Reconfigurable antenna based on liquid metal and polarization reconstruction method

Abstract

The invention discloses a reconfigurable antenna based on liquid metal and a polarization reconfiguration method. The reconfigurable antenna comprises a patch layer (1), a first transparent substrate (2), a first foam layer (3), a first ground layer (4), a second transparent substrate (5), a second foam layer (6), a third transparent substrate (7) and a second ground layer (8) which are sequentially arranged from top to bottom. A first groove is formed in the lower surface of the first foam layer (3), and an LED module (9) is embedded in the first groove; a second groove is formed in the upper surface of the second foam layer (6), and a PD module (10) is embedded in the second groove; a microfluid channel (11) is fixed to the upper surface of the second transparent substrate (5), one end of the microfluid channel is connected with a pump through a pipeline, the other end of the microfluid channel is connected with a liquid metal container through a pipeline, and flowing of liquid metal is controlled through the pump.

Description

Technical Field

[0001] The present invention relates to the field of antenna design, and in particular to a liquid metal-based reconfigurable antenna and a polarization reconstruction method. Background Art

[0002] In order to increase the versatility of antennas, improve their adaptability to complex environments, and enhance compatibility with different platforms, antennas need to have the ability to flexibly modify parameters according to different communication scenarios and channel requirements to achieve diverse radiation characteristics. At present, reconfigurable antennas mostly use solid metals, mainly through three methods: electronic component tuning, mechanical drive tuning, and special material tuning. In terms of electronic component tuning, varactor diodes, pin diodes, and their combinations are mainly used to reconfigure antenna functions. Mechanical drive tuning changes the antenna structure through physical stretching, rotation, or microelectromechanical system switches (MEMS). Although reconfigurable antennas with solid-state devices have the advantages of fast response, low power consumption, and high reliability, their reconstruction range is limited, and it is difficult to achieve wide-range state reconstruction through switching elements such as diodes. At the same time, active RF devices may cause nonlinear effects, limit power carrying, and have DC bias circuit stability problems, making the antenna structure more complex. In terms of special material tuning, water and liquid metal are used as media to adjust the antenna radiation structure through the fluid properties of the liquid. In particular, liquid metal, because of its metallicity and fluidity, has shown excellent reconstruction performance in domestic and foreign research.

[0003] At present, most of the reconfigurable antennas based on liquid metal are discrete state reconfigurable antennas, and the reconfiguration state can only be switched between a limited number of states. The current liquid metal reconfiguration drive antenna mainly adopts two driving methods: air pressure and voltage reconstruction. In terms of air pressure control, air pumps and syringes are mainly used as air pressure control components. The movement of liquid metal in the channel is controlled by changing the air pressure difference at both ends of the microfluidic channel in the antenna to change the metal structure of the antenna; in terms of voltage control, antenna reconstruction relies on electrochemical methods to control the movement of liquid metal by changing the bias voltage. However, both methods rely on visual feedback from the human eye, and engineers are required to manually adjust the antenna reconstruction state. This results in problems such as low antenna reconstruction speed, low liquid metal control accuracy, and more oxide residues, which have a great impact on antenna performance. At present, there is no high-precision continuous reconstruction solution for liquid metal antennas. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a reconfigurable antenna and polarization reconstruction method based on liquid metal. The liquid metal is driven by a continuous reconstruction method so that the antenna can realize the frequency-polarization reconfigurable function, and the polarization reconstruction direction can be continuously turned. The liquid metal reconfigurable antenna is automatically switched in polarization direction according to program design by an adaptive driving method.

[0005] The object of the present invention is achieved by the following technical solution: a liquid metal-based reconfigurable antenna, comprising a patch layer, a first transparent substrate, a first foam layer, a first ground layer, a second transparent substrate, a second foam layer, a third transparent substrate and a second ground layer, which are arranged in sequence from top to bottom;

[0006] The lower surface of the first foam layer is provided with a first groove, in which an LED module is embedded; the upper surface of the second foam layer is provided with a second groove, in which a PD module is embedded;

[0007] A microfluidic channel is fixed on the upper surface of the second transparent substrate. One end of the microfluidic channel is connected to a pump through a pipeline, and the other end is connected to a liquid metal container through a pipeline. The flow of the liquid metal is controlled by the pump.

