Metasurface electronic tag based on time modulation

Abstract

The invention relates to a metasurface electronic tag based on time modulation. The metasurface electronic tag is composed of a modulation waveform controller and a metasurface. The modulation waveform controller is used for generating a modulation voltage waveform input into the metasurface so as to change coding information of the electronic tag; the metasurface is composed of a structured metal surface, a bottom layer metal ground and a low-loss intermediate medium. The structured metal surface is composed of metasurface units, each metasurface unit comprises a metal frame, a circular metal patch and four semicircular metal patches, the circular metal patch is located in the center of the metasurface unit, and the circular metal patch and the four semicircular metal patches are connected through variable capacitance diodes. The structure has a 90-degree rotational symmetry characteristic and generates the same response to two arbitrary orthogonal wave energy, and the four discrete parts are respectively connected by variable capacitance diodes, so that effective tuning under arbitrary polarized waves can be realized.

Description

Technical Field

[0001] The invention relates to an electronic tag identification technology, and in particular to a super-surface electronic tag system based on time modulation. Background Art

[0002] Radio Frequency Identification (RFID) is a contactless automatic identification technology that does not require human intervention. In RFID technology, tags have the advantages of long life, small size, and large capacity. At present, chipless tags based on frequency domain characteristics add the encoding information of the resonant circuit to the ultra-wideband spectrum characteristics on the main transmission line by designing the surface structure of the tag. It has the advantages of being printable and low cost, and has been widely used in different fields.

[0003] However, the current chipless tag coding information based on frequency domain characteristics is determined by its surface structure, and the coding information of the tag cannot be changed through subsequent adjustments; at the same time, in order to achieve larger capacity coding, a larger spectrum bandwidth is required. Summary of the invention

[0004] In view of the shortcomings of the current electronic tag technology, the present invention aims to propose a high-capacity, re-encodeable, time-modulated metasurface electronic tag, which changes the coding information of the tag by changing the modulation waveform.

[0005] The technical solution for achieving the purpose of the present invention is: a metasurface electronic tag based on time modulation, including a modulation waveform controller and a metasurface; the modulation waveform controller is used to generate a modulation waveform; the metasurface is composed of a structured metal surface, an underlying metal ground and a low-loss intermediate medium, and the structured metal surface and the underlying metal ground are respectively arranged on the upper and lower surfaces of the intermediate medium; the output port of the modulation waveform controller is connected to any side of the metasurface array structure, and the frequency offset of the electromagnetic wave incident on the metasurface is generated by designing the modulation waveform output by the modulation waveform controller, and the encoding of the electronic tag is realized by using the frequency offset value.

[0006] Compared with the prior art, the present invention has the following significant advantages:

[0007] (1) The electronic tag based on the time-modulated metasurface of the present invention has a structure characteristic that the all-metal backplane of the metasurface is grounded, and the echo frequency conversion efficiency can reach 100%. The identification distance of the electronic tag is longer, and it can be applied to a wider range of applications.

[0008] (2) Changing the modulation voltage waveform can change the information of the electronic tag itself, realizing the programmable feature of the electronic tag information;

[0009] (3) The coding capacity of the electronic tag can be further increased through multiple transmissions and multiple receptions, and can theoretically reach any value, enabling larger capacity coding. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Schematic diagram of a metasurface tag unit using time modulation.

[0011] Figure 2 Schematic diagram of structured metal surface and metal cylinder.

[0012] Figure 3 It is a three-view image of a metasurface tag based on time modulation.

[0013] Figure 4 Schematic diagram of a metasurface array consisting of 10×10 metasurface units.

[0014] Figure 5 Schematic diagram of the changes in reflection amplitude and phase curves of a metasurface tag based on time modulation under different capacitances.

[0015] Figure 6 It is the normalized spectrum power distribution diagram of the echo of the metasurface tag under the 200kHz modulated sawtooth waveform. DETAILED DESCRIPTION

[0016] The present invention relates to an electronic tag based on a time-modulated metasurface, wherein the metasurface electronic tag is composed of a modulation waveform controller and a metasurface. The modulation waveform controller is used to generate a modulation voltage waveform input to the metasurface, so as to change the coding information of the electronic tag. The metasurface is composed of a structured metal surface, an underlying metal ground and a low-loss intermediate medium. The structured metal surface is composed of a metasurface unit, each of which includes a metal frame, a circular metal patch and four semicircular metal patches, the circular metal patch is located at the center of the metasurface unit, and the circular metal patch and the four semicircular metal patches are connected by a varactor diode. The structure has a 90° rotational symmetry characteristic, can produce the same response to two arbitrary orthogonal waves, and the four discrete parts are respectively connected by varactor diodes, which can realize effective tuning under arbitrary polarization waves. Under such a surface design, a 360° phase difference can be achieved within a wide frequency range of 3GHz to 6GHz, and the frequency conversion efficiency can reach 100%. The metasurface changes the echo frequency by designing a modulation waveform generated by the controller; the offset frequency numerical coding method can make the capacity of the electronic tag reach 3 bits. Theoretically, the coding capacity can reach (3×n) bits through n transmissions and receptions.

