Ultra-large octave antenna based on organic photoconductive material

Abstract

The invention discloses an ultra-large octave antenna based on an organic photoconductive material, and belongs to the field of metamaterials and antennas. Comprising an organic photoconductor film electromagnetic surface and a digital light processing module capable of projecting different patterns on the surface of the organic photoconductor film electromagnetic surface, the organic photoconductor film electromagnetic surface can change conductivity distribution through light control, and the digital light processing module can dynamically adjust the size and shape of the patterns projected on the organic photoconductor film electromagnetic surface. Therefore, a reconfigurable antenna array is generated, and cross-multi-octave ultra-wideband electromagnetic wave signal receiving and transmitting are realized. The electromagnetic surface of the organic photoconductor film sequentially comprises a photoconductive material layer, a first light-transmitting glass layer, an indium tin oxide microstrip line feed layer, a second light-transmitting glass layer and a substrate indium tin oxide layer according to a lamination sequence. According to the invention, the problems of narrow bandwidth, slow response and high cost of a traditional reconfigurable antenna are solved.

Description

Technical Field

[0001] The present invention belongs to the field of metamaterials and antennas, and particularly relates to an ultra-wide octave antenna based on an organic photoconductive material. Background Art

[0002] With the gradual deepening of the impact of globalization, the development of all walks of life has been inseparable from the communication industry. The development of communication technology not only promotes the rapid development of national science and technology and economy, but also has become the most popular research topic in China and even the world. With the proposal and implementation of major national strategies such as "Internet +", Internet of Things, smart city and big data, and the rapid development of new generation wireless communication technologies such as fifth-generation mobile communication, sixth-generation mobile communication, point-to-point communication, terahertz communication, and intelligent communication, people hope that the devices in their hands can work in multiple frequency bands and there will be no interference between these devices. This demand makes wireless communication booming while the already increasingly crowded spectrum resources are facing more and more arduous challenges. Since the ultra-wideband communication system has characteristics such as a very wide operating bandwidth, fast data transmission, strong anti-multipath ability, and high security performance, it has rapidly become a new type of wireless communication technology with great development potential after being proposed in the 1990s and is listed as one of the top ten future communication technologies.

[0003] As an important component of the ultra-wideband system, the ultra-wideband antenna has an important impact on the working performance of the system. Therefore, how to design and implement an ultra-wideband antenna with excellent performance has become an important aspect of the ultra-wideband communication system. In addition, wireless communication systems are developing towards miniaturization, ultra-wideband and functional diversification to meet the continuously increasing application requirements in practice. The existing reconfigurable antenna technologies are basically divided into: based on switch systems and tuning circuits, based on mechanical or microelectromechanical systems (MEMS), based on tuning materials, based on metasurfaces and graphene, etc. The design and implementation of the above-mentioned several reconfigurable antennas require complex electromagnetic theories and radio frequency circuit designs, and precise control of the physical structure and electrical parameters of the antenna, etc. The response speed and power consumption caused by continuous switching are also issues that need to be carefully considered. Summary of the Invention

[0004] Technical Problems to be Solved

[0005] In order to avoid the deficiencies of the prior art, the present invention provides an ultra-wide octave antenna based on an organic photoconductive material, which combines the dielectric-metal state light control characteristics of the photoconductive material with digital light processing (DLP) technology to generate a reconfigurable antenna array by dynamic projection on the photoconductive thin film. The present invention solves the problems of narrow bandwidth, slow response and high cost of traditional reconfigurable antennas, provides an efficient, flexible and economical solution for future ultra-wideband communication systems, and has broad application prospects in the fields of 6G, Internet of Things, terahertz communication, etc.

[0006] The technical solution of the present invention is: an ultra-large octave antenna based on an organic photoconductive material, including an organic photoconductor thin-film electromagnetic surface and a digital light processing module capable of projecting different patterns on its surface. The conductivity distribution of the organic photoconductor thin-film electromagnetic surface can be changed by light control. The digital light processing module can dynamically adjust the pattern size and shape projected on the organic photoconductor thin-film electromagnetic surface to generate a reconfigurable antenna array, realizing the transceiver of ultra-wideband electromagnetic wave signals across multiple octaves.

