Millimeter-wave Signal Generation Research Articles

Photonic-assisted high-order vector millimeter-wave signal generation enabled by DSM.

We propose an optical dual-single-sideband (dual-SSB) modulated 16384-quadrature amplitude modulation (QAM) photonic vector millimeter-wave (mm-wave) signal generation scheme based on delta-sigma modulation (DSM). With the aid of the DSM, the severe nonlinear distortion of envelope detection for high-order QAM modulation signals in wireless communication can be effectively resolved. For the validation of our proposed scheme, we experimentally demonstrate the generation of a 40 GHz 16384-QAM orthogonal frequency division multiplexing (OFDM) photonic vector mm-wave signal and transmission over a 25-km standard single-mode fiber (SSMF), and a 1-m wireless link with the bit error ratio (BER) reaches the hard-decision forward-error-correction (HD-FEC) threshold of 3.8 × 10-3.

Dual vector millimeter-wave signal generation based on optical carrier suppression modulation and direct detection with one photodetector.

We propose a novel, to the best of our knowledge, scheme for dual vector millimeter-wave (mm-wave) signal generation and transmission, based on optical carrier suppression (OCS) modulation, precoding, and direct detection by a single-ended photodiode (PD). At the transmitter side, two independent vector radio frequency (RF) signals with precoding, generated via digital signal processing (DSP), are used to drive an in-phase/quadrature (I/Q) modulator operating at the optical OCS modulation mode to simultaneously generate two independent frequency-doubling optical vector mm-wave signals, which can reduce the bandwidth requirement of transmitter's components and enhance spectral efficiency. With the aid of the single-ended PD and subsequent DSP at the receiver side, two independent frequency-doubling vector mm-wave signals can be separated and demodulated without data error. Based on our proposed scheme, we experimentally demonstrate the generation, transmission, and detection of 2-Gbaud 30-GHz quadrature-phase-shift-keying (QPSK) and 2-Gbaud 46-GHz QPSK signals over 10-km single-mode fiber-28 (SMF-28) and 1-m wireless transmission. The results indicate that the bit-error ratio (BER) of the dual vector mm-wave signals can each reach the hard-decision forward-error-correction (HD-FEC) threshold of 3.8 × 10-3.

Two-stage look-up-table-based 16QAM vector millimeter-wave signal generation and reception.

We propose a two-stage look-up table (LUT) scheme for a photonic 16 quadrature-amplitude-modulation (QAM) millimeter-wave (MMW) communication system. The first-stage LUT is used at the transmitter, which can eliminate complex computational processes and adaptively adjust the precoded amplitude values to achieve optimal performance without being affected by half-wave voltage variations. We have completed a signal transmission below the hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10-3 at the baud rate of 2/4 GBaud for weak turbulence and 2 GBaud for medium turbulence free-space optics (FSO) channel transmission. The second-stage LUT is used for post-compensation at the receiver as a nonlinear scheme that records the average pattern-related distortion of the channel and mitigates transmission impairment through nonlinear post-compensation. With the help of the second-stage LUT, the sensitivity of the optical receiver is improved by 0.15 dB at a baud rate of 2 GBaud for medium turbulence FSO channel transmission. As the baud rate increases to 4 GBaud, the system's bit error ratio (BER) can reach the soft-decision forward error correction (SD-FEC) threshold of 4.2 × 10-2 only after applying the second-stage LUT.

Photonic frequency-multiplied 4096-QAM vector millimeter-wave signal generation using CE-DSM

Photonic frequency-multiplied 4096-QAM vector millimeter-wave signal generation using CE-DSM

Spectral-Efficient Frequency-Division Photonic Millimeter-Wave Integrated Sensing and Communication System Using Improved Sparse LFM Sub-Bands Fusion

