A metasurface that generates frequency modulated continuous waves

Abstract

The present invention discloses a metasurface for generating frequency modulated continuous waves, comprising: n*n basic units, n columns of column sub-arrays composed of the basic units, and each column sub-array is provided with the same periodic nonlinear control voltage signal by the control link part of the metasurface. By carefully designing different types of nonlinear control voltage signals, the metasurface in the present invention can generate a variety of different types of linear and nonlinear frequency modulated continuous waves; by changing the initial phase distribution of the metasurface array, the metasurface in the present invention can also perform beam control on the frequency modulated continuous waves. Compared with the traditional frequency modulated continuous wave generating device, the present invention realizes the generation and beamforming functions of frequency modulated continuous waves only through periodic nonlinear control voltage signals. It has a simple principle, a simple architecture, low cost, is easy to integrate, and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of time domain frequency modulation waveform generation and novel artificial electromagnetic materials, and in particular relates to a super surface for generating multiple linear and nonlinear frequency modulation continuous waves. Background Art

[0002] Various types of FM signals are widely used in pulse compression technology, so FM signal generators are a very important part of modern radar systems. The core of traditional FM signal generators is a voltage-controlled oscillator (VCO) or a direct digital synthesizer (DDS), and often requires a series of peripheral circuits, which leads to high hardware costs and relatively complex structures. In addition, when the generated FM signal needs to be radiated externally, the system also requires some antenna feed equipment, and the system integration is not high. Summary of the invention

[0003] The purpose of the present invention is to provide a metasurface for generating frequency modulated continuous waves, which can generate a variety of linear and nonlinear frequency modulated continuous waves and has a real-time beam control function, and can be used to solve the technical problems of high hardware cost, relatively complex structure and low integration of traditional frequency modulated continuous wave generator systems.

[0004] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0005] A metasurface for generating frequency modulated continuous waves comprises: n*n basic units, n columns of column sub-arrays composed of basic units located in the same column, each column sub-array being provided with the same periodic nonlinear control voltage signal by the control link part of the metasurface; the basic unit comprises three layers: the first layer is a metal pattern layer welded with two identical varactor diodes, the second layer is a dielectric substrate layer, and the third layer is a full metal layer without etched patterns; the first layer and the third layer are connected by a metal through hole running through the entire basic unit, two varactor diodes are respectively fed by two parts of metal patches bridged by them, and the control voltage signals fed to them are the same.

[0006] Furthermore, the basic unit material is a F4B (polytetrafluoroethylene glass fiber cloth) dielectric substrate (dielectric constant 2.2, loss tangent 0.0015) with copper foil on both sides.

[0007] Furthermore, the control link part of the metasurface is composed of a field programmable gate array FPGA, a digital-to-analog conversion module DAC and an amplifier circuit module; the control link part generates a periodic arbitrary nonlinear control voltage signal that varies with time in the range of 0 to 19V.

[0008] Furthermore, when the voltage value of the control voltage signal changes continuously within the range of 0 to 19 V, the metasurface reflects electromagnetic waves with continuously changing phases within the frequency band of 2.35 to 2.7 GHz, and the phase change range exceeds 360°.

[0009] Furthermore, the first metal pattern layer and the third full metal layer of the column sub-array are integrated, all basic units of the same column sub-array share the same control voltage signal, and the control voltage signals of different column sub-arrays have the same form, but their voltage initial values ​​are different.

[0010] The metasurface for generating frequency modulated continuous waves of the present invention has the following advantages:

[0011] 1. The present invention designs a metasurface that generates frequency modulated continuous waves, including: n*n basic units, n columns of column sub-arrays composed of basic units located in the same column, and each column sub-array is provided with the same periodic nonlinear control voltage signal by the control link part of the metasurface. The basic unit is made of F4B (polytetrafluoroethylene glass fiber cloth) dielectric substrate (dielectric constant 2.2, loss tangent 0.0015) with copper foil on both sides, and the unit structure includes 3 layers: the first layer is a metal pattern layer welded with two identical varactor diodes, the second layer is a dielectric substrate layer, and the third layer is a full metal layer without etched patterns. The first layer and the third layer are connected by a metal through hole that runs through the entire unit, and the two diodes are fed by two parts of the metal patches bridged by them, and the control voltage signals fed to them are the same. It has a simple principle, a simple architecture, and low cost;

[0012] 2. The control link part of the metasurface proposed in the present invention is composed of a field programmable gate array FPGA, a digital-to-analog conversion module DAC and an amplifier circuit module; the control link part generates a periodic arbitrary nonlinear control voltage signal that varies with time in the range of 0 to 19V. The metasurface can generate a variety of linear and nonlinear frequency-modulated continuous waves by simply constructing the corresponding periodic nonlinear control voltage signal, with strong waveform reconfigurability and convenient switching;

