Microwave Signal Generation Research Articles

Simultaneous Dual-Band Frequency-Agile Microwave Signal Generation With a Dual Loop Fourier Domain Mode Locked Optoelectronic Oscillator

Simultaneous Dual-Band Frequency-Agile Microwave Signal Generation With a Dual Loop Fourier Domain Mode Locked Optoelectronic Oscillator

Wide-Range Tunable Coherent Dual-Frequency Microwave Signal Generation With Low Spurious Components in Optoelectronic Oscillator

Wide-Range Tunable Coherent Dual-Frequency Microwave Signal Generation With Low Spurious Components in Optoelectronic Oscillator

Freely tunable phase-locked dual-frequency microwave signal generation from injection-locked broadband optoelectronic oscillator

We propose and experimentally demonstrate an injection-locked broadband optoelectronic oscillator (OEO) to generate freely tunable phase-locked dual-frequency microwave signals. When two single-tone signals inside and outside the passband of the electrical broadband bandpass filter (BPF) are, respectively, injected into the OEO, a phase-locked dual-frequency microwave signal with ultra-low near-end side-mode spurs can be generated from the OEO cavity. Therefore, one frequency of the output signal is equal to the frequency of the injected signal within the BPF, and the other frequency is equal to the sum frequency or the differential frequency of two injected signals. By changing the frequencies of two injected signals, two frequencies of the generated dual-frequency microwave signal can be arbitrarily tuned over the passband of the BPF. In our experiment, freelytu nable phase-locked dual-frequency microwave signals within the frequency range of 8∼12 GHz can be generated, where the side-mode suppression ratios (SMSRs) are more than 90 dB during the frequency tuning.

Quantum-dot spin-VCSELs subject to optical injection and feedback for flexible photonic millimeter wave generation

A novel microwave and millimeter wave signal generation system is proposed and numerically demonstrated using an optically pumped quantum dot (QD) spin-polarized vertical-cavity surface-emitting laser (spin-VCSEL) with optical injection. Different from previous optical injection systems, the signal frequency in our proposed system is dominated by both the birefringence-splitting and injection detuning frequencies. By flexibly tailoring the frequency detuning and birefringence rate, the frequency ranges from a few gigahertz to nearly 150 GHz can be obtained. To evaluate the signal quality, the dynamical behaviors of the proposed system and the characteristics of the generated millimeter wave signal are evaluated including the center frequency, power, linewidth, and phase variance. We further adopt the optical feedback structure to improve the microwave and millimeter wave signal performance. Results show that the signal linewidth and phase variance can be optimized by three to four orders of magnitude. Compared to the case of a solitary QD spin-VCSEL, this work shows more stable performance, particularly in the frequency range above 90 GHz. This scheme offers an approach for high-purity microwave and millimeter sources in wireless communication and radar systems.

An experimental alternative of microwave signal generation through an optical heterodyning technique using a multimode laser diode and a tunable DFB laser

An experimental alternative of microwave signal generation through an optical heterodyning technique using a multimode laser diode and a tunable DFB laser

Multi-gigabit X-band transmitter for satellite communication using the optical phase-locked loop.

Optical generation of microwave signals using photonic techniques offers benefits of frequency agility, ease of frequency scaling, and reduced hardware complexity. We demonstrate the generation and detection of QPSK modulated with symbol rates up to 5 GBaud at carrier frequencies of 8-12 GHz through optical heterodyning of two-phase-locked lasers. The received data is demodulated through appropriate post-processing to correct for the phase noise and IQ imbalance. The approach is scalable to mmWave and THz communication.

Theoretical analysis of the buried heterostructure laser for stable dual-wavelength generation

Stable dual-wavelength emission from a laser is desirable for microwave signal generation using the optical heterodyning method. As both optical wavelengths are generated from the same cavity, the phase noise of the generated microwave signal is minimized. In this work, we exploit the inherent birefringence in the buried heterostructure semiconductor laser to generate dual polarized modes. We carefully analyze the mode competition between various modes in the cavity and propose the desirable gain modification conditions for stable dual mode oscillations when the laser is operating near the threshold. We show that the required asymmetry in the gain for two stable modes can be obtained from the mode confinement factors and facet losses. We also show the applicability of our results to a homogeneously broadened multimode laser.

Generating Microwave Signals with Enhancive Amplitudes Using Superconductor Single Flux Quantum Pulses for Controlling Quantum Bit

AbstractIn this study, the on‐chip generation of microwave signals are proposed for controlling nearby quantum bits in a low‐temperature environment, utilizing superconducting logical and RF components. To achieve enhanced amplitude of the microwave, superconducting single flux quantum (SFQ) pulse pairs are employed, which can have either the same or reversal polarity, serving as the basic elements of the generator. The SFQ pulse pairs are then combined and wave‐shaped by using a microwave combining filter, which finally outputs desired microwave signals with narrow line‐width. The amplitude of the microwave signal correlates with the interval between two SFQ pulses in a pair and can be adjusted accordingly. To validate the proposal, test chips are fabricated and performed experiments. The experimental results confirm that the method using a reverse‐polarity pulse can maximize the output microwave amplitude and provide control of the initial phase of the output microwave. This improvement offers a superior alternative for generating microwaves using superconducting circuits to control quantum bits.

