A metasurface resonant frequency calibration method and system based on compensation capacitance

Abstract

The application discloses a kind of based on compensation capacitance's metasurface resonant frequency calibration method and system, it is related to transmission technical field, it is difficult to realize simple, stable, high-precision calibration after processing is completed to the resonant frequency of the metasurface based on reconfigurable unit.The metasurface includes the array of metasurface unit being divided into more than one channel and more than one compensation capacitance branch;Compensation capacitance branch is connected to its corresponding channel or disconnected from its corresponding channel under the control of second external digital control signal, channel is switched electromagnetic state under the control of first external digital control signal;Method includes: S1, control each channel to switch to target electromagnetic state, test each channel actual resonant frequency, calculate the frequency deviation of actual resonant frequency and target resonant frequency;S2, according to frequency deviation, determine the target capacitance value of compensation capacitance;S3, in the compensation capacitance installation position of each compensation capacitance branch, access the compensation capacitance of the capacitance value matched with target capacitance value.

Description

Technical Field

[0001] This invention relates to the field of transmission technology, and in particular to a method and system for calibrating metasurface resonant frequencies based on compensation capacitors. Background Technology

[0002] In metasurfaces based on reconfigurable units, the electromagnetic state of the metasurface units is usually dynamically controlled by loading active devices. The electromagnetic state refers to the resonant frequency, reflection phase, amplitude, or polarization mode, and mainly includes two control methods: continuous control and discrete switching.

[0003] In continuous modulation methods, varactor diodes are typically used to dynamically control the electromagnetic properties of metasurface units. By changing the reverse bias voltage, the varactor diode continuously alters the junction capacitance, thereby adjusting the equivalent capacitance of the metasurface unit and achieving continuously adjustable resonant frequencies. However, this approach relies on analog control voltages, resulting in complex control circuitry that is highly sensitive to noise and electromagnetic interference. Furthermore, the capacitance adjustment range of the varactor diode is limited by the device's inherent physical characteristics, making it difficult to cover the metasurface frequency offset caused by manufacturing errors in practical applications. This restricts its use in high-precision frequency calibration scenarios.

[0004] In discrete switching control, the switching of the metal pattern structure (also called metal patch) inside the metasurface unit is generally controlled by turning on and off switching devices, thereby achieving discrete electromagnetic state switching of the metasurface unit. This method has advantages such as simple structure, strong anti-interference capability, and ease of digital control, and is therefore widely used in engineering systems. However, metasurfaces using discrete switching control typically rely on fixed structural parameters pre-determined according to the designed operating frequency, and their actual resonant frequency is basically determined after manufacturing. However, during actual processing, factors such as substrate dielectric constant deviation, processing dimensional errors, welding parasitic parameters, device parasitic parameters, or assembly errors can cause deviations between the actual resonant frequency and the simulated design value. This can cause the metasurface radar system to deviate from the designed operating frequency, affecting performance or even preventing normal operation, resulting in wasted resources.

[0005] In the process of realizing this invention, the inventors discovered at least the following problems in the prior art: The resonant frequency of metasurfaces based on reconfigurable units is difficult to calibrate simply, stably, and with high precision after fabrication. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for calibrating the resonant frequency of metasurfaces based on compensation capacitors, thereby solving the technical problem in the prior art where it is difficult to achieve simple, stable, and high-precision calibration of the resonant frequency of metasurfaces based on reconfigurable units after fabrication. The various technical effects of the preferred solutions among the many technical solutions provided by this invention are detailed below.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a metasurface resonant frequency calibration method based on compensation capacitors. The metasurface includes a metasurface unit array divided into one or more channels and one or more compensation capacitor branches. Each compensation capacitor branch is used to adjust the actual resonant frequency of its corresponding channel. The compensation capacitor branch is controlled by a second external digital control signal to connect to or disconnect from its corresponding channel. Each channel is controlled by a first external digital control signal to switch between two electromagnetic states. The method includes: step S1, using the first external digital control signal to control each channel of the processed metasurface to switch to the target electromagnetic state, testing the actual resonant frequency of each channel, and calculating the frequency deviation between the actual resonant frequency and the target resonant frequency of each channel; step S2, determining the target capacitance value of the compensation capacitor for each compensation capacitor branch based on the frequency deviation of the corresponding channel; and step S3, connecting a compensation capacitor with a capacitance value matching the target capacitance value at the installation position of the compensation capacitor for each compensation capacitor branch.

[0008] Preferably, in step S2, if the frequency deviation of the channel corresponding to the compensation capacitor branch does not fall within the preset allowable error range, then the target capacitance value of the compensation capacitor of the compensation capacitor branch is calculated; otherwise, the compensation capacitor is not connected at the installation position of the compensation capacitor of the compensation capacitor branch.

