Rapid fault diagnosis method for programmable metasurface based on orthogonal coding space-time modulation

Abstract

The invention discloses a programmable metasurface fault rapid diagnosis method based on orthogonal coding space-time modulation. The method comprises the following steps: step 1, applying independent orthogonal coding space-time modulation to each metasurface unit on a programmable metasurface to be diagnosed by adopting a time-varying signal based on orthogonal coding; 2, irradiating the programmable metasurface to be diagnosed by using a single-frequency plane wave; 3, receiving a reflection signal of the programmable metasurface to be diagnosed, and recovering each orthogonal coding channel energy from the reflection signal; step 4, according to the magnitude of the recovered orthogonal coding channel energy, determining a malfunctioning metasurface unit; when a certain unit breaks down, preset orthogonal coding modulation cannot be normally executed, so that a corresponding coding channel in a transmitting signal is lost, and therefore whether the unit corresponding to each coding channel breaks down or not can be judged by recovering energy distribution of each coding channel in a receiving signal, and accurate and efficient fault diagnosis is achieved.

Description

Technical Field

[0001] This invention belongs to the field of artificial electromagnetic materials technology, specifically a rapid fault diagnosis method for programmable metasurfaces based on orthogonal coding time-temperature control. Background Technology

[0002] Programmable metasurfaces (PMs), as a novel type of artificial electromagnetic material, are also known as intelligent reconfigurable surfaces in the field of communications. They possess the ability to dynamically control electromagnetic waves, generating various novel electromagnetic phenomena and improving the wireless channel environment. They have broad application prospects in radar, sensing, and wireless communication, attracting considerable attention from researchers and industry. However, in actual deployment, due to factors such as aging control circuitry and poor soldering of adjustable components, some units in the programmable metasurface may fail, affecting its normal operation and reducing system performance and reliability. Typically, programmable metasurfaces consist of a large number of subwavelength units, and manual troubleshooting would waste significant manpower and time. Therefore, a simple and reliable fault diagnosis method for programmable metasurfaces is urgently needed to achieve rapid identification and location of faulty units for subsequent repair.

[0003] Traditional diagnostic methods are either based on complex signal processing algorithms or rely on specific electromagnetic equipment and environments (such as vector network analyzers and anechoic chamber environments), and are mostly based on scenarios with fault coefficient distribution. In practical applications, they are limited by the performance of processing equipment and the measurement environment. Summary of the Invention

[0004] Purpose of the invention: To address the problem that traditional diagnostic methods, which rely on complex signal processing algorithms or specific electromagnetic equipment and environments, cannot quickly identify and locate faulty units when some units in a programmable metasurface may fail, this invention proposes a rapid fault diagnosis method for programmable metasurfaces based on orthogonal coding time-conditioning mechanism, providing a fast, efficient, and low-cost solution for fault diagnosis of programmable metasurfaces.

[0005] Technical solution: A rapid fault diagnosis method for programmable metasurfaces based on orthogonal coding time-conditioning mechanism, comprising the following steps:

[0006] Step 1: Apply an independent orthogonal coding time-varying mechanism to each metasurface unit on the programmable metasurface to be diagnosed using a time-varying signal based on orthogonal coding, so that different metasurface units correspond to mutually orthogonal coding channels;

[0007] Step 2: Illuminate the programmable metasurface to be diagnosed with a single-frequency plane wave, and the reflected signals of different metasurface units are modulated into different orthogonal coding channels;

[0008] Step 3: Receive the reflected signal from the programmable metasurface to be diagnosed, and recover the energy of each orthogonal coded channel from it;

[0009] Step 4: Based on the magnitude of the recovered energy of each orthogonal coded channel, determine the faulty metasurface unit.

[0010] Furthermore, the orthogonal encoding is an orthogonal code sequence that satisfies the following conditions:

[0011] Condition 1: The encoded sequences are mutually orthogonal;

[0012] Condition 2: It has time-varying characteristics.

[0013] Furthermore, the time-varying signal of each metasurface unit can be repeatedly subjected to orthogonal coding modulation for multiple cycles within a single measurement time.

[0014] Furthermore, depending on the requirements, a blank sequence or synchronization sequence can be inserted before orthogonal coding modulation.

[0015] Furthermore, prior to step 1, the following steps may also be performed:

[0016] The programmable metasurface to be diagnosed is partitioned;

[0017] Perform steps 1 through 4 for each programmable metasurface.

[0018] Furthermore, in step 4, the step of determining the faulty metasurface unit based on the magnitude of the recovered energy of each orthogonal coded channel specifically includes:

[0019] The fixed threshold determination method is used to determine the faulty metasurface unit based on the magnitude of the recovered energy of each orthogonal coded channel.