Scheduling radar and communication functions in a frequency-division multiplexing (FDM) fashion is a classic solution to achieve mutual-interference-free integrated sensing and communication (ISAC) system. However, it is haunted by poor spectral efficiency (SE) in comparison to the spectrum-sharing scheme. In this paper, we propose a novel photonics millimeter-wave ISAC system reaping the FDM scheme while offering inspirations for significantly enhancing SE using super-resolution techniques. Using the coherent fusion processing (CFP) of sparse sub-band linear frequency modulated (LFM) radar signals, a small fraction of the total bandwidth can enable a full-band-equivalent radar range resolution and more spectrum resources can be allocated for communications, leading to an ultrahigh SE for ISAC system. Moreover, an improved sparse sub-band fusion algorithm is developed based on particle swarm optimization to enhance the accuracy of synthesized radar range profiles. In experiments, a 60-GHz super-resolution FDM ISAC system using photonics-assisted millimeter-wave signal generation and dual-parallel coherent de-chirping processing is established, wherein the idle spectrum between two widely-spaced LFM sub-bands is loaded with broadband orthogonal frequency division multiplexing (OFDM) communication signals. Our system can simultaneously achieve up to 18-Gbit/s communication data rate and a radar range resolution as high as 2.14 cm, by exploring the globally unlicensed 7-GHz spectrum around 60-GHz with 4.5-GHz communication and 2-GHz radar bandwidths. In addition, a 0.97-cm radar range resolution corresponding to 16-GHz equivalent bandwidth (EB) is experimentally obtained by using two 1.5-GHz LFM sub-bands. This renders only ∼9.4% EB loss (3 GHz/32 GHz), without significant performance tradeoff between sensing and communications.

A simple filter-less QPSK modulated vector millimeter-wave signal generation with frequency quadrupling only enabled by a DP-PolM

A simple filter-less QPSK modulated vector millimeter-wave signal generation with frequency quadrupling only enabled by a DP-PolM

Q-Band MMW Transmission Enabled by Joint Probabilistic Shaping and Precoding With MZM-Based OCS Modulation

In this letter, we propose a novel and straightforward scheme for Q-band (33-50GHz) millimeter-wave signal generation enabled by a Mach-Zehnder modulator (MZM)-based joint algorithm, which combines probabilistic shaping (PS) and precoding technology, to enhance the anti-interference ability of the transmission system. Based on the proposed scheme, we experimentally demonstrate the generation and transmission of 1.4-Gbaud 46-GHz PS-16-quadrature-amplitude-modulation (PS-16QAM) vector signals, showcasing improved bit-error-ratio (BER) in both standard single-mode fiber (SSMF) and wireless transmission cases. The proposed scheme exhibits a clear advantage in terms of nonlinear interference suppression and satisfies the hard-decision forward-error-correction (HD-FEC) threshold with a BER of 3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> in radio-over-fiber (RoF) systems.

Scheme to eliminate the time shift of code edges based on the optimal transmission point of a DP-MZM.

To eliminate the time shift of code edges on a single-sideband (SSB) modulation signal transmission in a radio-over-fiber (RoF) system, a new, to the best of our knowledge, SSB modulation scheme based on an optimal transmission point for a double-parallel Mach-Zehnder modulator (DP-MZM) is proposed. The scheme is based on DP-MZM to realize the separation of the carrier and the +1st-order sideband at the optimal transmission point, and the baseband signal modulates the 2.5Gb/s data signal to the +1st-order sideband of the SSB signal; then, the carrier and the +1st-order sideband are transmitted with a carrier-to-sideband ratio of 0dB. Theoretical analysis shows that compared to the traditional SSB-modulated optical millimeter-wave signal generation scheme this scheme completely solves the problem of the time shift of code edges caused by dispersion. The simulation results show that the improved SSB modulation scheme has a Q factor of 23.362, the minimum bit error rate is 4.207×10-127 at 73.453km, and the eye diagram is still very clear. Under the premise of meeting the basic requirements of communications, the maximum communications distance can reach 135km, which is 270% of the transmission distance of a traditional SSB modulation model.Thus, the system performance has been greatly improved.

