Reflection-type slot antenna for RFID tag checking

Abstract

The invention discloses a reflective slot antenna for RFID tag inventory, and relates to the technical field of antenna design, the slot antenna design scheme of the invention greatly enhances the directionality and signal coverage capability of the antenna through a phase control algorithm and slot arrangement optimization, and improves the signal coverage capability of the antenna through adjusting the phase difference and the slot spacing. The radiation intensity of the antenna in multiple directions is enhanced, blind areas are effectively reduced, multi-path interference is effectively identified and suppressed through a multi-path signal processing algorithm and an LMS minimum mean square error algorithm, and the antenna can automatically adjust the phase of reflection current and filter reflection signals, so that the signal quality of a complex reflection environment is guaranteed, and the signal quality is improved. In addition, an adaptive array antenna system and a beam forming technology are introduced, so that the antenna can dynamically adjust the phase and amplitude of an array unit according to real-time data fed back by the RFID tag, thereby forming a directional beam, concentrating energy to a specific direction, and improving the recognition precision in a specific area.

Description

Technical Field

[0001] The invention relates to the technical field of antenna design, in particular to a reflective slot antenna for RFID tag inventory. Background Art

[0002] The RFID tag inventory system has very high requirements for antennas. It needs to accurately identify a large number of tags in a large range and maintain stable performance in a complex environment. Reflective slot antennas are widely used in such scenarios due to their good directivity and gain. The reflective slot antenna (RSA) combines the reflective surface and slot structure antenna design, opens a slot on the metal reflective surface, and radiates electromagnetic waves at the slot to achieve directional radiation and gain of the antenna. Specifically, the working principle of the reflective slot antenna is to use the reflective surface to reflect most of the incident electromagnetic waves and radiate through the slot. In RFID inventory applications, the reflective slot antenna generates highly directional and wide-coverage electromagnetic waves through the reflective surface to identify RFID tags within the range.

[0003] In RFID tag inventory, the antenna is required to have a wide coverage range and uniform field distribution to avoid blind spots in recognition. The radiation pattern in the traditional design is relatively concentrated, resulting in limited antenna coverage. It is impossible to achieve uniform tag recognition in a large area or complex storage environment, and it is easy to produce blind spots in recognition. Secondly, the antenna's anti-interference ability is weak in a complex electromagnetic environment, and the multipath effect can easily cause signal reflection and attenuation, which in turn affects the recognition accuracy and system stability. To solve these problems, some traditional solutions increase the number of antennas or adjust the antenna layout to expand the coverage, while improving the antenna gain and optimizing the directivity to reduce the impact of the multipath effect. In some cases, physical shielding materials are used to shield interference. Although these countermeasures have improved performance to a certain extent, they have also increased system complexity, increased deployment difficulty, and increased overall costs.

[0004] Despite this, traditional design solutions are still unable to completely solve the above problems. Increasing the number of antennas or adjusting the antenna layout increases the complexity of antenna synchronization and control, and is prone to cause mutual interference in complex environments, affecting the recognition of some tags. In addition, simply increasing the gain or using shielding materials is not enough to completely eliminate the multipath effect. The signal reflection problem is still prominent in metal shelves or small spaces. Therefore, a design method for a reflective slot antenna for RFID tag inventory is urgently needed to solve such problems. Summary of the invention

[0005] In view of the above existing problems, the present invention is proposed.

[0006] The present invention provides a reflective slot antenna for RFID tag inventory to solve the problem that the current reflective slot antenna design has some limitations when dealing with large-scale, multi-tag identification, and is not effective in dealing with coverage, identification blind spots and multipath effects.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] The present invention provides a reflective slot antenna for RFID tag inventory, which comprises:

[0009] The reflective surface is used to reflect the incident electromagnetic waves and radiate through the gap.

[0010] The slot is the radiation source of the reflective slot antenna. Electromagnetic waves are radiated to the external space through the slot. The slot length, width and reflective surface size of the slot antenna are designed based on the working frequency band of the RFID system.

[0011] The feeding network is used to transmit the radio frequency signal to the antenna, so that the electromagnetic wave radiates to the external space through the gap.

[0012] Periodic structures, using periodic metal or dielectric structures, are deployed around reflective surfaces or gaps:

[0013] The periodic structure on the reflective surface is specifically a metal reflective surface with periodic textures or holes, which is used to further adjust the phase and radiation direction of the electromagnetic wave.

[0014] The dielectric layer structure is specifically a multilayer structure formed by dielectric materials introduced between the reflective surface and the gap. The thickness and arrangement of the dielectric layer are controlled to adjust the radiation frequency range of the antenna.

[0015] Adaptive array control module adjusts the working status of antenna units in real time.

[0016] The frequency switching and broadband control module allows the antenna to automatically switch the operating frequency in different frequency bands and expand its operating bandwidth.

[0017] The radome is used to protect the antenna structure from external dust, moisture and mechanical impact while maintaining electromagnetic radiation performance. The radome is made of plastic or composite material with low dielectric loss.

[0018] Furthermore, the adaptive array control module includes:

[0019] The array control unit controls multiple antenna units in the reflective slot antenna. Each unit forms a directional adjustable beam through phase regulation and amplitude control.

[0020] The feedback loop, combined with real-time feedback data from RFID tags, automatically adjusts the radiation angle, power level and phase of each unit.

[0021] The beamforming unit uses multiple units in the array to work together to form a more directional beam, thereby enhancing the signal strength in a specific area.

[0022] Furthermore, the frequency switching and broadband control module includes:

[0023] The frequency switching unit integrates an electronic tuning circuit. The antenna automatically identifies the working frequency band of the RFID tag and switches to the corresponding working frequency.

[0024] The broadband extension unit expands the antenna operating bandwidth by adjusting the dielectric layer and gap size parameters in the antenna structure.