[0020] Furthermore, in step 4, the step of determining the faulty metasurface unit based on the magnitude of the recovered energy of each orthogonal coded channel specifically includes:

[0021] An adaptive clustering algorithm is used to determine the faulty metasurface units based on the magnitude of the recovered energy of each orthogonal coded channel.

[0022] Furthermore, the programmable metasurface to be diagnosed only needs to support time modulation function and can be any of the following structures: transmissive, reflective, or active radiative. One or more active devices are integrated on each metasurface unit, and it can operate in any electromagnetic wave frequency band provided that the transceiver system supports it.

[0023] Beneficial Effects: The method of this invention applies independent orthogonal coding modulation to each programmable metasurface unit using a time-varying control signal, so that different units correspond to mutually orthogonal coding channels. When a unit malfunctions, the predetermined orthogonal coding modulation cannot be executed normally, resulting in the loss of the corresponding coding channel in the transmitted signal. By demodulating the received signal using standard orthogonal coding, the energy distribution of each coding channel in the received signal is recovered. By setting an appropriate discrimination threshold or using an adaptive clustering algorithm, it is possible to determine whether the unit corresponding to each coding channel is faulty, thereby achieving accurate and efficient fault diagnosis. Compared with the prior art, this invention has the following advantages:

[0024] (1) The method of the present invention can be applied to the case where the fault cells are non-sparsely distributed in the programmable metasurface to be tested;

[0025] (2) The method of the present invention has a simple measurement process, does not require repeated iterative measurements, has a short measurement time, and can quickly obtain results;

[0026] (3) The method of the present invention does not require complex signal processing algorithms, has low computational resource requirements for data processing equipment, and does not require special measurement equipment, specific measurement environment or multiple iterative measurements, such as vector network analyzer or specific measurement environment such as microwave anechoic chamber environment, and the hardware implementation is simple.

[0027] (4) The method of the present invention is highly robust to the signal-to-noise ratio and the spatial position of the transmitting and receiving antennas, which is sufficient to meet the needs of actual measurement scenarios. Attached Figure Description

[0028] Figure 1 This is a flowchart of a rapid fault diagnosis method for programmable metasurfaces based on orthogonal coding time-temperature regulation proposed in Example 1;

[0029] Figure 2 This is a schematic diagram of the spatiotemporal coding matrix of the programmable metasurface proposed in Example 2;

[0030] Figure 3 This is a schematic diagram illustrating the diagnostic process for a programmable metasurface in Example 2, wherein... Figure 3 In the diagram, (a) represents the amplitude of the reflection signal from the programmable metasurface to be diagnosed. Figure 3 In the diagram, (b) represents the phase of the reflection signal from the programmable metasurface to be diagnosed. Figure 3 (c) in the diagram represents the operating state of each unit of the programmable metasurface to be diagnosed. Figure 3 In the diagram, (d) represents the relative energy of each coded channel recovered using this method and the corresponding diagnostic results;

[0031] Figure 4 This is a flowchart illustrating the diagnostic process performed on the programmable metasurface to be diagnosed, as described in this embodiment.

[0032] Figure 5 This is a schematic diagram of the partition diagnosis strategy proposed in Example 3, wherein, Figure 5 (a) in the diagram shows the control signal frame structure used. Figure 5 (b) in the figure represents the specific spatiotemporal coding matrix;

[0033] Figure 6 This is a schematic diagram illustrating the diagnostics of a larger-scale array in Example 4, wherein... Figure 6 (a) and Figure 6 In the diagram, (b) represents the relative energy of the coded channel corresponding to each unit in the received signal. Figure 6 (c) and Figure 6 In the diagram, (d) represents the distribution of faulty cells in the two arrays;

[0034] Figure 7 This is a graph showing the relationship between the diagnostic error rate of the method of the present invention and the number of faulty units, the receiving angle, and the signal-to-noise ratio. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the following description, in conjunction with the accompanying drawings and embodiments, will further illustrate a method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning mechanism.

