JP2004045351A - Double-tuned circuit of nuclear magnetic resonance apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-tuned circuit of a nuclear magnetic resonance apparatus capable of preventing generation of an unintended resonance component near HF by not adopting a conventional method for adding an LC circuit to a long cylindrical conductor 11 for fine adjustment of a resonance frequency of an HF resonance circuit. <P>SOLUTION: While electric contact between a hollow long cylindrical conductor 14 and the long cylindrical conductor 11 is kept by a first spring 15, and while electric contact between an electrode 17 for earthing and a earthed cylindrical electrode 16 is kept by a second spring 18, each member is slid respectively, to thereby vary the HF resonance frequency determined by the sum of lengths of the long cylindrical conductor 11 and the hollow long cylindrical conductor 14 (namely, a sum of inductance), and to establish tuning on the HF side. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a double-tuning circuit of a nuclear magnetic resonance apparatus, and more particularly to a double-tuning circuit of a nuclear magnetic resonance apparatus that has improved withstand voltage against RF voltage by performing a balanced operation.
[0002]
[Prior art]
First, an example of a conventional double tuning circuit in a nuclear magnetic resonance apparatus (Japanese Patent Application No. 2001-317716) will be described. In the following description, of the two types of high frequency for nuclear magnetic resonance, the higher frequency is referred to as HF (high frequency) and the lower frequency is referred to as LF (low frequency) for convenience.
[0003]
FIG. 1 shows an example of a double tuning circuit of a conventional nuclear magnetic resonance apparatus. In the figure, 1 and 2 are conductors. In this example, the conductors 1 and 2 form a parallel line. At the time of HF resonance, the adjustment of the distribution ratio of the input power to the sample coil 3 is performed by adjusting the characteristic impedance of the parallel line resonator constituted by the conductors 1 and 2. Since the conductors 1 and 2 only need to operate as transmission paths, they are not necessarily limited to rod-shaped conductors, and helical coils, coaxial wires with an external conductor grounded, and the like can also be used.
[0004]
A sample coil 3 composed of a solenoid coil, a saddle coil, or the like is connected to upper ends of the conductors 1 and 2 via LF tuning variable capacitors 4 and 5. The lower end of the conductor 2 is directly grounded, and the lower end of the conductor 1 is indirectly grounded via a capacitor 6. Note that, conversely, the lower end of the conductor 1 may be directly grounded, and the lower end of the conductor 2 may be indirectly grounded via the capacitor 6, or as shown in FIG. Both lower ends of the conductor 2 may be indirectly grounded via two capacitors 6, 6 '. Both are equivalent in circuit.
[0005]
An HF matching circuit composed of an HF matching capacitor 7 and a variable condenser 8 is connected to an arbitrary position in the middle of the conductor 2. A variable condenser 9 for HF tuning is connected to an arbitrary position in the middle of the conductor 1. The variable condenser 9 may be connected to an arbitrary position in the middle of the conductor 2 or may be connected to an arbitrary position in the middle of the conductor 1 and an arbitrary position in the middle of the conductor 2 as shown in FIG. You may connect in the form which connects between. Both are equivalent in circuit.
[0006]
Further, in this example, a single HF quarter-wavelength resonator including the conductor 1 and the LF tuning variable condenser 4 is formed. At the same time, another HF quarter-wave resonator including the conductor 2 and the LF tuning variable condenser 5 is formed. Further, a variable capacitor 10 for LF matching is connected to a connection point between the conductor 1 and the capacitor 6.
[0007]
FIG. 4 is a diagram in which the conventional example is rewritten to a more realistic form. In the figure, reference numeral 11 denotes a rod-shaped conductor. In this example, two bar-shaped conductors 11 form a parallel line. Then, at the time of HF resonance, adjustment of the distribution ratio of the input power to the sample coil 3 is performed by adjusting the characteristic impedance of the parallel line resonator constituted by the two rod-shaped conductors 11.
