Method and system for measuring reflection coefficient of information metamaterial based on harmonic detection

Abstract

The invention discloses an information metamaterial reflection coefficient measuring method and system based on harmonic detection, and relates to the technical field of electromagnetic material testing. Comprising the following steps: a transmitter generates a single-tone signal, the single-tone signal is incident to an information metamaterial, a periodic control signal for measuring a reflection coefficient of the information metamaterial is loaded to an information metamaterial unit, and the information metamaterial performs time modulation on the incident signal and reflects the incident signal; and the receiver receives the reflection signals carrying the reflection coefficient information of the information metamaterial, and solves reflection coefficient amplitudes and phases corresponding to different control signals according to frequency domain harmonic components of the reflection signals. According to the invention, the periodic control signal is utilized to regulate and control the harmonic component generated by the information metamaterial to measure the reflection coefficient of the information metamaterial, so that the interference influence caused by a background signal generated by environmental scattering is removed; and the measurement of the amplitude and the phase of the reflection coefficient of the information metamaterial can be realized under the condition of any combination of an incident angle and a receiving angle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic material testing, and in particular to a method and system for measuring the reflection coefficient of information metasurface based on harmonic detection. BACKGROUND

[0002] Information metasurface (commonly known as intelligent information metasurface in the field of communication) is one of the key enabling technologies of 6G. By designing the reflection coefficient of its electromagnetic unit, the amplitude and phase of the reflected electromagnetic wave can be controlled. In recent years, it has been widely researched and applied in fields such as coverage enhancement, indoor positioning, and direction modulation. By accurately measuring the change of the reflection coefficient of information metasurface with control signals at different angles, the reliability of the system in actual application can be effectively improved.

[0003] In existing research, the measurement of the reflection coefficient of information metasurface usually relies on a vector network analyzer to collect the amplitude and phase, and a metal plate with ideal reflection characteristics is used as a reference. Specifically, first, under the same transmit-receive antenna arrangement, the reflection signals of the metal plate and the information metasurface are measured respectively. By comparing the amplitude and phase information of the two, the relative reflection coefficient of the information metasurface is extracted. This method uses the predictability of the reflection characteristics of the metal plate to help calibrate system errors and improve measurement accuracy. However, this measurement scheme is usually only applicable to the two ideal scenarios of the transmit-receive antenna facing the information metasurface and the incident angle being equal to the receiving angle. It still has the problem of insufficient applicability for reflection characteristic measurement under other combinations of incident angle and receiving angle. In addition, due to the influence of environmental factors such as multipath effect during the measurement process, the measurement accuracy of the reflection coefficient may still be affected. At present, there is still a lack of systematic analysis and standardized scheme for the measurement process and applicable range of the reflection coefficient of information metasurface. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method and system for measuring the reflection coefficient of information metasurface based on harmonic detection. The time modulation capability of information metasurface is used to measure the reflection coefficient of information metasurface by analyzing the harmonics of the received signal, while avoiding the interference of background signals caused by environmental scattering.

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method and system for measuring the reflection coefficient of information metasurface based on harmonic detection. The time modulation capability of information metasurface is used to measure the reflection coefficient of information metasurface by analyzing the harmonics of the received signal, while avoiding the interference of background signals caused by environmental scattering.

[0006] According to the method for measuring the reflection coefficient of information metasurface based on harmonic detection provided by the present application, the method comprises the following steps:

[0007] Step 1: the single tone signal generated by the transmitter is incident to the information metamaterial, a periodic control signal is loaded on the information metamaterial, and the information metamaterial modulates the incident single tone signal in time under the control of the control signal and reflects it;

[0008] Step 2: the receiving antenna receives the reflected signal carrying the reflection coefficient information of the information metamaterial, and the amplitude and phase of the reflection coefficient of the information metamaterial corresponding to the control signal are solved according to the harmonic components in the frequency domain of the reflected signal;

[0009] Step 3: the incident angle of the single tone signal incident to the information metamaterial is changed, and the receiving angle of the receiving antenna and the central normal of the information metamaterial is changed, steps 1 and 2 are repeated, and the relationship between the reflection coefficient of the information metamaterial and the control signal under different angle configurations is measured.

[0010] As a further optimization scheme of the information metamaterial reflection coefficient measurement method based on harmonic detection, in step 1, the periodic control signal is a periodic control signal configured for measuring the reflection coefficient of the information metamaterial.

[0011] As a further optimization scheme of the information metamaterial reflection coefficient measurement method based on harmonic detection, in step 3, considering that the reflection coefficient of the information metamaterial is related to the angle direction, the positions of the transmitting antenna and the receiving antenna are changed, the incident angle of the single tone signal incident to the information metamaterial is changed, and the receiving angle of the receiving antenna and the central normal of the information metamaterial is changed.

