Electrically tunable high power mast antenna system and method for an electromagnetic anechoic chamber

Abstract

This invention discloses an electrically tuned high-power telescopic antenna system and method for use in an electromagnetic reverberation chamber. The system includes a base unit with a telescopic antenna rod slidably connected to it. The telescopic antenna rod's electrical length can be adjusted by changing its extension length to accommodate resonance requirements at different test frequencies. An electrically driven mechanism is installed within the base unit, with its power output connected to the telescopic antenna rod. The telescopic antenna rod is electrically connected to an RF feed unit for feeding external RF power into the telescopic antenna rod. A position feedback sensor is installed in the base unit. A control unit is optically connected to the electrically driven mechanism and the position feedback sensor, forming a closed-loop control based on the signal from the position feedback sensor. This invention achieves good impedance matching within the 30MHz–80MHz frequency band, solving the problem of severe mismatch in this band with existing antennas. It provides precise tuning, good matching, and ensures that the VSWR meets test requirements across the entire frequency band.

Description

Technical Field

[0001] This invention relates to the field of tuned telescopic antenna technology, and more particularly to an electrically tuned high-power telescopic antenna system and method for use in an electromagnetic reverberation chamber. Background Technology

[0002] An electromagnetic reverberation chamber (RC) is a test device that utilizes the multiple reflections, superpositions, and interferences of electromagnetic waves within a highly conductive metal enclosed cavity to create a statistically uniform, isotropic, and randomly polarized strong electromagnetic environment. With the rapid development of new energy vehicles and intelligent connected vehicle technologies, the integration and complexity of onboard electronic systems are increasing exponentially, leading to increasingly stringent requirements for electromagnetic compatibility (EMC) performance. Automotive-grade radiated immunity testing typically requires a field strength of 200–600 V / m across the entire 30 MHz–6 GHz frequency band, with some high-safety-level components even requiring 1000 V / m. The 30–80 MHz band is a sensitive frequency band for critical components such as onboard CAN / LIN buses, power management systems, and sensor interfaces, and is also the bottleneck area for RC performance. This band is close to the lowest usable frequency (LUF) of the reverberation chamber, where the electromagnetic modes inside the cavity are sparse and the field establishment efficiency is low, necessitating the use of a high-power transmitting antenna to compensate for the insufficient field strength.

[0003] Currently, there are no high-power auto-tuned transmitting antennas specifically designed for the 30–80 MHz frequency band of electromagnetic reverberation chambers. Existing technical solutions all have significant shortcomings and cannot simultaneously meet the requirements of automotive-grade testing. The typical lower limit operating frequency of commercial standard log-periodic antennas (LPDAs) is 80 MHz, with some high-end models extending to 70 MHz. However, in the 30–80 MHz frequency band, there is a severe input impedance mismatch, and the standing wave ratio (VSWR) increases sharply, resulting in ineffective radiation of input power and even burnout of the power amplifier due to excessive reflected power. In addition, log-periodic antennas are directional broadband designs, and the low-frequency arm is too long. The mechanical strength and heat dissipation capacity are not suitable for kilowatt-level continuous wave input, which can easily lead to problems such as arm deformation, insulation breakdown, and localized overheating and burnout.

[0004] Traditional manually operated telescopic antennas rely on manually adjusting the length of a metal rod to match the quarter-wavelength resonance at different frequencies (30 MHz corresponds to a wavelength of 10 m, and 80 MHz corresponds to 3.75 m). Each time a test frequency is switched, the tester must enter the reverberation chamber's shielded cavity to manually adjust and lock the rod, with each tuning session taking 5–10 minutes. This not only results in extremely low testing efficiency but also damages the electromagnetic shielding performance of the cavity due to frequent opening and closing of the shielding door. Furthermore, personnel entering a strong electromagnetic environment pose a serious radiation exposure safety risk, making it completely incompatible with modern automated testing processes. In addition, manually operated telescopic antennas typically have limited adjustable length, failing to ensure optimal impedance matching across the entire frequency band, leading to low radiation efficiency at certain frequencies. While biconical antennas cover the 30–200 MHz band, they suffer from low radiation efficiency, poor standing wave characteristics, and power capacity typically not exceeding 500 W, making it difficult to generate the high field strength required for automotive-grade testing. Therefore, a electrically tuned high-power telescopic antenna system and method for electromagnetic reverberation chambers are needed. Summary of the Invention

[0005] The purpose of this invention is to provide an electrically tuned high-power telescopic antenna system and method for use in an electromagnetic reverberation chamber.

