A broadband two-dimensional scanning photonics terahertz high-speed communication device

Abstract

This invention discloses a broadband two-dimensional scanning photonic terahertz high-speed communication device, comprising a photonic terahertz broadband signal transmitter, a terahertz Riesling prism antenna, and a terahertz Cramer-Kroni receiver. The photonic terahertz broadband signal transmitter includes a digital-to-analog converter (DAC), a first laser, an optoelectronic modulator, a first polarization-maintaining tunable optical attenuator, a polarization-maintaining optical amplifier, an optical coupler, a second laser, a second polarization-maintaining tunable optical attenuator, a photodetector, and a power amplifier. The terahertz Riesling prism antenna includes a horn antenna, a phase-calibrated linear gradient phase-shifting surface, and a linear gradient phase-shifting surface. The terahertz Cramer-Kroni receiver includes, in sequence, an attenuator, a low-noise amplifier, an intensity detector, an ADC sampling unit, a Cramer-Kroni processing unit, and a DSP processing unit. This invention has the advantages of flexible and adjustable beam, large bandwidth, simple system structure, and easy extension to higher frequencies.

Description

Technical Field

[0001] This invention belongs to the field of terahertz communication technology, specifically relating to a broadband photonics terahertz high-speed communication device with two-dimensional beam scanning capability. Background Technology

[0002] Currently, terahertz communication systems with beamforming capabilities mainly employ an "electronic frequency-doubling transmitter + phased array antenna + superheterodyne receiver" scheme. However, this scheme not only requires complex and expensive circuit design and beamforming chips, but also faces challenges in generating and demodulating broadband high-speed signals due to electronic bottlenecks. Recently, some research has adopted an "electronic local oscillator + FPGA-controlled active metasurface + superheterodyne receiver" scheme, but this scheme is mainly limited by modulation bandwidth, making it difficult to achieve an overall rate in the Gbps range. Furthermore, the "photonic heterodyne transmitter + optical delay phased array antenna + superheterodyne receiver" scheme is currently limited by process technology and scale, resulting in limitations in scanning dimensions. From the transmitter's perspective, photonic solutions have advantages over electronic solutions in broadband signal generation. From the perspective of beamforming antennas, traditional mechanically scanned antennas have disadvantages such as large size, large mass, and large scanning inertia, while phased array antennas require complex, expensive, and carefully designed feed networks and TR components, and active metasurfaces suffer from limited modulation bandwidth. Fortunately, a passive metasurface beamforming antenna based on the Rice prism principle can overcome the above problems to some extent, providing a broadband two-dimensional scanning scheme. From the receiver's perspective, while the widely used superheterodyne receiver can achieve high-order complex signal reception and demodulation, it is limited by intermediate frequency bandwidth and the complex and expensive terahertz local oscillator, and the mixer performance is not conducive to cost-sensitive scenarios. However, recently, low-hardware-complexity communication schemes based on the Kramer-Kronig principle have been widely studied, allowing the reconstruction of high spectral efficiency complex signals using only one intensity detector, and possessing the ability to achieve high spectral efficiency communication with low hardware complexity.

[0003] In summary, current research still has two limitations and shortcomings: First, the traditional terahertz communication system with beam control capability uses an "electronic frequency doubling transmitter + phased array antenna + superheterodyne receiver" scheme, which has limited system bandwidth and complex structure; Second, other terahertz communication systems based on active metasurfaces and optical time-delay phased arrays also have problems such as limited modulation bandwidth and limited scanning dimension, which restrict their application scenarios. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a broadband two-dimensional scanning photonic terahertz high-speed communication device based on a combination of the Rice prism principle and the Cramer-Kroni principle. This device uses a photonic transmitter to generate broadband terahertz signals, employs the Rice prism principle to control the antenna beam, and utilizes the Cramer-Kroni principle to achieve efficient reception of complex modulation formats. Through the organic combination of these three elements, the system as a whole possesses advantages such as flexible and adjustable beam, large bandwidth, simple system structure, and ease of extension to higher frequencies.

[0005] The objective of this invention is achieved through the following technical solution: a broadband two-dimensional scanning photonics terahertz high-speed communication device, comprising a photonics terahertz broadband signal transmitter, a terahertz Ries prism antenna, and a terahertz Cramer-Kroni receiver; the terahertz Ries prism antenna is used simultaneously at both the signal transmitting end and the signal receiving end;

[0006] The photonic terahertz broadband signal transmitter includes a digital-to-analog converter (DAC), a first laser, an optoelectronic modulator, a first polarization-maintaining tunable optical attenuator, a polarization-maintaining optical amplifier, an optical coupler, a second laser, a second polarization-maintaining tunable optical attenuator, a photodetector, and a power amplifier.

