Antenna tuning system suitable for medium wave

Abstract

The invention provides an antenna tuning system suitable for medium waves, which belongs to the field of medium and long wave transmitter communication, and comprises a standing wave detection circuit, a servo detection circuit, an antenna tuning monitoring unit, a direct current motor, an impedance transformer, a variable inductance coil, a fixed tap inductance coil, a relay group I, a relay group II and a lightning arrester, the standing wave detection circuit carries out forward and reverse power sampling on signals to the antenna tuning monitoring unit to serve as a basis for judging whether tuning is carried out or not; a radio frequency input signal enters the servo detection circuit and samples a power signal entering the antenna tuning unit through servo detection to obtain a voltage signal and a current signal; when the voltage and the current are in the same direction, the load is resistive, and the motor is immobile, and when the voltage and the current are in different directions, the load is reactive, and the motor is controlled to rotate to change the inductance value of the variable inductance coil; and the radio frequency signal is transmitted to the antenna through the impedance transformer, the variable inductance coil, the fixed tap inductance coil and the lightning arrester in sequence.

Description

Technical Field

[0001] The present invention belongs to the field of medium and long wave transmitter communication, and particularly relates to an antenna tuning system capable of adjusting antenna operating parameters to optimize communication performance. Background Art

[0002] Traditional antennas usually can only operate within a specific frequency range. When the communication frequency changes, the impedance matching of the antenna is poor, resulting in serious signal reflection and a significant reduction in transmission efficiency; different communication environments (such as temperature, humidity, electromagnetic interference, etc.) will have a significant impact on the antenna performance. Existing antennas are difficult to adapt to these environmental changes, thereby affecting communication quality and stability; in the case of the increasing demand for multi-band communication, traditional antennas cannot flexibly switch frequencies, restricting the versatility and application scope of communication devices. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an antenna tuning system applicable to medium waves for the deficiencies of the background art, effectively solving the key problems such as impedance matching problems, poor environmental adaptability, and inflexible frequency band switching existing in existing antennas, thereby significantly improving the overall performance, stability, and reliability of the communication system, and providing a solid guarantee for various communication applications.

[0004] The present invention adopts the following technical solutions to solve the above technical problems: The present invention provides an antenna tuning system, which includes a standing wave detection circuit, a servo detection circuit, an antenna tuning monitoring unit, a DC motor, an impedance converter, a variable inductance coil, a fixed tap inductance coil, a first relay group and a second relay group, and a lightning arrester; during tuning, the external transmitter control unit sends the impedance parameters, motor tuning parameters, and fixed tap inductance parameters corresponding to the pre-stored operating frequencies to the antenna tuning monitoring unit through the network port. The antenna tuning monitoring unit issues the impedance parameter, motor tuning parameter, and fixed tap inductance parameter commands to the first relay group, the servo detection circuit, and the second relay group respectively; when the radio frequency output signal of the external transmitter enters the standing wave detection circuit, forward and reverse power coupling is performed, and the coupled signal is sent to the antenna tuning monitoring unit to be converted into a standing wave ratio. The value of the standing wave ratio less than 1.3 is used as the judgment basis for successful tuning; the radio frequency output signal sequentially enters the servo detection circuit to detect the power signal entering the antenna tuning unit through servo detection, and the corresponding voltage and current signals are collected; when the voltage and current are in the same direction, the load is resistive and the motor does not move. When the voltage and current are not in the same direction, the load is reactive, and the motor is controlled to rotate to change the inductance value of the variable inductance coil; the radio frequency signal then sequentially passes through the impedance converter, the variable inductance coil, the fixed tap inductance coil, and the lightning arrester to transmit the signal to the antenna, making the antenna in a series resonance state; As a further preferred embodiment of the antenna tuning system of the present invention, the standing wave detection circuit includes a forward RF signal coupling circuit, a reverse RF signal coupling circuit, and a diode detection circuit. The output RF signal of the external transmitter is sampled and then converted into a voltage signal by the diode detection circuit. Finally, the two voltage signals are connected to the single-chip microcomputer of the antenna tuning monitoring unit through an operational amplifier.