[0009] Preferably, the method further includes step S4; step S4 includes: after executing step S3, returning to execute step S1; if the frequency deviation of all the channels falls within the preset allowable error range, then the metasurface resonant frequency calibration is completed; if the frequency deviation of at least one of the channels does not fall within the preset allowable error range, then returning to execute step S1, step S2 and step S3.

[0010] Preferably, each metasurface unit includes two metal pattern structures, and a first switching unit is connected between the two metal pattern structures. The first switching unit is controlled to be turned on or off by a first external digital control signal.

[0011] Preferably, the compensation capacitor branch includes a compensation capacitor, a second switching unit, a DC loop inductor, and an AC coupling capacitor; the first end of the compensation capacitor and the first end of the DC loop inductor are both connected to the first RF node of the corresponding channel, the second end of the compensation capacitor and the second end of the DC loop inductor are both connected to the first end of the second switching unit, the second end of the second switching unit is connected to the second RF node of the corresponding channel through the AC coupling capacitor, and the second switching unit is controlled to be turned on or off by the second external digital control signal.

[0012] Preferably, the compensation capacitor branch further includes an RF isolation inductor, and the second external digital control signal controls the second switching unit to turn on or off after passing through the RF isolation inductor.

[0013] Preferably, the parallel resonant angular frequency formed by the parallel connection of the DC circuit inductor and the compensation capacitor is less than the angular frequency of the incident electromagnetic wave on the metasurface. , This represents the proportionality coefficient. .

[0014] Preferably, the second switching unit is a PIN diode, the cathode of which is connected to both the second terminal of the compensation capacitor and the second terminal of the DC circuit inductor, and the anode of which is connected to both the second terminal of the AC coupling capacitor and the first terminal of the RF isolation inductor; the impedance of the equivalent capacitance of the compensation capacitor branch is... for: ;in, Represents the imaginary unit. This represents the angular frequency of the incident electromagnetic wave on the metasurface. This refers to the AC coupling capacitor. This refers to the compensation capacitor. This represents the junction capacitance of the PIN diode.

[0015] Preferably, the compensation capacitor branch includes N branch compensation circuits, where N is an integer greater than or equal to 2, and i represents the index of the branch compensation circuit, 1≤i≤N; the i-th branch compensation circuit includes an i-th branch compensation capacitor, an i-th branch switching unit, an i-th branch DC loop inductor, and an i-th branch AC coupling capacitor; the first end of the i-th branch compensation capacitor and the first end of the i-th branch DC loop inductor are both connected to the first RF node of the corresponding channel, the second end of the i-th branch compensation capacitor and the second end of the i-th branch DC loop inductor are both connected to the first end of the i-th branch switching unit, the second end of the i-th branch switching unit is connected to the first end of the i-th branch AC coupling capacitor, and the i-th branch switching unit is controlled by the i-th branch control signal of the second external digital control signal to be turned on or off; when i equals 1, the second end of the i-th branch AC coupling capacitor is connected to the second RF node of the corresponding channel, and when i is greater than 1, the second end of the i-th branch AC coupling capacitor is connected to the first end of the (i-1)-th branch AC coupling capacitor.

[0016] This invention also discloses a metasurface system, the system comprising: a control module that outputs multiple first external digital control signals and multiple second external digital control signals; a metasurface comprising a metasurface unit array divided into one or more channels and one or more compensation capacitor branches, each of the compensation capacitor branches being used to adjust the actual resonant frequency of its corresponding channel, each of the compensation capacitor branches being controlled by one of the second external digital control signals to connect to or disconnect from its corresponding channel, and each of the channels being controlled by the first external digital control signal to switch between two electromagnetic states; the resonant frequency of the metasurface is calibrated according to a metasurface resonant frequency calibration method based on compensation capacitors provided by this invention.