[0008]
A sample coil 3 composed of a solenoid coil, a saddle coil, or the like is connected to the upper end of the rod-shaped conductor 11 via variable capacitors 4 and 5 for LF tuning. The two rod-shaped conductors 11 are connected by the capacitor 6. Of the two bar-shaped conductors 11, the one located on the right side in the drawing is directly grounded, and the one located on the left side in the drawing is indirectly grounded via the HF tuning variable condenser 9. Conversely, even if the rod-shaped conductor 11 located on the left side in the drawing is directly grounded, and the rod-shaped conductor 11 located on the right side in the drawing is indirectly grounded via the HF tuning variable condenser 9. Alternatively, the two rod-shaped conductors 11 may be indirectly connected via the HF tuning variable condenser 9. Both are equivalent in circuit.
[0009]
Further, in this example, a single HF quarter-wave resonator including the rod-like conductor 11 on the right side and the variable condenser 4 for LF tuning is formed. At the same time, another HF quarter-wave resonator including the rod-shaped conductor 11 on the left side and the variable condenser 5 for LF tuning is formed as a whole.
[0010]
An HF matching circuit composed of an LF blocking filter 12 and an HF matching variable condenser 8 for preventing LF frequency components from leaking is connected to an arbitrary position in the middle of the left bar-shaped conductor 11. . An LF matching circuit composed of an HF blocking filter 13 for preventing HF frequency components from leaking and a LF matching variable condenser 10 is connected to the lower end of the same left-side rod-shaped conductor 11.
[0011]
In FIG. 4, both the HF matching circuit and the LF matching circuit are provided on the left rod-shaped conductor 11, but they may be both provided on the right rod-shaped conductor 11, or two matching circuits may be provided. Of the circuits, one matching circuit may be provided on the left bar-shaped conductor 11 and the other matching circuit may be provided on the right bar-shaped conductor 11. Both are equivalent in circuit.
[0012]
[Problems to be solved by the invention]
In such a configuration, in the conventional double tuning circuit, an unintended resonance component is generated near the HF due to the capacitance of the HF tuning variable capacitor 9 itself and the inductance component of the lead wire of the HF tuning variable capacitor 9. This is the original HF resonance circuit (resonance circuit composed of sample coil 3, LF tuning variable condensers 4 and 5, rod-shaped conductor 11, capacitor 6, LF blocking filter 12, and HF matching variable condenser 8) Interference with the resonance of the HF circuit, there is a problem that the performance of the HF circuit is not obtained.
[0013]
In view of the above, an object of the present invention is to eliminate the use of the conventional method of adding an LC circuit to the rod-shaped conductor 11 for fine adjustment of the resonance frequency of the HF resonance circuit, so that an unintended resonance component is generated near the HF. It is an object of the present invention to provide a double-tuning circuit of a nuclear magnetic resonance apparatus which does not occur.
[0014]
[Means for Solving the Problems]
In order to achieve this object, the double-tuned circuit of the nuclear magnetic resonance apparatus according to the present invention comprises:
A sample coil having ends A and B;
A first conductor having one end connected to the end A of the sample coil and the other end connected via a capacitive element or directly grounded;
A second conductor having one end connected to the end portion B of the sample coil and the other end connected via a capacitive element or directly grounded;
A matching circuit and a tuning circuit for the first high frequency;
A matching circuit and a tuning circuit for the second high frequency;
In a double-tuned circuit of a nuclear magnetic resonance apparatus including a grounded cylindrical electrode surrounding a first conductor and a second conductor,
A third conductor slidable in the axial direction of the first conductor while maintaining contact with both the inside of the cylindrical electrode and the first conductor;
A fourth conductor slidable in the axial direction of the second conductor while maintaining contact with both the inside of the cylindrical electrode and the second conductor,
By sliding the third conductor and the fourth conductor in the axial direction of the first conductor and the second conductor, the value of the sum of the inductance of the first conductor and the third conductor combined , And the sum of the inductance of the second conductor and the fourth conductor is varied.
[0015]
The sum inductance of the first conductor and the third conductor and the sum inductance of the second conductor and the fourth conductor each form a first high-frequency quarter-wave resonator. Features.
[0016]
Further, the third conductor and the fourth conductor are connected via a capacitor.
[0017]
In addition, the sliding between the third conductor and the cylindrical electrode and the sliding between the fourth conductor and the cylindrical electrode are performed directly or via a capacitor while maintaining contact.