[0013] 3. The metasurface column subarray proposed by the present invention has the first metal pattern layer and the third full metal layer integrated, and all basic units of the same column subarray share the same control voltage signal. The control voltage signals of different column subarrays have the same form, but their initial voltage values ​​are different. The direction of the frequency modulated continuous wave beam can be changed by changing the distribution of the initial voltage value, and it has a certain frequency modulated continuous wave beam control capability;

[0014] 4. In summary, the metasurface designed in the present invention can generate a variety of linear and nonlinear frequency modulated continuous waves, and has real-time beam control function. It can replace the VCO, DDS, antenna and other components required by the traditional frequency modulated continuous wave generator system, making the system more integrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the metasurface of the present invention generating frequency modulated continuous waves and realizing beamforming;

[0016] Figure 2 (a) is a nonlinear reflection phase response diagram required for the metasurface of the present invention to generate a linear frequency modulated continuous wave;

[0017] Figure 2 (b) Figure 2 (a) Schematic diagram of the baseband waveform of the linear frequency modulated continuous wave generated by the metasurface with nonlinear reflection phase response, where the baseband waveform is a waveform generated by mixing the actual waveform with the incident frequency signal;

[0018] Figure 3 (a) is a nonlinear reflection phase response diagram required for the metasurface of the present invention to generate a polynomial nonlinear frequency modulated continuous wave;

[0019] Figure 3 (b) Figure 3 (a) Schematic diagram of the baseband waveform of the polynomial nonlinear frequency modulated continuous wave generated by the metasurface with nonlinear reflection phase response, where the baseband waveform is a waveform generated by mixing the actual waveform with the incident frequency signal;

[0020] Figure 4 (a) is a nonlinear reflection phase response diagram required for the metasurface of the present invention to generate a sinusoidal nonlinear frequency modulated continuous wave;

[0021] Figure 4 (b) Figure 4 (a) is a schematic diagram of the baseband waveform of a sinusoidal nonlinear frequency modulated continuous wave generated by a metasurface with a nonlinear reflection phase response, wherein the baseband waveform is a waveform diagram generated by mixing the actual waveform with the incident frequency signal;

[0022] Figure 5 (a) is a schematic diagram of a basic unit of a super surface in the present invention;

[0023] Figure 5 (b) is a reflection amplitude response curve diagram of the metasurface basic unit in the present invention under different control voltages;

[0024] Figure 5 (c) is a reflection phase response curve diagram of the metasurface basic unit in the present invention under different control voltages;

[0025] Figure 5 (d) is a graph showing the measured reflection amplitude and phase of the metasurface changing with the control voltage at an operating frequency of 2.6 GHz;

[0026] Figure 5 (e) is a physical picture of the super surface in the present invention;

[0027] Figure 5 (f) is a physical diagram of the architecture of the frequency modulated continuous wave system based on the metasurface;

[0028] Figure 6 (a) is a baseband waveform diagram of ten cycles of the measured linear frequency modulation continuous wave generated by the metasurface of the present invention;

[0029] Figure 6 (b) From Figure 6 (a) is a baseband waveform diagram of a period length;

[0030] Figure 6 (c) for Figure 6 (b) The corresponding measured baseband time-frequency curve of linear frequency modulation continuous wave;

[0031] Figure 7 (a) is the theoretical and measured scattering patterns of polynomial nonlinear frequency modulated continuous waves generated by the metasurface of the present invention;

[0032] Figure 7 (b) is the theoretical and measured scattering pattern of dual-sine nonlinear frequency modulated continuous waves generated by the metasurface of the present invention;

[0033] Figure 7 (c) is the theoretical and measured scattering pattern of the “S” type nonlinear frequency modulated continuous wave generated by the metasurface of the present invention;

[0034] Figure 7 (d) for Figure 7 (a) The corresponding measured baseband time-frequency curve of polynomial nonlinear frequency modulated continuous wave;

[0035] Figure 7 (e) Figure 7 (b) The corresponding measured baseband time-frequency curve of dual-sine nonlinear frequency modulated continuous wave;

[0036] Figure 7 (f) Figure 7 (c) The corresponding measured baseband time-frequency curve of the “S” type nonlinear frequency modulated continuous wave. DETAILED DESCRIPTION

[0037] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a metasurface for generating a frequency modulated continuous wave according to the present invention in conjunction with the accompanying drawings.