[0007] The organic photoconductor thin-film electromagnetic surface sequentially includes a photoconductive material layer, a first transparent glass layer, an indium tin oxide microstrip line feeding layer, a second transparent glass layer, and a substrate indium tin oxide layer in a laminated order.

[0008] A further technical solution of the present invention is: the thickness of the photoconductive material layer of the organic photoconductor thin-film electromagnetic surface is 50 - 200 nm; the light transmittance of the first transparent glass layer > 95%, and the thickness is 1 - 3 mm; the sheet resistance of the indium tin oxide microstrip line feeding layer is 10 - 50 Ω / sq; the light transmittance of the second transparent glass layer > 95%, and the thickness is 1 - 3 mm; the sheet resistance of the substrate indium tin oxide layer is 10 - 50 Ω / sq.

[0009] A further technical solution of the present invention is: the width of the indium tin oxide microstrip line feeding layer is 50 - 500 μm, and its carrier concentration is regulated by voltage to be 10 18 ~10 21 cm -3 , feeding the antenna array of the top photoconductive material layer.

[0010] A further technical solution of the present invention is: the photoconductive material layer is a hydrogenated amorphous silicon a-Si:H thin film with a thickness of 100 nm and a photoconductivity of 10 4 S / cm 2 .

[0011] A further technical solution of the present invention is: the digital light processing module is a DLP projection module, including a light source, an illumination system, a TIR prism, a DMD chip, and a projection objective lens arranged in sequence along the optical path; the DMD chip is a 0.7-inch micromirror array with a resolution of 1024×768, a pixel unit size of 13.89 μm, and supporting a pattern switching speed of ≤20 μs; the light source is a semiconductor laser with a wavelength of 780 nm, a power stability of ±0.5%, and a coherence length > 50 cm.

[0012] A further technical solution of the present invention is that the light source further includes a laser beam expander system and a fly-eye homogenizing system arranged in the output direction of the laser. The beam expansion ratio of the beam expander system is 19 times, and the output beam diameter is 22 mm. The fly-eye homogenizing system is an 8×8 lens array, the aspect ratio of the lens unit is 4:3, and the size is 20 mm×15 mm.

[0013] A further technical solution of the present invention is that the projection objective lens has a focal length of 9 mm, a lateral magnification of 71.4, and the spatial resolution satisfies that the modulation transfer function MTF at the cut-off frequency of 36 lp / mm is MTF≥0.5 in the marginal field of view.

[0014] A further technical solution of the present invention is that the DLP projection module is driven by an FPGA control board, the sampling rate is 1 GHz, the delay is <1 μs, the ±12° deflection control of the micromirror array is realized, and the deflection jitter is <0.1°.

[0015] A further technical solution of the present invention is that the antenna array generates a Yagi antenna or a beamforming array through the DLP projection module, and the measured radiation efficiency is ≥82%.

[0016] A further technical solution of the present invention is that the minimum projection feature size of the antenna array is 7.6 μm, corresponding to the λ / 40 electrical size of the highest operating frequency; the operating bandwidth of the antenna covers >10 octaves.

[0017] Beneficial effects

[0018] The beneficial effects of the present invention are as follows: The present invention first proposes to use the projection method to generate an antenna array whose size and shape can be flexibly changed within a large range. Taking the DLP projection module as a reconfigurable technical means, it can realize the reception, transmission and regulation of ultra-wideband electromagnetic wave signals across multiple octaves.

[0019] Aiming at the problems of limited operating bandwidth, high design complexity and manufacturing cost, and insufficient electromagnetic regulation ability of the existing reconfigurable antenna array technology, according to the optoelectronic properties of materials, using DLP technology and digital micromirror device (DMD) chips, the antenna array is generated on the photoconductive material film by the "projection" method. On the premise of ensuring the regulation speed and efficiency, it provides a feasible solution for realizing an ultra-large octave operating bandwidth, and does not require a large number of electronic component arrangements and complex control network designs, effectively reducing the design difficulty and manufacturing cost. The specific effect analysis is as follows:

[0020] 1. Ultra-wideband communication capability. By dynamically generating a reconfigurable antenna array through DLP technology, with a minimum feature size of 7.6 μm (corresponding to the λ / 40 electrical size at the highest frequency), combined with the fast response of photoconductive materials (switching speed ≤ 20 μs), it realizes a working bandwidth coverage of more than 10 octaves, supports the transceiver of ultra-wideband signals from microwave to terahertz bands, far exceeding the frequency band limitations of traditional antennas.