[0025] Furthermore, the design method of the reflective slot antenna includes:

[0026] Step S1, initial geometry design and parameter definition,

[0027] Based on the operating frequency of the RFID system, the geometric structure of the reflective slot antenna is designed and the initial model is provided.

[0028] Step S2: Directivity optimization and signal coverage adjustment.

[0029] Based on the initial model of step S1, the phase control algorithm is used to adjust the phase of the reflected current in the gap, adjust the arrangement and spacing of the gaps, reduce the blind area during the inventory process, and increase the radiation intensity of the signal in different directions.

[0030] For complex environments, add periodic structures to improve antenna gain and output antenna structures with optimized directivity.

[0031] Step S3, multipath effect suppression and anti-interference,

[0032] Based on the antenna structure optimized in step S2, a multipath signal processing algorithm is used to perform time delay and spatial analysis on the reflected signal received by the antenna to identify and suppress multipath interference caused by reflection.

[0033] Step S4, adaptive array optimization and coverage control,

[0034] Based on the antenna design scheme in step S3, an adaptive array antenna system is constructed, and an adaptive array control algorithm is introduced to dynamically adjust the working state and radiation angle of each antenna unit in the array according to the real-time feedback of RFID tag reading data.

[0035] In step S4, the beamforming technology is combined with the coordinated work of the array antenna to enhance the signal strength in a specific area.

[0036] Step S5: multi-band compatibility and broadband expansion.

[0037] Based on the antenna design scheme in step S4, a frequency switching algorithm is used to enable the antenna to automatically identify the operating frequency of the RFID tag and dynamically switch to the corresponding frequency band.

[0038] In step S5, a broadband adjustment algorithm is used to expand the working bandwidth of the antenna, and a multi-band simulation test is performed to output a final antenna design solution.

[0039] Furthermore, in step S1, the initial model is constructed as follows:

[0040] The basic geometric parameters of the slot antenna are designed based on the working frequency band of the RFID system, including the slot length, width and reflective surface size. The electronic field simulation software HFSS is used to verify the initial geometric design of the antenna, and the initial antenna geometric parameters and the initial model for simulation verification are output.

[0041] Furthermore, in step S1, the initial geometry design and parameter definition are as follows:

[0042] The working frequency f is used to define the central working wavelength of the antenna. Among them, λ is the wavelength of the electromagnetic wave, c is the speed of light, and f is the operating frequency of the antenna.

[0043] Define the gap length as: Among them, L s is the length of the gap,

[0044] Define the gap width as: Among them, W s is the width of the gap, λ is the operating wavelength, and N is a constant with a value between 10 and 20.

[0045] Define the reflective surface size L r and W r , L r =k1λ,W r =k2,L r is the length of the reflecting surface, W r is the width of the reflecting surface, k1 and k2 are multiples of the length and width of the reflecting surface, and range from 1 to 3.

[0046] Define the gap spacing as: Among them, d s is the spacing between adjacent slots, λ is the operating wavelength,

[0047] Define the input impedance matching of the antenna and use the input impedance formula of the slot antenna to calculate:

[0048] Among them, Z in is the input impedance of the antenna, G s is the admittance of the gap, G s According to simulation calculation, the input impedance of the antenna design matches 50 ohms.

[0049] After defining the above geometric parameters, the antenna is verified using the electronic field simulation software HFSS. The simulation steps include:

[0050] Set the operating frequency, enter the design geometry, analyze the antenna’s radiation pattern, gain, and directivity, and optimize the parameters.

[0051] Furthermore, in step S2, based on the initial geometric model in step S1, a phase control algorithm is used to optimize the radiation directivity and coverage of the antenna:

[0052] The purpose of phase control is to adjust the current phase in the slot so that the radiation directivity of the antenna is optimized and the radiation intensity in a specific direction is improved. The current phase difference between adjacent slots determines the change in radiation direction. According to the basic principle of beamforming, the far-field radiation intensity E(θ) of the slot antenna is expressed as:

[0053] Where E(θ) is the radiation intensity in direction θ, N is the total number of gaps, and A n is the amplitude of each gap, taken as the same value, j is the imaginary unit, is the phase constant, λ is the wavelength, d n is the distance between the nth gap and the reference point, θ is the radiation angle, φ n is the phase adjustment of the nth slot,

[0054] The slot spacing is defined as 1 / 2 of the wavelength to avoid excessive side lobes and ensure the energy concentration of the main beam:

[0055] Among them, d n is the distance between the nth slit and the reference point, λ is the operating wavelength,

[0056] Introduce a periodic structure on the reflecting surface, adjust the phase and amplitude of the electromagnetic wave to adjust the antenna performance, and design the periodic structure of the reflecting surface:

[0057] Among them, φ p is the phase shift introduced by the periodic structure, h is the height of the periodic structure, and λ r is the wavelength of the electromagnetic wave in the medium, equal to ∈ r is the relative permittivity of the medium in the periodic structure,

[0058] Optimize the periodic structure and phase control to achieve the antenna gain G. The gain formula is:

[0059] Where G(θ) is the gain in direction θ, A eff is the effective radiation area of ​​the antenna, λ is the wavelength of the electromagnetic wave;

[0060] By adjusting the arrangement and phase of the slots, the directivity of the beam is controlled, thereby reducing the blind area and adjusting the spacing d of the slot arrangement. n , adjust the phase φ of each slit n To optimize the directivity, the beam direction angle θ is calculated as:

[0061] Where θ is the radiation angle of the beam, λ is the operating wavelength, Δφ is the phase difference between adjacent slots, and d n is the gap spacing,

[0062] Therefore, based on phase control and optimization of periodic structure, directional radiation characteristics are obtained, so that the antenna has higher gain and coverage in a specific direction. The antenna structure after directionality optimization is further verified by simulation software.