[0006] To achieve the above objectives, the present invention is implemented according to the following technical solution: This invention includes a base unit, to which a telescopic antenna rod is slidably connected. The electrical length can be changed by adjusting the extension length to adapt to the resonance requirements of different test frequencies. An electric drive mechanism is provided inside the base unit. The power output end of the electric drive mechanism is connected to the telescopic antenna rod and is used to drive the telescopic antenna rod to extend and retract axially. The telescopic antenna mast is electrically connected to the radio frequency feeding unit for feeding external radio frequency power into the telescopic antenna mast; the base unit is equipped with a position feedback sensor for detecting the actual extension length of the telescopic antenna mast in real time. The control unit is connected to the electric drive mechanism and the position feedback sensor via optical signal communication. It is used to drive the electric drive mechanism to adjust the telescopic antenna rod to the corresponding resonant length and to form closed-loop control based on the signal from the position feedback sensor.

[0007] Furthermore, the telescopic antenna mast is composed of multiple hollow metal tubes connected together, with a counterweight or a tip discharge head at the top; a high-power sliding electrical contact assembly is installed between the multiple metal tubes to maintain a stable electrical connection during telescopic movement.

[0008] Furthermore, the high-power sliding electrical contact assembly adopts an elastic finger spring structure or a helical spring structure.

[0009] Furthermore, the electric drive mechanism includes a servo motor, a reducer, and a transmission component. The transmission component is a ball screw or a synchronous belt drive mechanism, used to convert the rotational motion of the servo motor into the linear extension and retraction motion of the telescopic antenna mast.

[0010] Furthermore, the RF power supply unit includes a high-power RF connector and an internal impedance matching network.

[0011] Furthermore, the RF feed unit also integrates a VSWR detection module for real-time detection of antenna input impedance and VSWR data.

[0012] A tuning method for a high-power telescopic antenna for use in an electromagnetic reverberation chamber, employing the aforementioned system, includes the following steps: S1: Input the target test frequency to the control unit; S2: The control unit calculates the target resonant length based on the pre-stored mapping relationship between frequency points and lengths; S3: The control unit sends an adjustment command to the electric drive mechanism via an optical signal to drive the telescopic antenna rod to extend and retract to the target resonant length; S4: The RF feed unit detects the antenna input VSWR in real time, and the position feedback sensor detects the actual extension length of the pole in real time; S5: If the standing wave ratio exceeds the preset threshold, the control unit calculates the length correction amount based on the standing wave ratio deviation and repeats steps S3-S4 until the standing wave ratio meets the requirements.

[0013] Furthermore, methods for establishing the mapping relationship between frequency points and lengths include: The telescopic antenna mast is controlled to extend gradually in preset steps within the entire adjustable length range. At each length position, its VSWR curve in the full frequency band from 30MHz to 80MHz is measured by a vector network analyzer. Record the VSWR value at each frequency point for each length position to form a two-dimensional mapping table with length as the row and frequency as the column; For any target frequency, the length corresponding to the minimum standing wave value is selected as the tuning length of the target frequency by querying the two-dimensional mapping table.

[0014] Furthermore, the formula for calculating the length correction amount in step S5 is as follows:

[0015] Where ΔL is the length correction amount, and k is the correction coefficient. The detected standing wave ratio, This is the preset VSWR threshold. Furthermore, the entire frequency band from 30MHz to 80MHz is divided into multiple consecutive frequency sub-bands; A fixed tuning length is determined for each frequency sub-band, such that the standing wave ratio (VSWR) of the entire frequency sub-band meets the preset test requirements at that tuning length. During testing, the telescopic antenna mast is adjusted to the corresponding fixed tuning length according to the frequency sub-band to which the current test frequency belongs, so as to cover the entire sub-band.

[0016] The beneficial effects of this invention are: This invention uses a servo motor to drive the telescopic antenna pole, avoiding frequent opening and closing of the shielding door and personnel exposure to strong electromagnetic radiation, significantly improving test safety and covering the core bottleneck frequency band of the reverberation chamber.