[0008] The PD module is used to monitor the flow of liquid metal. The light signal emitted by the LED module will be received by the PD module. As the flow state of the liquid metal changes, the electrical signal output by the PD module will also change.

[0009] The first ground layer is a coupling layer, which adopts a patterned copper layer, and a plurality of concentric circular grooves with different radii are etched on the coupling layer; the energy on the feeder line can be coupled to the patch layer through the circular grooves on the coupling layer to generate radiation;

[0010] There are two microfluidic channels in total, and the feeder is a T-shaped feeder, which includes three feeder arms, a first end of the first feeder arm is connected to the first microfluidic channel, a second end of the first feeder arm is connected to the first end of the second feeder arm, and a second end of the second feeder arm is connected to the second microfluidic channel;

[0011] The first feeder arm and the second feeder arm are located on the same straight line, the first end of the third feeder arm of the T-shaped feeder is connected to the second end of the first feeder arm, and the second end of the third feeder arm is used for feeding power; and the third feeder arm and the first feeder arm are perpendicular to each other;

[0012] The coupling layer is also provided with two rectangular grooves, wherein the first rectangular groove is located directly above the first microfluidic channel, and the second rectangular groove is located directly above the second microfluidic channel; and is used to allow the light signal emitted by the LED module in the first groove to pass through the rectangular groove and irradiate the first microfluidic channel and the second microfluidic channel;

[0013] The number of the second grooves is 2, the first second groove corresponds to the first microfluidic channel and is located directly below the first microfluidic channel, and the other second groove corresponds to the second microfluidic channel and is located directly below the second microfluidic channel;

[0014] The PD module in each second groove is composed of a plurality of PD units, and each PD unit outputs corresponding voltage data according to the light signal collected passing through the corresponding microfluidic channel, thereby detecting the position of the liquid metal in the microfluidic channel;

[0015] For any microfluidic channel, take the connection point between the microfluidic channel and the T-type feeder as the starting point, project the centers of each PD unit in the second groove below the microfluidic channel onto the microfluidic channel, and measure the distance between the projection point position of each PD unit center and the starting point.

[0016] The first feeder arm and the second feeder arm are only connected to the liquid metal in the microfluidic channel, and the liquid metal is used to change the shape of the feeder; it should be noted that the liquid metal injection port of the microfluidic channel is located at the end of the T-shaped feeder. In a low-height flow channel (the flow channel height is less than 1mm), the high viscosity of the liquid metal enables the metal liquid to achieve uniform cross-sectional filling without stratification or deviation.

[0017] A polarization reconstruction method of a reconfigurable antenna based on liquid metal, comprising the following steps:

[0018] Step 1: Connect the LED module and the two PD modules in the second groove to the STM32 microcontroller;

[0019] Driven by the STM32 microcontroller, the LED module emits a uniform light signal. When the liquid metal flows to the target position, the light signal at the target position will be blocked.

[0020] Step 2: for any PD module in the second groove, each PD unit contained therein outputs corresponding voltage data according to the collected optical signal;

[0021] The voltage data is converted into ADC value through ADC and transmitted to the STM32 microcontroller;

[0022] First, two thresholds are set, denoted as ADC1 and ADC2, where ADC1 is smaller than ADC2;

[0023] It is defined that when the ADC value is less than ADC1, the corresponding PD unit is completely blocked by the liquid metal, and when the ADC value is greater than ADC2, the corresponding PD module is not blocked by the liquid metal; it is defined that when the ADC value is greater than or equal to ADC1 and less than or equal to ADC2, the corresponding PD module is partially blocked by the liquid metal, and the front end of the current liquid metal is located within the projection of the PD unit in the microfluidic channel;