[0063] Furthermore, in step S3, an interference signal suppression mechanism is introduced, and the interference part in the signal is filtered out in combination with the minimum mean square error LMS algorithm. The signal attenuation and multipath effect of the antenna in different reflection environments are evaluated in a simulation environment, and structural optimization is used for adjustment, and an antenna design scheme with multipath effect suppression capability is output.

[0064] Furthermore, in step S4, based on the antenna design of step S3, an adaptive array antenna system is constructed, and the radiation angle and working state of the antenna unit are dynamically adjusted by combining the adaptive array control algorithm and beamforming technology. Specifically:

[0065] The adaptive array antenna system consists of multiple antenna units, uses phased array technology and beamforming algorithms for dynamic control, and adjusts the working state based on real-time data. The array design:

[0066] Assuming it is a linear array, the total output field strength of the array antenna is E total (θ) is obtained by superposing the contributions of each antenna unit, that is: Among them, E total (θ) is the total radiated field strength in direction θ, N is the number of antenna elements, A n is the amplitude of the nth antenna element, that is, the transmit power of each element, is the phase constant, λ is the wavelength, d n is the distance between the nth antenna unit and the reference point, θ is the radiation angle, φ nis the phase control amount of the nth antenna element,

[0067] Adaptive array control algorithm is used to dynamically adjust the phase and amplitude of each antenna unit in the array according to the real-time feedback of RFID tag reading data. The minimum mean square error (LMS) algorithm is used to dynamically adjust the weight and phase of each antenna unit to minimize the error between the output signal of the antenna array and the expected signal. The update formula of the LMS algorithm is: w(n+1)=w(n)+μx(n)e * (n), where w(n) is the weight vector of the antenna unit at the nth iteration, i.e., amplitude and phase, μ is the learning rate, which controls the step size of the update, x(n) is the input signal vector at the nth iteration, i.e., the feedback signal of the RFID tag, e * (n) is the conjugate value of the error signal at the nth iteration,

[0068] Beamforming technology is used to adjust the phase and amplitude of each antenna unit in the array to form a beam pointing in a specific direction and enhance the signal strength in a specific area. The phase and amplitude of each antenna unit control the radiation angle of the beam.

[0069] Assuming that the beam needs to be concentrated in the direction θ0, the phase control formula is:

[0070] φ n =-βd n sin(θ0), where φ n is the phase of the nth antenna element, is the phase constant, d n is the distance between the nth antenna element and the reference point, θ0 is the angle of the desired beam focus direction,

[0071] To enhance the signal strength, beamforming is used to concentrate the radiation energy of the antenna in the target area and enhance the signal strength in a specific area. The antenna gain G(θ) is calculated as follows:

[0072] Where G(θ) is the gain in direction θ, G max is the maximum gain of the antenna array, N is the number of antenna elements, is the phase constant, d is the antenna element spacing, θ is the radiation angle,

[0073] Adopting adaptive array control algorithm, it responds to the feedback information read by RFID tags in real time and dynamically adjusts the phase and amplitude of each unit.

[0074] Furthermore, in step S5, a frequency switching algorithm and a broadband adjustment algorithm are used to expand the working bandwidth of the antenna:

[0075] The frequency switching algorithm is used to automatically identify the working frequency of the RFID tag through the antenna system, and dynamically adjust the working state of the antenna according to different frequency bands.

[0076] According to the feedback signal of the RFID tag, the frequency spectrum of the signal is analyzed by Fourier transform to determine the working frequency of the tag. The frequency recognition formula is:

[0077] Where F(f) is the spectrum of the signal, s(t) is the time domain signal emitted by the RFID tag, f is the frequency, and t is the time.

[0078] After Fourier transform, the returned RFID tag signal s(t) is analyzed to determine the main frequency component f, that is, the tag's operating frequency. After identifying the frequency f, the antenna switches to the corresponding operating frequency band, and the antenna's resonant frequency f r The relationship with the size of the slot antenna is: Among them, f r is the resonant frequency of the antenna, c is the speed of light, L slot is the length of the gap, ∈ r is the relative permittivity of the medium,

[0079] A broadband adjustment algorithm is introduced to adjust the slot length, width and dielectric material parameters in the antenna structure to expand the working bandwidth. The relationship between bandwidth, resonant frequency and quality factor is defined as:

[0080] Where B is the bandwidth of the antenna, f r is the resonant frequency of the antenna, Q is the quality factor of the antenna,

[0081] The broadband adjustment formula is: Where Q is the quality factor of the antenna, f r is the resonant frequency, L slot is the gap length, R s is the radiation resistance of the antenna,

[0082] Adjust the gap length L slot and the antenna radiation resistance R s , dynamically expand the antenna's working bandwidth B,

[0083] Then, multi-band simulation tests are performed using the simulation software HFSS to verify the radiation pattern, gain and directivity of the antenna and calculate the reflection coefficient S 11 (f) Test the matching of the antenna at different frequencies: Among them, S 11 (f) is the reflection coefficient at frequency f, Z in(f) is the input impedance of the antenna at frequency f, and Z0 is the characteristic impedance of the system. Through the frequency switching algorithm, the antenna can automatically identify different RFID tag operating frequencies and adjust the gap size and structure. At the same time, the broadband adjustment algorithm expands the working bandwidth of the antenna by adjusting the gap structure and antenna material. On this basis, multi-band simulation tests are carried out to enable the antenna to maintain good matching and radiation performance in different frequency bands.

[0084] The beneficial effects of the present invention are:

[0085] The present invention adopts a slot antenna design scheme that greatly enhances the directivity and signal coverage capability of the antenna through a phase control algorithm and slot arrangement optimization. By adjusting the phase difference and slot spacing, the radiation intensity of the antenna in multiple directions is enhanced, effectively reducing blind spots.

[0086] The present invention effectively identifies and suppresses multipath interference through a multipath signal processing algorithm and an LMS minimum mean square error algorithm. The antenna can automatically adjust the phase of the reflected current and filter the reflected signal, thereby ensuring the signal quality in a complex reflection environment.