[0021] 2. High precision and flexible reconfiguration. Using a DMD chip (resolution 1024×768) and sub-micron optical field modulation technology, it can dynamically generate diverse antenna structures such as Yagi antennas and beamforming arrays, flexibly adjust the frequency, radiation pattern, and polarization mode to meet the communication requirements of multiple frequency bands and multiple scenarios.

[0022] 3. Fast response and low power consumption. Based on the millisecond-level (<10 ms) pattern switching speed of DLP projection, it is significantly superior to mechanical or MEMS reconfigurable antennas, and there is no need to frequently switch the circuit, reducing power consumption, and is suitable for real-time communication scenarios.

[0023] 4. Low cost and low complexity. By directly generating the antenna structure through projection, it eliminates complex radio frequency circuits and a large number of electronic components, simplifies the manufacturing process, reduces the design difficulty and preparation cost, and is especially suitable for large-scale array applications.

[0024] 5. High radiation efficiency and stability. Using transparent conductive materials (ITO) and ultra-clear glass (light transmittance > 99%), combined with a polarization correction film (extinction ratio > 10 -6 ), it ensures low loss and anti-interference ability of the optical path. The measured radiation efficiency is ≥ 82%, improving the signal transceiver quality.

[0025] 6. Environmental adaptability. The photoconductive material works at a specific wavelength (760 - 820 nm) to avoid visible light interference. By combining voltage regulation of the carrier concentration of the ITO layer (10 18 ~10 21 cm -3 ), it enhances the stability and reliability of the system in complex electromagnetic environments.

[0026] 7. Technical compatibility and application prospects. Compatible with existing communication systems, suitable for cutting-edge fields such as 6G, the Internet of Things, and terahertz communication, providing efficient and economical solutions for scenarios such as ultra-wideband communication, intelligent radar, and electronic warfare, and having broad industrialization potential. Description of the Drawings

[0027] Figure 1Schematic diagram of the structure of the ultra-large octave antenna based on photoconductive material in the embodiment of the present invention: (a) Schematic diagram of the hierarchical structure of the ultra-large octave antenna array, (b) Projected antenna array structure diagram of the top photoconductive material layer, (c) Top view and cross-sectional view of the ITO microstrip line feeding layer, (d) DLP projection module diagram;

[0028] Figure 2 Schematic diagram of the principle of the DLP projection module based on the DMD chip in the embodiment of the present invention;

[0029] Figure 3 Optical path diagram of the DLP projection module in the embodiment of the present invention;

[0030] Figure 4 Galilean laser beam expander system in the embodiment of the present invention;

[0031] Figure 5 Optical properties of the photoconductive thin film in the embodiment of the present invention.

[0032] Description of reference numerals: 1. DMD chip, 11. Mirror layer, 111. Micro mirror, 12. Arm and hinge layer, 121. Hinge, 122. Arm, 13. Metal layer, 131. Micro mirror addressing electrode, 132. Arm addressing electrode, 133. Bias reset bus, 14. Storage cell layer; 2. 780nm laser, 3. Shaping and homogenizing illumination lens group, 4. TIR prism, 5. Projection objective lens group, 6. Organic photoconductor thin film electromagnetic surface, 61. Photoconductive material, 62. First light-transmitting glass layer, 63. Indium tin oxide microstrip line feeding layer, 64. Second light-transmitting glass layer, 65. Substrate indium tin oxide layer. Detailed implementation manners

