A method for implementing non-reciprocal nonlinear transmission based on metasurface cascade
By utilizing the cascaded metasurface technology and the synergistic control of gain metasurfaces and time-modulated metasurfaces, non-reciprocal transmission in both amplitude and frequency dimensions is achieved. This solves the problems of high loss and complex structure in traditional non-reciprocal transmission methods and is applicable to the fields of intelligent communication and information security.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-05-19
- Publication Date
- 2026-07-10
AI Technical Summary
Traditional non-reciprocal transmission methods suffer from high losses, complex structures, and limited linear response, making it difficult to meet the miniaturization, integration, and low power consumption requirements of next-generation communication and sensing systems.
Gain metasurfaces and time-modulated metasurfaces are fabricated using a metasurface cascade method. Nonlinear gain and harmonic characteristics are controlled by bias voltage to achieve non-reciprocal transmission in both amplitude and frequency dimensions. The method employs all-electric bias without the need for magnetic bias or complex mechanical structures.
It achieves low-loss, high-integration, and flexible non-reciprocal transmission, breaking through the single-dimensional limitations of traditional methods and is suitable for multi-dimensional control in complex scenarios.
Smart Images
Figure CN122370732A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electromagnetic transmission technology, and in particular to a method for realizing non-reciprocal nonlinear transmission based on metasurface cascades. Background Technology
[0002] Electromagnetic non-reciprocal transmission is a core fundamental function of modern electromagnetic systems. It refers to the significantly asymmetric transmission characteristics of electromagnetic waves when propagating in the forward and reverse directions within the same transmission structure. It is widely used in microwave and millimeter-wave communication, radar detection, information encryption, non-reciprocal devices, topological photonic systems, and quantum information processing. Traditional techniques for achieving non-reciprocal transmission mainly rely on the magneto-optical effect, breaking the time-reversal symmetry of materials by applying an external magnetic field to achieve unidirectional transmission. While these methods are technically mature, they require rare-earth magnetic materials and complex bias magnetic field structures, resulting in drawbacks such as large size, low integration, high loss, and incompatibility with planar circuits. These limitations fail to meet the miniaturization, integration, and low-power consumption requirements of next-generation communication and sensing systems.
[0003] To overcome dependence on magnetic fields, non-magnetic non-reciprocal schemes based on time modulation, nonlinear effects, and spatially asymmetric structures have emerged in recent years. Time-modulated non-reciprocal techniques break time invariance by periodically changing structural parameters, enabling unidirectional transmission and frequency conversion. However, these modulation systems are highly complex, suffer from large insertion losses, and mostly only support linear responses, making it difficult to balance signal amplification and noise suppression. Non-reciprocal schemes based on passive nonlinear materials utilize power-dependent transmission characteristics to achieve unidirectional isolation, but they suffer from high power thresholds, slow response speeds, poor stability, and narrow bandwidths. Furthermore, they cannot simultaneously control amplitude and frequency characteristics, making it difficult to meet the high-precision non-reciprocal control requirements in complex scenarios.
[0004] Therefore, developing a method that is simple in structure, easy to control, and stable in performance, and can simultaneously achieve nonlinear, dual-dimensional, and low-loss non-reciprocal transmission, is of great significance for promoting the development of next-generation intelligent communication, radar stealth, and one-way encryption technologies. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a non-reciprocal nonlinear transmission method based on metasurface cascades. This method solves the problems of high loss, complex structure, and limited linear response in traditional non-reciprocal transmission methods, achieving non-reciprocal transmission in both amplitude and frequency dimensions without magnetic bias. It also has the advantages of flexible control and compact structure.
