JPS6335240A - High frequency magnetic field generating and detecting apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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.

[Conventional technology]

Figure 6 shows, for example, the journal op magnetic
Resonance ( Journal of Magneti
cResonance) Volume 3 6, Pages 447-45
This is a diagram showing the entire conventional high-frequency magnetic field generation/detection device shown on page 1 (19'79).
ical band) (1a), wing
(lb) and the window ('la). (2)
is a capacitor inserted between adjacent wings, (3)
Guard ring is a protective ring for electric field shield installed inside the wing via an insulating layer.
g) and is called a top guard ring (Top Guar ring).
d Ring) (3a), and the bottom guard link (B
ottom 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 LC series resonant circuit equally parsimoniously. The impedance matching capacitor (5) and the terminal (6) are connected to a transmitter and a receiver (not shown) having a predetermined impedance through the impedance matching capacitor (5) and a terminal (6). While creating a high frequency magnetic field, the coil part (1)
It functions to guide the signal from the object to be measured located inside to the receiver. The guard ring (3) functions as an electric field shield, and when a measurement object is installed in this high frequency magnetic field generation/detection device, it reduces the dielectric loss within the object due to the generated electric field.

[Problem that the invention seeks to solve]

Since the high-frequency magnetic field generation/detection device described in Section 6 is configured as shown below, the balance/unbalance conversion of the circuit impedance is not taken into consideration, and the common mode current flows through the coaxial cable connected to terminal (0). There were disadvantages such as the flow of electricity, resulting in instability 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.

In addition, when the high-frequency coil for the whole body is cylindrical, the efficiency of generating the transmitting magnetic field is low, and the S/N (S/N) of the received signal is low.
There were problems such as a relatively small al to noise ratio.

[Means for solving problems]

The high frequency magnetic field generation/detection device according to the present invention has a part at the center of the vertical band (vertical conductor part) of the coil part,
A variable capacitor is constructed by dielectrically bonding the ends of the vertical conductor portions by overlapping them through a dielectric material, and each end portion of the vertical conductor portion is used as a power feeding point, and a separate power source is used. A balanced/balanced conversion circuit is provided to feed balanced power to this feeding point. In addition, the shape of the high-frequency coil for the whole body is made oval.

[Effect]

The high-frequency magnetic field generation/detection device of this invention has the above configuration, so that only a balanced current (a current with a negative phase to the ground) that effectively acts only on the true load including the coil section is applied to the coil section (1). flows, and the common-mode current is suppressed, significantly improving power supply efficiency.

Furthermore, by making the high-frequency coil for the whole body into an elliptical shape, the efficiency of generating the transmitting magnetic field and the 8/N ratio 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 the first embodiment, FIG. 2 is a partially sectional configuration diagram for explaining the same, and FIG. 3 is an equivalent circuit thereof.

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 parts. (3) is a guard ring, which is composed of a top guard ring (3a) and a bottom guard ring (3b). (6) is a terminal that supplies the power supply current and takes out the detection current. ('i'a), ('7b) are feeding points,
Reference numeral (8) denotes a matching circuit, which is composed of a capacitor section (8a) and variable capacitors (8b) and (8Q) which are formed by overlapping portions of upper and lower vertical conductor sections via a dielectric material o0. Note that the capacitance of the capacitor section (8a) can be varied by changing the size of the 9 heavy parts. (9) is an i-wavelength cable, and the unbalanced current supplied from the terminal (6) is delayed by 180 degrees and converted into an inverted phase, and then passes through the matching circuit (8) to two feeding points (7a).

(7b) functions as an unbalanced/balanced conversion so that the same amplitude and negative sequence current can be supplied.

An example of the angle θ formed by the vertical conductor is 8o0〈
θ<900. In addition, (lc) is the vertical conductor part (la
) and the horizontal conductor section (1b), and is called the window section of the coil section.

The shape of the high-frequency coil is an elliptical cylinder Q, and FIG. 1 shows an example in which the vertical punts are arranged in the short axis direction of the ellipse, and FIG. 4 shows an example in which they are arranged in the long axis direction.

Next, the operation will be explained.

As shown in the equivalent circuit of Fig. 3, the vertical conductor portion (1a) (
For an isometric series-parallel resonant circuit consisting of a horizontal conductor coil portion (1), a capacitor (2), a guard ring (3), and a capacitor (8a), the feed point ( '7a) j7b) to matching circuit (3)
Balanced power supply is performed through this process.

The resonant circuit and matching circuit are adjusted so that the desired signal is efficiently supplied to the load.

In this configuration, the load is balanced with equal amplitude and negative phase with respect to the ground, and the feeding current is completely converted into a balanced current 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. again\
Since the structure is such that signals from a measurement target placed inside the coil section can be efficiently extracted.

