JPS62190710A - High frequency magnetic field generator/detector - Google Patents

Abstract

PURPOSE:To improve the stability and the efficiency of a high frequency magnetic field generator/detector used in a unclear magnetic resonance apparatus by supplying a power in balance to a pair of wings adjacent with a balanced impedance matching circuit and a balance/imbalance converter. CONSTITUTION:A first variable capacitor 8a is connected between the electrodes 7a and 7b of a pair of wings 1b not capacitively coupled by a fixed capacitor 2. A balance/imbalance converter 9 is, for example, a coaxial cable having an electric length of 1/2 wavelength. The resonance frequency of a stereoscopic circuit which operates as an equivalent series resonator and an impedance matching frequency are adjusted by the capacitor 8a. Second and third variable capacitors 8b, 8c are disposed in a balance type, and, when a coaxial cable having an imbalanced impedance and a transceiver are coupled with a terminal 6, the maximum power is supplied to a load, and voltages of equal amplitude and reverse polarities are applied to the electrodes 7a, 7b. Thus, an LC series resonator is completely supplied with power in balance.

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 2 shows, for example, [Journal of Magnetics]
Resonance (Journal of Magnetic
Resonance) J, Vol. 36, pp. 447-4
This is a perspective view showing a conventional high-frequency magnetic field generator/detector shown on page 51 (1979). It is a coil arranged symmetrically with respect to a predetermined axis (not shown), and has a vertical band (Vθrt
It has a non-protruding part (1a) called an ical band and a protruding part (1b) called a wing. (2) is a fixed capacitor inserted between adjacent wings (1b). (Is) is a wing (1
b) 1 for electric field shielding installed on the inside of the cell via an insulating layer (not shown) and with the above-mentioned axis as a common center;
They are a pair of conductor rings, one conductor ring (3a) is called the top guard ring and the other conductor ring (6b) is called the bottom guard ring.
1) are electrodes formed integrally with a conductor plate (1) and a conductor ring (3), respectively. (5a) and (5b) are matching variable capacitors connected in series between these electrodes (4a) and (ab). (6) is a terminal connected to a transmitter/receiver (not shown), connected to the electrode (4a) via a variable capacitor (5a), and directly connected to the electrode (4b).

A conventional high-frequency magnetic field generator/detector is constructed as described above, and the conductor plate (1), the capacitor (2), and the conductor ring (6) form a three-dimensional circuit that equivalently functions as an LC series resonant circuit. Furthermore, since the electrodes (4a) and (4b) are capacitively coupled, the resonance frequency can be adjusted by adding variable capacitors (5a) and (5b). Therefore, by matching the impedance using variable capacitors (5a) and (5b), it is possible to connect a transmitter/receiver having a predetermined impedance to the terminal (6). Note that the conductor ring (′
6) is used for electric field shielding as described above, that is, for reducing dielectric loss within the measurement object due to the generated electric field when the measurement object is installed in a high frequency magnetic field generator/detector.

[Problem that the invention seeks to solve]

Conventional high-frequency magnetic field generators and detectors do not take into account the balance-unbalance conversion of circuit impedance, so if a common-mode current flows through the coaxial cable connected to the terminal and the operation becomes unstable, the efficiency will decrease. There was a problem.

This invention was made to solve these problems, and takes into account the balance and unbalance of circuit impedance.
The aim is to obtain a stable and efficient high-frequency magnetic field generator/detector.

[Means for solving problems]

The high frequency magnetic field generator/detector according to the present invention includes a first variable capacitor capacitively coupling a pair of adjacent wings, and a second variable capacitor connected to each end of the first variable capacitor.
A balanced impedance matching circuit including a variable capacitor and a third variable capacitor, and a balanced-unbalanced converter connected to the balanced impedance matching circuit are provided.

[For production]

In this invention, a balanced impedance matching circuit and a balanced-unbalanced converter feed balanced power to a pair of adjacent wings.

