CN207164229U

CN207164229U - A kind of radio-frequency coil

Info

Publication number: CN207164229U
Application number: CN201720595852.9U
Authority: CN
Inventors: 杨培强; 方智奇; 徐罗元; 沈杰; 陆治勇; 汪红志
Original assignee: Suzhou Niumag Electronic Technology Co Ltd
Current assignee: Suzhou Niumag Electronic Technology Co Ltd
Priority date: 2017-05-26
Filing date: 2017-05-26
Publication date: 2018-03-30
Anticipated expiration: 2027-05-26

Abstract

It the utility model is related to a kind of radio-frequency coil, active switch circuit is internally integrated in coil, overcome the problem of oscillation energy and useful RF energy being present in the next passive coil of the big resistive band of passive Diode series while being consumed, the problem of avoiding the vibration less than diode cut-in voltage not consume simultaneously, reach the purpose for shortening radio-frequency coil duration of oscillation.

Description

A kind of radio-frequency coil

Technical field

It the utility model is related to a kind of radio-frequency coil, category nuclear magnetic resonance field.

Background technology

Effect of the radio-frequency coil in magnetic resonance system is receiving and transmitting signal, that is, launches high-power RF pulse signal and reception Extremely low power nuclear magnetic signal.Since transmitting be accomplished to can receive nuclear magnetic signal time be referred to as the dead time.Dead time Producing reason is, after radio-frequency coil has launched high-power RF pulse signal, because coil is in a resonance circuit, RF energy on coil will not be reduced to 0 immediately, but vibration consumption slowly is changed into 0, and the duration of oscillation is typically not less than 16 μ s.In this duration of oscillation, the signal that coil externally exports is made up of oscillation energy and nuclear magnetic signal energy, both frequency phases Together, and oscillation energy is far longer than nuclear magnetic signal energy, receive the maximal input that bears of function, therefore this also greater than rear class Signal in the section time is needed to filter out, but nuclear magnetic signal useful in the time simultaneously is also filtered out.The length in dead time It is short to affect the systematic difference field, especially for the sample that the relaxation time is very short, such as hard fat, it is necessary to magnetic resonance system There is the very short dead time, otherwise relaxation is complete in the system dead time for nuclear magnetic signal caused by sample, and system just receives Less than the signal of the sample.

In conventional RF coil, the dead time is shortened using the method for the one big resistance of passive Diode series, it is former Reason is in duration of oscillation, and larger oscillation energy can turn on passive diode, forms path with big resistance, is put by resistance Electricity.The limitation of this method is：（1）Within the radio-frequency transmissions time, passive diode can be also switched on, quite a few useful radio frequency Energy has also been consumed on resistance, causes coil efficiency to decline；（2）While oscillation energy is consumed, useful radio-frequency power Signal is also consumed；（3）When the amplitude of oscillating voltage is less than the cut-in voltage of diode（It is generally acknowledged that 0.7V）Afterwards, the structure is not It is effective again, and now oscillator signal is still much larger than nuclear magnetic signal；（4）The temperature of resistance is usually very high so that resistance burn out or The scolding tin at both ends melts.Therefore for this method from the point of view of theory analysis to actual use, effect is not fine.

Binary channels coil is also made to solve dead time problem, i.e. transmitting coil and receiving coil separates, shorter to obtain Coil duration of oscillation.But binary channels coil has serious coupled problem, the vibration of transmitting coil can be coupled to receiving coil, shake It is basically identical to swing the coil of time and transceiver, and binary channels coil can cause workload to double in debugging.

Therefore how to overcome and oscillation energy be present in the passive coil that the big resistive band of passive Diode series comes and useful penetrate The problem of frequency energy is consumed simultaneously, while the problem of avoid the vibration less than diode cut-in voltage from not consuming, turn into this The difficult point of area research.

The content of the invention

The utility model is to solve the problems, such as that prior art is present, there is provided a set of shortening radio-frequency coil duration of oscillation Solution, this scheme are internally integrated active switch circuit in coil, overcome the big resistive band of passive Diode series passive The problem of oscillation energy and useful RF energy in coil being present while being consumed, while avoid less than diode cut-in voltage The problem of vibration can not consume.

The purpose of this utility model is realized by following measures：

The radio-frequency coil includes the first electric capacity, the second electric capacity, the 3rd electric capacity, the 4th electric capacity, the first inductance coil and master Dynamic on-off circuit.

3rd electric capacity and the 4th electric capacity earth, and connected with second electric capacity, then again with it is described First inductance coil is in parallel；The active switch circuit is connected with the first inductance coil.

