Generation Of Microwave Pulses Research Articles

Self-excited Microwave Pulse Generation Based on Self-mode-locking Optoelectronic Oscillator

Self-excited Microwave Pulse Generation Based on Self-mode-locking Optoelectronic Oscillator

Phase-coded coherent microwave pulse generation based on an actively mode-locked optoelectronic parametric oscillator.

An approach for generating phase-coded coherent microwave pulse trains at high frequencies is proposed and demonstrated based on an actively mode-locked optoelectronic parametric oscillator (AML-OEPO), where an electrical mixer is inserted into the cavity of an optoelectronic oscillator (OEO) to achieve both mode locking and parameter oscillation. The driving signal applied to the mixer is a low-frequency sinusoidal signal with voltage polarity coding, where the frequency is the same as the free spectral range (FSR) of the OEO cavity, and the duration of each voltage polarity coding bit is identical to the loop delay. As a result, phase-coded coherent microwave pulse trains can be generated, where the pulse interval is equal to the loop delay due to the active mode locking effect, and the phase coding period is equal to a multiple integer of the loop delay due to parameter oscillation. The enhancement of the signal period and the highly coherent characteristic are beneficial for breaking the contradiction between unambiguous detection range and ranging resolution in pulse radars. In the experiment, phase-coded microwave pulse trains with either 13-bit barker codes or 7-bit M codes are generated at 15.026 GHz. The autocorrelation calculation result of the phase-coded microwave pulse train with 13-bit barker codes shows a high peak-to-sidelobe ratio, verifying high coherence.

A cryogenic on-chip microwave pulse generator for large-scale superconducting quantum computing

For superconducting quantum processors, microwave signals are delivered to each qubit from room-temperature electronics to the cryogenic environment through coaxial cables. Limited by the heat load of cabling and the massive cost of electronics, such an architecture is not viable for millions of qubits required for fault-tolerant quantum computing. Monolithic integration of the control electronics and the qubits provides a promising solution, which, however, requires a coherent cryogenic microwave pulse generator that is compatible with superconducting quantum circuits. Here, we report such a signal source driven by digital-like signals, generating pulsed microwave emission with well-controlled phase, intensity, and frequency directly at millikelvin temperatures. We showcase high-fidelity readout of superconducting qubits with the microwave pulse generator. The device demonstrated here has a small footprint, negligible heat load, great flexibility to operate, and is fully compatible with today’s superconducting quantum circuits, thus providing an enabling technology for large-scale superconducting quantum computers.

Generation of powerful short microwave pulses using an amplifier on GaN transistors

Generation of powerful short microwave pulses using an amplifier on GaN transistors

Dual-band tunable microwave pulse signals generation based on a time domain mode locked optoelectronic oscillator

We propose and experimentally demonstrate a dual-band tunable microwave pulse signals generation method based on a time domain mode locked optoelectronic oscillator (TDML-OEO). The dual-band radio frequency (RF) combs are generated via injecting two single-tone signals and a low frequency signal. The two single-tone signals are injected to optimize the aimed center frequencies gain, while the low frequency signal is used to accomplish the multi-mode oscillation mode locking process. Furthermore, the dual-band RF combs with variable repetition rates of 3.69 MHz, 9.22 MHz, and 18.45 MHz are obtained with an over 72 dB ultra-high suppression of super mode noise as the TDML-OEO operates in the varied harmonic multiples mode locking state. Besides, by adjusting the amplitude and central frequency of the two injected local oscillator signals (LOs), a controllable output power and frequency tunability ranged from 11.1 GHz to 13.8 GHz are achieved for the generated dual-band RF combs. The proposed dual-band tunable microwave pulse generation method has great potential applications in multiband radars and electronic warfare.© 2023 Optica Publishing Group under the terms of the Optica Publishing Group Open Access Publishing Agreement.

Pulse-Density-Modulated Microwave Generator Using Single-Flux-Quantum Circuits for Controlling Qubits

Superconducting qubits are generally controlled by irradiation with microwave pulses. We propose a 5-GHz-range microwave pulse generator based on pulse density modulation for controlling qubits using single-flux-quantum (SFQ) circuits. The proposed microwave pulse generator comprises a 100-GHz circular shift register and a band-pass filter (BPF). In this study, we investigated the relationship between the target envelope of the microwave amplitude and the SFQ pulse density based on the transfer function for the BPF and the frequency spectrum of an SFQ pulse. We implemented a 64-bit circular shift register and demonstrated its operation up to 68 GHz.

