WO2022133823A1 - 天线电路、通信芯片、终端设备及反馈调谐方法 - Google Patents

天线电路、通信芯片、终端设备及反馈调谐方法 Download PDF

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Publication number
WO2022133823A1
WO2022133823A1 PCT/CN2020/138690 CN2020138690W WO2022133823A1 WO 2022133823 A1 WO2022133823 A1 WO 2022133823A1 CN 2020138690 W CN2020138690 W CN 2020138690W WO 2022133823 A1 WO2022133823 A1 WO 2022133823A1
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Prior art keywords
circuit
node
antenna
feedback
capacitor
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PCT/CN2020/138690
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English (en)
French (fr)
Inventor
袁广凯
郭子成
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深圳市汇顶科技股份有限公司
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Priority to PCT/CN2020/138690 priority Critical patent/WO2022133823A1/zh
Publication of WO2022133823A1 publication Critical patent/WO2022133823A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits

Definitions

  • the present application relates to the field of communication technologies, and in particular, to an antenna circuit, a communication chip, a terminal device and a feedback tuning method.
  • NFC Near Field Communication
  • 13.56MHz the carrier frequency to transmit modulated signals.
  • the strength of the 13.56MHz signal directly affects the size of the communication signal.
  • the NFC antenna circuit reaches a resonance state at 13.56MHz. At this time, the antenna can obtain the maximum operating voltage, the magnetic field is the largest, and the maximum communication signal volume can be obtained, that is, the communication quality is the best.
  • the resonant frequency of the NFC antenna circuit may deviate from 13.56MHz, resulting in a decrease in the transmit voltage at the antenna end, a decrease in the magnetic field, and a weakened communication signal, which reduces the communication quality.
  • the present application provides an antenna circuit, a communication chip, a terminal device and a feedback tuning method to ensure the communication quality of the antenna circuit.
  • an embodiment of the present application provides an antenna circuit, including: a filter circuit, a matching circuit, an antenna network circuit, and a feedback circuit;
  • the input end of the filter circuit is used for receiving the input voltage
  • the output end of the filter circuit is connected with the input end of the matching circuit
  • the output end of the matching circuit is connected with the input end of the antenna network circuit
  • the filter circuit is used for filtering the input voltage
  • the matching circuit is configured to match the output of the filter circuit with the input of the antenna network circuit
  • the feedback circuit is connected to the matching circuit through a connection node in the matching circuit, and the feedback circuit is configured to adjust the amplification factor of the feedback circuit according to the voltage of the connection node, so that the voltage of the connection node is is the maximum value.
  • This embodiment provides an antenna circuit.
  • the antenna circuit is provided with a feedback circuit that can adjust the magnification.
  • the feedback circuits of different magnifications can be equivalent to inserting capacitance values of different sizes into the antenna circuit. Therefore, by amplifying The adjustment of the multiple can equivalently adjust the overall equivalent capacitance value in the circuit, thereby changing the resonant frequency of the antenna circuit.
  • the voltage of the connecting node is the maximum value, it can be considered that the antenna circuit works at the predetermined resonant frequency, so that the antenna circuit is in the maximum value. Resonance state, so as to ensure the quality of communication and improve the stability and reliability of communication.
  • the purpose of reducing the cost of the antenna circuit can be achieved.
  • the feedback circuit includes an amplifier circuit and a first capacitor, and the first capacitor is a non-variable capacitor;
  • the input end of the amplifying circuit is connected to the connection node, the output end of the amplifying circuit is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the connection node.
  • the amplification factor A of the amplification circuit is adjustable, and the connection between the amplification circuit and the first capacitor can form a feedback closed loop. to adjust the resonant frequency of the antenna circuit.
  • the amplifying circuit is used to realize in-phase amplification or inverting amplification, so as to adjust the amplification factor of the amplifying circuit, so as to adjust the size of the capacitance value of the feedback circuit connected to the antenna circuit.
  • the overall equivalent capacitance value in the antenna circuit can be adjusted equivalently, thereby playing the role of adjusting the resonant frequency of the antenna circuit.
  • the amplifying circuit includes: a first switch, a second switch, a third switch, a fourth switch, a first adjustable resistor, a second adjustable resistor, a third adjustable resistor, and an operational amplifier;
  • One end of the first switch is grounded, and the other end of the first switch is connected to one end of the first adjustable resistor; one end of the second switch is connected to the connection node, and the other end of the second switch is connected to the connection node.
  • One end is connected to the one end of the first adjustable resistor; the other end of the first adjustable resistor is connected to the inverting input end of the operational amplifier;
  • One end of the third switch is grounded, and the other end of the third switch is connected to one end of the second adjustable resistor; one end of the fourth switch is connected to the connection node, and the other end of the fourth switch is connected to the connection node.
  • One end is connected to the one end of the second adjustable resistor; the other end of the second adjustable resistor is connected to the non-inverting input end of the operational amplifier;
  • One end of the third adjustable resistor is connected to the inverting input end of the operational amplifier, and the other end of the third adjustable resistor is connected to the output end of the operational amplifier;
  • the output end of the operational amplifier is connected to the one end of the first capacitor as the output end of the amplifying circuit
  • the amplifying circuit is configured to realize in-phase amplification when the first switch and the fourth switch are in a closed state and the second switch and the third switch are in an open state;
  • the amplifying circuit is further configured to implement inverting amplification when the first switch and the fourth switch are in an open state and the second switch and the third switch are in a closed state.
  • the amplification factor A of the amplifying circuit can be changed within the range of A ⁇ 0 and A>1, so as to adjust the amplification factor of the amplifying circuit.
  • the amplifying circuit further includes: a fourth adjustable resistor
  • One end of the fourth adjustable resistor is connected to the non-inverting input end of the operational amplifier, and the other end of the fourth adjustable resistor is grounded.
  • the control circuit can control the amplification factor A of the amplifier circuit to change within the range of 0 ⁇ A ⁇ 1, so as to achieve the effect of traversing all the amplification factors of the amplifier circuit, In order to more accurately determine the amplification factor of the amplifying circuit when the connection node voltage is the maximum value.
  • the feedback circuit further comprises: a control circuit
  • the control circuit is connected to the amplifying circuit, and the control circuit is used to control the working state of each switch in the amplifying circuit and the resistance value of each adjustable resistor, so as to adjust the magnification of the amplifying circuit.
  • control circuit is used to realize the function of adjusting the amplification factor of the amplifying circuit, so as to facilitate the determination of the amplification factor of the amplifying circuit when the connection node voltage is the maximum value.
  • the feedback circuit includes a current source.
  • the phase and magnification of the current source IS it can be equivalent to inserting a positive capacitor or a negative capacitor into the antenna circuit, which is equivalent to adjusting the overall equivalent capacitance value in the antenna circuit, thereby changing the antenna
  • the resonant frequency of the circuit makes the antenna circuit work at a predetermined resonant frequency.
  • a connection node between the feedback circuit and the matching circuit is a first node, and the first node is a node between the matching circuit and the filter circuit;
  • the filter circuit includes a first inductor
  • One end of the first inductor is connected to the input voltage, and the other end of the first inductor is connected to the matching circuit to form the first node.
  • the inductor has the characteristics of "passing DC and blocking AC".
  • the feedback circuit includes a first capacitor, and the capacitor has the characteristics of "passing AC and blocking DC”. Therefore, when the feedback circuit is connected to the first node M, the first capacitor The input voltage can be filtered in cooperation with the first inductor.
  • the overall equivalent capacitance value in the antenna circuit can be adjusted equivalently, so as to ensure that the antenna circuit operates at a predetermined resonant frequency to avoid detuning.
  • a connection node between the feedback circuit and the matching circuit is a first node or a second node, the first node is a node between the matching circuit and the filter circuit, and the second node A node is a node where the matching circuit is connected to the antenna network circuit;
  • the filter circuit includes: a first inductor and a second capacitor, and the second capacitor is a non-variable capacitor;
  • One end of the first inductor is connected to the input voltage, the other end of the first inductor is connected to the matching circuit to form the first node, and one end of the second capacitor is connected to the first node , and the other end of the second capacitor is grounded.
  • the inductor has the characteristics of "passing DC and blocking AC", while the capacitor has the characteristics of "passing AC and blocking DC”. Therefore, by setting the first inductor and the second capacitor, the filter circuit can filter the input voltage.
  • the capacitance value connected to the feedback circuit can be equivalently adjusted, that is, the overall equivalent capacitance value of the antenna circuit can be adjusted to ensure that the antenna circuit operates at a predetermined resonant frequency to avoid detuning.
  • a connection node between the feedback circuit and the matching circuit is a second node, and the second node is a node between the matching circuit and the antenna network circuit;
  • the matching circuit includes a third capacitor, and the third capacitor is a non-variable capacitor
  • One end of the third capacitor is connected to the filter circuit to form a first node, and the other end of the third capacitor is connected to the antenna network circuit to form the second node.
  • the capacitance value connected to the feedback circuit can be adjusted equivalently, that is, the overall equivalent capacitance value of the antenna circuit can be adjusted to ensure that the antenna circuit operates at the predetermined resonant frequency. to avoid detuning.
  • a connection node between the feedback circuit and the matching circuit is a first node or a second node, the first node is a node between the matching circuit and the filter circuit, and the second node A node is a node where the matching circuit is connected to the antenna network circuit;
  • the matching circuit includes a third capacitor and a fourth capacitor, and the third capacitor and the fourth capacitor are non-variable capacitors;
  • One end of the third capacitor is connected to the filter circuit to form the first node, and the other end of the third capacitor is connected to the antenna network circuit to form the second node; One end is connected to the second node, and the other end of the fourth capacitor is grounded.
  • the capacitance value connected to the feedback circuit can be adjusted equivalently, that is, the overall equivalent capacitance value of the antenna circuit can be adjusted to ensure that the antenna circuit operates at the predetermined resonant frequency. to avoid detuning.
  • the antenna network circuit includes a fourth resistor, a fifth capacitor, and a second inductor, and the fifth capacitor is a non-variable capacitor;
  • One end of the fourth resistor is connected to the matching circuit to form a second node, one end of the fourth resistor is also connected to one end of the fifth capacitor, and the other end of the fourth resistor is connected to the second node.
  • One end of the inductor is connected, and the other end of the fifth capacitor and the other end of the second inductor are grounded.
  • the antenna network circuit is connected with the matching circuit, and based on the energy provided by the matching circuit, the second inductor in the antenna network circuit can transmit a magnetic field, so that communication can be performed through the magnetic field.
  • an embodiment of the present application provides a feedback tuning method, which is applied to the above-mentioned antenna circuit, and the method includes:
  • the amplification factor of the feedback circuit is adjusted according to the voltage of the connection node between the feedback circuit and the matching circuit in the antenna circuit, so that the voltage of the connection node is the maximum value.
  • feedback circuits with different magnifications can be equivalent to inserting capacitance values of different sizes into the antenna circuit. Therefore, by adjusting the magnification, the overall equivalent capacitance in the circuit can be adjusted equivalently, thereby changing the The resonant frequency of the antenna circuit, when the voltage of the connecting node is the maximum value, it can be considered that the antenna circuit works at the predetermined resonant frequency, so that the antenna circuit is in a resonant state, thereby ensuring the quality of communication and improving the stability and reliability of communication.
  • the purpose of reducing the cost of the antenna circuit can be achieved.
  • adjusting the amplification factor of the feedback circuit according to the voltage of the connection node between the feedback circuit and the matching circuit in the antenna circuit includes:
  • the magnification of the feedback circuit when adjusting the magnification of the feedback circuit according to the voltage of the connection node, it can be realized by traversing and adjusting the magnification of the feedback circuit, that is, by taking different magnifications of the feedback circuit, and obtaining the connection node at different magnifications.
  • the target amplification factor corresponding to the maximum voltage can be determined as the amplification factor of the feedback circuit, that is, the amplification factor of the feedback circuit can be adjusted to the target amplification factor, thereby making the antenna circuit work at the predetermined resonant frequency to avoid detuning .
  • the separately acquiring the voltages of the connection nodes when the feedback circuits are at different magnifications includes:
  • Adjust the magnification of the feedback circuit to another magnification, and the other magnification is a value that is different from the initial magnification in the magnification adjustment range, and obtain that the connection node is the same as the feedback circuit. voltages at the other magnifications, until all values in the magnification adjustment range have corresponding voltages.
  • the feedback circuit when the amplification factor of the feedback circuit is adjusted according to the voltage of the connection node, the feedback circuit can be set to different amplification factors, and the voltage of the connection node at different amplification factors can be obtained, which can help to accurately determine the maximum voltage, and further can Accurately determine the target magnification corresponding to the maximum voltage.
  • adjusting the amplification factor of the feedback circuit includes:
  • the feedback circuit includes an amplifying circuit, adjusting the switching state of each switch in the amplifying circuit and the resistance value of the adjustable resistor;
  • the feedback circuit includes a current source
  • the phase and the amplification factor of the current source are adjusted.