〔Example〕

FIG. 1 is a perspective view showing an embodiment of the present invention.
) to (3) and (6) are the same as in the conventional example.

It is the first variable capacitor for performance matching, and the electrode (7!L
), (7b) between the electrodes (7a) of the pair of wings (1b) which are therefore not capacitively coupled by the fixed capacitor (2),
(7b) connected between. (8b), (fla) are the first
They are connected to each end of the variable capacitor (8a), and together with the first variable capacitor (8a) constitute a balanced impedance matching circuit (8). (9) is the second variable capacitor (at) of this balanced impedance matching circuit (8).
)) and a balanced-unbalanced converter connected to the third variable capacitor (8C), for example a coaxial cable with an electrical length of half a wavelength. (10) is the bottom guard ring (5b), the first variable capacitor (8a) and the terminal (6
) is the ground wire connected to the Note that the angle 0 formed by the vertical band (11L) is 80° (t (90°).

In this invention, the first variable capacitor (8a) adjusts the resonance frequency and impedance matching frequency of the three-dimensional circuit that functions as an equivalent series resonant circuit. In addition to this, a second variable capacitor (8″b) and a third
By arranging the variable capacitor (8C) in a balanced manner and using the balanced/unbalanced converter (9), when a coaxial cable and transmitter/receiver with unbalanced impedance are connected to the terminal (6), the maximum power can be delivered to the load. can be supplied, and the detected power is also maximized. In this case, the electrode (7a) and (
Since voltages of equal magnitude and opposite polarity are applied to 7b), the LC series resonant circuit is completely balancedly fed. This can increase the stability and efficiency of the high-frequency magnetic field generator/detector.By installing a conductor cylinder, that is, a metal cylinder, for electromagnetic shielding, the loss of the LC resonant circuit can be reduced. A balanced impedance matching circuit consisting of a first variable capacitor that capacitively couples the protrusion, a second variable capacitor and a third variable capacitor connected to each end of the first variable capacitor, and a balanced impedance matching circuit connected to the balanced impedance matching circuit. Since a balanced unbalanced converter is provided, it is possible to obtain a highly stable and efficient high frequency magnetic field generator/detector.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG.
The figure is a perspective view showing a conventional high-frequency magnetic field generator/detector. (1) is a conductor plate, (1'b) is a wing, (2) is a fixed capacitor, (8a) is the first variable capacitor, (8b)
is a second variable capacitor s (a') is a third variable capacitor, (8) is a balanced impedance matching circuit, and (9) is a balanced-unbalanced converter. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 1 Sn Figure 2 Procedural Amendment “Spontaneous” ■8 blocks 1. Current, −υ, ■

Claims (4)

[Claims] (1) At least one pair of H-shaped conductor plates is arranged symmetrically with respect to a predetermined axis, the protrusions of the conductor plates are brought close to each other, and at least three pairs of these protrusions are fixed capacitors. When capacitively coupled, a pair of remaining protrusions are capacitively coupled by a first variable capacitor, thereby forming a three-dimensional circuit that equivalently constitutes an LC resonant circuit, and a three-dimensional circuit connected to the first variable capacitor and each end thereof, respectively. A high frequency magnetic field generator/detector comprising: a balanced impedance matching circuit including a second variable capacitor and a third variable capacitor; and a balanced/unbalanced converter connected to the balanced impedance matching circuit. (2) A three-dimensional circuit includes a pair of conductor rings installed inside a protrusion of a conductor plate with an insulating layer in between and a predetermined axis as a common center, and at least one conductor ring is connected to a ground potential. A high-frequency magnetic field generator/detector according to claim 1, characterized in that: (3) The high-frequency magnetic field generator/detector according to claim 1 or 2, wherein the three-dimensional circuit has a conductor tube having a predetermined axis as its central axis on the outside of the conductor plate. (4) High-frequency magnetic field generation and detection according to any one of claims 1 to 3, wherein the balanced-unbalanced converter is a coaxial cable having an electrical length of 1/2 wavelength. vessel.