[0018]
The second high-frequency tuning element includes a connection between the sample coil and the first conductor or a predetermined position closer to the conductor than the connection, and a connection or connection between the sample coil and the second conductor. It is characterized in that it is provided at a predetermined position closer to the conductor.
[0019]
The sum inductance of the first conductor and the third conductor and the sum inductance of the second conductor and the fourth conductor are respectively equal to the first inductance including the tuning element for the second high frequency. Is characterized in that a high-frequency quarter-wave resonator is formed.
[0020]
Further, the first high frequency is characterized in that the frequency is higher than the second high frequency.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 5 shows an embodiment of the double tuning circuit of the nuclear magnetic resonance apparatus according to the present invention. In the figure, reference numeral 11 denotes a rod-shaped conductor. In this example, two bar-shaped conductors 11 form a parallel line. Then, at the time of HF resonance, adjustment of the distribution ratio of the input power to the sample coil 3 is performed by adjusting the characteristic impedance of the parallel line resonator constituted by the two rod-shaped conductors 11.
[0022]
A sample coil 3 composed of a solenoid coil, a saddle coil, or the like is connected to the upper end of the rod-shaped conductor 11 via variable capacitors 4 and 5 for LF tuning. Further, below the rod-shaped conductor 11, two hollow rod-shaped conductors 14 having a predetermined length are provided, and the two hollow rod-shaped conductors 14 are connected by the capacitor 6. In addition, the two hollow rod-shaped conductors 14 slide on the outer wall of each of the two rod-shaped conductors 11 in the axial direction of the rod-shaped conductors 11, so that the lengths of the rod-shaped conductors 11 and the hollow rod-shaped conductors 14 are reduced. The configuration is such that the total sum can be varied, and as a result, the value of the sum of the inductances of the rod-shaped conductor 11 and the hollow rod-shaped conductor 14 can be varied. Further, the first spring 15 keeps the contact between the rod-shaped conductor 11 and the hollow rod-shaped conductor 14 at all times, so that electrical conduction between the two is maintained.
[0023]
In addition, a grounded cylindrical electrode 16 is provided so as to surround the two rod-shaped conductors 11 and the two hollow rod-shaped conductors 14. In order to maintain electrical continuity between the two rod-shaped conductors 11 and the two hollow rod-shaped conductors 14 and the cylindrical electrode 16, the two rod-shaped conductors are surrounded by two An earthing electrode 17 electrically connected to the hollow rod-shaped conductor 14 is provided. A second spring 18 is provided on the outer edge of the grounding electrode 17 to always maintain electrical continuity between the grounding electrode 17 and the grounded cylindrical electrode 16.
[0024]
Thereby, in this example, the total inductance including the combined inductance of the right-hand rod-shaped conductor 11 and the right-hand hollow rod-shaped conductor 14 and the LF tuning variable condenser 4 constitutes one quarter-wave resonance of one HF. Forming a bowl. At the same time, another HF quarter-wave resonator including the sum inductance synthesized by the left rod-shaped conductor 11 and the left hollow rod-shaped conductor 14 and the LF tuning variable condenser 5 is used. Has formed.
[0025]
An HF matching circuit including an LF blocking filter 12 for preventing LF frequency components from leaking and a HF matching variable condenser 8 is connected to an arbitrary position in the middle of the left hollow rod-shaped conductor 14. I have. Further, the lower end of the hollow rod-shaped conductor 14 on the left side is connected to an LF matching circuit composed of an HF blocking filter 13 for preventing HF frequency components from leaking and an LF matching variable condenser 10. .
[0026]
In FIG. 5, the HF matching circuit and the LF matching circuit are both provided on the left hollow rod-shaped conductor 14. However, they may be provided on the right hollow rod-shaped conductor 14, or Of the two matching circuits, one matching circuit may be provided on the left hollow rod-shaped conductor 14, and the other matching circuit may be provided on the right hollow rod-shaped conductor 14. In addition, these two matching circuits may be configured to be able to move together with the sliding of the hollow rod-shaped conductor 14. Both are equivalent in circuit.