  • the feedback circuit is voltage feedback tuning or current feedback tuning
  • the amplification factor is adjusted according to the specific structure of the feedback circuit
  • the capacitance value in the circuit can be adjusted equivalently
  • the resonant frequency of the antenna circuit can be changed to meet the predetermined
  • the frequency requirement is to meet the predetermined resonant frequency to avoid detuning, so as to ensure the communication quality and improve the stability and reliability of the communication.
  • an embodiment of the present application provides an NFC control chip for near field communication, including: the aforementioned filter circuit, a matching circuit, and a feedback circuit.
  • an embodiment of the present application provides a terminal device, where the device includes the above-mentioned near field communication NFC control chip.
  • the present application provides an antenna circuit, a communication chip, a terminal device and a feedback tuning method, wherein the antenna circuit includes: a filter circuit, a matching circuit, an antenna network circuit and a feedback circuit; an input end of the filter circuit is used for receiving an input voltage, The output end of the filter circuit is connected to the input end of the matching circuit, and the output end of the matching circuit is connected to the input end of the antenna network circuit; the filter circuit is used for filtering the input voltage; The matching circuit is used to match the output of the filter circuit with the input of the antenna network circuit; the feedback circuit is connected to the matching circuit through a connection node in the matching circuit, and the feedback circuit is used to The voltage of the connection node adjusts the amplification factor of the feedback circuit so that the voltage of the connection node has a maximum value.
  • the antenna circuit is provided with a feedback circuit that can adjust the magnification.
  • the feedback circuits of different magnifications can be equivalent to inserting capacitance values of different sizes into the antenna circuit. Therefore, by adjusting the magnification, it is possible to wait for It can effectively adjust the overall equivalent capacitance value in the circuit, thereby changing the resonant frequency of the antenna circuit.
  • the voltage of the connecting node is the maximum value, it can be considered that the antenna circuit works at the predetermined resonant frequency, so that the antenna circuit is in a resonant state, thereby ensuring communication. quality, improve the stability and reliability of communication.
  • the purpose of reducing the cost of the antenna circuit can be achieved.
  • FIG. 1 is a schematic diagram of an antenna circuit provided by an embodiment of the present application.
  • 2a is a schematic diagram of a feedback circuit provided by an embodiment of the present application.
  • FIG. 2b is another schematic diagram of a feedback circuit provided by an embodiment of the present application.
  • 3a is another schematic diagram of a feedback circuit provided by an embodiment of the present application.
  • 3b is another schematic diagram of a feedback circuit provided by an embodiment of the application.
  • FIG. 4 is another schematic diagram of a feedback circuit provided by an embodiment of the present application.
  • FIG. 5 is another schematic diagram of an antenna circuit provided by an embodiment of the present application.
  • FIG. 6 is another schematic diagram of an antenna circuit provided by an embodiment of the present application.
  • FIG. 7 is a schematic diagram of a voltage feedback tuning principle in an embodiment of the present application.
  • Fig. 8 is the waveform schematic diagram of current and voltage
  • FIG. 9 is another schematic diagram of an antenna circuit provided by an embodiment of the present application.
  • FIG. 10 is a schematic diagram of a current feedback tuning principle in an embodiment of the application.
  • FIG. 11 is a schematic diagram of a voltage feedback type automatic tuning circuit provided by an embodiment of the application.
  • FIG. 12 is a schematic diagram of a feedback tuning method provided by an embodiment of the present application.
  • FIG. 13 is a schematic diagram of adjusting the magnification of the feedback circuit in the embodiment of the application.
  • FIG. 14 is a schematic diagram of respectively acquiring the voltages of the connection nodes when the feedback circuits have different magnifications according to an embodiment of the present application.
  • Resonance is also called “resonance”. Under the action of periodic external force, when the frequency of the external force is the same as or very close to the natural oscillation frequency of the system, the amplitude of the oscillation system increases sharply. The frequency at which resonance occurs is called the "resonant frequency”.
  • the following situations may occur: (1) During a certain period of time, the voltage of the capacitor gradually increases, while the current gradually decreases; the current of the inductor gradually increases, but the voltage of the inductor gradually increases. (2) In another time period, the voltage of the capacitor gradually decreases, while the current gradually increases; the current of the inductor gradually decreases, but the voltage of the inductor gradually increases.
  • the increase of the voltage can reach a positive maximum value, and the decrease of the voltage can also reach a negative maximum value.
  • the direction of the current will also change in the positive and negative directions during this process, which is called the electrical oscillation of the circuit.
  • the sinusoidal frequency of the external input voltage of the resonant circuit reaches a certain frequency (that is, the resonant frequency of the resonant circuit)
  • the resonant circuit is purely resistive to the outside, that is, resonance .
  • the resonant circuit amplifies the input by a factor of Q, where Q is the quality factor.
  • the quality factor Q is 28, then for a resonant circuit with an inductor L and a capacitor C in parallel, the current is increased by a factor of 28. For a resonant circuit with inductor L and capacitor C in series, the voltage is increased by a factor of 28.
  • Resonant circuit composed of inductor L and capacitor C, circuit impedance Among them, R is the resistance, ⁇ L is the inductive reactance of the inductor, is the capacitive reactance of the capacitor.
  • Detuning means that the resonant frequency of the antenna circuit deviates from the predetermined resonant frequency (13.56MHz).
  • the transmission voltage at the antenna end will decrease, resulting in a decrease in the magnetic field emitted by the coil and weakening the communication signal. This in turn degrades the communication quality.
  • the NFC communication chip is provided with a matching circuit, and the antenna coil is connected to the NFC communication chip through the matching circuit.
  • the antenna coil is used to transmit a magnetic field.
  • the antenna coil can be equivalent to an inductance.
  • the device deviation is the precision deviation of the component itself. In the antenna circuit, it is mainly the precision deviation of the inductance L and the capacitance C. According to the formula When there is an accuracy deviation between L and C, it will also cause the resonant frequency to deviate, resulting in detuning.
  • an improved method adopted in the prior art is to achieve the purpose of automatic tuning by adding variable capacitors in the antenna circuit, specifically: setting the capacitors in the antenna circuit as adjustable capacitors, such as voltage-controlled capacitors or Program-controlled capacitors, etc., when the circuit is detuned, directly adjust the capacitance value of the adjustable capacitor to make the antenna circuit work at the preset resonant frequency, so that the antenna circuit is maintained in a resonant state.
  • the prior art method requires adding an adjustable capacitance in the antenna circuit, which may result in an increase in the cost of the antenna circuit.
  • the antenna circuit, communication chip, terminal device and tuning method provided by the present application aim to solve the above technical problems in the prior art, so as to achieve the purpose of preventing detuning and reducing cost.
  • the resonance frequency is only determined by the inherent inductance value L and capacitance value C of the antenna circuit itself. If the resonance frequency deviates, whether it is due to external factors or the antenna circuit itself, the resonance can be adjusted by adjusting the capacitance value in the antenna circuit. frequency, so that the adjusted resonant frequency meets the predetermined frequency requirement, so that the antenna circuit is in a resonant state.
  • the emission voltage of the antenna network circuit in the antenna circuit is the maximum value, so as to achieve the best power transmission. Therefore, when the antenna circuit is feedback tuned, the voltage in the antenna circuit can be used as A reference standard that assists in the feedback tuning process by measuring the voltage in the antenna circuit.
  • the present application provides an antenna circuit
  • the antenna circuit is provided with a feedback circuit that can adjust the amplification factor according to the voltage of the connection node, and the feedback circuits with different amplification factors can be equivalent to the feedback circuit inserting different sizes into the antenna circuit. Therefore, by adjusting the magnification, it can be equivalent to adjusting the overall equivalent capacitance value in the antenna circuit, thereby changing the resonant frequency of the antenna circuit, and when the voltage of the connecting node is the maximum value, it can be considered that the antenna circuit Work at a predetermined resonant frequency, so that the antenna circuit is in a resonant state to avoid detuning. Since there is no need to set a high-cost adjustable capacitor in the antenna circuit, the purpose of reducing the cost of the antenna circuit can be achieved.
  • the antenna circuit in the present application can be, in particular, an NFC antenna circuit
  • the communication chip in the present application can be, in particular, an NFC communication chip
  • the terminal device in the present application Specifically, it may be a device supporting the NFC function
  • the tuning method in this application may be specifically applied to the NFC communication technology.
  • FIG. 1 is a schematic diagram of an antenna circuit provided by an embodiment of the present application. As shown in FIG. 1 , the antenna circuit includes: a filter circuit 10 , a matching circuit 20 , an antenna network circuit 30 and a feedback circuit 40 .
  • the input end of the filter circuit 10 is used for receiving the input voltage
  • the output end of the filter circuit 10 is connected to the input end of the matching circuit 20
  • the output end of the matching circuit 20 is connected to the input end of the antenna network circuit 30 .
  • the filter circuit 10 is used to filter the input voltage.
  • the filter circuit 10 can filter harmonics, so that the input voltage can be processed by the filter circuit 10 to remove or at least remove part of the harmonic signal to improve signal quality.
  • the antenna network circuit 30 is used to transmit the magnetic field, and the matching circuit 20 is used to match the output of the filter circuit 10 with the input of the antenna network circuit 30 to obtain better power transmission and ensure the transmission energy of the antenna network circuit 30 .
  • the feedback circuit 40 is connected to the matching circuit 20 through a connection node in the matching circuit 20 .
  • both the input terminal and the output terminal of the feedback circuit 40 are connected to the node M or the node N in FIG. 1 .
  • the feedback circuit 40 is used to adjust the amplification factor of the feedback circuit 40 according to the voltage of the connection node, so that the voltage of the connection node is the maximum value.
  • whether the voltage of the connection node is the maximum value can indirectly reflect whether the antenna circuit operates at a predetermined resonant frequency, that is, the voltage of the connection node can reflect the current resonant frequency of the antenna circuit.
  • the current resonance frequency of the antenna circuit is determined by the capacitance value and inductance value of the antenna circuit, etc. Therefore, the voltage of the connection node can be considered to be determined by the overall structure of the antenna circuit. Since the filter circuit 10, the matching circuit 20 and the antenna network circuit 30 are all fixed circuit structures, when other factors remain unchanged (such as the electrical components included in each circuit and the connection relationship, etc.), the feedback circuit can be adjusted by adjusting the feedback circuit.
  • the magnification of 40 can be equivalent to adjusting the current resonant frequency of the antenna circuit.
  • the voltage of the connection node is the maximum value by adjusting the magnification of the feedback circuit 40. , it can be considered that the antenna circuit works at a predetermined resonant frequency through adjustment.
  • the amplification factor of the feedback circuit 40 can be adjusted according to the voltage of the node M; when the feedback circuit 40 is connected to the matching circuit 20 at the node N, it can be adjusted according to the voltage of the node N. Adjust the magnification of the feedback circuit 40 .
  • the magnification of the feedback circuit 40 when adjusting the magnification of the feedback circuit 40 according to the voltage of the connection node, it can be realized by traversing and adjusting the magnification of the feedback circuit 40, that is, by taking different magnifications of the feedback circuit 40, and obtaining the different magnifications of the connection node.
  • the voltage at the time of magnification according to the characteristics of the maximum voltage value of the antenna circuit in the resonance state, it can be determined that in the process of traversal adjustment, when the voltage of the connection node is at the maximum value, the antenna circuit is in the resonance state, therefore, the maximum voltage can be determined.
  • the corresponding target amplification factor is determined as the amplification factor of the feedback circuit 40, and the amplification factor of the feedback circuit 40 is adjusted to the target amplification factor, so that the antenna circuit operates at the predetermined resonance frequency.
  • the feedback circuit 40 can also be adjusted according to the current of the connection node. gain.
  • the principle of adjusting the amplification factor of the feedback circuit 40 according to the current is similar to the above-mentioned principle of adjusting the amplification factor of the feedback circuit 40 according to the voltage, and will not be repeated here.
  • the predetermined resonance frequency when applied to the field of NFC communication, may be a carrier frequency used for transmitting modulated signals in the NFC communication technology, that is, 13.56 MHz.
  • This embodiment provides an antenna circuit.
  • the antenna circuit is provided with a feedback circuit that can adjust the magnification.
  • the feedback circuits of different magnifications can be equivalent to inserting capacitance values of different sizes into the antenna circuit. Therefore, by amplifying The adjustment of the multiple can equivalently adjust the overall equivalent capacitance value in the circuit, thereby changing the resonant frequency of the antenna circuit.
  • the voltage of the connecting node is the maximum value, it can be considered that the antenna circuit works at the predetermined resonant frequency, so that the antenna circuit is in the maximum value. Resonance state, so as to ensure the quality of communication and improve the stability and reliability of communication.
  • the purpose of reducing the cost of the antenna circuit can be achieved.
  • the feedback circuit 40 may perform feedback tuning by means of voltage feedback.
  • FIG. 2a is a schematic diagram of a feedback circuit 40 provided by an embodiment of the present application.
  • the feedback circuit 40 when tuning is performed in a voltage feedback manner, the feedback circuit 40 includes an amplifier circuit 41 and a first capacitor C1, and the first capacitor C1 is a non- Variable capacitor; the input end of the amplifier circuit 41 is connected to the connection node (M or N), the output end of the amplifier circuit 41 is connected to one end of the first capacitor C1, and the other end of the first capacitor C1 is connected to the connection node of the amplifier circuit 41 Node connection.