Non-isochronous exceptional point shift in coupled spin-torque nano-oscillators

This paper explores the nonlinear dynamics of mutually coupled spin-torque nano-oscillators and examines the relationship between non-isochronism and the appearance of exceptional points (EPs). We demonstrate that by manipulating the amplitudes of the driving force and the angles of the external bias magnetic field and spin-polarized current, it is possible to observe and fine-tune the position of EPs. Namely, EPs shift most significantly when the azimuth angle of the equilibrium state is approximately 90° and the system’s non-isochronism reaches its peak. The results of this investigation provide valuable insights for enhancing the performance of spintronic devices in applications such as microwave signal generation, spin-based computing, and sensing.

Experimental Study of Magnetron’s Power-Pulled Characteristic to Realize a Quasi-Dual-Frequency Microwave Output

This article presents experimental evidence demonstrating the feasibility of implementing a quasi-dual-frequency microwave signal generator using a 1 kW commercial magnetron. The injection-pulled magnetron may generate quasi-dual-frequency output with nearly identical amplitudes by injecting signal at specific powers and frequencies out of the Adler locking band. This generator offers the advantage of developing a large-power and tunable quasi-dual-frequency signal at low cost and with simple implementation. In the present study, a tunable quasi-dual-frequency signal with a frequency interval ranging from 0.48 MHz to 13.74 MHz is generated experimentally. Furthermore, the effects of anode voltage ripples on the dual-frequency outputs are experimentally investigated. An empirical relationship between the frequency interval and injection ratio is obtained and presented. In addition, neither the output power nor the efficiency of the magnetron in the dual-frequency mode decreases. This research is promising for improving microwave heating uniformity in large-scale industrial applications.

Phase-locked dual-frequency microwave signal generation in an optoelectronic oscillator based on frequency mixing mutual injection

An approach to generating stable phase-locked dual-frequency microwave signals is proposed and demonstrated based on a dual-passband optoelectronic oscillator (OEO). Mode gain competition is broken by employing frequency mixing mutual injection effect to realize phase locking between the two oscillation signals, which is achieved by applying a single-tone signal to a microwave mixer in the OEO cavity. In addition, a dual-loop configuration with balanced detection is utilized to ensure a high side mode suppression ratio (SMSR) and ultra-low phase noise, which also enhances the stability of the generated signal. In the experiment, a phase-locked dual-frequency microwave signal at 9.9982 GHz and 10.1155 GHz is generated by using the proposed OEO scheme. The SMSR and the phase noise are 75 dB and –141 dBc/Hz@10 kHz, respectively. Additionally, the Allan deviation of the generated signal is in the order of 10−11@1 s. These parameters are superior to those based on the same OEO but with a single-loop configuration, which are also compared in detail.

Integrated lithium niobate microwave photonic processing engine.

Integrated microwave photonics (MWP) is an intriguing technology for the generation, transmission and manipulation of microwave signals in chip-scale optical systems1,2. In particular, ultrafast processing of analogue signals in the optical domain with high fidelity and low latency could enable a variety of applications such as MWP filters3-5, microwave signal processing6-9 and image recognition10,11. An ideal integrated MWP processing platform should have both an efficient and high-speed electro-optic modulation block to faithfully perform microwave-optic conversion at low power and also a low-loss functional photonic network to implement various signal-processing tasks. Moreover, large-scale, low-cost manufacturability is required to monolithically integrate the two building blocks on the same chip. Here we demonstrate such an integrated MWP processing engine based on a 4 inch wafer-scale thin-film lithium niobate platform. It can perform multipurpose tasks with processing bandwidths of up to 67 GHz at complementary metal-oxide-semiconductor (CMOS)-compatible voltages. We achieve ultrafast analogue computation, namely temporal integration and differentiation, at sampling rates of up to 256 giga samples per second, and deploy these functions to showcase three proof-of-concept applications: solving ordinary differential equations, generating ultra-wideband signals and detecting edges in images. We further leverage the image edge detector to realize a photonic-assisted image segmentation model that can effectively outline the boundaries of melanoma lesion in medical diagnostic images. Our ultrafast lithium niobate MWP engine could provide compact, low-latency and cost-effective solutions for future wireless communications, high-resolution radar and photonic artificial intelligence.

