Tuning device for receiving coil, cryogenic probe, and magnetic resonance device
Embodiments of the present disclosure provides a tuning device for a receiving coil, a cryogenic probe, and a magnetic resonance device. The tuning device may include a fixed capacitor, a varactor assembly, and a control assembly. The fixed capacitor and the coil may be connected in series. The varactor assembly may be connected in parallel to both ends of the fixed capacitor. The control assembly may be configured to control the capacitance of the receiving coil by controlling the capacitance value of the varactor assembly to perform a tuning operation on the receiving coil, the tuning operation including at least one of a frequency tuning and an impedance tuning.
1 . A cryogenic probe, the cryogenic probe including a receiving coil and a tuning device for a receiving coil, the tuning device comprising:
a fixed capacitor, a varactor assembly, and a control assembly; wherein
the control assembly is configured to perform a tuning operation on the receiving coil by controlling a capacitance value of the varactor assembly, the tuning operation including at least one of a frequency tuning or an impedance tuning;
the fixed capacitor includes a first fixed capacitor and a second fixed capacitor, and the varactor assembly includes a first varactor assembly and a second varactor assembly;
the first varactor assembly and the first fixed capacitor are configured to achieve a frequency tuning on the receiving coil;
the second varactor assembly and the second fixed capacitor are configured to achieve an impedance tuning on the receiving coil; and
the combination of the first varactor assembly and the first fixed capacitor, the combination of the second varactor assembly and the second fixed capacitor, and the receiving coil are connected in series.
2 . A magnetic resonance device, including a cryogenic probe, wherein the cryogenic probe includes a receiving coil and a tuning device for the receiving coil, and the tuning device for the receiving coil comprises:
a fixed capacitor, a varactor assembly, and a control assembly; wherein
the control assembly is configured to perform a tuning operation on the receiving coil by controlling a capacitance value of the varactor assembly, the tuning operation including at least one of the frequency tuning or the impedance tuning;
the fixed capacitor includes a first fixed capacitor and a second fixed capacitor, and the varactor assembly includes a first varactor assembly and a second varactor assembly;
the first varactor assembly and the first fixed capacitor being configured to achieve a frequency tuning on the receiving coil;
the second varactor assembly and the second fixed capacitor being configured to achieve an impedance tuning on the receiving coil; and
the combination of the first varactor assembly and the first fixed capacitor, the combination of the second varactor assembly and the second fixed capacitor, and the receiving coil are connected in series.
3 . The cryogenic probe of claim 1 , wherein
the control assembly includes a power supply for outputting a voltage to the varactor assembly; and
the control assembly is configured to adjust the capacitance value of the varactor assembly to a target capacitance value by changing a magnitude of the voltage output from the power supply.
4 . The cryogenic probe of claim 1 , wherein the control assembly includes a first power supply and a second power supply, the first power supply being connected to the first varactor assembly through a first coaxial cable, and the second power supply being connected to the second varactor assembly through a second coaxial cable.
5 . The cryogenic probe of claim 1 , wherein the tuning device further includes a first inductor connected in parallel to the first fixed capacitor.
6 . The cryogenic probe of claim 1 , wherein the device further includes a parallel resonance circuit connected in parallel to the receiving coil, the parallel resonance circuit being configured to control the receiving coil to be in a detuned state or a tuned state.
7 . The cryogenic probe of claim 1 , wherein the first varactor assembly includes a first adjustable capacitor, the second varactor assembly includes a second adjustable capacitor, the control assembly includes a first control assembly, a second control assembly, a first connecting member, and a second connecting member, wherein
the first control assembly is configured to adjust a capacitance value of the first adjustable capacitor by controlling the first connecting member to link an adjustable member of the first adjustable capacitor, so as to perform the frequency tuning on the receiving coil; and
the second control assembly is configured to adjust a capacitance value of the second adjustable capacitor by controlling the second connecting member to link an adjustable member of the second adjustable capacitor, so as to perform the impedance tuning on the receiving coil.
8 . The cryogenic probe of claim 1 , wherein the first varactor assembly includes a first adjustable capacitor, the second varactor assembly includes a second adjustable capacitor, the control assembly includes a first control assembly and a second control assembly,
the first control assembly is configured to adjust a first capacitance value of the first adjustable capacitor such that a first reflection coefficient curve corresponding to the first adjustable capacitor satisfies a first preset condition of the frequency tuning; and
the second control assembly is configured to adjust a second capacitance value of the second adjustable capacitor such that a second reflection coefficient curve corresponding to the second adjustable capacitor satisfies a second preset condition of the impedance tuning.
9 . The cryogenic probe of claim 1 , wherein the first varactor assembly is connected in parallel to both ends of the first fixed capacitor, and the second varactor assembly is connected in parallel to both ends of the second fixed capacitor.
10 . The cryogenic probe of claim 1 , wherein
the tuning device further includes a third fixed capacitor, the third fixed capacitor being connected in series between the combination of the first varactor assembly and the first fixed capacitor and the combination of the second varactor assembly and the second fixed capacitor, the third fixed capacitor serves as a direct current (DC) blocking capacitor or a frequency tuning capacitor of the receiving coil.