  • the other end of the first capacitor C1 is also connected to the node M; when the input end of the amplifying circuit 41 is connected to the node N, the other end of the first capacitor C1 is also connected to the node M. Node N is connected.
  • the amplification factor A of the amplification circuit 41 is adjustable, and the connection between the amplification circuit 41 and the first capacitor C1 can form a feedback closed loop.
  • the overall equivalent capacitance in the antenna circuit can be adjusted equivalently value to adjust the resonant frequency of the antenna circuit.
  • a control circuit for adjusting the amplification factor of the amplification circuit 41 may be provided in the feedback circuit 40 .
  • FIG. 2b is another schematic diagram of the feedback circuit 40 provided by the embodiment of the application.
  • the feedback circuit 40 further includes a control circuit 42, the control circuit 42 is connected to the amplifying circuit 41, and the control circuit 42 is used to realize the adjustment of the amplifying circuit 41, so that it is convenient to determine the magnification of the amplifying circuit 41 when the connection node voltage is the maximum value.
  • control circuit 42 is not limited in this application, and the control circuit 42 can adopt the existing circuit structure, as long as the control circuit 42 can adjust the amplification of the amplifying circuit 41 in combination with the specific structure of the amplifying circuit 41 The effect of multiples is sufficient.
  • the amplifying circuit 41 is used to realize in-phase amplification or inverting amplification, so as to adjust the amplification factor of the amplifying circuit 41 to adjust the capacitance value of the feedback circuit 40 connected to the antenna circuit.
  • the feedback circuit 40 when the amplification factor A>1, the feedback circuit 40 is equivalent to an inductance (negative capacitance), and by adding an inductance to the antenna circuit, the overall equivalent capacitance value in the antenna circuit can be reduced equivalently; when the amplification factor A When ⁇ 1, the feedback circuit 40 is equivalent to a capacitor, and by adding a capacitor to the antenna circuit, the overall equivalent capacitance value in the antenna circuit can be equivalently increased.
  • the size of the capacitance value of the feedback circuit 40 connected to the antenna circuit can be adjusted, that is, the overall equivalent capacitance value in the antenna circuit can be adjusted equivalently, thereby changing the The effect of the resonant frequency of the antenna circuit.
  • the specific structure of the feedback circuit 40 is explained.
  • FIG. 3a is a schematic diagram of a feedback circuit 40 provided by an embodiment of the present application.
  • an amplifying circuit 41 is connected to a control circuit 42, and the amplifying circuit 41 includes: a first switch K1, a second switch K2, a third switch K3, The fourth switch K4, the first adjustable resistor R1, the second adjustable resistor R2, the third adjustable resistor R3 and the operational amplifier OP.
  • one end of the first switch K1 is grounded, the other end of the first switch K1 is connected to one end of the first adjustable resistor R1; one end of the second switch K2 is connected to the connection node, and the other end of the second switch K2 is connected to the first One end of an adjustable resistor R1 is connected; the other end of the first adjustable resistor R1 is connected to the inverting input end of the operational amplifier OP;
  • One end of the third switch K3 is grounded, and the other end of the third switch K3 is connected to one end of the second adjustable resistor R2; one end of the fourth switch K4 is connected to the connection node, and the other end of the fourth switch K4 is connected to the second adjustable resistor One end of R2 is connected; the other end of the second adjustable resistor R2 is connected to the non-inverting input end of the operational amplifier OP;
  • One end of the third adjustable resistor R3 is connected to the inverting input end of the operational amplifier OP, and the other end of the third adjustable resistor R3 is connected to the output end of the operational amplifier OP;
  • the output end of the operational amplifier OP is connected to one end of the first capacitor C1 as the output end of the amplifier circuit 41, and the other end of the first capacitor C1 is connected to the connection node connected to the amplifier circuit 41;
  • the amplifier circuit 41 is used for the first switch K1 When the fourth switch K4 and the fourth switch K4 are in the closed state, and the second switch K2 and the third switch K3 are in the open state, in-phase amplification is realized;
  • the amplifier circuit 41 is also used for the first switch K1 and the fourth switch K4 are in the open state, And when the second switch K2 and the third switch K3 are in a closed state, inversion amplification is realized.
  • control circuit 42 is used to control the working state of each switch in the amplifying circuit 41 and the resistance value of each adjustable resistor to adjust the magnification of the amplifying circuit 41.
  • the specific process of adjusting the magnification by the control circuit is explained below:
  • the control circuit 42 controls the second switch K2 and the third switch K3 to close, controls the first switch K1 and the fourth switch K4 to open, and controls the first adjustable resistor R1 is the minimum value, and the third adjustable resistor R3 is the maximum value.
  • the amplification factor of the amplifying circuit 41 is That is, the magnification is the maximum negative magnification at this time;
  • the range of magnification can be preset, for example, set the magnification to -Amax (-Amax represents the maximum magnification of the target whose magnification is negative, and the maximum magnification of the target may be smaller than the actual maximum magnification), and then, according to -Amax Adjust the specific resistance value of R3. That is, the resistance value of R3 may not need to be adjusted to the actual maximum resistance value of R3.
  • control circuit 42 controls the third adjustable resistance R3 to gradually decrease to the minimum value, during this change process, the amplification factor A is still a negative value, but the absolute value of the amplification factor A gradually decreases;
  • the control circuit 42 controls the second switch K2 and the third switch K3 to turn off, and controls the first switch K1 and the fourth switch K4 to turn on.
  • the resistance R3 is the minimum value, and the amplification factor of the amplifying circuit 41 is That is, the magnification is the maximum positive magnification at this time, and the magnification A>1;
  • the control circuit 42 controls the third adjustable resistor R3 to gradually increase to the maximum value.
  • the amplification factor A is still a value greater than 1, and the amplification factor A gradually increases.
  • the range of magnification can be preset, for example, set the magnification to Amax (Amax represents the maximum magnification of the target with a positive magnification, and the maximum magnification of the target may be smaller than the actual maximum magnification), and then adjust the R3 according to Amax. specific resistance value. That is to say, the resistance value of R3 may not need to be adjusted to the actual maximum resistance value of R3.
  • control circuit 42 can realize that the amplification factor of the amplifying circuit 41 can be changed within the range of A ⁇ 0 and A>1, so as to adjust the amplification factor of the amplifying circuit 41 .
  • a fourth adjustable resistor can be set in the amplifying circuit 41, so that the control circuit 42 can control the magnification of the amplifying circuit 41 to change within the range of 0 ⁇ A ⁇ 1, thereby realizing the traversal of the amplifying circuit 41. All the magnifications are used to more accurately determine the magnification of the amplifying circuit 41 when the connection node voltage is at the maximum value.
  • FIG. 3b is another schematic diagram of the feedback circuit 40 provided by the embodiment of the present application.
  • the amplifying circuit further includes: a fourth adjustable resistor R4; The non-inverting input terminal is connected, and the other terminal of the fourth adjustable resistor R4 is grounded.
  • the control circuit 42 can adjust the voltage division ratio of the second adjustable resistor R2 and the fourth adjustable resistor R4 by controlling the resistance values of the second adjustable resistor R2 and the fourth adjustable resistor R4, thereby controlling the amplifier circuit.
  • the control circuit 42 can realize the in-phase amplification or inverting amplification of the amplifier circuit by adjusting the on/off state of each switch and adjusting the resistance value of each adjustable resistor.
  • the magnification of the amplifying circuit is adjusted, so that the equivalent feedback circuit 40 can access the capacitance value of the antenna circuit, that is, the overall equivalent capacitance value in the antenna circuit can be adjusted, thereby changing the resonant frequency of the antenna circuit.
  • the feedback circuit 40 may perform feedback tuning by means of current feedback.
  • FIG. 4 is a schematic diagram of a feedback circuit 40 provided by an embodiment of the present application.
  • the feedback circuit 40 when tuning is performed in a current feedback manner, the feedback circuit 40 includes a current source IS.
  • the current source may be a program-controlled current source.
  • the phase and magnification of the current source IS can be adjusted.
  • the current source can be equivalent to a capacitor or an inductor (negative capacitor).
  • the current source is equivalent to a capacitor, it is equivalent to adding to the antenna circuit. Adding a capacitor increases the capacitance value of the antenna circuit; when the current source is equivalent to an inductance, it is equivalent to adding a negative capacitor to the antenna circuit, thereby reducing the capacitance value of the antenna circuit.
  • the magnification of the current source the value of the added capacitance or inductance can be adjusted, that is, the specific value of the increased or decreased capacitance value can be adjusted.
  • the feedback circuit 40 may further include a control circuit (not shown in the figure) for adjusting the phase and the amplification factor of the current source IS.
  • the phase and magnification of the current source IS it can be equivalent to inserting a positive capacitor or a negative capacitor into the antenna circuit, which is equivalent to adjusting the overall equivalent capacitance value in the antenna circuit, thereby changing the antenna
  • the resonant frequency of the circuit makes the antenna circuit work at a predetermined resonant frequency.
  • the specific structure of the antenna circuit is explained by taking the feedback circuit 40 including the amplifier circuit 41 and the first capacitor C1 as an example.
  • FIG. 5 is a schematic diagram of an antenna circuit provided by an embodiment of the present application.
  • the connection node between the feedback circuit 40 and the matching circuit 20 is the first node, and the first node is the node M where the matching circuit 20 and the filter circuit 10 are connected .
  • the filter circuit 10 includes a first inductor L1 and a second capacitor C2, and the second capacitor C2 is a non-variable capacitor; one end of the first inductor L1 is connected to the input voltage, and the other end of the first inductor L1 is connected to the matching circuit 20 to form the first inductor.
  • One node, one end of the second capacitor C2 is connected to the first node, and the other end of the second capacitor C2 is grounded.
  • the inductor has the characteristics of "passing DC and blocking AC", while the capacitor has the characteristics of "passing AC and blocking DC”. Therefore, by setting the first inductor L1 and the second capacitor C2, the filter circuit 10 can filter the input voltage. .
  • the amplifying circuit 41 When the first capacitor C1 in the feedback circuit 40 is connected to the node M, by controlling the amplifying circuit 41 to realize in-phase amplification or inverting amplification and adjusting the magnification of the amplifying circuit, it can be equivalent to adjusting the amplifying circuit 41 to connect to the antenna circuit.
  • the size of the capacitance value of the positive capacitance or the negative capacitance is adjusted, which is equivalent to adjusting the overall equivalent capacitance value in the antenna circuit.
  • the filter circuit 10 includes the first inductor L1; the first inductor L1 One end of the first inductor L1 is connected to the input voltage Ui, and the other end of the first inductor L1 is connected to the matching circuit 20 to form the first node M.
  • the inductor has the characteristics of "passing DC and blocking AC”.
  • the first capacitor C1 in the feedback circuit 40 is also connected to the node M, and the capacitor has the characteristics of "passing AC and blocking DC”. Therefore, when the feedback circuit 40 is connected to At the first node M, the first capacitor C1 can cooperate with the first inductor L1 to filter the input voltage Ui.
  • the matching circuit 20 includes a third capacitor C3 and a fourth capacitor C4, and the third capacitor C3 and the fourth capacitor C4 are non-variable capacitors; one end of the third capacitor C3 is connected to the filter circuit 10 to form At the first node, the other end of the third capacitor C3 is connected to the antenna network circuit 30 to form a second node; one end of the fourth capacitor C4 is connected to the second node, and the other end of the fourth capacitor C4 is grounded.
  • the antenna network circuit 30 includes a fourth resistor R4, a fifth capacitor C5 and a second inductor L2, and the fifth capacitor C5 is a non-variable capacitor; one end of the fourth resistor R4 is connected to the matching circuit 20 to A second node is formed, one end of the fourth resistor R4 is also connected to one end of the fifth capacitor C5, the other end of the fourth resistor R4 is connected to one end of the second inductor L2, the other end of the fifth capacitor C5 and the second inductor L2 The other end is grounded.
  • the antenna network circuit 30 is connected with the matching circuit 20, and based on the energy provided by the matching circuit 20, the second inductor L2 in the antenna network circuit 30 can transmit a magnetic field, so that communication can be performed through the magnetic field.
  • FIG. 6 is another schematic diagram of an antenna circuit provided by an embodiment of the present application. As shown in FIG. 6 , the connection node between the feedback circuit 40 and the matching circuit 20 is the second node, and the second node is the connection between the matching circuit 20 and the antenna network circuit 30 the node N.
  • the feedback circuit 40 when the feedback circuit 40 is connected to the second node, by controlling the amplifier circuit 41 to realize in-phase amplification or in-phase amplification and by adjusting the amplification factor of the amplifier circuit 41, it can be equivalent to adjusting the amplifier circuit 41 to connect to the antenna circuit.
  • the size of the capacitance value of the positive capacitance or the negative capacitance is adjusted, which is equivalent to adjusting the overall equivalent capacitance value in the antenna circuit.
  • the fourth capacitor C4 in the matching circuit 20 may be omitted, that is, the matching circuit 20 includes a third capacitor C3, and one end of the third capacitor C3 is connected to the filter circuit 10 to form the first capacitor C3. A node, the other end of the third capacitor C3 is connected to the antenna network circuit 30 to form a second node.
