Terahertz electrically controlled composite resonant reconfigurable smart surface

Abstract

The present invention discloses a terahertz electrically controlled composite resonant reconfigurable smart surface, comprising a metal base plate, a dielectric substrate, and a phase shift structure layer arranged layer by layer from bottom to top; the phase shift structure layer comprises phase shift units arranged in an M×N orthogonal array, and each column of phase shift units has an anode lead and a cathode lead; the phase shift unit comprises a circular ring resonant ring and an oscillation structure. The present invention adopts a two-dimensional planar artificial microstructure to achieve phase control of terahertz waves through a single-layer array. The structure is simple and can be realized by micro-machining means, with mature technology and easy production. The present invention works through electrical control to achieve dynamic broadband control of the phase. It does not require other more complex excitation methods such as external light excitation and temperature excitation, which makes the device have great advantages in miniaturization, practicality, and production.

Description

Technical Field

[0001] The present invention relates to the field of metamaterials and electromagnetic functional devices, and in particular to a terahertz electrically controlled composite resonant reconfigurable intelligent surface. Background Art

[0002] Terahertz (THz) waves generally refer to electromagnetic waves with a frequency range of 0.1THz to 10THz, lying between millimeter waves and infrared light, possessing characteristics of both microwaves and infrared light. They are characterized by moderate beamwidth and large system bandwidth, making them highly advantageous for target detection, imaging, and high-speed, high-capacity communications. They offer significant advantages in high-frame-rate, high-resolution imaging radar and broadband wireless communications. The development of a new generation of beam scanning technology is crucial for promoting the application of new terahertz radar and high-speed wireless communication systems, and is gaining increasing attention worldwide. This new scanning imaging technology, unlike traditional synthetic aperture imaging, is a new high-frame-rate, high-resolution three-dimensional imaging system that is independent of target or antenna platform motion. Its core technology is reconfigurable beam-scanning smart surfaces. These smart surfaces offer advantages such as more flexible beam scanning and enhanced anti-interference performance. Traditional metasurfaces are typically implemented using switching arrays of ferrite materials, positive-intrinsic-negative diodes, and field-effect transistors. Ferrite materials are bulky, costly, and difficult to integrate, while semiconductor switches suffer from high losses and poor linearity, hindering the application of metasurfaces in the terahertz band. Artificial microstructures combined with phase-change materials are a new type of subwavelength periodic artificial structure material that is both designable and controllable. By altering the state properties of the phase-change material, the intensity and spectral range of its response to electromagnetic waves can be controlled.

[0003] With the development of modern micro-machining technology, artificial microstructures have played a huge role in promoting the development of passive functional devices. A variety of related functional devices have been developed in the microwave and millimeter wave bands, terahertz bands, and optical bands. However, the difficulty of processing in the low-frequency band is different from that in the terahertz high-frequency band, and the methods of expanding the frequency band bandwidth are also different. Most ordinary single-layer structures have the disadvantages of small bandwidth and low amplitude efficiency. The structure in the low-frequency band can be expanded by stacking multiple layers or adding coupling holes to improve the amplitude efficiency. However, in the terahertz band, due to the limitations of current processing technology, it is difficult to achieve drilling and multi-layer structure processing. Therefore, the present invention introduces a composite resonance method to improve the bandwidth and efficiency of similar structures in the terahertz band. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an adjustable phase shift array with simple structure, easy processing and low loss.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] A terahertz electrically controlled composite resonant reconfigurable smart surface, comprising a metal base plate, a dielectric substrate, and a phase-shift structure layer arranged layer by layer from bottom to top;

[0007] The phase shift structure layer includes phase shift units arranged in an M×N orthogonal array, and each column of phase shift units has an anode lead wire and a cathode lead wire;

[0008] The phase shift unit includes a circular ring resonant ring and a resonant structure;

[0009] The resonant ring is bilaterally symmetrical, and an opening is provided at the upper and lower intersections of the ring and the symmetry axis, forming two independent left and right half rings;

[0010] The resonant structure is arranged in the center of the annular resonant ring. The resonant structure includes two metal sheets arranged in a bilaterally symmetrical manner on either side of the symmetry axis of the resonant ring. The long sides of the metal sheets are parallel to the symmetry axis. The metal sheets are connected to the semi-ring on their side via metal connecting strips. A doped heterojunction wire is arranged between the two metal sheets. The doped heterojunction wire is arranged along the symmetry axis of the resonant ring and is equidistant from the two metal sheets. An ohmic patch is provided between the doped heterojunction wire and the dielectric substrate.