11 . The cryogenic probe of claim 1 , wherein
the tuning device further includes a third fixed capacitor, the third fixed capacitor being connected in series between the receiving coil and the combination of the first varactor assembly and the first fixed capacitor, the third fixed capacitor serves as a direct current (DC) blocking capacitor or a frequency tuning capacitor of the receiving coil.
12 . The cryogenic probe of claim 3 , wherein the control assembly is further configured to determine the target capacitance value based on at least one of a resonant frequency of the receiving coil or a target output impedance of the receiving coil.
13 . The cryogenic probe of claim 8 , wherein the first preset condition includes that a sweep frequency corresponding to a lowest point of the first reflection coefficient curve is within a preset frequency range.
14 . The cryogenic probe of claim 8 , wherein to adjust a first capacitance value of the first adjustable capacitor such that a first reflection coefficient curve corresponding to the first adjustable capacitor satisfies a first preset condition of the frequency tuning, the first control assembly is configured to:
update the first capacitance value of the first adjustable capacitor by adjusting a first voltage applied to the first adjustable capacitor;
determine whether the first reflection coefficient curve corresponding to the updated first capacitance value satisfies the first preset condition of the frequency tuning;
in response to determining that the first reflection coefficient curve does not satisfy the first preset condition, continue to adjust the first voltage to further update the first capacitance value; or in response to determining that the first reflection coefficient curve satisfies the first preset condition, stop adjusting the first voltage.
15 . The cryogenic probe of claim 8 , wherein to adjust a second capacitance value of the second adjustable capacitor such that a second reflection coefficient curve corresponding to the second adjustable capacitor satisfies a second preset condition of the impedance tuning, the second control assembly is configured to:
update the second capacitance value of the second adjustable capacitor by adjusting a second voltage applied to the second adjustable capacitor;
determine whether the second reflection coefficient curve corresponding to the updated second capacitance value satisfies the second preset condition of the impedance tuning;
in response to determining that the second reflection coefficient curve does not satisfy the second preset condition, continue to adjust the second voltage to further update the second capacitance value; or in response to determining that the second reflection coefficient curve satisfies the second preset condition, stop adjusting the second voltage.
16 . The cryogenic probe of claim 4 , wherein
the first coaxial cable includes a first inner core and a first outer conductor, and the second coaxial cable includes a second inner core and a second outer conductor;
a positive pole of the first power supply is connected to a negative pole of the first varactor assembly through the first inner core of the first coaxial cable, and a negative pole of the first power supply is connected to a positive pole of the first varactor assembly through the first outer conductor of the first coaxial cable;
a positive pole of the second power supply is connected to a negative pole of the second varactor assembly through the second inner core of the second coaxial cable, and a negative pole of the second power supply is connected to a second positive pole of the second varactor assembly through the second outer conductor of the second coaxial cable.
17 . The device cryogenic probe of claim 14 , wherein to determine whether the first reflection coefficient curve corresponding to the updated first capacitance value satisfies the first preset condition of the frequency tuning, the first control assembly is configured to:
obtain a sweep reflection coefficient curve generated after the receiving coil is swept, the sweep reflection coefficient curve including reflection coefficients of the receiving coil at different sweep frequencies;
generate the first reflection coefficient curve corresponding to the updated first capacitance value by updating, based on the updated first capacitance value, the sweep reflection coefficient curve; and
determine whether the first reflection coefficient curve satisfies the first preset condition of the frequency tuning.
18 . The cryogenic probe of claim 15 , wherein to determine whether the second reflection coefficient curve corresponding to the updated second capacitance value satisfies the second preset condition of the impedance tuning, the second control assembly is configured to:
update one or more reflection coefficients of one or more plotted points in the first reflection coefficient curve based on the updated second capacitance value to generate the second reflection coefficient curve corresponding to the updated second capacitance value; and
determine whether the second reflection coefficient curve and the second voltage satisfy the second preset condition of the impedance tuning.
19 . The cryogenic probe of claim 15 , wherein to update the second capacitance value of the second adjustable capacitor by adjusting a second voltage applied to the second adjustable capacitor, the second control assembly is configured to:
determine an initial upper limit voltage, an initial lower limit voltage, and an initial matching voltage based on a preset upper limit value and a preset lower limit value of the second voltage;
generate an updated matching voltage by updating the initial matching voltage based on an updated first reflection coefficient curve corresponding to each of the initial upper limit voltage, the initial lower limit voltage, and the initial matching voltage; and
adjust the second voltage based on the updated matching voltage to update the second capacitance value.
20 . The cryogenic probe of claim 19 , wherein the second preset condition includes that: a lowest point in a second reflection coefficient curve corresponding to a matching voltage at a current moment is less than a first preset value, and an absolute value of a difference between the matching voltage at the current moment and a matching voltage at a last moment is less than a second preset value.