[0033] The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0034] Aiming at the problems of limited working bandwidth, high design complexity, high manufacturing cost, and insufficient electromagnetic regulation ability in the existing reconfigurable antenna array technology, the present invention proposes an ultra-wide octave antenna based on organic photoconductive materials. For the first time, the photoconductive materials are applied to the reconfigurable antenna array. According to the optoelectronic characteristics of the materials, using the DLP technology and the digital micromirror device (DMD) chip, the antenna array is generated on the organic photoconductive material film by means of "projection". On the premise of ensuring the regulation speed and efficiency, a feasible solution is provided for achieving an ultra-wide octave working bandwidth, and there is no need for a large number of electronic component arrangements and complex control network designs, effectively reducing the design difficulty and manufacturing cost. As the core hardware basis for the implementation of the present invention, under the condition of light illumination at a specific wavelength (visible light band), the organic photoconductive material can be converted from the dielectric state to the conductor state, while the unilluminated area still presents the dielectric state. Using this characteristic and combining with the DLP technology, light at a specific wavelength can form "images" of antenna arrays with different sizes and shapes on the organic photoconductive material film. Since the size and shape of the projected antenna array can be flexibly changed within a large range, the transceiver of ultra-wideband electromagnetic waves across multiple octaves can be realized. By controlling the size, shape, and illumination intensity of the projection, multi-dimensional and efficient reception, transmission, and regulation of electromagnetic wave signals can be achieved. This design has great feasibility and other potential application values in wireless communication systems and other reconfigurable designs.

[0035] The ultra-wide octave antenna based on organic photoconductive materials of the present invention includes an organic photoconductor thin film electromagnetic surface and a digital light processing module capable of projecting different patterns on its surface. The conductivity distribution of the organic photoconductor thin film electromagnetic surface can be changed by light control. The digital light processing module can dynamically adjust the size and shape of the pattern projected on the organic photoconductor thin film electromagnetic surface to generate a reconfigurable antenna array, realizing the transceiver of ultra-wideband electromagnetic wave signals across multiple octaves. The organic photoconductor thin film electromagnetic surface sequentially includes a photoconductive material layer, a first transparent glass layer, an indium tin oxide microstrip line feeding layer, a second transparent glass layer, and a substrate indium tin oxide layer according to the lamination sequence.

[0036] By innovatively integrating the light control characteristics of photoconductive materials with the DLP projection technology, the problems of narrow bandwidth, slow response, and high cost of traditional reconfigurable antennas are solved, and it has the advantages of ultra-wideband, high precision, and low cost, opening up a new path for the performance improvement and diversified applications of future wireless communication systems.

[0037] The above technical solutions will be further described below in conjunction with the drawings and examples:

[0038] In one embodiment, referring to Figure 1As shown in the figure, the ultra-wide octave antenna based on photoconductive materials in this embodiment includes an organic photoconductor thin-film electromagnetic surface 6 and a DLP projection module. The organic photoconductor thin-film electromagnetic surface 6 sequentially includes a photoconductive material layer 61 (with a thickness of 50 - 200 nm) from top to bottom, a first light-transmitting glass layer 62 (with a light transmittance > 95% and a thickness of 1 - 3 mm), an indium tin oxide (ITO) microstrip line feeding layer 63 (with a sheet resistance of 10 - 50 Ω / sq), a second light-transmitting glass layer 64 (with a light transmittance > 95% and a thickness of 1 - 3 mm), and a substrate ITO layer 65 (with a sheet resistance of 10 - 50 Ω / sq).

[0039] The photoconductive material layer 61 at the top is the projection layer of the present invention. That is, after the DLP projection module receives the "projection pattern", the projected light passes through the ITO layer 62, the second light-transmitting glass layer 64, the indium tin oxide (ITO) microstrip line feeding layer 63, and the first light-transmitting glass layer 62 to form the required reconfigurable antenna array on the top layer.

[0040] Preferably, the thickness of the photoconductive material layer of the organic photoconductor thin-film electromagnetic surface is 50 - 200 nm; the light transmittance of the first light-transmitting glass layer > 95% and the thickness is 1 - 3 mm; the sheet resistance of the indium tin oxide microstrip line feeding layer is 10 - 50 Ω / sq; the light transmittance of the second light-transmitting glass layer > 95% and the thickness is 1 - 3 mm; the sheet resistance of the substrate indium tin oxide layer is 10 - 50 Ω / sq.

[0041] Preferably, the width of the indium tin oxide microstrip line feeding layer is 50 - 500 μm, and its carrier concentration is regulated by voltage to be 10 18 ~10 21 cm -3 to feed the antenna array of the top photoconductive material layer.

