission coefficient and achieve the best tuning and matching effect.

10. The method for manufacturing and using a wireless coupling coil structure for signal transmission according to claim 9, characterized in that: Also includes: Step 5: Connect the wireless coupling coil structure to the magnetic resonance system for testing: The wireless coupling coil structure is placed outside the imaging area, the magnetic resonance receiving coil is connected to a wireless coupling coil via a coaxial cable, and the spectrometer is connected to another wireless coupling coil via a coaxial cable for signal testing and use.

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