Multi-channel vlc system based on cmos process

Abstract

The application discloses a multi-channel VLC system based on a CMOS process, comprising a transmitting module and a receiving module; the transmitting module comprises a vertical polarization transmitting submodule and a horizontal polarization transmitting submodule; the receiving module comprises a vertical polarization receiving submodule and a horizontal polarization receiving submodule; the vertical polarization transmitting submodule emits three routes of non-polarized light emitted by a first RGB-LED after vertical polarization dispersion, parallel conversion and emission, and the vertical polarization receiving submodule forms three routes of analog electric signals after filtering of the received multicolor visible light signals by a metasurface; the horizontal polarization transmitting submodule emits three routes of non-polarized light emitted by a second RGB-LED after horizontal polarization dispersion, parallel conversion and emission, and the horizontal polarization receiving submodule converts the received multicolor visible light signals into three routes of analog electric signals after filtering by a metasurface; and six routes of analog electric signals are converted into one route of digital electric signal output. The application can realize clear and complete multi-channel high-speed communication.

Description

Technical Field

[0001] This invention relates to the field of visible light communication technology, and in particular to a multi-channel VLC system based on CMOS technology. Background Technology

[0002] With the explosive growth in the number of mobile user terminals, traditional radio frequency communication is gradually becoming unable to handle the ever-increasing mobile data traffic. Against this backdrop, Visible Light Communication (VLC) has emerged. Compared with conventional wireless communication technologies, VLC not only combines illumination and high-speed communication functions, but also boasts significant advantages such as abundant spectrum resources, large system capacity, strong security, and no electromagnetic interference. This makes it a promising candidate for applications in electromagnetically sensitive areas, high-security communication scenarios, intelligent transportation, and underwater high-speed communication.

[0003] Traditional VLC systems typically use printed circuit boards (PCBs) and commercial discrete components (i.e., board-level structures) to build VLC transceiver systems. This design results in VLC systems that are bulky, consume a lot of power, and are expensive to deploy. Compared to board-level structures, integrated chips have advantages such as high speed, high reliability, small size, light weight, and low cost. Therefore, adopting a chip integration design helps to further optimize the performance of VLC systems.

[0004] Publicly available VLC systems typically use monochromatic LEDs (blue LEDs with yellow phosphors) as the light source, thus having only one communication channel. This severely limits the communication efficiency and application scenarios of VLC systems. In contrast, multicolor VLC systems use multicolor chip-integrated LEDs (such as red, green, and blue LEDs) as the light source. Each color can carry different data streams simultaneously, enabling wavelength division multiplexing (WDM) and effectively increasing the number of communication channels and data transmission rates. However, due to the wide spectrum and large divergence angle of multicolor LEDs, spectral overlap is prone to occur during communication. Therefore, channel separation is required before the receiver in a multicolor VLC system to prevent signal crosstalk. Two common methods for channel separation are: one is to place numerous filters in front of the photodetector (PD) at the receiver, but this increases the system's size, making integration and miniaturization difficult; the other is to use an image sensor as the light receiving chip, but image sensors are typically made of organic materials, resulting in higher costs and unstable chemical compositions, thus affecting system performance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and defects of the prior art and provide a multi-channel VLC system based on CMOS technology. It is implemented based on polarization diversity and wavelength division multiplexing technology. It not only has multiple communication channels, but also integrates the multi-color visible light modulation driver chip and the multi-color visible light metasurface light receiver chip on a single chip using CMOS technology. Clear and complete multi-channel high-speed communication can be achieved without increasing the system size. It solves the problem of low communication efficiency caused by the use of monochromatic LED light source in traditional VLC system and the signal crosstalk problem caused by spectral overlap in multi-color VLC system. At the same time, it reduces power consumption and cost by reducing the system size.

[0006] A multi-channel VLC system based on CMOS technology includes a transmitting module and a receiving module. The transmitting module includes a vertically polarized transmitting submodule and a horizontally polarized transmitting submodule. The receiving module includes a vertically polarized receiving submodule and a horizontally polarized receiving submodule. The vertically polarized transmitting submodule is used to convert three unpolarized lights emitted by a first RGB-LED according to three driving signals VIN1-VIN3 into divergent vertically polarized lights, and then into three parallel lights for emission. The vertically polarized receiving submodule is used to receive the three parallel lights emitted by the vertically polarized transmitting submodule, convert them into three convergent vertically polarized lights, and then, after being filtered by a metasurface, photoelectrically convert them into three analog electrical signals. The horizontally polarized transmitting submodule is used to convert three unpolarized lights emitted by a second RGB-LED according to three driving signals VIN4-VIN6 into divergent horizontally polarized lights, and then into three parallel lights for emission. The horizontally polarized receiving submodule is used to receive the three parallel lights emitted by the horizontally polarized transmitting submodule, convert them into three convergent horizontally polarized lights, and then, after being filtered by a metasurface, photoelectrically convert them into three analog electrical signals. The six analog electrical signals are then converted from analog to digital signals for output.