[0038] like Figure 1 As shown, the present invention discloses a metasurface for generating frequency modulated continuous waves, comprising: n*n basic units, n columns of column sub-arrays composed of basic units, each column sub-array being provided with the same periodic nonlinear control voltage signal by the control link part of the metasurface. The metasurface can generate a variety of linear and nonlinear frequency modulated continuous waves, and has a real-time beam steering function.

[0039] The control voltage signal of the metasurface in the present invention is a nonlinear voltage signal with a period of T. Figure 4 (d) shows the relationship between the measured reflection phase of the metasurface and the control voltage. When a single-frequency electromagnetic wave is incident on the metasurface, the phase of the reflected wave is also a nonlinear periodic function: in yes part within a cycle. Requirements: When m=±1,±2,±3…(i.e. m is a non-zero integer), the reflected wave has phase continuity. Therefore, the instantaneous frequency f(t) of the reflected wave can be obtained: where f c is the incident wave frequency, f0(t) is the baseband time-frequency function, express The derivative of the reflected wave with respect to time t is a frequency modulated continuous wave modulated at the frequency of the incident wave. By changing the form of the periodic nonlinear control voltage signal, the in the form of frequency modulated continuous waves of different types. Figure 2 (a) is the nonlinear reflection phase response required for the metasurface to generate linear frequency modulated continuous waves in the present invention: 0≤t≤T (the illustration shows the baseband time-frequency relationship of the frequency modulated continuous wave after down-conversion: 0≤t≤T), Figure 2 (b) A schematic diagram showing the corresponding baseband waveform of the linear frequency modulated continuous wave; Figure 3 (a) is the nonlinear reflection phase response required for the metasurface in the present invention to generate a polynomial nonlinear frequency modulated continuous wave: 0≤t≤T (the illustration shows the baseband time-frequency relationship of the frequency modulated continuous wave after down-conversion: 0≤t≤T), Figure 3 (b) A schematic diagram showing the baseband waveform of the corresponding polynomial-type linear frequency modulation continuous wave; Figure 4(a) is the nonlinear reflection phase response required for the metasurface in the present invention to generate a sinusoidal nonlinear frequency modulated continuous wave: 0≤t≤T (the illustration shows the baseband time-frequency relationship of the frequency modulated continuous wave after down-conversion: 0≤t≤T), Figure 4 (b) Schematic diagram showing the corresponding baseband waveform of the sinusoidal nonlinear frequency modulated continuous wave.

[0040] When all the columns of the metasurface in the present invention are fed with the same control voltage signal by the control link part of the metasurface, the metasurface reflects a frequency modulated continuous wave in its normal direction. Furthermore, by changing the initial voltage value of each column of the control voltage signal without changing the form of the control voltage signal of each column of the metasurface array, an initial phase distribution can be formed on the metasurface array, so that the metasurface has the beamforming function of the frequency modulated continuous wave. When a certain initial phase encoding is applied to a metasurface with n columns and a column spacing of d, the beam of the frequency modulated continuous wave reflected by it will deviate from the normal direction, and its angle θ c It can be expressed as: where c is the speed of light, is the phase difference between adjacent codes. The value of can realize the dynamic beam scanning function of FMCW, and its effect is as follows Figure 1 shown.

[0041] The metasurface for generating frequency modulated continuous waves proposed by the present invention is formed by periodically arranging its basic units. Figure 5 As shown in (a), the basic unit material is a F4B (polytetrafluoroethylene fiberglass cloth) dielectric substrate (dielectric constant 2.2, loss tangent 0.0015) with copper foil on both sides. The unit structure consists of 3 layers: the first layer is a metal pattern layer with two identical varactor diodes welded on it, the second layer is a dielectric substrate layer, and the third layer is a full metal layer without etched patterns. The first and third layers are connected by a metal through hole that runs through the entire unit. The two diodes are fed by two parts of the metal patches that are bridged by them, and the control voltage signals fed to them are the same. The specific physical dimensions of the unit are: P a =15mm, P b =23.8mm, w1=4mm, w2=5.5mm, D via =0.5mm, d=3mm, e=1mm, h=4mm; Varactor diode model: SMV-1405. After full-wave simulation and analysis, Figure 5 (b) and (c) respectively give the simulated reflection amplitude and phase responses of the unit: within the control voltage range of 0 to 19 V, the unit's reflection phase changes by more than 360° in the frequency range of 2.35 to 2.7 GHz. Figure 5(d) shows the curve of the measured metasurface amplitude and phase changing with the control voltage at 2.6 GHz: at 2.6 GHz, when the voltage changes continuously from 0 V to 19 V, the phase of the reflected wave of the metasurface has a continuous change range of more than 360°.