Amplitude-controllable microwave pulse generator using single-flux-quantum pulse pairs for qubit control

To achieve large-scale quantum processors, cryogenic quantum-bit (qubit) interface circuits that can control qubits inside a dilution refrigerator are indispensable. Superconducting single-flux quantum (SFQ) circuits are a promising building block for qubit interface circuits because SFQ circuits can operate with high clock frequencies and low power dissipation. In the present study, we developed an SFQ-based qubit interface circuit that we refer to as a pulse-pair microwave pulse generator (PP-MPG). The PP-MPG can generate microwave pulses for qubit control, with the microwave amplitude controlled based on the delay between paired SFQ pulses. By finely adjusting the delay with delay controlling circuits, the microwave amplitude can be controlled over a wide range. We fabricated a PP-MPG chip and tested it at 4.2 K, showing that the microwave amplitude can be controlled over a range of approximately 30 dB. Our results show that the PP-MPG has the potential for use in future large-scale quantum processors.

Photonic Generation of Background-Free Phase-Coded Microwave Pulses with Elimination of Power Fading

We report a novel photonic scheme to generate background-free phase-coded microwave pulses with elimination of power fading by cascading a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) and a polarization modulator (PolM). The DP-DPMZM is driven by a radio frequency (RF) signal to generate two first-order optical sidebands with an orthogonal polarization state, while the PolM is driven by a three-level electrical coding signal. By properly adjusting the polarization state, a series of background-free frequency-doubled phase-coded microwave pulses can be generated after optical-to-electrical conversion. Benefiting from the carrier-suppressed single-sideband (CS-SSB) modulation, the proposed signal generator can suppress the chromatic-dispersion-induced power-fading effect, which has excellent potential for long-distance fiber transmission. In addition, the system can directly generate phase-coded microwave signals in pulse mode by truncating continuous wave (CW) microwave signals. Moreover, the microwave signal generator has wideband tunability since no optical filter is involved in our scheme. The proposed method was theoretically analyzed and experimentally verified. Phase-coded microwave pulses centered at 14 GHz and 19.2 GHz with a bit rate of 0.5 Gb/s were successfully generated.

Tunable Microwave Pulse Generation Based on an Actively Mode-Locked Optoelectronic Oscillator

A tunable microwave-pulse-generation scheme is proposed and demonstrated by employing an actively mode-locked optoelectronic oscillator (OEO) based on a microwave photonic filter (MPF). The MPF mainly consists of a phase-shifted fiber Bragg grating (PS-FBG) and a phase modulator. The microwave pulse trains with variable repetition rates are achieved by injecting an external signal, of which the frequencies are equal to an integer multiple of the free spectrum range (FSR) of the OEO. The multi-mode oscillation mechanism is discussed in detail theoretically and experimentally. A microwave pulse train with a central frequency of 9.25 GHz and repetition rate of 1.68 MHz is demonstrated by setting the injecting signal frequency to be the same with the FSR of the OEO. A tunable center frequency of the microwave pulses from 5.47 GHz to 18.91 GHz can be easily generated by tuning the laser frequency benefit from adopting the MPF. Furthermore, the microwave pulses with different pulse periods of 297.62 ns, 198.69 ns, and 148.81 ns are also realized by harmonic mode-locking. The proposed tunable microwave-pulse-generation method has potential applications in the pulse Doppler radar and communications.

Tunable Microwave Pulse Generation Based on a Time-Domain Mode Locked Optoelectronic Oscillator

A tunable microwave pulse generator is proposed and demonstrated. In this study, a time-domain mode locked optoelectronic oscillator (OEO) is realized by utilizing a dual-parallel Mach-Zehnder modulator (DPMZM). One branch of the DPMZM is modulated by the feedback signal and another branch is modulated by an inject signal. When the frequency of the injected signal is equal to an integer multiple of the oscillation mode space, the time-domain mode locking is achieved in the OEO loop and the microwave pulse trains are generated. In the experiment, the phase noise of the generated signal is −93 dBc/Hz, the frequency range of the generated signal is 6–12 GHz, the time duration of the generated microwave pulse can be adjusted from 620 ns to 2970 ns, and the repetition rate of the generated microwave pulse can be set to 185.1 kHz, 370.2 kHz and 555.3 kHz.