[0011] In the same column, the doped heterojunction lines of each phase shift unit are connected through the anode lead line of the column and led to the anode connection terminal, the left half ring is connected to the cathode connection terminal through a cathode lead line, and the right half ring is connected to the cathode connection terminal through another cathode lead line.

[0012] Furthermore, the metal of the metal base plate includes one or more of aluminum, silver, and gold.

[0013] Furthermore, the material of the dielectric substrate includes one or more of sapphire, high-resistance silicon, InP, GaAs, and silicon carbide.

[0014] Furthermore, both M and N are integers greater than 2.

[0015] Furthermore, the center of the annular resonant ring is located on the axis of the metal connecting strip.

[0016] Furthermore, the connection point between the metal sheet and the metal connecting strip is located at the midpoint of the long side of the metal sheet, and the axis of the metal connecting strip is perpendicular to the symmetry axis of the resonant ring.

[0017] Furthermore, the metal sheet is in the shape of a rectangle.

[0018] Furthermore, the material of the doped heterojunction wire includes one or more of AlGaN, GaN, InGaN, GaN, AlGaAs, and GaAs.

[0019] Furthermore, the material of the ohmic patch includes one or more of Ti, Al, Ni, and Au.

[0020] The beneficial effects of the present invention are:

[0021] (1) The transistor of the present invention has a fast modulation function, so it is used as the core dynamic functional material of the present invention to achieve high-speed phase shift characteristics.

[0022] (2) The present invention changes the equivalent circuit of the entire structure by adjusting the size of the resonant ring and the concentration of the HEMT two-dimensional electron gas. Compared with the structure with rings on both sides, the dipole is embedded in the middle and introduces dipole resonance. This coupling effect organically combines the two originally independent resonant modes into a new hybrid resonant mode. The hybrid resonant mode achieves enhanced coupling of ring-like dipole resonance and dipole resonance. The coupled resonance of the dipole and the ring gives the structure better amplitude consistency and expands the phase shift bandwidth to 27 GHz, further improving the device integration and array control accuracy.

[0023] (3) The present invention adopts a two-dimensional planar artificial microstructure to achieve phase control of terahertz waves through a single-layer array. The structure is simple and can be realized through micro-machining means. The process is mature and easy to manufacture.

[0024] (4) The present invention operates through electrical control, thereby achieving dynamic broadband control of the phase. This eliminates the need for external, more complex excitation methods such as light excitation and temperature excitation, making the device highly advantageous in terms of miniaturization, practicality, and production volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the terahertz electrically controlled composite resonant reconfigurable smart surface structure of the present invention;

[0026] Figure 2 Schematic diagram of the phase shift unit structure, where (a) is a side view and (b) is a top view.

[0027] Figure 3 It is the amplitude characteristic curve of the unit structure in the ON and OFF states;

[0028] Figure 4 Phase shift curve diagram of the unit structure in ON and OFF states;

[0029] Figure 5 The current electric field diagram of the unit structure in the ideal ON and OFF states;

[0030] Figure 6 Schematic diagram of beam scanning for reconfigurable smart surfaces. DETAILED DESCRIPTION

[0031] This invention combines artificial microstructures with transistors to form a terahertz electrically controlled composite resonant metasurface phase-shift array. A two-dimensional planar arrangement forms the composite array reflector. By controlling the on / off switching of the transistors to change the resonant mode, it achieves large-scale phase control of X-polarized terahertz waves. The operation is quasi-optical, and within the 180° frequency band of the phase shift, beam scanning and beamforming with 1-bit column-controlled coding can be further achieved.

[0032] The present invention provides an artificial microstructure reflection array that has a frequency response to terahertz electromagnetic waves in a specific frequency band. The array structure is then combined with transistors using microelectronic processing technology, and the on and off of the transistors are controlled by an external voltage. Finally, the resonant mode of the artificial microstructure is changed by electrical control to achieve large phase control capability of terahertz waves.

[0033] See also Figure 1 、 Figure 2 The terahertz electrically controlled composite resonant reconfigurable smart surface of the present invention includes: a metal base plate, a dielectric substrate located on the metal base plate, and a phase shift array (phase shift structure layer) located on the dielectric substrate. The dielectric substrate is a semiconductor material; the phase shift structure layer is provided on the upper surface of the substrate in the form of a metal coating; a vertical negative metal feed line (cathode lead line) is provided for each column of unit antennas, and all negative metal feed lines in the array are connected to the same external negative electrode; ohmic patches are provided on the dielectric substrate, and doped heterogeneous wires are provided on each ohmic patch; a vertical anode lead line (positive feed line) is provided for each column of unit antennas, located on the right side of the unit, and connected to the doped heterogeneous material in that column. Each positive feed line in each column is externally connected to a positive electrode, allowing for independent control of each column. The carrier concentration of the doped heterogeneous material is controlled by the voltage difference between the external positive electrode and the external negative electrode, achieving on-off regulation, thereby adjusting the phase of the incident electromagnetic wave.

