Generation system of photon multi-frequency-multiplication ultrahigh-order vector millimeter wave signal

Abstract

The invention discloses a system for generating a photon multi-frequency-multiplication ultrahigh-order vector millimeter wave signal. The system comprises a digital signal processing module, an arbitrary waveform generator, a Mach-Zehnder modulator, an external cavity laser module, a standard single-mode optical fiber module and a photodiode module (160), wherein the digital signal processing module is used for generating CE-DSM electric signals; the arbitrary waveform generator, the Mach-Zehnder modulator and the photodiode module are used for carrying out photon frequency doubling processing on the CE-DSM electric signal to generate an optical frequency doubling signal, and a millimeter wave electric signal is formed after hybrid transmission on a 15km SSMF and a 1m wireless link. According to the technical scheme, the envelope of the signal can be kept constant, and intensity-dependent distortion caused by photon frequency doubling and a complex transmitter DSP is effectively avoided; meanwhile, in the implementation process, the ultrahigh-order vector millimeter wave signal can be effectively generated without pre-coding of a transmitter, a complex I / Q modulator and additional laser.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a generation system of ultra-high-order vector millimeter wave signals based on photon multiple frequency doubling. Background Art

[0002] With the advent of 5G commercialization, various new applications based on communication, such as unmanned driving, mobile X-haul, and smart medical care, have gradually emerged, bringing huge demands for wireless traffic and mobile networks. Radio over fiber (RoF) systems have become a promising candidate for future broadband wireless communications due to their large fiber communication capacity, enhanced flexibility, and minimal propagation delay, and have attracted widespread attention. The generation of millimeter wave (mmW) signals is simple and cost-effective, and it can be seamlessly integrated with abundant bandwidth resources and optical fiber and wireless communications, which is crucial to the realization of RoF technology. However, the current digital interface based on the common radio interface (CPRI) protocol has only 15 quantization bits, so the bandwidth efficiency is extremely low. In addition, due to the high signal-to-noise ratio (SNR) requirements of RoF systems and small nonlinear tolerance, it is difficult to generate ultra-high-order vector millimeter wave signals in RoF systems.

[0003] With the development of wireless technology in recent years, delta-sigma modulation (DSM) technology has become a hot topic in the wireless field because it can bring huge signal-to-noise ratio gain and improve the capacity of optical and wireless access systems. Therefore, combining DSM technology with phase modulation to generate vector millimeter-wave signals with simple structure and ultra-high modulation format is an important research direction. A study proposed a dual-vector RF signal generation scheme based on bandpass DSM, which successfully generated single-carrier 64QAM millimeter-wave signals and single-carrier 128QAM millimeter-wave signals; some researchers used 1-bit DSM to generate 1024-QAM / 4096QAM millimeter-wave signals, but these schemes require additional lasers for photon heterodyne detection.

[0004] Based on the above situation, a generation scheme of ultra-high-order vector millimeter-wave signals is needed, which can effectively generate photon-frequency-doubled millimeter-wave signals without the need for transmitter pre-coding, additional lasers and complex I / Q modulators. Summary of the invention

[0005] To achieve the above-mentioned purpose, the present application provides a photon multi-frequency ultra-high-order vector millimeter-wave signal generation system, comprising: a digital signal processing module, an arbitrary waveform generator, a Mach-Zehnder modulator, an external cavity laser module, a standard single-mode optical fiber module and a photodiode module;

[0006] Wherein, the digital signal processing module is used to generate a CE-DSM electrical signal;

[0007] Arbitrary waveform generator, Mach-Zehnder modulator and photodiode module are used to perform photon frequency doubling on CE-DSM electrical signal to generate optical frequency doubling signal, and form millimeter wave electrical signal after mixed transmission of 15km SSMF and 1m wireless link.

