Automatic tuner for loop antennas used in shortwave communication

Abstract

This invention provides an automatic tuner for a loop antenna used in shortwave communication, belonging to the field of shortwave communication technology. This tuner aims to solve the problems of existing automatic tuners for loop antennas, such as difficulty in balancing versatility and high power performance, and poor high-voltage withstand capability. The tuner includes: a matching circuit, which includes couplers for shunting forward and reverse radio frequency signals; a tuning actuator, which includes an oil-immersed variable capacitor and a drive mechanism; and a main control circuit. Based on the signal shunted by the coupler, the main control circuit autonomously calculates the standing wave ratio (VSWR) and generates a control signal to control the matching circuit and tuning actuator independently of the radio transceiver, thus completing automatic tuning. This invention improves voltage withstand and power handling capability by using an oil-immersed variable capacitor, and achieves universal tuning through the autonomous control of the main control circuit, overcoming the shortcomings of existing technologies and offering the advantages of high power, high reliability, and strong versatility.

Description

Technical Field

[0001] This invention relates to the field of shortwave communication technology, and more specifically, to an automatic tuner for a loop antenna used in shortwave communication. Background Technology

[0002] Shortwave communication has the advantage of long transmission distance, and can usually achieve ultra-long-distance communication without the need for relay stations, playing an irreplaceable role in the field of communication. However, the wavelength of shortwave communication is usually between 10m and 100m, so it is often difficult to miniaturize its antenna size.

[0003] Loop antennas are characterized by their small size and have traditionally been used primarily for radio reception. In recent years, with the increasing demand for miniaturization of shortwave antennas, loop antennas have gradually been applied in shortwave communication reception and transmission.

[0004] Since antenna resonance is often closely related to the operating frequency, and the frequency of a radio transceiver frequently changes according to usage requirements, the main function of an antenna tuner is to achieve impedance matching and radio frequency signal resonance between the radio transceiver and the antenna at various frequencies. The adjustment process undertaken to achieve resonance is called tuning. When a radio transceiver transmits communication radio frequency signals, if the antenna is not in a resonant state, it will not only severely reduce the gain of the transmitted and received signals, but may also damage the radio transceiver. Therefore, tuning is crucial for wireless communication.

[0005] The resistance and inductive reactance (impedance of the inductor) of a loop antenna used in communication are generally fixed. Therefore, the principle of loop antenna tuning is to connect a variable capacitor (tuning capacitor) in series in the loop. By adjusting the capacitance value (corresponding to different capacitive impedances, called capacitive reactance), the overall impedance of the loop antenna (i.e., the combined effect of resistance, inductive reactance, and capacitive reactance) is optimized. At this point, the loop antenna has the lowest standing wave ratio (VSWR), is in a resonant state, and has the best transmission and reception performance for electromagnetic waves. The inductance and inductive reactance of loop antennas are significantly higher than other types of antennas. Ordinary antenna tuners cannot tune them; specialized loop antenna tuners are required. To address the high inductive reactance inherent in loop antennas, loop antenna tuners use a series variable capacitor and adjust its capacitance value to achieve antenna tuning. This is a significant difference in fundamental principle compared to tuners for non-loop antennas.

[0006] Currently, most loop antenna tuners used in shortwave communication are manual tuners, which are cumbersome to operate, highly skill-dependent, and pose significant safety risks. In recent years, a small number of automatic loop antenna tuners have emerged in the communications field. However, these tuners must be used with specific models of radio transceivers and loop antennas; they cannot be used with other models of radio transceivers or loop antennas, making universality difficult to achieve. In the automatic tuning process of these loop antennas, the adjustment of the variable capacitor is controlled by commands sent from the radio transceiver. This means that not only the tuner but also the radio transceiver must participate in the tuning control, acting as the command center. This tuning control, spanning the radio transceiver and tuner, involves extensive customization across multiple levels and dimensions, including hardware compatibility, transmission protocols, and command expression. Therefore, the tuning process must be completed collaboratively between specific models of radio transceivers, tuners, and loop antennas. This universality problem significantly increases the equipment configuration cost in the communications field and also affects deployment efficiency and the interchangeability of communication systems.

[0007] Furthermore, due to the current ( ) when using high power ( The inductive reactance of the loop antenna is relatively large, while the inductive reactance of the loop antenna is relatively large. The voltage division within the loop of the antenna is relatively high, therefore the voltage drop across the loop is relatively high. The voltage rating is relatively high. However, most current loop antenna tuners use air variable capacitors, and the withstand voltage of air variable capacitors suitable for tuning is generally no more than 10kV, which means that tuners often cannot be used under power conditions higher than 125W. Summary of the Invention

[0008] In view of the deficiencies in the prior art, the purpose of this invention is to provide an automatic tuner for a loop antenna for shortwave communication.

[0009] An automatic tuner for a loop antenna used in shortwave communication, provided by the present invention, is used to connect between a radio transceiver and a loop antenna, comprising: A matching circuit includes an array circuit and a coupler; the array circuit includes multiple reactive elements and switches; the coupler is used to split the forward radio frequency signal transmitted by the radio transceiver and the reverse radio frequency signal reflected back from the loop antenna. A tuning actuator, comprising an oil-immersed variable capacitor and a drive mechanism for driving the oil-immersed variable capacitor to perform adjustment; The main control circuit, which is connected to the matching circuit and the tuning actuator, is used to autonomously calculate the standing wave ratio and generate control signals based on the forward and reverse radio frequency signals shunted by the coupler, so as to control the matching circuit and the tuning actuator independently of the radio transceiver, thereby completing the automatic tuning process.

[0010] Preferably, the main control circuit includes a detection circuit, an analog-to-digital converter, and a measurement and control circuit; The detection circuit is used to convert the forward and reverse radio frequency signals of the shunt into voltage signals corresponding to their respective powers. The analog-to-digital converter is used to digitize the voltage signal; The measurement and control circuit is used to calculate the standing wave ratio based on the digitized signal and generate the control signal.

[0011] Preferably, the control signal generated by the main control circuit is used for: First, control the matching circuit to perform impedance matching; Then, the tuning actuator is controlled to adjust the oil-immersed variable capacitor for resonant tuning.

[0012] Preferably, the array circuit includes several fixed capacitors, several inductors, and a matrix switch.

[0013] Preferably, the driving mechanism is a stepper motor.

[0014] Preferably, the tuning actuator further includes an angle sensor for detecting the rotation angle of the stepper motor and feeding it back to the main control circuit.

[0015] Preferably, the driving mechanism is a servo motor.

[0016] Preferably, it also includes a handheld controller separate from the main control circuit, the handheld controller including a display screen for displaying the VSWR and a button for starting tuning.

[0017] Preferably, it also includes a housing, and a display screen and a start button integrated on the housing.

[0018] Preferably, during the automatic tuning process, the main control circuit generates the control signal with the goal of the standing wave ratio being less than a preset threshold.

[0019] Preferably, the main control circuit further includes a detection circuit, and the coupler is electrically connected to the analog-to-digital converter through the detection circuit.