[0005] As a further preferred embodiment of the antenna tuning system of the present invention, the servo detection circuit includes a current mutual inductance coupler, a phase detection, and a control circuit. The current sampling signal is used as a switching signal and added to the detector circuit. After the capacitive voltage coupling signal is detected, a positive voltage will be output; after the inductive voltage coupling signal is detected, a negative voltage will be output, successfully realizing phase detection. According to the polarity of the voltage output by the phase detection, the DC motor is driven to change the inductance of the adjustable inductance coil, so that the antenna is in a series resonance state.

[0006] As a further preferred embodiment of the antenna tuning system of the present invention, the antenna tuning monitoring unit includes a single-chip microcomputer and a network chip; the single-chip microcomputer has a storage unit for storing impedance parameters corresponding to the operating frequency, motor tuning parameters, fixed tap inductance and other parameters. The stored data is used for each tuning call, and then these parameters are used to set the relay group of the impedance converter, the servo detection circuit, and the relay group of the fixed tap inductance through the single-chip microcomputer respectively.

[0007] Compared with the prior art, the present invention adopts the above technical solutions and has the following technical effects: Compared with the existing antenna tuner of the present invention, when the communication frequency changes or the external environment changes, the impedance matching of the antenna is not good. Personnel need to carry tools to the installation location to open the equipment chassis and manually change the impedance of the impedance converter and the inductance of the fixed tap inductance coil. When the communication operating frequency changes in the present invention, the servo detection circuit will automatically control the motor to change the inductance of the variable inductor through the phase detection circuit for automatic tuning. The antenna tuning monitoring unit can receive data through the network port, and then control the relay group to switch the impedance and switch the inductance of the fixed tap inductance coil for impedance matching, realizing full-automatic tuning, flexible frequency band switching, and simplified tuning. There is no need for personnel to open the equipment chassis and use tools to manually switch, saving tuning time and preventing the risk of personnel operating with the chassis open without remembering to cut off the power. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is the schematic diagram of the antenna tuning system provided by the present invention; Figure 2 is the schematic diagram of the standing wave detection circuit provided by the present invention; Figure 3It is the schematic diagram of the servo detection circuit provided by the present invention; Figure 4 It is the schematic diagram of the antenna tuning monitoring unit provided by the present invention; Figure 5 It is the circuit diagram of the standing wave detection circuit of the present invention; Figure 6 It is the circuit diagram of the servo detection circuit of the present invention; Figure 7 It is the circuit diagram of the single-chip microcomputer of the antenna tuning monitoring unit of the present invention. Detailed implementation manners

[0009] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings: The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. The present invention will be described in detail below according to the accompanying drawings and preferred embodiments, and the purpose and effect of the present invention will become more obvious. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0010] An antenna tuning system applicable to medium wave, as Figure 1 shown, includes a standing wave detection circuit, a servo detection circuit, an antenna tuning monitoring unit, a DC motor, an impedance converter, a variable inductance coil, a fixed tap inductance coil, a relay group one, a relay group two, and a lightning arrester; During tuning, the control unit of the external transmitter sends the impedance parameters, motor tuning parameters, and fixed tap inductance parameters corresponding to the pre-stored operating frequency to the antenna tuning monitoring unit through the network port, and the antenna tuning monitoring unit issues the impedance parameters, motor tuning parameters, and fixed tap inductance parameter instructions to the relay group one, the servo detection circuit, and the relay group two respectively; When the radio frequency output signal of the external transmitter enters the standing wave detection circuit, forward and reverse power coupling is performed, and the coupled signal is sent to the antenna tuning monitoring unit to be converted into a standing wave ratio. The value of the standing wave ratio less than 1.3 is used as the judgment basis for successful tuning; the radio frequency output signal enters the servo detection circuit in sequence to detect the power signal entering the antenna tuning unit through servo detection, and the corresponding voltage and current signals are collected; when the voltage and current are in the same direction, the load is resistive and the motor does not move, when the voltage and current are not in the same direction, the load is reactive, and the motor is controlled to rotate to change the inductance value of the variable inductance coil; the radio frequency signal is then transmitted to the antenna through the impedance converter, variable inductance coil, fixed tap inductance coil, and lightning arrester in sequence, so that the antenna is in a series resonance state.