[0017] Implementing one of the above-described technical solutions of the present invention has the following advantages or beneficial effects: Each channel in the metasurface is equipped with a compensation capacitor branch, which can effectively compensate for the resonant frequency deviation of the processed metasurface without changing the main structure of the metasurface. The target capacitance value of the compensation capacitor is calculated based on the actual frequency deviation, and the compensation capacitor is selected and installed according to the target capacitance value. This enables large frequency deviation calibration of the resonant frequency, so that the actual operating frequency of the metasurface is aligned with the design target frequency point, thereby avoiding performance degradation or system failure caused by resonant frequency deviation, and improving product consistency and yield. The first external digital control signal controls the channel to switch stably and reliably between at least two electromagnetic states, and the second external digital control signal controls whether the compensation capacitor branch is connected to its corresponding channel. This avoids the problems of noise and electromagnetic interference that are easily susceptible when using analog control signals, and has higher stability and reliability. It is suitable for engineering applications in complex electromagnetic environments, and the overall structure is simple and low in cost. Each channel is calibrated independently, which greatly improves the resonant frequency calibration accuracy. It is particularly suitable for large-scale array structures, improving the overall array consistency and system performance. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of a capacitor compensation circuit set in a certain channel of the metasurface in Embodiment 1 of the present invention; Figure 2 This is a flowchart illustrating the metasurface resonant frequency calibration method based on compensation capacitor according to Embodiment 1 of the present invention. Figure 3 This is a schematic diagram of the state transition of the metasurface resonant frequency calibration method based on compensation capacitor according to Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of a capacitor compensation circuit set in a channel of the metasurface in Embodiment 2 of the present invention; Figure 5 This is a system block diagram of Embodiment 3 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, various exemplary embodiments described below will be referenced to the accompanying drawings, which form part of the exemplary embodiments, illustrating various exemplary embodiments that may be used to implement the present invention. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. It should be understood that they are merely examples of processes, methods, and apparatuses consistent with some aspects of the present invention disclosed as detailed in the appended claims, and other embodiments may be used, or structural and functional modifications may be made to the embodiments listed herein without departing from the scope and spirit of the present invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," etc., indicate the orientation or positional relationship based on the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the referred element must have a specific orientation, or be constructed and operated in a specific orientation. The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. The term "multiple" means two or more. The terms "connected" and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, integral connections, mechanical connections, electrical connections, communication connections, direct connections, indirect connections through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more of the related listed items. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] To illustrate the technical solution described in this invention, specific embodiments are described below, showing only the parts related to the embodiments of this invention.

[0022] Example 1: This invention provides a method for calibrating the resonant frequency of a metasurface based on a compensation capacitor.

[0023] In this embodiment, the metasurface includes a metasurface unit array divided into one or more channels and one or more compensation capacitor branches. Each compensation capacitor branch is used to adjust the actual resonant frequency of its corresponding channel. The compensation capacitor branch is controlled by a second external digital control signal to connect to or disconnect from its corresponding channel. Each channel is controlled by a first external digital control signal to switch between two electromagnetic states.

[0024] It is understandable that a metasurface element array is formed by arranging multiple metasurface elements in an array-like manner. The metasurface element array is divided into one or more channels, each channel comprising one or more metasurface elements. Each channel corresponds one-to-one with a compensation capacitor branch, and each channel independently calibrates its resonant frequency, improving frequency calibration accuracy. The channels in the metasurface element array are not limited to being divided according to rows, columns, or other arbitrary shapes. For example, all metasurface elements in one or more rows of the metasurface element array can be grouped into one channel; or, all metasurface elements in one or more columns of the metasurface element array can be grouped into one channel; or, metasurface elements within any shaped region of the metasurface element array can be grouped into one channel; or, the entire metasurface element array can be treated as a single channel to achieve global compensation. Figure 1 An example is shown where all the metasurface cells in a row of a metasurface cell array are arranged into a channel, and a compensation capacitor branch is configured for that channel.

[0025] Understandably, a first switching unit is set in each channel. This first switching unit is controlled by a first external digital control signal to turn on and off, thereby controlling the connection or disconnection between the metal pattern structures within all metasurface units in the channel, thus achieving the switching of the channel's electromagnetic state. When the electromagnetic state is at the resonant frequency, the channel switches between the first and second resonant frequencies by controlling the high or low level of the first external digital control signal. Similarly, the electromagnetic state can also be a reflection phase, amplitude, or polarization mode.

[0026] Preferably, such as Figure 1 and Figure 4 As shown, each metasurface unit comprises two metallic patterned structures (i.e. Figure 1 and Figure 4The metasurface unit (with a single copper foil) has a first switching unit connected between two metal pattern structures. This first switching unit is not limited to a PIN diode or a MEMS (Micro-Electro-Mechanical Systems) switch, but is preferably a PIN diode for its simpler structure. The first switching unit is controlled by a first external digital control signal to turn on or off. When the first switching unit is on, the two metal pattern structures within its metasurface unit are connected; when the first switching unit is off, the two metal pattern structures within its metasurface unit are disconnected. The metal pattern structures at one end of all metasurface units within the channel are sequentially connected in series to form a first connection link, which is connected to a first radio frequency (RF) node. The metal pattern structures at the other end of all metasurface units are sequentially connected in series to form a second connection link, which is connected to a second RF node. The on / off state of all first switching units within the channel is synchronously controlled by a single first external digital control signal. When the first switching unit is a PIN diode, the cathode of the PIN diode is connected to the metal pattern structure at one end of its metasurface unit, and the anode of the PIN diode is connected to the metal pattern structure at the other end of its metasurface unit. The first RF node can be the reference voltage of the metasurface, such as DC ground. The second radio frequency node can be a point in the second connection link.