[0008] Wherein, generating a CE-DSM electrical signal comprises:

[0009] Mapping a pseudo-random binary sequence into a complex-valued signal with 4096-order QAM;

[0010] The baseband signal is generated by performing OFDM modulation through 1024-point inverse fast Fourier transform; the baseband signal is an OFDM signal including 0.5-Gbaud and 0.2-Gbaud; the DSM-NRZ signal is an NRZ signal including 4-GSa / s and 10-GSa / s;

[0011] The baseband signal is oversampled and processed by one bit of DSM to be converted into a DSM-NRZ signal;

[0012] The DSM-NRZ signal is up-sampled, root raised cosine filtered, phase modulated and up-converted to form a CE-DSM electrical signal.

[0013] Among them, the arbitrary waveform generator is used to generate an analog waveform for transmission according to the CE-DSM electrical signal;

[0014] The external cavity laser module is used to generate continuous wavelength laser waves, which serve as the optical input carrier signal of the Mach-Zehnder modulator. The line width of the external cavity laser module is 500Hz, and the maximum emission optical power is 13.7dBm.

[0015] The Mach-Zehnder modulator modulates the CE-DSM electrical signal into an optical input carrier signal and outputs an optical frequency-doubled signal.

[0016] Further, the optical frequency-doubled signal enters the photodiode module after being transmitted through the standard single-mode optical fiber module;

[0017] The photodiode module converts the optical frequency-doubled signal into a 2n-fold millimeter-wave electrical signal.

[0018] Furthermore, the millimeter wave electrical signal can be restored to a CE-DSM electrical signal after digital processing, phase demodulation, DSM demodulation and OFDM demodulation.

[0019] According to the present invention, a 1-bit DSM can be used to quantize a complex continuous analog signal into an NRZ signal. With the help of phase modulation, the envelope of the CE-DSM signal can be kept constant, which can effectively avoid the intensity-dependent distortion caused by photon frequency doubling and complex transmitter DSP. At the same time, the implementation of the present invention does not require transmitter precoding, complex I / Q modulators, or additional lasers, and can effectively generate photon frequency doubling millimeter-wave signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of a generation system of ultra-high-order vector millimeter-wave signals based on photon multiple frequency according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of a signal spectrum during a signal transmission process according to an embodiment of the present invention;

[0022] Figure numerals: 110 - digital signal processing module, 120 - arbitrary waveform generator, 130 - external cavity laser module, 140 - Mach-Zehnder modulator, 150 - standard single-mode optical fiber module, 160 - photodiode module, 170 - antenna module, 180 - data signal analyzer, 190 - digital signal processing module. DETAILED DESCRIPTION

[0023] The present invention proposes a generation system of ultra-high and ultra-high-order vector millimeter-wave signals based on photon multi-frequency: a 1-bit DSM is used to quantize a complex continuous analog signal into an NRZ signal for transmission. With the help of phase modulation, the envelope of the transmitted CE-DSM signal can be kept constant, which can effectively avoid the intensity-dependent distortion caused by photon multiplication and complex transmitter DSP. At the same time, the signal generation and transmission process does not require transmitter precoding, complex I / Q modulators, or additional lasers, and can effectively generate, transmit, and analyze photon multiplication millimeter-wave signals.

[0024] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings.

[0025] The structure of the generation system of ultra-high-order vector millimeter wave signals based on photon multiple frequency multiplication proposed by the present invention is as follows: Figure 1 The millimeter wave electrical signal generating unit includes: a digital signal processing module (Tx DSP) at the transmitting end, an arbitrary waveform generator, a Mach-Zehnder modulator, an external cavity laser module, a standard single-mode optical fiber module and a photodiode module;

[0026] The digital signal processing module is used to generate a CE-DSM electrical signal;

[0027] Generating a CE-DSM electrical signal includes the following steps:

[0028] 1) Map the pseudo-random binary sequence (PRBS) to a complex-valued signal with 4096-order QAM, and then perform OFDM modulation through a 1024-point inverse fast Fourier transform (IFFT) to generate an ultra-high-order vector baseband signal, which includes 0.5-Gbaud and 0.2-Gbaud OFDM signals. In order to obtain a real-valued and oversampled OFDM sequence, the data input to the IFFT in this step has the characteristics of conjugate symmetry. Among them, the OFDM signal is generated in MATLAB with 452 data subcarriers.