[0017] This invention employs a 1 / 4 wavelength resonant pull rod structure to achieve good impedance matching within the 30MHz–80MHz frequency band, solving the problem of severe mismatch and ineffective radiation in the low-frequency band of traditional log-periodic antennas. It features precise tuning, good matching effect, and ensures that the VSWR meets the test requirements across the entire frequency band. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the high-power tuned telescopic antenna system in this embodiment; Figure 2 This is a flowchart illustrating the automated radiated immunity testing process using a high-power tuned telescopic antenna in this embodiment. Figure 3 This is a schematic diagram of the high-power tuned telescopic antenna structure (4-segment telescopic rod example) in this embodiment; Figure 4 This is the measured standing wave curve of a high-power tuned telescopic antenna in this embodiment; Figure 5 In this embodiment, a high-power tuned telescopic antenna was used as the transmitting antenna, and the measured field uniformity curve of the reverberation chamber was obtained. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The illustrative embodiments of the invention are provided to explain the invention, but are not intended to limit the invention.

[0020] like Figure 1 As shown, the present invention includes a base unit, a telescopic antenna rod slidably connected to the base unit, and the electrical length can be changed by adjusting the extension length to adapt to the resonance requirements of different test frequencies; an electric drive mechanism is provided in the base unit, and the power output end of the electric drive mechanism is connected to the telescopic antenna rod to drive the telescopic antenna rod to extend and retract axially. The telescopic antenna mast is electrically connected to the radio frequency feeding unit for feeding external radio frequency power into the telescopic antenna mast; the base unit is equipped with a position feedback sensor for detecting the actual extension length of the telescopic antenna mast in real time. The control unit is connected to the electric drive mechanism and the position feedback sensor via optical signal communication. It is used to drive the electric drive mechanism to adjust the telescopic antenna rod to the corresponding resonant length and to form closed-loop control based on the signal from the position feedback sensor.

[0021] In this embodiment, the antenna structure mainly consists of a base unit, a telescopic antenna mast, an electric drive mechanism, an RF feed unit, a control unit, and supporting components. The structure, function, and connection relationship of each part are as follows: 1) Base unit: As the fixing and supporting component of the entire antenna, it can be directly installed on the floor, wall or lifting tower of the reverberation chamber, providing a stable installation foundation for all other components, and at the same time serving as an electrical grounding reference to ensure the stability and safety of the antenna during operation.

[0022] 2) Telescopic Antenna Pole: This is the core radiating component of the antenna, constructed from multiple hollow metal tubes joined together, allowing for axial extension and retraction. A counterweight or a tip discharge head is installed at the top of the pole to ensure balance during extension and retraction, and to prevent tip discharge from affecting antenna performance. The bottom of the pole is slidably connected to the base unit; adjusting the extension length changes the electrical length of the antenna, thus adapting to the resonance requirements of different test frequencies. The antenna employs a 1 / 4 wavelength resonant design, balancing size and radiation efficiency to ensure the antenna can be rationally placed within the reverberation chamber and effectively radiate energy.

[0023] 3) Electric drive mechanism: Installed inside the base unit, the power output end is connected to the innermost or outermost section of the telescopic antenna mast. It is used to drive the mast to extend and retract precisely, thereby adjusting the electrical length of the antenna to achieve frequency tuning. This structure consists of a servo motor, a reducer, and a transmission component. The transmission component can be a ball screw pair or a synchronous belt drive mechanism. During operation, it converts the rotational motion of the servo motor into the linear extension and retraction motion of the mast, ensuring a smooth and precise extension and retraction process.

[0024] 4) RF Feed Unit: Responsible for efficiently feeding the RF energy from the external power amplifier into the antenna mast. It mainly includes a high-power RF connector and an internal impedance matching network. The RF connector uses high-power models such as 7 / 16 DIN or EIA flanges for connecting to the external power amplifier. The internal impedance matching network reduces power reflection, improves feeding efficiency, and ensures the antenna can withstand high power inputs of hundreds of watts to kilowatts, avoiding problems such as excessive power loss and localized overheating.

[0025] 5) Control Unit: Electrically connected to the electric drive mechanism, it uses photoelectric-to-electro-optical conversion technology for signal transmission. The control unit is located in the control room, while the electric drive mechanism is placed in the reverberation chamber along with the antenna. The control signal is converted into an optical signal and transmitted between the two. This optical signal transmission control ensures stable and reliable operation of the tuning system in high field strength environments, solving the problems of interference and tuning failure in traditional electrically controlled antennas. It also avoids radiated interference from the high field strength in the reverberation chamber to the control unit. Simultaneously, the control unit can receive external control commands. A position feedback sensor is installed on the base unit, which can detect the actual extension length of the antenna mast in real time and feed the signal back to the control unit, forming a closed-loop control to ensure the positioning accuracy of the mast extension and retraction. The control unit has a pre-stored frequency-length mapping table. When the target test frequency is input, it can automatically calculate the corresponding antenna resonant length and drive the electric drive mechanism to adjust the mast to the corresponding position, achieving automatic and rapid frequency switching without requiring manual entry into the reverberation chamber, thus improving testing efficiency and avoiding personnel safety risks.