[0007] Preferably, the vertical polarization emission submodule includes a first multicolor visible light modulation driver chip, a first vertical polarizer, and a first convex lens. The first multicolor visible light modulation driver chip is connected to the first RGB-LED, and the first vertical polarizer and the first convex lens are located sequentially on the light-emitting side of the first RGB-LED. The horizontal polarization emission submodule includes a second multi-color visible light modulation driver chip, a first horizontal polarizer, and a second convex lens. The second multi-color visible light modulation driver chip is connected to the second RGB-LED, and the first horizontal polarizer and the second convex lens are located sequentially on the light-emitting side of the second RGB-LED.

[0008] Preferably, the first multi-color visible light modulation driver chip and the second multi-color visible light modulation driver chip are implemented based on CMOS technology, each including three signal transmitting sub-circuits, and the output terminals of the three signal transmitting sub-circuits are each connected to an LED, namely a red LED, a green LED and a blue LED.

[0009] Preferably, the signal transmitting sub-circuit includes a two-stage pre-emphasis circuit, a modulation driving circuit, and a carrier extraction circuit. The input terminal of the pre-emphasis circuit is connected to the LED driving signal, and the output terminal of the pre-emphasis circuit is connected to the input terminal of the modulation driving circuit. The output terminal of the modulation driving circuit is connected to the input terminal of the carrier extraction circuit. The output terminal of the carrier extraction circuit is connected to an LED pre-emphasis circuit to pre-boost the high-frequency components of the input signal. The modulation driving circuit modulates the output signal of the pre-emphasis circuit and then amplifies it to drive the LEDs in the RGB-LED to emit red, blue, and green light. The carrier extraction circuit discharges the remaining carriers according to the control signal of the modulation driving circuit, so that the LEDs of the RGB-LED are turned off.

[0010] Preferably, the vertical polarization receiving submodule includes a third convex lens, a second vertical polarizer, and a first multicolor visible light metasurface light receiver chip; the third convex lens focuses the parallel light transmitted from the vertical polarization transmitting submodule, the second vertical polarizer only allows vertically polarized light in the focused light signal to pass through, and the first multicolor visible light metasurface light receiver chip receives the vertically polarized light and outputs an analog electrical signal to the analog-to-digital converter to form a digital electrical signal output; The horizontal polarization receiving submodule includes a fourth convex lens, a second horizontal polarizer, and a second multicolor visible light metasurface light receiver chip. The fourth convex lens focuses the parallel light transmitted from the horizontal polarization transmitting submodule. The second horizontal polarizer only allows horizontally polarized light in the focused light signal to pass through. After receiving the horizontally polarized light, the second multicolor visible light metasurface light receiver chip outputs an analog electrical signal to an analog-to-digital converter to form a digital electrical signal output.

[0011] Preferably, the first multicolor visible light metasurface light receiver chip and the second multicolor visible light metasurface light receiver chip have the same structure, each including three receiver sub-circuits, and the front end of each receiver sub-circuit is connected to a fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating.

[0012] Preferably, the fully integrated multicolor visible light photodetector connected to the front end of the three receiving sub-circuits is a red light photodetector, a blue light photodetector, and a green light photodetector, which are used to detect red light, blue light, and green light signals, respectively.

[0013] Preferably, the receiving sub-circuit, from the optical signal input terminal to the digital electrical signal output terminal, is composed of a fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating, a transimpedance preamplifier, a limiting amplifier, an equalizer, and an output buffer stage connected in sequence. The output terminal of the output buffer stage is connected to the input terminal of the analog-to-digital converter. Specifically, the transimpedance preamplifier converts the output current signal of the fully integrated multicolor visible light photodetector into a voltage signal; the limiting amplifier amplifies the voltage signal output by the transimpedance preamplifier to a preset digital voltage level; the equalizer compensates for the frequency response characteristics of the limiting amplifier's output signal, outputting a differential voltage signal at the preset digital voltage level; and the output buffer stage converts the differential voltage signal output by the equalizer into a single-ended voltage signal.

[0014] Preferably, the fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating selectively responds to the signal of vertically or horizontally polarized light of the incident preset wavelength band according to the grating width and grating period parameters of the subwavelength grating, and blocks light signals of non-preset wavelength bands, thereby achieving selective response to red, blue or green light signals.

[0015] Preferably, the fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating is a silicon-based P-type substrate detector fabricated using CMOS technology.

[0016] The multi-channel VLC system based on CMOS technology of the present invention is compatible with standard CMOS technology. Without increasing the system size and cost, it achieves clear and complete high-speed communication through multiple communication channels. It effectively solves the problem of low communication efficiency caused by the use of monochromatic LED light source in traditional VLC system, as well as the signal crosstalk problem caused by spectral overlap in multicolor VLC system. It comprehensively improves communication quality and efficiency, and reduces power consumption and cost. Attached Figure Description

[0017] Figure 1 This is a block diagram of the overall system structure of the CMOS multi-channel VLC system of the present invention.

