Generation Of Microwave Pulses Research Articles

Nonlinear dispersion-based incoherent photonic processing for microwave pulse generation with full reconfigurability

A novel all-optical technique based on the incoherent processing of optical signals using high-order dispersive elements is analyzed for microwave arbitrary pulse generation. We show an approach which allows a full reconfigurability of a pulse in terms of chirp, envelope and central frequency by the proper control of the second-order dispersion and the incoherent optical source power distribution, achieving large values of time-bandwidth product.

Self-induced transparency, compression, and stopping of electromagnetic pulses interacting with beams of unexcited classical oscillators

The self-induced transparency effects that emerge when short (on the relaxation time scale) light pulses propagate in a two-level noninverted medium are well known in optics. The interaction of microwave pulses with an initially rectilinear electron beam under cyclotron resonance conditions can serve as a classical analog of the described effects. In this case, at a certain intensity of the input signal, the cyclotron absorption is replaced by self-induced transparency when the input pulse propagates almost without any change of its profile, forming a soliton whose amplitude and duration are rigidly related to its velocity. In a certain domain of parameters, this process is accompanied by significant two- or threefold compression of the initial pulse, which is of practical interest for the generation of multigigawatt picosecond microwave pulses. Since the soliton velocity lies between the unperturbed group velocity of the radiation and the translational velocity of the particles, another nontrivial effect in the case of interaction with a counterpropagating electron beam is the possibility of a significant deceleration or full stopping of the electromagnetic pulse.

Phase and Amplitude Modulator for Microwave Pulse Generation

We present a microwave amplitude/phase modulation device based on superconducting resonator and synthetic transmission line technology. The primary benefits of this device are agile frequency response for modulation over a 2 GHz bandwidth, low power dissipation and potential for integration with superconducting qubits and high-speed SFQ logic. This device demonstrates phase modulation of >; 90°, and amplitude modulation of ≈ 30 dB in a 2 GHz local oscillator bandwidth. We also show modulation of a 3.5 GHz microwave signal by a Gaussian pulse with σ ≈ 4 ns . The targeted application of this technology is for low power microwave pulse generation for qubit applications. In this paper we present results for the modulator and introduce potential applications in quantum computing.

Generation of chaotic microwave pulses in broadband self-oscillating ring system with ferromagnetic film under the action of external pulse-modulated microwave signal

We have experimentally studied specific features of the generation of chaotic microwave pulse trains in a self-oscillating ring system with nonlinear delay line on surface magnetostatic waves, bandpass filter, and power amplifier on GaAs field-effect transistors under the action of an external pulse-modulated microwave signal occurring outside the band of the generated chaotic signal. It is established that a decrease in the off/duty ratio in the external pulse-modulated microwave signal leads to an increase in this ratio for the chaotic microwave pulses. The integral power of the chaotic microwave signal generated under the pulsed external signal action is increased as compared to the power of signal generated in the autonomous regime.

Numerical Studies of the Propagation of High-Power Damped Sine Microwave Pulse in the Atmosphere

Simulations of the propagation of a high-power damped sine microwave pulse in the atmosphere in fluid model are presented, in which various reaction sets of oxygen and nitrogen are taken into account for calculating the ionization parameters. The accuracy of our method is verified by experimental results. Numerical simulations show that the electrons in the air breakdown lead to large attenuation in the tail of the pulse and high-frequency breaking, and the air breakdown depends strongly on the damped coefficient of the pulse and altitude. At high altitude, the modulated frequency has significant influence on the air breakdown.

Generation of chaotic microwave pulses with the help of passive synchronization of spin wave self-modulation frequencies in self-oscillatory ring systems

Passive synchronization (PS) of spin wave self-modulation frequencies of a chaotic microwave signal has been observed for the first time in a self-oscillatory ring system involving a nonlinear passive element with saturable absorption. The development of PS led to the generation of a periodic train of chaotic microwave pulses with an off/duty ratio exceeding 20. It is established that the repetition period of chaotic microwave pulses can be controlled by changing gain in the ring system.

