A self-excited self-induction coil and its working method

Abstract

The application relates to a self-excited self-receiving coil, which comprises a transmission line structure and a reference layer switching circuit, one end of the transmission line structure is connected with a radio frequency signal input end through a first T / R switch, the other end is grounded through a second T / R switch and a matching resistance; one end of the transmission line structure is also connected with a second radio frequency signal output end through a fourth T / R switch, the other end is connected with a first radio frequency signal output end through a third T / R switch; the transmission line structure comprises a coil winding, a reference layer is arranged outside the coil winding; a dielectric layer is arranged between the reference layer and the coil winding, the dielectric layer is used for controlling the characteristic impedance between the reference layer and the coil winding, so that the characteristic impedance is matched with the impedance of the input end and the matching resistance; the reference layer switching circuit is connected with the reference layer and is used for controlling the ground impedance of the reference layer. The application makes the coil respectively show the transmission line characteristic and the single inductance characteristic during the transmission and the reception.

Description

Technical Field

[0001] This invention relates to the field of magnetic resonance coil technology, and in particular to a self-generating and self-receiving coil and its operating method. Background Technology

[0002] As an important component of a magnetic resonance system, a magnetic resonance coil can generally be divided into a transmitting coil and a receiving coil. The transmitting coil is used to generate a radio frequency field of a certain intensity in a specific space to excite the sample; the receiving coil is used to detect the magnetic resonance signal generated by the sample. At present, most of the transmitting and receiving coils used in magnetic resonance systems are designed based on the LC tuning principle. Since the spectral width of such LC-tuned coils is generally narrow, there are several limitations when detecting samples with a wide spectral line: (1) Due to the narrow bandwidth of the coil, multiple different coil circuits need to interact to extend the detection frequency band. This not only makes the circuit and structure very complex, but also requires manual tuning within its limited bandwidth for each experiment, resulting in low efficiency. (2) Since the Q value of the coil circuit is different at different frequency points, the acquired signals are not easy to compare directly and signal normalization is required. (3) Since the coil at each frequency point needs to be tuned separately, such coils based on LC tuning circuits are difficult to apply to applications that require rapid changes in the center frequency.

[0003] For the reasons mentioned above, designing a magnetic resonance coil capable of covering a wide frequency range is crucial for the study and detection of broadband samples. Currently, the following approaches exist for the research of such broadband magnetic resonance coils:

[0004] I. Single Inductor Coil

[0005] A single-inductor coil uses only a single inductor for both radio frequency (RF) transmission and signal reception. It offers advantages such as simple structure, wide detection frequency range, and high Q value. However, because the inductor's impedance increases with the operating frequency, to ensure consistency in the RF field magnitude at different frequencies during transmission (while maintaining a constant current in the coil), the output voltage at the drive end needs to be increased accordingly when exciting samples at higher frequencies. This impedance mismatch in power output also causes significant power reflection, placing high demands on the RF power amplifier's driving capability and significantly reducing the coil's transmission efficiency. Therefore, the use of single-inductor coils has certain limitations in both existing commercial NMR systems and broadband systems.

[0006] II. Transmission Line Coil

[0007] A transmission line typically consists of a core wire, a dielectric layer, and a reference layer. It is a widely used device in radio frequency (RF) applications for signal transmission. Its advantage lies in its ability to transmit RF signals of any frequency without attenuation or reflection when the matching resistor impedance at the load end and the source impedance are matched to the characteristic impedance of the transmission line. Using a transmission line as a magnetic resonance coil offers the advantage of achieving impedance matching over a wide frequency range, thus ensuring the consistency of the RF field at different frequencies. However, because a matching resistor is required at the termination of the transmission line coil, and this resistor generates significant thermal noise, the signal-to-noise ratio (SNR) of the output signal at both ends will be significantly reduced when the transmission line coil is used for signal reception.