[0012] As a further optimization scheme of the information metamaterial reflection coefficient measurement method based on harmonic detection, the control signal is periodic, and by loading a periodic control signal on the information metamaterial, the ability of the information metamaterial to control electromagnetic waves is utilized to make the single tone signal incident to the information metamaterial generate a series of harmonic signals carrying reflection coefficient information.

[0013] As a further optimization scheme of the information metamaterial reflection coefficient measurement method based on harmonic detection, different control signals are used to measure the reflection coefficients of the information metamaterial corresponding to different control signals.

[0014] As a further optimization scheme of the information metamaterial reflection coefficient measurement method based on harmonic detection, the amplitude and phase of the reflection coefficient of the information metamaterial corresponding to different control signals are extracted from the information carried by the harmonics through frequency spectrum analysis of the received signal at the receiving antenna.

[0015] As a further optimization of the method for measuring the reflection coefficient of information metamaterials based on harmonic detection described in this invention, considering the angle-sensitive characteristics of information metamaterials, that is, the reflection coefficient of information metamaterials is related to both the incident angle and the receiving angle, the reflection coefficient of information metamaterials exhibits different characteristics under different angle configurations. Specifically, when the same control signal is applied to the information metamaterial, the amplitude and phase of the reflection coefficient observed at the receiver position are different under different angle configurations.

[0016] As a further optimization of the information metamaterial reflection coefficient measurement method based on harmonic detection described in this invention, the reflection coefficient of each electromagnetic unit of the information metamaterial is changed by a control signal; time modulation refers to the periodic modulation of the reflection coefficient of the electromagnetic unit of the information metamaterial by a control signal, so that the reflected signal includes a series of harmonic signals.

[0017] A system based on the above-described method for measuring the reflection coefficient of information metamaterials using harmonic detection includes a single-tone signal source, an arbitrary waveform generator, an information metamaterial, a receiver, and an angle measuring instrument.

[0018] A single-tone signal source is used to provide a single-tone signal and incident it onto the information metamaterial. By applying a configured periodic control signal to the information metamaterial, the amplitude and phase of the reflection coefficient corresponding to a certain control signal under a specific angle configuration can be measured.

[0019] Arbitrary waveform generator, used to generate periodic control signals for measurement;

[0020] Information metamaterials are used to time-modulate incident single-tone signals to generate reflected signals carrying information about the reflection coefficient of the information metamaterial.

[0021] The receiver is used to receive the reflected signal carrying the reflection coefficient information of the information metamaterial and analyze its spectrum, thereby solving for the amplitude and phase of the reflection coefficient of the information metamaterial corresponding to the control signal;

[0022] An angle measuring instrument is used to measure the angles between the transmitting antenna and the receiving antenna and the center normal of the information metamaterial, and to determine the relationship between the reflection coefficient of the information metamaterial and the control signal under different angle configurations.

[0023] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0024] (1) Compared with existing information metamaterial reflection coefficient measurement schemes, this invention uses harmonic signals generated by time modulation of information metamaterials to measure the reflection coefficient, which can remove the interference caused by background signals generated by environmental scattering and ensure the accuracy of the measurement results.

[0025] (2) Furthermore, the technical solution of the present invention is not limited to a certain frequency band. For information metamaterials that work in any frequency band, the technical solution of the present invention can be used to measure the reflection coefficient. Moreover, the technical solution of the present invention is applicable to any combination of incident angle and receiving angle. This is very meaningful for angle-sensitive information metamaterials (i.e., the reflection coefficient of information metamaterials is not only related to the control signal, but also to the incident angle and receiving angle). Attached Figure Description

[0026] Figure 1 A flowchart illustrating a method for measuring the reflectance coefficient of an information metamaterial according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the information metamaterial reflectance coefficient measurement system in an embodiment of the present invention;

[0028] Figure 3 This is a frame structure used to measure the reflectance coefficient of information metamaterials in an embodiment of the present invention;

[0029] Figure 4a The harmonic method and fundamental wave method in the embodiments of the present invention are The curve of the phase of the reflection coefficient as a function of the control signal, measured under the condition of having an absorbing wall;

[0030] Figure 4b The harmonic method and fundamental wave method in the embodiments of the present invention are The curve showing the variation of the reflection coefficient amplitude with the control signal, measured under the condition of having an absorbing wall;

[0031] Figure 5a The harmonic method in the embodiments of the present invention The reflection coefficient phase variation curves as a function of control signal were measured under conditions with and without absorbing walls.