[0036] Example 1:

[0037] like Figure 1 As shown, this embodiment proposes a rapid fault diagnosis method for programmable metasurfaces based on orthogonal coding time-conditioning, which mainly includes the following steps:

[0038] Step 1: Irradiate the programmable metasurface to be diagnosed using a single-frequency plane wave. The programmable metasurface consists of several metasurface units, each controlled by an independent time-varying signal based on orthogonal coding. The orthogonal coding includes common orthogonal code sequences such as Hadamard codes and Walsh codes; the requirement is that the coding sequences are orthogonal. In other words, the control signal for each metasurface unit is modulated based on an independent orthogonal coding sequence. Furthermore, different orthogonal codes should all have time-varying characteristics, so that the reflected signal from a normal unit exhibits time modulation characteristics not present in the reflected signal from a faulty unit. The control signal of each metasurface unit can be repeatedly orthogonally coded and modulated multiple times within a single measurement period to reduce the impact of noise on the measurement results and increase the stability and reliability of the diagnosis. Simultaneously, a blank sequence or synchronization sequence can be inserted before the orthogonal coding modulation for signal synchronization, depending on the requirements.

[0039] The programmable metasurface to be diagnosed only needs to support time modulation and can be of any type, including transmissive, reflective, or active radiative structures. Each metasurface unit integrates one or more active devices (including but not limited to PIN diodes, varactor diodes, etc.), and can operate in any electromagnetic frequency band, provided the transceiver system supports it. The following explanation uses Hadamard code as the orthogonal encoding and a reflective programmable metasurface to be diagnosed as an example.

[0040] Assuming the programmable metasurface to be diagnosed consists of N independently encoded metasurface units, it can be based on the K-order Hadamard matrix H. K Generate a time-varying signal for each metasurface unit, where H K The following recurrence relation is satisfied:

[0041]

[0042] Among them, H K Each line represents an independent Hadamard code, and the different Hadamard codes are orthogonal to each other. Because H... K The first row consists only of +1 elements, and the generated encoding sequence lacks time-varying characteristics, making it difficult to distinguish the reflected signals of the unit under normal and fault conditions. Therefore, it is excluded when generating the control signal. Thus, for the nth metasurface unit, based on H... K The (n+1)th row generates its time-varying signal. When all metasurface units are modulated simultaneously, the minimum order of the required Hadamard matrix is:

[0043]

[0044] in, This indicates the rounding up operation.

[0045] Considering that the required encoding time will increase as the size of the programmable metasurface increases and the number of independent units increases, a partitioning and sequential diagnosis strategy can be adopted for large-scale programmable metasurface arrays to reduce the time length of the orthogonal encoding sequence, thereby reducing the demand for computing resources.

[0046] To achieve time-domain Hadamard code modulation, the control sequence c of the nth metasurface unit... n Must meet:

[0047]

[0048] in, The bit symbol represents the control sequence in the l-th time slot.

[0049] Under this control sequence, the reflection coefficient of the nth coding unit in the lth time slot is:

[0050]

[0051] Among them, A e φ0 represents the reflection amplitude, and φ0 represents the reflection phase corresponding to the coded state "0".

[0052] Assume the frequency is f c single-frequency carrier from azimuth angle When the programmable metasurface to be diagnosed is illuminated, the receiving angle is... The intermediate frequency received signal at that location can be expressed as:

[0053]

[0054] in, and Let n represent the angular response of the nth metasurface element in the incident and exit directions, respectively. l It is additive white Gaussian noise. The orientation factor of the nth metasurface unit is defined as:

[0055]

[0056] In the formula, λ c d represents the operating wavelength of the metasurface. nx and d ny Let θ and y represent the distances between the nth metasurface element and the first metasurface element in the x and y directions, respectively. These represent the pitch angle and azimuth angle, respectively.

[0057] Step 2: For each normally functioning metasurface unit, its reflection coefficient conforms to the above... The expression indicates that the reflected signals from different metasurface units are modulated onto different orthogonal coding channels. However, faulty metasurface units, unable to perform time modulation, exhibit no modulation characteristics in their reflected signals. This reflectance coefficient is formally equivalent to H, which consists of all +1s. K (1,·) related, can be written as:

[0058]

[0059] This indicates that the reflected signal component of the faulty metasurface unit remains orthogonal to the signals of other coded channels, ensuring that the reflected signal component of the faulty metasurface unit will not interfere with the reflected signal of the normal unit, thus ensuring accurate and unambiguous programmable metasurface fault diagnosis.

[0060] Step 3: For each normally functioning unit, its reflected signal is modulated onto its corresponding orthogonal coding channel. However, because the faulty unit cannot complete the predetermined time modulation, its corresponding orthogonal coding channel is missing in the received signal. Therefore, the reflected signal from the programmable metasurface to be diagnosed is received, and the energy of each coding channel in the received signal is recovered using standard orthogonal codes. At the receiving end, for the m-th coding channel, its energy... The following steps can be taken to restore it:

[0061]

[0062] Substituting the previous expression, we get:

[0063]

[0064] The above expression can be discussed in two cases:

[0065] Case 1: If the m-th coding unit works normally, then From the discussion in step 2 and H K The orthogonality yields:

[0066]

[0067] Therefore, the recovered coded channel energy is

[0068]

[0069] Among them, P n This represents noise energy.