[0042] Preferably, the photoconductive material layer is a hydrogenated amorphous silicon a-Si:H thin film with a thickness of 100 nm and a conductivity of 10 4 S / cm 2 .

[0043] The indium tin oxide (ITO) is one of the most concerned materials among transparent metal oxides. It has good electrical conductivity and its carrier density exceeds that of conventional semiconductors by several orders of magnitude. The conductivity and dielectric constant of the ITO layer are both related to the carrier concentration. The carrier concentration of the ITO layer can be adjusted by voltage, and thus the equivalent dielectric constant of the ITO layer can be adjusted. Therefore, ITO can be used to fabricate a reconfigurable metasurface. Using this property, the carrier concentration of the ITO layer can be regulated by voltage to feed the antenna array projected on the top layer. Moreover, indium tin oxide is a transparent metal oxide, and as the feeding layer and the substrate layer material, it does not block the projection light emitted by the lower DLP projection module.

[0044] In addition, the use of the transparent glass layer does not affect the light projection of the bottom DLP projection module and the formation of the antenna array in the top photoconductive material layer. As the dynamic reconfiguration engine of the antenna array, the DLP projection module realizes the following functions through high-precision light field modulation: 1) Pattern projection: project the preset antenna array patterns (such as Yagi antennas, beamforming arrays) onto the photoconductive material layer with sub-micron accuracy; 2) Real-time control: achieve a millisecond-level response speed (<10 ms) through refresh rate control; 3) Parametric regulation: dynamically adjust the light field intensity / phase distribution to match the working requirements of different frequency bands.

[0045] The photoconductive material layer uses a special optoelectronic material, whose conductivity changes significantly when irradiated with light of a specific wavelength (visible light band), and can be converted from a dielectric state to a conductive state, while the unirradiated area remains in the dielectric state. Specifically, when the material is irradiated with light, electron-hole pairs are generated inside. These photo-generated charges migrate to different electrodes under the action of an electric field, resulting in a change in the conductivity of the material. The conductivity of the irradiated part increases, while the conductivity of the unirradiated part remains unchanged.

[0046] In the application of the antenna array, this change in conductivity can be used to dynamically adjust the characteristics of the antenna array. By precisely controlling the light spot projected onto the organic photoconductor material, the conductivity of specific parts of the array can be selectively changed, thereby realizing the reconfiguration of the radiation characteristics of the antenna array. This reconfiguration can achieve changes in parameters such as frequency, radiation pattern, and polarization to meet different communication and other requirements.

[0047] In one embodiment, referring to Figure 2 As shown, the reconfiguration means used in this embodiment is the DLP technology based on the DMD chip 1. The top layer of the DMD chip 1 structure is the mirror layer 11 composed of a micro-mirror 111 array, the middle layer is the arm and hinge layer 12 composed of the hinge 121 and the arm 122, the metal layer 13 is composed of the micro-mirror addressing electrode 131, the arm addressing electrode 132, and the bias reset bus 133, and the bottom layer is the COMS SRAM storage unit layer 14. The DMD chip integrates three technologies: optics, mechanics, and electronic circuits. The electronic circuit technology is responsible for the system's circuit, the mechanical technology is responsible for the flipping movement of the micro-mirror unit, and the optical technology refers to the modulation of light by the micro-mirror.

[0048] In one embodiment, referring to Figure 3As shown in the figure, the DLP projection system includes a DMD chip 1, a 780nm laser 2, an illumination lens group 3 for shaping and homogenizing the light field, a TIR prism 4, and a projection objective lens group 5. The laser emitted by the 780nm laser passes through the shaping and homogenizing lens group and enters the TIR prism. Total internal reflection occurs on the total internal reflection surface of the TIR prism and is incident on the surface of the DMD. After being modulated by the micromirror, the light beam enters the TIR prism again and finally forms the required antenna array on the photoconductive material film through the projection objective lens.

