Terahertz reconfigurable transmission metasurface unit with continuously regulated phase

Abstract

The invention discloses a terahertz reconfigurable transmission metasurface unit with a continuously controllable phase. The terahertz reconfigurable transmission metasurface unit is specifically and structurally composed of a pair of metal patterns printed on the two sides of a single-layer quartz substrate, a Schottky variable capacitance diode and a direct current bias line. Wherein the metal pattern is composed of two I-shaped patterns which are symmetrically distributed, a Schottky variable capacitance diode is introduced between the two I-shaped patterns, and the continuous regulation and control of the phase of the transmission metasurface unit are realized by utilizing the continuous change of the capacitance value of the Schottky variable capacitance diode. Two sections of bias lines are introduced to the left side and the right side of each I-shaped pattern respectively and used for being connected with a direct-current stabilized power supply, and the capacitance value of the Schottky variable capacitance diode can be controlled to change continuously by changing the voltage of the direct-current stabilized power supply. The terahertz reconfigurable transmission metasurface antenna has the advantages that the transmission phase can be continuously regulated and controlled, the transmission phase shift range is large, the unit structure is simple and easy to integrate and the like, the terahertz reconfigurable transmission metasurface antenna is expected to be applied to arraying of the terahertz reconfigurable transmission metasurface antenna, and flexible regulation and control of terahertz waves are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz reconfigurable transmission metasurfaces, and in particular to a terahertz reconfigurable transmission metasurface unit with continuous phase control and a design method thereof. Background Art

[0002] The terahertz spectrum has the characteristics of large bandwidth, large communication capacity, and high transmission rate. In the future, it is expected to be widely used in 6G communication scenarios such as ultra-large capacity data backhaul, short-distance ultra-high-speed transmission, holographic communication, and micro-size communication. However, as the operating frequency increases, the path loss coefficient of the terahertz wave also increases, which causes the terahertz signal to face serious free space loss and atmospheric attenuation during transmission. Therefore, in order to overcome the performance limitations caused by path loss, terahertz communication requires a larger antenna array to obtain higher system gain.

[0003] Although traditional large-scale or even ultra-large-scale phased array antennas can provide high gain, in order to achieve flexible control of terahertz beams, phased array antennas require a large number of TR components, which are very expensive in the terahertz frequency band. In addition, the high-frequency loss of the feeding network is also an issue that cannot be ignored. In contrast, the reconfigurable smart surface technology that integrates the spatial feeding system and array theory has the characteristics of simple architecture, flexible beam control, and low system cost, and has become a research hotspot in terahertz beam control technology.

[0004] Existing research on reconfigurable metasurface antenna technology is mainly focused on the microwave and millimeter wave bands, and the implementation method is usually to load PIN diodes or varactor diodes in the metasurface unit to achieve phase reconfiguration of the unit. However, when the operating frequency is increased to the terahertz band, the high-frequency parasitic effects, nonlinear characteristics and large physical size of PIN diodes or varactor diodes limit their use in terahertz reconfigurable metasurface antennas. On the other hand, since reflective metasurfaces have a natural tendency to be conducive to the deployment and design of bias networks, the current terahertz reconfigurable metasurface technology mainly adopts a reflective system, and research on reconfigurable metasurface technology for transmissive systems has just started.

[0005] The Chinese patent (CN115275588A) proposes a graphene-based terahertz smart metasurface antenna unit, which uses the characteristic that the surface impedance of the graphene material changes with the electric potential to achieve its 1-bit phase reconfiguration at 300GHz. However, the transmission amplitude of the unit is below -4dB, and only the modulation of the two transmission phase states of "0°" and "180°" is achieved.

[0006] In 2021, researchers from Southeast University proposed a 1-bit digitally coded transmissive metasurface based on liquid crystals in "Programmable manipulations of terahertz beams by transmissive digital coding metasurfaces based on liquid crystals, Advanced Optical Materials, 2021, 9: 2100932." By dynamically controlling the liquid crystal, the coded transmissive metasurface achieved ±30° two-dimensional beam scanning at 0.408THz. However, liquid crystal materials have high requirements for uniformity and stability and are difficult to manufacture. The transmissive metasurface unit only uses a discrete method for phase control.