[0027] This embodiment addresses the frequency deviation between the actual resonant frequency and the designed operating frequency of existing metasurfaces, which is affected by factors such as substrate dielectric constant deviation, processing dimensional errors, welding parasitic parameters, or assembly errors during processing. Using varactor diodes to adjust this frequency deviation presents problems such as complex control circuitry, weak anti-interference capability, and limited adjustment range. This embodiment configures a simple, easy-to-implement, and highly anti-interference compensation capacitor branch for each channel in the metasurface. This compensation capacitor branch alters the equivalent capacitance of the channel, fine-tuning its equivalent LC resonant frequency to compensate for the aforementioned frequency deviation. The compensation capacitor branch is controlled by a second external digital control signal; digital signal control improves control stability. During the initial or trial processing of the metasurface, the compensation capacitors are not installed; installation positions are reserved, and installation is performed after calibration to determine the target capacitance value. If the metasurface production environment is stable, in subsequent batch processing, the compensation capacitors for each channel can refer to the target capacitance value determined during the initial or trial processing without repeated calibration, improving efficiency.

[0028] To better understand the technical principles of this embodiment, the specific circuit structure of the compensation capacitor branch is described below.

[0029] To ensure the compensation capacitor branch has good anti-interference capability and matches the original metasurface structure, in the preferred embodiment of this example, please refer to... Figure 1 As shown, the compensation capacitor branch includes a compensation capacitor. Second switching unit, DC circuit inductor AC coupling capacitor Compensation capacitor First terminal and DC circuit inductor The first end of each terminal is connected to the first RF node of the corresponding channel, and the compensation capacitor The second terminal and DC circuit inductor The second terminal of each is connected to the first terminal of the second switching unit, and the second terminal of the second switching unit is connected via an AC coupling capacitor. The second RF node connected to the corresponding channel has its second switching unit controlled by a second external digital control signal to be turned on or off. Compensation capacitor. Used to change the equivalent capacitance of its channel (i.e., the corresponding channel) and to provide an AC path for the radio frequency signals of the metasurface.

[0030] Among them, DC circuit inductance This provides a DC bias loop from the second switching unit to the first RF node of the channel for the second external digital control signal, preventing high-frequency RF signals from interfering with the second external digital control signal. AC coupling capacitor. Achieving AC coupling between the compensation capacitor branch and the original structure of the metasurface helps the compensation capacitor... It plays a tuning role and also has a DC isolation function, preventing the DC component of the second external digital control signal from affecting the metasurface operation. (AC coupling capacitor) The first end is connected to the second RF node of the corresponding channel, and the AC coupling capacitor... The second terminal is connected to the second terminal of the second switching unit. The second switching unit can be a PIN diode or an RF MEMS switch, preferably a PIN diode, which is easier to control.

[0031] In a preferred embodiment of this first example, to achieve radio frequency isolation and protection of the control module at the second external digital control signal terminal, preferably, as follows: Figure 1 As shown, the compensation capacitor branch also includes an RF isolation inductor. The second external digital control signal passes through an RF isolation inductor. The second switch unit is then turned on or off. See the attached diagram for detailed connection information. Figure 1 RF isolation inductor The first terminal is connected to the AC coupling capacitor. The second terminal is connected to the second terminal of the second switching unit, and the radio frequency isolation inductor is connected to the second terminal of the second switching unit. The second end is connected to the control module, which is used to receive a second external digital control signal.

[0032] In this preferred embodiment, the second switching unit is set as a PIN diode, please see... Figure 1 As shown, the cathode of the PIN diode is simultaneously connected to the compensation capacitor. The second terminal and DC circuit inductor The second terminal is connected; the anode of the PIN diode is connected to the AC coupling capacitor. The second terminal and the RF isolation inductor The first terminal is connected, and the anode of the PIN diode is used as the PIN diode switch control terminal, which is controlled by a second external digital control signal.

[0033] In this preferred embodiment, in order to reduce the inductance of the DC circuit For compensation capacitors The effect of compensation, more preferably, is that the DC circuit inductance... and compensation capacitor Parallel resonant angular frequency formed by parallel connection Angular frequency of incident electromagnetic waves smaller than that of the metasurface of , This represents the proportionality coefficient. That is, satisfying This makes the DC circuit inductance and compensation capacitor The parallel circuit exhibits a stable and controllable capacitive impedance under radio frequency conditions, aiming to ensure that the compensation capacitor branch only affects the resonant frequency of the original metasurface structure. At this point, the equivalent compensation capacitance of the compensation capacitor branch... impedance for: ;in, Represents the imaginary unit (with values ​​of...) ), This represents the angular frequency of the incident electromagnetic wave on the metasurface. This represents the junction capacitance of the PIN diode (substitute its value into the calculation formula above). For ease of calculation, the capacitance of the AC coupling capacitor C2 can be set large enough that its effect can be ignored.