[0020] Preferably, the variable capacitor includes: The housing assembly is configured as a sealable cavity, and the housing assembly includes at least one medium port for discharging and injecting a fluid dielectric. An electrode assembly, mounted within the cavity of the housing assembly, includes a first electrode assembly and a second electrode assembly that are insulated from each other, wherein at least one electrode assembly is a movable electrode assembly for adjusting the capacitance value by changing the effective overlap area between the first electrode assembly and the second electrode assembly; and A fluid dielectric, an insulating fluid, is filled into the cavity of the housing assembly to immerse the electrode assembly; the fluid dielectric is a liquid dielectric.

[0021] Preferably, the medium port includes a threaded opening and a removable sealing plug.

[0022] Preferably, the relative permittivity of the liquid dielectric is greater than 2.

[0023] Preferably, the liquid dielectric is mineral oil or castor oil.

[0024] Preferably, the first electrode assembly is a fixed electrode assembly, and the second electrode assembly is a rotatable electrode assembly. The rotatable electrode assembly is adapted to rotate around a rotation axis to change its overlap area with the fixed electrode assembly.

[0025] Preferably, it further includes a spring conductive sheet, which is used to maintain an electrical connection with the rotatable electrode assembly as it rotates.

[0026] Preferably, the housing assembly includes a lower housing, a cover, and a sealing ring disposed between the lower housing and the cover; A shaft sealing plug is provided at the point where the shaft protrudes from the housing assembly.

[0027] Preferably, the fixed electrode assembly includes a plurality of parallel rectangular metal electrode sheets; Multiple rectangular metal electrode plates are stacked at intervals and fixed inside the housing assembly by a fixed shaft; the fixed shaft is electrically connected to the rectangular metal electrode plates. One end of the fixed shaft is inserted into the fixed shaft blind hole on the lower housing; the other end of the fixed shaft passes through the lower housing and extends to the outside of the housing assembly, and a fixed shaft sealing plug is provided at the through position; The fixed shaft is provided with a fixing electrode assembly wiring nut, which is used for electrical connection with an external circuit.

[0028] Preferably, the rotatable electrode assembly comprises a plurality of parallel semi-circular metal electrode sheets; Multiple semi-circular metal electrode plates are stacked at intervals and rotatably disposed inside the housing assembly via the rotating shaft; the rotating shaft is electrically connected to the semi-circular metal electrode plates. One end of the rotating shaft is inserted into the blind hole on the lower housing; the other end of the rotating shaft passes through the lower housing and extends to the outside of the housing assembly for connecting to an external drive mechanism, and a rotating shaft sealing plug is provided at the through position; A spring conductive sheet is provided on the lower housing. The spring conductive sheet is fixed to the lower housing by a rotatable electrode assembly wiring screw. The spring conductive sheet is electrically connected to the rotatable electrode assembly wiring screw, which is used to electrically connect to an external wire. The spring conductive sheet includes a spring sheet portion and a planar contact portion. The planar contact portion contacts the shoulder portion of the rotating shaft through the spring sheet portion, allowing the rotating shaft to rotate. The planar contact portion is electrically connected to the shoulder portion.

[0029] Preferably, the plurality of rectangular metal electrode pieces allow the plurality of semi-circular metal electrode pieces to be rotated and inserted; The fixed axis and the rotating axis are parallel, and during the rotation of the plurality of semi-circular metal electrode plates, the overlapping area of ​​the projected rectangular metal electrode plate and the semi-circular metal electrode plate along the axial direction of the fixed axis can be changed.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves a combination of versatility and high power. By sampling signals through a built-in coupler and independently completing tuning control by the main control circuit, it can be used with different models of radio transceivers and loop antennas, exhibiting good versatility. At the same time, by using a high-voltage oil-immersed variable capacitor as the core tuning element, the breakdown voltage of oil is significantly higher than that of air, thus significantly improving the power handling capability of the tuner and solving the problem of insufficient power in existing loop antenna automatic tuners.

[0031] 2. This invention improves reliability and environmental adaptability. The oil-immersed variable capacitor uses oil as the insulating medium, which has a dielectric strength much higher than that of air. This effectively avoids the risk of arc discharge caused by air ionization in high-voltage or humid environments, thereby significantly enhancing the reliability of the equipment in harsh environments.

[0032] 3. This invention contributes to the miniaturization of equipment. Since the dielectric constant of oil is greater than that of air, the size of the oil-immersed variable capacitor can be made smaller while achieving the same capacitance adjustment range. This helps to reduce the overall physical size of the tuner. Attached Figure Description

[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1A schematic diagram of the system composition of an automatic tuner for a loop antenna for shortwave communication provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the cross-section of a variable capacitor; Figure 3 A schematic diagram of the overall appearance of a variable capacitor; Figure 4 This is a schematic diagram of the decomposed variable capacitor. Figure 5 This is a partially enlarged schematic diagram of the rotating shaft conductive mechanism; Figure 6 This is a schematic diagram illustrating the principle of capacitor value adjustment. Figure 7 This is a flowchart illustrating the method of using a capacitor.

[0034] The diagram shows: 1-Lower housing; 2-Cover; 3-Rotating shaft; 4-Fixed shaft; 5-Rotable electrode assembly; 6-Fixed electrode assembly; 7-Rotable electrode assembly wiring screw; 8-Fixed electrode assembly wiring nut; 9-Spring conductive plate; 10-Rotating shaft sealing plug; 11-Sealing ring; 12-Fluorescent dielectric; 13-Housing screw; 14-Mounting base; 15-Fixed shaft blind hole; 16-Fixed shaft sealing plug; 17-Rotating shaft blind hole; 18-Shoulder area; 19-Spring plate area; 20-Plane contact area; S101 - Select and inject fluid dielectric step; S102 - Connect capacitor to external circuit step; S103 - Connect drive mechanism to shaft step; S104 - Adjust shaft to change capacitance value step; S105 - Monitor circuit performance step; S106 - Reach target state step. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0036] Example 1 This embodiment provides a general-purpose high-power loop antenna automatic tuner that can complete the automatic tuning process independently of the radio transceiver, while also possessing excellent high power handling capability and environmental adaptability.

[0037] Please see Figure 1This figure is a schematic diagram of the system composition of a generalized high-power loop antenna automatic tuner provided in an embodiment of this application. As shown in the figure, the automatic tuner is a standalone device connected between an external radio transceiver and the loop antenna. The tuner mainly includes a main control circuit, a matching circuit, a tuning actuator, and a human-machine interface. In this embodiment, the human-machine interface is specifically a handheld controller separate from the tuner body.