[0027]
In the present embodiment, the sample coil 3, the LF tuning variable condensers 4 and 5, the rod-shaped conductor 11, the capacitor 6, the first spring 15, the hollow rod-shaped conductor 14, the ground electrode 17, the second spring 18, and the ground are grounded. An LF resonance circuit including the cylindrical electrode 16, the HF blocking filter 13, and the variable condenser 10 for LF matching resonates near the LF frequency. In addition, the sample coil 3, the LF tuning variable condensers 4, 5, the rod-shaped conductor 11, the capacitor 6, the first spring 15, the hollow rod-shaped conductor 14, the ground electrode 17, the second spring 18, the grounded cylindrical electrode 16, an LF rejection filter 12, and an HF resonance circuit composed of an HF matching variable condenser 8 resonate near the HF frequency.
[0028]
In such a configuration, when the circuit is tuned to two different frequencies, the following adjustment is performed.
[0029]
First, the LF tuning variable condensers 4 and 5 are varied to perform tuning on the LF side. Then, since the LF tuning variable capacitors 4 and 5 are in the HF resonance circuit, the resonance frequency on the HF side changes as the LF tuning variable capacitors 4 and 5 are varied. Then, next, the HF frequency adjusting member in which the first spring 15, the hollow rod-shaped conductor 14, the capacitor 6, the ground electrode 17, and the second spring 18 are integrated is moved to tune the resonance frequency on the HF side. I take the. That is, the first spring 15 maintains electrical contact between the hollow rod-shaped conductor 14 and the rod-shaped conductor 11, and the second spring 18 connects the grounded electrode 17 to the grounded cylindrical electrode 16. While maintaining the electrical contact, the HF is slid to change the resonance frequency of the HF determined by the sum of the lengths of the rod-shaped conductor 11 and the hollow rod-shaped conductor 14 (that is, the sum inductance), thereby achieving tuning on the HF side.
[0030]
At this time, on the LF side, the resonance frequency is not determined by the lengths of the rod-shaped conductor 11 and the hollow rod-shaped conductor 14, so even if the sum of the lengths of the rod-shaped conductor 11 and the hollow rod-shaped conductor 14 is changed, The resonance frequency on the LF side hardly changes. As a result, the resonance frequency of the circuit can be tuned to both the HF and LF frequencies.
[0031]
In addition, various modifications are possible in the present invention. For example, in FIG. 5, it is possible to adopt a configuration that does not use the variable capacitors 4 and 5 for LF tuning, or a configuration that uses a coil (inductor) instead of the variable capacitor. In addition, these LF tuning elements are not limited to being provided at the connection between the sample coil 3 and the rod-shaped conductor 11. For example, the LF tuning elements are located at predetermined positions closer to the rod-shaped conductor 11 than the connection (for example, the rod-shaped conductor 11). 11 (in the middle of 11).
[0032]
In the above embodiment, the variable operation of the LF tuning variable condensers 4 and 5 and the variable operation of the sum of the lengths of the rod-shaped conductor 11 and the hollow rod-shaped conductor 14 (that is, the sum inductance) are separately performed. When the variable capacitors 4 and 5 are changed, the sum of the lengths of the rod-shaped conductor 11 and the hollow rod-shaped conductor 14 (that is, the sum inductance) may be simultaneously varied according to the variable amount of the capacitance.
[0033]
Further, in FIG. 5, the hollow rod-shaped conductor 14 and the ground electrode 17 are directly connected, but may be connected via the capacitor 6 as shown in FIG. 5 and 6, the condenser 6 may be divided into a plurality.
[0034]
In FIG. 6A, the LF blocking filter 12, the HF matching variable condenser 8, and / or the HF blocking filter 13, and the LF matching variable condenser 10 are fixed to the ground electrode 17, and It may be configured to move simultaneously.
[0035]
Further, in the above embodiment, the hollow rod-shaped conductor 14 sliding on the outer wall surface of the rod-shaped conductor 11 was used. On the contrary, the rod-shaped conductor 11 is hollower and the inner wall surface of the hollow portion is Needless to say, a configuration may be adopted in which the solid rod-shaped conductor 14 slides.
