Ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube control

Abstract

The present invention provides an ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube regulation, which is composed of metasurface units (hereinafter referred to as "units") using only one PIN diode. A PIN diode is integrated into the microstrip transmission circuit on the back of the unit, so that the unit has the ultra-wideband amplitude-phase independent adjustable characteristics. Continuous control of the reflection amplitude and 1-bit control of the reflection phase can be achieved by continuously changing the voltage across the PIN diode. Different amplitude and phase controls are performed on the units in the reflection array to achieve functions such as low scattering, beam deflection, beam focusing, and target simulation. The present invention has the advantages of ultra-large bandwidth, independent and adjustable electromagnetic reflection amplitude and phase, low profile, low manufacturing cost, and easy system integration, and has important application prospects in the field of radar electromagnetic target characteristic simulation.

Description

Technical Field

[0001] The present invention relates to a new type of ultra-wideband amplitude-phase-independent reconfigurable reflective electromagnetic metasurface based on a single PIN diode control technology, belonging to the field of new type artificial electromagnetic materials. Background Art

[0002] New artificial electromagnetic materials, also known as electromagnetic metamaterials, are artificial synthetic materials with unique electromagnetic properties formed by arranging artificial unit structures in a specific way. These materials exhibit electromagnetic properties that are not found in natural materials, giving rise to many novel physical phenomena. However, traditional electromagnetic metamaterials are large in size, expensive to manufacture, and difficult to carry because they arrange artificial units in three-dimensional space. To overcome these limitations, an innovative two-dimensional planar artificial electromagnetic material, the electromagnetic metasurface, has been developed. This metasurface is composed of sub-wavelength-sized units arranged according to a specific rule to form a periodic or quasi-periodic two-dimensional surface structure. Electromagnetic metasurfaces have become a hot topic of research due to their small size, low profile, low cost, easy conformality, and excellent electromagnetic wave control capabilities. Early research on electromagnetic metasurfaces focused on passive metasurfaces. Although they have many unique electromagnetic properties, they also have many limitations, such as narrow bandwidth, linear response, and inability to be controlled in real time.

[0003] Compared with traditional passive metasurfaces, electromagnetic metasurfaces loaded with active devices on passive metal structures have the huge advantage of being able to dynamically control electromagnetic waves, and have broadband electromagnetic functions and characteristics that cannot be achieved by traditional passive methods.

[0004] The electromagnetic metasurface involved in the present invention is a new type of active electromagnetic metasurface. The concept of programmable metasurface based on digital active components to manipulate scattered electromagnetic waves was proposed in 2014, and a 180-degree reflection phase difference was achieved by switching the PIN diodes on the metasurface unit. After that, more and more programmable metasurfaces were proposed and used to achieve phase modulation and amplitude modulation, all of which achieved good results. However, to date, the relative working bandwidth of most active metasurfaces that can achieve independent adjustable amplitude and phase does not exceed 80%, and the number of active devices used in the metasurface unit is not less than 2. Therefore, using fewer active devices to achieve ultra-wideband electromagnetic functions with independent adjustable amplitude and phase is a problem that needs to be solved urgently.

[0005] Combined with the ultra-wideband transmission capability of the microstrip line, the ultra-wideband unit integrated with a single PIN diode provides a solution for realizing the independent adjustable amplitude and phase of ultra-wideband. By using a tightly coupled antenna to receive and transmit ultra-wideband electromagnetic waves, combined with the bottom microstrip circuit, the scattering control of ultra-wideband electromagnetic waves can be achieved. Summary of the invention

[0006] Technical problem: The ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube regulation of the present invention overcomes the problems of high power consumption, high cost and poor performance of traditional active electromagnetic metasurfaces. In traditional active electromagnetic metasurfaces, in order to realize the function of independent adjustable amplitude and phase, no less than 2 active devices will be integrated in the metasurface unit, which not only increases the manufacturing cost, but also increases the working power consumption of the metasurface. In addition, the metal structures in traditional metasurface units are mostly dispersive structures, which are very unfavorable for realizing electromagnetic functions with a relative bandwidth greater than 80%. The new reflective electromagnetic metasurface of the present invention realizes fewer active devices, newer structural design and better ultra-wideband electromagnetic performance.