[0038] Specifically, the matching circuit is the main path for radio frequency (RF) signal transmission, and it has two main interfaces: a transceiver interface for connecting to the radio transceiver, and an antenna feed interface for connecting to the main feed line of the loop antenna. The RF signal transmitted from the radio transceiver (in...) Figure 1 (Indicated by solid arrows) The signal enters the matching circuit via the transceiver interface, is processed, and then output to the loop antenna from the antenna feed interface. The matching circuit internally includes a coupler and a configurable array circuit. The coupler (e.g., a directional coupler) is connected in series in the main path of the RF signal. Its core function is to divert a small portion of the forward RF signal (i.e., the signal flowing from the transceiver to the antenna) and the reverse RF signal (i.e., the signal reflected back from the antenna) in a predetermined proportion, without significantly affecting the main signal transmission. These two diverted weak RF signals serve as measurement samples, and their flow direction is... Figure 1 The data, indicated by dashed arrows, is transmitted to the main control circuit for analysis.

[0039] An array circuit is a network used to achieve impedance transformation. In this embodiment, the array circuit consists of multiple fixed capacitors of different values, multiple inductors of different values, and a matrix switch for selectively connecting these reactive components to the circuit. These capacitors and inductors can be combined into different network topologies such as L-type, T-type, or π-type as needed. By controlling the on / off state of the matrix switch through the main control circuit, the equivalent reactance of the entire array circuit can be changed, thereby adjusting the input impedance of the antenna system.

[0040] The main control circuit, as the control core of the entire automatic tuner, is responsible for all measurement, calculation, decision-making, and control functions. The main control circuit is electrically connected to the matching circuit and the tuning actuator, and is used to receive measurement signals and send control commands (in...). Figure 1(Indicated by dashed arrows). In one specific embodiment of this application, the main control circuit includes a detection circuit, an analog-to-digital converter, and a core measurement and control circuit. The forward and reverse radio frequency signals shunted from the coupler first enter the detection circuit, which (e.g., may be composed of Schottky diodes, capacitors, and resistors) converts the high-frequency radio frequency signals into DC or low-frequency voltage signals, the amplitude of which is proportional to the power of the corresponding radio frequency signal. Subsequently, these two voltage signals, representing the forward and reverse power respectively, are sent to the analog-to-digital converter to be converted into digital quantities that the measurement and control circuit can process. The measurement and control circuit is typically implemented by a microcontroller or digital signal processor, which runs a preset tuning algorithm internally.

[0041] After receiving the digitized forward and reverse power values, the measurement and control circuit first applies the formula... Calculate the modulus of the reflection coefficient, where Forward power, This represents the reverse power. Accordingly, the current voltage standing wave ratio (VSWR) is calculated based on the reflection coefficient, using the following formula: The standing wave ratio (SWR) is a key indicator for measuring the degree of matching between the antenna system and the transceiver. Ideally, the SWR is 1:1. The core task of the measurement and control circuit 110 is to control the matching circuit 120 and the tuning actuator 130 to make the SWR value as close to 1:1 as possible.

[0042] The tuner actuator is the physical mechanism that enables antenna resonance adjustment. The core component of the tuner actuator is an oil-immersed variable capacitor. Compared to traditional air-immersed variable capacitors, oil-immersed variable capacitors use insulating oil as the dielectric. Because the dielectric strength of insulating oil is much higher than that of air, this capacitor has extremely high withstand voltage (e.g., it can withstand tens of thousands of volts), allowing the entire tuner to safely operate at high power transmission rates of hundreds or even thousands of watts.

[0043] As an example, in this embodiment, the tuner can operate stably at a transmit power of 500W. Meanwhile, the use of insulating oil avoids the risk of arcing caused by air ionization in humid or high-altitude, low-pressure environments, greatly improving the reliability of the equipment. The oil-immersed variable capacitor is connected in series with the external loop antenna's tuning circuit via its two ends' loop antenna series interfaces (typically, loop antennas have pre-installed ports for series tuning capacitors). The capacitance value of the oil-immersed variable capacitor is changed by rotating its adjusting lever.

[0044] To achieve automatic adjustment, the tuning actuator also includes a drive mechanism. In this embodiment, the drive mechanism is specifically a stepper motor. The motor shaft of the stepper motor is rigidly connected to the adjusting rod of the oil-immersed variable capacitor via a coupling. The measurement and control circuit in the main control circuit sends pulse and direction signals to the stepper motor through the motor drive circuit, thereby precisely controlling its rotation angle and speed, and thus precisely changing the capacitance value of the oil-immersed variable capacitor. To achieve more precise closed-loop control, the tuning actuator also includes an angle sensor, which is coaxially mounted with the motor shaft. This sensor can detect the absolute or relative rotation angle of the motor shaft in real time and send this angle information back to the measurement and control circuit of the main control circuit as a feedback signal. In this way, the measurement and control circuit can not only know the number of steps of the drive command it issues, but also confirm whether the adjusting rod of the capacitor has indeed reached the target position through the reading of the angle sensor, thereby avoiding the stepper motor's potential loss of steps when overloaded or obstructed, and ensuring the accuracy and reliability of capacitance value adjustment.

[0045] The handheld controller serves as the interface for user interaction with the tuner. Connected to the main control circuit via a cable, the controller features a button to initiate the automatic tuning process and a display screen (such as an LCD or digital tube) for showing information. The operator can issue tuning commands to the main control circuit by pressing the button and view real-time information sent by the main control circuit, including the current VSWR value, tuning process status (such as "Matching," "Tuning," "Tuning Complete"), and possible fault codes. This modular design allows the operator to conveniently operate and monitor the system from a location away from the antenna and tuner body.

[0046] The operation of the automatic tuner provided in this embodiment is described below. The entire process begins with the operator initiating tuning via a button on a handheld controller. Upon receiving the start command, the main control circuit enters a standby state. The operator operates the radio transceiver to transmit a continuous wave or frequency modulation signal at a low power (e.g., 5-10W, referred to as "tuning power"). This radio frequency signal flows through the matching circuit inside the tuner. The coupler samples the forward and reverse radio frequency signals and sends the sampled signals to the main control circuit. The detector circuit and analog-to-digital converter within the main control circuit process the sampled signals, and the measurement and control circuit ultimately calculates the initial standing wave ratio (VSWR). When the initial VSWR is too high, exceeding a preset coarse tuning threshold (e.g., greater than 3.0:1), the impedance matching stage is initiated first. At this stage, the measurement and control circuit sends control commands to the matrix switches in the array circuit of the matching circuit, based on the current VSWR and the internally stored tuning strategy (which may be a lookup table based on empirical data or a simple search algorithm), to turn specific switch combinations on or off, thereby connecting or removing different fixed capacitors and inductors from the RF path. This process aims to perform a coarse impedance transformation, adjusting the impedance presented by the antenna to a smaller range, significantly reducing the VSWR, and creating conditions for subsequent fine-tuning. The measurement and control circuit will try several different switch combinations and select the combination that results in the lowest VSWR as the result of this stage.