[0018] Figure 2 This is a schematic diagram of the circuit structure of the first multi-color visible light modulation driver chip based on a CMOS multi-channel VLC system according to the present invention.

[0019] Figure 3 This is a signal processing block diagram of the transmitter module of the CMOS multi-channel VLC system of the present invention.

[0020] Figure 4 This is a schematic diagram of the circuit structure of the first multicolor visible light metasurface optical receiver chip based on a CMOS multichannel VLC system according to the present invention.

[0021] Figure 5 This is a signal processing block diagram of the receiving module of the CMOS multi-channel VLC system of the present invention.

[0022] Figure 6 This is a top view of the structure of the blue light photodetector / green light photodetector of the fully integrated multicolor visible light photodetector of the present invention.

[0023] Figure 7 This is a cross-sectional view of the structure of the blue light photodetector / green light photodetector of the present invention.

[0024] Figure 8 This is a top view of the structure of the red light photodetector of the fully integrated multicolor visible light photodetector of the present invention.

[0025] Figure 9 This is a cross-sectional view of the red light photodetector of the present invention.

[0026] Explanation of reference numerals in the attached figures: 1. Transmission module; 11. First multi-color visible light modulation driver chip; 111. First pre-emphasis circuit; 112. First modulation driver circuit; 113. First carrier extraction circuit; 114. Second pre-emphasis circuit; 115. Second modulation driver circuit; 116. Second carrier extraction circuit; 117. Third pre-emphasis circuit; 118. Third modulation driver circuit; 119. Third carrier extraction circuit; 101. First transmitter sub-circuit; 102. Second transmitter sub-circuit; 103. Third transmitter sub-circuit; 12. Second multi-color visible light modulation driver chip; 13. First RGB-LED; 131. Red LED; 132. Green LED; 133. Blue LED; 14. Second RGB-LED; 15. First vertical polarizer; 16. First horizontal polarizer; 17. First convex lens; 18. Second convex lens; 2. Receiving module; 21. Third convex lens; 22. Fourth convex lens; 23. Second vertical polarizer; 24. Second horizontal polarizer; 25. First multicolor visible light metasurface light receiver chip; 2501, First receiving sub-circuit; 2502, Second receiving sub-circuit; 2503, Third receiving sub-circuit; 251. The first fully integrated multicolor visible light photodetector; 25101, Red photodetector; 25102, Green photodetector; 25103, Blue photodetector; 252. First transimpedance preamplifier; 253. First limiting amplifier; 254. First equalizer; 255. First output buffer stage; 256. Second transimpedance preamplifier; 257. Second limiting amplifier; 258. Second equalizer; 259. Second output buffer stage; 2510. Third transimpedance preamplifier; 2511. Third limiting amplifier; 2512. Third equalizer; 2513. Third output buffer stage; 26. Second multicolor visible light metasurface light receiver chip; 27. Analog-to-digital converter; 3. Subsequent circuitry; 4. P-type substrate; 41. External electrode of the active region of the P-type substrate; 42. External cathode wire of the blue / green photodetector; 43. External anode wire of the blue / green photodetector; 44. First periodic grating; 45. Anode contact hole of the blue / green photodetector; 46. Cathode contact hole of the blue / green photodetector; 47. Deep N-well region; 48. P-well region; 49. First shallow trench isolation layer; 10. Active region external to P-type substrate; 420. Active region external to deep N-well region; 430. Active region external to P-well region; 50. External lead wire for cathode of red photodetector; 51. External lead wire for anode of red photodetector; 52. Second periodic grating; 53. N-well region; 54. Cathode contact hole of red photodetector; 55. Second shallow trench isolation layer; 56. Active region external to N-well region; 57. Third shallow trench isolation layer; 58. Active region external to second P-substrate. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] See Figures 1 to 9 As shown in the exemplary embodiment of this application, the multi-channel VLC system based on CMOS technology is designed based on standard CMOS technology and includes a transmitting module 1 and a receiving module 2. The transmitting module 1 and the receiving module 2 are based on polarization diversity technology and each has two communication channels. Specifically, the transmitting module 1 has a vertical polarization transmitting submodule and a horizontal polarization transmitting submodule; the receiving module 2 has a vertical polarization receiving submodule and a horizontal polarization receiving submodule. The vertical polarization receiving submodule and the horizontal polarization receiving submodule in the receiving module 2 correspond to the vertical polarization transmitting submodule and the horizontal polarization transmitting submodule in the transmitting module 1, respectively. That is, the transmitted signal from the vertical polarization transmitting submodule is received by the vertical polarization receiving submodule, and the transmitted signal from the horizontal polarization transmitting submodule is received by the horizontal polarization receiving submodule.