  • the feedback circuit 40 can perform feedback tuning by means of current feedback, that is, when the feedback circuit 40 includes the current source IS, the position where the feedback circuit 40 is connected to the antenna circuit and the feedback circuit 40 include the amplifier circuit 41 and the first capacitor C1
  • the feedback circuit 40 includes the current source IS
  • the position where the feedback circuit 40 is connected to the antenna circuit and the feedback circuit 40 include the amplifier circuit 41 and the first capacitor C1
  • each capacitor (the first capacitor C1 - the fifth capacitor C5 ) used in the antenna circuit is a non-variable capacitor, that is, the capacitance value of each capacitor is a fixed value. , it can be ensured that when other factors in the circuit (such as the inductance value of the inductive element, the capacitance value of the capacitive element, the connection relationship of the elements, etc.) remain unchanged, by adjusting the amplification factor of the amplifier circuit 41 in the feedback circuit 40, the feedback can be adjusted.
  • the circuit 40 is connected to the size of the capacitance value of the antenna circuit, so as to adjust the overall equivalent capacitance value of the antenna circuit, that is, the feedback circuit 40 only plays the role of adjusting the voltage of the connection node, and then only plays the role of adjusting the antenna circuit. the effect of the resonant frequency.
  • the variable capacitor is not included in the antenna circuit, the cost of generating the antenna circuit can also be reduced.
  • the antenna circuit may specifically be a single-ended antenna circuit, that is, the antenna circuit includes a single input voltage Ui, a single filter circuit 10 , a single matching circuit 20 , a single antenna network circuit 30 and a single feedback circuit 40 .
  • the antenna circuit may also be a differential antenna circuit, that is, the antenna circuit includes two input voltages Ui, two symmetrically arranged filter circuits 10, two symmetrically arranged matching circuits 20, a single antenna network circuit 30 and two Symmetrically arranged feedback circuit 40 .
  • FIG. 7 is a schematic diagram of the voltage feedback tuning principle in the embodiment of the application.
  • the voltage of node N is defined as UN
  • the amplifying circuit to realize in-phase amplification or inverting amplification and adjusting the amplification factor, the overall equivalent capacitance value in the antenna circuit can be equivalently adjusted, thereby adjusting the resonant frequency of the antenna circuit to avoid detuning.
  • FIGS. 8 , 9 and 10 are schematic diagram of waveforms of current and voltage
  • FIG. 9 is a schematic diagram of an antenna circuit provided by an embodiment of the application
  • FIG. 10 is a schematic diagram of a current feedback tuning principle in an embodiment of the application, as shown in FIGS. 8 , 9 and 10 .
  • the voltage of node N as UN
  • IN as the current of the current source
  • the current source is equivalent to the effect of a capacitor
  • the current source is equivalent to the effect of an inductor.
  • the overall equivalent capacitance value in the antenna circuit can be adjusted equivalently, so as to adjust the resonant frequency of the antenna circuit to avoid detuning.
  • FIG. 11 is a schematic diagram of a voltage feedback type automatic tuning circuit provided by an embodiment of the application.
  • an NFCC NFC Controller, NFC controller
  • NFC controller NFC Controller
  • the transmitting end TXP and the reverse transmitting end TXN are connected, and the receiving link is connected with the same direction receiving end RXP and the reverse receiving end RXN.
  • the structure inside the box shown by the NFCC is the internal structure of the chip, and the structure outside the box shown by the NFCC is the peripheral device of the chip.
  • the circuit structure shown in FIG. 11 further includes a filter circuit 10 , a matching circuit 20 , an antenna network circuit 30 and a feedback circuit 40 .
  • a filter circuit 10 for the specific structures of the filter circuit 10 , the matching circuit 20 , the antenna network circuit 30 and the feedback circuit 40 , reference may be made to the descriptions of the foregoing embodiments, which will not be repeated here.
  • the resistor Rext (Rext'), the capacitor Cac (Cac'), and the resistor Rp (Rp') constitute the signal input path of the NFCC, that is, the receiving path of the NFC communication.
  • the resistor Rp (used to realize the gain automatic adjustment function) adjusts the resistance value in real time according to the external voltage, and divides the voltage with the external resistor Rext, so that the voltage of the RXP or PXN terminal is within a fixed voltage range, and the capacitor Cac is used to filter out the antenna matching circuit. DC component.
  • the amplification circuit in the feedback circuit 40 realizes the function of inverting amplification, and the amplification factor is
  • a feedback tuning method is provided, which can be applied to the antenna circuit in any of the above embodiments, and the execution body of the method can be a control chip/module/circuit or a processor connected to the antenna circuit, etc. .
  • FIG. 12 is a schematic diagram of a feedback tuning method provided by an embodiment of the present application. As shown in FIG. 12 , the method mainly includes the following steps:
  • the detection of whether the current feedback tuning trigger condition is met may specifically be detecting the resonant frequency of the antenna circuit. If the current resonance frequency of the antenna circuit does not meet the predetermined resonance frequency, it can be determined that the feedback tuning trigger condition is met.
  • detecting whether the trigger condition for feedback tuning is currently satisfied may also be an opportunity to detect whether the current feedback tuning is satisfied.
  • the time when the antenna circuit is powered on can be preset as the timing for performing feedback tuning. When the antenna circuit is powered on each time At startup, feedback tuning is performed on the antenna circuit. It can be understood that the timing of performing feedback tuning may also be other time points, such as the time point when the antenna circuit is fabricated, the time point when the quality of the antenna circuit is detected, and the like.