[0047] After impedance matching is completed (or skipped if the initial VSWR is already within an acceptable range), the process enters the resonant tuning stage. This is the core of the tuning process. The measurement and control circuit begins sending control signals to the motor drive circuit of the tuning actuator, driving the stepper motor to rotate, which in turn causes a continuous and smooth change in the capacitance value of the oil-immersed variable capacitor. During this process, the measurement and control circuit repeatedly executes the "sampling-calculating VSWR" cycle at an extremely high frequency (e.g., hundreds of times per second). The measurement and control circuit executes judgment logic. The measurement and control circuit continuously compares the newly calculated VSWR with the previously recorded minimum value. If the current VSWR is lower, the minimum value record is updated, and the stepper motor continues to rotate in the current direction. If the current VSWR begins to increase, it indicates that the resonant point (i.e., the lowest point of the VSWR) has been passed. At this time, the measurement and control circuit controls the stepper motor to rotate in the opposite direction a small distance, searching back and forth near the lowest point with finer step increments until a stable VSWR value that is as low as possible is found. In principle, this process is similar to an optimization algorithm, aiming to find the lowest point of the VSWR curve. The ultimate goal of the tuning process is to make the VSWR less than a preset threshold representing a good match, such as 1.5:1. Once the VSWR is below this threshold, and no lower point can be found within a certain range, the tuning process can be declared successful.

[0048] Once the control circuit determines that the minimum VSWR has been found, it stops tuning and displays the result. The control circuit stops sending signals to the motor drive circuit, the stepper motor stops rotating, and the capacitance of the oil-immersed variable capacitor is locked at the optimal resonant point. Simultaneously, the control circuit displays a "tuning complete" or similar success message to the user on the handheld controller's display screen, along with the final VSWR value. This completes the entire automatic tuning process, typically taking only a few seconds. The operator can then increase the power of the radio transceiver to its rated operating power (e.g., 500W) for normal communication.

[0049] The variable capacitor of this embodiment is particularly suitable for antenna tuning units in high-power high-frequency communication equipment, such as the tuning circuit of a high-power loop antenna. It aims to take advantage of the high-performance liquid dielectric to achieve excellent high-voltage resistance, power carrying capacity and compact structural design.

[0050] Figure 2 This is a schematic diagram of the cross-sectional structure of the capacitor in an embodiment of this application. Figure 3 This is a schematic diagram of its overall appearance, and Figure 4 The diagram shows its exploded structure. The capacitor mainly includes a housing assembly, an electrode assembly housed inside the housing assembly, and a fluid dielectric 12 filling the cavity of the housing assembly.

[0051] Specifically, the housing assembly forms a reliably sealable cavity, primarily composed of a lower housing 1 and a cover 2. The lower housing 1 and cover 2 may be made of high-strength insulating materials (e.g., engineering plastics or ceramics) to ensure overall insulation performance and mechanical strength. An annular sealing ring 11 is provided between the mating surfaces of the lower housing 1 and cover 2. When secured by a housing screw 13 (see...) Figure 4 When the cover 2 is secured to the lower housing 1 with fasteners such as [insert fastener name here], the sealing ring 11 is compressed, thereby forming a reliable static seal between the two to prevent leakage of the internal fluid dielectric 12. Furthermore, to facilitate the replacement of the fluid dielectric 12, at least one port is provided on the housing assembly (e.g., at a suitable location on the cover 2 or the lower housing 1). As an optional implementation, this port can be a threaded opening equipped with a removable sealing plug. When the medium needs to be replaced, the sealing plug can be unscrewed, the old medium can be drained through the port, and the new medium can be injected. After the operation is completed, the sealing plug can be tightened to ensure a seal. Near the bottom of the lower housing 1 is a mounting base 14 for mounting and securing the capacitor in this embodiment.

[0052] The electrode assembly is housed within an inner cavity formed by the housing assembly, and the electrode assembly includes a first electrode assembly and a second electrode assembly that are insulated from each other. In one embodiment of this application, as a preferred structure, the first electrode assembly is a fixed electrode assembly, and the second electrode assembly is a rotatable electrode assembly.

[0053] Combination Figure 2 and Figure 4 As shown, the fixed electrode assembly specifically includes a fixed electrode group 6. This fixed electrode group 6 is composed of multiple parallel rectangular metal electrode sheets stacked at certain intervals and fixed inside the housing assembly, for example, fixed to the base of the lower housing 1 by a fixed shaft 4. One end of the fixed shaft 4 is inserted into a fixed shaft blind hole 15 on the lower housing 1, and the other end of the fixed shaft 4 passes through the lower housing 1, with a fixed shaft sealing plug 16 provided at the through-hole position. The fixed electrode assembly is connected to an external circuit via a lead-out terminal, such as... Figure 3 The fixed shaft 4 and the fixed electrode assembly wiring nut 8 are shown. The fixed shaft 4 is electrically connected to the fixed electrode assembly 6 and passes through the wall of the housing assembly (e.g., the bottom of the lower housing 1) while ensuring the sealing of the passage position. The fixed electrode assembly wiring nut 8 is mounted on the fixed shaft 4.

[0054] The rotatable electrode assembly includes a rotatable electrode group 5 and a rotating shaft 3 for driving its rotation. The rotatable electrode group 5 is also composed of multiple parallel semi-circular metal electrode plates stacked at certain intervals, their size and spacing matching the fixed electrode group 6, allowing the electrode plates of the rotatable electrode group 5 to be smoothly inserted into the gaps between the electrode plates of the fixed electrode group 6. The rotatable electrode group 5 is securely mounted on the rotating shaft 3 and rotates with it. One end of the rotating shaft 3 is inserted into a blind hole 17 on the lower housing 1, and the other end of the rotating shaft 3 extends through the lower housing 1 to the outside of the housing assembly for connection to an external drive mechanism, such as a motor or a manual knob. A rotating shaft sealing plug 10, such as an O-ring or a dedicated rotary seal, is provided at the location where the rotating shaft 3 passes through the lower housing 1 to ensure a dynamic seal is maintained at this point during rotation of the rotating shaft 3, preventing leakage of the fluid dielectric 12 from the shaft gap.

[0055] To connect the rotatable electrode assembly 5 to an external circuit, this embodiment employs a reliable rotating conductive structure. See also... Figure 3 and Figure 5 ,in Figure 5This is a partially enlarged schematic diagram of the rotating shaft conductive mechanism. On the exterior of the housing assembly, a rotatable electrode assembly wiring screw 7 is provided for connecting external wires. This wiring screw 7 also serves to secure the spring conductive piece 9. The spring conductive piece 9 is a metal component with good elasticity and conductivity. One of its spring portions 19, through its own elastic force, presses a planar contact portion 20 tightly against the shoulder portion 18 of the rotating shaft 3. The shoulder portion 18 of the rotating shaft 3 is a smooth, surface-treated conductive annular area on the rotating shaft 3. In this way, regardless of how the rotating shaft 3 rotates, the contact portion of the spring conductive piece 9 always maintains stable sliding electrical contact with it, thereby establishing a complete, low-resistance electrical path from the wiring screw 7 to the spring conductive piece 9, then to the rotating shaft 3, and finally to the rotatable electrode assembly 5.