Fiber-Based Photonic Generation of High-Frequency Microwave Pulses With Reconfigurable Linear Chirp Control

A fiber-based approach for linear and continuous chirp control in photonics microwave pulse generation is proposed and demonstrated. The technique is based on spectral pulse shaping combined with nonlinear frequency-to-time mapping (FTM). Particularly, the proposed fiber-optics method provides an unprecedented arbitrary chirp-rate control by combining spectral shaping induced by dispersion unbalance in a fiber interferometer, resulting in a nonlinear-chirp frequency interference pattern, with nonlinear FTM. Full linear chirp reconfigurability, including positive, negative and zero chirp rates, is achieved from a single fiber-optics platform by simply varying the relative delay between the interferometer arms. Moreover, a simple balanced photodetection strategy is implemented to achieve dc-free microwave pulses with significantly improved noise figures. High-quality dc-free gigahertz-frequency microwave sinusoids were successfully generated with central frequencies ranging from 100 MHz to 25 GHz and chirp rates ranging from -160 MHz/ns to +160 MHz/ns.

On-chip RSFQ microwave pulse generator using a multi-flux-quantum driver for controlling superconducting qubits

We have been studying a superconducting quantum-computing system where superconducting Josephson-junction quantum bits (qubits) are controlled and read out by rapid single-flux-quantum (RSFQ) circuits. In this study, we designed and fabricated an on-chip RSFQ microwave pulse generator (MPG), which generates microwave pulses with the time resolution of sub-ns for precise control of qubit states. The output microwave amplitude of the MPG can be amplified to more than 350μV using a multi-flux-quantum (MFQ) driver, which increases the number of the propagating single-flux-quantum (SFQ) pulses. Fundamental properties of the MFQ driver and the RSFQ MPG were measured at 4.2K. It was confirmed that the MFQ driver can amplify an SFQ pulse up to six MFQ pulses and the irradiation time and the amplitude of the output microwave of the RSFQ MPG can be controlled adequately.

Generation of chaotic microwave pulses in a ring system based on a klystron power amplifier and a nonlinear delay line on magnetostatic waves

The autonomous generation of stationary chaotic microwave pulse trains in a self-oscillating ring system with a multicavity klystron power amplifier operating in a small-signal regime and a wideband non-linear delay line on surface magnetostatic waves has been experimentally studied. It is established that the characteristics of generated chaotic microwave pulses can be controlled by varying the electron beam current and accelerating voltage in the klystron.

Chirped Microwave Pulse Generation Based on Optical Spectral Shaping and Wavelength-to-Time Mapping Using a Sagnac Loop Mirror Incorporating a Chirped Fiber Bragg Grating

In this paper, we propose and demonstrate an approach to optically generating chirped microwave pulses with tunable chirp profile based on optical spectral shaping using a Sagnac loop filter incorporating a chirped fiber Bragg grating (CFBG) and linear wavelength-to-time mapping in a dispersive element. In the proposed approach, the optical power spectrum of an ultrashort optical pulse is shaped by a CFBG-incorporated Sagnac loop mirror that has a reflection spectral response with a linearly increasing or decreasing free spectral range. The spectrum-shaped optical pulse is then sent to a dispersive element to perform the linear wavelength-to-time mapping. A chirped microwave pulse with the pulse shape identical to that of the shaped spectrum is obtained at the output of a high-speed photodector. The central frequency and the chirp profile of the generated chirped microwave pulse can be controlled by simply tuning the time delay in the Sagnac loop mirror. A simple mathematical model to describe the chirped microwave pulse generation is developed. Numerical simulations and a proof-of-principle experiment are implemented to verify the proposed approach.