[0026] 6) Supporting components: To ensure reliable electrical connection of each section of the pole during high-power operation, a high-power sliding electrical contact assembly is installed between each metal tube section of the telescopic antenna pole. This assembly adopts an elastic finger spring or helical spring structure, which can maintain a stable electrical connection during the extension and retraction of the pole, prevent arcing and local overheating caused by poor contact, and further improve the high-power carrying capacity and working stability of the antenna.

[0027] The electrically tuned high-power telescopic antenna system for the electromagnetic reverberation chamber also includes a forced cooling system for dissipating heat from the connection points of the RF feed unit and the telescopic antenna mast. It can stably withstand continuous wave / pulse power input at the kilowatt level and above, meeting automotive-grade testing requirements.

[0028] The antenna system has a continuous wave power carrying capacity of ≥3kW, and its operating frequency band covers 30MHz-80MHz. It has strong high power carrying capacity and meets the requirements of kW-level high field strength testing. The antenna adopts a multi-section hollow metal tube sleeve structure, combined with a high-power sliding electrical contact component, to ensure stable and reliable electrical connection during extension and retraction, and avoid poor contact, arcing, and overheating. The RF feed unit adopts a 7 / 16 DIN or EIA flange high-power interface, which can stably carry ≥3kW continuous wave power input and can establish a high field strength environment of ≥200V / m in the reverberation chamber that meets automotive-grade requirements. The base unit can be fixedly installed on the floor, wall, or lifting tower of the reverberation chamber.

[0029] This invention provides three tuning schemes: (a) Fully automatic tuning scheme This antenna achieves coverage of the 30MHz~80MHz frequency band through automatic optimized electric tuning. Combined with closed-loop control and impedance detection, it achieves adaptive matching between antenna size and target resonant frequency. The core principle is to automatically adjust the length of the telescopic rod by real-time detection of the antenna's VSWR and frequency parameters, ensuring that the antenna always operates in a resonant state. The specific method is as follows: First, clarify the core formula relating antenna resonant length to frequency. For a monopole telescopic antenna, its resonant length... Resonant frequency with the target The following relationship must be satisfied: (1) In the formula: The wavelength of the electromagnetic wave corresponding to the target frequency. The speed of light in a vacuum ( ), The target resonant frequency is (30~80MHz). The relative permittivity of the medium surrounding the antenna (reverberation chamber air) ).

[0030] This resonant length, obtained from an empirical formula, can be used as an initial value. Within a range using this length as an intermediate value, the optimal resonant length needs to be adaptively adjusted based on actual closed-loop testing. Figure 2 As shown, the adjustment steps are as follows: 1) Calculate the initial resonant length based on the target resonant frequency: The external test system inputs the target resonant frequency to the control unit. The control unit calls the formula (1) to calculate the initial resonance length. Control the electric drive telescopic pole to extend and retract to its initial length. .

[0031] 2) Real-time parameter detection and standing wave ratio (VSWR) curve scanning: The RF feed unit acquires antenna input impedance and VSWR data in real time through a built-in VSWR detection module or an externally connected vector network analyzer. Simultaneously, the position feedback sensor of the base unit detects the actual extension length of the pole in real time. ; 3) Deviation Judgment and Correction: The control unit compares the detected VSWR with the standard threshold (e.g., VSWRstd=2). If the VSWR exceeds the standard, it indicates that the current pole length does not match the target frequency. The adjustment amount is calculated using the following correction formula. : In the formula: The standard VSWR threshold (can be set as needed, such as 2). This is a correction factor (valued from 0.01 to 0.1 m depending on the antenna structure calibration) used to compensate for length errors caused by impedance deviations.

[0032] 4) Limited range, adaptive adjustment and stabilization: The control unit adjusts according to the adjustment amount. The optical signal is used to send an adjustment command to the electric drive mechanism again, causing the drive rod to extend or retract to the corrected length. or Repeat steps 2)-4) until the standing wave ratio meets the standard threshold. At this point, the length of the rod is... Once a precise match is achieved with the target resonant frequency, the adjustment process stops.