[0034] The substrate is sapphire, high-resistance silicon, InP, GaAs or silicon carbide.

[0035] The feed line and the unit patch are made of Au, Ag, Cu or Al.

[0036] The material of the ohmic patch is Ti, Al, Ni or Au.

[0037] The doped heterogeneous material is AlGaN / GaN, InGaN / GaN or AlGaAs / GaAs.

[0038] The artificial microstructure polarization deflection reflection array is an array of MN composed of multiple units, where M>2 and N>2.

[0039] Example:

[0040] This embodiment includes:

[0041] Metal base plate, made of good conductors such as aluminum, silver, and gold;

[0042] Semiconductor substrate, made of sapphire, high-resistance silicon, silicon carbide, etc.

[0043] The phase shift units are arranged in an M×N orthogonal array on a semiconductor substrate.

[0044] See also Figure 2 The phase shift unit includes a resonant ring 3 with two openings and a dipole oscillation structure 4. The dipole oscillation structure 4 is arranged at the opening of the resonant ring. The two end points of the resonant ring are respectively connected to a rectangular metal strip. The connection point is located at the center of the long side of the rectangular metal strip. The long side of the rectangular metal strip is perpendicular to the side of the resonant ring where the opening is located. An ohmic patch is arranged on the upper surface of the dielectric substrate between the two rectangular metal strips at the opening. A doped heterojunction line is arranged above the ohmic patch. The doped heterojunction line is parallel to and equidistant from the two rectangular metal strips.

[0045] In each column, the doped heterojunction line of the phase shift unit is connected to the anode lead line of the column, and the split resonant ring is connected to the cathode lead line of the column ( Figure 2 1 and 2 in the figure are cathode lead wires, and the one drawn from the center of the ring is the anode lead wire);

[0046] Each cathode lead-out line is connected to the same cathode bus, which has an external cathode connection terminal; each anode lead-out line is independent of each other.

[0047] The material of the ohmic patch is Ti, Al, Ni or Au, and the material of the doped heterojunction wire is AlGaN / GaN, InGaN / GaN, AlGaAs / GaAs, AlGaAs / InGaAs, AlGaAs / InGaAs / InP, etc.

[0048] The anode lead wire is connected to different external positive electrodes. The voltage difference between the external positive electrode and the external negative electrode is used to control the carrier concentration of the doped heterogeneous material, realize on-off switching, and then perform phase control on the electromagnetic beam.

[0049] The present invention achieves phase regulation of terahertz reflected electromagnetic waves by changing the on and off states of transistors, whose on and off states are controlled by the magnitude of an applied voltage. Specifically, by changing the voltage difference between the positive and negative electrode lines connected to the transistor electrodes in the structure, the transistor will switch between the cutoff and on states.

[0050] Simulation results show that the applied voltage changes the cutoff and conduction states of the transistor, thereby achieving phase control of the terahertz beam. Figure 3The amplitude characteristics of the unit are shown. In the ON and OFF states, the insertion loss of the unit structure is small, and the dynamically adjustable array can achieve high-efficiency phase modulation. Figure 4 The figure shows the phase shift characteristics of the phase shift unit at specific voltages. "OFF" indicates that the transistor located within the artificial electromagnetic medium is in the pinch-off state at a specific voltage, while "ON" indicates that the transistor is in the on state when no voltage is applied. It can be seen that the reflection phase of the unit structure varies significantly with the transistor state. Between 0.325THz and 0.352THz, there is a 180°±20° phase difference between the unit in the "ON" and "OFF" states. The unit phase bandwidth varies by approximately 27GHz, offering a wide adjustable range. Figure 5 The electric field and current diagrams of the phase shift unit when in ideal on and off states are shown. The phase shift of the structure is mainly controlled by the coupled resonance between the resonant ring and the embedded dipole length switching, which illustrates the phase shift mechanism of the phase shift structure. Table 1 shows the coding sequence for beam scanning. Figure 6 The beam simulation scanning diagram of the 32×32 RIS array at 13.1°~81° shows that the array composed of this structure can perform continuous beam scanning in a single polarization direction.