[0011] As Figure 2 shown, the standing wave detection circuit includes a forward RF coupling circuit, a reverse RF coupling circuit, and a diode detection circuit. The output RF signal of the external transmitter passes through the coupling circuit and then through the diode detection circuit to convert the RF signal into a required voltage signal and output it to the antenna tuner monitoring unit; the forward power sampling and reverse power sampling signals obtained by the standing wave detection circuit are then used by the antenna tuner monitoring unit to calculate the standing wave ratio, and determine whether the standing wave ratio reaches the appropriate range according to the reference value set during the previous debugging. Only when the appropriate range is reached is the tuning successful; Among them, the forward power sampling signal and the reverse power sampling signal , the antenna tuner monitoring unit uses a formula to calculate the standing wave ratio SWR, and the specific calculation is as follows: ; When the transmitter and the antenna are perfectly matched, the standing wave ratio SWR = 1. If the transmitter is not matched, that is, there is a standing wave, then SWR > 1. Generally, SWR < 1.3 meets the transmission requirements.

[0012] As Figure 3 shown, the servo detection circuit includes a current mutual inductance coupler, a double-phase detection circuit, and a motor control circuit; The output signal of the external transmitter first passes through the standing wave detection circuit and then through the servo detection circuit. The servo detection circuit samples the current and voltage and then compares the phases, and converts them into appropriate voltage signals to drive the DC motor to rotate, changing the inductance of the adjustable inductance coil to make the antenna in a series resonance state; Among them, the double-phase detection circuit compares the phases of the RF current and the RF voltage, and uses phase detection to determine whether the antenna circuit is capacitive or inductive; the capacitive voltage sampling signal will output a positive voltage after detection; while the inductive voltage sampling signal will output a negative voltage after detection, successfully realizing phase detection, and driving the DC motor according to the polarity of the output voltage of the phase detection, changing the inductance of the adjustable inductance coil to make the antenna in a series resonance state; The double-phase detection circuit outputs a DC voltage signal in the positive half cycle of the current sampling signal and also outputs a DC negative voltage signal in the negative half cycle of the current sampling signal; The motor control circuit includes two groups of relay switches, which switch the voltage signal from the double-phase detection circuit and the motor control command from the antenna tuner monitoring unit. When the antenna tuning system automatically tunes, the voltage signal from the double-phase detection circuit is used to drive the DC motor. When the antenna tuning system software manually tunes, the motor control command from the antenna tuner monitoring unit is used to drive the DC motor.

[0013] As Figure 4As shown, the antenna tuner monitoring unit includes a single-chip microcomputer and a network chip; the circuit diagram of the single-chip microcomputer of the antenna tuner monitoring unit is as Figure 7 shown.