[0007] A digital-to-analog converter (DAC) generates a digital signal with a specified modulation format and converts it into an analog signal, which is then sent to an optoelectronic modulator. The DAC is connected to the electro-optic modulator. The optical signal generated by the first laser is used as the modulation light and passes sequentially through the electro-optic modulator, the first polarization-maintaining tunable optical attenuator, and the polarization-maintaining optical amplifier before being sent to one input of the coupler. The optical signal generated by the second laser provides a reference optical signal with a terahertz frequency interval and is sent to the other input of the coupler. The coupler couples the modulation optical signal and the reference optical signal, and the coupled signal passes through the second polarization-maintaining tunable optical attenuator before being input to a photodetector. The photodetector converts the optical signal into a terahertz signal and then inputs it to a power amplifier. The power amplifier amplifies the signal and then radiates it directionally into free space via a Ricean prism antenna.

[0008] The terahertz Rice prism antenna consists of, from bottom to top, a horn antenna, a phase calibration-linear gradient phase shift surface, and a linear gradient phase shift surface 2. The phase calibration-linear gradient phase shift surface includes a phase calibration surface and a linear gradient phase shift surface 1. The phase distribution of the phase calibration-linear gradient phase shift surface is the sum of the phase of the phase calibration surface and the phase of the linear gradient phase shift surface 1. The phase distribution of the linear gradient phase shift surface 2 is consistent with that of the linear gradient phase shift surface 1.

[0009] The terahertz Kramer-Kroni receiver includes an attenuator, a low-noise amplifier, an intensity detector, an ADC sampling unit, a Kramer-Kroni processor, and a DSP processing unit connected in sequence.

[0010] The digital signal is a single-sideband QAM modulation format using a virtual carrier.

[0011] The electro-optic modulator is an IQ modulator and needs to operate at the Null point.

[0012] The photodetector is a PIN-type structure or a single-row carrier UTC-type structure.

[0013] The phase calibration surface, linear gradient phase shift surface 1, and linear gradient phase shift surface 2 are all composed of multiple electromagnetic metasurface units arranged according to the phase distribution.

[0014] The beneficial effects of this invention are:

[0015] 1. This invention enables the convenient and flexible generation of broadband terahertz signals through a photonic terahertz transmitter, and facilitates the extension to higher terahertz frequencies.

[0016] 2. This invention provides the radiation direction through a Rice prism antenna based on a broadband passive metasurface. Figure 2 It has 3D scanning capability and is easy to control.

[0017] 3. This invention provides complex signal demodulation functionality with low structural complexity using a Cramer-Kroni receiver.

[0018] 4. By organically combining a broadband photonic heterodyne transmitter, a Rice prism beam-tuning antenna, and a Cramer-Kroni receiver, this invention enables the system to have the advantages of flexible beam adjustment, large bandwidth, simple system structure, and easy extension to high frequencies. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the photonic terahertz transmitter of the communication device of the present invention;

[0020] Figure 2 This is a schematic diagram of the digital signal processing flow at the transmitting end of the communication device of the present invention;

[0021] Figure 3 This is a schematic diagram of the Rice prism antenna structure used in the communication device of the present invention;

[0022] Figure 4 This is a schematic diagram of the Kramer-Kroni receiver and a schematic diagram of the algorithm flow of the communication device of the present invention;

[0023] Figure 5 This is a schematic diagram illustrating the overall implementation of the communication device of the present invention;

[0024] Figure 6 This is a schematic diagram of the phase distribution of the two phase-shifting surfaces of the Rice prism antenna in this embodiment. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0026] The present invention provides a broadband two-dimensional scanning photonics terahertz high-speed communication device, comprising a photonics terahertz broadband signal transmitter, a terahertz Ries prism antenna, and a terahertz Cramer-Kroni receiver;

[0027] The photonic terahertz broadband signal transmitter generates single-sideband (SSB) QAM signals that meet the minimum phase condition required for Kramer-Kronig reception and employs virtual carrier technology to provide a reference carrier. The terahertz Kramer-Kronig (KK) receiver is a low-complexity receiver based on amplitude detection for complex signal reception and demodulation, enabling high-speed QAM signal reception. The terahertz Risley-Prism (RP) antenna is used simultaneously at both the transmitting and receiving ends. The Risley-Prism (RP) antenna employs two thin, phase-shifting surfaces with a specific phase distribution, achieved using metasurface technology, to flexibly adjust the radiation beam and change the direction of information transmission.