[0034] Before performing resonant frequency calibration, step S0 is performed: the above-mentioned metasurface is fabricated.

[0035] Taking metasurfaces applied to radar systems as an example, the target resonant frequency of the metasurface unit is determined based on the radar system's operating frequency band, target center frequency, bandwidth requirements, and metasurface unit size constraints. f tar The initial structural parameters were obtained through electromagnetic simulation. Based on the simulation design results, a metasurface array structure was fabricated, and PIN diodes (first switching units) were welded between adjacent metal pattern structures within the metasurface unit to achieve digital state switching of the metasurface unit. The array size can be set to 8×8, 16×16, etc., according to application requirements. Simultaneously, compensation capacitor branch elements were welded at each channel, and installation positions for the compensation capacitors were reserved.

[0036] like Figure 2 As shown, the metasurface resonant frequency calibration method based on compensation capacitance provided in this embodiment includes: Step S1: Using the first external digital control signal, control each channel of the processed metasurface to switch to the target electromagnetic state, and test the actual resonant frequency of each channel. Calculate the actual resonant frequency of each channel. Resonant frequency with the target frequency deviation .

[0037] In this embodiment, the target electromagnetic state can be determined by selecting one of the two electromagnetic states of the channel as needed. Preferably, the electromagnetic state of the channel when the first switching unit is turned on is selected as the target electromagnetic state. At this time, the influence of the device parasitic parameter error and installation error of the first switching unit on the resonant frequency can be calibrated simultaneously, which helps to improve the resonant frequency calibration accuracy.

[0038] In this embodiment, the resonant frequency of each channel is not limited to being tested using existing vector network analyzers, radar echo test systems, or other RF test equipment.

[0039] Step S2: Determine the target capacitance value of each compensation capacitor branch based on the frequency deviation of the corresponding channel of each compensation capacitor branch.

[0040] To avoid overcalibration and improve calibration efficiency, preferably, in step S2, if the frequency deviation of the corresponding channel of the compensation capacitor branch does not fall within the preset allowable error range, then the target capacitance value of the compensation capacitor of the compensation capacitor branch is calculated; otherwise, the compensation capacitor is not connected at the installation position of the compensation capacitor of the compensation capacitor branch. It is understood that the preset allowable error range is determined based on the actual application requirements of the metasurface. In the example of the metasurface being applied to a radar system, if the radar detection metasurface has a target center frequency of 10 GHz, then its preset allowable error range can be ±50 MHz.

[0041] In this embodiment, the specific calculation process for the target capacitance value of the compensation capacitor includes: Based on the LC resonance theory and the frequency deviation of the corresponding channel in the compensation capacitor branch, the equivalent capacitance of the channel when it reaches the target resonant frequency is derived in reverse. The equivalent capacitance Subtract the equivalent capacitance of this channel before it is connected to the compensation capacitor branch. Obtain the equivalent capacitance of the compensation capacitor branch. , Then follow the formula Calculate the compensation capacitor The target capacitance value.

[0042] In this embodiment, to improve calibration efficiency, a mapping table between the channel frequency deviation and the target capacitance value of the compensation capacitor can be pre-built. After calculating the channel frequency deviation, the target capacitance value of the compensation capacitor can be found by looking up the mapping table.

[0043] Step S3: Connect a compensation capacitor with a capacitance value matching the target capacitance value at the installation position of the compensation capacitor in each compensation capacitor branch. The connection method is welding or base plugging, etc.

[0044] In this embodiment, matching the capacitance value with the target capacitance value means that the capacitance value is equal to the compensation capacitor, or that the capacitance value is closest to the compensation capacitor in the capacitor selection table. In practical applications, if it is necessary to reduce the resonant frequency, the compensation capacitor is connected to increase the equivalent capacitance; if compensation is not required, the compensation capacitor is disconnected.

[0045] In a preferred embodiment of this invention, the metasurface resonant frequency calibration method based on compensation capacitors further includes step S4. Step S4 includes: after executing step S3, returning to execute step S1; if the frequency deviation of all channels falls within the preset allowable error range, the metasurface resonant frequency calibration is completed; if the frequency deviation of at least one channel does not fall within the preset allowable error range, returning to execute steps S1, S2, and S3, and so on, until the design requirements are met. In this preferred embodiment, after the compensation capacitor is connected, the resonant frequency of the metasurface channel is tested again to determine whether it falls within the target allowable range. If a deviation still exists, a compensation capacitor with a different capacitance value can be replaced.