Compact RSFQ microwave pulse generator based on an integrated RF module for controlling superconducting qubits

An on-chip superconducting microwave pulse generator (MPG), incorporating rapid single-flux-quantum (RSFQ) logic gates and passive radio frequency (RF) components, is an energy-efficient solution for controlling superconducting quantum bits (qubits). Traditional RSFQ MPG designs, however, suffer from a large footprint as multiple RF components (including impedance matching networks, filters, etc.) are separately implemented one after another. In this Letter, we propose a compact on-chip MPG by introducing an integrated RF module. Using a generalized filter synthesis technique, the integrated RF module combines the functionalities of impedance matching and bandpass filtering as a single inductor-capacitor (LC) lumped network. Plenty of circuit elements can, thus, be saved, and the resultant LC network is applicable to both real and complex terminal impedance cases. For validation, a superconducting MPG adopting a fourth-order, 5 GHz centered, 100 MHz bandwidth integrated RF module is designed and fabricated, whose correct operations are confirmed through both simulation and measurement. These results raise the availability of controlling large-scale quantum systems by low-power superconductor technology in the future.

Photonic Generation of Multi-Band Phase-Coded Microwave Pulses by Polarization Manipulation of Optical Signals

We report a photonic approach to generate multi-band phase-coded microwave pulses based on polarization manipulation of optical signals using a dual-polarization dual-parallel Mach-Zehnder modulator (DPol-DPMZM). Two radio frequency signals are sent to the DPol-DPMZM to realize carrier-suppressed double sideband (CS-DSB) modulation. A high-speed polarization modulator, driven by a three-level electrical coding signal <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> ), is used to switch the modulation states of optical signals. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> ) = 1 or -1, the phases of the generated microwave signals are 0 or π. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> ) = 0, a carrier-suppressed single sideband (CS-SSB) modulation is realized and there is no desired microwave signal recovered after photodetection. In this way, multi-band phase-coded microwave pluses are generated. The π phase jump of the generated phase-coded pulses is determined by the polarity of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> ) instead of its amplitude, which is low power consuming and convenient. Compared to most existing photonic schemes that generate multi-band phase-coded signals in continuous wave (CW) mode, our scheme can directly generate multi-band phase-coded signal in pulse mode, which is pretty suitable for multi-band radar system application.

Ultrastable microwave and soliton-pulse generation from fibre-photonic-stabilized microcombs

The ability to generate lower-noise microwaves has greatly advanced high-speed, high-precision scientific and engineering fields. Microcombs have high potential for generating such low-noise microwaves from chip-scale devices. To realize an ultralow-noise performance over a wider Fourier frequency range and longer time scale, which is required for many high-precision applications, free-running microcombs must be locked to more stable reference sources. However, ultrastable reference sources, particularly optical cavity-based methods, are generally bulky, alignment-sensitive and expensive, and therefore forfeit the benefits of using chip-scale microcombs. Here, we realize compact and low-phase-noise microwave and soliton pulse generation by combining a silica-microcomb (with few-mm diameter) with a fibre-photonic-based timing reference (with few-cm diameter). An ultrastable 22-GHz microwave is generated with −110 dBc/Hz (−88 dBc/Hz) phase noise at 1-kHz (100-Hz) Fourier frequency and 10−13-level frequency instability within 1-s. This work shows the potential of fully packaged, palm-sized or smaller systems for generating both ultrastable soliton pulse trains and microwaves, thereby facilitating a wide range of field applications involving ultrahigh-stability microcombs.

