JPS62132158A - High frequency magnetic field generator/detector - Google Patents

Abstract

PURPOSE:To increase matching capacity of an impedance matching capacitor in NMR, by connecting capacitor to high frequency coil to equivalently lower the inductance thereof. CONSTITUTION:A capacitor 4 is connected to a high frequency coil 1 to equivalently lower the inductance L thereof. An impedance matching capacitor 2A is connected to the capacitor 4 to balance the impedance. The capacitor 4 comprises capacitors 4a and 4b while the capacitor 2A comprises capacitors 2a, 2b and 2c. The capacitor 2c is connected to a balance/imbalance converter 7, for example, a coaxial cable. The capacitor 2b is connected to an input/output terminal 3 through an impedance converter 9. Therefore, as the capacitors are connected to equivalently lower the inductance of the high frequency coil, the electrostatic capacitance of impedance matching variable condenser can be increased to facilitate the designing of a matching circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high frequency magnetic field generator/detector, and particularly to a high frequency magnetic field generator/detector in which the capacitance of a variable capacitor for impedance matching can be increased.

[Conventional technology]

Figure 2 shows, for example, the Oxford e-university
Breath (0XFORD UNIVER8ITY PRE
S8) tD Davit published on page 170
DAVID G, C) ADIAN
) Author's paper Magnetic resonance and its application to biological systems (N
uCier Ma2netmcResonance
a,nd jts ApplcatAons to I
1 is a circuit diagram showing a conventional high-frequency magnetic field generator/detector disclosed by "Avjnp System". In the figure, (1) is a high-frequency coil, for example, a saddle-shaped coil, and its inductance is L and its resistance is (2) is a variable capacitor for impedance matching connected to this high frequency coil (1), and is composed of (core a) and (2b) configured in an L shape.

(3) is an input/output terminal connected to a high frequency transmitter/receiver (not shown), one end of which is connected to r via (b), and the other end is connected to L (1).

A conventional high-frequency magnetic field generator/detector is configured as described above, and since the impedance of the high-frequency coil (tl) and the impedance of the high-frequency transmitter/receiver connected to this high-frequency magnetic field generator/detector are generally different, a variable capacitor ( 2
) to match the impedance of both and maximize power transmission efficiency.

Here, the input and output impedance of the high frequency transceiver is R1
High frequency coil (L is variable capacitor C2a' as mentioned above for the inductance and resistance of /l), (
As shown in Figure 1, the capacitance of (b) is C and C, respectively.
' and the angular frequency for matching is ω, then when the impedances match.

becomes. For example, ω=axxqs, 5xto' (tl seconds), i.e. &J! In fMH2, L-1,o (μH)
r r =/ (Ω).

In the case of R-40 (Ω), becomes.

[Problem that the invention seeks to solve]

In the conventional high frequency all light generation detector, a variable capacitor f-(,21O capacitance,
In particular, since C' in (b) is extremely small at several pF, there are problems such as difficulty in circuit configuration and poor stability.

The present invention was made to solve all of the above-mentioned problems, and aims to provide a high-frequency magnetic field generator/detector in which a matching circuit can be easily designed and the stability is the same.

[Means for solving problems]

The frequency magnetic field generator/detector according to the present invention is provided with a capacitor connected to both ends of a high frequency coil to equivalently lower its inductance.

[For production]

In this invention, the capacitance of the impedance type variable capacitor can be increased by reducing the equivalent inductance of the high frequency coil.

[Examples]

Fig. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, l/l and (j) are exactly the same high frequency coils and input/output terminals as in Fig. 1, but variable impedance matching is used. The capacitor (CoA) consists of (Core A) and (Core B), as well as (Core C) connected in series with these. Furthermore, (ri) is a capacitor for equivalently lowering the inductance of the high frequency coil (4),
(da a) connected between L and (Jc) and r and (2
b) consisting of (tIb) connected between. lyl is a stray capacitance in the high-frequency coil system, and its size is aS. (6) is the equivalent inductance determined by the inductance of the above-mentioned high-frequency coil (c), the resistance molecule 1 capacitor Tll1, and the stray capacitance t (, tl K, and its size is L'.
(ri) is a case where a high frequency coil side with balanced impedance is coupled to a high frequency transmitting/receiving system with unbalanced impedance.Balanced/unbalanced converter to increase transmission efficiency For example, electrical length of t/J wavelength This is a coaxial cable used as a transmission line. (71 is a connection terminal of this balanced/unbalanced converter (ri), consisting of (ffa) connected to (C) and (gb) connected to (2b).