[0029] In one embodiment, the vertical polarization emitting submodule is used to convert unpolarized light emitted by an RGB-LED into divergent vertical polarized light, and to convert the divergent vertical polarized light into parallel light for outward emission. The vertical polarization receiving submodule is used to receive the parallel light signal emitted by the vertical polarization emitting submodule, converge it, and after polarization processing, allow only vertical polarized light to pass through. Then, the converged vertical polarized light signal is filtered by a metasurface and converted into an analog electrical signal. The analog electrical signal is then converted into a digital electrical signal for output.

[0030] In one embodiment, the horizontal polarization emitting submodule is used to convert the unpolarized light emitted by another RGB-LED into divergent horizontal polarized light, and then convert the divergent horizontal polarized light signal into parallel light for outward transmission. Correspondingly, the horizontal polarization receiving submodule is used to receive the parallel light signal emitted by the horizontal polarization emitting submodule, converge it, and after polarization processing, allow only the horizontal polarized light signal to pass through. Then, the converged horizontal polarized light is filtered by metasurface and converted into an analog electrical signal. The analog electrical signal is then converted into a digital electrical signal for output.

[0031] In an optional embodiment, the vertical polarization emission submodule includes a first RGB-LED 13, a first vertical polarizer 15 that converts the unpolarized light emitted by the first RGB-LED 13 into divergent vertically polarized light, and a first convex lens 17 that converts the divergent vertically polarized light signal into parallel light for transmission.

[0032] In a preferred embodiment, the vertical polarization emission submodule further includes a first multi-color visible light modulation driver chip 11 responsible for modulating and driving the first RGB-LED 13, connected to the first RGB-LED 13, with its input terminal connected to different electrical signals VIN, such as VIN1-VIN3, to modulate and drive the three-color LEDs in the first RGB-LED 13 to emit visible light signals (RGB signals), such as red light, blue light and green light.

[0033] In an optional embodiment, the horizontally polarized emission submodule includes a second RGB-LED 14, a first horizontal polarizer 16, and a second convex lens 18. The first horizontal polarizer 16 is used to convert the unpolarized light emitted by the second RGB-LED 14 into divergent horizontally polarized light, and the second convex lens 18 is used to convert the divergent horizontally polarized light signal emitted by the second RGB-LED 14 and converted by the first horizontal polarizer 16 into parallel light for transmission.

[0034] In a further embodiment, the horizontal polarization emission submodule further includes a second multi-color visible light modulation driver chip 12 responsible for modulating and driving the second RGB-LED 14, connected to the second RGB-LED 14, with its input terminal connected to electrical signals VIN, such as VIN4-VIN6, respectively modulating and driving the three-color LEDs in the second RGB-LED 14 to emit visible light signals (RGB signals), such as red light, blue light and green light.

[0035] In one embodiment, such as Figure 2 As shown, the first multi-color visible light modulation driver chip 11 includes three signal transmitting sub-circuits, namely a first transmitting sub-circuit 101, a second transmitting sub-circuit 102, and a third transmitting sub-circuit 103. For example, the first, second, and third transmitting sub-circuits all adopt the same circuit structure, and the output terminals of each of the three transmitting sub-circuits are connected to an LED, namely a red LED 131, a green LED 132, and a blue LED 133.

[0036] For example, in the first multi-color visible light modulation driver chip 11, each transmitting sub-circuit receives different electrical signals (such as VIN1, VIN2, and VIN3) during operation, respectively modulating and driving the red LED 131, green LED 132, and blue LED 133 in the first RGB-LED 13 to emit visible light signals of various colors. Preferably, the first multi-color visible light modulation driver chip 11 and the second multi-color visible light modulation driver chip 12 are implemented based on CMOS technology, which is low in cost and has high reliability.

[0037] For example, each of the transmitting sub-circuits is composed of two-stage pre-emphasis circuits, a modulation driving circuit, and a carrier extraction circuit connected together. The first transmitting sub-circuit 101 includes: a first pre-emphasis circuit 111, a first modulation driving circuit 112, and a first carrier extraction circuit 113, as shown below. Figure 3 As shown.

[0038] According to the first transmitting sub-circuit 101, the input electrical signal (VIN) is pre-amplified by a two-stage first pre-emphasis circuit 111 to compensate for the inherent low-pass characteristics of the LED device, making the overall frequency response of the system flat. The first modulation driving circuit 112 (including a modulation circuit module and a series driving circuit module) receives the signal processed by the first pre-emphasis circuit 111. First, the modulation circuit module completes the signal formatting, and then the series driving circuit module amplifies the signal power to drive the red LED in the first RGB-LED 13 to emit a red (R) signal, ultimately realizing the control of the first RGB-LED 13. The switching on and off of the first modulation driving circuit 112, connected in series with the B-LED13, drives the red LED131 in the first RGB-LED13 to emit a red (R) signal. Simultaneously, the control signal of the power transistor in the first modulation driving circuit 112 is fed to the first carrier extraction circuit 113 through a coupling capacitor. This provides a low-impedance discharge path for the remaining carriers, thereby accelerating the extinguishing of the red LED131 in the first RGB-LED13 and improving the emission bandwidth of the first RGB-LED13. Figure 3 As shown.

