A three-dimensional direction far-field beam coding and regulation structure of terahertz wave

Abstract

This invention relates to the field of electromagnetic wavefront modulation functional devices. It discloses a three-dimensional far-field beamforming encoding and modulation structure for terahertz waves, comprising a composite microstructure arranged in a rectangular pattern on a two-dimensional plane, consisting of a substrate, a metal base plate, a metal microstructure, and a HEMT. The key feature is that the metal microstructure and HEMT are located on the substrate surface. The metal microstructure is a notched ring, and the HEMT is placed at the notch. The HEMT consists of a gate lead, a hetero-doped structure, a source electrode, and a drain electrode. This invention employs a two-dimensional digitally independently encoded and modulated composite microstructure array unit to generate changes in reflection amplitude and phase, ultimately achieving three-dimensional far-field beamforming encoding and modulation. It possesses high beamforming freedom, real-time beamforming capability, and is small in size and thin in thickness.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wavefront modulation functional device technology, specifically to a three-dimensional directional far-field beam coding and modulation structure for terahertz waves. Background Technology

[0002] Terahertz technology has seen rapid development in wireless communication, spectroscopy, and imaging. Various functional devices have been developed, including filters, absorbers, polarizers, mixers, and modulators. Among these, terahertz phase modulation is a current research hotspot, serving as a core technology for flexible terahertz wavefront control, beam scanning, and focus deflection. Terahertz phase modulation is indispensable in terahertz wireless communication, high-resolution imaging, and radar systems. However, terahertz technology faces the challenge of short transmission distances in applications, requiring increased antenna gain to compensate for losses. However, most high-gain antennas are difficult to adjust, with fixed propagation angles, reducing system practicality. One solution is to use terahertz wavefront shaping technology, which allows for flexible manipulation of beam direction and wavefront characteristics to meet the application requirements of terahertz systems. Terahertz phase modulators are key technologies for realizing terahertz wavefront modulation; future development will focus on achieving more efficient and wider-bandwidth phase modulators, as well as enabling terahertz wavefront modulation for a wider range of applications.

[0003] A digitally coded metasurface is a subwavelength planar array that encodes metasurface units as digital coding units to achieve different wavefront modulation functions. By integrating switching elements on the metaunits, a variety of modulation characteristics can be imparted to the metasurface. For example, by loading materials or components such as liquid crystal materials, microwave RF diodes, and vanadium dioxide, and by changing the physical properties of these materials or components, the resonant electromagnetic field of the metaunit excited by a space plane wave can be altered, resulting in modulation of the reflection phase and amplitude, as well as conversion of polarization direction and mode. The reflective metasurface medium is generally set to a quarter-wavelength thickness, with a metal layer covering the bottom so that the electromagnetic wave propagates half a wavelength after passing through the artificial microstructure layer, further enhancing the subwavelength microstructure modulation effect.

[0004] Two-dimensional electron gases in high electron mobility transistors (HEMTs) possess the ability to interact with terahertz waves. Research shows that by adjusting the geometrical plasma frequency of the two-dimensional electron gas in HEMT devices, the plasma resonant frequency can be loaded onto the incident terahertz wave, thereby enabling the fabrication of terahertz sensors, mixers, and frequency multipliers. AlGaN / GaN heterojunction high electron mobility transistors can generate two-dimensional electron gases with high electron mobility, enhancing the on / off characteristics during HEMT, and are also small in size, facilitating metasurface integration. Summary of the Invention

[0005] The purpose of this invention is to provide a three-dimensional far-field beam coding and control structure for terahertz waves. It integrates a large number of HEMT devices using a subwavelength composite microstructure metal planar array to generate digital phase shift. By punching holes, the switching control circuit is moved to the back of the reflector array to achieve two-dimensional independent coding function, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a three-dimensional far-field beam encoding and control structure for terahertz waves, comprising a composite microstructure composed of a substrate, a metal base plate, a metal microstructure, and a HEMT arranged in a rectangular pattern on a two-dimensional plane, wherein the metal microstructure and the HEMT of the composite microstructure are located on the surface of the substrate, the metal microstructure is a notched ring, and the HEMT is placed at the notch of the metal microstructure, wherein the HEMT is composed of a gate lead, a hetero-doped structure, a source electrode, and a drain electrode.

[0007] Preferably, the metal microstructure is provided with through holes, and by leading the gate of the HEMT to the back of the reflective substrate for layout and wiring, the purpose of reducing the interference of the lead wires on the reflection can be achieved.

