JPS6334906A - Device for generating and detecting high frequency magnetic field - Google Patents

Abstract

PURPOSE:To improve the power supplying efficiency of a high frequency magnetic field generation detector by opposing the ends of split vertical conductors at a predetermined gap, using the ends as power supplying points, and supplying power in balance to the points through an unbalance/balance converter provided separately. CONSTITUTION:Balanced powers are supplied from power supplying points 7a, 7b through a matching circuit 8 to an equivalent resonator which is composed of a coil 1 made of vertical and lateral conductors 1a, 1b, a capacitor 2, and a guard ring 3 disposed through a dielectric element inside the conductor 1b. The resonance frequency can be mainly regulated by moving upward or downward the ring to vary an electrostatic capacity between the lateral conductors disposed adjacently, and the matching state can be regulated by altering the variable capacitors 8a-8c of the matching circuit 8. Loads are balanced with respect to an earth, the supplying current is completely converted to balanced currents necessary for intrinsic loads which contain coils to be supplied, and resonated and matched regularly. Thus, the power supplying efficiency can be extremely improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high frequency magnetic field generation/detection device, particularly to a high frequency magnetic field generation/detection device used in a nuclear magnetic resonance apparatus.

[Prior art] Figure 4 shows, for example, a journal op magnetic
Resonance ( Journal of Magneti
cResonance) 3 6th volume. pages 447-45
This is a diagram showing a conventional high-frequency magnetic field generation/detection device shown on page (Yu 979).
al band) (la), wing (wing)
(lb) Consists of a window portion (1c). (2) is a capacitor inserted between adjacent wings, and (3) is a protective ring for electric field shield installed inside the wing via an insulating layer, called a guard ring, and the top guard ring. (Top Guard R
ing )-(3a), Bottom Guard Link (Bot
tom Guard Ring) (3b). (4) is a feeding point, (5) is an impedance matching capacitor, and (6) is a terminal connected to a transmitter/receiver.

Next, the operation will be explained.

Coil part (1), capacitor (2), guard ring (
3) constitutes an equi-constrained KLO series resonant circuit. It is connected to a transmitter and receiver (not shown) having a predetermined impedance via an impedance matching capacitor (5) and a terminal (6), and current is supplied from the transmitter to the coil section (1) to generate a predetermined high-frequency magnetic field. The coil part (1) serves to guide the signal from the object to be measured provided in the coil part (1) to the receiver.

The guard ring (3) functions as an electric field shield and reduces dielectric loss within the measurement object due to the generated electric field when the measurement object is installed in this high frequency magnetic field generating fist detection device.

[Problem that the invention seeks to solve]

Conventional high-frequency magnetic field generation/detection devices are configured as described above, so balance-unbalance conversion of circuit impedance is not taken into account, and a common-mode current flows through the coaxial cable connected to terminal (6), causing unbalance. There were drawbacks such as stability and low efficiency.

The present invention has been made to solve the above-mentioned problems, and aims to provide a stable and efficient high-frequency magnetic field generation/detection device by taking into consideration the unbalanced circuit impedance.

Furthermore, when the whole-body high-frequency coil is cylindrical, the efficiency of generating the transmitting magnetic field is low, and the S/IJ (Sig.
There were problems such as a relatively small noise ratio (nal to noise ratio).

[Means for solving problems]

The high frequency magnetic field generation/detection device according to the present invention has a structure in which a vertical band (vertical conductor part) of a coil part is divided at the center, and the ends of the vertical conductor part are opposed with a predetermined gap, Each end portion of the divided vertical conductor portion is used as a power feeding point, and balanced power is fed to this feeding point via a separately provided unbalanced/balanced conversion circuit. In addition, the shape of the high-frequency coil for the whole body is made into an oval shape.

[Effect]

The high frequency magnetic field generation/detection device according to the present invention has the above configuration, so that the coil part (1) has a balanced current (relative to ground) that effectively acts only on the true load including the coil part.
Only currents that are in the opposite phase flow, and common-mode currents that are in the same phase as the ground are suppressed, significantly improving power supply efficiency.