[0056] In this embodiment, to achieve extremely high withstand voltage and a compact size, a high-performance liquid dielectric, namely castor oil, was selected as the fluid dielectric 12. Castor oil is an insulating, non-polar liquid with a relative permittivity of approximately 4.7, much higher than that of air (approximately 1.0) and vacuum (1.0). Simultaneously, its breakdown voltage is as high as approximately 7.0 kV / cm, while the breakdown voltage of air is only approximately 0.3 kV / cm. The castor oil is filled into the entire cavity of the housing assembly through a pre-designed port, completely immersing the fixed electrode assembly 6 and the rotatable electrode assembly 5 within it.

[0057] The working principle of this capacitor is based on the capacitance formula of a parallel plate capacitor. The capacitance is given, where C is the capacitance value, ε is the dielectric constant of the medium between the electrodes, A is the effective overlap area of ​​the electrode plates, and d is the distance between the electrode plates. In the structure of this application, d is a fixed value, while ε is determined by the selected fluid dielectric 12. The capacitance value is adjusted by changing the effective overlap area A.

[0058] Figure 6 The process of adjusting the capacitance value is illustrated schematically. When the external drive mechanism drives the rotating shaft 3 to rotate, the rotatable electrode assembly 5 mounted on it also rotates accordingly. Figure 6 (a) shows the state where the rotatable electrode assembly 5 and the fixed electrode assembly 6 are completely offset, at which point the effective overlap area A between them is close to zero, and the capacitance value reaches its minimum. As the rotating shaft 3 rotates, the electrode pieces of the rotatable electrode assembly 5 gradually insert into the gaps of the fixed electrode assembly 6, as shown... Figure 6 (b) and Figure 6 As shown in (c), the effective overlapping area A gradually increases, and the capacitance value also increases linearly. When rotated to... Figure 6At the position shown in (d), the overlap area A between the rotatable electrode group 5 and the fixed electrode group 6 reaches its maximum, and the capacitance value reaches its maximum value accordingly. By controlling the rotation angle of the rotating shaft 3, the capacitance value can be smoothly and continuously adjusted between the minimum and maximum values.

[0059] The following is combined Figure 7 The flowchart shown illustrates the method of using the capacitor in the high-power loop antenna tuning of this embodiment. First, in step S101, castor oil is selected as the fluid dielectric 12 according to the application requirements of high power and high voltage resistance, and it is injected into the inner cavity of the capacitor and sealed. Next, in step S102, the capacitor is connected in series to the radiation loop of the loop antenna. Specifically, the antenna loop is disconnected, and both ends are connected to the fixed electrode assembly wiring nut 8 and the rotatable electrode assembly wiring screw 7 of the capacitor, respectively. Next, in step S103, a precision drive mechanism such as a stepper motor or servo motor is connected to the exposed rotating shaft 3 of the capacitor.

[0060] After installation, tuning begins. The transmitter transmits a signal at low power, while the drive mechanism executes step S104, slowly rotating shaft 3 to change the capacitance value. Simultaneously, step S105 is executed in real-time using an antenna analyzer or VSWR meter to monitor the antenna's VSWR. If the VSWR does not reach the ideal value (e.g., greater than 1.5), the process returns to step S104 to continue adjusting the capacitance value. When the VSWR reaches its minimum value (ideally close to 1.1), it indicates that the antenna has reached resonance at that frequency. At this point, the process proceeds to step S106, the tuning process is complete, and the drive mechanism stops rotating.

[0061] Understandably, because this embodiment uses castor oil with extremely high breakdown voltage, the capacitor's ability to withstand the high voltage generated by the antenna loop during high-power transmission is approximately 23 times that of an air-based variable capacitor, and it can withstand hundreds of kilovolts of radio frequency voltage without breakdown. Experimental data shows that the antenna system using the capacitor of this embodiment can stably increase its operating power from the 125 watts limited by conventional air-based variable capacitors to over 500 watts. Furthermore, as a liquid, castor oil has far superior thermal conductivity than air, effectively conducting the heat generated by the electrode plates under high current to the housing assembly and dissipating it, ensuring the stability of the capacitor during long-term high-power operation. Simultaneously, due to the high relative permittivity of castor oil (4.7), while achieving the same capacitance adjustment range as conventional large air-based variable capacitors, the electrode plate area and overall volume of the capacitor in this embodiment can be significantly reduced, to approximately 1 / 4.7 of the latter, thus achieving significant miniaturization and weight reduction.

[0062] Example 2 Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0063] This embodiment addresses the current industry problem of a lack of universal tuners for loop antennas, providing a universal loop antenna tuner for shortwave communication. For readability, this embodiment does not describe the common-sense, basic components of the tuner in detail, such as the power supply and housing; however, this does not mean that the tuner lacks these components. Furthermore, as is common knowledge, antennas in wireless communication are responsible for receiving and transmitting wireless signals, and the tuning process is mainly accomplished using the radio frequency signals during transmission. According to the reciprocity theorem, once the antenna achieves resonance, it is in its optimal performance state for both transmission and reception; therefore, to avoid redundancy, the reception process is not described in detail in this embodiment.

[0064] This embodiment provides a general-purpose automatic tuner for a loop antenna used in shortwave communication, mainly composed of a main control circuit, a matching circuit, a tuning actuator, and a handheld controller. Figure 1 The diagram shown is a schematic of the internal components and signal flow of this tuner. Figure 1 In the description of the line type in the lower right corner, "communication radio frequency signal" mainly represents the shortwave communication signal received and transmitted by the radio transceiver; "measurement and control signal" mainly represents the signal used for measurement or the signal used for control (including the control of electronic and electrical signals, as well as the control of power and motion); the arrow indicates the direction of signal flow.

[0065] This tuner connects the radio transceiver to the loop antenna. The main control circuit within this tuner is its control center, responsible for measuring, calculating, and analyzing the communication radio frequency signals. It then generates control signals to control the matching circuit and tuning actuator to achieve automatic tuning of the loop antenna. The main function of the matching circuit is to split the radio frequency signals transmitted by the radio transceiver and those reflected from the loop antenna back to the tuner to the analog-to-digital converter in the main control circuit, and to achieve automatic impedance matching (typically 50Ω) between the radio transceiver and the loop antenna.

[0066] The matching circuit is connected between the radio transceiver and the loop antenna. In communication transmission, the matching circuit is the main path for the transmission of radio frequency signals between the radio transceiver and the loop antenna in this tuner. The tuning actuator is mainly responsible for achieving automatic resonance of the loop antenna by adjusting and controlling the oil-immersed variable capacitor. The handheld controller is mainly responsible for operation and information display.

[0067] The automatic loop antenna tuner provided in this embodiment mainly functions to automatically match the impedance between the radio transceiver and the loop antenna, and to automatically tune the loop antenna. This tuner primarily uses a coupler in its matching circuit to split the radio frequency (RF) signal transmitted by the radio transceiver and the RF signal reflected from the antenna to the main control circuit inside the tuner. The main control circuit measures, calculates, and analyzes these two RF signals to obtain the standing wave ratio (VSWR) value. Based on this value and the capacitance, inductance, and frequency characteristics of the loop antenna stored in the main control circuit, a control strategy is generated to control the matching circuit for automatic matching. Then, the rotation of the oil-immersed variable capacitor in the tuning actuator is controlled to adjust the capacitance value, thereby achieving automatic tuning of various loop antennas.