[0046] Figure 3 The flowchart illustrating steps S0, S1, S2, S3, and S4 in this embodiment is shown, including the following state transition conditions: ① The actual resonant frequency does not meet the design requirements; ② The actual resonant frequency meets the design requirements. The design requirements refer to the frequency deviation of all channels falling within a preset allowable error range.

[0047] In this embodiment, during the processing stage, the above-mentioned metasurfaces can be processed in small batches sequentially, and calibration is completed according to the above-mentioned metasurface resonant frequency calibration method based on compensation capacitors. The variance of the compensation capacitor value corresponding to each channel in this small batch is calculated. If the variance is less than the variance threshold, it indicates that the processing environment is stable. Then, the median value of the compensation capacitor value corresponding to each channel in this small batch is selected and directly used as the compensation capacitor value corresponding to that channel in subsequent processing to improve processing efficiency. If the variance is not less than the variance threshold, the next small batch processing is carried out, and the metasurface resonant frequency calibration method based on compensation capacitors is executed in the next small batch processing.

[0048] In practical applications of metasurfaces, the phase difference between any two channels needs to be equal to or close to the target phase difference between the two channels. However, due to factors such as substrate dielectric constant deviation, processing size error, welding parasitic parameters, device parasitic parameters, or assembly errors, the actual resonant frequency of the channel deviates from the target resonant frequency, causing the actual phase difference between the two channels to deviate from its target phase difference. When the difference between the actual phase difference and the target phase difference is large, adjustment is required. Specifically, it is only necessary to reduce the actual resonant frequency of one of the two channels (i.e., connect a capacitor compensation branch) to make the actual phase difference between the two channels close to or equal to the target phase difference.

[0049] Example 2: This embodiment provides a metasurface resonant frequency calibration method based on compensation capacitors. The difference between this embodiment and Embodiment 1 is that the compensation capacitor branches corresponding to all or part of the channels are configured as a multi-stage structure. The multi-stage structure is as follows: Figure 4 As shown, the compensation capacitor branch includes N branch compensation circuits, where N is an integer greater than or equal to 2, and i represents the index of the branch compensation circuit, 1≤i≤N, forming a... One compensation tier; The i-th branch compensation circuit includes the i-th branch compensation capacitor. The i-th branch switching unit, the i-th branch DC circuit inductor AC coupling capacitor of the i-th branch ; The compensation capacitor of the i-th branch The first terminal and the i-th branch DC loop inductor The first end of each terminal is connected to the first RF node (e.g., DC ground) of the corresponding channel, and the i-th branch compensation capacitor The second terminal and the i-th branch DC loop inductor The second terminal of each branch is connected to the first terminal of the i-th branch switching unit, and the second terminal of the i-th branch switching unit is connected to the i-th branch AC coupling capacitor. The first end is connected, and the i-th branch switch unit is controlled by the i-th branch control signal of the second external digital control signal to turn on or off; When i equals 1, the AC coupling capacitor of the i-th branch The second end is connected to the second RF node of the corresponding channel; when i is greater than 1, the i-th branch AC coupling capacitor The second terminal is AC coupled to the (i-1)th branch capacitor. The first end is connected, which is equivalent to N branch AC coupling capacitors connected in series and then connected to the second RF node of the corresponding channel.

[0050] In this embodiment, preferably, as follows: Figure 4As shown, the i-th branch switching unit can be a PIN diode, and the cathode of the PIN diode is connected to the inductor of the i-th branch DC circuit. The second terminal is connected to the anode of the PIN diode and the AC coupling capacitor of the i-th branch. The first end is connected.

[0051] More preferably, such as Figure 4 As shown, the i-th branch compensation circuit also includes an i-th branch RF isolation inductor. This is used to block radio frequency signals in the radar receiving or radiating path from entering the control module, serving as radio frequency isolation and protection for the control circuit. The i-th branch radio frequency isolation inductor... The first terminal is connected to the anode of the PIN diode, and the i-th branch is an RF isolation inductor. The second end receives the i-th branch control signal of the second external digital control signal.

[0052] In this embodiment, the second external digital control signal includes N branch control signals, each controlling the connection or disconnection of a branch compensation circuit, which can achieve... One type of capacitor compensation scheme, namely Multiple compensation levels. The capacitance values ​​of the N branch compensation capacitors are set according to binary weights or equal intervals, thereby achieving multi-level discrete frequency modulation and covering a wider frequency range. This method can improve frequency calibration resolution while maintaining the advantages of digital control.

[0053] Example 3: This invention also discloses a metasurface system, please see Figure 5 As shown, the system includes: The control module outputs multiple first external digital control signals and multiple second external digital control signals. The control module is not limited to FPGA (Field Programmable Gate Array), MCU (Microcontroller Unit), CPLD (Complex Programmable Logic Device), or other controllers capable of outputting digital control levels.