[0039] In the embodiments of this application, the circuit structures of the first pre-emphasis circuit 111 (PE), the first modulation drive circuit 112 (MD), and the first carrier extraction circuit 113 (CE) can all be implemented by connecting existing circuits based on the principles of this application.

[0040] like Figure 2 As shown, the second transmitting sub-circuit 102 includes a second emphasis circuit 114, a second modulation driving circuit 115, and a second carrier extraction circuit 116; the third transmitting sub-circuit 103 includes a third emphasis circuit 117, a third modulation driving circuit 118, and a third carrier extraction circuit 119. The second modulation driving circuit drives the green LED 132 in the first RGB-LED 13 to emit a green (G) signal; the third modulation driving circuit drives the blue LED 133 in the first RGB-LED to emit a blue (B) signal.

[0041] In this embodiment, the structure of the second multicolor visible light modulation driver chip 12 is the same as that of the first multicolor visible light modulation driver chip 11, and both include three signal transmitting sub-circuits, which have the same structure as the first transmitting sub-circuit 101.

[0042] like Figure 1As shown, in one embodiment, the vertical polarization receiving submodule includes a third convex lens 21, a second vertical polarizer 23, and a first multicolor visible light metasurface light receiver chip 25. The third convex lens 21 is used to converge all the parallel light transmitted from the vertical polarization transmitting submodule of the transmitting module 1. The second vertical polarizer 23 is used to allow only vertically polarized light to pass through the converged light signal. Then, the first multicolor visible light metasurface light receiver chip 25 receives the converged vertically polarized light, converts the multicolor visible light photoelectrically into an analog electrical signal, and then transmits it to the analog-to-digital converter 27 to convert it into a digital electrical signal for output to the subsequent circuit 3.

[0043] like Figure 1 As shown, in one embodiment, the horizontal polarization receiving submodule includes a fourth convex lens 22, a second horizontal polarizer 24, and a second multicolor visible light metasurface photodetector chip 26. The fourth convex lens 22 is used to converge all the parallel light transmitted from the horizontal polarization transmitting submodule of the transmitting module 1. The second horizontal polarizer 24 is used to allow only horizontally polarized light to pass through after convergence. Then, the second multicolor visible light metasurface photodetector chip 26 receives the light, photoelectrically converts the multicolor visible light (RGB light signal) into a corresponding analog electrical signal, and then transmits it to the analog-to-digital converter 27 to convert it into a digital electrical signal (digital signal) for output to the subsequent circuit 3, such as... Figure 5 As shown.

[0044] like Figure 1 As shown in the embodiment of this application, the analog-to-digital converter 27 processes the output signals of the first multicolor visible light metasurface receiver chip 25 and the second multicolor visible light metasurface receiver chip 26 and outputs them. These signals can then be input into the subsequent circuit 3 and output again, realizing the conversion and transmission of optical signals to electrical signals. That is, the six analog signals that the vertical polarization receiving submodule and the horizontal polarization receiving submodule constitute the final output of the VLC system are all input into the analog-to-digital converter 27 and then converted into one digital electrical signal that can be processed by the subsequent circuit 3.

[0045] In the embodiments of this application, the first vertical polarizer 15 and the second vertical polarizer 23 are responsible for filtering out horizontally polarized noise light signals so that the subsequent circuits only receive vertically polarized light signals; the first horizontal polarizer 16 and the second horizontal polarizer 24 are responsible for filtering out vertically polarized noise light signals so that the subsequent circuits only receive horizontally polarized light signals, thereby achieving polarization diversity, preventing signal crosstalk, and finally converting the light transmission path through a convex lens to ensure stable transmission and reception of light signals and improve system sensitivity.

[0046] In one embodiment, such as Figure 1As shown, the first vertical polarizer 15 and the first convex lens 17 in the transmitting module 1 are aligned with the third convex lens 21 and the second vertical polarizer 23 in the corresponding receiving module 2 in the same horizontal direction; similarly, the first horizontal polarizer 16 and the second convex lens 18 in the transmitting module 1 are aligned with the fourth convex lens 22 and the second horizontal polarizer 24 in the receiving module 2 in the same horizontal direction.

[0047] In one embodiment, the first multicolor visible light metasurface light receiver chip 25 is used to receive multiple optical signals (such as RGB light signals) that converge vertically polarized light, and includes three signal receiving sub-circuits, namely a first receiving sub-circuit 2501, a second receiving sub-circuit 2502, and a third receiving sub-circuit 2503, such as... Figure 4 As shown in the diagram, each receiving sub-circuit, from the optical signal input to the digital electrical signal output, consists of a fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating, a transimpedance preamplifier, a limiting amplifier, an equalizer, and an output buffer stage connected in sequence. The output of the output buffer stage is connected to the input of the analog-to-digital converter. The transimpedance preamplifier converts the output current signal of the fully integrated multicolor visible light photodetector into a voltage signal. The limiting amplifier amplifies the voltage signal output by the transimpedance preamplifier to a preset digital voltage level. The equalizer compensates for the frequency response characteristics of the limiting amplifier's output signal, outputting a differential voltage signal at the preset digital voltage level. The output buffer stage converts the differential voltage signal output by the equalizer into a single-ended voltage signal.