In the above embodiment, the junctions of adjacent parts of the horizontal conductor portion (1b) were capacitively coupled via the capacitor (2), but as in the other embodiment shown in FIG. The conductor may be removed and connected directly, or the guard ring may also be removed. In such cases, the vertical conductor may be separated into upper and lower parts at the center, overlapped with a dielectric between them, and that part may be used as a power feeding point. By adopting a configuration that applies a balanced power supply system, efficient excitation current supply and signal detection can be performed.

In FIG. 5, the same reference numerals as in FIG. 1 indicate the same or equivalent parts.

In the above embodiments, a single wavelength cable is used as the unbalanced/balanced conversion means, but a transformer with a well-balanced secondary winding may also be used.

Further, a fixed capacitor or a variable capacitor may be connected in parallel to the variable capacitor portion configured via a dielectric provided between the vertical conductor portions, and matching may be achieved using this variable capacitor.

In addition, the cylindrical high-frequency magnetic field generator/detector for the whole body has become larger, and the efficiency of transmitting magnetic field generation or B/II 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 so that the diameter of the cylinder is the major axis. As a result, the efficiency of magnetic field generation is higher than in the case of a cylinder, and the received signal is 87N
It also improves.

For example, for 64 MHz, it has been experimentally found that the transmitted magnetic field increases by 60 to 70 cm for the same transmit power in the case of an elliptical shape compared to the case of a cylinder.

′! 1. RF so that the major axis direction of the fc1 ellipse is horizontal.
Depending on whether the high-frequency magnetic field is generated horizontally or vertically when the coil is installed, the vertical bands are arranged in the minor axis direction and the major axis direction, respectively.

〔Effect of the invention〕

As described above, in the high-frequency magnetic field generation/detection device according to the present invention, the vertical conductor portion of the coil portion is divided into two at the center, and the ends of the vertical conductor portions are overlapped with each other via a dielectric material. In addition to making a variable capacitor with a dielectric-coupled configuration, the end portion of the vertical conductor section is used as a power feeding point, and a separate unbalanced/balanced conversion circuit is provided to feed balanced power to this feeding point. Since only a 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, the power feeding efficiency and signal detection efficiency are significantly improved.

Furthermore, by making the whole-body high-frequency magnetic field generator/detector elliptical in shape, the efficiency of magnetic field generation is high, and the S/N of the received signal is also improved.

[Brief explanation of drawings]

FIG. 1 is an embodiment of this invention, FIG. 2 is an explanatory drawing of this embodiment, FIG. 3 is an equivalent circuit, FIG. 4 is another embodiment of this invention, and FIG. 5 is a drawing for explaining this embodiment. In another embodiment, an example in which the capacitor (2) of FIG. 1 is not provided is shown. FIG. 6 is a diagram showing a conventional example. (1)...Coil part, (1a)...Vertical conductor part, (
1b)...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, (8a)...Capacitor section, (Bb), (Ba)...Variable capacitor, (9)...Stone wavelength cable, C1O... dielectric. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (8)

[Claims] (1) A T-shaped conductor plate having a vertical conductor part with a predetermined width extending in the vertical direction and a horizontal conductor part with a predetermined width provided at the upper end and perpendicular to this and extending left and right. a first conductor in which a plurality of conductors curved to draw a predetermined arc in the axial direction are arranged adjacently in an elliptical shape; a first conductor having a shape substantially similar to the first conductor; a three-dimensional circuit comprising a variable capacitor that changes capacitance by moving a second conductor in the axial direction that is arranged to be engaged with a part of the vertical conductor part in the opposite direction via a dielectric; a first power feeding point provided on the vertical conductor portion of the conductor; and a second power feeding 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 through the conductor. (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) The high frequency magnetic field generation/detection device according to claim 1, further comprising a fixed capacitor or a variable capacitor between the first feeding point and the second feeding point. (4) Balanced power feeding is achieved by passing the input current through a 1/2 wavelength circuit, reverse phase, and feeding this signal to each feeding point. High frequency magnetic field generation according to any one of paragraphs to 3.
Detection device. (5) Balanced power supply is achieved by supplying input current to each power supply point via a 1/2 wavelength circuit and an impedance matching circuit. The high frequency magnetic field generation/detection device according to any one of Item 4. (6) Claims 1 to 5 above, characterized in that 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. (7) The high-frequency magnetic field generation system according to any one of claims 1 to 6, characterized in that the horizontal conductor portions of adjacent T-shaped conductor plates are connected in a DC manner. Detection device. (8) The horizontal conductor portions of adjacent T-shaped conductor plates are connected via a predetermined capacitance. High frequency magnetic field generation/detection device.