[0017] A controller capable of generating a modulation waveform and a metasurface operating at a broadband and fully polarized microwave frequency and capable of changing its electromagnetic properties by changing the modulation voltage waveform are used as electronic tags.

[0018] The waveform modulation controller can generate corresponding modulation waveforms according to requirements; the metasurface is composed of a structured metal surface, a bottom metal ground and a low-loss intermediate medium. The output port of the waveform modulation controller is connected to one side of the metasurface, and a specific frequency offset is generated for the electromagnetic wave incident on the metasurface by designing the modulation waveform output by the controller, and the encoding of the electronic tag is realized by using the frequency offset value.

[0019] The metasurface is an array structure composed of N×N metasurface units, each of which includes a metal frame with a width of 0.3mm, a circular metal patch with a radius of 3mm, and four semicircular metal patches with a radius of 2.6mm. The circular metal patch is located at the center of the metasurface unit. The circular metal patch and the four semicircular metal patches form a 90° rotationally symmetrical metal pattern on the unit surface. Four identical varactors are symmetrically embedded in the four reserved 0.6mm gaps of the top metal pattern, so that the middle circular metal patch is connected to the four surrounding semicircular metal patches. Considering that the four varactors require external DC bias, a metal through-hole is set in the center of the metasurface unit to connect the central square patch and the metal ground. The metal through-hole is a metal cylinder with a radius of 0.2mm that is co-centered with the central circular metal patch. Different voltages result in different RLC parameters of the four varactors. When the modulation voltage waveform causes the reflection phase of the metasurface to continuously and linearly change Tm within a modulation period, the incident frequency f i will effectively be converted upon reflection into a new frequency component f r , resulting in a frequency shift Δf = f r -f i By designing the modulation waveform output by the controller in advance, the size of the echo frequency shift achieved by the metasurface can be controlled, and the tag can be encoded by adopting the offset frequency numerical coding method.

[0020] Preferably, the varactor diode is MAVR-000120-14110P.

[0021] Preferably, the thickness of the top metal patch is 0.018 mm.

[0022] Preferably, the dielectric constant of the low-loss F4B intermediate layer is selected to be εr=2.65, and the tangent loss tanδ=0.001. The frequency difference information between the incident wave and the echo is used to encode the electronic tag, and multiple transmissions and receptions are used to increase the encoding capacity.

[0023] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0024] Example

[0025] A metasurface electronic tag that works at broadband and fully polarized microwave frequencies and can change the tag encoding information by changing the modulation voltage waveform, wherein the electronic tag includes a controller and an array structure composed of N×N metasurface units, each of which is a rotationally symmetrical structure consisting of a central circular metal patch and four surrounding semicircular metal patches, wherein the central circular metal patch has a thickness of 0.3 mm and a radius of 3 mm, and the four semicircular metal patches have a radius of 2.6 mm. The middle circular metal patch is connected to the four surrounding semicircular metal patches through four identical varactors, which are respectively embedded in four reserved 0.6 mm gaps of the top metal pattern. The metasurface unit includes a structured surface metal, a bottom metal ground, and a low-loss F4B intermediate medium.

[0026] like Figure 1 to Figure 4 As shown, the top layer of each square metasurface unit with a side length of 12.6 mm is a 90° rotationally symmetrical structure. This rotational symmetry has the same response to two arbitrary orthogonal waves. It is mainly composed of the following active components: first, a metal frame with a width and thickness of 0.3 mm is extended from the edge of the square unit inward, and then four semicircular metal patches with a radius of 2.6 mm are distributed with the midpoints of the four sides of the metal frame as the center of the circle, and a circular metal patch with a radius of 3 mm with the center of the unit as the center of the circle is located in the middle of the unit. Since there is a gap of 0.6 mm between the circular metal patch in the center and the semicircular metal patches around it, four MAVR-000120-14110P varactor diodes are used in the four empty gaps to connect the central metal patch and the semicircles around it. The rlc parameters of the varactor diode will change with the change of the voltage on both sides. The bandwidth characteristics of the unit are completely determined by the variable capacitance. Considering that the four varactors require external DC bias, a metal through hole with a diameter of 0.2mm is set to connect the central square patch and the metal ground. Finally, low-loss F4B is used as a filler between the top metal and the bottom metal.

[0027] In a further implementation, when the modulation waveform is set so that the reflection phase of the metasurface changes continuously and linearly within one modulation period Tm, the incident frequency f i will effectively be converted upon reflection into a new frequency component f r , resulting in a frequency shift Δf t =f r –f i (f r is the frequency of the reflected wave). Under this modulation, the linearly changing reflection phase of the metasurface Described as

[0028]

[0029] From equation (1), we can see that when the phase change covers 2π in one cycle, the conversion efficiency can reach 100% in principle, and the resulting frequency shift Δf t Controllable, satisfying |Δf t |=1 / Tm.