[0008] To improve transmission efficiency and receiver signal-to-noise ratio (SNR), a separate transmit / receive coil design can be considered. The transmission line coil is designed as the transmitting coil to ensure consistent RF field strength over a wide frequency range, while a single inductor coil is designed as the receiving coil. This, combined with a high-input-impedance preamplifier, achieves a lower noise figure. However, this separate transmit / receive coil design requires the single inductor coil to be designed inside the transmission line coil and placed close to the sample to improve the SNR. For magnetic resonance spectroscopy systems with limited sample space, this structure not only increases the design complexity of the transmit and receive coils but also increases the distance between the sample and the transmitting coil, reducing transmission efficiency. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a self-transmitting and self-receiving coil and its working method, so that the coil exhibits transmission line characteristics and single inductor characteristics during transmission and reception, respectively.

[0010] The technical solution adopted by this invention to solve its technical problem is as follows: A self-transmitting and self-receiving coil is provided, comprising a transmission line structure and a reference layer switching circuit. One end of the transmission line structure is connected to the radio frequency signal input terminal through a first T / R switch, and the other end is grounded through a second T / R switch and a matching resistor. One end of the transmission line structure is also connected to a second radio frequency signal output terminal through a fourth T / R switch, and the other end is connected to a first radio frequency signal output terminal through a third T / R switch. The transmission line structure includes a coil, and a reference layer is disposed outside the coil winding. A dielectric layer is disposed between the reference layer and the coil winding, and the dielectric layer is used to control the characteristic impedance between the reference layer and the coil winding, so that the characteristic impedance matches the impedance of the input terminal and the impedance of the matching resistor. The reference layer switching circuit is connected to the reference layer and is used to control the impedance of the reference layer to ground.

[0011] The coil winding can be in the form of a solenoid, a planar coil, or a coaxial core wire.

[0012] The reference layer can be cylindrical, linear, a coaxial shielding layer, or planar.

[0013] The reference layer switching circuit includes a first switching device and a second switching device, the first switching device being connected to the second switching device; the end of the first switching device not connected to the second switching device being connected to a gate control drive terminal; the end of the second switching device not connected to the first switching device being grounded; and the reference layer being connected at the connection point between the first switching device and the second switching device.

[0014] A capacitor is also connected in parallel across the two ends of the first and second switching devices.

[0015] The first switching device and the second switching device are field-effect transistors, transistors, diodes, PIN diodes, or relays.

[0016] A current-limiting resistor is also provided between the end of the first switching device that is not connected to the second switching device and the gate control drive end.

[0017] The matching resistor can be a through-hole resistor, a surface mount resistor, a wire-wound resistor, or a PCB trace resistor.

[0018] The technical solution adopted by the present invention to solve its technical problem is as follows: A method for operating the aforementioned self-transmitting and self-receiving coil is provided. When the self-transmitting and self-receiving coil is in the transmitting state, the first T / R switch and the second T / R switch are in the conducting state; the third T / R switch and the fourth T / R switch are in the off state; and the reference layer switching circuit makes the reference layer and ground present a low-resistance state. When the self-transmitting and self-receiving coil is in the receiving state, the first T / R switch and the second T / R switch are in the off state; the third T / R switch and the fourth T / R switch are in the conducting state; and the reference layer switching circuit makes the reference layer and ground present a high-resistance state.