The active switch circuit, including can generating positive and negative voltage biasing dc source, the first PIN diode, the 2nd PIN bis- Pole pipe and the second inductance coil, first PIN diode and the second PIN diode earth, and with the second inductance coil Series connection；

When first inductance coil is in emission state, by the dc source provide positive voltage bias, first PIN diode, the second PIN diode are in fully on state, equivalent to one wire, when the moment that emission state terminates, The dc source provides negative voltage bias, the first PIN diode, the cut-off of the second PIN diode, equivalent to one resistance, original Resonant tank is destroyed, and the equivalent resistance that the energy in coil is connected in resonant tank consumes rapidly, and vibration runs out of Afterwards, dc source is changed into positive voltage, and the first PIN diode, the second PIN diode turn on again, and coil switchs to reception state.

The dc source includes the chip of adjustment waveform, and the chip has PWR output ends and AUX output ends, and two defeated Go out end can separately adjustable rising edge, trailing edge and input signal delay, the PWR signals and AUX signals of output respectively enter light Electric coupler, front and rear control signal is mutually isolated, and the signal after isolating enters the metal-oxide-semiconductor with positive and negative logic output and driven Dynamic device, the output signal of driver drive the metal-oxide-semiconductor grid of direct current gating circuit below.

For 0.8A constant currents and -15V constant-voltage DC sources outside the direct current gating circuit, when outside gate-control signal provides During low level, PWR and AUX signals are also all low level, now circuit output 0.8A constant currents；And when gate-control signal is high level When, what PWR signals and AUX signals provided is high level, now circuit output -15V.

The metal-oxide-semiconductor is divided into NMOS tube and PMOS, and the NMOS voltages can load ± 20V, opens the turn-off time 10 ~30ns, the PMOS continuous output current are 2A, and maximum impulse output current is 10A, open the turn-off time 10~ 50ns。

The unaccounted technical characteristic of the utility model is carried out supporting using ripe prior art.

The utility model has the following advantages that compared with prior art：

1st, the utility model provides a kind of radio-frequency coil, will with different direct current biasings according to the different sequential stages Coil is placed in different conditions, avoids oscillation energy present in passive coil and useful RF energy while what is be consumed ask Topic, while the problem of the vibration that it also avoid less than diode cut-in voltage can not consume.

Brief description of the drawings

Fig. 1 is coil circuit design of the present utility model.

Fig. 2 is circuit power design frame chart of the present utility model.

Fig. 3 is UC3714 gating delays schematic diagram of the present utility model.

Fig. 4 is electric current gating circuit schematic diagram of the present utility model.

Fig. 5 is coil circuit power supply way circuit figure of the present utility model.

Fig. 6 is the concussion oscillogram of conventional passive coil circuit.

Fig. 7 is the waveform figure of coil circuit of the utility model with active switch.

Embodiment

This method is described in further detail below in conjunction with the drawings and specific embodiments.

Embodiment：

A kind of design of radio-frequency coil circuit is as shown in Figure 1.In the circuit, C1, C2, C3, C4, L1 are primary coil Circuit, C1 are matching capacitances, C2, C3, C4 and L1 be tuned to required for resonance point, L1 is coil.

The coil circuit is provided with active switch circuit, and the principle of active switch circuit is, when coil is in emission state, PIN diode D1, D2 add positive bias by VCC, and in fully on state, D1, D2 are equivalent to a wire in theory, whole Individual coil circuit state is consistent with former passive coil.When the moment that emission state terminates is, it is necessary to fast by the oscillation energy in coil Speed is consumed, and now VCC provides negative voltage bias, D1, D2 cut-off, and equivalent to one resistance, resonant tank originally is destroyed, The equivalent resistance that energy in coil is connected in resonant tank consumes rapidly, and after vibration runs out of, VCC is changed into positive electricity Pressure, D1, D2 are turned on again, and coil switchs to reception state.

PIN diode is using model MA4P506-1072T import device, the power appearance of the diode in this example Amount is very big, and ON time is short, conducting resistance is small, in similar volume production product of its related keyword index on current world market Belong to first-class.For the switch time of diode, actual measurement can be accomplished within 3 μ s, can meet to require.

The total design frame chart of coil circuit power control circuit is as shown in Figure 2.

The gate-control signal that board provides first by UC3714 chips adjust waveform, as shown in figure 3, UC3714 have two it is defeated Go out end, be PWR outputs and AUX outputs respectively, two output ends can prolonging with separately adjustable rising edge, trailing edge and input signal Late, time delay is typically in tens nanoseconds.The purpose of regulation delay is to make the gate-control signal of input direct-current gating circuit below In the presence of a small time difference, avoid the occurrence of two-way power supply and meanwhile output and caused by short circuit phenomenon.The PWR letters of UC3714 outputs Number and AUX signals respectively enter photoelectrical coupler first, it is therefore an objective to front and rear control signal is mutually isolated, the letter after isolating Number enter metal-oxide-semiconductor driver, the output signal of driver can drive the metal-oxide-semiconductor grid of direct current gating circuit below.Metal-oxide-semiconductor drives That dynamic device selects is TI UCC27517A-Q1, and it is a MOS driver with positive and negative logic output, in order to meet high electricity 0.8A constant currents are usually exported, output -15V constant pressures during low level, by MOS drivers all anti-phase outputs of two.

