JPS59171842A - Transmitting and receiving circuit of nuclear magnetic resonance apparatus - Google Patents

Abstract

PURPOSE:To reduce influence imparted to a receiver and to transmit an obtained resonance signal to the receiver side without losing the same, by differentiating the operation mode of a gate control circuit in applying a high frequency pulse and in detecting a nuclear magnetic resonance signal. CONSTITUTION:High frequency power is generated from a power amplifier 1 by a timing circuit 20 and supplied to a detector 2 through a pair of diodes 12. During this time, the pulse generated in the circuit 20 is applied to a gate control circuit 22 through a pulse amplifier 21. Diodes D1, D2 are inversely biased by this applied pulse to turn the circuit 22 OFF and the leak thereof to the side of a receiver 3 is inhibited. On the other hand, when the amplifier is turned OFF, the pulse generated in the circuit 20 is applied to the circuit 22 to turn the circuit 22 ON and the resonance signal detected by a detector 2 is passed through the circuit 22 to be transmitted to the receiver 3. Thereafter, the leak of the resonance signal to the side of the power amplifier 1 is inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmitter/receiver circuit for a nuclear magnetic resonance system, and more specifically, the present invention relates to a power amplifier that generates high frequency power, and a power amplifier that receives the output of the power amplifier and transmits it to a high TJA field. It is equipped with a detector that detects nuclear magnetic resonance signals while irradiating high-frequency pulses on the sample H, and a receiver that receives the nuclear magnetic resonance signals from the detector! , :IS, Transmission/reception of magnetic resonance apparatus (relating to g-circuit).

When obtaining a nuclear magnetic resonance signal (hereinafter simply referred to as a resonance signal) using a pulsed Fourier nuclear magnetic resonance apparatus, as shown in FIG. ), the sample placed in a high magnetic field is irradiated with high-frequency pulses, the obtained resonance signal is transmitted to the receiver 3, amplified, and then predetermined processing is performed. ing. In such a transmitting/receiving circuit, it is necessary to minimize the influence on the receiver 3 side when applying high frequency power from the power amplifier 1 to the detector 2, and also to transfer the detected resonance signal to the receiver side without loss. \It is necessary to transmit.

For this reason, a configuration as shown in FIG. 2 has conventionally been adopted. In the block diagram of FIG. 2, the same parts as in FIG. 1 are given the same reference numerals. First, the circuit shown in FIG. 2 (a) prevents high-frequency leakage to the receiver 3 side when a high-frequency horn is applied by using a /l/4 cable 1o and a pair of diodes 11 that are connected in reverse to each other. At the time of detection, the power amplifier 1 is turned on by the bare diode 12.The circuit shown in FIG.
A coil 13 forming a step-up circuit is used in place of the Jλ/4 cable 1o shown in FIG. 2(a).
This circuit performs the same function as the circuit shown in ＞. Furthermore, in the circuit shown in FIG. 2(C), a transmission transformer 15 is connected in series to the transmission line 14, and the primary side hr of the lance
While applying a gate pulse for power control and applying a high frequency pulse from the power amplifier 1 to the detector 2, the receiver 3
This is designed to eliminate high frequency leakage to the side. By the way, the circuits shown in Figures 2(a) and (b) have narrow frequency bands, so if a wideband transmitting/receiving circuit is required, multiple circuits may be installed (they should not be used by switching between them). (1) On the other hand, although the circuit shown in Figure 2 (C) can be used in a wide band, it has the disadvantage of avoiding a reduction in reception sensitivity due to the large loss caused by the transmission transformer 15. of〔.

The present invention has been made in view of these points, and its purpose is to minimize high-frequency leakage to the receiver side when high-frequency power is applied, and to transmit the resonance signal to the receiver with low loss when detecting a resonance signal. The object of the present invention is to realize a transmitting/receiving circuit for a nuclear magnetic resonance apparatus that can transmit data to the other side.