[0006] The objective of this invention is achieved through the following technical solution: a method for realizing non-reciprocal nonlinear transport based on metasurface cascades, comprising the following steps: (1) Preparation of gain metasurface and nonlinear gain tuning: The gain metasurface of integrated tunnel diode is prepared, the negative conductance of tunnel diode is adjusted by DC bias voltage, the bias voltage range corresponding to nonlinear gain is tested and determined, and the nonlinear decay characteristics of gain with incident power are verified. (2) Time-modulated metasurface fabrication and harmonic modulation: a time-modulated metasurface integrating dual PIN diodes is fabricated. The switching state of the PIN diodes is controlled by the bias voltage, and a periodic modulation sequence is applied to realize the generation of comb-shaped harmonics and the selective enhancement of specific order harmonics. (3) Dual metasurface cascade construction: The time modulation metasurface and the gain metasurface are cascaded without gaps along the electromagnetic wave propagation direction. Port 1 is defined as the outer side of the time modulation metasurface and port 2 is defined as the outer side of the gain metasurface, forming a forward propagation path from port 1 to port 2 and a reverse propagation path from port 2 to port 1. (4) Non-reciprocal nonlinear transmission control: By controlling the nonlinear gain of the gain metasurface and the harmonic characteristics of the time modulation metasurface through bias voltage, the difference in power loss and the difference in harmonic-gain matching order in the forward and reverse propagation paths are used to realize amplitude non-reciprocal transmission and frequency non-reciprocal transmission respectively. (5) Performance verification: Test the bidirectional transmission spectrum, harmonic amplification characteristics and nonlinear signal processing capabilities of the cascaded system to realize non-reciprocal nonlinear transmission.
[0007] Furthermore, the gain metasurface in step (1) adopts a three-layer substrate architecture, including two dielectric substrates and one intermediate bonding layer, with the dielectric substrate having a relative permittivity of [missing information]. ,thickness Relative permittivity of bonding layer ,thickness The top and bottom layers are printed with copper metal patches, which are coupled through copper vias to form a resonant cavity. A tunnel diode is embedded in the resonant cavity to introduce negative conductivity. .
[0008] Furthermore, in step (1), the bias voltage range corresponding to the nonlinear gain is 85~125mV, corresponding to the negative differential resistance of the tunnel diode. The gain metasurface forms a gain peak with a bandwidth of 30MHz at 4.88GHz; the nonlinear attenuation characteristic is that the gain is about 14dB when the incident power is -25dBm, and the gain drops to below 3dB when the incident power increases to 10dBm.
[0009] Furthermore, in step (2), the three-layer substrate structure of the time-modulated metasurface is consistent with that of the gain metasurface. The side length of the top metal patch is 14.4 mm. The dual-PIN diodes are independently controlled by the bias voltage and switch to form two electromagnetic response states, thereby achieving time modulation through periodic switching.
[0010] Furthermore, the period length of the periodic modulation sequence in step (2) is adjustable. When the period length is 8, the harmonic frequency interval is 31.25MHz, and when the period length is 16, the harmonic frequency interval is 15.625MHz. By designing the modulation sequence, selective enhancement of specific orders of +1 and +3 harmonics can be achieved.
[0011] Furthermore, the amplitude non-reciprocal transmission in step (4) includes: during forward propagation, the electromagnetic wave is slightly attenuated by the time-modulated metasurface and then enters the gain metasurface with low power, activating high gain and obtaining a high transmission coefficient T. 21 During reverse propagation, the electromagnetic wave enters the gain metasurface at full power, but only obtains low effective gain, resulting in a transmission coefficient T. 12 Significantly reduced, satisfying |T 12 |<|T 21 |
[0012] Furthermore, the non-reciprocal frequency transmission in step (4) includes: during forward propagation, the time-modulated metasurface first generates comb-shaped harmonics, and the target harmonics fall into the gain band of the gain metasurface to achieve selective amplification; during reverse propagation, the gain metasurface first amplifies the background noise, and the harmonics subsequently generated by the time-modulated metasurface cannot obtain effective gain, only the background noise is amplified, forming frequency domain transmission asymmetry.