Parity time symmetry all-optical microwave oscillator using a polarization dependent Sagnac loop

An all-optical microwave oscillator based on parity-time symmetry was proposed and experimentally demonstrated. It mainly consists of a big feedback loop, an active small loop and a polarization-dependent Sagnac loop. The microwave seed signal originates from the beating between the continuous wave and the Stokes wave. The function of microwave envelope detection and feedback modulation are implemented through cross gain modulation of two semiconductor optical amplifiers. By employing the parity time symmetry loops and the Vernier effect, the single mode selectivity capability of the oscillator has been enhanced, and a single mode microwave signal with high quality can be generated. In the experiment, a highly quality microwave signal with a frequency of 10.71 GHz was generated. The single side band phase noise can reach −94.1 dBc/Hz@10 kHz and the side mode suppression ratio of the generated microwave signal reaches 41 dB. Compared to the previously reported all-photonic microwave oscillator, the single side band phase noise is improved by 7 dB at a frequency offset of 10 kHz, and by 20 dB at a frequency offset of 100 Hz. The results indicate that our proposed scheme significantly improves the quality of the generated microwave signals.

Low-phase-noise microwave generation with a free-running dual-pumped Si3N4 soliton microcomb.

Microwave signals can be generated by photodetecting the repetition frequencies of the soliton microcombs. In comparison to other methods, the dual-pumped method allows for the stable generation of the soliton microcombs even with resonators having lower Q-factors. However, introducing an additional pump laser may affect the phase noise of the generated microwave signals when using these dual-pumped soliton microcombs. Here, we investigate the factors that could influence the phase noise of microwave signals generated with dual-pumped soliton microcombs, including the polarization, amplitude noise, and phase noise of the two pumps. We demonstrate a 25.25 (12.63) GHz microwave with phase noise reaching -112(-118) dBc/Hz at a 10 kHz offset frequency, surpassing the performance of previous reports on microwave generation using free-running Si3N4 soliton microcombs, even those generated with higher Q microresonators. We analyze the noise floor of the generated microwave signals and establish a phase noise simulation model to study the limiting factors in our system. Our work highlights the potential of generating low-phase-noise microwave signals using free-running dual-pumped soliton microcombs.

Generation of Microwave Frequency Comb, Chaotic, and Single-frequency Microwave Signal in a Short-cavity-based Optoelectronic Oscillator

Generation of Microwave Frequency Comb, Chaotic, and Single-frequency Microwave Signal in a Short-cavity-based Optoelectronic Oscillator

Photonic Generation of Multi-Featured Chirp Microwave Signal With a Phase Tunable Mechanism for Chirp Rate Variation

Photonic Generation of Multi-Featured Chirp Microwave Signal With a Phase Tunable Mechanism for Chirp Rate Variation

Progress in Photonics-Based Linear Frequency-Modulated Microwave Signal Generation Technology (Invited)

Progress in Photonics-Based Linear Frequency-Modulated Microwave Signal Generation Technology (Invited)

Photonic generation of dual-mode multi-format chirp microwave signals.

In this paper, we present a novel, to the best of our knowledge, photonic scheme for the generation of dual-mode multi-format chirp microwave signals, utilizing a dual-drive dual-parallel Mach-Zehnder modulator (DD-DPMZM). By inputting a single-chirp signal and controlling the input binary sequences, the proposed method can generate up-, down-, dual-, or triangular-chirp signals in both pulse and continuous-wave modes. Moreover, the duty cycle of the generated chirp signals in the pulse mode can be easily adjusted by manipulating the injected binary sequences. The compact structure of the proposed scheme eliminates the need for polarization control in signal switching and avoids the use of any optical filter. Experimental verification confirms the feasibility of our approach, while also pointing towards its promising applications in multi-functional radar systems.

The photodetection of ultrashort optical pulse trains for low noise microwave signal generation.

Electrical signals derived from optical sources have achieved record-low levels of phase noise, and have demonstrated the highest frequency stability yet achieved in the microwave domain. Attaining such ultrastable phase and frequency performance requires high-fidelity optical-to-electrical conversion, typically performed via a high-speed photodiode. This paper reviews characteristics of the direct photodetection of optical pulses for the intent of generating high power, low phase noise microwave signals from optical sources. The two most popular types of photodiode detectors used for low noise microwave generation are discussed in terms of electrical pulse characteristics, achievable microwave power, and photodetector nonlinearities. Noise sources inherent to photodetection, such as shot noise, flicker noise, and photocarrier scattering are reviewed, and their impact on microwave phase fidelity is discussed. General guidelines for attaining the lowest noise possible from photodetection that balances power saturation, optical amplification, and amplitude-to-phase conversion, are also presented.

Continuous optical generation of microwave signals for fountain clocks.

For the optical generation of ultrastable microwave signals for fountain clocks, we developed a setup based on a cavity stabilized laser and a commercial frequency comb. The robust system, in operation since 2020, is locked to a 100MHz output frequency of a hydrogen maser and provides an ultrastable 9.6GHz signal for the interrogation of atoms in two cesium fountain clocks, acting as primary frequency standards. Measurements reveal that the system provides a phase noise level that enables quantum projection noise limited fountain frequency instabilities at the low 10-14(τ/s)-1/2 level. At the same time, it offers largely maintenance-free operation.