[0033] The entire process requires no manual intervention. Optical signal transmission avoids interference from the high field strength in the reverberation chamber on the control signal. Combined with formula calculation and real-time closed-loop feedback, the antenna size is adaptively adjusted to ensure that the antenna always operates in a resonant state in the 30~80MHz frequency band, thus ensuring the stability of high-power radiation and the accuracy of the test field strength.

[0034] (ii) Establishing a mapping table for rapid tuning By establishing a mapping table, the relationship between the target frequency and the resonant length can be quickly located through table lookup. The mapping table is established and maintained through preliminary experiments; the specific implementation method is as follows: 1) Confirm the tunable range [Lmin, Lmax] of the telescopic antenna length. Usually, the shortest length should be less than 1m (corresponding to 75MHz) and the maximum length should be greater than 2.5m (corresponding to 30MHz). 2) Connect the RF output of the telescopic antenna to the vector network analyzer, and set the vector network analyzer to measure the standing wave (VSWR) parameter, covering a frequency range of (30MHz~80MHz), with 51 points, i.e., a frequency point interval of 1MHz; 3) Control the telescopic antenna to start from the shortest length, in 1cm increments, and gradually adjust it to the maximum length (length span greater than 1.5m). At each length, automatically read the standing wave curve (30MHz~80MHz) and then establish a two-dimensional mapping table between standing wave and (length-frequency). 4) For each target frequency, the minimum standing wave at that frequency can be obtained by looking up a table. The resonant length corresponding to the minimum standing wave at that time can be taken as the tuning length of the target frequency.

[0035] The advantage of this method is that it only requires maintaining the two-dimensional mapping table of standing waves and (length-frequency) once. Subsequently, setting the resonant length required for the target frequency can be done simply by looking up the table, which is far more efficient than the previous automatic tuning method.

[0036] In the mapping table method, both frequency and length are discrete. If the set frequency is not in the list, data from a nearby frequency or interpolation can be used. It cannot achieve continuous frequency and length adjustment through automatic tuning.

[0037] (III) Tuning scheme with full frequency coverage of finite tuning length The telescopic antenna has a certain operating bandwidth at each tuning length. That is, after fixing the tuning length, its full-band standing wave curve will have a certain interval that is entirely below the set standard threshold (e.g., VSWRstd=2). Therefore, it can be assumed that this tuning length is used for this frequency band interval. Thus, in some cases, to further improve testing efficiency, several tuning lengths can be selected to cover the frequency band range (30MHz~80MHz), with each length covering one frequency range. This eliminates the need to tune the resonator length point by point, and uses a few lengths to cover the entire frequency band, further greatly improving efficiency.

[0038] like Figure 3 As shown, a four-segment telescopic antenna with a frequency coverage of 30MHz~80MHz is designed for a vehicle electromagnetic reverberation chamber with a working area of ​​8m×8m×3m. It is used for electromagnetic immunity testing of the vehicle. The goal is to generate a field strength of 140V / m in the reverberation chamber using a 2500W power amplifier, while maintaining the field uniformity in the reverberation chamber to meet the limit requirements.

[0039] Through actual testing and analysis, the high-power tuned telescopic antenna was modified to have five different lengths, corresponding to five center frequencies. Each length covers a 10MHz bandwidth, resulting in a total bandwidth of 50MHz. The actual test standing wave curve is shown below. Figure 4 As shown, the input impedance is well matched.

[0040] The center frequencies corresponding to the five tuning sizes, as well as the measured field strength and maximum field strength under specific power amplifier output conditions, are shown in Table 1 below.

[0041] Table 1. Field strength test results of a high-power tuned telescopic antenna in a reverberation chamber. Data shows that a 2500W power amplifier can generate a field strength greater than 140V / m.

[0042] Meanwhile, for the antenna used as a transmitting antenna, field uniformity tests were conducted in the 30MHz~80MHz frequency band. Field strength was measured at the eight vertices of the operating area, and field uniformity was calculated according to IEC61000-4-21 requirements. The test results are as follows: Figure 5 As shown.

[0043] Test results show that the field uniformity meets the standard requirements. From the actual test results of the three groups of standing wave, generated field strength and field uniformity, the designed high-power tuned telescopic antenna meets the requirements for testing in this reverberation chamber and can be used for electromagnetic compatibility testing of the whole vehicle in the range of 30MHz to 80MHz.