The configuration of the present invention that achieves this objective includes a power amplifier that generates high-frequency power, and a sample placed in a high magnetic field that receives the output of the power amplifier. In a transmitting/receiving circuit of a nuclear magnetic resonance apparatus, which includes a detector that irradiates a single frequency pulse and detects a nuclear magnetic resonance signal, and a receiver that receives the nuclear magnetic resonance signal from the detector, the detector and A gate control circuit composed of a diode, a capacitor, and an inductor is provided between the receiver and the gate control circuit is given control (fi signal to add high-frequency pulses EJJ1j, +J
The operation mode of the gate control circuit is made different depending on when a nuclear magnetic resonance signal is detected, and when a high-frequency pulse is applied, the color tube applied to the receiver is minimized, and when a nuclear magnetic resonance signal is detected, a single resonant signal is generated. It is characterized by being able to transmit the information to the receiver side without loss.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 is an electrical configuration diagram showing an embodiment of the present invention.

In the figure, the same parts as in FIGS. 1 and 2 are given the same reference numerals, and their explanations are omitted. In FIG. 2 is a pulse amplifier that amplifies the output pulse of the timing circuit, and 22 is a gate control circuit that receives the output of the pulse amplifier as a control signal. As shown in the figure, the gate control circuit "t8" is inserted and connected between the detector 2 and the receiver 3, and prevents high frequency leakage from leaking into the receiver 3 side when high frequency power is applied. -I!: Operates to transmit the ringing signal to the receiver 3 side without loss when a resonance signal is detected.The gate/control circuit 22 includes diodes -1"Dl, D2. The output of the pulse amplifier 21 is applied to the connection point between the diodes D+ and D2 via the inductor L2. Also, the die Δ-de D+ is connected from this connection point Δ toward the detector 2 side (in the forward direction), and the die Δ-de D2
is from the connection point △ to the receiver 3 side (J is in the forward direction,
connected to the sea urchin. Also, die A-D1 and condenser +
IC1 is connected in series, tie auto D2 and capacitor C
2 is connected in series, and one end of the inductor 1 is connected to the connection point between the capacitor C1 and the tie auto D+, and the other 9M is grounded.Inductors 1-3 is connected to the connection point of the inductor C2 and the diode D2, and the other end is connected to the inductor "l".
is similarly grounded.

Further, the capacitor C3 has one end connected to the negative end of the inductor L2, and the other end is grounded, and one end of the inductor L2 is grounded at a high frequency.

The operation of the embodiment configured in this way will be described next.

In response to the timing signal generated by the timing circuit 20, the power amplifier 1 is gated by the timing signal and generates high frequency power, which is connected to the pair diode 12.
is supplied to the detector 2 via.

During this time, the pulses generated by the timing circuit 20 are amplified by the pulse amplifier 21 and applied to the gate control circuit 22. As a result of this applied pulse, the diodes Dl and D2 are reverse-biased, and as a result, the control circuit 22 is turned off, and leakage of high-frequency power to the Li device side is prevented.On the other hand, the power amplifier 1 is off and the receiving system is operating, a pulse generated by the timing circuit 20 is amplified by the pulse amplifier 21 and then applied to the gate control circuit 22.This applied pulse causes the diode D to
+, D2 is forward biased, and as a result, the gate control circuit 22 is turned on, and the resonance signal detected by the detector 2 is transmitted to the receiver 3 through the gate control circuit 22. During this resonance signal transmission, the pair tie Δ-dead 12 prevents the resonance signal from leaking to the power amplifier 1 side l\. Note that when the gate control circuit 22 is on, the diodes D+ and D2 are conductive, and the resonance signal from the detector 2 is transmitted through the diodes DI and D? through receiver 3
It is designed to be transmitted to As described above, the pair diode 12 separates the power amplifier 1 and the detector 2 side when the power amplifier 1 is off, and the pair diode 11
1-- protects the receiver 3 by clipping high-level signals such as leakage of high-frequency pulses from the control circuit 22. 3. FIG. 4 is a timing chart showing the operating waveforms of each part of the above embodiment. It is. FIG. 4(A) shows the output waveform of the power amplifier 1, FIG. 4(F) shows the output waveform of the pulse amplifier 21, and FIG. 4(C) shows the waveform of the resonance signal detected by the detector 2. , FIG. 4(d) shows the operating state of the gate control circuit 22,
Figure 4 (small) shows the resonance (g waveform) of the input section of the receiver 3.
In the fi1 circuit 22, if a diode (for example, a bin diode, etc.) whose resistance during forward bias is sufficiently small is used, the high frequency of the gate control circuit 22 when turned off can be controlled. It can be expressed as shown in FIG. 5(a), and further simplified as shown in FIG. 5(b). Here, the inductor Lo in Fig. 5 (1)) is L
t"L3. In FIG. 5(b), by carefully selecting the values of each element of capacitors C+, C2 and inductor Lo to form a high-pass filter, a...i frequency ω0 At frequencies above, parasitic elements such as the LO of the DC bias circuit are transmitted to the detector 2 and the receiver 3.
It is possible to prevent disturbance of the transmission line impedance between the two and to realize a low-loss transmission line with matching characteristic impedance over a wide band, and to prevent a decrease in detection sensitivity. Here, as the fraction of capacitor C+ and C2, 1/ω
R/2ω0 can be taken as the value of oR and inductor Lo. However, C0 is the cutoff frequency of the previous line, and R is the characteristic impedance of the transmission line. In addition, since the gate control circuit 22 is normally switched at high speed, the inductor L.