[0036]
【The invention's effect】
As described above, according to the double-tuned circuit of the nuclear magnetic resonance apparatus of the present invention, the first spring 15 maintains the electrical contact between the hollow rod-shaped conductor 14 and the rod-shaped conductor 11 while maintaining the second spring. While maintaining electrical contact between the ground electrode 17 and the grounded cylindrical electrode 16 by the spring 18, each of them is slid, and the sum of the lengths of the rod-shaped conductor 11 and the hollow rod-shaped conductor 14 (ie, sum inductance) The resonance frequency of the HF determined by the above is varied, and tuning on the HF side is performed. Therefore, tuning to the HF can be performed without adding an LC circuit for fine adjustment of the resonance frequency of the HF resonance circuit, and the intention near the HF is obtained. It has become possible to provide a double-tuned circuit of a nuclear magnetic resonance apparatus in which no undesired resonance components are generated.
[Brief description of the drawings]
FIG. 1 is a diagram showing a double tuning circuit of a conventional nuclear magnetic resonance apparatus.
FIG. 2 is a diagram showing a double tuning circuit of a conventional nuclear magnetic resonance apparatus.
FIG. 3 is a diagram showing a double tuning circuit of a conventional nuclear magnetic resonance apparatus.
FIG. 4 is a diagram showing a double tuning circuit of a conventional nuclear magnetic resonance apparatus.
FIG. 5 is a diagram showing one embodiment of a double tuning circuit of the nuclear magnetic resonance apparatus according to the present invention.
FIG. 6 is a diagram showing one embodiment of a double tuning circuit of the nuclear magnetic resonance apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... conductor, 2 ... conductor, 3 ... sample coil, 4 ... LF tuning variable condenser, 5 ... LF tuning variable condenser, 6 ... condenser, 6 '... condenser 7: HF matching condenser, 8: HF matching variable condenser, 9: HF tuning variable condenser, 10: LF matching variable condenser, 11: rod-shaped conductor, 12: LF blocking filter , 13: HF blocking filter, 14: hollow rod-shaped conductor, 15: first spring, 16: cylindrical electrode, 17: ground electrode, 18: second spring .

Claims (7)

A sample coil having ends A and B;
A first conductor having one end connected to the end A of the sample coil and the other end connected via a capacitive element or directly grounded;
A second conductor having one end connected to the end portion B of the sample coil and the other end connected via a capacitive element or directly grounded;
A matching circuit and a tuning circuit for the first high frequency;
A matching circuit and a tuning circuit for the second high frequency;
In a double-tuned circuit of a nuclear magnetic resonance apparatus including a grounded cylindrical electrode surrounding a first conductor and a second conductor,
A third conductor slidable in the axial direction of the first conductor while maintaining contact with both the inside of the cylindrical electrode and the first conductor;
A fourth conductor slidable in the axial direction of the second conductor while maintaining contact with both the inside of the cylindrical electrode and the second conductor,
By sliding the third conductor and the fourth conductor in the axial direction of the first conductor and the second conductor, the value of the sum of the inductance of the first conductor and the third conductor combined And a variable value of the sum of the inductances of the second conductor and the fourth conductor. The sum inductance of the first conductor and the third conductor, and the sum inductance of the second conductor and the fourth conductor form a first high-frequency quarter-wave resonator, respectively. The double-tuned circuit of the nuclear magnetic resonance apparatus according to claim 1, wherein 2. The double-tuned circuit according to claim 1, wherein the third conductor and the fourth conductor are connected via a capacitance element. 3. The sliding between the third conductor and the cylindrical electrode and between the fourth conductor and the cylindrical electrode while maintaining the contact directly or via a capacitor element, wherein the sliding is performed. A double-tuned circuit of the nuclear magnetic resonance apparatus according to the above. The tuning element for the second high frequency is located at a predetermined position closer to the conductor than the connection between the sample coil and the first conductor or the connection between the sample coil and the second conductor. 5. The double-tuned circuit of a nuclear magnetic resonance apparatus according to claim 1, wherein the double-tuned circuit is provided at a predetermined position near a conductor. The sum inductance of the first conductor and the third conductor and the sum inductance of the second conductor and the fourth conductor are respectively equal to the first high frequency including the tuning element for the second high frequency. 6. A double-tuned circuit for a nuclear magnetic resonance apparatus according to claim 5, wherein a quarter-wavelength resonator is formed. 7. The double-tuned circuit according to claim 1, wherein the first high frequency has a higher frequency than the second high frequency.

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