A multi-frequency joint regulation method based on an asynchronous space-time coding metasurface

Abstract

The application discloses a kind of based on the multi-frequency joint regulation and control method for realization of asynchronous space-time coding metasurface. Specifically, by different regions of asynchronous space-time coding metasurface being applied with periodic signal with different modulation frequency, partition type asynchronous space-time coding metasurface can be constructed. Due to the difference of modulation frequency, the same order nonlinear harmonic generated by different partitions is different and does not affect each other. This characteristic lays the foundation for independently regulating the electromagnetic response of each partition. For any partition, by independently applying periodic modulation signal with different time delay and duty cycle to asynchronous space-time coding metasurface unit in the region, the amplitude and phase of the corresponding frequency can be effectively regulated. Accordingly, asynchronous space-time super coding surface contains several modulation partitions, which can jointly regulate several frequencies.

Description

Technical Field

[0001] This invention relates to a method for controlling multi-frequency electromagnetic waves and multi-frequency signals based on a partitioned asynchronous spatiotemporally encoded metasurface, belonging to the field of novel artificial electromagnetic metamaterials technology. Background Technology

[0002] Multi-frequency joint control is an essential capability for many wireless systems, including radar and wireless communication systems. For example, in wireless communication, frequency division multiplexing (FDM) mechanisms, introduced to increase channel capacity, modulate multi-stream information onto different carrier frequencies. Similarly, in radar systems, frequency control arrays need to set different radiation frequencies for different radiating elements and control multiple frequencies to suppress multipath effects. However, in existing wireless systems, the control of multi-carrier electromagnetic signals is all done in radio frequency (RF) circuits. RF circuit components, such as mixers, phase shifters, and amplifiers, are characterized by complex manufacturing processes, high costs, and high power consumption.

[0003] In recent years, spatiotemporally coded metasurfaces have received widespread attention and research due to their ability to jointly control the spectral and spatial spectra of electromagnetic waves. Studies have found that, under default RF circuitry, spatiotemporally coded metasurfaces can control any first-order harmonic. However, because the entire spatiotemporally coded metasurface samples the same modulation frequency, a natural harmonic relationship (multi-frequency entanglement) exists between the generated nonlinear frequencies. This harmonic relationship makes it difficult for spatiotemporally coded metasurfaces to achieve multi-frequency joint control. To overcome this limitation, asynchronous spatiotemporally coded metasurfaces have been proposed. Unlike spatiotemporally coded metasurfaces operating in a synchronous architecture, asynchronous spatiotemporally coded metasurfaces have different modulation frequencies in different regions. These different modulation frequencies make the nonlinear harmonics generated by each region independent, thus laying the foundation for multi-frequency joint control. However, a specific method for achieving multi-frequency joint control using asynchronous spatiotemporally coded metasurfaces has not yet been proposed. Summary of the Invention

[0004] Technical issues:

[0005] The technical problem this invention aims to solve is to provide a multi-frequency joint control method based on an asynchronous spatiotemporally coded metasurface under default RF link conditions. Specifically, under single-carrier electromagnetic wave incident conditions, control signals with different modulation frequencies are applied to different regions of the metasurface to construct a partitioned asynchronous spatiotemporally coded metasurface. Since different partitions have different modulation frequencies, the frequencies generated by the metasurface are free from harmonic entanglement, thus effectively decoupling the joint control of multiple frequency signals. In any modulation frequency partition, the phase and amplitude of a frequency signal can be controlled by adjusting the time delay and duty cycle of the control signal within the partition. Therefore, the entire partitioned asynchronous spatiotemporally coded metasurface can achieve joint control of multiple frequency signals.

[0006] From an application perspective, a method for controlling multi-frequency electromagnetic waves and multi-frequency signals based on a partitioned asynchronous spatiotemporally coded metasurface can further realize joint control of multi-frequency radiation patterns and a new type of wireless communication system with frequency division multiplexing characteristics. Therefore, this invention has potential application value in both wireless communication and radar fields.