[0087] The present invention introduces an adaptive array antenna system and beamforming technology, so that the antenna can dynamically adjust the phase and amplitude of the array unit according to the real-time data fed back by the RFID tag, thereby forming a directional beam, concentrating energy in a specific direction, and improving the recognition accuracy in a specific area.

[0088] The present invention introduces a frequency switching algorithm and a broadband adjustment algorithm to enable the antenna to automatically identify the operating frequency of the RFID tag and dynamically switch between different frequency bands. In addition, the broadband adjustment algorithm further expands the operating bandwidth and enhances the matching performance of the antenna in a wide frequency range by optimizing the antenna geometry and materials.

[0089] The present invention, through the interference signal suppression mechanism and the minimum mean square error LMS algorithm, can identify and suppress external interference signals in real time, effectively improve the anti-interference ability of the system, work more stably in a multi-label and high-density environment, and reduce signal collision and interference.

[0090] The present invention, through an adaptive array control algorithm and beamforming technology, can achieve flexible coverage control without increasing the number of antennas, thereby simplifying system deployment and reducing overall costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0092] Figure 1 A schematic diagram of the design process of the reflective slot antenna of the present invention;

[0093] Figure 2 It is a schematic diagram of the structure of the reflective slot antenna of the present invention. DETAILED DESCRIPTION

[0094] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0095] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0096] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0097] Example 1, reference Figure 1 and Figure 2 , this embodiment provides a reflective slot antenna for RFID tag inventory, including:

[0098] The reflective surface is used to reflect the incident electromagnetic waves and radiate through the gap.

[0099] The slot is the radiation source of the reflective slot antenna. Electromagnetic waves are radiated to the external space through the slot. The slot length, width and reflective surface size of the slot antenna are designed based on the working frequency band of the RFID system.

[0100] The feeding network is used to transmit the radio frequency signal to the antenna, so that the electromagnetic wave radiates to the external space through the gap.

[0101] Periodic structures, using periodic metal or dielectric structures, are deployed around reflective surfaces or gaps:

[0102] The periodic structure on the reflective surface is specifically a metal reflective surface with periodic textures or holes, which is used to further adjust the phase and radiation direction of the electromagnetic wave.

[0103] The dielectric layer structure is specifically a multilayer structure formed by dielectric materials introduced between the reflective surface and the gap. The thickness and arrangement of the dielectric layer are controlled to adjust the radiation frequency range of the antenna.

[0104] Adaptive array control module adjusts the working status of antenna units in real time.

[0105] The adaptive array control module includes:

[0106] The array control unit controls multiple antenna units in the reflective slot antenna. Each unit forms a directional adjustable beam through phase regulation and amplitude control.

[0107] The feedback loop, combined with real-time feedback data from RFID tags, automatically adjusts the radiation angle, power level and phase of each unit.

[0108] The beamforming unit uses multiple units in the array to work together to form a more directional beam, thereby enhancing the signal strength in a specific area.

[0109] The frequency switching and broadband control module allows the antenna to automatically switch the operating frequency in different frequency bands and expand its operating bandwidth.

[0110] The frequency switching and broadband control module includes:

[0111] The frequency switching unit integrates an electronic tuning circuit. The antenna automatically identifies the working frequency band of the RFID tag and switches to the corresponding working frequency.

[0112] The broadband extension unit expands the antenna operating bandwidth by adjusting the dielectric layer and gap size parameters in the antenna structure.

[0113] The radome is used to protect the antenna structure from external dust, moisture and mechanical impact while maintaining electromagnetic radiation performance. The radome is made of plastic or composite material with low dielectric loss.

[0114] The design of the reflective slot antenna is as follows:

[0115] Step S1, initial geometry design and parameter definition,

[0116] Based on the operating frequency of the RFID system, the geometric structure of the reflective slot antenna is designed and the initial model is provided.

[0117] In step S1, the initial model is constructed as follows:

[0118] Design the basic geometric parameters of the slot antenna based on the working frequency band of the RFID system, including the slot length, width and reflective surface size. Use the electronic field simulation software HFSS to verify the initial geometric design of the antenna, output the initial antenna geometric parameters and simulate and verify the initial model.

[0119] In step S1, the initial geometry design and parameter definition are as follows:

[0120] The working frequency f is used to define the central working wavelength of the antenna. Among them, λ is the wavelength of the electromagnetic wave, c is the speed of light, and f is the operating frequency of the antenna.

[0121] Define the gap length as: Among them, L s is the length of the gap,

[0122] Define the gap width as: Among them, W s is the width of the gap, λ is the operating wavelength, and N is a constant with a value between 10 and 20.

[0123] Define the reflective surface size L r and W r , L r =k1λ,W r =k2,L r is the length of the reflecting surface, W r is the width of the reflecting surface, k1 and k2 are multiples of the length and width of the reflecting surface, and range from 1 to 3.

[0124] Define the gap spacing as: Among them, d s is the spacing between adjacent slots, λ is the operating wavelength,

[0125] Define the input impedance matching of the antenna and use the input impedance formula of the slot antenna to calculate:

[0126] Among them, Z in is the input impedance of the antenna, G s is the admittance of the gap, G s According to simulation calculation, the input impedance of the antenna design matches 50 ohms.

[0127] After defining the above geometric parameters, the antenna is verified using the electronic field simulation software HFSS. The simulation steps include:

[0128] Set the operating frequency, input the designed geometric parameters, analyze the antenna's radiation pattern, gain and directivity, and optimize the parameters;

[0129] Specifically, a phase control algorithm is used to adjust the phase of the reflected current in the gap to enhance the radiation directivity of the antenna. On this basis, the antenna beam is concentrated in a specific direction through the arrangement and spacing of the gaps, reducing the recognition blind spot and improving the coverage and accuracy of the antenna, which is suitable for complex warehousing environments and large-scale Internet of Things scenarios.