[0024] When completely blocked, the light received by the PD unit is mainly ambient light, so the ADC value is low, so ADC1 is generally set to 50; when not blocked, the PD unit can receive relatively complete LED light, so the ADC value is high, so ADC2 is generally set to 2000; and partially blocked is between the two, so as long as the ADC value is greater than or equal to ADC1 and less than or equal to ADC2, the partially blocked PD unit can be determined;

[0025] From the ADC values ​​of each PD unit, select the value that is greater than or equal to ADC1 and less than or equal to ADC2, and record it as ADC n The distance between the projection point of the corresponding PD unit center in the microfluidic channel and the starting point is recorded as PD n ;

[0026] Calculate the front position of the liquid metal in the microfluidic channel directly above the second groove:

[0027] Current liquid metal front position = PD n +a*ADC n *ADC n -b*ADC n +c;

[0028] Wherein, a, b, c are fitting coefficients; wherein, a, b, c are fitting coefficients determined by the width and height of the microfluidic channel and are treated as known constants in this application.

[0029] The difference between the target position of the liquid metal in the microfluidic channel directly above the second groove and the current front position of the liquid metal is used as the input of the PID algorithm. After proportional, integral and differential operations, the output speed of the liquid metal driving pump in the current state is obtained under given PID parameters, and the length of the liquid metal in the flow channel is changed.

[0030] Step 3: Since the liquid metal in the two microfluidic channels is connected to the feeder arm, the length of the liquid metal in the two microfluidic channels is changed through the second step, thereby changing the length of the feeder arm to achieve antenna polarization control;

[0031] Step 4: With a given Δt as the time interval, the above operations are executed repeatedly to finally realize the automatic control of the liquid metal reconstructed antenna.

[0032] The beneficial effects of the present invention are as follows: the present invention adopts a continuous reconstruction method to drive liquid metal, so that the antenna can realize the frequency-polarization reconfigurable function, and the polarization reconstruction direction can be continuously turned. By adopting an adaptive driving method, the liquid metal reconstructed antenna can automatically switch the polarization direction according to the program design. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of the structure of a reconfigurable antenna;

[0034] Figure 2 It is a schematic diagram of key structural layer parameters;

[0035] Figure 3 This is a schematic diagram of antenna polarization state data at 3.2GHz;

[0036] Figure 4 This is a schematic diagram of antenna polarization state data at 2.8 GHz;

[0037] Figure 5 Schematic diagram of S11 parameters in different polarization states at 2.8 GHz and 3.2 GHz;

[0038] Figure 6 The 2.8GHz antenna pattern working in linear polarization and circular polarization state;

[0039] Figure 7 Schematic diagram of the high-precision automatic driving solution for liquid metal. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0041] like Figure 1 As shown, a reconfigurable antenna based on liquid metal includes a patch layer 1, a first transparent substrate 2, a first foam layer 3, a first ground layer 4, a second transparent substrate 5, a second foam layer 6, a third transparent substrate 7 and a second ground layer 8 arranged in sequence from top to bottom;

[0042] A first groove is provided on the lower surface of the first foam layer 3, and an LED module 9 is embedded in the first groove; a second groove is provided on the upper surface of the second foam layer 6, and a PD module 10 is embedded in the second groove;

[0043] A microfluidic channel 11 is fixed on the upper surface of the second transparent substrate 5 . One end of the microfluidic channel is connected to a pump through a pipeline, and the other end is connected to a liquid metal container through a pipeline. The flow of the liquid metal is controlled by the pump.

[0044] The LED module 9 and the PD module 10 are respectively arranged above the first stratum 4 (coupling layer) (embedded in the first foam layer 3) and below the second transparent substrate 5 (embedded in the second foam layer 6) to monitor the flow of liquid metal. The light signal emitted by the LED module will be received by the PD, and the electrical signal output by the PD will also change as the flow state of the liquid metal changes.