[0007] Technical solution:

[0008] To address the aforementioned technical problems, this invention proposes a multi-frequency joint modulation method based on an asynchronous spatiotemporally coded metasurface, comprising the following steps: dividing the asynchronous spatiotemporally coded metasurface into partitions, each partition including several asynchronous spatiotemporally coded metasurface units, and independently modulating one frequency in each partition; achieving joint modulation of multiple frequencies by jointly controlling multiple frequencies across multiple partitions to realize the joint modulation of multi-frequency electromagnetic waves and signals. The modulation frequencies within different partitions of the asynchronous spatiotemporally coded metasurface are inconsistent, resulting in inconsistent and independently selectable nonlinear harmonic frequencies generated by different partitions. Furthermore, the size and shape of the metasurface modulation frequency partitions possess reconfigurable characteristics.

[0009] Preferably, the step of partitioning and controlling a frequency includes: controlling the frequency amplitude by adjusting the duty cycle of the modulation waveform; and controlling the frequency phase by introducing a time delay into the modulation waveform.

[0010] Preferably, different zones are controlled by periodic signals with different modulation frequencies.

[0011] Preferably, the periodic signal is generated by a control circuit, which includes a field-programmable gate array (FPGA), a digital-to-analog converter (DAC), and an amplifier module (Amplifier), and is capable of outputting a time-varying voltage waveform of any period.

[0012] Preferably, the asynchronous spatiotemporal coded metasurface comprises N subwavelength artificial electromagnetic units arranged in a periodic manner; each subwavelength artificial electromagnetic unit comprises an active control element; by applying different voltages to the two ends of the active control element, the reflection phase of the subwavelength artificial electromagnetic unit to the spatial electromagnetic wave can be changed in real time, and the phase agility rate is greater than 10kHz.

[0013] Preferably, the size and shape of each partition of the asynchronous spatiotemporal coded metasurface are reconfigurable through software definition.

[0014] Preferably, the asynchronous spatiotemporal coded metasurface unit includes two pin diodes and two varactor diodes. By adjusting the voltage applied across the two varactor diodes from 0V to 14V, it is possible to achieve a reflection amplitude fluctuation of less than 3dB at a frequency of 4.25GHz, while the unit's reflection phase coverage range is greater than 360°.

[0015] Preferably, the joint control of multiple frequency patterns can be achieved based on the partitioned asynchronous spatiotemporal coding metasurface.

[0016] Preferably, frequency division multiplexing technology based on partitioned asynchronous spatiotemporal coded metasurface can be realized in wireless communication systems, enabling simultaneous transmission of multiple streams of information under multi-carrier conditions.

[0017] The present invention also provides a wireless communication transmitter based on an asynchronous spatiotemporal coded metasurface, which uses the above-mentioned multi-frequency joint modulation method to simultaneously modulate multi-stream information onto multiple carrier frequencies and transmit it into free space.

[0018] The present invention also provides a wireless communication system, characterized in that it includes the transmitter and multi-antenna wireless communication receiver described above.

[0019] Beneficial effects:

[0020] 1. The frequencies generated by the partitioned asynchronous spatiotemporal coded metasurface do not suffer from the harmonic entanglement problem found in traditional spatiotemporal coded metasurfaces, thus effectively decoupling the problem of multi-frequency signal combination;

[0021] 2. Under the condition of the default radio frequency circuit in a traditional wireless system, the partitioned asynchronous spatiotemporal coded metasurface can easily realize the generation and control of multi-carrier signals;

[0022] 3. Partitioned asynchronous spatiotemporal coded metasurfaces can achieve joint control of multi-frequency radiation patterns;

[0023] 4. Partitioned asynchronous spatiotemporal coded metasurfaces can be used to construct wireless communication systems with frequency division multiplexing capabilities, enabling simultaneous transmission of multiple streams of signals across multiple carrier frequencies;

[0024] 5. Compared with traditional multi-frequency generation and control systems implemented using circuits (such as radar frequency control arrays and frequency division multiplexing technology for wireless communication), the present invention has a simple hardware structure, low cost, and does not require local oscillator sources, phase shifters, amplifiers, or other related RF components. Based on the method of the present invention, multi-frequency joint beamforming function has been successfully realized, and a wireless communication system with frequency division multiplexing function has been successfully built. Attached Figure Description

[0025] Figure 1 This is a conceptual diagram illustrating the enabling of multi-frequency modulation in the method of this invention.