[0014] Among them, the single-chip microcomputer has a storage unit for storing impedance parameters corresponding to the operating frequency, motor tuning parameters, and fixed tap inductor parameters. The stored data is used for calling during each tuning, and then these parameters are used to set the impedance converter, DC motor, and fixed tap inductor through the single-chip microcomputer respectively; The network chip is used for network communication between the antenna tuner monitoring unit and the external transmitter control unit, receiving data such as impedance parameters, motor tuning parameters, and fixed tap inductor parameters sent by the external transmitter control unit, and real-time feedback of the tuning status parameters of the antenna tuning system to the external transmitter; When the antenna tuner monitoring unit tunes, first set the impedance parameters, motor tuning parameters, and fixed tap inductor parameters to the corresponding relay group one, servo detection circuit, and relay group two respectively. Then, the dual-phase detection circuit in the servo detection circuit converts the RF signal of the current mutual inductance coupler into a voltage signal with polarity, drives the motor, changes the inductance of the adjustable inductor coil, performs automatic tuning, searches for the resonance point, makes the antenna in a series resonance state. At the same time, the coupled signal of the standing wave detection circuit is converted into a voltage signal and output to the antenna tuner monitoring unit. The voltage signal is converted into a numerical standing wave ratio through the single-chip microcomputer. According to the size of the standing wave ratio, it is judged whether the tuning is successful. If not, then cooperate with the software algorithm of the single-chip microcomputer to send a motor control instruction to the servo detection circuit, make the motor rotate one week, search for the resonance point. After finding the resonance point, make the motor rotate to the angle of the resonance point. If the resonance point has not been found all the time, the single-chip microcomputer sends an alarm signal to the external transmitter control unit through the network chip, requesting manual tuning.

[0015] The speed of the DC motor is 1RPM, and it can be more accurately adjusted to the required angle of the motor during tuning. The DC motor is controlled by the antenna tuner monitoring unit to drive the servo detection circuit to perform automatic tuning and manual tuning.

[0016] The impedance converter is used to match the impedance of the transmitter to the impedance of different antennas, and the impedance is adjusted by changing different taps on the impedance converter.

[0017] The variable inductor coil is used to change the inductance of the variable inductor coil by the angle of motor rotation.

[0018] The fixed tap inductor coil is used to meet the emission requirements of different operating frequencies.

[0019] When the antenna tuner monitoring unit of Relay Group 1 receives the impedance parameters sent by the external transmitter control unit through the network port on the same day, the antenna tuner monitoring unit sends an instruction to the relay group to switch the taps of the impedance transformer to cope with the change in antenna impedance when the transmission frequency is changed.

[0020] For Relay Group 2, when the antenna tuner monitoring unit receives the fixed tap inductance parameters sent by the external transmitter control unit through the network port, the antenna tuner monitoring unit sends an instruction to the relay group to switch the taps of the fixed tap inductance coil to cope with the change in antenna impedance when the transmission frequency is changed.

[0021] As Figure 5 shown, the standing wave detection circuit includes resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, capacitor C1, capacitor C2, inductor L1, inductor L2, transmitter output signal terminal, transmitter output signal output terminal, forward coupling output terminal, and reverse coupling output terminal. Among them, the transmitter output signal terminal is respectively connected to the transmitter output signal output terminal and one end of inductor L2, the other end of inductor L2 is grounded, the forward coupling output terminal is respectively connected to one end of resistor R1 and one end of resistor R3, the other end of resistor R3 is grounded, the other end of resistor R1 is respectively connected to one end of resistor R4 and one end of capacitor C1, the other end of capacitor C1 is respectively connected to one end of resistor R5, one end of resistor R6, one end of capacitor C2, and one end of inductor L1, the other end of inductor L1 is grounded, the other ends of resistor R5 and resistor R6 are respectively grounded, the other end of capacitor C2 is respectively connected to one end of resistor R2 and one end of resistor R7, the other end of resistor R2 is respectively connected to the reverse coupling output terminal and one end of resistor R8, and the other ends of resistor R7 and resistor R8 are respectively grounded.