[0013] Furthermore, the equipment used for performance verification in step (5) includes a vector network analyzer, a signal generator, and a spectrum analyzer. The verification indicators include the difference in bidirectional transmission coefficient, the difference in target harmonic amplification factor, and the effect of nonlinear signal processing.
[0014] The technical solution of this invention can be summarized as follows: 1) Construct the fabrication and parameter tuning process of gain metasurface and time-modulated metasurface, respectively realize voltage-controllable nonlinear gain and period-tunable comb harmonic generation, and provide basic functional support for non-reciprocal transmission. 2) Design a dual-supersurface spatial cascade architecture to form a bidirectional electromagnetic wave transmission path and establish the physical basis for asymmetric transmission in both forward and reverse directions; 3) By synergistically controlling nonlinear gain and harmonic characteristics, and utilizing power-dependent gain differences and harmonic-gain matching timing differences, nonlinear non-reciprocal transmission in both the amplitude and frequency domains can be achieved simultaneously. 4) It adopts a fully electrical bias control method, eliminating the need for magnetic bias and complex mechanical structures, and achieves low-loss, high-integration, and high-stability non-reciprocal nonlinear transmission.
[0015] The beneficial effects of this invention are: 1) Comprehensive non-reciprocal dimensions: Through the cascaded collaboration of two supersurfaces, non-reciprocal transmission in both the amplitude and frequency domains is achieved simultaneously, breaking through the limitation of single-dimensional non-reciprocity in traditional methods and meeting the multi-dimensional control requirements in complex scenarios. 2) No magnetic bias and low loss: The nonlinear amplification effect of the gain metasurface is used to compensate for the interlayer loss of the cascaded structure, eliminating the need for magnetic bias devices in traditional solutions, effectively reducing insertion loss and improving transmission efficiency. 3) Flexible and convenient control: Nonlinear gain control of the gain metasurface and harmonic characteristic control of the time-modulated metasurface can be achieved simply by bias voltage, without the need for complex mechanical structures or environmental control, making operation simple; 4) Compact structure and easy integration: The time modulation metasurface and the gain metasurface adopt a similar three-layer substrate architecture, which is simple to cascade, small in size, and easy to mass-produce and engineer. 5) Wide range of applications: It can be applied to fields such as information processing, one-way encryption, anti-eavesdropping communication, and electromagnetic wave one-way rectification, providing an efficient cascaded solution for the practical application of non-reciprocal transmission technology. Attached Figure Description
[0016] Figure 1 This is a flowchart of the non-reciprocal nonlinear transport implementation method based on metasurface cascades of the present invention; Figure 2 The figures show the experimental results of the gain metasurface and the time-modulated metasurface of this invention, wherein... Figure 2 (a) in the figure shows the curve of the gain of the gain metasurface as a function of bias voltage; Figure 2 (b) in the figure is a schematic diagram of the comb-shaped harmonic spectrum generated by the time-modulated metasurface; Figure 3 This is a graph showing the experimental results of the nonlinear nonreciprocal transport characteristics of this invention, wherein... Figure 3 (a) in the diagram is a schematic diagram of the received spectrum of the positive main frequency signal; Figure 3 (b) in the diagram is a schematic diagram of the received spectrum of the reverse main frequency signal, and... Figure 3 The contrast in (a) reflects the non-reciprocal nature of amplitudes; Figure 3 (c) in the diagram is a schematic diagram of the received spectrum of the signal at the reverse offset frequency (harmonics within the gain band); Figure 3 (d) in the diagram is a schematic diagram of the received signal spectrum at the positive offset frequency (harmonics entering the gain band). Detailed Implementation
[0017] The core technology of this invention is to spatially cascade a time-modulated metasurface and a gain metasurface, and achieve non-reciprocal nonlinear transmission in both amplitude and frequency dimensions by synergistically controlling the generation of periodic harmonics and nonlinear gain.