[0054] The metasurface includes an array of metasurface units divided into one or more channels and one or more compensation capacitor branches. Each compensation capacitor branch is used to adjust the actual resonant frequency of its corresponding channel. Each compensation capacitor branch is controlled by a second external digital control signal to connect to or disconnect from its corresponding channel. Each channel is controlled by a first external digital control signal to switch between two electromagnetic states. The resonant frequency of the metasurface is calibrated according to a metasurface resonant frequency calibration method based on compensation capacitors provided in Embodiment 1 or Embodiment 2.

[0055] In this embodiment, when using Figure 1When the compensation capacitor branch is shown, the metasurface system operates as follows: When the metasurface is in normal working condition, the control module outputs multiple external digital control signals to control the first switching unit (PIN diode) in each channel to conduct, achieving predetermined electromagnetic encoding or beam control. When a deviation of the actual resonant frequency of a channel from the target resonant frequency is detected, the control module outputs a second external digital control signal to the second switching unit (PIN diode) of the corresponding capacitor compensation branch of that channel, causing the compensation capacitor of that compensation branch to... Connect to the resonant circuit. Since the resonant frequency of the metasurface unit is determined by both the equivalent inductance and equivalent capacitance, a compensation capacitor is used. The connection alters the channel's equivalent capacitance, thus shifting the actual resonant frequency toward the target resonant frequency. Simultaneously, the RF isolation inductor... Presents high impedance to radio frequency signals to prevent radio frequency energy from entering the control terminal of the control module; DC loop inductance. Provides a stable DC path for the second external digital control signal; compensation capacitor It provides an AC path for radio frequency signals, so that the compensation effect can be applied to the metasurface resonant circuit.

[0056] Compared with existing technologies, this invention achieves post-calibration and fine-tuning of the resonant frequency by introducing a controllable compensation capacitor branch into a metasurface structure based on reconfigurable units. Without altering the original main structure and control architecture, it significantly improves system performance and engineering practicality, specifically offering the following beneficial effects: 1. Ability to calibrate frequency after machining errors This invention can effectively compensate for the resonant frequency shift caused by substrate parameter deviation, dimensional error and welding parasitic effect after the metasurface is processed, so that the actual operating frequency is re-aligned with the design target resonant frequency, thereby avoiding performance degradation or system failure caused by frequency deviation, and improving product consistency and yield.

[0057] 2. Maintains a digital control architecture with strong anti-interference capabilities. Compared to varactor diode solutions that rely on analog bias voltage, this invention employs a digital control unit (i.e., control module) such as an FPGA to control the connection and disconnection of the compensation capacitor through high and low level signals. This avoids the problem of analog control signals being susceptible to noise and electromagnetic interference, resulting in higher stability and reliability, making it suitable for engineering applications in complex electromagnetic environments. It eliminates the need for complex analog modulation circuits or high-precision bias networks, resulting in a simple overall structure, low design and implementation costs, and easy compatibility and integration with existing metasurface systems based on PIN diodes.

[0058] 3. Possesses discrete and controllable frequency adjustment capability. Each channel's independent second external digital control signal supports channel-level, row-column-level, or zone-level compensation design for the metasurface unit array. It allows for independent calibration of frequency deviations in different regions, making it particularly suitable for large-scale array structures and improving overall array consistency and system performance. In multi-level structures, by setting one or more compensation capacitors with different capacitance values ​​and controlling their combination state with multi-branch control signals, multi-level discrete resonant frequency adjustment can be achieved to meet the tuning requirements of different application scenarios and more flexibly change the operating frequency band of the metasurface.

[0059] The embodiment is merely a specific example and does not indicate that this is the only way to implement the present invention.