[0048] The transimpedance preamplifier, limiting amplifier, equalizer, and output buffer stage described in this application can be implemented using existing corresponding unit circuit structures or corresponding chips based on the principles of this application.

[0049] In terms of specific implementation, such as Figure 4 As shown, the first receiving sub-circuit 2501 includes a red photodetector 25101, a first transimpedance preamplifier (TIA) 252, a first limiting amplifier (LA) 253, a first equalizer (EQU) 254, and a first output buffer stage (FSO) 255, which are connected sequentially in the signal transmission direction. The first transimpedance preamplifier 252 can be a passive feedback transimpedance amplifier, including a feedback resistor R1.

[0050] like Figure 5As shown, when the first multicolor visible light metasurface optical receiver chip 25 is working, the red light signal transmitted through the polarizer illuminates the surface of the red light photodetector 25101 of the first fully integrated multicolor visible light photodetector 251, which converts the red light signal into a current signal. Then, the first transimpedance preamplifier 252 converts the current signal output by the red light photodetector 25101 into a voltage signal. Then, the first limiting amplifier 253 amplifies the voltage signal output by the first transimpedance preamplifier 252 to the voltage level required by the digital processing unit. Then, the first equalizer 254 compensates the frequency response characteristics of the output signal of the first limiting amplifier 253 to improve the bandwidth of the optical receiver chip. The first output buffer stage 255 converts the differential voltage signal output by the first equalizer 254, which has reached the digital voltage level, into a single-ended output voltage signal and provides driving capability. The single-ended voltage signal is output through port VOUT1.

[0051] For example, in this application, the structures of the second receiving sub-circuit 2502 and the third receiving sub-circuit 2503 in the first multicolor visible light metasurface light receiver chip 25 are the same as those of the first receiving sub-circuit 2501. The only difference is that the photodetectors connected to the front end of each receiving sub-circuit are different. Specifically, the photodetector connected to the front end of the second receiving sub-circuit 2502 is a green photodetector 25102, and the photodetector connected to the front end of the third receiving sub-circuit 2503 is a blue photodetector 25103.

[0052] Specifically, the second receiving sub-circuit 2502 includes a green photodetector 25102, a second transimpedance preamplifier 256, a second limiting amplifier 257, a second equalizer 258, and a second output buffer stage 259 in the first fully integrated multicolor visible light photodetector 251; the third receiving sub-circuit 2503 includes a blue photodetector 25103, a third transimpedance preamplifier 2510, a third limiting amplifier 2511, a third equalizer 2512, and a third output buffer stage 2513 in the first fully integrated multicolor visible light photodetector 251.

[0053] like Figure 4 As shown, the structure of the second multicolor visible light metasurface light receiver chip 26 is the same as that of the first multicolor visible light metasurface light receiver chip 25. It receives and converges multiple optical signals (RGB signals) of horizontally polarized light, so the second multicolor visible light metasurface light receiver chip also includes three signal receiving sub-circuits. The structure of the three signal receiving sub-circuits in the second multicolor visible light metasurface light receiver chip 26 is the same as that of the first receiving sub-circuit 2501.

[0054] In this embodiment, the first fully integrated multicolor visible light photodetector 251 includes three photodetectors that detect light signals of different colors, respectively, and achieve selective detection of red, green and blue visible light signals. All of them are photodetectors based on subwavelength polycrystalline silicon gratings. When the grating width and grating period parameters of the subwavelength grating are reasonably designed, when appropriate polarized light is incident, it can selectively respond to light signals of a specific wavelength band and shield light signals of other wavelength bands.

[0055] Figure 6 and Figure 7 The structure of the green photodetector 25102 is shown from both top and cross-sectional perspectives. For example, the blue photodetector 25103 has the same structure as the green photodetector 25102, differing only in the grating width and period of the polysilicon grating. Figure 6 and Figure 7 As shown, the structure of the blue photodetector 25103 / green photodetector 25102 is as follows: a deep N-well region (DN-well) 47 is embedded on a P-type substrate (P-sub) 4; an external active region (P+-AA) 410 of the P-type substrate is embedded around the deep N-well region 47 and near the upper surface of the P-type substrate 4; a P-well region (P-well) 48 is embedded inside the deep N-well region 47; an external active region (N-AA) 420 of the deep N-well region is embedded inside the deep N-well region 47 near the upper surface and around the periphery of the P-well region 48; an external active region (P-AA) 430 of the P-well region is embedded inside the P-well region 48 near the upper surface; and a first shallow trench isolation layer (STI) 49 is embedded in the center position. A set of first periodic gratings 44 made of polycrystalline silicon material is arranged directly above the first shallow trench isolation layer 49.