[0022] As Figure 6As shown, the servo detection circuit includes capacitor C3, capacitor C4, capacitor C5, capacitor C6, resistor R9, resistor R10, resistor R11, resistor R12, diode D1, diode D2, diode D3, diode D4, diode D5, diode D6, diode D7, diode D8, diode D9, diode D10, diode D11, triode Q1, triode Q2, triode Q3, and triode Q4; wherein, one end of capacitor C3 is connected to one end of capacitor C4, and the other end of capacitor C4 is respectively connected to one end of diode D1, one end of diode D3, one end of resistor R9, one end of diode D5, and one end of diode D7. The other end of diode D1 is connected to one end of diode D2, the other end of diode D3 is connected to one end of diode D4, and the other end of diode D4 is respectively connected to the other end of diode D2, the base of triode Q1, and one end of capacitor C5. The other end of capacitor C5 is connected to the emitter of triode Q1 and grounded. The collector of triode Q1 is respectively connected to one end of resistor R11 and one end of diode D10, the base of triode Q2. The emitter of triode Q2 is connected to the other end of diode D10. The other end of resistor R11 is respectively connected to the collector of triode Q2 and one end of resistor R2. The other end of resistor R2 is respectively connected to the other end of resistor R9, one end of diode D9, one end of resistor R12, and the collector of triode Q4. The other end of diode D9 is grounded. The other end of resistor R4 is respectively connected to the collector of triode Q3, one end of diode D11, and the base of triode Q4. The emitter of triode Q4 is connected to the other end of diode D11. The base of triode Q3 is respectively connected to one end of diode D6 and one end of diode D8, and one end of capacitor C6. The other end of capacitor C6 is connected to the emitter of triode Q3 and grounded. The other end of diode D8 is connected to the other end of diode D7, and the other end of diode D6 is connected to the other end of diode D5.

[0023] Those of ordinary skill in the art can understand that the above are only preferred examples of the invention and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, for those skilled in the art, they can still modify the technical solutions described in the foregoing examples or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention. All technical features in this embodiment can be freely combined according to actual needs.

Claims

1. An antenna tuning system suitable for medium wave, characterized in that: It includes a standing wave detection circuit, a servo detection circuit, an antenna tuning monitoring unit, a DC motor, an impedance converter, a variable inductance coil, a fixed tap inductance coil, a relay group 1, a relay group 2, and a lightning arrester; During tuning, the control unit of the external transmitter sends the impedance parameters, motor tuning parameters, and fixed tap inductance parameters corresponding to the pre-stored working frequency to the antenna tuning monitoring unit through the network port, and the antenna tuning monitoring unit sends the impedance parameter, motor tuning parameter, and fixed tap inductance parameter instructions to the relay group 1, the servo detection circuit, and the relay group 2 respectively; When the RF output signal of the external transmitter enters the standing wave detection circuit, forward and reverse power coupling is performed, and the coupled signal is sent to the antenna tuning monitoring unit to be converted into a standing wave ratio, and a standing wave ratio value less than 1.3 is used as a basis for judging successful tuning; the RF output signal enters the servo detection circuit in turn, and the power signal entering the antenna tuning unit is detected through servo detection, and the corresponding voltage and current signals are collected; when the voltage and current are in the same direction, the load is resistive and the motor does not move; when the voltage and current are in different directions, the load is reactive, and the motor is controlled to rotate to change the inductance value of the variable inductor coil; the RF signal is then transmitted to the antenna through the impedance transformer, the variable inductor coil, the fixed tap inductor coil, and the lightning arrester in turn, so that the antenna is in a series resonance state.

2. The antenna tuning system for medium wave according to claim 1, characterized in that: The standing wave detection circuit comprises a forward RF coupling circuit, a reverse RF coupling circuit and a diode detection circuit. The output RF signal of the external transmitter passes through the coupling circuit and then through the diode detection circuit to convert the RF signal into a required voltage signal and output it to the antenna tuning monitoring unit. The forward power sampling and reverse power sampling signals obtained by the standing wave detection circuit are then used to calculate the standing wave ratio through the antenna tuning monitoring unit. The reference value set during the previous debugging is used to determine whether the standing wave ratio reaches an appropriate range. The tuning is successful only when the appropriate range is reached. Among them, the forward power sampling signal and reverse power sampling signal , the standing wave ratio SWR is calculated by the formula of the antenna tuning monitoring unit. The specific calculation is: ； When the transmitter and antenna are completely matched, the standing wave ratio SWR=1. If the transmitter is not matched, that is, there is a standing wave, then SWR>1. Generally, SWR<1.3 meets the transmission requirements.