(91 is an impedance converter, for example, a coaxial cable having an electrical length of l/ψ wavelength. (tO) is the connection terminal of this impedance converter (ql,
) is connected to.

In a high-frequency magnetic field generator/detector configured in this way, the impedance of the high-frequency coil Itl is generally different from the input/output impedance of the high-frequency transmitter/receiver connected to the high-frequency coil (/l), so it is necessary to match the impedances of both. .When impedance matching is performed,
When the high-frequency magnetic field Fi generated by the high-frequency coil (tl) is maximized, and at the same time the high-frequency magnetic field is detected by the high-frequency coil (c), the transmission efficiency of the high-frequency energy is maximized. A balanced/unbalanced transformer (7) that connects the transmitting/receiving system and the high frequency coil system having balanced impedance is also essential in order to maximize the transmission efficiency of high frequency energy.

Note that the balanced and unbalanced converter (ri) also has an impedance effect of l vs. q, and its connection terminals (ffa) and (fb
) when looking at the high-frequency coil side is Zc, the connection terminal (tO
), the impedance c of the high-frequency coil system is -.

Furthermore, an impedance converter (?) K! D,
The impedance seen from the input/output terminal (3) is as follows.

The characteristic impedance of the impedance converter (9) is Z
Q: If the impedance seen from the connection terminal (10) to the high-frequency coil side is kZ' (=tongue Zc), then the impedance of the input/output terminal (3) is Z= = Zq'/ Zo (4'1) .

Therefore, the impedance 2 seen from the input/output terminal (3) =
and the impedance Zc seen from the connection terminals (ra) and (gb) are connected by the following relationship.

Zc Since impedance matching is done here, 7. The impedance of L and the high frequency transceiver are equal.

In FIG. 1, the magnitude of the equivalent inductance (6) can be expressed by the following equation.

Here, ω is the angular frequency for impedance matching, L is the inductance of the high-frequency coil H, C8 is the size of the stray capacitance (S) of the high-frequency coil system, and Cc is the capacitor that lowers the inductance of the high-frequency coil (/l) to the same constraint. (4t) capacity.

Also, at this time, the capacity of the variable capacitor (two people) is as follows ω L
'Here, for example, if one coaxial cable with a characteristic impedance of SOΩ is used in parallel as an impedance converter (9) using a coaxial cable, Zq=2. t(Ω)
(9) becomes. In general, the input/output impedance of a high-frequency transmitter/receiver is soΩ, so the value of Zc when the impedances are equal to (1) = q −□ = so ′ (to).

moreover.

For example, (Ll= 27CX e s, s x t 0
When matching at 6(i/S), that is, q 2 , SMIIz, L=i, 0(ttH'), r=y (Ω), (
:B=5 (pF).

Assuming Cc = 10 (pF).

becomes.

In the above embodiment, // is used as a balanced/unbalanced converter.
We used a coaxial cable with an electrical length of
In addition to this, a branch conductor or a super top type may be used. Also, as the characteristic impedance of the coaxial cable used as an impedance converter, SOΩ
Although λ cables are used in parallel, three or more cables may be used in parallel, and coaxial cables having other characteristic impedances may also be used. Furthermore, the impedance converter may be configured using one and the same cable.

Furthermore, a variable capacitor is used as a capacitor to lower the inductance of the high frequency coil to the same constraint, and the temperature is good at °C.
Alternatively, it may be configured with a plurality of capacitor groups.