[0056] Among them, the P-type substrate external active region 410 leads out the P-type substrate active region external electrode 41, the deep N-well region external active region 420 is connected to the cathode external wire 42 of the blue light photodetector / green light photodetector through the cathode contact hole 46 of the blue light photodetector / green light photodetector, and the P-well region external active region 430 is connected to the anode external wire 43 of the blue light photodetector / green light photodetector through the anode contact hole 45 of the blue light photodetector / green light photodetector.

[0057] Figure 8 and Figure 9 The structure of the red photodetector 25101 is shown from both top and cross-sectional views, which differs from that of the green photodetector 25102 and the blue photodetector 25103.

[0058] In the embodiments of this application, the red photodetector 25101 has an N-well region 53 embedded on a P-type substrate 4. A second P-substrate external active region AA (PS-AA) 58 is embedded in the P-type substrate 4 around the periphery of the N-well region 53 and near the upper end surface of the P-type substrate 4. A red photodetector cathode contact hole (N-AA) 54 is embedded in the N-well region 53 near the upper end surface and around the periphery of the N-well region 53. A second shallow trench isolation layer 55 is provided in the center of the N-well region 53. A set of second periodic gratings 52 made of polycrystalline silicon material is arranged directly above the second shallow trench isolation layer 55. A red photodetector anode external wire 51 is led out from the second P-substrate external active region 58, corresponding to the anode of each red photodetector 25101. A red photodetector cathode external wire 50 is connected to the N-well region external active region 56 through the red photodetector cathode contact hole 54, corresponding to the cathode of each red photodetector 25101.

[0059] The fully integrated multicolor visible light photodetector technology described in this application embodiment adopts the fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating disclosed in CN121262906A. For any related details not covered herein, please refer to the contents of that patent application.

[0060] The fully integrated multicolor visible light photodetector (PSG-PD) described in this application adopts the above design scheme, combining the subwavelength dielectric grating filtering theory with standard CMOS process capabilities to achieve channel separation of the VLC system receiver module.

[0061] In this application, the second fully integrated multicolor visible light photodetector (PSG-PD) in the second multicolor visible light metasurface photodetector chip 26 has the same structure as the first fully integrated multicolor visible light photodetector (PSG-PD) 251, and both can respond to red, green, and blue light signals respectively. Because the detection structure is sensitive to the polarization direction of light, the polarization directions of the light incident on the surfaces of the first multicolor visible light metasurface photodetector chip 25 and the second multicolor visible light metasurface photodetector chip 26 are perpendicular to each other. That is, the directions of the photodetector gratings in the incident light structure of the second fully integrated multicolor visible light photodetector (PSG-PD) and the first fully integrated multicolor visible light photodetector (PSG-PD) 251 are perpendicular to each other.

[0062] The CMOS multi-channel VLC system proposed in this invention utilizes standard CMOS technology for both the multi-color visible light modulation driver chip and the multi-color visible light metasurface receiver chip in the transceiver module, enabling miniaturization and integration, thus significantly reducing manufacturing costs. By employing RGB three-color light as the data transmission carrier, and with both horizontal and vertical polarization communication capabilities in the transceiver module, this system can simultaneously perform six high-speed communications, greatly improving the communication efficiency of the VLC system.

[0063] In addition, by introducing polarizers and convex lenses between the transceiver modules of the VCL system, polarization diversity and wavelength division multiplexing are achieved. This not only ensures the signal stability of the system during communication, but also effectively solves the signal crosstalk problem of multicolor VLC systems. At the same time, based on the advantages of polarized light, this system also has great application prospects in encrypted communication and high-density data storage scenarios, while overcoming the problems of large size, high power consumption, high cost and low communication efficiency of traditional VLC systems.