3. The antenna tuning system for medium wave according to claim 1, characterized in that: The servo detection circuit includes a current mutual inductance coupler, a dual-phase detection circuit, and a motor control circuit; The output signal of the external transmitter first passes through the standing wave detection circuit and then passes through the servo detection circuit. The servo detection circuit samples the current and voltage and then performs phase comparison, and then converts it into a suitable voltage signal to drive the DC motor to rotate, change the inductance of the adjustable inductor coil, and put the antenna in a series resonance state; Among them, the dual-phase detection circuit compares the phases of the RF current and the RF voltage, and uses phase detection to determine whether the antenna loop is capacitive or inductive; the capacitive voltage sampling signal will output a positive voltage after detection; and the inductive voltage sampling signal will output a negative voltage after detection, successfully realizing phase detection, and according to the polarity of the phase detection output voltage, driving the DC motor to change the inductance of the adjustable inductor coil, so that the antenna is in a series resonance state; The dual-phase detection circuit outputs a DC voltage signal in the positive half cycle of the current sampling signal and also outputs a DC negative voltage signal in the negative half cycle of the current sampling signal; The motor control circuit includes two sets of relay switches, which switch the voltage signal from the dual-phase detection circuit and the motor control command of the antenna tuning monitoring unit. When the antenna tuning system is automatically tuned, the voltage signal of the dual-phase detection circuit is used to drive the DC motor. When the antenna tuning system software is manually tuned, the motor control command of the antenna tuning monitoring unit is used to drive the DC motor.

4. The antenna tuning system for medium wave according to claim 1, characterized in that: The antenna tuning monitoring unit includes a single-chip microcomputer and a network chip; Among them, the single-chip microcomputer has a storage unit for storing impedance parameters, motor tuning parameters, and fixed tap inductance parameters corresponding to the operating frequency. The stored data is used for each tuning call, and then these parameters are used to set the impedance converter, DC motor, and fixed tap inductance through the single-chip microcomputer respectively; The network chip is used for the antenna tuning monitoring unit to communicate with the external transmitter control unit over the network, receive impedance parameters, motor tuning parameters, fixed tap inductance parameters and other data sent by the external transmitter control unit, and feed back the tuning status parameters of the antenna tuning system to the external transmitter in real time; When the antenna tuning monitoring unit is tuned, the impedance parameters, motor tuning parameters, and fixed tap inductance parameters are first set to the corresponding relay group 1, servo detection circuit, and relay group 2 respectively. Then, the dual-phase detection circuit in the servo detection circuit converts the radio frequency signal of the current mutual inductance coupler into a voltage signal with polarity, drives the motor, changes the inductance of the adjustable inductance coil, performs automatic tuning, and finds the resonance point, so that the antenna is in a series resonance state. At the same time, the coupling signal of the standing wave detection circuit is converted to obtain a voltage signal, which is output to the antenna tuning monitoring unit. The voltage signal is converted into a numerical standing wave ratio by the single-chip microcomputer. According to the size of the standing wave ratio, it is judged whether the tuning is successful. If it is not successful, the software algorithm of the single-chip microcomputer is used to issue a motor control instruction to the servo detection circuit to make the motor rotate one circle to find the resonance point. After finding the resonance point, the motor is rotated to the angle of the resonance point. If the resonance point has not been found, the single-chip microcomputer sends an alarm signal to the external transmitter control unit through the network chip to request manual tuning.

5. The antenna tuning system for medium wave according to claim 1, characterized in that: The speed of the DC motor is 1RPM, and the angle required by the motor can be adjusted more accurately during tuning. The DC motor is controlled by the antenna tuning monitoring unit to control the servo detection circuit to drive the DC motor for automatic tuning and manual tuning.

6. The antenna tuning system for medium wave according to claim 1, characterized in that: The impedance converter is used to match the impedance of the transmitter to the impedance of different antennas, and the impedance is adjusted by changing different taps on the impedance converter; the variable inductor is used to change the inductance of the variable inductor by the angle of rotation of the motor; the fixed tap inductor is used to meet the transmission requirements of different operating frequencies.