[0070] Case 2: If the m-th coding unit fails, then From the discussion in step 2 and H K The orthogonality yields:

[0071]

[0072] This led to

[0073]

[0074] Step 4: Based on the relative energy levels of the recovered coding channels, set an appropriate threshold (or use other adaptive discrimination algorithms) to diagnose the unit status. As discussed in Step 3, under high signal-to-noise ratio conditions, the coding channel energy corresponding to a faulty unit will be significantly lower than that of a normally functioning unit.

[0075] In this embodiment, a suitable judgment threshold Λ is set for diagnosis, and the m-th coding unit is determined to be:

[0076]

[0077] It is worth noting that this method is robust to offsets in both transmit and receive azimuth, because these azimuth angles only affect... The absolute strength of the signal depends on the strength of the signal, while the diagnostic process depends on the relative magnitude of the coding channel energy corresponding to the normal and faulty units. Furthermore, the discrimination method involved in this step is not limited to the fixed threshold method; K-means algorithm, hierarchical clustering algorithm, or even some neural network-based classification methods can be used for adaptive discrimination, increasing the flexibility and reliability of the diagnosis at the cost of increased algorithm complexity.

[0078] Example 2:

[0079] The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning proposed in Example 1 is now applied to... Figure 2 The spatiotemporal coding matrix shown is as follows: Figure 3 As shown, in this embodiment, the programmable metasurface to be diagnosed consists of 16 coding units, and the programmable metasurface is modulated using a time-varying control signal based on a 32nd-order Hadamard matrix. The distribution of the faulty units is as follows: Figure 3 As shown in (c) above. After a single-frequency incident plane wave is reflected by this metasurface, the amplitude and phase of the intermediate frequency received signal are as follows: Figure 3 (a) and Figure 3 As shown in (b) of the figure. The recovered coded channel energies and diagnostic results using the diagnostic method proposed in Example 1 are as follows. Figure 3 As shown in (d) above. To reduce the impact of noise, the result is the average energy over 6 modulation cycles; and all energies are normalized based on the highest channel energy. It can be seen that the received energy is divided into two groups based on the unit's operating state, with significant differences. The received energy corresponding to normally functioning units remains around 0 dB, while the received energy corresponding to faulty units remains at the noise level. By setting an appropriate threshold, a completely accurate diagnosis can be achieved. In this embodiment, the number of faulty units is 7, which does not meet the sparsity distribution condition, but this embodiment can still perform a correct diagnosis and is applicable to more scenarios than traditional methods based on sparsity sensing.

[0080] Figure 4 This document demonstrates an example implementation flow for diagnosing a programmable metasurface using the diagnostic method proposed in Embodiment 1. The signal source provides a single-frequency incident wave, the FPGA provides orthogonally coded and modulated control signals to the programmable metasurface, and the USRP receives the modulated intermediate frequency signal and performs subsequent signal processing to complete the fault diagnosis. It should be noted that the signal source, FPGA, and USRP involved in this embodiment can be replaced with other devices with equivalent functions according to the actual application scenario requirements.

[0081] Example 3:

[0082] like Figure 5 As shown, this embodiment illustrates a specific implementation of a partitioned diagnostic strategy. In this embodiment, a programmable metasurface consisting of 16 coded units is divided into two groups according to odd and even numbering during the diagnostic process, and these groups are alternately excited. Its control signal frame structure is as follows: Figure 5 As shown in (a) above, a blank sequence is inserted at the beginning for receiver synchronization. The specific spatiotemporal coding matrix is ​​as follows: Figure 5 As shown in (b), the order of the Hadamard code used is reduced from 32 to 16. For large-scale programmable metasurface arrays, this strategy can reduce the time length of the orthogonal coding sequence, thereby reducing the demand for computational resources.

[0083] Example 4:

[0084] like Figure 6 As shown, this embodiment illustrates an example of diagnostics performed on a larger-scale programmable metasurface array. The two examples are based on two point-controlled arrays of 15×15 and 25×25 respectively, where each array has approximately 30% randomly distributed faulty cells. Spatiotemporal coding matrices based on 256th-order and 1024th-order Hadamard codes were used during the diagnostic process for the two arrays, respectively. The energy of the corresponding coding channel for each cell obtained from the diagnostic is shown below. Figure 6 (a) and Figure 6 As shown in (b) above, the corresponding actual fault cell distribution is as follows: Figure 6 (c) and Figure 6 As shown in (d) above. The results show that the channel energy of faulty cells is significantly lower than that of normal cells, making them easily identifiable. This confirms the effectiveness of the present invention in diagnosing large-scale, high-fault-ratio arrays.