[0018] See Figure 1The present invention proposes a method for realizing non-reciprocal nonlinear transport based on metasurface cascades, comprising the following steps: (1) Preparation of gain metasurfaces and nonlinear gain tuning: (1.1) Fabrication of gain metasurface: A three-layer substrate architecture is adopted, with the bottom and top layers being dielectric substrates (relative permittivity). ,thickness The middle layer is a bonding layer (relative permittivity). ,thickness The top and bottom surfaces are printed with coin-shaped copper metal patches (24mm on each side). Electromagnetic coupling between the top and bottom patches is achieved through a central copper via. Another copper via connects the top patch to the gold ground plane on the bonding layer, forming a dual resonant cavity. A microscale tunnel diode (TD) is embedded in the resonant cavity to introduce voltage-controllable negative conductivity. .
[0019] (1.2) Nonlinear gain adjustment: A bias voltage is provided to the tunnel diode through a DC power supply. The transmission gain spectrum under different bias voltages is tested using a vector network analyzer to determine that the bias voltage range corresponding to the nonlinear gain is 85~125mV (corresponding to the negative differential resistance of the tunnel diode). The gain metasurface forms a gain peak with a bandwidth of 30 MHz at 4.88 GHz; the nonlinear decay characteristics of the gain with incident power are verified: when the incident power is -25 dBm, the gain is about 14 dB; when the incident power increases to 10 dBm, the gain drops to below 3 dB, ensuring that the gain metasurface has power-dependent nonlinear amplification capability.
[0020] (2) Fabrication and harmonic modulation of time-modulated metasurfaces: (2.1) Fabrication of time-modulated metasurface: The three-layer substrate architecture consistent with the gain metasurface is adopted. The side length of the top metal patch is 14.4 mm. Dual-PIN diodes are integrated in the gaps of the top metal patch. The dual-PIN diodes are respectively led out with independent bias voltage interfaces.
[0021] (2.2) Harmonic modulation verification: The switching state of the dual-PIN diode is controlled by the bias voltage, and the amplitude and phase response under the two states are tested; a periodic modulation sequence is loaded, and the harmonic generation effect is tested using a signal generator and a spectrum analyzer. The harmonic frequency interval is controlled (31.25MHz, 15.625MHz) by adjusting the modulation period (e.g., period 8, 16); a specific modulation sequence is designed to achieve selective enhancement of target order harmonics such as +1st order and +3rd order.
[0022] (3) Dual supersurface cascade construction: The prepared time-modulation metasurface and gain metasurface are spatially cascaded without gaps along the electromagnetic wave propagation direction, ensuring that the central axes of the two metasurfaces coincide. Port 1 is defined as the outer side of the time-modulation metasurface, and port 2 is defined as the outer side of the gain metasurface, forming two propagation paths: the forward path is port 1 → time-modulation metasurface → gain metasurface → port 2; the reverse path is port 2 → gain metasurface → time-modulation metasurface → port 1.
[0023] (4) Non-reciprocal nonlinear transport regulation: (4.1) Amplitude non-reciprocal modulation: The bias voltage of the gain metasurface is adjusted to the nonlinear gain range of 85~125mV. The difference in power loss in the forward and reverse propagation paths is utilized: During forward propagation, the electromagnetic wave is slightly attenuated by the time-modulated metasurface and enters the gain metasurface with low power, activating high gain and obtaining a high transmission coefficient T. 21 During reverse propagation, the electromagnetic wave is directly incident on the gain metasurface at full power, resulting in only low effective gain. After subsequent losses, the transmission coefficient T... 12 Significantly reduced, eventually forming |T 12 |<|T 21 The amplitude of | is non-reciprocal.
[0024] (4.2) Frequency non-reciprocal control: The modulation sequence of the time-modulated metasurface is controlled to generate comb-shaped harmonics and make the target harmonics fall precisely into the 30MHz gain band of the gain metasurface; during forward propagation, the time-modulated metasurface first generates harmonics, and the target harmonics are matched with the gain band to achieve selective amplification; during reverse propagation, the gain metasurface first amplifies the background noise, and the harmonics generated by subsequent time modulation cannot obtain effective gain, only the background noise is amplified, forming non-reciprocal transmission in the frequency domain (i.e., frequency domain transmission asymmetry).