[0130] Step S2: Directivity optimization and signal coverage adjustment.

[0131] Based on the initial model of step S1, the phase control algorithm is used to adjust the phase of the reflected current in the gap, adjust the arrangement and spacing of the gaps, reduce the blind area during the inventory process, and increase the radiation intensity of the signal in different directions.

[0132] For complex environments, add periodic structures to improve antenna gain and output antenna structures with optimized directivity.

[0133] In step S2, based on the initial geometric model in step S1, a phase control algorithm is used to optimize the radiation directivity and coverage of the antenna:

[0134] The purpose of phase control is to adjust the current phase in the slot so that the radiation directivity of the antenna is optimized and the radiation intensity in a specific direction is improved. The current phase difference between adjacent slots determines the change in radiation direction. According to the basic principle of beamforming, the far-field radiation intensity E(θ) of the slot antenna is expressed as:

[0135] Where E(θ) is the radiation intensity in direction θ, N is the total number of gaps, and A n is the amplitude of each gap, taken as the same value, j is the imaginary unit, is the phase constant, λ is the wavelength, d n is the distance between the nth gap and the reference point, θ is the radiation angle, φ n is the phase adjustment of the nth slot,

[0136] Assume that the antenna is designed with four slots, and the wavelength λ = 0.327m, and the slot spacing d n =0.164m, then by adjusting the phase of each slot φ n , control the directivity of the beam. If φ1=0°, φ2=90°, φ3=180°, φ4=270°, the radiation beam of the antenna will be enhanced in a specific direction.

[0137] The slot spacing is defined as 1 / 2 of the wavelength to avoid excessive side lobes and ensure the energy concentration of the main beam:

[0138] Among them, d n is the distance between the nth slit and the reference point, λ is the operating wavelength,

[0139] Introduce a periodic structure on the reflecting surface, adjust the phase and amplitude of the electromagnetic wave to adjust the antenna performance, and design the periodic structure of the reflecting surface:

[0140] Among them, φ p is the phase shift introduced by the periodic structure, h is the height of the periodic structure, and λ r is the wavelength of the electromagnetic wave in the medium, equal to ∈ r is the relative permittivity of the medium in the periodic structure,

[0141] Assume that the dielectric constant ∈ r =2.2, wavelength λ = 0.327m, if the periodic structure height h = 0.05m, then the phase shift introduced in the periodic structure is: The arc helps to adjust the phase of electromagnetic waves at different positions on the reflecting surface and enhance the gain of the antenna.

[0142] Optimize the periodic structure and phase control to achieve the antenna gain G. The gain formula is:

[0143] Where G(θ) is the gain in direction θ, A eff is the effective radiation area of ​​the antenna, λ is the wavelength of the electromagnetic wave,

[0144] Assume that the effective radiation area of ​​the antenna is A eff =0.1m 2 , and the wavelength is λ = 0.327m, then the antenna gain in the main beam direction is:

[0145] That is, the gain of the antenna in the main beam direction is 11.7dBi, indicating that the antenna has strong directivity and can be used to cover a longer range during the inventory process;

[0146] By adjusting the arrangement and phase of the slots, the directivity of the beam is controlled, thereby reducing the blind area and adjusting the spacing d of the slot arrangement. n , adjust the phase φ of each slit n To optimize the directivity, the beam direction angle θ is calculated as:

[0147] Where θ is the radiation angle of the beam, λ is the operating wavelength, Δφ is the phase difference between adjacent slots, and d n is the gap spacing,

[0148] For example, in the gap spacing d n =0.164m, wavelength λ=0.327m, if the phase difference Δφ=90°, the radiation angle of the main beam is: That is, the direction of the main beam is 30 degrees, which can effectively reduce the blind spots in the coverage area;

[0149] Based on the phase control and periodic structure optimization, directional radiation characteristics are obtained, so that the antenna has higher gain and coverage in a specific direction. The antenna structure after directivity optimization is further verified by simulation software.

[0150] Step S3, multipath effect suppression and anti-interference,

[0151] Based on the antenna structure optimized in step S2, a multipath signal processing algorithm is used to perform time delay and spatial analysis on the reflected signal received by the antenna to identify and suppress multipath interference caused by reflection.

[0152] In step S3, an interference signal suppression mechanism is introduced, and the interference part in the signal is filtered out by combining the minimum mean square error LMS algorithm. The signal attenuation and multipath effect of the antenna in different reflection environments are evaluated in a simulation environment, and structural optimization is used for adjustment to output an antenna design scheme with multipath effect suppression capability.

[0153] Specifically, the minimum mean square error LMS algorithm and multipath signal processing algorithm are introduced to effectively identify and suppress interference signals caused by reflections. The dynamic phase adjustment and current control are adopted, which can adapt to different reflection environments in practical applications, greatly reduce signal attenuation and interference problems, and improve the stability and accuracy of the RFID system.

[0154] Step S4, adaptive array optimization and coverage control,

[0155] Based on the antenna design scheme in step S3, an adaptive array antenna system is constructed, and an adaptive array control algorithm is introduced to dynamically adjust the working state and radiation angle of each antenna unit in the array according to the real-time feedback of RFID tag reading data.

[0156] In step S4, the beamforming technology is combined with the coordinated work of the array antenna to enhance the signal strength in a specific area.