If the inductance of the continuum υ
By appropriately selecting the values of +, C2, and cutoff frequency ω0, it is possible to reduce the value of Lo and thereby reduce the transient phenomenon.

It should be noted that the gate control circuit 22 may be approximated by a filter circuit other than the T-type filter shown in FIG. 5(b) when it is turned on, and various other filter circuits may be considered. For example, a π-type filter as shown in Figure 3, or a multiple-stage series connection of these T-type and 7-type filters can also be considered. Alternatively, it may have a Butterworth characteristic, a Chebyshev characteristic, or the like. In these cases, the number and arrangement of the ties, capacitors, and inductors of the gate control circuit 22 may be set so that the approximate filter circuit has such various filter characteristics.

As explained above, in the present invention, the parasitic impedance remaining when the gate of the gate control circuit composed of a high frequency low loss diode (bin diode, etc.) and an inductor is in the on state, and external additional elements (inductor, capacitor) are combined. , to match the transmission lines. This eliminates the influence of the transmission line of parasitic elements that occur in the DC bias inductor and diode of the gate control circuit.
A wideband, low-loss transmitter/receiver circuit can be constructed. Furthermore, by incorporating the DC bias inductor, which is a source of harmful transient phenomena such as ringing when the gate control circuit is turned on and off, as an element in the transmission circuit, the value of the inductor can be designed to be small, thereby eliminating the ringing. etc. can be made smaller.

Therefore, when high frequency pulses are applied, the influence of r:i frequency leakage to the receiver side can be minimized, and the obtained resonance signal can be transmitted to the receiver side without loss.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the principle of construction of nuclear magnetic resonance implantation, Fig. 2 is a block diagram showing an embodiment of a conventional transmitting/receiving circuit, and Fig. 3 is a block diagram showing an embodiment of the present invention. An electrical structure, diagram,
Figure 4 is a timing diagram showing the operating waveforms of each part of the circuit in Figure 3, Figure 5 is an isometric circuit diagram of the gate control circuit, and Figure 6 is an isometric diagram of the gate control circuit.
The figure is another equivalent circuit diagram. 1...Power amplifier 2...Detector 3...Receiver 10...λ7/4 cable 1L12...
・Bare diode 13...Coil 14...Transmission line 15・
...Transmission transformer 20...Timing circuit 21...
・Pulse amplifier 22...Gate control circuit C+"C3
... Capacitor D+, D2... Diode 1 to L3. Lo...Inductor patent applicant JEOL Ltd. agent Patent attorney Osamu Tsukishima Figure 1 Figure 2 Figure 2 (b) Figure 3 Figure 4 (Book) 5th cause (Q) (b) Figure 6

Claims (1)

[Claims] A power amplifier that generates high frequency power, a detector that receives the output of the power amplifier and irradiates a sample placed in a high magnetic field with a high frequency pulse and detects a nuclear magnetic resonance signal; A transmitter/receiver circuit for a nuclear magnetic resonance apparatus comprising a receiver for receiving a nuclear magnetic resonance signal from a detector, wherein a gate control circuit is provided between the detector and the receiver and includes a diode, a capacitor, and an inductor. A control signal is provided to the gate control circuit to make the operation mode of the gated ti11 circuit different between when applying a high frequency pulse and when detecting a nuclear magnetic resonance signal, thereby minimizing the influence on the receiver when applying a high frequency pulse. A transmitter/receiver circuit for a nuclear magnetic resonance apparatus, which is characterized in that it is capable of transmitting the resonance signal obtained at the time of nuclear magnetic resonance signal detection to the receiver side without loss.