[0028] like Figure 1 As shown, the photonic terahertz broadband signal transmitter includes a digital-to-analog converter (DAC), a first laser, an optoelectronic modulator, a first polarization-maintaining tunable optical attenuator, a polarization-maintaining optical amplifier, an optical coupler, a second laser, a second polarization-maintaining tunable optical attenuator, a photodetector (PD), and a power amplifier.

[0029] A digital-to-analog converter (DAC) generates a digital signal with a specified modulation format (such as QAM) and converts it into an analog signal, which is then sent to an electro-optic modulator. The DAC is connected to the electro-optic modulator; its generation process is as follows: Figure 2 As shown, the process includes steps such as pseudo-random sequence generation, encoding (Gray), mapping, pulse shaping, SSB transformation, adding a virtual carrier, and resampling. Each step is existing technology and will not be described in detail here. The digital signal is a single-sideband QAM modulation format using a virtual carrier.

[0030] The electro-optic modulator is an IQ modulator and needs to operate at the Null point to obtain a carrier-suppressed modulated signal.

[0031] The optical signal generated by the first laser is used as modulated light and sequentially passes through an electro-optic modulator, a first polarization-maintaining tunable optical attenuator, and a polarization-maintaining optical amplifier before being sent to one input of the coupler. The optical signal generated by the second laser is used to provide a reference optical signal with a terahertz frequency interval and is sent to the other input of the coupler. The coupler is used to couple the modulated optical signal and the reference optical signal, and the coupled signal is input to the photodetector after passing through a second polarization-maintaining tunable optical attenuator. The optical signal input to the photodetector is expressed using a mathematical model as follows:

[0032]

[0033] Where, ω C1 With ω C2 These represent the operating frequencies of the two lasers, ω and ω'. Z The shift frequency of the baseband signal up-conversion is represented by s(t), which is the baseband digital signal in various required modulation formats. c and A are used to represent the reference carrier amplitude and the second laser amplitude, respectively.

[0034] The photodetector is a PIN-type structure or a single-row carrier UTC-type structure. Based on the heterodyne beat frequency principle, it performs square-law detection on the received signal to generate a terahertz signal. The output signal of the photodetector, which contains the loaded terahertz wave signal, is expressed using a mathematical model as follows:

[0035]

[0036] ω M =ω C1 -ω C2

[0037] The photodetector converts the optical signal into a terahertz signal and then inputs it into a power amplifier. The power amplifier amplifies the signal and then sends the generated terahertz signal to the terahertz broadband low-complexity two-dimensional scanning Rice prism antenna at the transmitter. The Rice prism antenna then radiates the signal directionally into free space.

[0038] The terahertz Rice prism antenna includes a horn antenna, a phase-calibrated linear gradient phase-shifting surface, and a linear gradient phase-shifting surface. The horn antenna is used to radiate terahertz signals generated by a photonic terahertz broadband signal transmitter into free space or to receive terahertz signals in free space. The phase-calibrated linear gradient phase-shifting surface is used to collimate the horn antenna beam from divergence and to deflect the collimated, highly directional beam from the center to a specified angle. This specified deflection angle is related to the phase gradient value adopted by the linear phase gradient surface, typically using an interval of 45° or 60°. The linear gradient phase-shifting surface is used to perform a secondary deflection on the calibrated deflected beam. The transmitting end uses two layers of phase-shifting surfaces for beamforming to control the beam scanning direction. The receiving end uses two layers of phase-shifting surfaces to enable the horn antenna to obtain the highest received power.

[0039] like Figure 3 As shown, the terahertz Rice prism antenna consists of a horn antenna, a phase calibration-linear gradient phase shift surface, and a linear gradient phase shift surface 2, from bottom to top. The phase calibration-linear gradient phase shift surface includes a phase calibration surface and a linear gradient phase shift surface 1. The phase distribution of the phase calibration-linear gradient phase shift surface is the sum of the phase of the phase calibration surface and the phase of the linear gradient phase shift surface 1. The phase distribution of the linear gradient phase shift surface 2 is consistent with that of the linear gradient phase shift surface 1.