[0157] In step S4, based on the antenna design of step S3, an adaptive array antenna system is constructed, and the radiation angle and working state of the antenna unit are dynamically adjusted by combining the adaptive array control algorithm and beamforming technology. Specifically:

[0158] The adaptive array antenna system consists of multiple antenna units, uses phased array technology and beamforming algorithms for dynamic control, and adjusts the working state based on real-time data. The array design:

[0159] Assuming it is a linear array, the total output field strength of the array antenna is E total (θ) is obtained by superposing the contributions of each antenna unit, that is: Among them, E total (θ) is the total radiated field strength in direction θ, N is the number of antenna elements, A n is the amplitude of the nth antenna element, that is, the transmit power of each element, is the phase constant, λ is the wavelength, d n is the distance between the nth antenna unit and the reference point, θ is the radiation angle, φ nis the phase control amount of the nth antenna element,

[0160] Adaptive array control algorithm is used to dynamically adjust the phase and amplitude of each antenna unit in the array according to the real-time feedback of RFID tag reading data. The minimum mean square error (LMS) algorithm is used to dynamically adjust the weight and phase of each antenna unit to minimize the error between the output signal of the antenna array and the expected signal. The update formula of the LMS algorithm is: w(n+1)=w(n)+μx(n)e * (n), where w(n) is the weight vector of the antenna unit at the nth iteration, i.e., amplitude and phase, μ is the learning rate, which controls the step size of the update, x(n) is the input signal vector at the nth iteration, i.e., the feedback signal of the RFID tag, e * (n) is the conjugate value of the error signal at the nth iteration,

[0161] Beamforming technology is used to adjust the phase and amplitude of each antenna unit in the array to form a beam pointing in a specific direction and enhance the signal strength in a specific area. The phase and amplitude of each antenna unit control the radiation angle of the beam.

[0162] Assuming that the beam needs to be concentrated in the direction θ0, the phase control formula is:

[0163] φ n =-βd n sin(θ0), where φ n is the phase of the nth antenna element, is the phase constant, d n is the distance between the nth antenna element and the reference point, θ0 is the angle of the desired beam focus direction,

[0164] To enhance the signal strength, beamforming is used to concentrate the radiation energy of the antenna in the target area and enhance the signal strength in a specific area. The antenna gain G(θ) is calculated as follows:

[0165] Where G(θ) is the gain in direction θ, G max is the maximum gain of the antenna array, N is the number of antenna elements, is the phase constant, d is the antenna element spacing, θ is the radiation angle,

[0166] Adopting adaptive array control algorithm, it responds to the feedback information read by RFID tags in real time and dynamically adjusts the phase and amplitude of each unit;

[0167] Specifically, the introduction of the adaptive array antenna system has greatly improved the flexibility and intelligence level of the antenna. It dynamically adjusts the phase and amplitude of the antenna unit through real-time feedback of RFID tag data to form a directional beam and concentrate energy in a specific area, thereby enhancing the signal strength in the area. In a dense RFID tag environment, it improves the reading success rate and reduces signal collisions and interference.

[0168] Step S5: multi-band compatibility and broadband expansion.

[0169] Based on the antenna design scheme in step S4, a frequency switching algorithm is used to enable the antenna to automatically identify the operating frequency of the RFID tag and dynamically switch to the corresponding frequency band.

[0170] In step S5, a broadband adjustment algorithm is used to expand the working bandwidth of the antenna, and a multi-band simulation test is performed to output a final antenna design solution;

[0171] In step S5, a frequency switching algorithm and a broadband adjustment algorithm are used to expand the working bandwidth of the antenna:

[0172] The frequency switching algorithm is used to automatically identify the working frequency of the RFID tag through the antenna system, and dynamically adjust the working state of the antenna according to different frequency bands.

[0173] According to the feedback signal of the RFID tag, the frequency spectrum of the signal is analyzed by Fourier transform to determine the working frequency of the tag. The frequency recognition formula is:

[0174] Where F(f) is the spectrum of the signal, s(t) is the time domain signal emitted by the RFID tag, f is the frequency, and t is the time.

[0175] After Fourier transform, the returned RFID tag signal s(t) is analyzed to determine the main frequency component f, that is, the tag's operating frequency. After identifying the frequency f, the antenna switches to the corresponding operating frequency band, and the antenna's resonant frequency f r The relationship with the size of the slot antenna is: Among them, f r is the resonant frequency of the antenna, c is the speed of light, L slot is the length of the gap, ∈ r is the relative permittivity of the medium,

[0176] A broadband adjustment algorithm is introduced to adjust the slot length, width and dielectric material parameters in the antenna structure to expand the working bandwidth. The relationship between bandwidth, resonant frequency and quality factor is defined as:

[0177] Where B is the bandwidth of the antenna, f r is the resonant frequency of the antenna, Q is the quality factor of the antenna,

[0178] The broadband adjustment formula is: Where Q is the quality factor of the antenna, f r is the resonant frequency, L slot is the gap length, R s is the radiation resistance of the antenna,

[0179] Adjust the gap length L slot and the antenna radiation resistance R s , dynamically expand the antenna's working bandwidth B,

[0180] Then, multi-band simulation tests are performed using the simulation software HFSS to verify the radiation pattern, gain and directivity of the antenna and calculate the reflection coefficient S 11 (f) Test the matching of the antenna at different frequencies: Among them, S 11 (f) is the reflection coefficient at frequency f, Z in (f) is the input impedance of the antenna at frequency f, and Z0 is the characteristic impedance of the system. Through the frequency switching algorithm, the antenna can automatically identify different RFID tag operating frequencies and adjust the gap size and structure. At the same time, the broadband adjustment algorithm expands the working bandwidth of the antenna by adjusting the gap structure and antenna material. On this basis, multi-band simulation tests are carried out to enable the antenna to maintain good matching and radiation performance in different frequency bands.

[0181] Specifically, a frequency switching algorithm is used to enable the antenna to automatically identify the operating frequency of the RFID tag and dynamically adjust to the appropriate frequency band to achieve multi-band compatibility.