Multifrequency Vector Mm-Wave Signal Generation with No Optical Filtering Based on One Dual-Arm MZM with Phase Factor Optimization

In order to reduce the number of devices in and cost of a multifrequency vector millimeter-wave (mm-wave) signal generation system, we propose a novel scheme for multifrequency vector mm-wave signal generation based on one dual-arm Mach-Zehnder modulator (MZM) without optical filtering. This scheme utilizes the carrier suppression modulation of a single modulator, without the need for optical filtering and combines precoding technology to generate high-frequency QPSK and 16 QAM mm-wave signals. The transmitter is applied with precoding technology to make the frequency multiplying vector mm-wave signal display regular vector modulation at the receiver, and the system is optimized with a phase factor to ensure that the phase distribution of QPSK signal at the receiver is symmetrical. We demonstrated the generation of 4-Gbaud 76 GHz QPSK and 16 QAM vector mm-wave signals through simulation. The simulation results show that, at a fiber transmission distance of 12 km, when the launched optical power of the PD is greater than −20.535 dBm, the bit error ratio (BER) of the QPSK signal is lower than the hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10−3. At a fiber transmission distance of 10 km, when the launched optical power of the PD is greater than −18.637 dBm, the BER of 16 QAM signal is also lower than 3.8 × 10−3.

Multi-frequency 5G NR millimeter-wave signal generation over analog RoF link using optical frequency combs

Optical heterodyne analog radio-over-fiber (A-RoF) links can provide a cost-effective and spectrally efficient solution for the generation and distribution of millimeter-wave/Terahertz (mm-wave/THz) carriers for the next-generation wireless systems. The use of an optical frequency comb (OFC) source in such a system can facilitate carrier generation free from frequency fluctuation. However, decorrelation between tones, due to path length difference, can lead to phase noise on the generated mm-wave carrier — limiting the performance of low subcarrier spacing multi-carrier signals specified in the 5G standard. In this work, we analyze the effect of comb tones decorrelation due to path length difference on the performance of 5G compatible 244 kHz subcarrier spacing 59 GHz OFDM signal over an optical heterodyne A-RoF link using a gain switched laser (GSL) OFC source. Furthermore, we demonstrate the ability of the OFC-based A-RoF optical/mm-wave system to support flexible and interoperable mm-wave functionality through signal generation at 27 GHz, 43 GHz and 59 GHz using different pairs of GSL OFC tones for remote heterodyning. The capability of multi-frequency 5G NR compatible mm-wave signal generation and potential for photonic integration make the demonstrated GSL OFC based optical heterodyne A-RoF system a suitable candidate for deployment in the next generation wireless systems.

Photonic filter-free adjustable frequency sextupling scheme for V-band vector mm-wave signal generation based on a DP-MZM with precoding

In this work, a new filter-free adjustable scheme for the generation of frequency sextupling vector millimeter-wave (mm-wave) signal without optical filter which can widen the adjustable frequency range. In the process of vector mm-wave frequency multiplication, the frequency is linearly multiplication and the phase would be simultaneous linearly multiplication, which makes the information carried by the phase distorted. Phase precoding is employed to eliminate constellation overlapping caused by phase multiplication. Simulations are done to generate V-band 60 GHz sextupling phase shift keying (QPSK) modulated vector mm-wave signals using a 10 GHz radio frequency source and the BER performance is analyzed in detail. The results show that BER of the generated 5/10-Gbit/s vector millimeter-wave signal is below 3.8×10−3, when the input optical power for into photo-detector is higher than −20.67 dBm.

SNR-enhanced and high-order frequency multiplied 64-QAM millimeter-wave signal generation enabled by MZM-based angle modulation.