[0026] Figure 2 This invention presents a partitioned asynchronous spatiotemporal coded metasurface unit and curves showing the variation of its reflection phase and amplitude with bias voltage at 4.25 GHz.

[0027] Figure 3 Multiple carrier signals are generated based on a partitioned asynchronous spatiotemporal coded metasurface. (ab) The partitioned asynchronous spatiotemporal coded metasurface generates two frequency signals; (cd) The partitioned asynchronous spatiotemporal coded metasurface generates eight frequency signals.

[0028] Figure 4 Two frequency signals can be simultaneously modulated based on a partitioned asynchronous spatiotemporal coding metasurface.

[0029] Figure 5 Joint modulation of multi-frequency signal radiation patterns based on partitioned asynchronous spatiotemporal coding metasurface.

[0030] Figure 6 A partitioned asynchronous spatiotemporal coding metasurface enables simultaneous transmission of 8 carrier frequencies and 8 streams of information. Detailed Implementation

[0031] This embodiment provides a method for controlling multi-frequency electromagnetic waves and multi-frequency signals based on a partitioned asynchronous spatiotemporal coded metasurface. Its conceptual implementation diagram is shown below. Figure 1 As shown. The method employs an asynchronous spatiotemporal coded metasurface. In this embodiment, the asynchronous spatiotemporal coded metasurface specifically consists of 8 × 16 elements. Figure 2 As shown on the left, each unit contains two pin diodes and two varactor diodes. By adjusting the voltage applied across the two varactor diodes from 0V to 14V, it can be ensured that at the 4.25GHz frequency point, the reflection amplitude fluctuation is less than 3dB, while the unit's reflection phase coverage is greater than 360° (see...). Figure 2(Right side) In this invention, different partitions of the asynchronous spatiotemporal coded metasurface have different modulation frequencies. Therefore, there is no harmonic entanglement problem between the nonlinear harmonics generated in different partitions. Each modulation frequency partition is responsible for controlling one frequency, thereby effectively decoupling the problem of multi-frequency joint control and realizing the joint control of multi-frequency signals under a single incident frequency. For any region, the energy distribution of the reflected frequency spectrum can be effectively controlled by adjusting the control signal waveform. To enable a partition to efficiently generate a target frequency f c +f1, where f c f1 represents the incident wave frequency, and f1 represents the modulation frequency. The control waveform should make the reflection phase of this partition change linearly from 0° to 360° within a certain time period to ensure that the unit reflection frequency is completely shifted from the incident wave carrier frequency to the first harmonic. For example Figure 3 As shown in (a), two columns in the center of the metasurface are selected, and waveforms with different modulation frequencies are applied to them respectively, so that two nonlinear frequencies are efficiently generated. The corresponding baseband reflection spectrum is as follows. Figure 3 As shown in (b). Further, as... Figure 3 As shown in (cd), the metasurface is divided into eight different modulation frequency zones, each of which efficiently generates a nonlinear frequency.

[0032] For the joint modulation of multi-frequency signals, taking dual-frequency modulation and 1-bit phase encoding as an example. Figure 4 As shown, the present invention can independently control the amplitude and phase of the frequency signal in the corresponding region by adjusting the time delay and duty cycle of the modulation waveform in any partition.

[0033] On the asynchronous spatiotemporal coded metasurface, cells in the same column are modulated by the same control signal, while the modulation signals between columns are independent of each other. The control signal is generated by the FPGA, output by the DAC module, amplified by the Amplifier, and finally applied to the asynchronous spatiotemporal coded metasurface in the form of a corresponding voltage (which can generate the corresponding voltage of the target reflection phase).

[0034] In this invention, a partitioned asynchronous spatiotemporal coded metasurface is used to realize multi-frequency directions.

[0035] Example 1:

[0036] The diagram shows joint regulation. For example, such as... Figure 5 As shown in (ab), firstly, by applying control signals with different modulation frequencies to the left and right halves of the metasurface, two modulation frequency partitions are generated on the metasurface. Each partition controls a nonlinear frequency f1 and f2, respectively. By introducing different phase gradients to partitions f1 and f2, the radiation patterns of the two regions can be independently controlled (see...). Figure 5 (ab)). Furthermore, with the phase gradients of partitions f1 and f2 remaining unchanged, the shape of the partitions is reconstructed (see...). Figure 5 (cd) can change the beam pointing of the scattering pattern. Furthermore, by adding modulation frequency partitions to the metasurface, the number of controllable multi-frequency patterns can be increased. Figure 5 (ef) respectively demonstrates the joint modulation of four- and eight-frequency radiation patterns based on partitioned asynchronous spatiotemporal coded metasurfaces.