[0182] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A reflective slot antenna for RFID tag inventory, characterized in that: include, The reflective surface is used to reflect the incident electromagnetic waves and radiate through the gap. The slot is the radiation source of the reflective slot antenna. Electromagnetic waves are radiated to the external space through the slot. The slot length, width and reflective surface size of the slot antenna are designed based on the working frequency band of the RFID system. The feeding network is used to transmit the radio frequency signal to the antenna, so that the electromagnetic wave radiates to the external space through the gap. Periodic structures, using periodic metal or dielectric structures, are deployed around reflective surfaces or gaps: The periodic structure on the reflective surface is specifically a metal reflective surface with periodic textures or holes, which is used to further adjust the phase and radiation direction of the electromagnetic wave. The dielectric layer structure is specifically a multilayer structure formed by dielectric materials introduced between the reflective surface and the gap. The thickness and arrangement of the dielectric layer are controlled to adjust the radiation frequency range of the antenna. Adaptive array control module adjusts the working status of antenna units in real time. The frequency switching and broadband control module allows the antenna to automatically switch the operating frequency in different frequency bands and expand its operating bandwidth. The radome is used to protect the antenna structure from external dust, moisture and mechanical impact while maintaining electromagnetic radiation performance. The radome is made of plastic or composite material with low dielectric loss.

2. The reflective slot antenna for RFID tag inventory according to claim 1, characterized in that: The adaptive array control module includes: The array control unit controls multiple antenna units in the reflective slot antenna. Each unit forms a directional adjustable beam through phase regulation and amplitude control. The feedback loop, combined with real-time feedback data from RFID tags, automatically adjusts the radiation angle, power level and phase of each unit. The beamforming unit uses multiple units in the array to work together to form a more directional beam, thereby enhancing the signal strength in a specific area.

3. The reflective slot antenna for RFID tag inventory according to claim 2, characterized in that: The frequency switching and broadband control module includes: The frequency switching unit integrates an electronic tuning circuit. The antenna automatically identifies the working frequency band of the RFID tag and switches to the corresponding working frequency. The broadband extension unit expands the antenna operating bandwidth by adjusting the dielectric layer and gap size parameters in the antenna structure.

4. The reflective slot antenna for RFID tag inventory according to claim 3, characterized in that: The design methods of reflective slot antenna include: Step S1, initial geometry design and parameter definition, Based on the operating frequency of the RFID system, the geometric structure of the reflective slot antenna is designed and the initial model is provided. Step S2: Directivity optimization and signal coverage adjustment. Based on the initial model of step S1, a phase control algorithm is used to adjust the phase of the reflected current in the gap and adjust the arrangement and spacing of the gaps. For complex environments, add periodic structures to improve antenna gain and output antenna structures with optimized directivity. Step S3, multipath effect suppression and anti-interference, Based on the antenna structure optimized in step S2, a multipath signal processing algorithm is used to perform time delay and spatial analysis on the reflected signal received by the antenna to identify and suppress multipath interference caused by reflection. Step S4, adaptive array optimization and coverage control, Based on the antenna design scheme in step S3, an adaptive array antenna system is constructed, and an adaptive array control algorithm is introduced to dynamically adjust the working state and radiation angle of each antenna unit in the array according to the real-time feedback of RFID tag reading data. In step S4, the beamforming technology is combined with the coordinated work of the array antenna to enhance the signal strength in a specific area. Step S5, multi-band compatibility and broadband extension, Based on the antenna design scheme in step S4, a frequency switching algorithm is used to enable the antenna to automatically identify the operating frequency of the RFID tag and dynamically switch to the corresponding frequency band. In step S5, a broadband adjustment algorithm is used to expand the working bandwidth of the antenna, and a multi-band simulation test is performed to output a final antenna design solution.

5. The reflective slot antenna for RFID tag inventory according to claim 4, characterized in that: In step S1, the initial model is constructed as follows: The basic geometric parameters of the slot antenna are designed based on the working frequency band of the RFID system, including the slot length, width and reflective surface size. The electronic field simulation software HFSS is used to verify the initial geometric design of the antenna, and the initial antenna geometric parameters and the initial model for simulation verification are output.

6. The reflective slot antenna for RFID tag inventory according to claim 5, characterized in that: In step S1, the initial geometry design and parameter definition are as follows: The working frequency f is used to define the central working wavelength of the antenna. Among them, λ is the wavelength of the electromagnetic wave, c is the speed of light, and f is the operating frequency of the antenna. Define the gap length as: Among them, L s is the length of the gap, Define the gap width as: Among them, W s is the width of the gap, λ is the operating wavelength, and N is a constant with a value between 10 and 20. Define the reflective surface size L r and W r , L r =k1λ,W r =k2,L r is the length of the reflecting surface, W r is the width of the reflecting surface, k1 and k2 are multiples of the length and width of the reflecting surface, and range from 1 to 3. Define the gap spacing as: Among them, d s is the spacing between adjacent slots, λ is the operating wavelength, Define the input impedance matching of the antenna and use the input impedance formula of the slot antenna to calculate: Among them, Z in is the input impedance of the antenna, G s is the admittance of the gap, G s According to simulation calculation, the input impedance of the antenna design matches 50 ohms. After defining the above geometric parameters, the antenna is verified using the electronic field simulation software HFSS. The simulation steps include: Set the operating frequency, enter the design geometry, analyze the antenna’s radiation pattern, gain, and directivity, and optimize the parameters.