[0007] Technical solution: The present invention discloses an ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube regulation, which is composed of a plurality of units. The units include three metal layers, the first metal layer is welded with a tightly coupled antenna array, the second metal layer is a ground layer, and the third metal layer is a microstrip circuit layer. A first metal via is arranged between the first metal layer and the third metal layer, and a second metal via is arranged between the second metal layer and the third metal layer; the microstrip circuit includes a PIN diode, a microstrip line and a DC bias circuit, and the PIN diode is integrated between the second metal via and the microstrip line; the cathode of the PIN diode is grounded through the second metal via, and the anode is connected to the feeding port of the tightly coupled antenna through the first metal via; the DC bias circuit loads a DC voltage to the anode of the PIN diode, and the on-off of the PIN diode is controlled by adjusting the DC voltage.

[0008] Preferably, the units of the outermost circle of the metasurface integrate a 50Ω resistor between the second metal via and the microstrip line, and extend the dipole arms of the tightly coupled antenna of the units of the outermost circle to form a dummy element.

[0009] Preferably, the tightly coupled antenna is a vertical antenna, the upper part of which is a frequency selective surface, the lower part is a microstrip balun, a fan-shaped branch is arranged at the end of the microstrip balun, and the bottom end of the microstrip balun is connected to the microstrip circuit through the first metal through hole.

[0010] Preferably, the DC bias circuit is a "T"-shaped circuit composed of an inductor, a capacitor, and a resistor, the inductor has an inductance of 82nH, the capacitor has a capacitance of 100pF, and the resistor has a resistance of 10Ω.

[0011] Preferably, in the unit, the first metal layer is located on the upper surface of the upper dielectric substrate, the second metal layer is located between the upper dielectric substrate and the middle adhesive layer, and the third metal layer is located on the lower surface of the lower dielectric substrate; the dielectric constant of the upper dielectric substrate is 4.4, the thickness is 3.2 mm, and the loss tangent is 0.0033; the dielectric constant of the middle adhesive layer is 3.5, the thickness is 0.1 mm, and the loss tangent is 0.0042; the dielectric constant of the lower dielectric substrate is 2.65, the thickness is 0.9 mm, and the loss tangent is 0.0015.

[0012] Preferably, the tightly coupled antenna is a single-layer printed circuit board, the dielectric substrate of which has a dielectric constant of 4.4, a loss tangent of 0.0033, and a thickness of 3.2 mm.

[0013] Preferably, the line width of the microstrip line in the microstrip circuit is the line width corresponding to the characteristic impedance of 50 ohms.

[0014] The present invention also provides an electromagnetic wave control method based on the above-mentioned metasurface, comprising the following steps: after the tightly coupled antenna converts the spatial electromagnetic wave into a guided electromagnetic wave, the guided electromagnetic wave is conducted to the microstrip circuit through a first metal through hole; the DC bias voltage is adjusted within the range of 0V-1.3V to control the state of the PIN diode to achieve independent control of the amplitude and phase of the guided electromagnetic wave; and the guided electromagnetic wave is then emitted into space by the tightly coupled antenna through the first metal through hole.

[0015] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0016] 1. The present invention integrates a PIN diode in each unit so that the new electromagnetic metasurface has the advantages of low profile, low manufacturing cost, independent amplitude and phase control, and easy system integration, and has important application prospects in the field of radar electromagnetic target characteristic simulation.

[0017] 2. The present invention designs the units in the outer circle of the metasurface as dummy elements to simulate a periodic environment and provide a good matching environment for the internal units, thereby better realizing the electromagnetic performance of ultra-wideband reflection amplitude and reflection phase that are independently adjustable.

[0018] 3. The present invention has the characteristics of low power consumption, large working bandwidth and multiple electromagnetic functions. Only one PIN diode is integrated in each unit of the electromagnetic metasurface used in the present invention to achieve ultra-wideband electromagnetic performance with independent and reconfigurable reflection amplitude and reflection phase.

[0019] 4. The present invention is easy to process and realize. The electromagnetic super surface used in the present invention has a mature low-cost processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a schematic diagram of the structure of the present invention, wherein (a) and (b) are schematic diagrams of the front and back sides of a model of an ultra-wideband amplitude-phase independent reconfigurable new reflective electromagnetic metasurface based on a single PIN diode control technology of the present invention, respectively.

[0021] Figure 2 This is a magnified image of a single circuit on the back side of the electromagnetic metasurface.

[0022] Figure 3 It is an oblique view of the electromagnetic supersurface unit of the present invention.

[0023] Figure 4 It is the bottom circuit diagram of the electromagnetic metasurface unit of the present invention.