[0068] The main control circuit consists primarily of a measurement and control circuit and an analog-to-digital converter (ADC). The ADC is connected to the matching circuit and the measurement and control circuit, responsible for measuring the two types of radio frequency (RF) signals shunted from the matching circuit and transmitting the measured values ​​to the measurement and control circuit. These two RF signals include the RF signal transmitted from the radio transceiver and the RF signal reflected back from the antenna. The measurement and control circuit is connected to the matching circuit and the tuning actuator. The measurement and control circuit calculates and analyzes the measured values ​​of these two RF signals to obtain the VSWR (Standing Wave Ratio). Based on this value and the capacitance, inductance, and frequency characteristics of the loop antenna stored in the software within the measurement and control circuit, it generates a control strategy and transmits the matching control signal from the control strategy to the matching circuit to achieve automatic impedance matching between the radio transceiver and the loop antenna. Then, it transmits the tuning control command from the control strategy to the tuning actuator to achieve automatic tuning control of the loop antenna.

[0069] The measurement and control circuit is connected to the handheld controller. It is used to execute the control signals sent by the handheld controller, and also to send the VSWR value and tuning status information calculated by the measurement and control circuit to the handheld controller for display. The main function of the matching circuit is to shunt the radio frequency (RF) signals transmitted by the radio transceiver and the RF signals reflected back to the tuner from the loop antenna into the tuner itself, and to achieve automatic impedance matching between the radio transceiver and the loop antenna. In communication transmission and reception, the matching circuit is the main path for the transmission of communication RF signals between the radio transceiver and the loop antenna in this tuner.

[0070] The matching circuit mainly consists of a coupler, an array circuit, a transceiver interface, and an antenna feed interface. The coupler is connected between the transceiver interface and the array circuit, and is responsible for diverting a portion of the communication radio frequency signal (including the radio frequency signal transmitted by the radio transceiver and the radio frequency signal reflected back from the loop antenna) flowing through the coupler to the analog-to-digital converter of the main control circuit for measurement.

[0071] The transceiver interface connects to the coupler and an external radio transceiver, respectively. The antenna feed interface connects to the array circuit and the feed interface in the external loop antenna, respectively. The coupler has two main channel ports connected to the transceiver interface and the array circuit, respectively, and one coupled shunt signal output terminal connected to the analog-to-digital converter in the main control circuit. The coupler is responsible for shunting a small portion of the RF signal transmitted by the radio transceiver and the RF signal reflected back from the loop antenna to the analog-to-digital converter in the main control circuit for measurement.

[0072] The array circuit is connected to the coupler and antenna feed interface, and mainly consists of several fixed capacitors, several inductors, and a matrix switch. Its matching network adopts the Γ-matching principle. The fixed capacitors and inductors are arranged in an array, and the pins of each fixed capacitor and inductor are connected to different channel pins in the matrix switch. The matrix switch contains a large number of channel pins and has an internal channel switching network, which can control the on / off state between each channel pin according to control commands.

[0073] The control interface of the matrix switch is connected to the measurement and control circuit in the main control circuit. One of the channel pins of the matrix switch is connected to the antenna feed interface. The matching circuit receives the matching control signal (i.e., the control signal for the matrix switch channel switching network) from the measurement and control circuit to realize real-time control of the switch channel switching network status, thereby realizing the control of the on / off state between each channel pin, and further realizing the selection control of related fixed capacitors and inductors.

[0074] The different on / off, series, and parallel states of each fixed capacitor and inductor arranged in an array correspond to a certain capacitance value and a certain inductance value of the entire array. Since the pins of each fixed capacitor and inductor are connected to different channel pins of the matrix switch, the on / off states of each channel pin in the matrix switch correspond to the connection relationship between each fixed capacitor and inductor. Therefore, the changes in the above connection relationship represent the changes in the on / off, series, and parallel relationships between each fixed capacitor and inductor, thus determining the overall capacitance and inductance value of the entire array.

[0075] The array circuit changes its own capacitance and inductance values ​​in this way, with different capacitance and inductance values ​​corresponding to specific capacitive and inductive reactance values. This is based on the connection relationships described above. Figure 1As can be seen, the array circuit connects itself in series with the external radio transceiver and loop antenna through an internal matrix switch. As is common knowledge in this industry, impedance is determined by resistance, capacitive reactance, and inductive reactance. Therefore, changes in the capacitive and inductive reactance of the array circuit directly affect the impedance between the radio transceiver and the loop antenna. This tuner uses the above mechanism to control and adjust the capacitive and inductive reactance of the array circuit, thereby achieving automatic impedance adjustment between the radio transceiver and the loop antenna. When this impedance is adjusted to match the specified impedance value of the radio transceiver (typically 50Ω), automatic matching is achieved.

[0076] The tuning actuator mainly consists of a loop antenna series interface, a stepper motor, an angle sensor, a motor drive circuit, and an oil-immersed variable capacitor. The tuning actuator is primarily responsible for automatically tuning the loop antenna by adjusting the internal oil-immersed variable capacitor according to the control commands from the measurement and control circuit.

[0077] At the electrical connection level, the loop antenna series interface is connected to the oil-immersed variable capacitor and the tuning capacitor interface in the external loop antenna. The variable capacitor is connected in sequence to the loop antenna series interface and the tuning capacitor interface of the external loop antenna, thereby connecting the oil-immersed variable capacitor in series in the loop body of the loop antenna.

[0078] The angle sensor's shaft is mechanically connected and linked to the stepper motor's shaft, measuring the stepper motor's rotation angle. The angle sensor is electrically connected to the measurement and control circuit, transmitting the measured angle value in real-time as feedback for motor rotation control, enabling precise control of the motor's rotation angle. The motor drive circuit is connected to the measurement and control circuit and receives motor control commands from it. The motor drive circuit is also electrically connected to the stepper motor, converting the motor control commands into motor drive signals to drive the stepper motor's rotation. The adjusting rod of the oil-immersed variable capacitor is mechanically rigidly connected to the stepper motor's shaft. The measurement and control circuit in the main control circuit autonomously controls the stepper motor's rotation, thereby driving the adjustment rod of the variable capacitor (rigidly connected to the stepper motor's shaft) to adjust its capacitance value, thus achieving automated tuning of the loop antenna. The stepper motor, angle sensor, and motor drive circuit work together to control the rotation of the oil-immersed variable capacitor's adjusting rod according to commands from the measurement and control circuit in the main control circuit, providing real-time feedback of the rotation angle to the measurement and control circuit.

[0079] Furthermore, the loop of the loop antenna has a high inductive reactance, and whether the loop antenna resonates depends on the capacitance value of the oil-immersed variable capacitor connected in series in the loop (corresponding to a certain capacitive reactance value). This tuner automatically changes the capacitance value by rotating the adjustment rod of the oil-immersed variable capacitor, thereby achieving automatic tuning of the loop antenna.