Further, by making the whole body high-frequency coil elliptical, the efficiency of generating the transmitting magnetic field and the S/N of the received signal are improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of an embodiment of the present invention, and FIG. 2 is a partially sectional configuration diagram for explaining the same.

In FIG. 1 and FIG. 2, the same reference numerals indicate the same or corresponding parts. (1) is the coil part and the vertical conductor part (
la) (corresponding to the vertical pant of the conventional example), and a horizontal conductor part (corresponding to the wing of the conventional example).

(2) is a capacitor that capacitively couples the ends of adjacent horizontal conductor portions. (3) are guard rings; top guard ring (3a) and bottom guard ring (3a).
(6) is a terminal that supplies the power supply current and takes out the detection current. (7a).

(7b) is a feeding point, and (8) is a matching circuit consisting of three variable capacitors (8a), (8b), and (8c). (9) is a 1/2 wavelength cable, which delays the unbalanced current supplied from the terminal (6) by 1800 degrees, converts it into a negative phase, passes through the matching circuit (8), and connects it to the two feeding points (7a) and (7b).
It functions as an unbalanced/balanced converter that allows currents of the same amplitude and opposite phase to be supplied to the QO is the gap between the vertical conductor parts facing each other 0. An example of the angle θ formed by the vertical conductor part (1a) is 80
〈θ〈900.

(]C) is the vertical conductor part (1a) and the horizontal conductor part (1a).
b) This is the space surrounded by the coil part and is called the window part of the coil part.

In addition, aυ is a ring that connects the top guard ring (3a) and the bottom guard link (3b) in an insulated state, and by moving it up and down, the capacitance between the guard ring and the horizontal conductor facing the guard ring can be adjusted. This makes it possible to change the coupling capacitance between adjacent horizontal conductor parts.

The high frequency coil has an elliptical cylindrical shape, and FIG. 1 shows an example in which the vertical attachment band is arranged in the short axis direction of the ellipse, and FIG. 3 shows an example in which it is arranged in the long axis direction.

Next, the operation will be explained.

The coil part (1), the capacitor (2), and the horizontal conductor part (1b) consist of a vertical conductor part (1a) and a horizontal conductor part (1b).
) is placed inside the guard link (3) through the dielectric material.
), the feed point (7a).

Balanced power feeding can be performed from (7b) through a matching circuit (8).

The resonance frequency can be adjusted mainly by moving the ring up and down to change the capacitance between adjacent horizontal conductor parts.

Also, the matching state is determined by the variable capacitor (8a) of the matching circuit (8).
), (8b), and (8c).

In this configuration, the load is balanced with respect to the ground, and the feed current is completely converted into a balanced current (a current in reverse phase with respect to the ground) required by the true load including the coil section and supplied. In addition, since resonance and matching are properly achieved, power feeding efficiency is extremely high.

Furthermore, with this configuration, signals from the measurement target placed in the coil section (1) can also be efficiently extracted.

Further, in the above embodiment, a case has been described in which the unbalanced/balanced conversion is configured using a 172 wavelength cable, but a transformer having a well-balanced secondary winding may also be used. Further, it is also possible to supply power to one of the vertical conductor parts and connect a capacitor between the opposite vertical conductor parts to correspond to a high frequency.

In addition, the cylindrical high-frequency magnetic field generation/inspection TG for the whole body has become larger, and the efficiency of transmitting magnetic field generation or the S/N of the received signal has increased.
becomes smaller. Since the cross section of the human body is approximately elliptical, the high-frequency magnetic field generator/detector can be made into an elliptical cylinder whose diameter is the major axis. As a result, the efficiency of magnetic field generation is higher than in the case of a cylinder, and the S/N of the received signal is
It also improves.

For example, for 64MH2, it has been found through experiments that the transmitted magnetic field increases by 60 to 70% for the same transmission power in the case of an oval shape compared to the case of a cylinder.