[0060] The above description is merely a preferred embodiment of the present invention. Those skilled in the art will understand that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for calibrating the resonant frequency of a metasurface based on a compensation capacitor, characterized in that, The metasurface includes a metasurface unit array divided into one or more channels and one or more compensation capacitor branches; each compensation capacitor branch is used to adjust the actual resonant frequency of its corresponding channel, and the compensation capacitor branch is controlled by a second external digital control signal to connect to or disconnect from its corresponding channel, and each channel is controlled by a first external digital control signal to switch between two electromagnetic states; the method includes: Step S1: Using the first external digital control signal, control each channel of the metasurface after processing to switch to the target electromagnetic state, test the actual resonant frequency of each channel, and calculate the frequency deviation between the actual resonant frequency and the target resonant frequency of each channel. Step S2: Determine the target capacitance value of the compensation capacitor for each compensation capacitor branch based on the frequency deviation of the corresponding channel of each compensation capacitor branch. Step S3: Connect the compensation capacitor with a capacitance value matching the target capacitance value at the installation position of the compensation capacitor in each of the compensation capacitor branches. The compensation capacitor branch includes N branch compensation circuits, where N is an integer greater than or equal to 2, and i represents the index of the branch compensation circuit, 1≤i≤N; The i-th branch compensation circuit includes the i-th branch compensation capacitor, the i-th branch switching unit, the i-th branch DC loop inductor, and the i-th branch AC coupling capacitor; The first terminal of the i-th branch compensation capacitor and the first terminal of the i-th branch DC loop inductor are both connected to the first RF node of the corresponding channel. The second terminal of the i-th branch compensation capacitor and the second terminal of the i-th branch DC loop inductor are both connected to the first terminal of the i-th branch switching unit. The second terminal of the i-th branch switching unit is connected to the first terminal of the i-th branch AC coupling capacitor. The i-th branch switching unit is controlled by the i-th branch control signal of the second external digital control signal to be turned on or off. When i equals 1, the second end of the i-th branch AC coupling capacitor is connected to the second RF node of the corresponding channel. When i is greater than 1, the second end of the i-th branch AC coupling capacitor is connected to the first end of the (i-1)-th branch AC coupling capacitor.

2. The metasurface resonant frequency calibration method based on compensation capacitor according to claim 1, characterized in that, In step S2, if the frequency deviation of the channel corresponding to the compensation capacitor branch does not fall within the preset allowable error range, the target capacitance value of the compensation capacitor of the compensation capacitor branch is calculated; otherwise, the compensation capacitor is not connected at the installation position of the compensation capacitor of the compensation capacitor branch.

3. The metasurface resonant frequency calibration method based on compensation capacitance according to claim 1, characterized in that, The method further includes step S4; step S4 includes: After completing step S3, return to step S1. If the frequency deviation of all channels falls within the preset allowable error range, the metasurface resonant frequency calibration is completed. If the frequency deviation of at least one channel does not fall within the preset allowable error range, return to execute steps S1, S2, and S3.

4. The metasurface resonant frequency calibration method based on compensation capacitance according to claim 1, characterized in that, Each metasurface unit includes two metallic patterned structures, and a first switching unit is connected between the two metallic patterned structures. The first switching unit is controlled to be turned on or off by a first external digital control signal.

5. The metasurface resonant frequency calibration method based on compensation capacitance according to claim 1, characterized in that, The compensation capacitor branch includes a compensation capacitor, a second switching unit, a DC circuit inductor, and an AC coupling capacitor; The first end of the compensation capacitor and the first end of the DC loop inductor are both connected to the first radio frequency node of the corresponding channel. The second end of the compensation capacitor and the second end of the DC loop inductor are both connected to the first end of the second switching unit. The second end of the second switching unit is connected to the second radio frequency node of the corresponding channel through the AC coupling capacitor. The second switching unit is controlled by the second external digital control signal to turn on or off.

6. The metasurface resonant frequency calibration method based on compensation capacitor according to claim 5, characterized in that, The compensation capacitor branch also includes an RF isolation inductor, and the second external digital control signal controls the second switching unit to turn on or off after passing through the RF isolation inductor.

7. The metasurface resonant frequency calibration method based on compensation capacitance according to claim 6, characterized in that, The parallel resonant angular frequency formed by the parallel connection of the DC circuit inductor and the compensation capacitor is less than the angular frequency of the incident electromagnetic wave on the metasurface. , Represents the proportionality coefficient. .

8. The metasurface resonant frequency calibration method based on compensation capacitance according to claim 7, characterized in that, The second switching unit is a PIN diode. The cathode of the PIN diode is connected to both the second terminal of the compensation capacitor and the second terminal of the DC loop inductor. The anode of the PIN diode is connected to both the second terminal of the AC coupling capacitor and the first terminal of the RF isolation inductor. The impedance of the equivalent capacitance of the compensation capacitor branch for: ； in, Represents the imaginary unit. This represents the angular frequency of the incident electromagnetic wave on the metasurface. This refers to the AC coupling capacitor. This refers to the compensation capacitor. This represents the junction capacitance of the PIN diode.

9. A metasurface system, characterized in that, The system includes: The control module outputs multiple channels of first external digital control signals and multiple channels of second external digital control signals; The metasurface includes an array of metasurface units divided into one or more channels and one or more compensation capacitor branches. Each compensation capacitor branch is used to adjust the actual resonant frequency of its corresponding channel. Each compensation capacitor branch is controlled by a second external digital control signal to be connected to or disconnected from its corresponding channel. Each channel is controlled by a first external digital control signal to switch between two electromagnetic states. The resonant frequency of the metasurface is calibrated according to a metasurface resonant frequency calibration method based on compensation capacitors according to any one of claims 1-8.

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