〔Effect of the invention〕

As described above, according to the present invention, since a capacitor is connected to the high-frequency coil to lower its inductance to an equal constraint, the capacitance of the variable capacitor for impedance matching can be made larger than before, which makes it easy to design a matching circuit. This has the effect of improving the stability of the matching circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional high frequency magnetic field generator/detector. (1) is a high-frequency coil, (CoA) is a variable capacitor for impedance comparison, (31 is an input/output terminal for connecting to a high-frequency transmitter/receiver, (R) is a capacitor that lowers the inductance of the high-frequency coil to the same constraint, f, tl is the stray capacitance in the high-frequency coil system, (le) is the equivalent inductance, (7) is the balanced/unbalanced converter, and (ql is the impedance converter. In the figure, the same symbols indicate the same or equivalent parts. J Procedural amendment (voluntary) 1986, ``5. Magnetic field generator/detector 3, name of person performing correction Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4, agent address 4-1, 2-1 Marunouchi, Chiyoda-ku, Tokyo
No. Marunouchi Building 4th floor (3) Drawing B, H1,',,'
+, ,”6& Contents of the amendment (1) The statement of the current claims is amended as shown in the attached sheet. (2) “Nuclear” in the second line of page 6 of the specification
The description of J is corrected to [Nuclear J. (3) “Iiving” on page 3, line 3 of the specification
The description of J is amended to ``Living J.'' (4) The description of ``consisting of (2a) and (2b) configured in an L-shape'' on page 3, lines 9 to 10 of the specification is changed to ``Living J.'' It consists of variable capacitors (2a) j (2b) connected in parallel and series with (1), respectively. ” he corrected. (5) R on page 3 of Ming #lIl, lines 12-13
(21:+)...L" was changed to "connected to one end of the high-frequency coil (1) (r 1lill in Figure 2) via the variable capacitor (2b), and the other end is connected to the high-frequency coil (1lill). (1) at the other end.” (6) In the 1st and 2nd lines of page 5 of the specification, the statement ``capacity of the variable capacitor (2) for use, particularly'' is amended to read ``capacity of the variable capacitor (2) for use, especially the variable capacitor''. (7) r on page 6, lines 4 to 8 of the specification (2a) φ・
... (4b) The description of J was changed to "variable capacitor (2a) connected in parallel and series with the high frequency coil (1), (
2b) and a variable capacitor (2c) connected in series with the high frequency coil (1). Furthermore, (4) is a capacitor for equivalently lowering the inductance of the high-frequency coil (1), and is a fixed capacitor connected between the variable capacitor (2b) and the above-mentioned one end of the high-frequency coil (1). (4b) and variable capacitor (2c)
and the fixed capacitor (4a) J connected between the above-mentioned other end of the high-frequency coil (1). (8) The statement "a plurality of" on page 11, line 18 of Book #11 is corrected to "a variable capacitor and a fixed capacitor may be used together, and these capacitors are also used in combination." (9) Figure 1 of the drawings will be amended as shown in the attached sheet. (Attachment) Claims +1) A high-frequency coil in a nuclear magnetic resonance apparatus, a capacitor connected to both ends of the high-frequency coil to equivalently reduce its inductance, and a capacitor connected to the high-frequency coil via the capacitor. A high frequency magnetic field generator/detector comprising an impedance matching capacitor and a balanced/unbalanced converter that couples a balanced load consisting of the high frequency coil and both capacitors to an unbalanced high frequency transmitter/receiver. (2) The high frequency magnetic field generator/detector according to claim 1, characterized in that an impedance converter is connected after the balanced/unbalanced converter. (3) The high-frequency magnetic field generator/detector according to claim 1 or 1, wherein the high-frequency coil is a saddle-shaped coil. (4) The high frequency magnetic field generator/detector according to claim 1 or 1, wherein the balanced/unbalanced converter is a transmission line having an electrical length of 1/2 wavelength. . (5) The high-frequency magnetic field generating fist detector according to claim 1, wherein the impedance converter is a transmission line having an electrical length of 1/4 wavelength. (6) The high frequency magnetic field generator/detector according to claim 4 or 5, wherein the transmission line is a coaxial cable.

Claims (6)

[Claims] (1) A high-frequency coil in a nuclear magnetic resonance apparatus, a capacitor connected to both ends of this high-frequency coil to equivalently lower its inductance, an impedance matching capacitor connected to the high-frequency coil via this capacitor, and A high-frequency magnetic field generator/detector comprising a high-frequency coil and a balanced/unbalanced converter for coupling a balanced load consisting of both the capacitors to an unbalanced high-frequency transmitter/receiver. (2) The high frequency magnetic field generator/detector according to claim 1, characterized in that an impedance converter is connected after the balanced/unbalanced converter. (3) The high-frequency magnetic field generator/detector according to claim 1 or 2, wherein the high-frequency coil is a saddle-shaped coil. (4) The high frequency magnetic field generator/detector according to claim 1 or 2, wherein the balanced/unbalanced converter is a transmission line having an electrical length of 1/2 wavelength. . (5) The high frequency magnetic field generator and detector according to claim 2, wherein the impedance conversion surface is a transmission line having an electrical length of 1/4 wavelength. (6) The high frequency magnetic field generator/detector according to claim 1 or 1, wherein the transmission line is a coaxial cable.