[0080] Furthermore, traditional air-immersed variable capacitors are prone to air ionization, leading to arc discharge and equipment burnout. This damage is exacerbated in humid weather due to higher humidity. The maximum power of air-immersed variable capacitors is typically no higher than 125W, while this solution, using oil-immersed variable capacitors, can achieve a maximum power of over 500W. In addition, the dielectric constant of oil-based dielectrics is significantly greater than that of air, resulting in significantly smaller electrode dimensions for oil-immersed variable capacitors compared to air capacitors. Therefore, the unique use of oil-immersed variable capacitors in this embodiment offers the advantages of significantly improving the tuner's high-voltage withstand capability, transmission power, and significantly reducing the overall size of the tuner.

[0081] The handheld controller mainly consists of buttons, a display and control circuit, and a display screen. The display and control circuit is connected to the buttons and the display screen, and also to the measurement and control circuit in the main control circuit. It is used to read the button status and forward it to the measurement and control circuit, and to convert the digital information transmitted from the measurement and control circuit into electrical signals for display on the screen. The on / off buttons are used to turn the tuner's automatic tuning function on or off; the display screen shows the information transmitted from the display and control circuit, including the VSWR value of the loop antenna and a status indicator indicating whether tuning is complete.

[0082] This embodiment provides a general-purpose automatic tuner for a loop antenna used in shortwave communication, mainly composed of a main control circuit, a matching circuit, a tuning actuator, and a handheld controller. The main control circuit is the control center of this tuner, responsible for measuring, calculating, and analyzing the radio frequency signal, and generating control signals to control the matching circuit and the tuning actuator to achieve automatic tuning of the loop antenna. The main control circuit mainly consists of a measurement and control circuit and an analog-to-digital converter. The matching circuit is the main path for transmitting radio frequency signals between the radio transceiver and the loop antenna in this tuner. Its main function is to split the radio frequency signals sent by the radio transceiver and the radio frequency signals reflected back to the tuner from the loop antenna to the analog-to-digital converter in the main control circuit of this tuner, and to realize the automatic impedance matching between the radio transceiver and the loop antenna. It mainly consists of a coupler, an array circuit, a transceiver interface, and an antenna feed interface. The tuning actuator is mainly responsible for realizing the automatic resonance of the loop antenna by adjusting and controlling the internal oil-immersed variable capacitor. It mainly consists of a stepper motor, an angle sensor, a motor drive circuit, an oil-immersed variable capacitor, and a loop antenna series interface. The handheld controller is mainly used for operation and information display, and mainly consists of buttons, a display control circuit, and a display screen.

[0083] The implementation mechanism of the antenna tuner provided in this embodiment is mainly to use the above-mentioned coupler to split the radio frequency signal sent by the radio transceiver and the radio frequency signal reflected from the loop antenna into the tuner. The main control circuit measures, calculates and analyzes the above-mentioned radio frequency signal and controls the matching circuit to perform automatic matching. Then, it controls the rotation of the oil-immersed variable capacitor in the tuning actuator to adjust the capacitance value to achieve resonance of the loop antenna, thereby realizing automatic tuning of various loop antennas.

[0084] The solution provided in this embodiment enables automated impedance matching and automated resonant tuning between various types of loop antennas and radio transceivers during shortwave communication reception and transmission. This primarily addresses the current industry problem of a lack of universal automatic tuners for loop antennas. Furthermore, the use of an oil-immersed variable capacitor in the tuning capacitor offers the significant advantage of a higher voltage tolerance and higher power limit compared to current loop antenna tuners, thus significantly improving shortwave communication quality.

[0085] Example 3 Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0086] Before use, prepare by connecting the tuner to the radio transceiver and the loop antenna, and then powering the equipment. The handheld controller of the tuner is placed at the operator's work position, while the remaining components are integrated into a housing forming the main body of the tuner. This main body is mounted on the loop antenna's mounting position. The two positions are connected by a cable.

[0087] Normal operating procedures mainly include: Step 1: The operator turns on the tuning button switch (i.e., the button) on the handheld controller to activate the automatic tuning function and turn on the radio transceiver; Step 2: Set the radio transceiver to the communication frequency and start transmitting the signal. Simultaneously, the operator observes the standing wave ratio (SWR) and tuning status display on the handheld controller's screen. The tuning status display mainly includes "Tuning in progress" and "Tuning complete." As tuning progresses, when the tuning status changes from "Tuning in progress" to "Tuning complete," it indicates that the tuner has completed automatic impedance matching and resonance adjustment between the radio transceiver and the loop antenna, thus completing the tuning process. Step 3: At this point, the radio transceiver can receive and transmit normally.

[0088] If the communication frequency required for the operation of the radio transceiver changes, repeat steps 2 and 3 above.

[0089] If the tuning status on the handheld controller's display does not show "Tuning Complete" within 10 seconds, the operator should immediately stop the radio transceiver from transmitting and conduct an inspection, including checking the condition of the loop antenna and ensuring all connections are secure. This is a protective function to address unexpected situations or misoperation, as prolonged untuned operation of any type of antenna can cause serious damage to the radio transceiver.

[0090] The following section, in conjunction with the "Normal Operation Procedures," explains the internal workflow and principles of this tuner during implementation.

[0091] When the operator sets the radio transceiver to communication frequency f and begins transmitting a signal, the coupler in the matching circuit continuously shuns the radio frequency signal transmitted from the radio transceiver interface into this tuner to the analog-to-digital converter in the main control circuit. At the same time, the coupler also continuously shuns the radio frequency signal reflected back from the loop antenna (the value of the signal reflected back from the antenna is zero only in the ideal tuning state, which is the ideal resonance state) into the main control circuit.

[0092] Furthermore, the analog-to-digital converter continuously measures the two types of radio frequency signals shunted from the coupler in the matching circuit and transmits the measured values ​​to the measurement and control circuit.

[0093] Furthermore, the measurement and control circuit is responsible for calculating and analyzing the measured values ​​of the two radio frequency signals to obtain the standing wave ratio (SWR) value, and displaying the value and "tuning in progress" on the display screen of the handheld controller. Based on this value and the capacitance, inductance, and frequency characteristics of the loop antenna stored in the software contained in the measurement and control circuit, a control strategy is generated, and the matching control signal is transmitted to the matching circuit to realize the automatic impedance matching between the radio transceiver and the loop antenna.

[0094] Specifically, after receiving the matching control signal, the matrix switch in the matching circuit performs channel switching and deployment on the internal channel switching network, determines the on / off, series, and parallel states of each fixed capacitor and each inductor in the entire array circuit, thereby controlling the adjustment of the capacitive reactance and inductive reactance of the entire matching circuit, thus realizing automatic impedance matching between the radio transceiver and the loop antenna.