Analysis of the Pulse-Modulated Microwave Propagation into 3D Anisotropic Heart Model by SIE Method

Here we present the electrodynamical analyses of microwave pulses propagation in a 3D anisotropic heart model for the flrst time. The electrodynamical rigorous solution of Maxwell's equations related to the microwave pulse propagation in the 3D heart model with anisotropic and isotropic media is presented here. The myocardium tissue media is an anisotropic lossy media and blood is an isotropic lossy media. The boundary problem was solved by using the singular integral equations' (SIE) method. Our solution, obtained by the SIE method, is electrodynamically rigorous. The false roots do not appear and the boundary conditions have to be satisfled only on the surfaces dividing difierent materials. The frequency of the carrier microwave is 2.45GHz. The modulating signals are triangular video pulses with the on-ofi time ratio equal to 5 and 100. The pulse durations were always equal to 20s. Microwave electric fleld distributions were analysed at three longitudinal cross-sections of the heart model. The distributions of electric fleld for the anisotropic and isotropic heart models are compared here. 1. INTRODUCTION A human heart may be under in∞uence of the microwave radiation for the medical examination of patients (1) or because of hazardous environment (2). The tissue of a heart, in the normal state possesses anisotropic properties; however, the anisotropy of heart tissue grows with some illnesses (3,4). Desiring to diagnose diseases of heart with the help of the microwave equipment it is necessary to investigate the process of microwave interaction with the anisotropic heart tissue. Research data of the anisotropic properties of heart tissue along and across of myocardium muscle flbers are given in (3). An electrodynamical analysis of the difiraction problem relating to scattering of the pulse- modulated microwave on the anisotropic heart model is given in this article. We solve this problem, using the SIE method (5). In our case the model of heart contains both isotropic and anisotropic area. The model that contains simultaneously anisotropic and isotropic media we will call an anisotropic model. The model that contains only isotropic media we will call an isotropic model.

Generation of gigawatt 10-GHz pulses with stable phase

The generation of microwave pulses in a 10-GHz range has been studied in a nonstationary relativistic backward wave oscillator (BWO) operating at a pulse train repetition rate of up to 300 Hz. Regimes with a stabilized phase of the high-frequency filling of pulses with respect to the accelerating voltage pulse front have been observed at a BWO peak output power of ∼1 and 3 GW. In pulse trains with a length of 10–100 s, the average output microwave power reached ∼1 kW.

SINGULAR INTEGRAL METHOD FOR THE PULSE-MODULATED MICROWAVE ELECTRIC FIELD COMPUTATIONS IN A 3D HEART MODEL

The electrodynamical rigorous solution of Maxwell's equations related to the microwave pulse propagation inside a three- dimension heart model is presented here. The boundary problem was solved by using the singular integral equations' method. The carrier microwave frequency is 2.45 GHz. The pulse durations were always equal to 20 ms. The modulating signals are triangular video pulses with the on-off time ratio equal to 5 and 100. The model heart was limited by a non-coordinate shape surface and it consisted of two different size cavities. The heart cavities were schematic images of the left and right atriums and ventricles. In our calculations the cavities were filled with blood with the permittivity e2 =5 8− i19 and the walls of the heart consisted of myocardium tissue with the permittivity e1 =5 5− i17. Microwave electric field distributions were analysed at four longitudinal cross-sections of the heart model.

High-Voltage Rectifier Diodes Used as Photoconductive Device for Microwave Pulse Generation

Generation of unipolar and bipolar pulses by using high- and medium-voltage silicon rectifier diodes is achieved. These components are provided by the French Atomic Energy Commission (CEA). Furthermore, these devices work in the linear mode of photoconducting switches. Generation of electrical unipolar pulses with an amplitude of 10.7 kV and a full-width at half-maximum of 300 ps by using only 1.2 mJ of optical power is demonstrated. This energy value is 10-100 times less than usually published during the past decades. Furthermore, the linear mode running of these devices permits to synchronize several generators with a precision as low as 2 ps. This low timing jitter is useful for bipolar generators in order to control their spectrum with high precision, i.e., bipolar pulses of 3 kV peak-to-peak have been generated with a cycle duration of 400 ps and an optical energy of 1 mJ