[0042] Furthermore, the actual structure of the system architecture for generating frequency modulated continuous waves using the metasurface of the present invention is shown in FIG. Figure 5 (f) shows the actual image of the metasurface in the system. Figure 5 As shown in (e), the control platform provides a corresponding programmable control voltage signal to each column of the metasurface, and the signal source provides a 2.6 GHz incident wave to the feed antenna located in the normal direction of the metasurface. When the metasurface is irradiated by the incident wave, the metasurface generates a corresponding type of frequency modulated continuous wave, which is Figure 5 (f) The receiving antenna on the right receives and transmits the signal to the software radio platform, which demodulates and recovers the FM continuous wave baseband waveform. Figure 6 (a) and (b) are the baseband waveforms of the linear frequency modulated continuous wave with a measured length of ten cycles (100 microseconds) and a length of one cycle (10 microseconds), respectively, generated by the metasurface of the present invention. Figure 6 (c) shows the baseband time-frequency curve of the corresponding linear frequency modulated continuous wave within a period length (10 microseconds), where the time-frequency relationship is: f0(t) = 10 11 ·t(Hz),75μs≤t≤85μs. In addition, Figure 7 The ability to generate nonlinear frequency modulated continuous waves and beamforming using metasurfaces has been experimentally demonstrated: Figure 7 (a) shows the scattering pattern of the polynomial nonlinear frequency modulated continuous wave, with the maximum beam direction at -37.3°. Figure 7 (d) shows the corresponding baseband time-frequency curve: f0(t) = 1.5 16 .t 2 (Hz), 0≤t≤10μs; Figure 7 (b) shows the scattering pattern of the double-sine nonlinear frequency modulated continuous wave, with the maximum beam direction at 0°. Figure 7 (e) shows the corresponding baseband time-frequency curve: f0(t) = 2.5 × 10 5 [cos(2×10 5 πt)+2cos(4×10 5 πt)](Hz),0≤t≤10μs; Figure 7 (c) shows the scattering pattern of the “S” type nonlinear frequency modulated continuous wave, with the maximum beam direction at +37.3°. Figure 7 (f) shows the corresponding baseband time-frequency curve: f0(t) = 10 11 ·t+5×10 5cos(2×10 5 πt)(Hz),0≤t≤10μs. The test results of the directional pattern match the simulation results very well, demonstrating its beamforming capability. The burr phenomenon in the measured results is mainly caused by the electromagnetic interference of the environment and the mismatch of the receiver sampling rate, but it does not affect the theoretical and practical value of the proposed solution.

[0043] In summary, the metasurface provided by the present invention realizes the generation of frequency modulated continuous waves and beamforming functions only through periodic nonlinear control voltage signals. It has a simple principle, a simple architecture, low cost, is easy to integrate, and has broad application prospects.

[0044] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A metasurface for generating frequency modulated continuous waves, characterized in that: include: There are n*n basic units, and n columns of column sub-arrays composed of basic units located in the same column. Each column sub-array is provided with the same periodic nonlinear control voltage signal by the control link part of the metasurface. The basic unit contains 3 layers: the first layer is a metal pattern layer welded with two identical varactor diodes, the second layer is a dielectric substrate layer, and the third layer is a full metal layer without etched patterns. The first layer and the third layer are connected by a metal through hole running through the entire basic unit, and the two varactor diodes are fed by two parts of metal patches bridged by them respectively. The first metal pattern layer and the third full metal layer of the basic unit in the same column sub-array are integrated, and all the basic units in the column share the same control voltage signal. The control voltage signals of different column sub-arrays have the same form, but their initial voltage values ​​are different.

2. The metasurface for generating frequency modulated continuous waves according to claim 1, characterized in that: The basic unit material is a polytetrafluoroethylene glass fiber cloth dielectric substrate with copper foil on both sides, wherein the dielectric constant is 2.2 and the loss tangent is 0.0015.

3. The metasurface for generating frequency modulated continuous waves according to claim 1, characterized in that: The control link part of the metasurface is composed of a field programmable gate array FPGA, a digital-to-analog conversion module DAC and an amplifier circuit module; the control link part generates a periodic arbitrary nonlinear control voltage signal that varies with time within the range of 0 to 19V.

4. The metasurface for generating frequency modulated continuous waves according to claim 1, characterized in that: When the voltage value of the control voltage signal changes continuously within the range of 0 to 19V, the metasurface reflects electromagnetic waves with continuously changing phases within a frequency band of 2.35 to 2.7GHz, and the phase change range exceeds 360°.

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