[0051] Table 1

[0052]

[0053] Note: Nx represents the number of adjacent in-phase unit intervals.

[0054] The present invention, based on a HEMT transistor-metasurface ring dipole structure, differs from the ring-loaded dual-HEMT structure employed in Zhang, Y., et al. ("Largephase modulation of THz waves via an enhanced resonant active HEMT metasurface.") Nanophotonics 8.1 (2018). The present invention eliminates the HEMT transistors at either end of the split ring and introduces a HEMT transistor with a larger two-dimensional electron gas region at the center of the dipole, located horizontally symmetrically around the ring. The phase shift mechanisms of the two structures are completely different. The phase shift in the present invention arises from the resonant switching of the ring-like dipole coupled with the long-short dipole. Compared to the dipole-ring LC resonant switching of the resonant ring-loaded dual-HEMT structure, the present invention achieves greater switching state discrimination, stronger resonance intensity, and better impedance matching. By increasing the two-dimensional electron gas gate area and optimizing the matching artificial microstructure, the present invention effectively improves bandwidth and reduces losses, increasing the average amplitude by 11.5 dB and achieving an average phase shift of 180° over a wide bandwidth of 27 GHz. The maximum phase shift of the resonant ring-loaded dual-HEMT structure is only 153°. The structure works in a quasi-optical mode, and within the 180° phase-shifted frequency band, it can further realize 1-bit train-controlled coded beam scanning and beam shaping. It uses external electrical control to control the electron gas characteristics and resonant modes of the composite metasurface microstructure array to perform phase regulation on the terahertz wave. This is one of the most cutting-edge research areas in this field internationally and a new approach to achieving advanced scanning technology.

Claims

1. Terahertz electrically controlled composite resonant reconfigurable smart surface, characterized by: It includes a metal base plate, a dielectric substrate and a phase shift structure layer which are arranged layer by layer from bottom to top; The phase shift structure layer includes phase shift units arranged in an M×N orthogonal array, and each column of phase shift units has an anode lead wire and a cathode lead wire; The phase shift unit includes a circular ring resonant ring and a resonant structure; The resonant ring is bilaterally symmetrical, and an opening is provided at the upper and lower intersections of the ring and the symmetry axis, forming two independent left and right half rings; The resonant structure is arranged in the center of the annular resonant ring. The resonant structure includes two metal sheets arranged in a bilaterally symmetrical manner on either side of the symmetry axis of the resonant ring. The long sides of the metal sheets are parallel to the symmetry axis. The metal sheets are connected to the semi-ring on their side via metal connecting strips. A doped heterojunction wire is arranged between the two metal sheets. The doped heterojunction wire is arranged along the symmetry axis of the resonant ring and is equidistant from the two metal sheets. An ohmic patch is provided between the doped heterojunction wire and the dielectric substrate. In the same column, the doped heterojunction wires of each phase shift unit are connected to the anode connection terminal through the anode lead wire of the column, the left half ring is connected to the cathode connection terminal through a cathode lead wire, and the right half ring is connected to the cathode connection terminal through another cathode lead wire; The center of the annular resonant ring is located on the axis of the metal connecting strip; The connection point between the metal sheet and the metal connecting strip is located at the midpoint of the long side of the metal sheet, and the axis of the metal connecting strip is perpendicular to the symmetry axis of the resonant ring.

2. The terahertz electrically controlled composite resonant reconfigurable smart surface according to claim 1, wherein: The metal of the metal base plate includes one or more of aluminum, silver, and gold.

3. The terahertz electrically controlled composite resonant reconfigurable smart surface according to claim 1, wherein: The material of the dielectric substrate includes one or more of sapphire, high-resistance silicon, InP, GaAs, and silicon carbide.

4. The terahertz electrically controlled composite resonant reconfigurable smart surface according to claim 1, wherein: Both M and N are integers greater than 2.

5. The terahertz electrically controlled composite resonant reconfigurable smart surface according to claim 1, wherein: The metal sheet is in the shape of a rectangle.

6. The terahertz electrically controlled composite resonant reconfigurable smart surface according to claim 1, wherein: The material of the doped heterojunction wire includes one or more of AlGaN, GaN, InGaN, GaN, AlGaAs, and GaAs.

7. The terahertz electrically controlled composite resonant reconfigurable smart surface according to claim 1, wherein: The material of the ohmic patch includes one or more of Ti, Al, Ni, and Au.

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