We propose and experimentally demonstrate a novel scheme to generate ultrahigh-order frequency multiplied millimeter-wave (mm-wave) signals with high fidelity enabled by angle modulation (ANG-M). The constant envelope (CE) characteristic of the ANG-M signal makes it possible to avoid nonlinear distortion induced by photonic frequency multiplication. In addition, the theoretical formula and the simulation results prove that the modulation index (MI) of the ANG-M signal increases along with frequency multiplication, so as to improve the signal-to-noise ratio (SNR) of the frequency-multiplied signal. In the experiment, we confirm the SNR of the 4-fold signal is enhanced by 2.1 dB approximately for the increased MI compared to the 2-fold signal. Finally, a 6-Gb/s 64-QAM signal with a carrier frequency of 30 GHz is generated and transmitted over 25-km standard single-mode fiber (SSMF) using only a 3-GHz radio frequency signal and 10-GHz bandwidth Mach-Zehnder modulator. To the best of our knowledge, it is the first time that a 10-fold frequency-multiplied 64-QAM signal with high fidelity is generated. The results prove that the proposed method will be a potential solution for low-cost mm-wave signal generation in future 6G communication.

Enabling WiGig Communications Using Quantum-Dash Laser Source Under Smoky Weather Conditions

Wireless Gigabit (WiGig) is a recent wireless local area network that operates at the 60-GHz band and supports a transmission data rate of up to 20 Gbps. This paper demonstrates the generation of a V-band millimeter-wave (mmWave) signal using a new class of InAs/InP quantum-dash laser-based comb source operating in the L-band region. A 62.5-GHz mmWave signal is generated with electrical linewidth and phase noise characterization of 1 kHz and −65 dBc/Hz, respectively. Then, the transmission of the 6-Gbaud quadrature phase-shift keying (12 Gbps) signal is experimentally achieved over a hybrid radio-over-fiber (RoF) and radio-over-free-space (RoFSO) architecture comprising an 11.6-km single-mode fiber (SMF), 6-m FSO, and up to 2-m wireless link. Moreover, we also report this WiGig signal's transmission performance in terms of the measured bit error rate and error vector magnitude under various density smoke FSO channels, exhibiting a visibility range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 100 m for error-free transmission.

Photonic generation of millimeter-wave and multi-waveform signals based on external modulation and polarization control.

An approach for photonic generation of multi-function microwave/pulse signals has been proposed and verified, which is capable of achieving Nyquist/triangular pulse signals and frequency quadrupling/12-tupling microwave signals. Based on optical carrier suppressed modulation in a dual-parallel Mach-Zehnder modulator, a four-line optical frequency comb and a Nyquist pulse are generated. Subsequently, polarization controlling using an optical interleaver and a linear polarizer is conducted to manipulate spectra, after which a pulse signal with triangular shape and a microwave signal with high-frequency multiplication factor are generated. By applying a 10-GHz RF driving signal, a Nyquist pulse and a full-duty-cycle triangular pulse with repetition frequency of 40GHz, and 40-/120-GHz millimeter-wave signals can be obtained. This proposal provides the potential of higher-frequency multi-waveform and millimeter-wave signals generator for an all-optical network.

A Continuously Tunable and Filter-Less QPSK Modulated Millimeter-Wave Signal Generation with Frequency Quadrupling Just Based on an MZM

In this paper, we propose a new frequency quadrupling scheme to generate a quadrature phase shift keying (QPSK) modulated vector millimeter-wave signal, in which an optical filter is not necessary. To eliminate constellation overlapping of the generated vector millimeter-wave signal caused by phase multiplication in the process of frequency multiplication, a precoding assisted technique is adopted. The principle and feasibility of the proposed scheme is deduced by a detailed mathematical formula. Simulations are carried out to generate 40 GHz QPSK modulated vector millimeter-wave signals using a 10 GHz radio frequency source and the BER performance is analyzed in detail. The results show that BER of the generated 5/10-Gbaud vector millimeter-wave signal is below 3.8×10-3, when the input optical power for into photo-detector is higher than −20.67 dBm.

Injection-Locking Techniques for CMOS Millimeter-Wave and Terahertz Signal Generation

This brief presents a comprehensive tutorial on the recent advances of injection-locking techniques used for millimeter-wave (mm-Wave) and terahertz (THz) signal generation systems. Injection locking has the potential to significantly improve the system performance in terms of low phase noise and low power consumption. The focus will be on the state-of-the-art injection-locking techniques to effectively widen the locking range and reduce the phase noise, including injection-locked frequency dividers (ILFDs), injection-locked frequency multipliers (ILFMs), and sub-harmonic injection-locked phase-locked loops (IL-PLLs).