[0045] The first transparent substrate and the second transparent substrate are both transparent plastic substrates, and the dielectric constant ε r =2.35, loss angle tanδ = 0.0005. Unlike conventional substrates, transparent substrates have high light transmittance, and the light signal emitted by the LED module can be transmitted to the PD module through the transparent substrate, thereby controlling the liquid metal.

[0046] The (multiple) microfluidic channel structure polarization is 3D printed and bonded to a transparent substrate through a double-layer adhesive sheet and a light-curing adhesive. The two ends of the microfluidic channel are connected to a PTFE tube, one end is connected to a pump, and the other end is connected to a liquid metal container, and the flow of the liquid metal is controlled by the pump.

[0047] The upper layer of the first layer (coupling layer) and the lower layer of the feeder 12 are (PMI) foam layer structures for embedding LED modules and PTFE tubes (for injecting and extracting liquid metal). The dielectric constant ε of the PMI foam layer r =1.06, loss cut angle tanδ =0.00028. In addition, the PMI foam layer can effectively increase the antenna bandwidth.

[0048] The first stratum (coupling layer) is a patterned copper layer, i.e., the grounding layer. Multiple concentric circular grooves with different radii are etched on the coupling layer. Based on the polarization periodicity of the T-shaped feeder, the feeder is extended into a fork-shaped antenna, and rectangular grooves are etched at the corresponding positions of the stratum. The rectangular grooves can prevent the stratum from obstructing the optical signal and increase the antenna bandwidth. In addition, since the coupled feeder structure has obvious backscattering, a stratum structure is added under the antenna structure to reduce backscattering and improve the antenna directivity.

[0049] When the antenna is working, one of the annular grooves is reserved as a coupling groove, and the other annular grooves are filled with gallium indium liquid metal (EGaIn). The diameter of the reserved coupling groove is d s2 Under the second transparent substrate is a T-type feeder, and the lengths of the two arms ls1 and ls2 of the T-type feeder can be adjusted by liquid metal. The relevant parameters of the top copper sheet, coupling layer and feeder are as follows: Figure 2 shown.

[0050] By adjusting the length of the double arms ls1 and ls2, multiple polarization states can be achieved. When one arm of the feed line is much shorter than the other arm, the feed line and the circular groove will form two intersections. Since the current on the feed line moves in two orthogonal directions, x and y, two orthogonal modes will be excited. When the length of the double arms ls1 and ls2 is adjusted, the phase of the current in the two directions will change. When the current amplitude at the intersection is the same and the phase difference is 90°, the antenna will form a circular polarization working mode; when the current phase at the intersection is the same, the antenna will form a linear polarization working mode.

[0051] When the diameter of the dielectric substrate d s1 =43mm, coupling slot diameter d s2 =14mm, the antenna works at 3.2GHz. The circular polarization at 2.44GHz and the linear polarization at five angles are as follows Figure 3 As shown. By adjusting the length of ls1 and ls2, right-hand circular polarization (RHCP), left-hand circular polarization (LHCP) and various linear polarization (LP) states can be obtained. As the feed line length changes, the linear polarization direction can be continuously changed.

[0052] When choosing the coupling slot diameter d s2 =12mm, the operating frequency of the antenna changes from 3.2GHz to 2.8GHz. In this state, changing the lengths of the two arms of the feeder, ls1 and ls2, can also achieve the function of polarization reconfiguration. The polarization state at 2.8GHz is as follows Figure 4 By adjusting the lengths of ls1 and ls2, right-hand circular polarization (RHCP), left-hand circular polarization (LHCP) and five linear polarization (LP) states can be obtained, and the linear polarization direction can be continuously changed.

[0053] When the coupling slot diameter d s2 When the length of the two arms of the feeder remains unchanged, changing the length will not affect the working frequency of the antenna. Figure 5 As shown. That is, the polarization reconfiguration function and frequency reconfiguration function of the antenna can be controlled independently. The linear polarization and circular polarization antenna radiation patterns working at 2.8GHz are shown in Figure 6 The antenna has good cross-polarization difference.