[0085] Figure 7 The influence of factors such as signal-to-noise ratio, number of faulty units, and receiving angle on the diagnostic error rate of this invention is demonstrated. Figure 7 As shown in (a), for a given number of faulty units, the diagnostic error rate of this invention decreases as the signal-to-noise ratio increases. Furthermore, when the signal-to-noise ratio exceeds 15 dB, the diagnostic error rate will be less than 10% regardless of the number of faulty units. -4 On the other hand, for a given signal-to-noise ratio, the diagnostic error rate remains almost stable, and even decreases slightly, as the number of faulty cells increases. This result demonstrates the diagnostic performance of this invention for programmable metasurfaces with high failure rates. Figure 7 As shown in (b), when the signal-to-noise ratio exceeds 20 dB, it remains below 10 dB within a range of ±60°. -4This demonstrates the angular robustness of the proposed method. In practical test scenarios, by increasing the transmitted signal energy, the signal-to-noise ratio can easily exceed 15dB. Therefore, this invention remains effective under different signal-to-noise ratios, receiving angles, and numbers of faulty units, and requires no multiple measurements or complex signal processing algorithms, making it significantly more practical than traditional methods.

[0086] In summary, the method of this invention maps the working state of a unit to the corresponding orthogonal coded channel energy in the received signal. Based on the energy of each coded channel in the received signal, it determines whether the unit corresponding to the coded channel is faulty, achieving accurate and efficient fault diagnosis. It requires no complex algorithms, special measurement equipment, specific measurement environments, or repeated iterative measurements, and is applicable to non-sparse fault scenarios. It has advantages such as simple implementation, low computational performance requirements, and high robustness, and shows promise for application in practical scenarios such as factory inspection and routine maintenance.

Claims

1. A rapid fault diagnosis method for programmable metasurfaces based on orthogonal coding time-conditioning mechanism, characterized in that: Includes the following steps: Step 1: Apply an independent orthogonal coding time-varying mechanism to each metasurface unit on the programmable metasurface to be diagnosed using a time-varying signal based on orthogonal coding, so that different metasurface units correspond to mutually orthogonal coding channels; Step 2: Illuminate the programmable metasurface to be diagnosed with a single-frequency plane wave, and the reflected signals of different metasurface units are modulated into different orthogonal coding channels; Step 3: Receive the reflected signal from the programmable metasurface to be diagnosed, and recover the energy of each orthogonal coded channel from it; Step 4: Based on the magnitude of the recovered energy of each orthogonal coded channel, determine the faulty metasurface unit.

2. The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning as described in claim 1, characterized in that: The orthogonal code is an orthogonal code sequence that satisfies the following conditions: Condition 1: The encoded sequences are mutually orthogonal; Condition 2: It has time-varying characteristics.

3. The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning as described in claim 1, characterized in that: The time-varying signal of each metasurface unit can be repeatedly orthogonally coded and modulated for multiple cycles within a single measurement time.

4. The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning as described in claim 1, characterized in that: Depending on the requirements, a blank sequence or synchronization sequence may be inserted before orthogonal coding modulation.

5. The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning as described in claim 1, characterized in that: Before step 1, the following steps can also be performed: The programmable metasurface to be diagnosed is partitioned; Perform steps 1 through 4 for each programmable metasurface.

6. The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning as described in claim 1, characterized in that: In step 4, the step of determining the faulty metasurface unit based on the magnitude of the recovered energy of each orthogonal coded channel includes the following specific operations: The fixed threshold determination method is used to determine the faulty metasurface unit based on the magnitude of the recovered energy of each orthogonal coded channel.

7. The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning as described in claim 1, characterized in that: In step 4, the step of determining the faulty metasurface unit based on the magnitude of the recovered energy of each orthogonal coded channel includes the following specific operations: An adaptive clustering algorithm is used to determine the faulty metasurface units based on the magnitude of the recovered energy of each orthogonal coded channel.

8. The method for rapid fault diagnosis of programmable metasurfaces based on orthogonal coding time-conditioning as described in claim 1, characterized in that: The programmable metasurface to be diagnosed only needs to support time modulation function and can be any of the following structures: transmissive, reflective, or active radiative. One or more active devices are integrated on each metasurface unit, and it can operate in any electromagnetic wave frequency band provided that the transceiver system supports it.

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