[0019] Beneficial effects

[0020] By employing the above-mentioned technical solution, this invention has the following advantages and positive effects compared with the prior art: This invention, by changing the ground impedance of the transmission line coil reference layer, enables it to achieve good broadband impedance matching in the transmission state and high Q value and low noise in the receiving state, thus achieving transmission line characteristics in the transmission state and single-inductor coil characteristics in the receiving state. This invention is fully compatible with existing commercial 50Ω broadband RF power amplifiers, enabling broadband magnetic resonance RF excitation. Compared with a single inductor coil, this invention can achieve good impedance matching in the transmission state, thereby overcoming the transmission impedance mismatch problem of a single inductor coil. Compared with using a transmission line coil directly as a receiving coil, this invention has a higher Q value and a lower noise figure in the receiving state, significantly improving the coil's receiving signal-to-noise ratio performance and overcoming the problems of high thermal noise and low receiving signal-to-noise ratio when using a transmission line coil directly as a receiving coil. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the transmission line structure in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the reference layer switching circuit in an embodiment of the present invention. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0025] Embodiments of the present invention relate to a self-transmitting and self-receiving coil, which can exhibit the characteristics of a transmission line coil in the transmitting state and the characteristics of a single inductor coil in the receiving state. For example... Figure 1As shown, it mainly consists of a transmission line structure, a reference layer switching circuit, a matching resistor, and T / R switches. One end A of the coil winding COIL in the transmission line structure is connected to the RF signal input terminal PORTA through a first T / R switch S1, and the other end B is grounded through a second T / R switch S2 and a matching resistor Z1. One end A of the coil winding COIL in the transmission line structure is also connected to the second RF signal output terminal PORTC through a fourth T / R switch S4, and the other end B is connected to the first RF signal output terminal PORTB through a third T / R switch S3. The reference layer switching circuit SW1 is connected to the reference layer REF in the transmission line structure. The four T / R switches are used to control the direction of the signal from the self-transmitting and self-receiving coil. When the self-transmitting and self-receiving coil is in the transmitting state, the first T / R switch S1 and the second T / R switch S2 are in the conducting state; the third T / R switch S3 and the fourth T / R switch S4 are in the cut-off state. When the coil is in the receiving state, the first T / R switch S1 and the second T / R switch S2 are in the off state; the third T / R switch S3 and the fourth T / R switch S4 are in the on state.

[0026] The transmission line structure in this embodiment is as follows: Figure 2 As shown, the device includes a coil winding (COIL), with a reference layer (REF) disposed outside the COIL. A dielectric layer is disposed between the reference layer (REF) and the coil winding, and the dielectric layer is used to control the characteristic impedance between the reference layer and the coil winding. In this embodiment, the coil winding (COIL) is wound into a solenoid shape, and the reference layer (REF) is cylindrical. Figure 2 (This is a cross-sectional view of the transmission line structure coil). The dielectric layer 3 is used to adjust the characteristic impedance between the coil winding 1 and the cylindrical reference layer 2. This characteristic impedance value should match the impedance of the input terminal impedance and the terminating resistance, including but not limited to 50Ω, 75Ω, etc. It is worth mentioning that the transmission line structure in this embodiment can also adopt other forms. For example, when the transmission line structure is a parallel two-wire form, the coil winding COIL is one wire, and the reference layer REF is the other wire; when the transmission line structure is a coaxial line, the coil winding COIL is the core wire of the coaxial line, and the reference layer REF is the shielding layer of the coaxial line. The transmission line structure in this embodiment includes, but is not limited to, parallel two-wire, parallel multi-wire, coaxial line, stripline, microstrip line, etc.

[0027] In this embodiment, the reference layer switching circuit SW1 is used to change the ground impedance of the transmission line reference layer. The operating logic of the reference layer switching circuit is as follows: when the self-generating and self-receiving coil needs to present a good impedance matching state over a wide bandwidth, the reference layer switching circuit is turned on, thereby presenting a low impedance state between the reference layer REF and ground; when the self-generating and self-receiving coil needs to present low noise and a high Q value over a wide bandwidth, the reference layer switching circuit is turned off, thereby presenting a high impedance state between the reference layer REF and ground.

[0028] like Figure 3 As shown, the reference layer switching circuit in this embodiment includes a first switching device D1 and a second switching device D2, with the first switching device D1 connected to the second switching device D2. The end of the first switching device D1 not connected to the second switching device D2 is connected to the gate control driver TRIG via a current-limiting resistor R1. The end of the second switching device D2 not connected to the first switching device D1 is grounded. The reference layer REF is connected at the junction of the first switching device D1 and the second switching device D2. A DC-blocking and AC-passing capacitor C1 is also connected in parallel across the connected ends of the first switching device D1 and the second switching device D2. When the signal received by the gate control driver TRIG is high, the first switching device D1 and the second switching device D2 are turned on. At this time, the reference layer REF is in a low-impedance state with ground. When the signal received by the gate control driver TRIG is low, the first switching device D1 and the second switching device D2 are turned off. At this time, the reference layer REF is in a high-impedance state with ground. In this embodiment, both the first and second switching devices are implemented using diodes. It is worth mentioning that the switching devices can also be field-effect transistors, transistors, PIN diodes, or relays. The TRIG gate can be driven by a voltage source or a current source.