[0054] like Figure 7 As shown, a polarization reconstruction method of a reconfigurable antenna based on liquid metal includes the following steps:

[0055] Step 1: LED-PD module drive and data output. Different from the traditional air pressure drive method, the PD module and LED module are embedded in the multi-layer structure of the antenna, and both are driven by the STM32 microcontroller. The LED module emits a uniform light signal. When the liquid metal flows to the target position, the light signal at the target position will be blocked, and the corresponding PD unit cannot receive the light signal. The PD module is composed of multiple PD units, each of which outputs corresponding voltage data based on the collected light signal. The voltage data is converted into ADC data through STM32 and MATLAB data processing. According to the ADC array output by each PD unit, the current running position of the front end of the liquid metal can be obtained, thereby realizing real-time position monitoring of the liquid metal.

[0056] Step 2: Process the ADC array corresponding to the current liquid metal flow state and calculate the front position of the liquid metal. The calculation formula is shown below. This formula is fitted by the experimental results of liquid metal in a flow channel with a width of 2mm and a height of 0.5mm. This formula needs to be adjusted according to the different reconstructed antenna structures.

[0057] Current liquid metal position = PD n +0.0005*ADC n *ADC n -0.03*ADC n +0.23.

[0058] The difference between the antenna reconstruction position and the current running position of the liquid metal is used as the input of the PID algorithm. After proportional, integral and differential operations, the output speed of the liquid metal driving pump in the current state can be obtained under appropriate PID parameters. In the present invention, the PID control parameters are as follows: K p =8,K i =0.01,K d =1.

[0059] Step 3: Since the liquid metal in the two microfluidic channels is connected to the feeder arm, the length of the liquid metal in the two microfluidic channels is changed through the second step, thereby changing the length of the feeder arm to achieve antenna polarization control;

[0060] Step 4: Execute the above operation repeatedly with a time interval of 0.5s, and finally realize high-precision automatic control of liquid metal reconstructed antenna, with control accuracy up to 0.5mm and polarization rotation angle accuracy up to 5°. The design of high-precision driving method also makes continuous reconstruction of liquid metal possible.

[0061] The above is a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A reconfigurable antenna based on liquid metal, characterized in that: It comprises a patch layer (1), a first transparent substrate (2), a first foam layer (3), a first ground layer (4), a second transparent substrate (5), a second foam layer (6), a third transparent substrate (7) and a second ground layer (8) which are stacked in sequence from top to bottom; The lower surface of the first foam layer (3) is provided with a first groove, in which an LED module (9) is embedded; the upper surface of the second foam layer (6) is provided with a second groove, in which a PD module (10) is embedded; A microfluidic channel (11) is fixed on the upper surface of the second transparent substrate (5); one end of the microfluidic channel is connected to a pump via a pipeline, and the other end is connected to a liquid metal container via a pipeline, and the flow of the liquid metal is controlled by the pump.

2. The liquid metal-based reconfigurable antenna according to claim 1, characterized in that: The profile of the first groove is consistent with the profile of the LED module (9).

3. The liquid metal-based reconfigurable antenna according to claim 1, characterized in that: The profile of the second groove is consistent with the profile of the PD module (10).

4. The liquid metal-based reconfigurable antenna according to claim 1, characterized in that: The pipeline is a PTFE tube.

5. The liquid metal-based reconfigurable antenna according to claim 1, characterized in that: A feeder line (12) is also provided between the first stratum (4) and the second transparent substrate (5).

6. The liquid metal-based reconfigurable antenna according to claim 1, characterized in that: The PD module (10) is used to monitor the flow of liquid metal. The light signal emitted by the LED module (9) will be received by the PD module (10). As the flow state of the liquid metal changes, the electrical signal output by the PD module (10) will also change.