  • feedback circuits with different magnifications can be equivalent to inserting capacitance values of different sizes into the antenna circuit. Therefore, by adjusting the magnification, the overall equivalent capacitance in the circuit can be adjusted equivalently, thereby changing the The resonant frequency of the antenna circuit, when the voltage of the connecting node is the maximum value, it can be considered that the antenna circuit works at the predetermined resonant frequency, so that the antenna circuit is in a resonant state, thereby ensuring the quality of communication and improving the stability and reliability of communication.
  • the purpose of reducing the cost of the antenna circuit can be achieved.
  • FIG. 13 is a schematic diagram of adjusting the amplification factor of the feedback circuit in the embodiment of the application. As shown in FIG. 13 , according to the voltage of the connection node between the feedback circuit and the matching circuit in the antenna circuit, the amplification factor of the feedback circuit is adjusted, including the following steps:
  • adjusting the magnification of the feedback circuit according to the voltage of the connection node it can be realized by traversing and adjusting the magnification of the feedback circuit, that is, by taking different magnifications of the feedback circuit, and obtaining the connection node at different magnifications.
  • the target amplification factor corresponding to the maximum voltage can be determined as the amplification factor of the feedback circuit, that is, the amplification factor of the feedback circuit can be adjusted to the target amplification factor, thereby making the antenna circuit work at a predetermined resonant frequency to avoid detuning .
  • FIG. 14 is a schematic diagram of respectively acquiring the voltages of the connection nodes when the feedback circuits are at different magnifications in an embodiment of the application. As shown in FIG. 14 , the voltages of the connection nodes when the feedback circuits are at different magnifications are respectively obtained, including the following step:
  • the initial magnification may be the minimum value in the magnification adjustment range.
  • other magnifications may be selected in a manner of changing from the minimum value to the maximum value.
  • the initial magnification can also be the maximum value in the magnification adjustment range.
  • the feedback circuit when the amplification factor of the feedback circuit is adjusted according to the voltage of the connection node, the feedback circuit can be set to different amplification factors, and the voltage of the connection node at different amplification factors can be obtained, which can help to accurately determine the maximum voltage, and further can Accurately determine the target magnification corresponding to the maximum voltage.
  • adjusting the amplification factor of the feedback circuit includes: when the feedback circuit includes an amplifier circuit, adjusting the switching state of each switch in the amplifier circuit and the resistance value of the adjustable resistor; or, when the feedback circuit includes a current source , adjust the phase and magnification of the current source.
  • the amplification factor is adjusted according to the specific structure of the feedback circuit, the capacitance value in the circuit can be adjusted equivalently, and the resonant frequency of the antenna circuit can be changed to meet the predetermined requirements.
  • the frequency requirement is to meet the predetermined resonant frequency to avoid detuning, so as to ensure the communication quality and improve the stability and reliability of the communication.
  • a near field communication NFC control chip is provided, and the near field communication NFC control chip includes the filter circuit, the matching circuit and the feedback circuit in any of the above embodiments.
  • the feedback circuit in the chip By setting the feedback circuit in the chip, the communication quality of the chip can be guaranteed, and the stability and reliability of the chip communication can be improved.
  • the purpose of reducing the cost of the chip can be achieved.
  • a terminal device is provided, and the device includes the above-mentioned near field communication NFC control chip.
  • the communication quality of the device can be guaranteed, and the stability and reliability of the device communication can be improved.
  • the purpose of reducing equipment cost can be achieved.

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Abstract

本申请提供一种天线电路、通信芯片、终端设备及反馈调谐方法，其中，天线电路包括：滤波电路、匹配电路、天线网络电路以及反馈电路；滤波电路用于对输入电压进行滤波处理；匹配电路用于使滤波电路的输出与天线网络电路的输入匹配；反馈电路通过匹配电路中的连接节点与匹配电路连接，反馈电路用于根据连接节点的电压调整反馈电路的放大倍数，以使得连接节点的电压为最大值。本申请中，通过进行放大倍数的调整，可以等效调整电路中的整体等效电容值，从而改变天线电路的谐振频率，使得天线电路处于谐振状态，从而保证通信质量，提高通信的稳定性和可靠性。另外也可以降低天线电路的成本。

Description

天线电路、通信芯片、终端设备及反馈调谐方法 技术领域
本申请涉及通信技术领域，尤其涉及一种天线电路、通信芯片、终端设备及反馈调谐方法。
背景技术
NFC(Near Field Communication，近场通信)技术，以13.56MHz作为载波频率，来传递调制信号。13.56MHz信号的强弱，直接影响着通信信号量大小。理想条件下，NFC天线电路在13.56MHz达到谐振状态，此时天线能得到最大的工作电压，磁场最大，能得到最大的通信信号量，即通信质量最好。
然而，在实际场景中，由于外界影响或者电路内部因素，NFC天线电路会出现谐振频率偏离13.56MHz的情况，导致天线端发射电压减小，磁场减小，通信信号减弱，使得通信质量降低。
发明内容
本申请提供了一种天线电路、通信芯片、终端设备及反馈调谐方法，以保证天线电路的通信质量。
第一方面，本申请实施例提供一种天线电路，包括：滤波电路、匹配电路、天线网络电路以及反馈电路；
所述滤波电路的输入端用于接收输入电压，所述滤波电路的输出端与所述匹配电路的输入端连接，所述匹配电路的输出端与所述天线网络电路的输入端连接；
所述滤波电路用于对所述输入电压进行滤波处理；
所述匹配电路用于使所述滤波电路的输出与所述天线网络电路的输入匹配；
所述反馈电路通过所述匹配电路中的连接节点与所述匹配电路连接，所述反馈电路用于根据所述连接节点的电压调整所述反馈电路的放大倍数，以使得所述连接节点的电压为最大值。
本实施例提供一种天线电路，该天线电路中设置有可以进行放大倍数调整的反馈电路，不同放大倍数的反馈电路可以等效于向天线电路中接入不同大小的电容值，因此通过进行放大倍数的调整，可以等效调整电路中的整体等效电容值，从而改变天线电路的谐振频率，当连接节点的电压为最大值时，可以认为天线电路工作在预定的谐振频率，使得天线电路处于谐振状态，从而保证通信质量，提高通信的稳定性和可靠性。另外，由于不需要在天线电路中设置成本较高的可调电容，因此可以达到降低天线电路成本的目的。
在一些实施例中，所述反馈电路包括放大电路和第一电容，所述第一电容为非可变电容；
所述放大电路的输入端与所述连接节点连接，所述放大电路的输出端与所述第一电容的一端连接，所述第一电容的另一端与所述连接节点连接。
其中，放大电路的放大倍数A可调，放大电路与第一电容的连接方式可以形成一个反馈闭环，通过调整放大电路的放大倍数，可以等效调整天线电路中的整体等效电容值，从而起到调整天线电路的谐振频率的作用。
在一些实施例中，所述放大电路用于实现同相放大或反相放大，以调整所述放大电路的放大倍数，以调整所述反馈电路接入所述天线电路的电容值的大小。
从而，通过调整放大电路的放大倍数，可以等效调整天线电路中的整体等效电容值，从而起到调整天线电路的谐振频率的作用。
在一些实施例中，所述放大电路包括：第一开关、第二开关、第三开关、第四开关、第一可调电阻、第二可调电阻、第三可调电阻以及运算放大器；
所述第一开关的一端接地，所述第一开关的另一端与所述第一可调电阻的一端连接；所述第二开关的一端与所述连接节点连接，所述第二开关的另一端与所述第一可调电阻的所述一端连接；所述第一可调电阻的另一端与所述运算放大器的反相输入端连接；
所述第三开关的一端接地，所述第三开关的另一端与所述第二可调电阻的一端连接；所述第四开关的一端与所述连接节点连接，所述第四开关的另一端与所述第二可调电阻的所述一端连接；所述第二可调电阻的另一端与所述运算放大器的同相输入端连接；
所述第三可调电阻的一端与所述运算放大器的所述反相输入端连接，所述第三可调电阻的另一端与所述运算放大器的输出端连接；
所述运算放大器的输出端作为所述放大电路的所述输出端与所述第一电容的所述一端连接；
所述放大电路用于在所述第一开关和所述第四开关处于闭合状态，且所述第二开关和所述第三开关处于断开状态时，实现同相放大；
所述放大电路还用于在所述第一开关和所述第四开关处于断开状态，且所述第二开关和所述第三开关处于闭合状态时，实现反相放大。
从而，通过上述结构，可以实现放大电路的放大倍数A在A<0以及A>1的范围内进行变化，从而起到调整放大电路的放大倍数的作用。
在一些实施例中，所述放大电路还包括：第四可调电阻；
所述第四可调电阻的一端与所述运算放大器的所述同相输入端连接，所述第四可调电阻的另一端接地。
从而，通过在放大电路中设置第四可调电阻，以使得控制电路可以控制放大电路的放大倍数A在0<A<1的范围内进行变化，从而实现遍历放大电路的所有放大倍数的作用，以便于更准确地确定使连接节点电压为最大值时放大电路的放大倍数。
在一些实施例中，所述反馈电路还包括：控制电路；
所述控制电路与所述放大电路连接，所述控制电路用于控制所述放大电路中各个开关的工作状态以及各个可调电阻的电阻值，以调整所述放大电路的放大倍数。
从而，控制电路用于实现调整放大电路的放大倍数的功能，从而便于确定使连接节点电压为最大值时放大电路的放大倍数。
在一些实施例中，所述反馈电路包括电流源。
本实施例中，通过调整电流源IS的相位以及放大倍数，可以等效于向天线电路中接入正电容或者负电容，从而等效于调整天线电路中的整体等效电容值，从而改变天线电路的谐振频率，使天线电路工作在预定的谐振频率。