[0064] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A multi-channel VLC system based on CMOS technology, characterized in that, Based on polarization diversity and wavelength division multiplexing technology, it includes a transmitting module and a receiving module; the multicolor visible light modulation driver chip of the transmitting module and the multicolor visible light metasurface light receiver chip of the receiving module are both monolithically integrated using CMOS technology; the transmitting module includes a vertical polarization transmitting submodule and a horizontal polarization transmitting submodule; the receiving module includes a vertical polarization receiving submodule and a horizontal polarization receiving submodule. The vertical polarization emission submodule converts the three unpolarized lights emitted by the first RGB-LED according to the three driving signals VIN1-VIN3 into divergent vertically polarized lights, and then into three parallel lights for emission. The vertical polarization receiving submodule receives the three parallel light signals emitted by the vertical polarization emission submodule, converts them into three converging vertically polarized light signals, and then, after being filtered by a metasurface, photoelectrically converts them into three analog electrical signals. The horizontal polarization emission submodule converts the three unpolarized lights emitted by the second RGB-LED according to the three driving signals VIN4-VIN6 into divergent horizontally polarized lights, and then into three parallel lights. The system includes: a light emission module; a horizontal polarization receiving submodule, used to receive three parallel light signals emitted by the horizontal polarization emission submodule and convert them into three converged horizontally polarized light signals, which are then photoelectrically converted into three analog electrical signals after being filtered by a metasurface; six analog electrical signals are converted into one digital electrical signal for output; a vertical polarization emission submodule includes a first multi-color visible light modulation driver chip, a first vertical polarizer, and a first convex lens, the first multi-color visible light modulation driver chip being connected to a first RGB-LED, and the first vertical polarizer and the first convex lens being located sequentially on the light-emitting side of the first RGB-LED; and a second multi-color visible light emission submodule. The system comprises a light modulation driver chip, a first horizontal polarizer, and a second convex lens. The second multi-color visible light modulation driver chip is connected to a second RGB-LED. The first horizontal polarizer and the second convex lens are sequentially located on the light-emitting side of the second RGB-LED. Both the first and second multi-color visible light modulation driver chips are implemented using CMOS technology and each includes three signal transmission sub-circuits. The output terminals of each of the three signal transmission sub-circuits are connected to an LED, namely a red LED, a green LED, and a blue LED. The signal transmission sub-circuit includes a two-stage pre-emphasis circuit, a modulation driver circuit, and a carrier extraction circuit. The input of the pre-emphasis circuit is connected to the LED driving signal, the output of the pre-emphasis circuit is connected to the input of the modulation driving circuit, the output of the modulation driving circuit is connected to the input of the carrier extraction circuit, and the output of the carrier extraction circuit is connected to an LED. The pre-emphasis circuit is used to pre-boost the high-frequency components of the input signal, the modulation driving circuit is used to modulate the output signal of the pre-emphasis circuit and then amplify the power to drive the LED in the RGB-LED to emit red, blue, and green light, respectively, and the carrier extraction circuit is used to discharge the remaining carriers according to the control signal of the modulation driving circuit, so that the LED of the RGB-LED is turned off.

2. The multi-channel VLC system based on CMOS technology according to claim 1, characterized in that, The vertical polarization receiving submodule includes a third convex lens, a second vertical polarizer, and a first multi-color visible light metasurface optical receiver chip. The third convex lens focuses the parallel light transmitted from the vertical polarization transmitting submodule, while the second vertical polarizer only allows vertically polarized light in the focused light signal to pass through. The first multi-color visible light metasurface optical receiver chip receives the vertically polarized light and outputs an analog electrical signal to an analog-to-digital converter to form a digital electrical signal output. The horizontal polarization receiving submodule includes a fourth convex lens, a second horizontal polarizer, and a second multi-color visible light metasurface optical receiver chip. The fourth convex lens focuses the parallel light transmitted from the horizontal polarization transmitting submodule, while the second horizontal polarizer only allows horizontally polarized light in the focused light signal to pass through. The second multi-color visible light metasurface optical receiver chip receives the horizontally polarized light and outputs an analog electrical signal to an analog-to-digital converter to form a digital electrical signal output.

3. The multi-channel VLC system based on CMOS technology according to claim 2, characterized in that, The first multicolor visible light metasurface light receiver chip and the second multicolor visible light metasurface light receiver chip have the same structure, each including three receiver sub-circuits. The front end of each receiver sub-circuit is connected to a fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating.

4. The multi-channel VLC system based on CMOS technology according to claim 3, characterized in that, The front ends of the three receiving sub-circuits are connected to the fully integrated multicolor visible light photodetectors, namely a red light photodetector, a blue light photodetector, and a green light photodetector, which are used to detect red light, blue light, and green light signals, respectively.

5. The multi-channel VLC system based on CMOS technology according to claim 3, characterized in that, The three receiving sub-circuits, from the optical signal input terminal to the digital electrical signal output terminal, are sequentially connected as follows: a fully integrated multicolor visible light photodetector based on a subwavelength polycrystalline silicon grating, a transimpedance preamplifier, a limiting amplifier, an equalizer, and an output buffer stage. The output terminal of the output buffer stage is connected to the input terminal of the analog-to-digital converter. Specifically, the transimpedance preamplifier is used to convert the output current signal of the fully integrated multicolor visible light photodetector into a voltage signal; the limiting amplifier is used to amplify the voltage signal output by the transimpedance preamplifier to a preset digital voltage level; the equalizer is used to compensate for the frequency response characteristics of the output signal of the limiting amplifier and output a differential voltage signal at the preset digital voltage level; and the output buffer stage is used to convert the differential voltage signal output by the equalizer into a single-ended output voltage signal.

6. The multi-channel VLC system based on CMOS technology according to claim 3, characterized in that, The fully integrated multicolor visible light photodetector based on subwavelength polycrystalline silicon gratings selectively responds to signals of vertically or horizontally polarized light incident in a preset wavelength band, and blocks light signals in non-preset wavelength bands, according to the grating width and grating period parameters of the subwavelength grating.

7. The multi-channel VLC system based on CMOS technology according to claim 3, characterized in that, The fully integrated multicolor visible light photodetector based on subwavelength polycrystalline silicon grating is a silicon-based P-type substrate detector fabricated using CMOS technology.

Images