[0029] 2) oversampling and one-bit DSM processing are performed on the baseband signal to convert it into a DSM-NRZ signal, including 4-GSa / s and 10-GSa / s NRZ signals respectively; upsampling and root raised cosine filtering are performed on the DSM-NRZ signal, and the signal spectrum after root raised cosine filtering is as follows: Figure 2 As shown in part (a), the horizontal axis represents the signal frequency and the vertical axis represents the signal amplitude. After the root raised cosine filter, the signal is phase modulated and up-converted to form a CE-DSM electrical signal, and its signal spectrum is shown in Figure 2 As shown in part (b) of .

[0030] In the generation system, the CE-DSM electrical signal is input into an arbitrary waveform generator (AWG), and the photon frequency doubling processing of the CE-DSM electrical signal is realized through a Mach-Zehnder modulator (MZM) and a photodiode module (PD), and the CE-DSM electrical signal is mixed and transmitted in a 15km SSMF and a 1m wireless link to form a millimeter wave electrical signal.

[0031] Specifically, the arbitrary waveform generator is used to convert the CE-DSM electrical signal into an analog waveform for subsequent transmission;

[0032] The external cavity laser module (ECL) has a line width of 500 Hz and a maximum emitted optical power of 13.7 dBm, and can generate a continuous wavelength (CW) laser wave, which serves as the optical input signal of the Mach-Zehnder modulator (MZM);

[0033] The structure of the Mach-Zehnder modulator (MZM) mainly includes two branch arms, a beam splitter and a beam combiner, which modulate the optical input signal and carry the analog signal generated by the arbitrary waveform generator (120) to the optical input signal to form an optical frequency doubling signal; specifically, the input optical signal is split into two beams by the beam splitter, which respectively constitute two different optical paths; the modulation signal is applied to the corresponding electrode to change the phase of the light in each arm; after passing through the two branch arms, the optical signal is recombined at the beam combiner. Due to the change in phase difference, the interference effect of the optical signal causes the change in the output light intensity, thereby realizing the modulation of the optical signal; the output signal spectrum of the Mach-Zehnder modulator at the lowest point (zero point) of the output light signal intensity is as follows Figure 2 As shown in part (c) of the diagram, the signal spectrum output at the highest bias point is Figure 2 As shown in part (d) of .

[0034] Standard single-mode fiber module (SSMF) uses high-performance single-mode fiber to support long-distance, high-bandwidth data transmission, with the advantages of low loss and low crosstalk;

[0035] The photodiode module (PD) is used to convert the optical frequency-doubled signal into a 2n-frequency millimeter-wave electrical signal so as to propagate to free space. At this time, the spectrum of the millimeter-wave electrical signal is as follows: Figure 2 As shown in part (e) of .

[0036] The present invention provides a specific embodiment, in which a millimeter wave electrical signal generating unit outputs a photon multi-frequency ultra-high-order vector millimeter wave signal at a transmitting end and transmits it, and performs offline digital signal processing on the transmitted millimeter wave signal at a receiving end to restore it to baseband information:

[0037] like Figure 1 As shown, the millimeter wave electrical signal generating unit outputs a signal, which is propagated into free space by the horn antenna module (HA) at the transmitting end.

[0038] In the embodiment, a signal receiving end is provided. After the receiving end receives the millimeter wave electrical signal through a 1m wireless link through an antenna module, the data signal analyzer at the receiving end digitizes the millimeter wave electrical signal; the digitized millimeter wave electrical signal is phase demodulated, DSM demodulated and OFDM demodulated in the data signal processing module (Rx DSP) at the receiving end to restore the baseband signal.

[0039] At the receiving end, the DSP processing of the digital signal processing module mainly includes three parts: phase demodulation, DSM demodulation and OFDM demodulation.