在一些实施例中，所述反馈电路与所述匹配电路的连接节点为第一节点，所述第一节点为所述匹配电路与所述滤波电路连接的节点；
所述滤波电路包括第一电感；
所述第一电感的一端与所述输入电压连接，所述第一电感的另一端与所述匹配电路连接以形成所述第一节点。
电感具备“通直流、阻交流”的特性，另外，反馈电路包含第一电容，而电容具备“通交流、阻直流”的特性，从而，当反馈电路连接在第一节点M时，第一电容可以配合第一电感对输入电压进行滤波处理。另外，通过调整放大电路的放大倍数，可以等效调整天线电路中的整体等效电容值，保证天线电路工作在预定的谐振频率以避免失谐。
在一些实施例中，所述反馈电路与所述匹配电路的连接节点为第一节点或者第二节点，所述第一节点为所述匹配电路与所述滤波电路连接的节点，所述第二节点为所述匹配电路与所述天线网络电路连接的节点；
所述滤波电路包括：第一电感以及第二电容，所述第二电容为非可变电容；
所述第一电感的一端与所述输入电压连接，所述第一电感的另一端与所述匹配电路连接以形成所述第一节点，所述第二电容的一端与所述第一节点连接，所述第二电容的另一端接地。
电感具备“通直流、阻交流”的特性，而电容具备“通交流、阻直流”的特性，从而，通过设置第一电感和第二电容，使得滤波电路可以对输入电压进行滤波处理。另外，通过调整放大电路的放大倍数，可以等效调整反馈电路接入的电容值，即调整天线电路的整体等效电容值，保证天线电路工作在预定的谐振频率以避免失谐。
在一些实施例中，所述反馈电路与所述匹配电路的连接节点为第二节点，所述第二节点为所述匹配电路与所述天线网络电路连接的节点；
所述匹配电路包括第三电容，所述第三电容为非可变电容；
所述第三电容的一端与所述滤波电路连接以形成第一节点，所述第三电容的另一端与所述天线网络电路连接以形成所述第二节点。
当反馈电路连接在第二节点时，通过调整放大电路的放大倍数，可以等效调整反馈电路接入的电容值，即调整天线电路的整体等效电容值，保证天线电路工作在预定的谐振频率以避免失谐。
在一些实施例中，所述反馈电路与所述匹配电路的连接节点为第一节点或者第二节点，所述第一节点为所述匹配电路与所述滤波电路连接的节点， 所述第二节点为所述匹配电路与所述天线网络电路连接的节点；
所述匹配电路包括第三电容以及第四电容，所述第三电容以及所述第四电容为非可变电容；
所述第三电容的一端与所述滤波电路连接以形成所述第一节点，所述第三电容的另一端与所述天线网络电路连接以形成所述第二节点；所述第四电容的一端与所述第二节点连接，所述第四电容的另一端接地。
当反馈电路连接在第二节点时，通过调整放大电路的放大倍数，可以等效调整反馈电路接入的电容值，即调整天线电路的整体等效电容值，保证天线电路工作在预定的谐振频率以避免失谐。
在一些实施例中，所述天线网络电路包括第四电阻、第五电容以及第二电感，所述第五电容为非可变电容；
所述第四电阻的一端与所述匹配电路连接以形成第二节点，所述第四电阻的一端还与所述第五电容的一端连接，所述第四电阻的另一端与所述第二电感的一端连接，所述第五电容的另一端以及所述第二电感的另一端接地。
天线网络电路与匹配电路连接，基于匹配电路提供的能量，使得天线网络电路中的第二电感可以发射磁场，从而可以通过磁场进行通信。
第二方面，本申请实施例提供一种反馈调谐方法，应用于上述的天线电路，所述方法包括：
检测当前是否满足反馈调谐触发条件；
在确定满足所述反馈调谐触发条件时，根据所述天线电路中反馈电路与匹配电路的连接节点的电压，调整所述反馈电路的放大倍数，以使得所述连接节点的电压为最大值。
本实施例中，不同放大倍数的反馈电路可以等效于向天线电路中接入不同大小的电容值，因此通过进行放大倍数的调整，可以等效调整电路中的整体等效电容值，从而改变天线电路的谐振频率，当连接节点的电压为最大值时，可以认为天线电路工作在预定的谐振频率，使得天线电路处于谐振状态，从而保证通信质量，提高通信的稳定性和可靠性。另外，由于不需要在天线电路中设置成本较高的可调电容，因此可以达到降低天线电路成本的目的。
在一些实施例中，所述根据所述天线电路中反馈电路与匹配电路的连接 节点的电压，调整所述反馈电路的放大倍数，包括：
分别获取所述连接节点在所述反馈电路为不同的放大倍数时的电压；
确定各所述电压中的最大电压，以及所述最大电压对应的目标放大倍数；
将所述反馈电路的放大倍数调整为所述目标放大倍数。
具体的，在根据连接节点的电压调整反馈电路的放大倍数时，可以通过遍历调整反馈电路的放大倍数的方式实现，即通过将反馈电路取不同的放大倍数，并获取连接节点在不同放大倍数时的电压，根据电路在谐振状态下电压值最大的特性，可以确定在遍历调整的过程中，当连接节点的电压处于最大值时，天线电路处于谐振状态，即天线电路的谐振频率满足预定的谐振频率，因此，可以将最大电压对应的目标放大倍数确定为反馈电路的放大倍数，即将反馈电路的放大倍数调整为该目标放大倍数，从而，使得天线电路工作在预定的谐振频率，以避免失谐。
在一些实施例中，所述分别获取所述连接节点在所述反馈电路为不同的放大倍数时的电压，包括：
将所述反馈电路的放大倍数调整为初始放大倍数，所述初始放大倍数为所述反馈电路的放大倍数调整范围中的任意值；
获取所述连接节点在所述反馈电路为所述初始放大倍数时的电压；
将所述反馈电路的放大倍数调整为其他放大倍数，所述其他放大倍数为所述放大倍数调整范围中与所述初始放大倍数不同的值，并获取所述连接节点在所述反馈电路为所述其他放大倍数时的电压，直至所述放大倍数调整范围中的所有值都存在对应的电压。
本实施例在根据连接节点的电压调整反馈电路的放大倍数时，通过将反馈电路取不同的放大倍数，并获取连接节点在不同放大倍数时的电压，可以有助于准确确定最大电压，进而可以准确确定最大电压对应的目标放大倍数。
在一些实施例中，调整所述反馈电路的放大倍数，包括：
在所述反馈电路包括放大电路时，调整所述放大电路中的各开关的开关状态以及可调电阻的电阻值；或者
在所述反馈电路包括电流源时，调整所述电流源的相位以及放大倍数。
具体的，在反馈电路为电压反馈调谐或者电流反馈调谐时，根据反馈 电路的具体结构进行放大倍数的调整，可以等效调整电路中的电容值，可以改变天线电路的谐振频率，使其满足预定的频率要求，即满足预定的谐振频率以避免失谐，从而保证通信质量，提高通信的稳定性和可靠性。
第三方面，本申请实施例提供一种近场通信NFC控制芯片，包括：上述的滤波电路、匹配电路以及反馈电路。
第四方面，本申请实施例提供一种终端设备，所述设备包括上述的近场通信NFC控制芯片。
本申请提供一种天线电路、通信芯片、终端设备及反馈调谐方法，其中，天线电路包括：滤波电路、匹配电路、天线网络电路以及反馈电路；所述滤波电路的输入端用于接收输入电压，所述滤波电路的输出端与所述匹配电路的输入端连接，所述匹配电路的输出端与所述天线网络电路的输入端连接；所述滤波电路用于对所述输入电压进行滤波处理；所述匹配电路用于使所述滤波电路的输出与所述天线网络电路的输入匹配；所述反馈电路通过所述匹配电路中的连接节点与所述匹配电路连接，所述反馈电路用于根据所述连接节点的电压调整所述反馈电路的放大倍数，以使得所述连接节点的电压为最大值。本申请中，天线电路中设置有可以进行放大倍数调整的反馈电路，不同放大倍数的反馈电路可以等效于向天线电路中接入不同大小的电容值，因此通过进行放大倍数的调整，可以等效调整电路中的整体等效电容值，从而改变天线电路的谐振频率，当连接节点的电压为最大值时，可以认为天线电路工作在预定的谐振频率，使得天线电路处于谐振状态，从而保证通信质量，提高通信的稳定性和可靠性。另外，由于不需要在天线电路中设置成本较高的可调电容，因此可以达到降低天线电路成本的目的。
附图说明
此处的附图被并入说明书中并构成本说明书的一部分，示出了符合本公开的实施例，并与说明书一起用于解释本公开的原理。
图1为本申请实施例提供的天线电路的示意图；
图2a为本申请实施例提供的反馈电路的示意图；
图2b为本申请实施例提供的反馈电路的另一示意图；
图3a为本申请实施例提供的反馈电路的另一示意图；
图3b为本申请实施例提供的反馈电路的另一示意图；
图4为本申请实施例提供的反馈电路的另一示意图；
图5为本申请实施例提供的天线电路的另一示意图；
图6为本申请实施例提供的天线电路的另一示意图；
图7为本申请实施例中的电压反馈调谐原理的示意图；
图8为电流与电压的波形示意图；
图9为本申请实施例提供的天线电路的另一示意图；
图10为本申请实施例中的电流反馈调谐原理的示意图；
图11为本申请实施例提供的电压反馈型自动调谐电路的示意图；
图12为本申请实施例提供的反馈调谐方法的示意图；
图13为本申请实施例中调整反馈电路的放大倍数的示意图；
图14为本申请实施例中分别获取连接节点在反馈电路为不同的放大倍数时的电压的示意图。
通过上述附图，已示出本公开明确的实施例，后文中将有更详细的描述。这些附图和文字描述并不是为了通过任何方式限制本公开构思的范围，而是通过参考特定实施例为本领域技术人员说明本公开的概念。
具体实施方式
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本发明。在本申请实施例中所使用的单数形式的“一种”和“该”也旨在包括多数形式，除非上下文清楚地表示其他含义。
还需要说明的是，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的商品或者系统不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种商品或者系统所固有的要素。在没有更多限制的情况下，由语句“包括一个……” 限定的要素，并不排除在包括要素的商品或者系统中还存在另外的相同要素。
首先对本申请涉及的专业名词进行解释说明：
1、谐振频率(Resonance Frequency)
谐振又称“共振”。振荡系统在周期性外力作用下，当外力作用频率与系统固有振荡频率相同或很接近时，振幅急剧增大的现象。产生谐振时的频率称“谐振频率”。而在含有电容和电感的谐振电路中，可能出现以下情况：(1)在某个时间段内，电容的电压逐渐升高，而电流却逐渐减少；电感的电流逐渐增加，电感的电压却逐渐降低；(2)在另一个时间段内，电容的电压逐渐降低，而电流却逐渐增加；电感的电流逐渐减少，电感的电压却逐渐升高。电压的增加可以达到一个正的最大值，电压的降低也可达到一个负的最大值，同样，电流的方向在这个过程中也会发生正负方向的变化，称为电路发生电的振荡。当谐振电路外部输入电压的正弦频率达到某一特定频率(即该谐振电路的谐振频率)时，谐振电路的感抗与容抗相等，Z＝R，谐振电路对外呈纯电阻性质，即为谐振。发生谐振时，谐振电路将输入放大Q倍，Q为品质因数。
例如，假设品质因数Q为28，那么对于电感L和电容C并联的谐振电路就是电流增大了28倍。对于电感L和电容C串联的谐振电路，就是电压增加了28倍。
由电感L和电容C组成的谐振电路，电路阻抗
Figure PCTCN2020138690-appb-000001
其中，R为电阻，ωL为电感的感抗，
Figure PCTCN2020138690-appb-000002
为电容的容抗。电路的谐振频率也称为电路的固有频率。由于谐振时电路的感抗与容抗相等，即
Figure PCTCN2020138690-appb-000003
所以谐振角频率
Figure PCTCN2020138690-appb-000004
由于ω 0＝2πf 0，所以谐振频率
Figure PCTCN2020138690-appb-000005
谐振频率只由电路本身固有的参数L和C所决定。
2、失谐
失谐是指天线电路的谐振频率偏离预定的谐振频率(13.56MHz)，当天线电路出现失谐时，会导致天线端的发射电压减小，从而导致线圈发射的磁场减小，使得通信信号减弱，进而降低通信质量。
现有技术中，NFC通信芯片中设置有匹配电路，天线线圈通过匹配电路连接到NFC通信芯片，天线线圈用于发射磁场，天线线圈可以等效为 电感，当包含金属的物体(例如卡)靠近含有天线线圈的读卡器设备时，物体内部的金属会形成反相磁场，导致读卡器天线线圈发射的磁场发生变化，使得电感发生变化，并使得谐振频率发生偏离，从而出现失谐的情况。
另外，器件偏差也会导致失谐。器件偏差即元件本身的精度偏差，在天线电路中，主要是电感L和电容C的精度偏差，根据公式
Figure PCTCN2020138690-appb-000006
当L和C存在精度偏差时，也会导致谐振频率发生偏离，从而引起失谐。
针对上述问题，现有技术采用的一种改进方法是通过在天线电路中添加可变电容来达到自动调谐的目的，具体为：将天线电路中的电容设置为可调电容，例如压控电容或者程控电容等，在出现电路失谐的情况时，通过直接调节该可调电容的电容值，使得天线电路工作在预设的谐振频率，从而使得天线电路维持在谐振状态。然而，现有技术的方法需要在天线电路中增加可调电容，从而会导致天线电路的成本增加。
本申请提供的天线电路、通信芯片、终端设备及调谐方法，旨在解决现有技术的如上技术问题，以达到防止失谐以及降低成本的目的。
本申请的主要思路为：根据谐振频率的计算公式
Figure PCTCN2020138690-appb-000007
谐振频率只由天线电路本身固有的电感值L和电容值C所决定，若谐振频率出现偏差，无论原因在于外界因素还是天线电路本身，都可以通过调整天线电路中的电容值的方式来调整谐振频率，使得调整后的谐振频率满足预定的频率要求，使得天线电路处于谐振状态。而当天线电路处于谐振状态时，天线电路中天线网络电路的发射电压为最大值，以便于达到最好的功率传输，因此，在对天线电路进行反馈调谐时，可以将天线电路中的电压作为参考标准，通过测量天线电路中的电压来协助进行反馈调谐处理。
基于此，本申请提供一种天线电路，该天线电路中设置有可以根据连接节点的电压调整放大倍数的反馈电路，不同放大倍数的反馈电路可以等效于反馈电路向天线电路中接入不同大小的电容值，因此通过对放大倍数进行调整，可以等效于调整天线电路中的整体等效电容值，从而改变天线电路的谐振频率，而当连接节点的电压为最大值时，可以认为天线电路工作在预定的谐振频率，从而使得天线电路处于谐振状态，避免失谐。由于不需要在天线电路中设置成本较高的可调电容，因此可以达到降低天线电路成本的目的。
本申请的技术方案，具体可以应用于NFC通信领域，即本申请中的天线电路，具体可以是NFC天线电路；本申请中的通信芯片，具体可以 是NFC通信芯片；本申请中的终端设备，具体可以是支持NFC功能的设备；本申请中的调谐方法，具体可以应用于NFC通信技术中。
下面以具体地实施例对本申请的技术方案以及本申请的技术方案如何解决上述技术问题进行详细说明。下面这几个具体的实施例可以相互结合，对于相同或相似的概念或过程可能在某些实施例中不再赘述。下面将结合附图，对本申请的实施例进行描述。
图1为本申请实施例提供的天线电路的示意图，如图1所示，该天线电路包括：滤波电路10、匹配电路20、天线网络电路30以及反馈电路40。
其中，滤波电路10的输入端用于接收输入电压，滤波电路10的输出端与匹配电路20的输入端连接，匹配电路20的输出端与天线网络电路30的输入端连接。
滤波电路10用于对输入电压进行滤波处理，通过滤波电路10可以起到过滤谐波的作用，使得输入电压经滤波电路10的处理后去除掉或至少去除一部分谐波信号，以提升信号质量。
天线网络电路30用于发射磁场，匹配电路20用于使滤波电路10的输出与天线网络电路30的输入匹配，以得到更好的功率传输，保证天线网络电路30的发射能量。
参考图1，反馈电路40通过匹配电路20中的连接节点与匹配电路20连接。例如，反馈电路40的输入端以及输出端均与图1中的节点M或者节点N连接。
反馈电路40用于根据连接节点的电压调整反馈电路40的放大倍数，以使得连接节点的电压为最大值。