[0044] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A motorized tuned high-power telescopic antenna system for an electromagnetic reverberation chamber, comprising a base unit. Its characteristic is that... The telescopic antenna rod is slidably connected to the base unit. The electrical length can be changed by adjusting the extension length to adapt to the resonance requirements of different test frequencies. An electric drive mechanism is provided inside the base unit. The power output end of the electric drive mechanism is connected to the telescopic antenna rod and is used to drive the telescopic antenna rod to extend and retract axially. The telescopic antenna mast is electrically connected to the radio frequency feeding unit for feeding external radio frequency power into the telescopic antenna mast; the base unit is equipped with a position feedback sensor for detecting the actual extension length of the telescopic antenna mast in real time. The control unit is connected to the electric drive mechanism and the position feedback sensor via optical signal communication. It is used to drive the electric drive mechanism to adjust the telescopic antenna rod to the corresponding resonant length and to form closed-loop control based on the signal from the position feedback sensor.

2. The electrically tuned high-power telescopic antenna system for an electromagnetic reverberation chamber according to claim 1, characterized in that, The telescopic antenna mast is made of multiple hollow metal tubes connected together, with a counterweight or a tip discharge head at the top. High-power sliding electrical contact components are installed between the multiple metal tubes to maintain a stable electrical connection during telescopic movement.

3. The electrically tuned high-power telescopic antenna system for an electromagnetic reverberation chamber according to claim 2, characterized in that, The high-power sliding electrical contact assembly adopts an elastic finger spring structure or a helical spring structure.

4. The electrically tuned high-power telescopic antenna system for an electromagnetic reverberation chamber according to claim 1, characterized in that, The electric drive mechanism includes a servo motor, a reducer, and a transmission component. The transmission component is a ball screw or a synchronous belt drive mechanism, which is used to convert the rotational motion of the servo motor into the linear extension and retraction motion of the telescopic antenna mast.

5. The electrically tuned high-power telescopic antenna system for an electromagnetic reverberation chamber according to claim 1, characterized in that, The RF feed unit includes a high-power RF connector and an internal impedance matching network.

6. The electrically tuned high-power telescopic antenna system for an electromagnetic reverberation chamber according to claim 5, characterized in that, The radio frequency feeding unit also integrates a standing wave ratio (SWR) detection module for real-time detection of antenna input impedance and SWR data.

7. A method for tuning a high-power telescopic antenna for use in an electromagnetic reverberation chamber, employing the system described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Input the target test frequency to the control unit; S2: The control unit calculates the target resonant length based on the pre-stored mapping relationship between frequency points and lengths; S3: The control unit sends an adjustment command to the electric drive mechanism via an optical signal to drive the telescopic antenna rod to extend and retract to the target resonant length; S4: The RF feed unit detects the antenna input VSWR in real time, and the position feedback sensor detects the actual extension length of the pole in real time; S5: If the standing wave ratio exceeds the preset threshold, the control unit calculates the length correction amount based on the standing wave ratio deviation and repeats steps S3-S4 until the standing wave ratio meets the requirements.

8. The tuning method according to claim 7, characterized in that, Methods for establishing frequency-length mapping relationships include: The telescopic antenna mast is controlled to extend gradually in preset steps within the entire adjustable length range. At each length position, its VSWR curve in the full frequency band from 30MHz to 80MHz is measured by a vector network analyzer. Record the VSWR value at each frequency point for each length position to form a two-dimensional mapping table with length as the row and frequency as the column; For any target frequency, the length corresponding to the minimum standing wave value is selected as the tuning length of the target frequency by querying the two-dimensional mapping table.

9. The tuning method for a high-power telescopic antenna for an electromagnetic reverberation chamber according to claim 7, characterized in that, The formula for calculating the length correction amount in step S5 is: Where ΔL is the length correction amount, and k is the correction coefficient. The detected standing wave ratio, This is the preset VSWR threshold.

10. The tuning method for a high-power telescopic antenna for an electromagnetic reverberation chamber according to claim 7, characterized in that, The entire frequency band from 30MHz to 80MHz is divided into multiple consecutive frequency sub-bands; A fixed tuning length is determined for each frequency sub-band, such that the standing wave ratio (VSWR) of the entire frequency sub-band meets the preset test requirements at that tuning length. During testing, the telescopic antenna mast is adjusted to the corresponding fixed tuning length according to the frequency sub-band to which the current test frequency belongs, so as to cover the entire sub-band.

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