[0040] The phase calibration surface, linear gradient phase shift surface 1, and linear gradient phase shift surface 2 are all composed of multiple electromagnetic metasurface units arranged according to the phase distribution.

[0041] The directional radiation direction of the terahertz Rice prism antenna is jointly determined by both the phase calibration-linear gradient phase-shifting surface and the linear gradient phase-shifting surface. The radiation array factor formula for each phase-shifting surface is expressed as:

[0042]

[0043] in, dx represents the radiation array factor, k represents the wave vector, and dx and dy represent the row spacing and column spacing of the electromagnetic metasurface unit, respectively. This represents the amplitude and phase of the electromagnetic field after passing through two phase-shifting surfaces. Furthermore, both the phase-calibrated linear gradient phase-shifting surface and the linear gradient phase-shifting surface are composed of multiple electromagnetic metasurface units. For ease of representation, the X-axis is used as the horizontal axis and the Y-axis as the vertical axis. Each unit of each phase-shifting surface is numbered from left to right and from bottom to top, thus uniquely identifying the unit in the m-th row and n-th column, as shown below. Figure 6 As shown. Ultimately, due to the change in phase caused by rotating the two phase-shifting surfaces, the beam direction can be flexibly and effectively controlled.

[0044] like Figure 4 As shown, the terahertz Cramer-Kroni receiver includes an attenuator, a low-noise amplifier, an intensity detector, an ADC sampling unit, a Cramer-Kroni processing unit, and a DSP processing unit connected in sequence. The attenuator controls the power of the terahertz signal received by the Rice prism antenna and sends the signal to the low-noise amplifier. The low-noise amplifier amplifies the received terahertz signal and sends the amplified terahertz signal to the intensity detector. The intensity detector extracts the envelope of the received terahertz signal.

[0045] The ADC sampling unit samples the terahertz signal envelope according to requirements, saves the sampled terahertz signal envelope, and then uses the Cramer-Krone processing unit to reconstruct the complex signal. The Cramer-Krone processing demodulates the envelope signal into an IQ complex signal format and sends it to the DSP processing unit. The Cramer-Krone processing mainly includes resampling, the Cramer-Krone algorithm, carrier removal, frequency conversion, and downsampling. The Cramer-Krone algorithm mainly includes square root operation, logarithmic operation, Hilbert transform, exponential operation, and multiplication operation. The specific formula for reconstructing the complex signal using the Cramer-Krone relation is expressed as follows:

[0046]

[0047] Among them, S L ′(t) is the sampled value of the envelope signal output by the intensity detector. H[·] is the Hilbert transform of the amplitude signal, used to recover the phase information of the signal.

[0048] In this embodiment, the two lasers of the transmitter operate at frequencies of 1550 nm and 1549.2 nm, respectively, with a frequency interval of 100 GHz (0.1 THz). The digital signal is generated by PRBS, then encoded with Gray code, and finally mapped to a constellation diagram. The specific data mapping format depends on the selected modulation format; here, 16QAM modulation is used. The data symbol rate is set to 10 GBd, and the pulse shaping upsampling rate is set to 6. Subsequently, the signal undergoes a Hilbert transform operation and a dummy carrier is added.

[0049] The digital signal is converted into a matched analog signal by a 60GSa / s DAC and then input to an IQ modulator to generate an optical carrier signal. Subsequently, after polarization-maintaining VOA and polarization-maintaining EDFA amplification, the power of the optical signal is amplified to 8dBm. The amplified optical signal is then coupled with an optical signal generated by a second laser with a frequency interval of 0.1THz. The coupled optical signal is then power-adjusted by the polarization-maintaining VOA and input to a PD to generate a terahertz signal with a center frequency of 0.1THz. Finally, the terahertz signal is amplified by a power amplifier and sent to a metasurface-based terahertz Ricean antenna for radiating the signal into free space.

[0050] At the receiving end, the same terahertz Rice prism antenna is used to receive terahertz signals in free space. For example... Figure 5 As shown in the figure, antennas P1 and P2 at the receiving end represent the target (receiving end) at two different deflection angles. The Rice prism antennas at the transmitting and receiving ends need to be beam-aligned to ensure maximum signal power reception.