具体的，连接节点的电压是否为最大值，可以间接反映天线电路是否工作在预定的谐振频率，即连接节点的电压可以反映天线电路的当前谐振频率。天线电路的当前谐振频率由天线电路的电容值以及电感值等决定，因此，该连接节点的电压可以认为是由天线电路的整体结构决定。而由于滤波电路10、匹配电路20以及天线网络电路30均为固定的电路结构，因此，在其他因素不变(例如各个电路所包含的电器元件以及连接关系等)的情况下，通过调整反馈电路40的放大倍数，可以等效于调整天线电路的当前谐振频率，由于当前谐振频率可以通过连接节点的电压来直观体 现，因此，在通过调整反馈电路40的放大倍数使得连接节点的电压为最大值时，可以认为通过调整使得天线电路工作在预定的谐振频率。
例如，当反馈电路40在节点M与匹配电路20连接时，可以根据节点M的电压调节反馈电路40的放大倍数；当反馈电路40在节点N与匹配电路20连接时，可以根据节点N的电压调节反馈电路40的放大倍数。
具体的，在根据连接节点的电压调整反馈电路40的放大倍数时，可以通过遍历调整反馈电路40的放大倍数的方式实现，即通过将反馈电路40取不同的放大倍数，并获取连接节点在不同放大倍数时的电压，根据天线电路在谐振状态下电压值最大的特性，可以确定在遍历调整的过程中，当连接节点的电压处于最大值时，天线电路处于谐振状态，因此，可以将最大电压对应的目标放大倍数确定为反馈电路40的放大倍数，并将反馈电路40的放大倍数调整为该目标放大倍数，从而，使得天线电路工作在预定的谐振频率。
可以理解，根据电压与电流的关系：U＝I×R，当电阻R不变时，电流与电压成正比关系，因此，在实际应用中，也可以根据连接节点的电流来调整反馈电路40的放大倍数。根据电流调整反馈电路40的放大倍数的原理与上述根据电压调整反馈电路40的放大倍数的原理相似，在此不再赘述。
可选的，当应用于NFC通信领域时，预定的谐振频率可以是NFC通信技术中用于传递调制信号的载波频率，即13.56MHz。
本实施例提供一种天线电路，该天线电路中设置有可以进行放大倍数调整的反馈电路，不同放大倍数的反馈电路可以等效于向天线电路中接入不同大小的电容值，因此通过进行放大倍数的调整，可以等效调整电路中的整体等效电容值，从而改变天线电路的谐振频率，当连接节点的电压为最大值时，可以认为天线电路工作在预定的谐振频率，使得天线电路处于谐振状态，从而保证通信质量，提高通信的稳定性和可靠性。另外，由于不需要在天线电路中设置成本较高的可调电容，因此可以达到降低天线电路成本的目的。
在一些实施例中，反馈电路40可以通过电压反馈的方式来进行反馈调谐。
图2a为本申请实施例提供的反馈电路40的示意图，如图2a所示，在采用电压反馈的方式进行调谐时，反馈电路40包括放大电路41和第一电容C1，第一电容C1为非可变电容；放大电路41的输入端与连接节点(M或者N)连接，放大电路41的输出端与第一电容C1的一端连接，第一电容C1的另一端与放大电路41所连接的连接节点连接。例如，当放大电路41的输入端与节点M连接时，第一电容C1的另一端也与节点M连接；当放大电路41的输入端与节点N连接时，第一电容C1的另一端也与节点N连接。
其中，放大电路41的放大倍数A可调，放大电路41与第一电容C1的连接方式可以形成一个反馈闭环，通过调整放大电路41的放大倍数，可以等效调整天线电路中的整体等效电容值，从而起到调整天线电路的谐振频率的作用。
可选的，可以在反馈电路40中设置用于调整放大电路41的放大倍数的控制电路。
图2b为本申请实施例提供的反馈电路40的另一示意图，如图2b所示，反馈电路40还包括控制电路42，控制电路42与放大电路41连接，控制电路42用于实现调整放大电路41的放大倍数的功能，从而便于确定使连接节点电压为最大值时放大电路41的放大倍数。
需要说明的是，本申请对控制电路42的具体结构不做限定，控制电路42可以采用现有的电路结构，只要该控制电路42能够结合放大电路41的具体结构起到调整放大电路41的放大倍数的作用即可。
在一些实施例中，放大电路41用于实现同相放大或反相放大，以起到调整放大电路41的放大倍数的作用，以调整反馈电路40接入天线电路的电容值的大小。
具体的，当放大倍数A>1时，使得反馈电路40相当于电感(负电容)，通过向天线电路中加入电感，可以等效减小天线电路中的整体等效电容值；当放大倍数A<1时，使得反馈电路40相当于电容，通过向天线电路中加入电容，可以等效增加天线电路中的整体等效电容值。
从而，通过调整放大电路41的放大倍数，配合第一电容C1，可以调整反馈电路40接入天线电路的电容值的大小，即等效调整天线电路中的整 体等效电容值，从而起到改变天线电路的谐振频率的作用。
在一些实施例中，对反馈电路40的具体结构进行解释说明。
图3a为本申请实施例提供的反馈电路40的示意图，如图3a所示，放大电路41与控制电路42连接，放大电路41包括：第一开关K1、第二开关K2、第三开关K3、第四开关K4、第一可调电阻R1、第二可调电阻R2、第三可调电阻R3以及运算放大器OP。
参考图3a，第一开关K1的一端接地，第一开关K1的另一端与第一可调电阻R1的一端连接；第二开关K2的一端与连接节点连接，第二开关K2的另一端与第一可调电阻R1的一端连接；第一可调电阻R1的另一端与运算放大器OP的反相输入端连接；
第三开关K3的一端接地，第三开关K3的另一端与第二可调电阻R2的一端连接；第四开关K4的一端与连接节点连接，第四开关K4的另一端与第二可调电阻R2的一端连接；第二可调电阻R2的另一端与运算放大器OP的同相输入端连接；
第三可调电阻R3的一端与运算放大器OP的反相输入端连接，第三可调电阻R3的另一端与运算放大器OP的输出端连接；
运算放大器OP的输出端作为放大电路41的输出端与第一电容C1的一端连接，第一电容C1的另一端与放大电路41所连接的连接节点连接；放大电路41用于在第一开关K1和第四开关K4处于闭合状态，且第二开关K2和第三开关K3处于断开状态时，实现同相放大；放大电路41还用于在第一开关K1和第四开关K4处于断开状态，且第二开关K2和第三开关K3处于闭合状态时，实现反相放大。
其中，控制电路42用于控制放大电路41中各个开关的工作状态以及各个可调电阻的电阻值，以调整放大电路41的放大倍数，下面对控制电路调整放大倍数的具体过程进行解释说明：
(1)在放大电路41用于实现反相放大时，控制电路42控制第二开关K2和第三开关K3闭合，控制第一开关K1和第四开关K4断开，控制第一可调电阻R1为最小值，第三可调电阻R3为最大值，此时，放大电路41的放大倍数为
Figure PCTCN2020138690-appb-000008
即此时放大倍数为负的最大倍数；
可选的，可以预先设置放大倍数的区间，例如设置放大倍数为-Amax(-Amax表示放大倍数为负的目标最大倍数，该目标最大倍数可能小于实际的最大倍数)，然后，根据-Amax来调整R3的具体电阻值。也就是说，R3 的电阻值可以不需要调整为R3的实际最大电阻值。
(2)控制电路42控制第三可调电阻R3逐渐减小至最小值，该变化过程中，放大倍数A仍为负值，但放大倍数A的绝对值逐渐减小；
(3)在放大电路41用于实现正相放大时，控制电路42控制第二开关K2和第三开关K3断开，控制第一开关K1和第四开关K4闭合，此时，第三可调电阻R3为最小值，放大电路41的放大倍数为
Figure PCTCN2020138690-appb-000009
即此时放大倍数为正的最大倍数，且放大倍数A>1；
(4)控制电路42控制第三可调电阻R3逐渐增加至最大值，该变化过程中，放大倍数A仍为大于1的值，且放大倍数A逐渐增大。
可选的，可以预先设置放大倍数的区间，例如设置放大倍数为Amax(Amax表示放大倍数为正的目标最大倍数，该目标最大倍数可能小于实际的最大倍数)，然后，根据Amax来调整R3的具体电阻值。也就是说，R3的电阻值可以不需要调整为R3的实际最大电阻值。
从而，通过上述控制过程，控制电路42可以实现放大电路41的放大倍数在A<0以及A>1的范围内进行变化，从而起到调整放大电路41的放大倍数的作用。
可选的，可以通过在放大电路41中设置第四可调电阻，以使得控制电路42可以控制放大电路41的放大倍数在0<A<1的范围内进行变化，从而实现遍历放大电路41的所有放大倍数的作用，以便于更准确地确定使连接节点电压为最大值时放大电路41的放大倍数。
图3b为本申请实施例提供的反馈电路40的另一示意图，如图3b所示，所述放大电路还包括：第四可调电阻R4；第四可调电阻R4的一端与运算放大器OP的同相输入端连接，第四可调电阻R4的另一端接地。
控制电路42可以通过控制第二可调电阻R2以及第四可调电阻R4的电阻值，起到调整第二可调电阻R2与第四可调电阻R4的分压比的作用，从而控制放大电路41的放大倍数在0<A<1的范围内进行变化，该调整过程中，放大倍数
Figure PCTCN2020138690-appb-000010
例如，当R2＝R4时，放大倍数A为0.5。
基于图3a以及图3b所示的电路结构，控制电路42通过调整各开关的开启/关闭状态，以及调整各可调电阻的电阻值，可以实现放大电路的同相放大或者反相放大，并可以对放大电路的放大倍数进行调整，从而可以等效反馈电路40接入天线电路的电容值的大小，即调整天线电路中的整体等效电容值，从而改变天线电路的谐振频率。
在一些实施例中，反馈电路40可以通过电流反馈的方式来进行反馈调谐。
图4为本申请实施例提供的反馈电路40的示意图，如图4所示，在采用电流反馈的方式进行调谐时，反馈电路40包括电流源IS。电流源具体可以是采用程控电流源。
电流源IS的相位以及放大倍数可调，其中，通过调整电流源的相位，可以使得电流源等效为电容或者电感(负电容)，当电流源等效为电容时，相当于向天线电路中加入电容，从而增加天线电路的电容值；当电流源等效为电感时，相当于向天线电路中加入负电容，从而减小天线电路的电容值。另外，通过调整电流源的放大倍数，可以调整加入的电容或者电感的数值，即起到调整增加或者减小的电容值的具体数值的作用。
可选的，反馈电路40还可以包括对电流源IS的相位以及放大倍数进行调整的控制电路(图中未示出)。
本实施例中，通过调整电流源IS的相位以及放大倍数，可以等效于向天线电路中接入正电容或者负电容，从而等效于调整天线电路中的整体等效电容值，从而改变天线电路的谐振频率，使天线电路工作在预定的谐振频率。
在一些实施例中，以反馈电路40包括放大电路41和第一电容C1为例，对天线电路的具体结构进行解释说明。
图5为本申请实施例提供的天线电路的示意图，如图5所示，反馈电路40与匹配电路20的连接节点为第一节点，第一节点为匹配电路20与滤波电路10连接的节点M。滤波电路10包括第一电感L1以及第二电容C2，第二电容C2为非可变电容；第一电感L1的一端与输入电压连接，第一电感L1的另一端与匹配电路20连接以形成第一节点，第二电容C2的一端与第一节点连接，第二电容C2的另一端接地。电感具备“通直流、阻交流”的特性，而电容具备“通交流、阻直流”的特性，从而，通过设置第一电感L1和第二电容C2，使得滤波电路10可以对输入电压进行滤波处理。
在反馈电路40中的第一电容C1连接至节点M时，通过控制放大电路41实现同相放大或反相放大以及通过调整放大电路的放大倍数，可以等效于调整放大电路41向天线电路中接入正电容或者负电容的电容值的大小， 从而等效于调整天线电路中的整体等效电容值。
可选的，参考图5，当反馈电路40与匹配电路20的连接节点为节点M时，滤波电路10中的第二电容C2可省略，即滤波电路10包括第一电感L1；第一电感L1的一端与输入电压Ui连接，第一电感L1的另一端与匹配电路20连接以形成第一节点M。电感具备“通直流、阻交流”的特性，另外，反馈电路40中的第一电容C1也连接至节点M，而电容具备“通交流、阻直流”的特性，从而，当反馈电路40连接在第一节点M时，第一电容C1可以配合第一电感L1对输入电压Ui进行滤波处理。
可选的，参考图5，匹配电路20包括第三电容C3以及第四电容C4，第三电容C3以及第四电容C4为非可变电容；第三电容C3的一端与滤波电路10连接以形成第一节点，第三电容C3的另一端与天线网络电路30连接以形成第二节点；第四电容C4的一端与第二节点连接，第四电容C4的另一端接地。
可选的，参考图5，天线网络电路30包括第四电阻R4、第五电容C5以及第二电感L2，第五电容C5为非可变电容；第四电阻R4的一端与匹配电路20连接以形成第二节点，第四电阻R4的一端还与第五电容C5的一端连接，第四电阻R4的另一端与第二电感L2的一端连接，第五电容C5的另一端以及第二电感L2的另一端接地。
天线网络电路30与匹配电路20连接，基于匹配电路20提供的能量，使得天线网络电路30中的第二电感L2可以发射磁场，从而可以通过磁场进行通信。
图6为本申请实施例提供的天线电路的另一示意图，如图6所示，反馈电路40与匹配电路20的连接节点为第二节点，第二节点为匹配电路20与天线网络电路30连接的节点N。
参考图6，当反馈电路40连接在第二节点时，通过控制放大电路41实现同相放大或反相放大以及通过调整放大电路41的放大倍数，可以等效于调整放大电路41向天线电路中接入正电容或者负电容的电容值的大小，从而等效于调整天线电路中的整体等效电容值。
可选的，当反馈电路40连接在第二节点时，匹配电路20中第四电容C4可省略，即匹配电路20包括第三电容C3，第三电容C3的一端与滤波 电路10连接以形成第一节点，第三电容C3的另一端与天线网络电路30连接以形成第二节点。
可以理解，在反馈电路40可以通过电流反馈的方式来进行反馈调谐，即反馈电路40包括电流源IS时，反馈电路40接入天线电路的位置与反馈电路40包括放大电路41和第一电容C1的情况类似，在此不再赘述。
需要说明的是，本申请各实施例中，天线电路中所使用的各个电容(第一电容C1-第五电容C5)均为非可变电容，即各个电容的电容值为固定值，一方面，可以确保在电路中其他因素(例如电感元件的电感值、电容元件的电容值、元件的连接关系等)不变的情况下，通过调整反馈电路40中放大电路41的放大倍数，可以调整反馈电路40接入天线电路的电容值的大小，从而起到调整天线电路的整体等效电容值的作用，即通过反馈电路40来唯一起到调整连接节点电压的作用，进而唯一起到调整天线电路的谐振频率的作用。另一方面，由于天线电路中不包括可变电容，也可以起到降低天线电路生成成本的作用。
在一些实施例中，天线电路具体可以是单端天线电路，即天线电路中包含单个输入电压Ui、单个滤波电路10、单个匹配电路20、单个天线网络电路30以及单个反馈电路40。
可选的，天线电路也可以是差分天线电路，即天线电路中包含两个输入电压Ui、两个对称设置的滤波电路10、两个对称设置的匹配电路20、单个天线网络电路30以及两个对称设置的反馈电路40。
关于单端天线电路或者差分天线电路中各元件之间的连接，具体可以参考之前实施例中对于电路结构的说明，在此不再赘述。
在一些实施例中，对采用电压反馈的方式进行反馈调谐的原理进行解释说明。
图7为本申请实施例中的电压反馈调谐原理的示意图，如图7所示，定义节点N的电压为UN，则节点P的电压为UP＝A×UN，第一电容C1两端的电压为UN-UP＝(1-A)×UN，若图7左右两个电路中电容消耗的电荷量相等，可以认为左右两个电路等效，即：(1-A)×UN×C1＝UN×C1’，等效电容为：C1’＝(1-A)×C1，因此，通过调整放大电路实现同相放大或反相放大以及调整放大倍数A，即 等效改变电容值。
另外，当A>1时，可以等效为负电容，即等效为电感；当A＝1时，电容值不起作用；当A<1时，等效为正电容。
从而，通过调整放大电路实现同相放大或反相放大以及调整放大倍数，可以等效调整天线电路中的整体等效电容值，从而起到调整天线电路的谐振频率以避免失谐的作用。
在一些实施例中，对采用电流反馈的方式进行反馈调谐的原理进行解释说明。
图8为电流与电压的波形示意图，图9为本申请实施例提供的天线电路的示意图，图10为本申请实施例中的电流反馈调谐原理的示意图，如图8、图9及图10所示，定义节点N的电压为UN，IN为电流源的电流，当电流IN＝A*UN∠90°,电流波形滞后电压波形90°，此时，电流源等效为一个电容的效果；当电流IN＝A*UN∠90°，电流波形超前电压波形90°，此时，电流源等效为一个电感的效果。