[0025] (5) Performance verification: A vector network analyzer was used to test the bidirectional transmission spectrum of the cascaded system to verify the stability of the amplitude non-reciprocal characteristics. A signal generator and a spectrum analyzer were used to test the harmonic amplification characteristics of bidirectional propagation (including the difference in bidirectional transmission coefficients and the difference in target harmonic amplification factors) to confirm the frequency non-reciprocal effect. Electromagnetic waves of simulated image signals were input to verify the system's nonlinear signal processing and one-way encryption capabilities, ensuring that the non-reciprocal nonlinear transmission performance meets the design requirements and completing the entire implementation process.
[0026] Implementation Examples An implementation example of the present invention was carried out in an experimental environment equipped with a standard microwave test platform. The experimental equipment included: a vector network analyzer, a signal generator, a spectrum analyzer, a dual-horn antenna, a DC regulated power supply, and microwave absorbing materials. Using all the parameter values listed in the above specific embodiments, non-reciprocal nonlinear transmission based on metasurface cascade was achieved.
[0027] See Figure 2 ,in, Figure 2 (a) in the figure shows the curve of the gain of the gain metasurface as a function of bias voltage; Figure 2 (b) is a schematic diagram of the comb-shaped harmonic spectrum generated by the time-modulated metasurface.
[0028] Experimental results show that within the designed operating frequency range, the gain metasurface can achieve stable and controllable nonlinear gain output through bias voltage, and the time-modulated metasurface can generate tunable comb harmonics; the constructed cascaded system can effectively realize amplitude non-reciprocal and frequency non-reciprocal transmission characteristics, and the nonlinear transmission effect is stable.
[0029] See Figure 3 ,in, Figure 3 (a) in the diagram is a schematic diagram of the received spectrum of the positive main frequency signal; Figure 3 (b) in the diagram is a schematic diagram of the received spectrum of the reverse main frequency signal, and... Figure 3 The contrast in (a) reflects the non-reciprocal nature of amplitudes; Figure 3 (c) in the diagram is a schematic diagram of the received spectrum of the signal at the reverse offset frequency (harmonics within the gain band); Figure 3 (d) in the diagram is a schematic diagram of the received signal spectrum at the positive offset frequency (harmonics entering the gain band).
[0030] Experimental results demonstrate that, compared with existing methods, the method of this invention can achieve stable nonlinear non-reciprocal transmission under non-magnetic bias conditions, while possessing the advantages of low loss, convenient control, and high integration. It can be widely applied to non-reciprocal transmission scenarios in complex electromagnetic environments such as intelligent communication, radar sensing, and information security.
Claims
1. A method for realizing non-reciprocal nonlinear transport based on metasurface cascades, characterized in that, Includes the following steps: (1) Preparation of gain metasurface and nonlinear gain tuning: The gain metasurface of integrated tunnel diode is prepared, the negative conductance of tunnel diode is adjusted by DC bias voltage, the bias voltage range corresponding to nonlinear gain is tested and determined, and the nonlinear decay characteristics of gain with incident power are verified. (2) Time-modulated metasurface fabrication and harmonic modulation: a time-modulated metasurface integrating dual PIN diodes is fabricated. The switching state of the PIN diodes is controlled by bias voltage, and a periodic modulation sequence is applied to realize the generation of comb-shaped harmonics and selective enhancement of specific order harmonics. (3) Dual metasurface cascade construction: The time modulation metasurface and the gain metasurface are cascaded without gaps along the electromagnetic wave propagation direction. Port 1 is defined as the outer side of the time modulation metasurface and port 2 is defined as the outer side of the gain metasurface, forming a forward propagation path from port 1 to port 2 and a reverse propagation path from port 2 to port 1. (4) Non-reciprocal nonlinear transmission control: By controlling the nonlinear gain of the gain metasurface and the harmonic characteristics of the time-modulated metasurface through bias voltage, the difference in power loss and the difference in harmonic-gain matching order in the forward and reverse propagation paths are used to realize amplitude non-reciprocal transmission and frequency non-reciprocal transmission respectively. (5) Performance verification: Test the bidirectional transmission spectrum, harmonic amplification characteristics and nonlinear signal processing capabilities of the cascaded system to realize non-reciprocal nonlinear transmission.