[0051] like Figure 6 As shown in Figures (a) and (b), the phase distribution of the phase calibration-linear gradient phase shift surface and the linear gradient phase shift surface used in this embodiment of the terahertz broadband low-complexity two-dimensional scanning Rice prism antenna are respectively set to 60°.

[0052] The received terahertz signal, after passing through an attenuator and a low-noise amplifier, is input to an intensity detector. The intensity detector outputs the envelope of the terahertz signal, which is then sampled by an 80 GSa / s ADC. Considering the digital upsampling requirements of the Cramer-Kroni algorithm in a low-complexity terahertz Cramer-Kroni receiver, the upsampling rate of the sampled signal needs to be controlled at 6 sps or higher. If the actual sampling rate is insufficient, it needs to be increased through digital upsampling. After the sampled signal is reconstructed into a complex signal by the Cramer-Kroni algorithm, it still needs to undergo carrier removal, frequency conversion, and downsampling to finally obtain the baseband signal, i.e., the baseband digital information is recovered.

[0053] In summary, this embodiment provides a broadband two-dimensional scanning photonic terahertz high-speed communication device. It employs a photonic transmitter to generate broadband terahertz signals, a Rice prism principle to control the antenna beam, and a Cramer-Kroni principle to achieve efficient reception of complex modulation formats. Through the organic combination of these three elements, a broadband photonic terahertz high-speed communication system with flexible beam scanning capabilities is realized.

[0054] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A broadband two-dimensional scanning photonics terahertz high-speed communication device, characterized in that, This includes a photonics terahertz broadband signal transmitter, a terahertz Ries prism antenna, and a terahertz Cramer-Kroni receiver; the terahertz Ries prism antenna is used simultaneously at both the signal transmitting and receiving ends. The photonic terahertz broadband signal transmitter includes a digital-to-analog converter (DAC), a first laser, an electro-optic modulator, a first polarization-maintaining tunable optical attenuator, a polarization-maintaining optical amplifier, an optical coupler, a second laser, a second polarization-maintaining tunable optical attenuator, a photodetector, and a power amplifier. A digital-to-analog converter (DAC) generates a digital signal with a specified modulation format and converts it into an analog signal, which is then sent to an electro-optic modulator. The DAC is connected to the electro-optic modulator. The optical signal generated by the first laser is used as the modulation light and passes sequentially through the electro-optic modulator, the first polarization-maintaining tunable optical attenuator, and the polarization-maintaining optical amplifier before being sent to one input of the optical coupler. The optical signal generated by the second laser provides a reference optical signal with a terahertz frequency interval and is sent to the other input of the optical coupler. The optical coupler couples the modulation optical signal and the reference optical signal and then inputs the coupled signal to the photodetector after passing through the second polarization-maintaining tunable optical attenuator. The photodetector converts the optical signal into a terahertz signal, which is then input into a power amplifier. The power amplifier amplifies the signal and then directs it into free space through a terahertz Rice prism antenna. The terahertz Rice prism antenna consists of, from bottom to top, a horn antenna, a phase calibration-linear gradient phase shift surface, and a linear gradient phase shift surface 2. The phase calibration-linear gradient phase shift surface includes a phase calibration surface and a linear gradient phase shift surface 1. The phase distribution of the phase calibration-linear gradient phase shift surface is the sum of the phase of the phase calibration surface and the phase of the linear gradient phase shift surface 1. The phase distribution of linear gradient phase-shifting surface 2 is consistent with that of linear gradient phase-shifting surface 1; The terahertz Kramer-Kroni receiver includes an attenuator, a low-noise amplifier, an intensity detector, an ADC sampling unit, a Kramer-Kroni processor, and a DSP processing unit connected in sequence.

2. The broadband two-dimensional scanning photonics terahertz high-speed communication device according to claim 1, characterized in that, The digital signal is a single-sideband QAM modulation format using a virtual carrier.

3. The broadband two-dimensional scanning photonics terahertz high-speed communication device according to claim 1, characterized in that, The electro-optic modulator is an IQ modulator and needs to operate at the Null point.

4. The broadband two-dimensional scanning photonics terahertz high-speed communication device according to claim 1, characterized in that, The photodetector is a PIN-type structure or a single-row carrier UTC-type structure.

5. A broadband two-dimensional scanning photonics terahertz high-speed communication device according to claim 1, characterized in that, The phase calibration surface, linear gradient phase shift surface 1, and linear gradient phase shift surface 2 are all composed of multiple electromagnetic metasurface units arranged according to the phase distribution.

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