[0095] Furthermore, after completing automatic impedance matching, the measurement and control circuit transmits the tuning control command to the tuning actuator. The motor drive circuit in the tuning actuator drives the stepper motor to rotate to the corresponding angle according to this command. Simultaneously, the motor's rotation drives the adjustment rod of the oil-immersed variable capacitor to rotate, thereby adjusting the capacitance value. The angle sensor feeds back the motor's current rotation angle to the measurement and control circuit as input for the motor's closed-loop control, achieving precise control of the oil-immersed variable capacitor's adjustment rod angle.

[0096] For each communication frequency f, the capacitance value of the corresponding oil-immersed variable capacitor is unique in the resonant state of each loop antenna entity, and corresponds to a minimum standing wave ratio (VSWR). During the adjustment of the capacitance value of the oil-immersed variable capacitor, the measurement and control circuit continuously calculates the VSWR value. When the lowest VSWR value is measured, it is determined that the antenna resonance has been achieved, that is, the tuning is completed. At this time, the measurement and control circuit immediately controls the motor to stop rotating and sends the "tuning completed" status to the handheld controller. At this time, the tuning status on the handheld controller's display screen changes from "tuning in progress" to "tuning completed".

[0097] At this point, the tuner has completed its automatic tuning task. At frequency f, the radio transceiver and the loop antenna are in optimal coordination, the radio transceiver is transmitting and receiving at its most energy-efficient state, the reflection loss of both the radio transceiver and the loop antenna is at its lowest, and the loop antenna is also in optimal transmit and receive gain state. The operator can then use the radio transceiver for normal transmission and reception operations.

[0098] In light of the specific implementation scenario, it is necessary to further explain that: The advantages of using oil-immersed variable capacitors in this solution are a significant improvement in the tuner's transmit power and tolerance to humid environments. Traditional air-immersed variable capacitors are prone to arcing and damage in humid conditions due to high humidity, typically limiting their maximum power to no more than 125W. This solution, however, can achieve 500W. Even in environments with poor ionospheric conditions leading to weak shortwave reflection, the communication performance under these power conditions is significantly better than current tuners, resulting in a substantial improvement in shortwave communication quality. Furthermore, this tuner can operate in any humidity environment during its implementation. The implementation of this scheme has no requirements regarding the type of loop antenna or radio transceiver. This is a unique benefit resulting from the use of real-time standing wave measurements to detect the antenna's resonance state.

[0099] This embodiment provides a general-purpose automatic tuner for shortwave communication loop antennas. Uniquely, it employs a coupler to shunt the communication RF signal (regardless of the radio transceiver model or loop antenna model) into the tuner. The tuner measures, calculates, and analyzes this signal, calculates the VSWR value, and automatically controls the internal mechanism to achieve automated impedance matching and automatic tuning between the radio transceiver and the loop antenna. The unique advantage of this design is that antenna tuning is based solely on the actual communication signal. The control and execution of automatic tuning are entirely performed independently by the tuner, without needing to receive control commands from the radio transceiver. Therefore, tuning of different loop antenna models can be independent of specific radio transceiver models.

[0100] Therefore, it can achieve automated impedance matching and automated resonant tuning between the output signals of various types of loop antennas and various types of radio transceivers during shortwave communication reception and transmission, mainly to solve the current industry problem of the lack of universal automatic tuners for loop antennas. Furthermore, because it uses an oil-immersed variable capacitor, and the high voltage withstand capability of oil-based dielectrics is more than twenty times that of air-based variable capacitors, this tuner's high-power operation capability is no less than 500W, significantly higher than current loop antenna tuners.

[0101] This invention provides an automatic tuner for a loop antenna used in shortwave communication, belonging to the field of shortwave communication technology. This tuner aims to solve the problems of existing automatic tuners for loop antennas, such as difficulty in balancing versatility and high power performance, and poor high-voltage withstand capability. The tuner includes: a matching circuit, which includes couplers for shunting forward and reverse radio frequency signals; a tuning actuator, which includes an oil-immersed variable capacitor and a drive mechanism; and a main control circuit. Based on the signal shunted by the coupler, the main control circuit autonomously calculates the standing wave ratio (VSWR) and generates a control signal to control the matching circuit and tuning actuator independently of the radio transceiver, completing automatic tuning. This invention improves voltage withstand and power handling capability by using an oil-immersed variable capacitor, and achieves universal tuning through the autonomous control of the main control circuit, overcoming the shortcomings of existing technologies and offering the advantages of high power, high reliability, and strong versatility.

[0102] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. An automatic tuner for a loop antenna used in shortwave communication, characterized in that, For connection between a radio transceiver and a loop antenna, including: A matching circuit includes an array circuit and a coupler; the array circuit includes multiple reactive elements and switches; the coupler is used to split the forward radio frequency signal transmitted by the radio transceiver and the reverse radio frequency signal reflected back from the loop antenna. A tuning actuator, comprising an oil-immersed variable capacitor and a drive mechanism for driving the oil-immersed variable capacitor to perform adjustment; The main control circuit, which is connected to the matching circuit and the tuning actuator, is used to autonomously calculate the standing wave ratio and generate control signals based on the forward and reverse radio frequency signals shunted by the coupler, so as to control the matching circuit and the tuning actuator independently of the radio transceiver, thereby completing the automatic tuning process.

2. The automatic tuner for a loop antenna for shortwave communication according to claim 1, characterized in that, The main control circuit includes a detector circuit, an analog-to-digital converter, and a measurement and control circuit. The detection circuit is used to convert the forward and reverse radio frequency signals of the shunt into voltage signals corresponding to their respective powers. The analog-to-digital converter is used to digitize the voltage signal; The measurement and control circuit is used to calculate the standing wave ratio based on the digitized signal and generate the control signal.

3. The automatic tuner for a loop antenna for shortwave communication according to claim 1, characterized in that, The control signals generated by the main control circuit are used for: First, control the matching circuit to perform impedance matching; Then, the tuning actuator is controlled to adjust the oil-immersed variable capacitor for resonant tuning.

4. The automatic tuner for a loop antenna for shortwave communication according to claim 1, characterized in that, The array circuit includes several fixed capacitors, several inductors, and a matrix switch.

5. The automatic tuner for a loop antenna for shortwave communication according to claim 1, characterized in that, The driving mechanism is a stepper motor.

6. The automatic tuner for a loop antenna for shortwave communication according to claim 5, characterized in that, The tuning actuator also includes an angle sensor for detecting the rotation angle of the stepper motor and feeding it back to the main control circuit.

7. The automatic tuner for a loop antenna for shortwave communication according to claim 1, characterized in that, The drive mechanism is a servo motor.

8. The automatic tuner for a loop antenna for shortwave communication according to claim 1, characterized in that, It also includes a handheld controller separate from the main control circuit, the handheld controller including a display screen for displaying the VSWR and a button for starting tuning.

9. The automatic tuner for a loop antenna for shortwave communication according to claim 1, characterized in that, It also includes a housing, as well as a display screen and a start button integrated into the housing.

10. The automatic tuner for a loop antenna for shortwave communication according to any one of claims 1 to 3, characterized in that, During the automatic tuning process, the main control circuit generates the control signal with the goal of the standing wave ratio being less than a preset threshold.

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