假定图10中左右两个电路等效，从节点N来讲，左右两个电路的阻抗相等，其中，右边电路的阻抗为
Figure PCTCN2020138690-appb-000011
左边
Figure PCTCN2020138690-appb-000012
那么可得到
Figure PCTCN2020138690-appb-000013
即C＝A/ω。当A为正数时，对应电流源等效为一个电容的情况；当A为负数时，对应电流源等效为一个电感的情况。
从而，通过调整电流源的相位以及放大倍数，可以等效调整天线电路中的整体等效电容值，从而起到调整天线电路的谐振频率以避免失谐的作用。
图11为本申请实施例提供的电压反馈型自动调谐电路的示意图，如图11所示，NFCC(NFC Controller，NFC控制器)包括发射链路以及接收链路，其中，发射链路与同向发射端TXP以及反向发射端TXN连接，接收链路与同向接收端RXP和反向接收端RXN连接。NFCC所示方框内的结构为芯片内部结构，NFCC所示方框外的结构为芯片外围器件。
此外，图11所示电路结构还包括滤波电路10、匹配电路20、天线网络电路30以及反馈电路40。关于滤波电路10、匹配电路20、天线网络电路30以及反馈电路40的具体结构，可以参考前述各实施例的描述，在此不再赘述。
另外，电阻Rext(Rext’)、电容Cac(Cac’)和电阻Rp(Rp’)构成NFCC的信号输入路径，即NFC通信的接收路径。电阻Rp(用于实现增益自动调节功能)根据外部电压实时调节阻值，与外部电阻Rext分压， 使得RXP或PXN端的电压在一个固定的电压范围内，电容Cac用于滤除天线匹配电路的直流分量。
参考图11，当反馈电路40中开关K1和K4处于闭合状态，开关K2和K3处于断开状态时，此时反馈电路40中的放大电路实现同相放大的功能，放大倍数
Figure PCTCN2020138690-appb-000014
(需要Rin1>>R1\R2)。
另外，当开关K1和K4处于断开状态，开关K2和K3处于闭合状态时，此时反馈电路40中的放大电路实现反相放大的功能，放大倍数
Figure PCTCN2020138690-appb-000015
在一些实施例中，提供一种反馈调谐方法，该方法可以应用于以上任一实施例中的天线电路，该方法的执行主体可以是与天线电路连接的控制芯片/模块/电路或者处理器等。
图12为本申请实施例提供的反馈调谐方法的示意图，如图12所示，该方法主要包括以下步骤：
S100、检测当前是否满足反馈调谐触发条件；
S200、在确定满足反馈调谐触发条件时，根据天线电路中反馈电路与匹配电路的连接节点的电压，调整反馈电路的放大倍数，以使得连接节点的电压为最大值。
其中，检测当前是否满足反馈调谐触发条件，具体可以是对天线电路的谐振频率进行检测，若天线电路当前的谐振频率不满足预定的谐振频率，则可以确定满足反馈调谐触发条件。
另外，检测当前是否满足反馈调谐触发条件，也可以是检测当前是否满足进行反馈调谐的时机，例如，可以预设天线电路上电开机的时间为进行反馈调谐的时机，当天线电路每次上电开机时，都对天线电路进行反馈调谐。可以理解，进行反馈调谐的时机也可以是其他时间点，例如天线电路制作完成的时间点，进行天线电路质量检测的时间点等。
本实施例中，不同放大倍数的反馈电路可以等效于向天线电路中接入不同大小的电容值，因此通过进行放大倍数的调整，可以等效调整电路中的整体等效电容值，从而改变天线电路的谐振频率，当连接节点的电压为最大值时，可以认为天线电路工作在预定的谐振频率，使得天线电路处于谐振状态，从而保证通信质量，提高通信的稳定性和可靠性。另外，由于不需要在天线电路中设置成本较高的可调电容，因此可以达到降低天线电 路成本的目的。
图13为本申请实施例中调整反馈电路的放大倍数的示意图，如图13所示，根据天线电路中反馈电路与匹配电路的连接节点的电压，调整反馈电路的放大倍数，包括以下步骤：
S210、分别获取连接节点在反馈电路为不同的放大倍数时的电压；
S220、确定各电压中的最大电压，以及最大电压对应的目标放大倍数；
S230、将反馈电路的放大倍数调整为目标放大倍数。
具体的，在根据连接节点的电压调整反馈电路的放大倍数时，可以通过遍历调整反馈电路的放大倍数的方式实现，即通过将反馈电路取不同的放大倍数，并获取连接节点在不同放大倍数时的电压，根据电路在谐振状态下电压值最大的特性，可以确定在遍历调整的过程中，当连接节点的电压处于最大值时，天线电路处于谐振状态，即天线电路的谐振频率满足预定的谐振频率，因此，可以将最大电压对应的目标放大倍数确定为反馈电路的放大倍数，即将反馈电路的放大倍数调整为该目标放大倍数，从而，使得天线电路工作在预定的谐振频率，以避免失谐。
图14为本申请实施例中分别获取连接节点在反馈电路为不同的放大倍数时的电压的示意图，如图14所示，分别获取连接节点在反馈电路为不同的放大倍数时的电压，包括以下步骤：
S212、将反馈电路的放大倍数调整为初始放大倍数，初始放大倍数为反馈电路的放大倍数调整范围中的任意值；
S214、获取连接节点在反馈电路为初始放大倍数时的电压；
S216、将反馈电路的放大倍数调整为其他放大倍数，其他放大倍数为放大倍数调整范围中与初始放大倍数不同的值，并获取连接节点在反馈电路为其他放大倍数时的电压，直至放大倍数调整范围中的所有值都存在对应的电压。
具体的，初始放大倍数可以为放大倍数调整范围中的最小值，在更改放大倍数时，可以按照由最小值向最大值变化的方式，选择其他放大倍数的取值。
可选的，初始放大倍数也可以为放大倍数调整范围中的最大值，在更改放大倍数时，可以按照由最大值向最小值变化的方式，选择其他放大倍 数的取值。
可选的，更改放大倍数的方式，也可以选择其他方法，例如二分法等，本实施例对更改放大倍数的具体方式不做限定。
本实施例在根据连接节点的电压调整反馈电路的放大倍数时，通过将反馈电路取不同的放大倍数，并获取连接节点在不同放大倍数时的电压，可以有助于准确确定最大电压，进而可以准确确定最大电压对应的目标放大倍数。
在一些实施例中，调整反馈电路的放大倍数，包括：在反馈电路包括放大电路时，调整放大电路中的各开关的开关状态以及可调电阻的电阻值；或者，在反馈电路包括电流源时，调整电流源的相位以及放大倍数。
具体的，在反馈电路为电压反馈调谐或者电流反馈调谐时，根据反馈电路的具体结构进行放大倍数的调整，可以等效调整电路中的电容值，可以改变天线电路的谐振频率，使其满足预定的频率要求，即满足预定的谐振频率以避免失谐，从而保证通信质量，提高通信的稳定性和可靠性。
应该理解的是，虽然上述实施例中的流程图中的各个步骤按照箭头的指示依次显示，但是这些步骤并不是必然按照箭头指示的顺序依次执行。除非本文中有明确的说明，这些步骤的执行并没有严格的顺序限制，其可以以其他的顺序执行。而且，图中的至少一部分步骤可以包括多个子步骤或者多个阶段，这些子步骤或者阶段并不必然是在同一时刻执行完成，而是可以在不同的时刻执行，其执行顺序也不必然是依次进行，而是可以与其他步骤或者其他步骤的子步骤或者阶段的至少一部分轮流或者交替地执行。
在一些实施例中，提供一种近场通信NFC控制芯片，该近场通信NFC控制芯片包括以上任一实施例中的滤波电路、匹配电路以及反馈电路。通过在芯片中设置反馈电路，可以保证芯片的通信质量，提高芯片通信的稳定性和可靠性。另外，由于不需要在芯片中设置成本较高的可调电容，因此可以达到降低芯片成本的目的。
在一些实施例中，提供一种终端设备，该设备包括上述的近场通信NFC控制芯片。通过在设备的芯片中设置反馈电路，可以保证设备的通信质量，提高设备通信的稳定性和可靠性。另外，由于不需要在芯片中设置成本较 高的可调电容，因此可以达到降低设备成本的目的。
本领域技术人员在考虑说明书及实践这里公开的申请后，将容易想到本公开的其它实施方案。本申请旨在涵盖本公开的任何变型、用途或者适应性变化，这些变型、用途或者适应性变化遵循本公开的一般性原理并包括本公开未公开的本技术领域中的公知常识或惯用技术手段。说明书和实施例仅被视为示例性的，本公开的真正范围和精神由下面的权利要求书指出。
应当理解的是，本公开并不局限于上面已经描述并在附图中示出的精确结构，并且可以在不脱离其范围进行各种修改和改变。本公开的范围仅由所附的权利要求书来限制。

Claims (18)

  1. 一种天线电路，其特征在于，包括：滤波电路、匹配电路、天线网络电路以及反馈电路；
    所述滤波电路的输入端用于接收输入电压，所述滤波电路的输出端与所述匹配电路的输入端连接，所述匹配电路的输出端与所述天线网络电路的输入端连接；
    所述滤波电路用于对所述输入电压进行滤波处理；
    所述匹配电路用于使所述滤波电路的输出与所述天线网络电路的输入匹配；
    所述反馈电路通过所述匹配电路中的连接节点与所述匹配电路连接，所述反馈电路用于根据所述连接节点的电压调整所述反馈电路的放大倍数，以使得所述连接节点的电压为最大值。
  2. 根据权利要求1所述的天线电路，其特征在于，所述反馈电路包括放大电路和第一电容，所述第一电容为非可变电容；
    所述放大电路的输入端与所述连接节点连接，所述放大电路的输出端与所述第一电容的一端连接，所述第一电容的另一端与所述连接节点连接。
  3. 根据权利要求2所述的天线电路，其特征在于，所述放大电路用于实现同相放大或反相放大，以调整所述反馈电路接入所述天线电路的电容值的大小以调整所述放大电路的放大倍数。
  4. 根据权利要求3所述的天线电路，其特征在于，所述放大电路包括：第一开关、第二开关、第三开关、第四开关、第一可调电阻、第二可调电阻、第三可调电阻以及运算放大器；
    所述第一开关的一端接地，所述第一开关的另一端与所述第一可调电阻的一端连接；所述第二开关的一端与所述连接节点连接，所述第二开关的另一端与所述第一可调电阻的所述一端连接；所述第一可调电阻的另一端与所述运算放大器的反相输入端连接；
    所述第三开关的一端接地，所述第三开关的另一端与所述第二可调电阻的一端连接；所述第四开关的一端与所述连接节点连接，所述第四开关的另一端与所述第二可调电阻的所述一端连接；所述第二可调电阻的另一端与所述运算放大器的同相输入端连接；
    所述第三可调电阻的一端与所述运算放大器的所述反相输入端连接，所述第三可调电阻的另一端与所述运算放大器的输出端连接；
    所述运算放大器的输出端作为所述放大电路的所述输出端与所述第一电容的所述一端连接；
    所述放大电路用于在所述第一开关和所述第四开关处于闭合状态，且所述第二开关和所述第三开关处于断开状态时，实现同相放大；
    所述放大电路还用于在所述第一开关和所述第四开关处于断开状态，且所述第二开关和所述第三开关处于闭合状态时，实现反相放大。
  5. 根据权利要求4所述的天线电路，其特征在于，所述放大电路还包括：第四可调电阻；
    所述第四可调电阻的一端与所述运算放大器的所述同相输入端连接，所述第四可调电阻的另一端接地。
  6. 根据权利要求5所述的天线电路，其特征在于，所述反馈电路还包括：控制电路；
    所述控制电路与所述放大电路连接，所述控制电路用于控制所述放大电路中各个开关的工作状态以及各个可调电阻的电阻值，以调整所述放大电路的放大倍数。
  7. 根据权利要求1所述的天线电路，其特征在于，所述反馈电路包括电流源。
  8. 根据权利要求1-7任一项所述的天线电路，其特征在于，所述反馈电路与所述匹配电路的连接节点为第一节点，所述第一节点为所述匹配电路与所述滤波电路连接的节点；
    所述滤波电路包括第一电感；
    所述第一电感的一端与所述输入电压连接，所述第一电感的另一端与所述匹配电路连接以形成所述第一节点。
  9. 根据权利要求1-7任一项所述的天线电路，其特征在于，所述反馈电路与所述匹配电路的连接节点为第一节点或者第二节点，所述第一节点为所述匹配电路与所述滤波电路连接的节点，所述第二节点为所述匹配电路与所述天线网络电路连接的节点；
    所述滤波电路包括：第一电感以及第二电容，所述第二电容为非可变电 容；
    所述第一电感的一端与所述输入电压连接，所述第一电感的另一端与所述匹配电路连接以形成所述第一节点，所述第二电容的一端与所述第一节点连接，所述第二电容的另一端接地。
  10. 根据权利要求1-7任一项所述的天线电路，其特征在于，所述反馈电路与所述匹配电路的连接节点为第二节点，所述第二节点为所述匹配电路与所述天线网络电路连接的节点；
    所述匹配电路包括第三电容，所述第三电容为非可变电容；
    所述第三电容的一端与所述滤波电路连接以形成第一节点，所述第三电容的另一端与所述天线网络电路连接以形成所述第二节点。
  11. 根据权利要求1-7任一项所述的天线电路，其特征在于，所述反馈电路与所述匹配电路的连接节点为第一节点或者第二节点，所述第一节点为所述匹配电路与所述滤波电路连接的节点，所述第二节点为所述匹配电路与所述天线网络电路连接的节点；
    所述匹配电路包括第三电容以及第四电容，所述第三电容以及所述第四电容为非可变电容；
    所述第三电容的一端与所述滤波电路连接以形成所述第一节点，所述第三电容的另一端与所述天线网络电路连接以形成所述第二节点；所述第四电容的一端与所述第二节点连接，所述第四电容的另一端接地。
  12. 根据权利要求1-7任一项所述的天线电路，其特征在于，所述天线网络电路包括第四电阻、第五电容以及第二电感，所述第五电容为非可变电容；
    所述第四电阻的一端与所述匹配电路连接以形成第二节点，所述第四电阻的一端还与所述第五电容的一端连接，所述第四电阻的另一端与所述第二电感的一端连接，所述第五电容的另一端以及所述第二电感的另一端接地。
  13. 一种反馈调谐方法，应用于权利要求1-12任一项所述的天线电路，其特征在于，所述方法包括：
    检测当前是否满足反馈调谐触发条件；
    在确定满足所述反馈调谐触发条件时，根据所述天线电路中反馈电路与匹配电路的连接节点的电压，调整所述反馈电路的放大倍数，以使得所述连 接节点的电压为最大值。
  14. 根据权利要求13所述的方法，其特征在于，所述根据所述天线电路中反馈电路与匹配电路的连接节点的电压，调整所述反馈电路的放大倍数，包括：
    分别获取所述连接节点在所述反馈电路为不同的放大倍数时的电压；
    确定各所述电压中的最大电压，以及所述最大电压对应的目标放大倍数；
    将所述反馈电路的放大倍数调整为所述目标放大倍数。
  15. 根据权利要求14所述的方法，其特征在于，所述分别获取所述连接节点在所述反馈电路为不同的放大倍数时的电压，包括：
    将所述反馈电路的放大倍数调整为初始放大倍数，所述初始放大倍数为所述反馈电路的放大倍数调整范围中的任意值；
    获取所述连接节点在所述反馈电路为所述初始放大倍数时的电压；
    将所述反馈电路的放大倍数调整为其他放大倍数，所述其他放大倍数为所述放大倍数调整范围中与所述初始放大倍数不同的值，并获取所述连接节点在所述反馈电路为所述其他放大倍数时的电压，直至所述放大倍数调整范围中的所有值都存在对应的电压。
  16. 根据权利要求13-15任一项所述的方法，其特征在于，调整所述反馈电路的放大倍数，包括：
    在所述反馈电路包括放大电路时，调整所述放大电路中的各开关的开关状态以及可调电阻的电阻值；或者
    在所述反馈电路包括电流源时，调整所述电流源的相位以及放大倍数。
  17. 一种近场通信NFC控制芯片，其特征在于，包括：如权利要求1-12任一项所述的滤波电路、匹配电路以及反馈电路。
  18. 一种终端设备，其特征在于，所述设备包括如权利要求17所述的近场通信NFC控制芯片。
PCT/CN2020/138690 2020-12-23 2020-12-23 天线电路、通信芯片、终端设备及反馈调谐方法 WO2022133823A1 (zh)

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