[0049] Preferably, the technical specifications of the DMD chip are a 0.7-inch DMD chip of the DLP 700 model (1024×768 resolution), which generates a high-precision grating pattern and supports synchronous control of a maximum 16×16 array; the laser light source uses a semiconductor laser with a wavelength of 780nm (power stability ±0.5%, coherence length > 50cm), which provides a monochromatic light field and matches the best response wavelength of the photoconductive material; the optical module includes a gamma correction lens group and a polarization correction film (extinction ratio < 10 -6 ), which optimizes the light field modulation quality and eliminates ambient light interference; the drive control uses a self-developed FPGA control board (sampling rate 1GHz, delay < 1μs) to achieve real-time deflection control of the micromirror array (deflection accuracy ±12°, jitter < 0.1°)

[0050] Specifically, the design process of the DLP projection module is as follows:

[0051] From the parameters of the DMD chip 1, it can be calculated that the diagonal length of the DMD is 17.78mm, and the spot diameter of the laser is 1.2mm. In order to make the illumination light beam completely cover the display chip, an expansion system needs to be added behind the light source, and the expansion ratio is 15 times. Considering that the laser beam is evenly distributed within the DMD display area, the expansion ratio of the expansion system of the present invention is comprehensively considered to be 19 times.

[0052] 1) Design of the laser beam expansion system:

[0053] Considering the overall size of the system, the expansion system adopts a Galilean structure as Figure 4 shown. An input negative lens and an output positive lens form a virtual confocal structure. The input negative lens diverges the light emitted from the virtual focus and transmits it to the output positive lens.

[0054] After the approximately parallel laser beam passes through the input mirror, the new beam waist ω′0 and divergence angle θ' are

[0055]

[0056] In the formula, l is the distance between the incident laser beam waist ω'0 and the incident mirror, f1 is the focal length of the input mirror, and the radius of the laser beam on the input mirror is calculated by the formula

[0057]

[0058] ω'0 falls on the rear focal plane of the output mirror. The focal length f2 of the output mirror is greater than the focal length of the input mirror. The laser beam will be collimated by the beam expander, and the collimation magnification is

[0059]

[0060] where T = f2 / f1 and θ is the divergence angle of the incident laser beam. After passing through the output mirror, the new beam waist ω″0 and divergence angle θ″ are

[0061]

[0062] Thus, ω″0 = T1ω(l).

[0063] The laser beam expander is designed using Zemax software. From the laser parameters, it is known that the system uses a wavelength of 780 nm, the input beam diameter is 1.2 mm, the output beam diameter is 22 mm, a Galilean structure is used for the design, the distance between the two lenses is 60 mm, the entrance pupil diameter is set to 1.2 mm. From the Cardinal Point Data function of Zemax software, it can be seen that the focal length of the first input lens is f1 = -3.1 mm, and the focal length of the second output lens is f1 = 3.1 mm. Therefore, the magnification of the designed laser beam expander T1 = 56.8 / 3.1 = 18.33.

[0064] Assume the laser beam expander is placed 10 mm behind the laser, then Therefore, ω″0 = 18.33×1.2 = 21.9 mm, which is greater than the diagonal length of the DMD chip, meeting the design requirements.

[0065] 2) Design of the fly-eye homogenizing system

[0066] The fly-eye homogenizing system can not only provide uniform illumination for the DMD chip, but also modulate the circular illumination spot of the light source and convert it into a rectangular spot for output. Therefore, the aspect ratio of the fly-eye lens unit should be the same as that of the DMD chip, which is 4:3. The size of the 0.7-inch DMD chip selected for this system is 14.22 mm×10.67 mm, and the aperture of the laser beam after passing through the beam expander system is 21.9 mm. Considering that the illumination beam can fully illuminate the DMD, the size of the fly-eye lens is set to 20 mm×15 mm. From the principle of the fly-eye lens, the more the number of fly-eye lens units, the better the homogenizing effect. However, when the number of lens units reaches a certain level, the improvement of the homogenizing effect is not obvious, and the increase in the number results in very small lens unit sizes, which are not easy to process and manufacture, and the overall cost performance decreases. Considering the above factors comprehensively, the present invention uses an 8×8 fly-eye lens array. From the aspect ratio of the lens unit, the length of the lens unit is 2.5 mm and the width is 1.88 mm.

[0067] 3) Analysis of Projection Objective Parameters

[0068] Based on the size of the DMD chip, the main technical specifications of the projection objective of the present invention are as follows:

[0069] a. Working Wavelength Band:

[0070] Since the present invention uses a 780 nm laser as the light source, the working wavelength band of the objective is about 780 nm.