[0030] Figure 5 The phase curves under different capacitances under x and y polarization incidence are shown. It is observed that the reflected phase varies nonlinearly with voltage, which is mainly due to the nonlinear resonance of the element and the load varactor. By gradually increasing the applied bias, the programmable metasurface sample is able to provide a full 360° phase difference at all frequency points. Therefore, the actual conversion efficiency can reach 100%, and the resulting frequency shift Δf t Controllable.

[0031] The resulting frequency shift Δf t Under controllable conditions, the frequency difference Δf t This information is encoded. Set tags ID101, ID110, and ID111 to correspond to frequency shift Δf t The values ​​are -100kHz, -200kHz, and -300kHz; the labels ID001, ID010, and ID011 correspond to the frequency shift Δf t The value is 100kHz, 200kHz, 300kHz; when the frequency offset value Δf t When it is 0, it corresponds to tag ID000 or tag ID100.

[0032] In order to further improve the coding capacity of the electronic tag, a protocol is established between the transmitter and the receiver, and the signal is transmitted and received at a fixed time interval, and the same coding operation is performed. One transmission and reception is called a frame. The coding in each frame is determined by the offset value of the echo frequency, that is, by the modulation waveform generated by each frame. After the entire operation is completed, all frame codes are arranged in order to form a total code. For example, when the fixed interval is continuously transmitted and received 6 times, and the frequency difference is -100kHz, 0kHz, 200kHz, 0kHz, -300kHz, and 100kHz respectively, the code at this time is "101 100 010 000 111001" (where the frequency offset value is 0, the highest bit of this frame depends on the highest bit of the previous frame). Since the tag adopts the offset frequency numerical coding and multi-frame coding, the information storage capacity is greatly improved.

[0033] In this example, tag ID110 and tag ID010 correspond to Figure 6The normalized spectral power of the left and right echoes in the middle, 3 bits is determined by the offset value of the echo frequency. In multi-frame encoding, each frame can be encoded by changing the frequency offset value, and the encoding capacity can be directly improved by increasing the number of frames.

Claims

1. A metasurface electronic tag based on time modulation, characterized in that: It includes a modulation waveform controller and a metasurface; the modulation waveform controller is used to generate a modulation waveform; the metasurface is composed of a structured metal surface, a bottom metal ground and a low-loss intermediate medium, and the structured metal surface and the bottom metal ground are respectively arranged on the upper and lower surfaces of the intermediate medium; The output port of the modulation waveform controller is connected to any side of the metasurface array structure. The modulation waveform output by the modulation waveform controller is designed to generate a frequency offset for the electromagnetic wave incident on the metasurface, and the frequency offset value is used to realize the encoding of the electronic tag.

2. The time-modulated metasurface electronic tag according to claim 1 is characterized in that: The structured metal surface is composed of N×N super surface units, each of which includes a metal frame, a circular metal patch and four semicircular metal patches. The circular metal patch is located at the center of the super surface unit, and the circular metal patch and the four semicircular metal patches are connected by a varactor diode.

3. The time-modulated metasurface electronic tag according to claim 2 is characterized in that: The circular metal patch and four semicircular metal patches form a 90° rotationally symmetrical metal pattern on the unit surface, and are symmetrically embedded in four reserved 0.6 mm gaps of the top metal pattern through four identical varactors.

4. The time-modulated metasurface electronic tag according to claim 2 or 3, characterized in that: The width of the metal frame is 0.3mm, the radius of the circular metal patch is 3mm, and the radius of the semicircular metal patch is 2.6mm.

5. The time-modulated metasurface electronic tag according to claim 2 is characterized in that: The four semicircular metal patches respectively take the midpoints of the four sides of the metal frame as the centers of the circles.

6. The time-modulated metasurface electronic tag according to claim 2 is characterized in that: The varactor diode used is MAVR-000120-14110P.

7. The time-modulated metasurface electronic tag according to claim 1 is characterized in that: The thickness of the top metal patch is 0.018mm.

8. The time-modulated metasurface electronic tag according to claim 1 is characterized in that: The low-loss intermediate dielectric has a dielectric constant of 2.65 and a loss tangent of 0.

001.

9. The time-modulated metasurface electronic tag according to claim 1, characterized in that: The bottom metal ground is connected to the super surface unit through a metal cylinder with a radius of 0.2 mm and a common center with the circular metal patch.

10. The time-modulated metasurface electronic tag according to claim 1, characterized in that: The frequency difference information between the incident wave and the echo is used to encode the electronic tag, and multiple transmissions and receptions are used to increase the coding capacity.

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