Photonics aided vector millimeter-wave signal generation without DAC at W-band

In this paper, a novel scheme to generate a high-order QAM W-band mm-wave signal is proposed, which avoids the usage of expensive and power hungry digital-to-analog converter (DAC). We numerically simulate m2-QAM mm-wave signal generation and investigate the influences of phase shift and SNR on the performance of the generated W-band signals. The numerical result shows that both SNR and the modulation order m are important factors which decide the quality of generated vector mm-wave signals. Besides, we experimentally demonstrate 10 Gb/s @80 GHz QPSK signal generation based on photonic-aided frequency quadrupled generation principle, which handles the phase noise issue effectively. Moreover, 10 Gb/s @80 GHz QPSK signal transmission over 1-km DSF and 1-m wireless link is also achieved. The experiment results indicate that BER can achieve 7% hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10−3 when the optical power is above −5 dBm. Due to avoiding a bandwidth limited DAC, our proposed W-band QAM vector mm-wave signal generation with a simple structure is promising for the future high-speed 5G ROF-based communication application and beyond.

A Filterless Generation of Optical Millimeter Wave Signal Based on Frequency 16-Tupling Using Cascaded Polarization Modulators

Millimeter wave (MMW) frequencies are becoming vital as they bolster a large number of applications requiring higher data rates. In this paper, we have demonstrated a frequency multiplication technique based on external modulation for a 160 GHz MMW signal generation. The proposed scheme which uses a four-stage cascaded structure of polarization modulators proves to be a lucrative solution since the selected modulation index of 2.826 is phenomenally low. A precise choice of phase shifts between the cascaded stages ensures two eighth-order peaks spaced 160 GHz apart. This technique renders Radio Frequency Spurious Suppression Ratio and Optical Sideband Suppression Ratio of 45 and 65 dB, respectively. Simulation results are verified from a mathematical standpoint. The requirement of a Radio Frequency Local Oscillator with a higher frequency has been eliminated by a higher value of frequency multiplication factor.

Optical Injection Locking for Generation of Tunable Low-Noise Millimeter Wave and THz Signals

This article presents the experimental demonstration of synchronization of two integrated semiconductor distributed Bragg reflector lasers, fabricated with a generic multiproject wafer platform, by means of injection locking. Substantial linewidth reduction and frequency stabilization of the lasers were shown during locking of the lasers to an optical frequency comb. Phase noise was measured for different injected powers and different laser cavities. For a generation of millimeter-wave signals up to 80 GHz, two lasers were simultaneously locked to the comb. Fine-tuning was performed by tuning the repetition rate of the comb and coarse-tuning was carried out by switching to another comb line. A suppression ratio of 37 dB was achieved for unwanted comb lines. The achieved signal purity, phase noise, and suppression of unwanted components demonstrate the viability of injection locking for the generation of high-quality signals at sub-THz and THz frequencies and with substantial tunability.

Large Tunable 16-Tupled Millimeter Wave Generation Utilizing Optical Carrier Suppression With a Tunable Sideband Suppression Ratio

Coping up with the rising bandwidth demands for 5G ultra-high speed applications, utilizing millimeter (MM) wave spectrum for data transmission over the radio over a fiber-based system is the ideal approach. In this study, a highly conversant and spectrally pure photonic generation of a 16-tupled MM wave signal using a series-connected DD-MZM with a lower modulation index, a splitting ratio, and a wider tunable range is presented. A 160-GHz MM wave is generated through a double sideband optical carrier suppression technique having an optical sideband suppression ratio (OSSR) of 69 dB and a radio frequency sideband suppression ratio (RSSR) of 40 dB. However, the OSSR and the RSSR are tunable with values greater than 15 dB when the modulation index (M.I.) varies from 2.778 to 2.873, ±8° phase drift, and a 15-dB enhancement in the OSSR with a wider nonideal parameter variation range giving acceptable performance can be seen in the model as compared with previous research works.