[0071] b. Field of View and F / #:

[0072] To reduce the overall size of the system, the field of view of the projection objective is usually between 60° and 80°. In the present invention, the full field angle 2ω = 70° is selected, and the F / # of the projection objective is 2.4.

[0073] c. Transverse Magnification and Focal Length of the Lens:

[0074] The transverse magnification of the projection objective is the ratio of the size of the projection screen to the size of the projection chip, that is

[0075]

[0076] According to the actual application environment of the projection system of the present invention, when the projection distance is 0.25 M, the size of the projection screen is set to 20 inches (50 cm × 50 cm). Since a 0.7-inch DMD chip is selected for this system, the transverse magnification β = 20 / 0.7 = 29. The focal length calculation formula is

[0077]

[0078] In the formula, L is the conjugate distance between the object and the image, and l' is the image distance. Substituting l' = 0.25 M and β = 29 into the above formula, f ≈ 9 mm can be obtained.

[0079] 4) Spatial Resolution of the Projection Objective

[0080] The spatial resolution of the projection objective must be greater than the resolution of the DMD chip for the system to project a clear image. The size of the DMD chip is 0.7 inches, and the pixel unit size is 13.89 μm × 13.89 μm. From this, the cut-off frequency of the modulation transfer function MTF of the projection objective can be determined to be at least:

[0081]

[0082] That is, when the spatial resolution of the projection objective is equal to or greater than this value, it meets the design standard. Combining with the general design standard of the projection objective, at the cut-off frequency, MTF ≥ 0.5 for the edge field of view and MTF ≥ 0.6 for the central field of view.

[0083] 5) Determination of the initial structure of the projection objective lens:

[0084] Since it is relatively complex and computationally intensive to determine the initial structure of an optical system by using the PW method to solve the initial structure parameters, the initial structure of the projection objective lens in this system is found from existing structures with similar technical indicators in patents, literature and other materials. Based on the main technical indicators of the projection objective lens and the analysis of the telecentric optical path, a telecentric projection objective lens structure with similar performance parameters is selected: the full field angle 2ω = 78°, the relative aperture 1 / 2.5, and the effective focal length 12.7 mm.

[0085] The initial structure is optimized by using Zemax software. The initial structure parameters are input into the software, and the corresponding data are modified: the image-side F / # is 2.4, the semi-field angle is 35°, three fields of view of 0, 0.7, and 1 are selected, and the wavelength is selected as 780 nm. According to the parameters of the projection objective lens, the number of lenses and the lens surface types of the initial structure are optimized. Appropriately adding aspherical surfaces in the system can effectively correct spherical aberration and improve the structure of the system.

[0086] In one embodiment, the implementation process of an ultra-large octave antenna based on an organic photoconductive material is as follows:

[0087] 1) Prepare the substrate: Clean and deposit the base ITO layer (sheet resistance 15 Ω / sq);

[0088] 2) Coat the photoconductive material: Spin-coat the a-Si:H thin film (thickness 100 nm, conductivity 10 4 S / cm 2 );

[0089] 3) Construct the intermediate layer: Stack the transparent glass layer (1.5 mm) and the ITO microstrip line feeding layer (50 μm wide) in sequence;

[0090] 4) DLP projection module setting;

[0091] 5) Antenna reconstruction: Input a preset pattern (such as a Yagi antenna array with a frequency of 5 GHz), project it onto the photoconductive material layer through the DLP projection module, and the measured radiation efficiency reaches 82% after feeding through the microstrip line.

[0092] In summary, we propose an ultra-wide octave antenna based on organic photoconductive materials. After converting the required antenna array image into a digital signal, it is input into the DLP projection system. Inside the system, light is emitted through processes such as illumination, total reflection, and projection. After passing through the ITO substrate layer, it successively enters the transparent glass layer 1, the ITO feeding layer, and the transparent glass layer 2, and finally irradiates on the top photoconductive material layer to form an antenna array. The reconfigurable technology used in the present invention can quickly and timely perform array transformation to meet different communication requirements, etc. And this projection method also makes the present invention have a high reuse rate. Using ITO as the microstrip line material not only meets the requirement of feeding the antenna array but also can transmit the projection light as much as possible. The uniqueness of this structure lies in that it obtains a switchable antenna array structure and a super-wideband electromagnetic wave signal that can be transmitted and received through projection technology. This ultra-wide octave antenna based on photoconductive materials provides a new technical means for realizing ultra-wideband communication coverage, etc.