[0008] Preferably, the coding and control structure of the three-dimensional far-field beam of the terahertz wave further includes: based on the switching control effect of the gate voltage on the HEMT, using N×N digital control voltages to drive the HEMT of the microstructure array elements to produce a phase shift switching effect, thereby realizing the coding and control of the three-dimensional far-field beam of the terahertz wave by the composite microstructure.

[0009] Preferably, the substrate includes an upper substrate and a lower substrate, wherein the upper substrate is used to load the metal microstructure and the metal base plate, and the lower substrate is used to arrange the anode leads of the reflective array.

[0010] Preferably, the uppermost layer of the composite microstructure consists of a metal microstructure and an HEMT integrated on it, with both ends of the HEMT connected to the metal microstructure and grounded through a cathode lead.

[0011] Preferably, the pads of the HEMT gate-connected metal vias are connected to independent anode leads on the back of the reflective array, so that each metal microstructure has an independent anode lead to achieve independent control.

[0012] Preferably, the metal microstructure is a C-shaped metal ring surrounding a metal via pad, with both ends of the C-shaped metal ring connected to electronic control switching devices. Holes are drilled on the back of the unit for wiring to achieve independent coded control for each electronic control switching device.

[0013] The three-dimensional far-field beam coding and control structure for terahertz waves proposed in this invention has the following advantages:

[0014] 1. The metal microstructure of this invention is simple, with a single resonant ring forming the main resonant structure. It has no complex structure, which reduces the uncertainty of processing errors.

[0015] 2. The present invention has a high degree of freedom in the coding and control of the reflective array. By drilling holes on the substrate, each microstructure unit on the reflective array can be independently coded and controlled, thereby realizing the effect of three-dimensional beam direction scanning or spherical wave to plane wave conversion.

[0016] 3. The control method of the HEMT of this invention enables the coded reflective array to achieve real-time regulation and direct voltage control. It eliminates the need for redundant physical quantity conversion and can directly control the encoding with electrical signals, reducing the equipment used in actual scenarios and lowering the threshold for using the coded reflective array. The ease of use, portability, and efficiency of this device in application are guaranteed.

[0017] In summary, this invention employs a two-dimensional digitally independently coded composite microstructure array unit to generate changes in reflection amplitude and phase, ultimately achieving coded control of the far-field beam in three dimensions. It possesses a high degree of freedom in beam control, along with real-time beam control functionality, and is small in size and thin in thickness, thus showing promising application prospects in terahertz mobile wireless communication. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the C-shaped metal patch structure of the present invention;

[0020] Figure 3 This is a perspective view of the C-shaped metal patch structure of the present invention;

[0021] Figure 4 This is a schematic diagram showing the amplitude and phase shift characteristics of the phase shift unit of the present invention in the switching state;

[0022] Figure 5 This is a schematic diagram showing the variation of the reflection coefficient and operating frequency band of the metasurface of the present invention under different incident angles. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 1This invention provides a technical solution: a three-dimensional far-field beamforming encoding and control structure for terahertz waves, comprising: a metal substrate, a dielectric substrate located above the metal substrate, a wiring substrate located below the metal substrate, a metal microstructure located on the upper substrate, and a HEMT connected to vias and the metal microstructure. The metal microstructure is a notched ring, with the HEMT placed at the notch. The HEMT consists of a gate lead, a hetero-doped structure, a source electrode, and a drain electrode. The main body of the HEMT is a hetero-doped structure disposed on the substrate surface, with source and drain electrodes at both ends connected to the metal microstructure. The hetero-doped structure is provided with... Gate leads are placed; a vertical cathode lead is led out from the side of each metal microstructure, and the cathode leads of each column of metal microstructures are directly connected, and the cathode leads of each column are finally connected together at the edge of the reflective array; on the substrate surface, the gate of each HEMT is connected to the metal of the via through the anode lead; on the back side of the substrate, the anode lead continues to lead out of the array at each via; applying a control voltage between the anode and cathode can change the concentration of two-dimensional electron gas in the heterojunction to produce conduction and turn-off effects between the gaps in the metal microstructures, ultimately changing the phase information of the reflected electromagnetic wave.

[0025] In this embodiment, the substrate of the upper metal microstructure is sapphire, high-resistivity silicon, InP, GaAs or silicon carbide, and the lower wiring substrate is RogersRT5880, ArlonAD250C or Polymide.

[0026] In this embodiment, the metal microstructure and the metal substrate are made of gold, silver, copper, or aluminum.

[0027] In this embodiment, the doped heteromaterial of HEMT is AlGaN / GaN, InGaN / GaN, or AlGaAs / GaAs.

[0028] In this embodiment, the coded reflective array consists of N*N microstructure units, each with a size of 400 μm, a metal microstructure thickness of 0.2 μm, a lead width of 4 μm, and two substrates with a thickness of 100 μm each.