[0040] First, phase demodulation includes down-conversion and phase demodulator. During phase demodulation, the millimeter-wave electrical signal is phase-demodulated. After resampling and RRC filtering, the millimeter-wave electrical signal is restored to a DSM-NRZ signal using NRZ DSP technology. T / 2 spatial equalization is used to solve the dispersion and nonlinear problems caused by optical fiber and wireless transmission and photoelectric detector detection. When performing T / 2 spatial equalization, a 21-tap feedforward equalizer (FFE) and a 5-tap decision feedback equalizer (DFE) are used.

[0041] Secondly, after the NRZ signal is restored, DSM demodulation is performed through a low-pass filter (LPF) to remove the out-of-band quantization noise introduced by noise shaping and restore the original analog signal;

[0042] Finally, after downsampling, OFDM demodulation is performed, including synchronization, frequency domain equalization, fast Fourier transform (FFT), and 4096-QAM demapping, to restore the baseband signal. At this time, the signal spectrum is as follows: Figure 2 As shown in part (e) of the figure, it can be seen that the envelope of the CE-DSM signal remains constant after transmission, and photon frequency doubling and complex transmitter DSP do not cause intensity-dependent distortion to it.

[0043] Through this embodiment, a 4096QAM vector millimeter wave signal with high spectrum efficiency and simple structure is successfully generated, and the feasibility of combining phase modulation with DSM is verified based on the signal recovery at the receiving end.

[0044] The photon multi-frequency ultra-high-order vector millimeter wave signal generation system provided by the present invention can generate a 4096QAM ultra-high-order vector millimeter wave signal with high spectrum efficiency and simple structure, providing a high spectrum efficiency and high fidelity solution for the next generation mobile fronthaul (MFH) system.

[0045] The above disclosures are only several specific embodiments of the present invention; however, the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A photon multi-frequency ultra-high-order vector millimeter wave signal generation system, characterized in that: include: A digital signal processing module (110), an arbitrary waveform generator (120), a Mach-Zehnder modulator (140), an external cavity laser module (130), a standard single-mode optical fiber module (150), and a photodiode module (160); The digital signal processing module (110) is used to generate a CE-DSM electrical signal; The arbitrary waveform generator (120), Mach-Zehnder modulator (140) and photodiode module (160) are used to perform photon frequency doubling processing on the CE-DSM electrical signal to generate an optical frequency doubling signal, and to form a millimeter wave electrical signal after mixed transmission via a 15km SSMF and a 1m wireless link.

2. The production system according to claim 1, characterized in that The generating of the CE-DSM electrical signal comprises: Mapping a pseudo-random binary sequence into a complex-valued signal with 4096-order QAM; The baseband signal is generated by performing OFDM modulation through 1024-point inverse fast Fourier transform; Oversampling and one-bit DSM processing are performed on the baseband signal to convert it into a DSM-NRZ signal; The DSM-NRZ signal is up-sampled, root raised cosine filtered, phase modulated and up-converted to form a CE-DSM electrical signal.

3. The production system according to claim 1, characterized in that The arbitrary waveform generator (120) is used to generate an analog waveform for transmission according to the CE-DSM electrical signal; The external cavity laser module (130) is used to generate a continuous wavelength laser wave, and the laser wave is used as an optical input carrier signal of a Mach-Zehnder modulator (140); The Mach-Zehnder modulator (140) modulates the CE-DSM electrical signal into a corresponding optical input carrier signal and outputs an optical frequency-doubled signal.

4. The production system according to claim 1, characterized in that The optical frequency-doubled signal enters the photodiode module (160) after being transmitted through the standard single-mode optical fiber module (150); The photodiode module (160) converts the optical frequency-doubled signal into a 2n-fold millimeter-wave electrical signal.

5. The production system according to claim 1, characterized in that: The millimeter wave electrical signal can be restored to a CE-DSM electrical signal after being digitized, phase demodulated, DSM demodulated and OFDM demodulated.

6. The production system according to claim 2, characterized in that: The baseband signal is an OFDM signal including 0.5-Gbaud and 0.2-Gbaud; the DSM-NRZ signal is an NRZ signal including 4-GSa / s and 10-GSa / s.

7. The production system according to claim 3, characterized in that: The line width of the external cavity laser module (130) is 500 Hz, and the maximum emitted light power is 13.7 dBm.

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