[0032] Figure 5b The harmonic method in the embodiments of the present invention The reflection coefficient amplitude as a function of control signal was measured under conditions with and without a absorbing wall.

[0033] Figure 6a The fundamental wave method in the embodiments of the present invention The reflection coefficient phase variation curves as a function of control signal were measured under conditions with and without absorbing walls.

[0034] Figure 6b The fundamental wave method in the embodiments of the present invention The curves showing the variation of the reflection coefficient amplitude with the control signal were obtained under conditions with and without the absorbing wall. Detailed Implementation

[0035] To make the system and method of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Information metamaterials are composed of artificial subwavelength unit structures with electromagnetic properties. Their electromagnetic properties are determined by the intrinsic properties of the constituent materials, the microstructure of the artificial units, and the tunable units, allowing for wide application across the electromagnetic spectrum from microwaves to visible light. The reflection coefficient of each electromagnetic unit can be adjusted by applying a control signal, making the overall reflection coefficient of the information metamaterial programmable. Therefore, accurately measuring the reflection coefficient of information metamaterials is crucial for improving the accuracy of system modeling and the effectiveness of practical applications.

[0037] The method for measuring the reflection coefficient of information metamaterials based on harmonic detection provided in this invention includes the following specific steps: Figure 1 As shown:

[0038] Step 1: The single-tone signal generated by the transmitter is incident on the information metamaterial. The periodic control signal configured for measuring the reflection coefficient of the information metamaterial is loaded onto the information metamaterial unit. Under the regulation of the control signal, the information metamaterial modulates the incident single-tone signal in time and reflects it, and then proceeds to Step 2.

[0039] Step 2: The receiving antenna receives the reflected signal carrying the reflection coefficient information of the information metamaterial. Based on the harmonic components in the frequency domain of the reflected signal, the amplitude and phase of the reflection coefficient of the information metamaterial corresponding to a certain control signal can be obtained, and then proceed to step 3.

[0040] Step 3: Considering that the reflection coefficient of the information metamaterial is related to the angle and direction, change the position of the transmitting antenna and the receiving antenna, that is, change the incident angle of the single tone signal to the information metamaterial and the receiving angle between the receiving antenna and the center normal of the information metamaterial. Repeat Step 1 and Step 2 to measure the relationship between the reflection coefficient of the information metamaterial and the control under different angle configurations.

[0041] A schematic diagram of the information metamaterial reflection coefficient measurement system based on harmonic detection in this embodiment of the invention is shown below. Figure 2 As shown, the system includes a transmitting antenna Tx, an information metamaterial, and a receiving antenna Rx. In this scenario, the information metamaterial is reflective and has 8*16=128 elements. The operating frequency is... The single-tone signal generated by the single-tone signal source is incident perpendicularly onto the information metamaterial via the transmitting antenna Tx, meaning the incident angle is always maintained. The receiving antenna moves along an arc centered on the information metamaterial to change the receiving angle. The transmitting antenna, the information metamaterial, and the receiving antenna are on the same horizontal plane; it is worth noting that the incident angle... and receiving angle The settings are unrestricted; the specific settings in the embodiments are only used to demonstrate the measurement scheme proposed in this invention. In addition, positive incident angles and exit angles represent that the transmitting antenna and receiving antenna are on the left side of the information metamaterial, and negative incident angles and exit angles represent that the transmitting antenna and receiving antenna are on the right side of the information metamaterial. Finally, the measurement scheme proposed in this invention is applicable to three-dimensional scenes, that is, in addition to the azimuth angle, the elevation angle between the transmitting and receiving antennas and the information metamaterial is also arbitrary.

[0042] The present invention relates to a method for measuring the reflection coefficient of information metamaterials based on harmonic detection, wherein a reference reflection coefficient is used. Determined by the following formula:

[0043]

[0044] In the formula, This refers to the static channel vector between the receiving antenna and the information metamaterial. This represents the static channel vector between the transmitting antenna and the information metamaterial. This refers to the transmission power.

[0045] The method for measuring the reflection coefficient of information metamaterials based on harmonic detection in this embodiment of the invention includes the following method for setting the control voltage signal for measuring the reflection coefficient of the information metamaterials:

[0046] Because different control voltages will cause the information metamaterial to exhibit different reflectivity. That is, each reflection coefficient Corresponding to a unique control voltage, therefore the reflection coefficient Specifically, it is determined using the following formula:

[0047]

[0048] in It is a rectangular window sampling function, and its expression is as follows:

[0049]

[0050] It is the q-th element of a known time series that can be freely designed, where Q is the total number of elements in the empty time series. It is the period of the space-time sequence, and the duration of each element is... .