Further, when the RF horizontal is installed so that the major axis direction of the ellipse is horizontal, the vertical punts are arranged in the minor axis direction and the major axis direction depending on whether the high frequency magnetic field is generated horizontally or vertically.

〔Effect of the invention〕

As described above, the high-frequency magnetic field generation/detection device according to the present invention has a high-frequency magnetic field generation/detection device for the whole body.
has also been improved. In addition, the vertical conductor part of the coil part is divided into two at the center, and the end part of the vertical conductor part is used as a feeding point, and a separate unbalanced/balanced conversion circuit is installed to supply balanced power to this feeding point. Therefore, only the balanced current that effectively acts only on the true load including the coil portion is fed to the coil portion, and no unbalanced current flows, resulting in the effect of significantly improving power feeding efficiency and signal detection efficiency.

[Brief explanation of the drawing]

Fig. 1 is an embodiment of the present invention, Fig. 2 is an explanatory drawing of this embodiment, Fig. 3 is a perspective view showing another embodiment of the invention, and Fig. 4 is a diagram showing a conventional example. . (1) Coil part, (la) Vertical conductor part, (1'b) Horizontal conductor part, (lc) Window part, (2) Capacitor, (3 )...Guard ring, (3a)...Top guard ring, (3b)
... Bottom guard ring, (6) ... Terminal, (7a
), ('7b)... feeding point, (8) -... matching circuit,
(aa), (sb), (sc)...variable capacitor, (9)...bow/two-wavelength cable, αO...gear lath αυ...ring. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (6)

[Claims] (1) A T-shaped conductor plate having a vertical conductor portion with a predetermined width extending in the vertical direction and a horizontal conductor portion with a predetermined width extending left and right at right angles to the upper end of the T-shaped conductor plate is set with the vertical conductor portion in the axial direction. A first conductor in which a plurality of conductors curved to draw an arc are arranged adjacently in an elliptical shape, and a first conductor having a shape substantially similar to the first conductor, and a vertical conductor respectively having a shape similar to the first conductor. a second conductor whose conductor parts are arranged to face each other with a predetermined interval; and a ring-shaped first guard which is arranged inside the horizontal conductor part of the first conductor through a dielectric material of a predetermined thickness. A ring, a ring-shaped second guard ring disposed inside the horizontal conductor portion of the second conductor through a dielectric material of a predetermined thickness, and these two rings are connected, and the first ring and the second guard ring are connected to each other. A ring made of an insulator, which is made to move in a parallel manner, and by changing the facing area of each ring and the vertical conductor portion facing each ring, the capacitance therebetween can be changed. , a first feeding point provided on the vertical conductor portion of the first conductor and a second feed point provided on the vertical conductor portion of the second conductor at a position opposite to the vertical conductor portion of the first conductor. A high-frequency magnetic field generation/detection device comprising: a power supply circuit that supplies a high-frequency balanced current to each of the conductors via a power supply point. (2) The high-frequency magnetic field generation/detection device according to claim 1, wherein the three-dimensional circuit has a conductor tube having a predetermined axis as its central axis on the outside of the conductor plate. (3) Balanced power supply is achieved by passing the input current through a 1/2 wavelength circuit, reverse phase, and feeding this signal to each power supply point. The high frequency magnetic field generation/detection device according to item 1 or 2. (4) Balanced power supply is achieved by supplying input current to each power supply point via a λ/2 circuit and an impedance matching circuit. The high frequency magnetic field generation/detection device according to any one of paragraphs. (5) The power is supplied to one or more sets of the power supply points, and the power supply points to which power is not supplied are connected to a predetermined impedance.
The high frequency magnetic field generation/detection device according to any one of paragraphs. (6) The scope of the above claim, characterized in that the first conductor and the second conductor are constructed by connecting horizontal conductor portions of adjacent T-shaped conductor plates via a predetermined capacitance. The high frequency magnetic field generation/detection device according to any one of Items 1 to 5.