Review on microwave pulse generation using electro-optical sources

Review on microwave pulse generation using electro-optical sources

Review on microwave pulse generation using electro-optical sources

Review on microwave pulse generation using electro-optical sources

Tunable Microwave Pulse Generation Based on an Actively Mode-Locked Optoelectronic Oscillator

Tunable Microwave Pulse Generation Based on an Actively Mode-Locked Optoelectronic Oscillator

Frequency-Tunable Pulsed Microwave Waveform Generation Based on Unbalanced Single-Arm Interferometer Excited by Near-Infrared Femtosecond Laser

Femtosecond laser-excited generation of frequency-tunable microwave pulses, based on an unbalanced single-arm interferometer with frequency-to-time mapping, has been proposed and demonstrated with easy-to-obtain commercial devices. The optical wave-to-microwave frequency conversion, which involves continuous tuning in the range from 2.0 GHz to 19.7 GHz, was achieved based on simple spatial–optical group delay adjustment. Additionally, the pulse duration of the microwave waveform was measured to be 24 ns as the length of the linear dispersion optical fiber was fixed at 20 km. In addition, owing to the designs of the single-arm optical path and polarization-independent interference, the generated microwave pulse train had better stability in terms of frequency and electrical amplitude. Furthermore, a near-triangular-shaped microwave pulse at 4.5 GHz was experimentally obtained by the superposition of two generated sinusoidal signals, which verified the potential of this system to synthesize special microwave waveform pulses.

Generation of Short Microwave Pulses by Compression of Chirped Signals Obtained by Raman Backscattering on Electron Beam With Variable Energy

We suggest method of short microwave pulse generation by means of compression of chirped pulses obtained in the process of Stimulate Raman Backscattering (SRB) on electron beam with variable energy. We assume that in frequency modulator the pump wave, co-propagating with the electrons is scattered into counter propagating signal wave with frequency downshift. The absolute instability, developing in this system, allows for the smooth tuning of the signal frequency by varying the energy of electrons. The SRB modulator can produce a frequency-tunable signal with a bandwidth up to 10% and conversion efficiency up to 70%, when using a 50 kW, 35 GHz gyrotron as a source of pump wave. Simulation of subsequent compression with multi-fold helically corrugated waveguide (HCW) as dispersive line showed that optimization of energy temporal dependence in modulator together with compressor parameters provides the possibility to produce pulses with the peak power up to 3 MW which exceeds the power of driving gyrotron by the factor of 60.

Microwave pulse generation via employing an electric signal modulator to achieve time-domain mode locking in an optoelectronic oscillator.

An actively mode-locked optoelectronic oscillator (OEO) is proposed and demonstrated to generate chirp-free microwave pulse trains with variable repetition rates. Time-domain mode locking is realized by using an electric signal modulator to achieve amplitude modulation of the generated microwave signal in the OEO cavity. Through setting the externally applied electric signal frequency to be equal to the integral multiple of the free spectral range, a microwave pulse train with a low close-to-carrier phase noise is generated. In the experiment, microwave pulse trains with repetition rates of 179.94 and 360.00 kHz are generated through fundamental mode locking and 2nd-order harmonic mode locking, respectively. Under fundamental mode locking, the phase noise of the actively mode-locked OEO at 100 Hz frequency offset is measured to be 30 dB lower than that in a free-running OEO.

Real-Time Volumetric Thermoacoustic Imaging and Thermometry Using a 1.5-D Ultrasound Array.

Noninvasive thermal therapies for the treatment of breast cancer depend on accurate monitoring of tissue temperature to optimize treatment and ensure safety. This work describes a real-time system for 3-D thermoacoustic imaging and thermometry (TAI-TAT) for tracking temperature in tissue samples during heating. The study combines a 2.7-GHz microwave pulse generator with a custom 1.5-D 0.6 MHz ultrasound array for generating and detecting TA signals. The system is tested and validated on slabs of biological tissue and saline gel during heating. Calibration curves for relating the TA signal to temperature were calculated in saline gel (3.40%/°C), muscle (1.73%/°C), and fat (1.15%/°C), respectively. The calibrations were used to produce real-time, volumetric temperature maps at ~3-s intervals with a spatial resolution of approximately 3 mm. TAT temperature changes within a region of interest were compared to adjacent thermocouples with a mean error of 17.3%, 13.2%, and 20.4% for muscle, gel, and fat, respectively. The TAT algorithm was also able to simultaneously track temperatures in different tissues. With further development, noninvasive TAI-TAT may prove to be a valuable method for accurate and real-time feedback during breast cancer ablation therapy.