[0051] If the information metamaterial follows the time-domain sequence of reflection coefficients defined in the above equation, then the received signal at the receiving antenna... The first harmonic component can be expressed as follows:

[0052]

[0053] In the formula, for Received noise on first harmonics, matrix The definition is as follows:

[0054]

[0055] in It is an identity matrix, and Middle elements

[0056]

[0057] The time-domain sequence of the reflection coefficients of the electromagnetic unit First harmonic components.

[0058] In this embodiment, the frame structure of the voltage control signal used to measure the reflection coefficient of the information metamaterial in step 1 consists of a synchronization subframe, a reference sequence, and multiple repeating space-time sequence 1 and space-time sequence 2 subframes, as follows: Figure 3 As shown, the reference sequence is a control signal with a constant voltage of 0V, used to measure the reference reflection coefficient. This is used as a reference, with its reflection coefficient considered to have an amplitude of 1 and a phase of 0°. Space-time sequence 1 is used to measure the control voltage. The corresponding information metamaterial reflection coefficient, space-time sequence 2 is used to measure the control voltage. The corresponding information metamaterial reflection coefficient, and the specific design of the spatiotemporal sequence subframe are as follows:

[0059] Each spatiotemporal sequence subframe is a square wave signal with a fixed duty cycle and a reflection coefficient. In two states and Switching between them is defined as follows:

[0060]

[0061] Under these conditions, the time-domain sequence of the reflection coefficient of the electromagnetic unit First harmonic components This can be further expressed as the following formula:

[0062]

[0063] according to The calculation results ultimately show that the receiving antenna at point Rx is... First harmonic components as follows.

[0064]

[0065]

[0066] Harmonic components are typically measured under conditions of high signal-to-noise ratio, therefore Received noise on first harmonic It can be approximated as negligible.

[0067] In this embodiment, all parameters are set as follows: the total number of elements in the space-time sequence Q = 32; the period of each space-time sequence... The space-time sequence has a duty cycle of 50%, that is... The harmonic order of the received signal spectrum at the observed receiver. Under this parameter setting, the receiving antenna Rx... First harmonic components The expression can be simplified to the following formula:

[0068]

[0069] Combined with reference reflection coefficient Measurement results We can finally obtain the following expression for the reflection coefficient:

[0070]

[0071] Assuming reference reflection coefficient The amplitude is 1, and the phase is In this embodiment, step 2 involves extracting the reflection coefficient using harmonics. The phase method is as follows:

[0072]

[0073] In this embodiment, the method for extracting the reflection coefficient amplitude through harmonics in step 2 is as follows:

[0074]

[0075] In this embodiment, to verify the accuracy of the measured metamaterial reflectance coefficient, the following verification scheme is proposed:

[0076] Comparative Verification of Harmonic and Fundamental Wave Methods: In these two sets of comparative experiments, we placed absorbing walls around the system to simulate an anechoic chamber environment and reduce interference from environmental scattering. In the fundamental wave method, we set the control signal for the information metamaterial to a linearly varying voltage signal with a voltage range of 0-11V. All other settings were the same as in the harmonic method. That is, the transmitting antenna emitted a single-tone carrier signal that irradiated the information metamaterial, and under the action of the control signal, the information metamaterial modulated the electromagnetic waves. Figure 4a The harmonic method and the fundamental wave method are in The curve of the reflection coefficient amplitude as a function of the control signal obtained under the measured conditions. Figure 4b The harmonic method and the fundamental wave method are in The curves showing the phase change of the reflection coefficient with the control signal obtained under the specified conditions show that the harmonic method can accurately measure the reflection coefficient of information metamaterials.

[0077] In this embodiment, to verify the anti-interference performance of the proposed method for measuring the reflection coefficient of information metamaterials based on harmonic detection, the following verification scheme is proposed:

[0078] We chose whether to place absorbing walls around the system. When absorbing walls were placed, most of the background scattered signal was absorbed, and background interference was negligible. When no absorbing walls were placed, the background scattered signal energy was not negligible due to the presence of many metallic scattering objects in the environment, resulting in significant background interference. In both environments, we measured the reflectivity of the information metamaterial using the fundamental wave method and the harmonic wave method.