[0007] In summary, compared with the design of microwave and millimeter wave reconfigurable metasurfaces, the design of terahertz reconfigurable transmission metasurfaces is extremely challenging. Existing terahertz reconfigurable transmission metasurface designs only use discrete phase control, which will introduce a certain phase error, thus affecting the accuracy of beam control. Therefore, it is of great significance to carry out research on terahertz reconfigurable transmission metasurface antenna technology with continuous phase control. Summary of the invention

[0008] The goal of the present invention is to solve the design challenges of terahertz reconfigurable transmission metasurface units in terms of structural design, device performance limitations, and continuous modulation of transmission phase, and to realize a metasurface transmission unit with a simple structure and continuous phase modulation, in which a double-layer metal sheet is loaded with a single-layer dielectric plate, by regulating the variable capacitance Schottky diode.

[0009] The present invention adopts the following technical scheme: a terahertz reconfigurable metasurface transmission unit loaded with a Schottky varactor diode, comprising: a single-layer quartz dielectric substrate (1), a "double I" type metal patch (2), a Schottky varactor diode (3) and a DC bias line (④). The "double I" type metal patch is printed on the front and back sides of the single-layer quartz dielectric substrate, and the two "I" type metal patches are centrally symmetrically distributed and are relatively close to each other, introducing multiple gap structures (gap capacitors), broadening the phase modulation range and ensuring the broadband performance of the unit, and the two poles of the Schottky varactor diode are mounted between the two "I" structures and connected in parallel with the gap capacitors introduced on both sides to adjust the unit transmission phase.

[0010] The design of the laterally distributed bias line is orthogonal to the polarization direction of the unit, which reduces the impact on the unit's transmission performance. At the same time, the Schottky varactor diodes on the upper and lower layers of the unit can be connected to the positive and negative electrodes of the DC voltage regulator respectively. The bias line is integrated with the "double I" type metal patch on the front and back sides of the quartz dielectric plate. The diodes mounted between the "double I" type metal patches can achieve different capacitance value regulation under the control of the DC voltage regulator, changing the current distribution on the metal patch and thus achieving the regulation of the unit's transmission phase.

[0011] The innovation of the present invention lies in:

[0012] 1. The design of the double "I"-shaped metal pattern printed on the upper and lower sides of the quartz dielectric substrate and in a centrally symmetrical manner introduces a certain degree of coupling (gap capacitance), which makes up for the performance limitation of the variable capacitance diode in the terahertz frequency band due to the reduction of junction capacitance, expands the phase modulation range, and ensures good bandwidth performance.

[0013] 2. Two bias lines orthogonal to the polarization direction are introduced on the left and right sides of the two "I"-shaped patterns respectively, which are used to connect to the DC regulated power supply. By controlling the DC voltage across the two Schottky varactor diodes loaded between the "double I"-shaped metal patches, the capacitance value of the Schottky varactor diodes changes continuously, realizing the continuous regulation of the unit transmission phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a three-dimensional view of the present invention, Figure 2 This is a top view of a terahertz reconfigurable transmission metasurface unit with continuous phase control. Figure 3 This is a side view of a terahertz reconfigurable transmission metasurface unit with continuous phase control. Figure 4 This is the capacitance change curve of Schottky varactor diode under the control of voltage regulator. Figure 5 The simulation curves of the amplitude and phase frequency response (f = 0.215THz ~ 0.225THz) of the terahertz reconfigurable transmission metasurface unit with continuous phase control under different capacitance values ​​of Schottky varactor diodes are shown in Figure 2. Figure 6 This is the amplitude and phase simulation curve of the terahertz reconfigurable transmission metasurface unit with continuously phase control at different capacitance values ​​of the Schottky varactor diode when the center frequency is 0.22THz.

[0015] Figure 1 In the figure, numeral 1 is a single-layer quartz dielectric substrate, 2 is a "double I" type metal patch, 3 is a Schottky varactor diode and ④ is a DC bias line. Specific implementation plan

[0016] The present invention proposes a terahertz reconfigurable transmission metasurface unit with continuously adjustable phase, which is composed of a pair of metal patterns printed on both sides of a single-layer quartz substrate, a Schottky varactor diode and a DC bias line. A centrally symmetrical double "I"-shaped metal pattern is printed on the upper and lower sides of the quartz dielectric substrate, and a Schottky varactor diode is loaded between each of the two double "I"-shaped metal patches. The DC bias line is led out from the left and right sides of the two "I"-shaped metal patterns and connected to the two poles of the diode respectively. The other side of the bias line is connected to a DC voltage regulator, and by controlling the voltage across the two Schottky varactor diodes, the capacitance value of the Schottky varactor diode changes continuously, thereby realizing continuous regulation of the unit transmission phase.