7. The antenna tuning system for medium wave according to claim 1, characterized in that: The relay group 1 is used for sending instructions to the relay group to switch the taps of the impedance converter when the antenna monitoring unit receives the impedance parameters sent by the external transmitter control unit through the network port, so as to cope with the change of antenna impedance when the transmission frequency is changed.

8. The antenna tuning system for medium wave according to claim 1, characterized in that: The relay group 2 is used for when the antenna tuning monitoring unit receives the fixed tap inductance parameters sent by the external transmitter control unit through the network port, the antenna tuning monitoring unit sends a command to the relay group to switch the taps of the fixed tap inductance coil to cope with the change of antenna impedance when the transmission frequency is changed.

9. The antenna tuning system for medium wave according to claim 1, characterized in that: The standing wave detection circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a capacitor C2, an inductor L1, an inductor L2, a transmitter output signal terminal, a transmitter output signal output terminal, a forward coupling output terminal, and a reverse coupling output terminal, wherein the transmitter output signal terminal is respectively connected to the transmitter output signal output terminal and one end of the inductor L2, the other end of the inductor L2 is grounded, the forward coupling output terminal is respectively connected to one end of the resistor R1 and one end of the resistor R3, the other end of the resistor R3 is grounded, The other end of the resistor R1 is connected to one end of the resistor R4 and one end of the capacitor C1 respectively, the other end of the capacitor C1 is connected to one end of the resistor R5, one end of the resistor R6, one end of the capacitor C2 and one end of the inductor L1 respectively, the other end of the inductor L1 is grounded, the other end of the resistor R5 and the other end of the resistor R6 are grounded respectively, the other end of the capacitor C2 is connected to one end of the resistor R2 and one end of the resistor R7, the other end of the resistor R2 is connected to the reverse coupling output end and one end of the resistor R8 respectively, the other end of the resistor R7 and the other end of the resistor R8 are grounded respectively.

10. The antenna tuning system suitable for medium wave according to claim 1, characterized in that: The servo detection circuit includes capacitor C3, capacitor C4, capacitor C5, capacitor C6, resistor R9, resistor R10, resistor R11, resistor R12, diode D1, diode D2, diode D3, diode D4, diode D5, diode D6, diode D7, diode D8, diode D9, diode D10, diode D11, transistor Q1, transistor Q2, transistor Q3, and transistor Q4; wherein, one end of capacitor C3 is connected to one end of capacitor C4, the other end of capacitor C4 is respectively connected to one end of diode D1, one end of diode D3, one end of resistor R9, one end of diode D5, and one end of diode D7, the other end of diode D1 is connected to one end of diode D2, the other end of diode D3 is connected to one end of diode D4, the other end of diode D4 is respectively connected to the other end of diode D2, the base of transistor Q1, and one end of capacitor C5, the other end of capacitor C5 is connected to the emitter of transistor Q1 and connected to The collector of the transistor Q1 is respectively connected to one end of the resistor R11 and one end of the diode D10, the base of the transistor Q2, the emitter of the transistor Q2 is connected to the other end of the diode D10, the other end of the resistor R11 is respectively connected to the collector of the transistor Q2 and one end of the resistor R2, the other end of the resistor R2 is respectively connected to the other end of the resistor R9, one end of the diode D9, one end of the resistor R12, and the collector of the transistor Q4, the other end of the diode D9 is grounded, the other end of the resistor R4 is respectively connected to the collector of the transistor Q3, one end of the diode D11, and the base of the transistor Q4, the emitter of the transistor Q4 is connected to the other end of the diode D11, the base of the transistor Q3 is respectively connected to one end of the diode D6 and one end of the diode D8, and one end of the capacitor C6, the other end of the capacitor C6 is connected to the emitter of the transistor Q3 and grounded, the other end of the diode D8 is connected to the other end of the diode D7, and the other end of the diode D6 is connected to the other end of the diode D5.

Images