2. The method for realizing non-reciprocal nonlinear transport based on metasurface cascades according to claim 1, characterized in that, The gain metasurface described in step (1) adopts a three-layer substrate architecture, including two dielectric substrates and one intermediate bonding layer. The dielectric substrate has a relative permittivity of [missing information]. ,thickness Relative permittivity of bonding layer ,thickness The top and bottom layers are printed with copper metal patches, which are coupled through copper vias to form a resonant cavity. A tunnel diode is embedded in the resonant cavity to introduce negative conductivity. .
3. The method for realizing non-reciprocal nonlinear transport based on metasurface cascades according to claim 1, characterized in that, The bias voltage range corresponding to the nonlinear gain mentioned in step (1) is 85~125mV, which corresponds to the negative differential resistance of the tunnel diode. The gain metasurface forms a gain peak with a bandwidth of 30MHz at 4.88GHz; the nonlinear attenuation characteristic is that the gain is about 14dB when the incident power is -25dBm, and the gain drops to below 3dB when the incident power increases to 10dBm.
4. The method for realizing non-reciprocal nonlinear transport based on metasurface cascades according to claim 1, characterized in that, The three-layer substrate architecture of the time modulation metasurface described in step (2) is consistent with that of the gain metasurface. The side length of the top metal patch is 14.4 mm. The dual-PIN diodes are independently controlled by the bias voltage and switch to form two electromagnetic response states. Time modulation is achieved through periodic switching.
5. The method for realizing non-reciprocal nonlinear transport based on metasurface cascades according to claim 1, characterized in that, The period length of the periodic modulation sequence in step (2) is adjustable. When the period length is 8, the harmonic frequency interval is 31.25MHz, and when the period length is 16, the harmonic frequency interval is 15.625MHz. The selective enhancement of specific order harmonics of +1 and +3 can be achieved by designing the modulation sequence.
6. The method for realizing non-reciprocal nonlinear transport based on metasurface cascades according to claim 1, characterized in that, The amplitude non-reciprocal transmission mentioned in step (4) includes: during forward propagation, the electromagnetic wave is slightly attenuated by the time-modulated metasurface and then enters the gain metasurface with low power, activating high gain and obtaining a high transmission coefficient T. 21 During reverse propagation, the electromagnetic wave enters the gain metasurface at full power, but only obtains low effective gain, resulting in a transmission coefficient T. 12 Significantly reduced, satisfying |T 12 |<|T 21 | 7. The method for realizing non-reciprocal nonlinear transport based on metasurface cascades according to claim 1, characterized in that, The frequency non-reciprocal transmission in step (4) includes: during forward propagation, the time-modulated metasurface first generates comb-shaped harmonics, and the target harmonics fall into the gain band of the gain metasurface to achieve selective amplification; during reverse propagation, the gain metasurface first amplifies the background noise, and the harmonics subsequently generated by the time-modulated metasurface cannot obtain effective gain, only the background noise is amplified, forming frequency domain transmission asymmetry.
8. The method for realizing non-reciprocal nonlinear transport based on metasurface cascades according to claim 1, characterized in that, The equipment used for performance verification in step (5) includes a vector network analyzer, a signal generator, and a spectrum analyzer. The verification indicators include the difference in bidirectional transmission coefficient, the difference in target harmonic amplification factor, and the effect of nonlinear signal processing.