[0024] Figure 5 It is a simulation result diagram of 1-bit phase switching of the electromagnetic metasurface unit of the present invention, wherein (a) shows the reflection amplitude of the unit when the PIN diode is in the ON state (1.3V) and the OFF state (0V), and (b) shows the reflection phase difference of the unit corresponding to the PIN diode ON state and OFF state.

[0025] Figure 6 It is a simulation result diagram of the corresponding reflection amplitude and reflection phase when the electromagnetic metasurface unit of the present invention is continuously adjusted within the bias voltage range of 0V-0.58V, wherein (a) is the corresponding reflection amplitude change diagram, and (b) is the corresponding reflection phase change diagram.

[0026] Figure 7 It is a simulation result diagram of the reflection amplitude and reflection phase corresponding to the electromagnetic metasurface unit of the present invention when the bias voltage is continuously adjusted in the range of 0.63V-1.3V, wherein (a) is the corresponding reflection amplitude change diagram, and (b) is the corresponding reflection phase change diagram.

[0027] Figure 8 This is a diagram of the reflection amplitude simulation results of the electromagnetic metasurface unit of the present invention under the condition of a bias voltage of 0.6V. DETAILED DESCRIPTION

[0028] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0029] In this embodiment, the new reflective electromagnetic metasurface uses a tightly coupled antenna to receive and radiate space waves. The working process is as follows: after the tightly coupled antenna converts the space wave into a guided electromagnetic wave (hereinafter referred to as "guided wave"), the guided wave is transmitted to the back microstrip circuit through the first metal via for amplitude and phase manipulation. After that, the guided electromagnetic wave is transmitted into space by the tightly coupled antenna through the first metal via.

[0030] The electromagnetic super surface of the present invention is composed of N In this example, 10 The electromagnetic metasurface is composed of 10 metasurface units. In each internal unit, only one PIN diode 6 is used to control whether the microstrip line is grounded to regulate the electromagnetic performance of the guided wave. In order to provide a good matching environment for the internal units, the outermost circle is designed as a dummy element to simulate a periodic environment. The new reflective electromagnetic metasurface contains a total of eleven printed circuit boards, namely an array base plate 1 with integrated PIN diodes and ten tightly coupled antenna vertical plates 2. By regulating the PIN diodes of the units, the function of independent adjustable amplitude and phase of ultra-wideband is realized.

[0031] The array base plate 1 of the PIN diode is a three-layer printed circuit board, which includes two layers of dielectric substrates and an intermediate bonding layer. The dielectric constant of the upper dielectric substrate is 4.4, and the loss tangent is 0.0033. The dielectric constant of the lower dielectric substrate is 2.65, and the loss tangent is 0.0015. The dielectric constant of the intermediate bonding layer is 3.5, and the loss tangent is 0.0042. The thickness of the upper dielectric layer is 3.2mm, the thickness of the lower dielectric layer is 0.9mm, and the thickness of the bonding layer is 0.1mm. The tightly coupled antenna stand 2 is a single-layer printed circuit board, and the dielectric constant of its dielectric substrate is 4.4, the loss tangent is 0.0033, and the thickness is 3.2mm. The metal of the eleven printed circuit boards is copper, the thickness of copper is 0.018mm, and anti-oxidation treatment has been done.

[0032] In this embodiment, only one PIN diode 6 is used to control the grounding of the microstrip line, and a broadband DC bias circuit 5 is used to feed the PIN diode to control the voltage at both ends of the PIN diode to continuously change, thereby realizing independent adjustment of the reflection amplitude and reflection phase of the electromagnetic wave.

[0033] A 50-ohm resistor 4 is integrated between the metallized via and the microstrip line, and the dipole arm 3 of the tightly coupled antenna in the dummy element is extended.

[0034] The tightly coupled antenna is a vertical antenna soldered on the bottom circuit dielectric board, such as Figure 3As shown in the figure, the upper part of the antenna is a frequency selective surface, which is used to improve the return loss of the antenna to achieve ultra-large bandwidth. The antenna is coupled and fed by a microstrip balun, and the end of the balun is combined with a fan-shaped branch to achieve good impedance matching. The bottom end of the antenna balun is connected to the microstrip circuit on the back through a metal through hole, as shown in the figure. Figure 4 shown.