[0037] Example 2:

[0038] In this invention, an asynchronous spatiotemporally coded metasurface capable of generating and modulating multi-frequency signals can be used as a transmitter to construct a wireless communication architecture with frequency division multiplexing characteristics. For example, firstly, the asynchronous spatiotemporally coded metasurface is divided into eight partitions with different modulation frequencies, such as... Figure 6 As shown in (a). To improve the efficiency of generating nonlinear frequencies in each partition, the control waveform used across the entire array allows the reflected phase to linearly change from 0° to 360° within a certain time period, ensuring that the incident frequency is completely shifted to the first harmonic. The communication modulation scheme used in this invention is Quadrature Phase Shift Keying (QPSK). Therefore, four time delays need to be introduced into the control waveform to ensure that the generated signal has four phase states (0°, 90°, 180°, 270°). The eight nonlinear frequencies generated by the metasurface can be independently and flexibly controlled. Therefore, under eight carrier frequencies, the asynchronous spatiotemporally coded metasurface can simultaneously modulate eight streams of information to transmit eight different information streams. The eight-stream constellation diagram at the receiver is shown below. Figure 6 As shown in (bi), a wireless communication framework with frequency division multiplexing characteristics has been successfully constructed based on the partitioned asynchronous spatiotemporal coded metasurface.

Claims

1. A multi-frequency joint control method based on asynchronous spatiotemporal coded metasurfaces, characterized in that, The process includes the following steps: partitioning the asynchronous spatiotemporal coded metasurface into several asynchronous spatiotemporal coded metasurface units, with each partition independently controlling a frequency; and achieving joint control of multi-frequency electromagnetic waves and signals by jointly controlling multiple frequencies through multiple partitions. The step of partitioning and controlling a frequency includes: controlling the frequency amplitude by adjusting the duty cycle of the modulation waveform; and controlling the frequency phase by introducing a time delay into the modulation waveform. The asynchronous spatiotemporal coded metasurface comprises N subwavelength artificial electromagnetic units arranged in a periodic manner; each subwavelength artificial electromagnetic unit contains an active control element; by applying different voltages to the two ends of the active control element, the reflection phase of the subwavelength artificial electromagnetic unit to the spatial electromagnetic wave can be changed in real time, with a phase agility rate greater than 10 kHz.

2. The multi-frequency joint control method based on asynchronous spatiotemporal coded metasurfaces according to claim 1, characterized in that, Different zones are controlled by periodic signals with different modulation frequencies.

3. The multi-frequency joint control method based on asynchronous spatiotemporal coded metasurfaces according to claim 2, characterized in that, The periodic signal is generated by a control circuit, which includes a field-programmable gate array (FPGA), a digital-to-analog converter (DAC), and an amplifier module (Amplifier), and is capable of outputting a time-varying voltage waveform of any period.

4. The multi-frequency joint control method based on asynchronous spatiotemporal coded metasurface as described in claim 1, characterized in that, The size and shape of each partition of the asynchronous spatiotemporal coded metasurface can be reconfigured through a software-defined approach.

5. The multi-frequency joint control method based on asynchronous spatiotemporal coded metasurface as described in claim 1, characterized in that, The asynchronous spatiotemporal coded metasurface unit includes two pin diodes and two varactor diodes. By adjusting the voltage applied across the two varactor diodes from 0V to 14V, it is possible to achieve a reflection amplitude fluctuation of less than 3dB at a frequency of 4.25GHz, while the unit's reflection phase coverage range is greater than 360°.

6. A wireless communication transmitter based on an asynchronous spatiotemporally coded metasurface, characterized in that, By employing the multi-frequency joint control method described in any one of claims 1-5, multi-stream information can be simultaneously modulated onto multiple carrier frequencies and transmitted into free space.

7. A wireless communication system, characterized in that, include: The transmitter and multi-antenna wireless communication receiver as described in claim 6.

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