[0029] In this embodiment, the matching resistor Z1 is used to provide termination impedance matching for the transmission line structure when the reference layer switching circuit presents a low impedance state. The matching resistor Z1 includes, but is not limited to, through-hole resistors, surface mount resistors, wire-wound resistors, PCB trace resistors, etc.

[0030] It is readily apparent that this invention is fully compatible with existing commercial 50Ω broadband RF power amplifiers, enabling broadband magnetic resonance RF excitation. Utilizing a reference layer switching circuit, the coil exhibits transmission line characteristics during transmission and single-inductor characteristics during reception, achieving reflection-free RF excitation and efficient, low-noise RF reception. Compared to single-inductor coils, this invention achieves excellent impedance matching in the transmission state, overcoming the impedance mismatch problem inherent in single-inductor coils. Compared to transmission line coils, this invention exhibits a higher Q value and lower noise figure in the reception state, improving the coil's signal-to-noise ratio (SNR) and overcoming the high thermal noise and low SNR issues associated with transmission line coils.

Claims

1. A self-generating self-receiving coil, characterized by, The system includes a transmission line structure and a reference layer switching circuit. One end of the transmission line structure is connected to the RF signal input terminal via a first T / R switch, and the other end is grounded via a second T / R switch and a matching resistor. One end of the transmission line structure is also connected to a second RF signal output terminal via a fourth T / R switch, and the other end is connected to a first RF signal output terminal via a third T / R switch. The transmission line structure includes a coil winding, with a reference layer disposed outside the coil winding. A dielectric layer is disposed between the reference layer and the coil winding, and this dielectric layer controls the characteristic impedance between the reference layer and the coil winding, ensuring that the characteristic impedance matches the input terminal impedance and the matching resistor impedance. The reference layer switching circuit is connected to the reference layer and controls the reference layer's impedance to ground.

2. The self-generating self-receiving coil of claim 1, wherein, The coil winding can be in the form of a solenoid, a planar coil, or a coaxial core wire.

3. The self-generating self-receiving coil of claim 1, wherein, The reference layer can be cylindrical, linear, a coaxial shielding layer, or planar.

4. The self-generating self-receiving coil of claim 1, wherein, The reference layer switching circuit includes a first switching device and a second switching device, the first switching device being connected to the second switching device; the end of the first switching device not connected to the second switching device is connected to a gate control drive terminal. The end of the second switching device that is not connected to the first switching device is grounded; the reference layer is connected at the connection between the first switching device and the second switching device.

5. The self-generating self-receiving coil of claim 4, wherein, A capacitor is also connected in parallel across the two ends of the first and second switching devices.

6. The self-generating self-receiving coil of claim 4, wherein, The first switching device and the second switching device are field-effect transistors, transistors, diodes or PIN diodes.

7. The self-generating self-receiving coil of claim 4, wherein, A current-limiting resistor is also provided between the end of the first switching device that is not connected to the second switching device and the gate control drive end.

8. The self-generating self-receiving coil of claim 1, wherein, The matching resistor can be a through-hole resistor, a surface mount resistor, a wire-wound resistor, or a PCB trace resistor.

9. A method of operating a self-generating self-receiving coil as claimed in any one of claims 1-8, characterized in that, When the self-transmitting and self-receiving coil is in the transmitting state, the first T / R switch and the second T / R switch are in the conducting state; the third T / R switch and the fourth T / R switch are in the cut-off state, and the reference layer switching circuit makes the reference layer and ground present a low-resistance state; when the self-transmitting and self-receiving coil is in the receiving state, the first T / R switch and the second T / R switch are in the cut-off state. When the third and fourth T / R switches are in the ON state, the reference layer switching circuit makes the reference layer and ground present a high-resistance state.

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