Direct current gating circuit supplies 0.8A constant currents and -15V constant-voltage DC sources outside needing.When outside gate-control signal provides low electricity Usually, PWR and AUX signals are also all low level, and now NMOS tube Q2 is not turned on, and causes Q3 to be also not turned on, and Q1 is conducting, Now circuit output 0.8A constant currents；And when gate-control signal is high level, what PWR signals and AUX signals provided is high level, this When Q2 turn on, R5 and R6 form path, and R6 both ends produce partial pressure, cause Q3 to turn on, Q1 is what is be not turned on, therefore now circuit Output -15V.

NMOS tube uses BSS138, and voltage can load ± 20V, satisfaction -15V requirement, open the turn-off time 10~ Between 30ns.PMOS uses FDN340P, and its continuous output current is 2A, and maximum impulse output current is 10A, meets 0.8A The requirement of constant current, the turn-off time is opened between 10~50ns.

The power control circuit design of T/R switches uses the design essentially identical with coil energy consuming circuitry power supply, simply line The current source designs of positive electricity are needed to be changed to the voltage source design of T/R switches in circle, and offer ± 5V two is needed outside T/R Switching Power Supplies Voltage, the design of the power control circuit repeat no more.

Total T/R switching power source control circuits are as shown in Figure 5.LM317 voltage stabilizings are all employ at each voltage, remove ripple.

Silicone oil has been selected in experiment, and as sample, coil uses the coil with active switch circuit mentioned above, and Conventional passive coil.Coil is connected in whole MR system, but the output signal of coil is switched directly by passive T/R It is sent into oscillograph observation duration of oscillation.

Fig. 6 is the waveform of conventional passive coil circuit, it can be seen that actual waveform has continueed to more than 13 μ s. Nuclear magnetic signal has the process of a rising after vibration terminates, and the uphill process makes the time that useful nuclear magnetic signal is received Delay, the process vibrates mainly due to coil makes greatly very much preamplifier saturation, and preposition fan-out capability is pressed down after saturation System is, it is necessary to the recovery process of a period of time.

Fig. 7 is the waveform of the coil circuit with active switch, it can be seen that vibration just finishes within 8 μ s, And entirely waveform is small compared to passive coil, this reduces the impact to preposition amplification, does not make preposition amplification Device saturation, the concussion time is on the one hand shortened, on the one hand eliminate the process of amplifier saturation recovery, so as to which useful nuclear-magnetism be believed Number time point that can be received shifts to an earlier date, while also improves reliability.

Although the utility model is disclosed as above with preferred embodiment, they be not for limiting the utility model, It is any to be familiar with this area technical professional, in the spirit and scope for not departing from the utility model, it can make various simply to repair Change, equivalent variations, still fall within the protection domain of technical solutions of the utility model.

Claims

A kind of 1. radio-frequency coil, it is characterised in that：

The radio-frequency coil includes the first electric capacity, the second electric capacity, the 3rd electric capacity, the 4th electric capacity, the first inductance coil and actively opened Powered-down road, the 3rd electric capacity and the 4th electric capacity earth, and connected with second electric capacity, then again with described One inductance coil is in parallel；The active switch circuit is connected with the first inductance coil, and the active switch circuit includes can be positive and negative The dc source of voltage bias, the first PIN diode, the second PIN diode and the second inductance coil, the poles of the first PIN bis- Pipe and the second PIN diode earth, and connected with the second inductance coil；

When first inductance coil is in emission state, positive voltage bias, the first PIN bis- are provided by the dc source Pole pipe, the second PIN diode are in fully on state, equivalent to one wire, described straight when the moment that emission state terminates Flow power supply and negative voltage bias, the first PIN diode, the cut-off of the second PIN diode, equivalent to one resistance, former resonance time are provided Road is destroyed, and the first PIN diode that the energy in coil is connected in resonant tank, the second PIN diode consume rapidly, After vibration runs out of, dc source is changed into positive voltage, and the first PIN diode, the second PIN diode turn on again, and coil turns For reception state.
2. radio-frequency coil according to claim 1, it is characterised in that：

The dc source includes the chip of adjustment waveform, and the chip has PWR output ends and AUX output ends, two output ends Can separately adjustable rising edge, trailing edge and input signal delay, the PWR signals and AUX signals of output respectively enter photoelectricity coupling Clutch, front and rear control signal is mutually isolated, and the signal after isolating enters the metal-oxide-semiconductor driving with positive and negative logic output Device, the output signal of driver drive the metal-oxide-semiconductor grid of direct current gating circuit below.
3. radio-frequency coil according to claim 2, it is characterised in that：

For 0.8A constant currents and -15V constant-voltage DC sources outside the direct current gating circuit, when outside gate-control signal provides low electricity Usually, PWR and AUX signals are also all low level, now circuit output 0.8A constant currents；And when gate-control signal is high level, PWR What signal and AUX signals provided is high level, now circuit output -15V.