[0035] The microstrip circuit on the back is mainly composed of a microstrip line with an integrated PIN diode and a "T"-shaped broadband DC bias circuit. The cathode of the PIN diode is connected to the second metal via and directly grounded. The anode of the PIN diode is connected to the microstrip line. The DC voltage is loaded onto the microstrip line, that is, the anode of the PIN diode, through a bias circuit that integrates inductance, capacitance, and resistance. Among them, the inductance value is 82nH, the capacitance value is 100pF, and the resistance value is 10Ω. The line width of the microstrip line is the line width corresponding to the characteristic impedance of 50 ohms. When the DC bias voltage changes continuously in the range of 0V-1.3V, the state of the PIN diode can be continuously adjusted to achieve independent regulation of the amplitude and phase of the guided wave.

[0036] In microwave transmission line theory, the distance between the load The reflection coefficient solution formula at is as follows:

[0037] (1)

[0038] for The input impedance at can be calculated by the following formula:

[0039] (2)

[0040] is the phase shift constant; is the load impedance; Indicates the characteristic impedance of the transmission line. In an ideal situation, when the PIN diode is turned on, that is, one end of the microstrip line with the PIN diode is directly grounded, is approximately 0. =0 is substituted into (2) to obtain After the input impedance at the input point is substituted into formula (1), we can calculate The reflection coefficient at is as follows:

[0041] (3)

[0042] When the PIN diode is turned off, one end of the microstrip line is open. Very big, will Approximately infinite, after substituting it into (2) to calculate the input impedance, and then substituting it into (1) to calculate the reflection coefficient, we get the following formula:

[0043] (4)

[0044] Combining equation (3) with equation (4), we get:

[0045] (5)

[0046] That is, when the PIN diode is turned on and off, the reflection coefficient at the same position of the microstrip line has a reflection phase difference of , it can be observed that the phase difference does not contain the frequency term, which means that the working bandwidth of 1-bit phase regulation using this theory depends on the working frequency range of the PIN diode and the working frequency of other structures in the unit, providing a good basis for realizing ultra-wideband 1-bit phase modulation. Of course, in the actual circuit, the PIN diode is not an ideal short circuit when it is turned on, and there will be an internal resistance of about several ohms; the PIN diode is not an ideal open circuit when it is turned off, and it can be equivalent to a large resistance of several thousand ohms, and the characteristics of the actual PIN diode are dispersive. This means that in the actual results, the 1-bit phase difference is not an ideal phase difference. , but the phase difference will vary slightly at different operating frequencies, but generally it is around 180°.

[0047] Combined with the above theory of using PIN diode to realize 1-bit phase modulation, the simulation model of PIN diode provided by the manufacturer is brought into the overall unit for overall simulation. The simulation results of the unit are obtained, such as Figure 5 shown. Figure 5 (a) shows the reflection amplitude of the whole unit when 0V and 1.3V are applied to both ends of the PIN diode. It can be observed that the change of the two amplitude curves in the range of 0.5GHz-1.5GHz does not exceed 0.5dB. At the same time, when the PIN diode is turned off and on, the reflection amplitude difference of the corresponding unit is as follows: Figure 5 As shown in (b), in the frequency range of 0.5 GHz to 1.5 GHz, the phase difference is within 180°±30°.

[0048] As mentioned above, when the PIN diode is turned on, it can be equivalent to a resistance of several ohms, that is, the voltage loaded at both ends is 1.3V; when it is turned off, it can be equivalent to a resistance of several thousand ohms, that is, the voltage loaded at both ends is 0V. When the voltage increases continuously from 0V to 1.3V, the resistance characteristic of the PIN diode will also decrease continuously from several thousand ohms to several ohms. In the present invention, the line width of the microstrip line is 50 ohms, so when the internal resistance of the PIN diode is adjusted to 50 ohms, at this time, it can be known from formula (2), = , substituting into formula (1) we can get This characteristic can be used to achieve continuous adjustment of the guided wave reflection amplitude.

[0049] When the voltage across the PIN diode changes continuously from 0V to 0.58V, take part of the intermediate voltage, the simulation results of the corresponding overall unit are as follows Figure 6 shown. Figure 6 (a) shows that the reflection amplitude has a control range of more than 7dB in the range of 0.5GHz-1.5GHz. At the same time, the corresponding reflection phase is as follows Figure 6 As shown in (b), there is an oscillation of less than 20°. Similarly, when the voltage across the PIN diode changes continuously from 0.63V to 1.3V, the simulation results of the corresponding overall unit are as follows: Figure 7 shown. Figure 7 (a) shows that the reflection amplitude has a control range of more than 7dB in the range of 0.5GHz-1.5GHz. At the same time, the corresponding reflection phase is as follows Figure 7 As shown in (b), there is an oscillation of less than 20° and Figure 6 The phase shown in (b) has a phase difference of 180°±30°.