[0017] Figure 1 It is the overall structure of the present invention, Figure 2 , Figure 3 They are respectively the top view and the side view of the present invention. The medium 1 is a square quartz material, with a dielectric constant of about 3.78, a magnetic permeability of 1, a loss tangent of 0.0044, a length and width of L1=682μm, a thickness of h1=127μm, and a material of the "double I" type metal patch. The length of the long strip structure on both sides is L2=240μm, the width is w2=50μm, the length of the center part is L3=320μm, the width is w1=160μm, and the center distance between the "I" type metal patches is L4 =90μm, and the gap between the long strip structures on both sides is w4=10μm; the gap formed between the "double I" type metal patches introduces a certain resonance (gap capacitance), expands the unit bandwidth, and reserves enough space for the Schottky varactor diode; the length of the lateral DC bias line on both sides is L5=90μm, and the width is w5=20μm; the bias line distribution of the lateral structure is orthogonal to the polarization of the unit, reducing the impact of the introduction of the voltage control line on the unit transmission performance. The "double I" type metal patch and the bias lines on both sides are made of copper, with a thickness of h2=3μm, and 3 is the loaded Schottky varactor diode, with a width of w4=53μm.

[0018] Figure 4 This is the capacitance variation curve of the Schottky varactor diode loaded on the unit under the control of a regulated power supply. The breakdown voltage of the diode is 0.8V. Within the voltage range of -0.8V to +0.8V, the capacitance variation range of the diode is approximately 3 to 16fF. Figure 5 It is the frequency response curve of the transmission amplitude and phase of the terahertz reconfigurable transmission unit when several groups of unit capacitance values ​​(C = 3, 6, 7, 15fF) have different values. Its operating frequency is 0.215THz-0.225THz and its bandwidth is 10GHz. Figure 6The transmission amplitude and phase curve of the terahertz reconfigurable transmission unit at different capacitance values ​​when the unit is at the center frequency of 0.22THz, the transmission amplitude is in the range of -2.92--0.34dB, and the phase shift is about 334°. Through the control of DC voltage, the transmission type terahertz reconfigurable metasurface unit of the present invention can achieve continuous phase regulation of about 334° and has good broadband performance.

[0019] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A terahertz reconfigurable transmission metasurface unit with continuous phase control, the specific structure of which consists of a pair of metal patterns (2) printed on both sides of a single-layer quartz substrate (1), a Schottky varactor diode (3) and a DC bias line (④), characterized in that: The metal pattern (2) is composed of two symmetrically distributed "double I"-shaped patterns on the upper and lower sides of a single-layer quartz substrate 1. The two adjacent "I"-shaped patterns are connected in the middle by a Schottky varactor diode (3), and the two poles of the Schottky varactor diode (3) are loaded on the two adjacent "I"-shaped patterns.

2. The terahertz reconfigurable transmission metasurface unit with continuous phase control according to claim 1, characterized in that: Two adjacent "I"-type patterns will introduce additional coupling, which not only expands the working bandwidth of the transmissive metasurface unit, but also expands the phase range of the transmissive metasurface unit.

3. The terahertz reconfigurable transmission metasurface unit with continuous phase control according to claim 1, characterized in that: A Schottky varactor diode (3) is introduced between two "I" shapes of the metal pattern (2), and the working capacitance of the Schottky varactor diode is regulated by voltage control to change the surface current distribution on the unit metal patch, thereby realizing continuous regulation of the phase of the transmission metasurface unit, thereby realizing a reconfigurable function of the transmission phase.

4. The terahertz reconfigurable transmission metasurface unit with continuous phase control according to claim 1, characterized in that: Two sections of bias lines orthogonal to the polarization direction are respectively introduced on the left and right sides of the two "I"-shaped patterns of the metal pattern (2) for connecting a DC voltage-stabilized power supply. By changing the voltage of the DC voltage-stabilized power supply, the capacitance value of the Schottky varactor diode can be controlled to change continuously.

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