7. The liquid metal-based reconfigurable antenna according to claim 6, characterized in that: The first stratum (4) is a coupling layer, which is a patterned copper layer, and a plurality of concentric circular grooves with different radii are etched on the coupling layer; the energy on the feeder line can be coupled to the patch layer (1) through the circular grooves on the coupling layer to generate radiation; There are two microfluidic channels (11), and the feeder (12) is a T-shaped feeder, which includes three feeder arms, a first end of the first feeder arm is connected to the first microfluidic channel, a second end of the first feeder arm is connected to the first end of the second feeder arm, and a second end of the second feeder arm is connected to the second microfluidic channel; The first feeder arm and the second feeder arm are located on the same straight line, the first end of the third feeder arm of the T-shaped feeder is connected to the second end of the first feeder arm, and the second end of the third feeder arm is used for feeding power; and the third feeder arm and the first feeder arm are perpendicular to each other; The coupling layer is also provided with two rectangular grooves, wherein the first rectangular groove is located directly above the first microfluidic channel, and the second rectangular groove is located directly above the second microfluidic channel; and is used to allow the light signal emitted by the LED module (9) in the first groove to pass through the rectangular grooves and irradiate the first microfluidic channel and the second microfluidic channel; The number of the second grooves is 2, the first second groove corresponds to the first microfluidic channel and is located directly below the first microfluidic channel, and the other second groove corresponds to the second microfluidic channel and is located directly below the second microfluidic channel; The PD module in each second groove is composed of a plurality of PD units, and each PD unit outputs corresponding voltage data according to the light signal collected passing through the corresponding microfluidic channel, thereby detecting the position of the liquid metal in the microfluidic channel; For any microfluidic channel, take the connection point between the microfluidic channel and the T-type feeder as the starting point, project the centers of each PD unit in the second groove below the microfluidic channel onto the microfluidic channel, and measure the distance between the projection point position of each PD unit center and the starting point.

8. A polarization reconfiguration method for a liquid metal-based reconfigurable antenna, based on the reconfigurable antenna according to any one of claims 1 to 7, characterized in that: The following steps are involved: The first step: connecting the LED module (9) and the PD modules (10) in the two second grooves to the STM32 single chip computer; Driven by the STM32 single chip microcomputer, the LED module (9) emits a uniform light signal, and when the liquid metal flows to the target position, the light signal at the target position will be blocked; Step 2: for any PD module (10) in the second groove, each PD unit contained therein outputs corresponding voltage data according to the collected optical signal; The voltage data is converted into ADC value through ADC, forming an ADC array and transmitted to the STM32 microcontroller; First, two thresholds are set, denoted as ADC1 and ADC2, where ADC1 is smaller than ADC2; It is defined that when the ADC value is less than ADC1, the corresponding PD unit is completely blocked by the liquid metal, and when the ADC value is greater than ADC2, the corresponding PD module is not blocked by the liquid metal; it is defined that when the ADC value is greater than or equal to ADC1 and less than or equal to ADC2, the corresponding PD module is partially blocked by the liquid metal, and the front end of the current liquid metal is located within the projection of the PD unit in the microfluidic channel; From the ADC values ​​of each PD unit, select the value that is greater than or equal to ADC1 and less than or equal to ADC2, and record it as ADC n The distance between the projection point of the corresponding PD unit center in the microfluidic channel and the starting point is recorded as PD n ; Calculate the front position of the liquid metal in the microfluidic channel directly above the second groove: Current liquid metal front position = PD n +a*ADC n *ADC n -b*ADC n +c; Among them, a, b, c are fitting coefficients; The difference between the target position of the liquid metal in the microfluidic channel directly above the second groove and the current front position of the liquid metal is used as the input of the PID algorithm. After proportional, integral and differential operations, the output speed of the liquid metal driving pump in the current state is obtained under given PID parameters, and the length of the liquid metal in the flow channel is changed. Step 3: Since the liquid metal in the two microfluidic channels is connected to the feeder arm, the length of the liquid metal in the two microfluidic channels is changed through the second step, thereby changing the length of the feeder arm to achieve antenna polarization control; Step 4: With a given Δt as the time interval, the above operations are executed repeatedly to finally realize the automatic control of the liquid metal reconstructed antenna.

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