[0029] In this embodiment, more specifically, the metal microstructure and metal substrate are made of gold; the dielectric substrate is made of silicon carbide; the wiring substrate is made of Rogers RT5880; the metal electrodes and gate leads are made of gold; and the doped heterostructure of the HEMT is AlGaN / GaN.

[0030] like Figure 2 and Figure 3As shown, the metal microstructure includes a symmetrically beveled "C"-shaped metal patch on both the top and bottom. A row of cathode leads is connected to the left side of the metal microstructure via leads, which ultimately ground. The notches of the metal microstructure patch are connected to two rectangular metal patch electrodes, which are used to connect hetero-doped structures. The length of these electrodes is less than the width of the patch edge. A hetero-doped structure is positioned between the two electrodes, and a gate lead is horizontally positioned on top of the hetero-doped structure. A via is located in the middle of the "C"-shaped metal patch, and the via and the gate lead are connected by an anode lead. The via connects the gate wiring layer to the metal microstructure layer, and the anode lead extends horizontally from the via.

[0031] Each cathode lead is connected to the same cathode bus, which has an external cathode connection terminal. Each anode lead is independent of the others. The cathode leads are all located on the surface of the dielectric substrate, and one end of the anode lead is connected to the HEMT gate lead. The lead passes through the dielectric substrate and the wiring substrate via a hole and is led out on the surface of the wiring substrate. By applying different bias voltages between the cathode and anode, the concentration of two-dimensional electron gas in the HEMT heterodoped structure is changed, thereby altering the resonant characteristics of the artificial microstructure and controlling the phase of the electromagnetic wave. Electromagnetic simulation results show that changing the electron gas concentration can control the resonant characteristics of the unit cell, achieving phase control of the terahertz beam. By changing the depth of the top and bottom edges of the resonant ring, the resonant frequency can be adjusted while maintaining the phase shift performance.

[0032] like Figure 4 As shown, the amplitude and phase shift characteristics of the switching state are represented by carrier concentrations of 0.1e16cm^-3 and 8e16cm^-3, respectively, under the premise that the phase shift unit is a complete circular ring and the clipping depth is 5um and 15um, respectively.

[0033] like Figure 5 As shown, the variation of the reflection coefficient and operating frequency band of the metasurface under different incident angles are displayed.

[0034] In summary, this invention integrates artificial microstructures (including metal microstructures and HEMTs) with HEMTs, combining the emission phase-shifting capability of artificial microstructures with the switching modulation capability of HEMTs to achieve rapid modulation of the terahertz reflection phase. This invention connects each microstructure unit to an independent anode lead by punching holes in the dielectric substrate, and forms a two-dimensional independent coded reflection array of subwavelength units in a two-dimensional array, thereby achieving free control of the far-field beam in three-dimensional directions.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A three-dimensional far-field beamforming encoding and modulation structure for terahertz waves, comprising a composite microstructure composed of a substrate, a metal base plate, a metal microstructure, and a HEMT arranged in a rectangular pattern in a two-dimensional plane, characterized in that: The composite microstructure's metal microstructure and HEMT are located on the substrate surface. The metal microstructure is a notched ring, and the HEMT is placed at the notch of the metal microstructure. The HEMT consists of a gate lead, a hetero-doped structure, a source electrode, and a drain electrode. The metal microstructure is provided with through holes. By routing the gate of the HEMT to the back of the reflective substrate, the interference of the lead wires on the reflection can be reduced. The three-dimensional far-field beam coding and control structure of the terahertz wave also includes: based on the switching control effect of the gate voltage on the HEMT, the HEMT of the microstructure array element is driven by N×N digital control voltages to produce a phase shift switching effect, thereby realizing the coding and control of the three-dimensional far-field beam of the terahertz wave by the composite microstructure. The substrate includes an upper substrate and a lower substrate. The upper substrate is used to load the metal microstructure and the metal base plate, and the lower substrate is used to arrange the anode leads of the reflective array. The top layer of the composite microstructure consists of a metal microstructure and an HEMT integrated on it. The two ends of the HEMT are connected to the metal microstructure and grounded through a cathode lead. The gate of the HEMT is connected to the pad of a metal via. Each metal microstructure has an independent anode lead connected to the back of the reflector array to achieve independent control. The metal microstructure is a C-shaped metal ring surrounding a pad of a metal via. The two ends of the C-shaped metal ring are connected to electronically controlled switching devices. Holes are drilled on the back of the unit for wiring to achieve independent coded control for each electronically controlled switching device.

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