[0050] When the voltage across the PIN diode is 0.6V, the internal resistance of the PIN diode almost matches the characteristic impedance of the microstrip line. At this time, the corresponding reflection amplitude is the lowest, and the absorption of more than 13dB can be met in the range of 0.5GHz-1.5GHz. Figure 8 shown.

[0051] The present invention provides a simple design idea and method based on the model theory of only using a PIN diode combined with a microwave transmission line. It only needs to change the voltage value at both ends of the PIN diode to change the equivalent internal resistance value of the PIN diode, so as to construct the desired reflection amplitude and reflection phase.

[0052] The present invention has the advantages of ultra-large bandwidth, independently adjustable electromagnetic reflection amplitude and phase, low profile, low manufacturing cost, easy system integration, etc., and can be used to achieve functions such as low scattering, beam deflection, beam focusing, and target simulation.

[0053] It should be noted that the above is only a preferred implementation of the present invention in the P band and the L band, and the same structure can be applied to higher frequency bands by scaling the size, such as the C band, the X band, the Ku band, etc. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube control, consisting of several units, characterized in that: The unit includes three metal layers, the first metal layer is welded with a tightly coupled antenna array, the second metal layer is a ground layer, and the third metal layer is a microstrip circuit layer. A first metal via is arranged between the first metal layer and the third metal layer, and a second metal via is arranged between the second metal layer and the third metal layer. The tightly coupled antenna in the tightly coupled antenna array is a vertical antenna, the upper part of which is a frequency selective surface, and the lower part is a microstrip balun. A fan-shaped matching branch is arranged at the end of the microstrip balun, and the bottom end of the microstrip balun is connected to the microstrip circuit through the first metal through hole. The microstrip circuit includes a PIN diode, a microstrip line and a DC bias circuit, and the PIN diode is integrated between the second metal via and the microstrip line. The cathode of the PIN diode is grounded through the second metal via, and the anode is connected to the feeding port of the tightly coupled antenna through the first metal via. The DC bias circuit loads a DC voltage to the anode of the PIN diode, and the on-off of the PIN diode is controlled by adjusting the DC voltage.

2. According to claim 1, an ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube control is characterized in that: The outermost circle unit of the metasurface integrates a 50Ω resistor between the second metal via and the microstrip line, and extends the dipole arm of the tightly coupled antenna of the outermost circle unit to form a dummy element.

3. According to claim 1, an ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube control is characterized in that: The DC bias circuit is a "T" type circuit composed of an inductor, a capacitor, and a resistor, wherein the inductor has an inductance of 82nH, the capacitor has a capacitance of 100pF, and the resistor has a resistance of 10Ω.

4. According to claim 1, an ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube control is characterized in that: In the unit, the first metal layer is located on the upper surface of the upper dielectric substrate, the second metal layer is located between the upper dielectric substrate and the middle adhesive layer, and the third metal layer is located on the lower surface of the lower dielectric substrate; the upper dielectric substrate has a dielectric constant of 4.4, a thickness of 3.2 mm, and a loss tangent of 0.0033; the middle adhesive layer has a dielectric constant of 3.5, a thickness of 0.1 mm, and a loss tangent of 0.0042; the lower dielectric substrate has a dielectric constant of 2.65, a thickness of 0.9 mm, and a loss tangent of 0.0015.

5. The ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube control according to claim 1, characterized in that: The tightly coupled antenna is a single-layer printed circuit board, the dielectric constant of the dielectric substrate of which is 4.4, the loss tangent is 0.0033, and the thickness is 3.2 mm.

6. The ultra-wideband amplitude-phase independent reconfigurable metasurface based on single PIN tube control according to claim 1, characterized in that: The line width of the microstrip line in the microstrip circuit is the line width corresponding to the characteristic impedance of 50 ohms.

7. The electromagnetic wave control method of the metasurface according to any one of claims 1 to 6, characterized in that: The invention comprises the following steps: after the tightly coupled antenna converts the space electromagnetic wave into the guided electromagnetic wave, the guided electromagnetic wave is conducted to the microstrip circuit through the first metal through hole; the DC bias voltage is adjusted within the range of 0V-1.3V to adjust the state of the PIN diode to realize independent regulation of the amplitude and phase of the guided electromagnetic wave; and the guided electromagnetic wave is emitted into the space by the tightly coupled antenna through the first metal through hole.

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