[0079] In the fundamental wave method, the presence of environmental scattering particles and the influence of multipath propagation make it impossible to accurately measure the reflection coefficient of the information metamaterial corresponding to each control signal. Since harmonic components all originate from the reflected signal of the information metamaterial, and environmental scattering signals do not generate frequency signals other than the carrier frequency, the harmonic method can directly measure the reflection coefficient of the information metamaterial under different control signals and is unaffected by environmental interference. Through observation... Figure 5a and Figure 5b It can be observed that the harmonic method has good resistance to environmental interference; through observation Figure 6a and Figure 6b It can be observed that the fundamental wave method performs poorly in measuring the reflection coefficient in complex environments.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring the reflection coefficient of an information metamaterial based on harmonic detection, characterized in that, The method comprises the following steps: Step 1: a single-tone signal generated by a transmitter is incident to an information metamaterial, a periodic control signal is loaded on the information metamaterial, and the information metamaterial modulates the incident single-tone signal in time and reflects under the control of the control signal; Step 2: a receiving antenna receives a reflected signal carrying information of a reflection coefficient of the information metamaterial, and the amplitude and phase of the reflection coefficient of the information metamaterial corresponding to the control signal are solved according to harmonic components in a frequency domain of the reflected signal; Step 3: the incident angle of the single-tone signal incident to the information metamaterial and the receiving angle of the receiving antenna and the central normal of the information metamaterial are changed, and steps 1 and 2 are repeated to measure the change relationship between the reflection coefficient of the information metamaterial and the control signal under different angle configurations.

2. A method of measuring the reflection coefficient of an information metamaterial based on harmonic detection according to claim 1, characterized in that, In step 1, the periodic control signal is a periodic control signal configured for measuring the reflection coefficient of the information metamaterial.

3. A method of measuring the reflection coefficient of an information metamaterial based on harmonic detection according to claim 1, characterized in that, In step 3, the positions of the transmitting antenna and the receiving antenna are changed, the incident angle of the single-tone signal incident to the information metamaterial and the receiving angle of the receiving antenna and the central normal of the information metamaterial are changed, considering that the reflection coefficient of the information metamaterial is related to the angle direction.

4. The method of claim 1, wherein the method is a harmonic detection based information metamaterial reflection coefficient measurement method. The control signal is periodic, the periodic control signal is loaded on the information metamaterial, the ability of the information metamaterial to control electromagnetic waves is utilized, and the single-tone signal incident to the information metamaterial generates a series of harmonic signals carrying reflection coefficient information.

5. The method of claim 1, wherein the method is based on harmonic detection of the information metamaterial reflection coefficient. Different control signals are used to measure the reflection coefficients of the information metamaterial corresponding to different control signals.

6. The method of claim 1, wherein the method is based on harmonic detection. The amplitude and phase of the reflection coefficient of the information metamaterial corresponding to different control signals are extracted from the information carried by the harmonics through frequency spectrum analysis of the received signal at the receiving antenna.

7. The method of claim 1, wherein the method is based on harmonic detection of the information metamaterial reflection coefficient. Considering the angle sensitivity of the information metamaterial, that is, the reflection coefficient of the information metamaterial is related to the incident angle and the receiving angle, the reflection coefficient of the information metamaterial presents different characteristics under different angle configurations, and specifically, the amplitude and phase of the reflection coefficient observed at the receiver under different angle configurations are different when the same control signal is loaded on the information metamaterial.

8. The method of claim 1, wherein the method is a harmonic detection based information metamaterial reflection coefficient measurement method. The reflection coefficient of each electromagnetic unit of the information metamaterial is changed by the control signal; time modulation means that the reflection coefficient of the electromagnetic unit of the information metamaterial is modulated by the periodic control signal, so that the reflected signal includes a series of harmonic signals.

9. A system for measuring the reflection coefficient of an information metamaterial based on harmonic detection according to claim 1, characterized in that, The method comprises a single-tone signal source, an arbitrary waveform generator, an information metamaterial, a receiver, and an angle measuring instrument, wherein, The single-tone signal source is used to provide a single-tone signal and incident to the information metamaterial, and the amplitude and phase of the reflection coefficient corresponding to a certain control signal under a specific angle configuration are measured by applying a configured periodic control signal to the information metamaterial; The arbitrary waveform generator is used to generate a periodic control signal for measurement; The information metamaterial is used to modulate the incident single-tone signal in time and generate a reflected signal carrying information of a reflection coefficient of the information metamaterial; a receiver for receiving the reflection signal carrying the information metamaterial reflection coefficient information and analyzing the spectrum of the reflection signal to obtain the amplitude and phase of the information metamaterial reflection coefficient corresponding to the control signal; an angle measuring instrument for measuring the included angle between the center normal line of the information metamaterial and the transmitting antenna and the receiving antenna, and determining the relationship between the information metamaterial reflection coefficient and the control signal under different angle configurations.

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