7. The reflective slot antenna for RFID tag inventory according to claim 6, characterized in that: In step S2, based on the initial geometric model in step S1, a phase control algorithm is used to optimize the radiation directivity and coverage of the antenna: The far-field radiation intensity E(θ) of the slot antenna is expressed as: Where E(θ) is the radiation intensity in direction θ, N is the total number of gaps, and A n is the amplitude of each gap, taken as the same value, j is the imaginary unit, is the phase constant, λ is the wavelength, d n is the distance between the nth gap and the reference point, θ is the radiation angle, φ n is the phase adjustment of the nth slot, The gap spacing is defined as 1 / 2 of the wavelength to ensure the energy concentration of the main beam: Among them, d n is the distance between the nth slit and the reference point, λ is the operating wavelength, Introduce a periodic structure on the reflecting surface, adjust the phase and amplitude of the electromagnetic wave to adjust the antenna performance, and design the periodic structure of the reflecting surface: Among them, φ p is the phase shift introduced by the periodic structure, h is the height of the periodic structure, and λ r is the wavelength of the electromagnetic wave in the medium, equal to ∈ r is the relative permittivity of the medium in the periodic structure, Optimize the periodic structure and phase control to achieve the antenna gain G. The gain formula is: Where G(θ) is the gain in direction θ, A eff is the effective radiation area of ​​the antenna, λ is the wavelength of the electromagnetic wave, Adjust the spacing d of the gap arrangement n , adjust the phase φ of each slit n To optimize the directivity, the beam direction angle θ is calculated as: Where θ is the radiation angle of the beam, λ is the operating wavelength, Δφ is the phase difference between adjacent slots, and d n is the gap spacing.

8. The reflective slot antenna for RFID tag inventory according to claim 7, characterized in that: In step S3, an interference signal suppression mechanism is introduced, and the interference part in the signal is filtered out by combining the minimum mean square error LMS algorithm. The signal attenuation and multipath effect of the antenna in different reflection environments are evaluated in a simulation environment, and structural optimization is used for adjustment, and an antenna design scheme with multipath effect suppression capability is output.

9. The reflective slot antenna for RFID tag inventory according to claim 8, characterized in that: In step S4, based on the antenna design of step S3, an adaptive array antenna system is constructed, and the radiation angle and working state of the antenna unit are dynamically adjusted by combining the adaptive array control algorithm and beamforming technology. Specifically: The adaptive array antenna system consists of multiple antenna units, uses phased array technology and beamforming algorithms for dynamic control, and adjusts the working state based on real-time data. The array design: Assuming it is a linear array, the total output field strength of the array antenna is E total (θ) is obtained by superposing the contributions of each antenna unit, that is: Among them, E total (θ) is the total radiated field strength in direction θ, N is the number of antenna elements, A n is the amplitude of the nth antenna element, that is, the transmit power of each element, is the phase constant, λ is the wavelength, d n is the distance between the nth antenna unit and the reference point, θ is the radiation angle, φ n is the phase control amount of the nth antenna element, Adaptive array control algorithm is used to dynamically adjust the phase and amplitude of each antenna unit in the array according to the real-time feedback of RFID tag reading data. The minimum mean square error (LMS) algorithm is used to dynamically adjust the weight and phase of each antenna unit to minimize the error between the output signal of the antenna array and the expected signal. The update formula of the LMS algorithm is: w(n+1)=w(n)+μx(n)e * (n), where w(n) is the weight vector of the antenna unit at the nth iteration, i.e., amplitude and phase, μ is the learning rate, controlling the step size of the update, x(n) is the input signal vector at the nth iteration, i.e., the feedback signal of the RFID tag, and e*(n) is the conjugate value of the error signal at the nth iteration. Assuming that the beam needs to be concentrated in the direction θ0, the phase control formula is: φ n =-βd n sin(θ0), where φ n is the phase of the nth antenna element, is the phase constant, d n is the distance between the nth antenna element and the reference point, θ0 is the angle of the desired beam focus direction, To enhance the signal strength, beamforming is used to concentrate the radiation energy of the antenna in the target area and enhance the signal strength in a specific area. The antenna gain G(θ) is calculated as follows: Where G(θ) is the gain in direction θ, G max is the maximum gain of the antenna array, N is the number of antenna elements, is the phase constant, d is the antenna element spacing, θ is the radiation angle, Adopting adaptive array control algorithm, it responds to the feedback information read by RFID tags in real time and dynamically adjusts the phase and amplitude of each unit.

10. The reflective slot antenna for RFID tag inventory according to claim 9, characterized in that: In step S5, a frequency switching algorithm and a broadband adjustment algorithm are used to expand the working bandwidth of the antenna: The frequency switching algorithm is used to automatically identify the working frequency of the RFID tag through the antenna system, and dynamically adjust the working state of the antenna according to different frequency bands. According to the feedback signal of the RFID tag, the frequency spectrum of the signal is analyzed by Fourier transform to determine the working frequency of the tag. The frequency recognition formula is: Where F(f) is the spectrum of the signal, s(t) is the time domain signal emitted by the RFID tag, f is the frequency, and t is the time. After Fourier transform, the returned RFID tag signal s(t) is analyzed to determine the main frequency component f, that is, the tag's operating frequency. After identifying the frequency f, the antenna switches to the corresponding operating frequency band, and the antenna's resonant frequency f r The relationship with the size of the slot antenna is: Among them, f r is the resonant frequency of the antenna, c is the speed of light, L slot is the length of the gap, ∈ r is the relative permittivity of the medium, A broadband adjustment algorithm is introduced to adjust the slot length, width and dielectric material parameters in the antenna structure to expand the working bandwidth. The relationship between bandwidth, resonant frequency and quality factor is defined as: Where B is the bandwidth of the antenna, f r is the resonant frequency of the antenna, Q is the quality factor of the antenna, The broadband adjustment formula is: Where Q is the quality factor of the antenna, f r is the resonant frequency, L slot is the gap length, R s is the radiation resistance of the antenna, Adjust the gap length L slot and the antenna radiation resistance R s , dynamically expand the antenna's working bandwidth B, Then, multi-band simulation tests are performed using the simulation software HFSS to verify the radiation pattern, gain and directivity of the antenna and calculate the reflection coefficient S 11 (f) Test the matching of the antenna at different frequencies: Among them, S 11 (f) is the reflection coefficient at frequency f, Z in (f) is the input impedance of the antenna at frequency f, and Z0 is the characteristic impedance of the system.

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