[0093] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. An ultra-large octave band antenna based on organic photoconductive materials, characterized in that: It includes an organic photoconductor film electromagnetic surface and a digital light processing module capable of projecting different patterns on the surface, wherein the organic photoconductor film electromagnetic surface can change the conductivity distribution through light control, and the digital light processing module can dynamically adjust the size and shape of the pattern projected on the organic photoconductor film electromagnetic surface to generate a reconfigurable antenna array to realize the transmission and reception of ultra-wideband electromagnetic wave signals across multiple octaves; The electromagnetic surface of the organic photoconductor film comprises, in a lamination order, a photoconductive material layer, a first light-transmitting glass layer, an indium tin oxide microstrip line feeding layer, a second light-transmitting glass layer, and a base indium tin oxide layer.

2. The ultra-large octave band antenna based on organic photoconductive material according to claim 1, characterized in that: The thickness of the photoconductive material layer on the electromagnetic surface of the organic photoconductor film is 50 to 200 nm; the transmittance of the first light-transmitting glass layer is greater than 95%, and the thickness is 1 to 3 mm; the square resistance of the indium tin oxide microstrip line feeding layer is 10 to 50 Ω / sq; the transmittance of the second light-transmitting glass layer is greater than 95%, and the thickness is 1 to 3 mm; the square resistance of the base indium tin oxide layer is 10 to 50 Ω / sq.

3. The ultra-large octave band antenna based on organic photoconductive material according to claim 2, characterized in that: The width of the indium tin oxide microstrip line feeding layer is 50 to 500 μm, and its carrier concentration is 10 18 ~10 21 cm -3 , feeding the antenna array of the top photoconductive material layer.

4. The ultra-large octave band antenna based on organic photoconductive material according to claim 3, characterized in that: The photoconductive material layer is a hydrogenated amorphous silicon a-Si:H film with a thickness of 100nm and a photoconductivity of 104S / cm 2 .

5. The ultra-large octave band antenna based on organic photoconductive material according to claim 1, characterized in that: The digital light processing module is a DLP projection module, including a light source, an illumination system, a TIR prism, a DMD chip and a projection objective lens arranged in sequence along the optical path; the DMD chip is a 0.7-inch micromirror array with a resolution of 1024×768, a pixel unit size of 13.89 μm, and supports a pattern switching speed of ≤20 μs; the light source is a 780nm wavelength semiconductor laser with a power stability of ±0.5% and a coherence length of >50 cm.

6. The ultra-large octave band antenna based on organic photoconductive material according to claim 5, characterized in that: The light source also includes a laser beam expansion system and a compound eye homogenization system arranged in the laser emission direction. The beam expansion system has a beam expansion ratio of 19 times and an output beam diameter of 22 mm. The compound eye homogenization system is an 8×8 lens array with a lens unit aspect ratio of 4:3 and a size of 20 mm×15 mm.

7. The ultra-large octave band antenna based on organic photoconductive material according to claim 6, characterized in that: The projection objective lens has a focal length of 9 mm, a vertical axis magnification of 71.4, and a spatial resolution that satisfies the MTF of the edge field of view MTF≥0.5 when the cutoff frequency is 36 lp / mm.

8. The ultra-large octave band antenna based on organic photoconductive material according to claim 7, characterized in that: The DLP projection module is driven by an FPGA control board with a sampling rate of 1 GHz and a delay of <1 μs, achieving ±12° deflection control of the micromirror array and a deflection jitter of <0.1°.

9. The ultra-large octave band antenna based on organic photoconductive material according to claim 1, characterized in that: The antenna array generates a Yagi antenna or a beamforming array through a DLP projection module, and the measured radiation efficiency is ≥82%.

10. The ultra-large octave band antenna based on organic photoconductive material according to claim 1, characterized in that: The minimum projected characteristic size of the antenna array is 7.6 μm, corresponding to the λ / 40 electrical size of the highest operating frequency; the operating bandwidth of the antenna covers more than 10 times the frequency range.

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