Design, Numerical Analysis and Test of HF Absorber

The paper presents numerical analysis of the microwave absorber design. It is possible to use modifled concept of the absorber. There were used novel numerical methods (flnite element method (FEM)) for thin layers modelling with sandwich non-isotropic electromagnetic materials. Modifled absorber has appropriate properties and it is possible to use it in non- re∞ecting chamber construction. The non-re∞ecting chamber will be used for open space testing of relativistic microwave pulse generator; Pmax = 500MW, tp = 10i100ns. An experimental testing of the proposed pyramidal absorbers was done in the laboratories at University of Defence Brno, Czech Republic. DOI: 10.2529/PIERS060901094301 Figure 2: The shielded laboratory. The calorimetric sensor has disc design. The carbon with changed crystal lattice is used as one of the thin layers. Combined calorimetric sensors was designed for microwave vircator with output power Pmax = 500MW, length of pulse tp 2 ns. Usually, two types of the absorber materials (non-re∞ecting) are used. The polyurethane foam impregnated by graphite is used in high frequency range (more than 1GHz) | the foam employs heat losses in material. The ferrite absorber is used in low frequency range | the ferrite absorber employs magnetic losses. The mentioned materials are used to prevent re∞ection of the electromag- netic waves inside the laboratory. The idea is to rebuild the laboratory in Fig. 2 to the shielded non-re∞ecting chamber for measurements and experiments with power microwave pulse generators iPmax = 500MW, length of pulse tp 2 ns. 2. SHIELDING OF THE WALLS It is possible to deflne an electromagnetic shielding by help of shielding coe-cient ?. It represents the ratio of the electrical fleld Et (magnetic fleld Ht) in the given place of the chamber to the electrical fleld Ei (magnetic fleld Hi) incoming at the absorber. ? = Et

Microwave nonlinear resonance incorporating the helium heating effect in superconducting microstrip resonators

Nonlinear microwave phenomena in superconducting niobium–teflon microstrip resonators cooled by liquid helium are studied. Helium heating caused by the losses of microwave power in superconductor changes the resonant frequency because of the temperature dependence of helium permittivity. Manifestations of this thermal instability discover a new type of nonlinear phenomena including the generation of the monochromatic microwave pulses, generation of acoustic signals. The found nonlinear resonances are explained by thermally induced variations of the helium dielectric permittivity caused by the microwave power dissipated in superconductor, which enable incorporating the jump nonlinearity of a liquid–vapour phase transition in helium.

Generation of Powerful Ultrashort Microwave Pulses

We study theoretically and experimentally the possibility of generation of ultrashort powerful microwave pulses. The regime of spatial accumulation of electromagnetic energy is considered in the case where the pulse propagates oppositely to the electron flow in a long slow-wave structure. We show that during transformation of the kinetic energy of electrons to the energy of an electromagnetic pulse, the pulse power is not limited by the electron-beam power. Using compact high-current accelerators, we obtain gigawatt pulses in the 3-cm and 8-mm wavelength ranges with power conversion factor exceeding unity.

Generation of complex microwave and millimeter-wave pulses using dispersion and kerr effect in optical fiber systems

We study a new method to synthesize high-frequency complex microwave and millimeter-wave pulses using dispersion, Kerr effect, and group velocity delay in optical fiber systems. The profile of the generated pulses can be controlled by changing the parameters of the optical system. Nonlinear propagation effect in fibers can be used to generate electrical pulses with an extremely broad spread spectrum. Soliton trapping can be used to generate electrical pulses with a controllable frequency. Implicit results are given when dispersion or nonlinear effect can be neglected. Generation of electrical pulses with a controllable microwave frequency is demonstrated experimentally using a Mach-Zehnder interferometer and a chirped fiber Bragg grating.

Highly efficient generation of subnanosecond microwave pulses in ka-band relativistic bwo

This paper presents the results of investigations of the mode of nonsteady-state oscillations with a short-time power burst which is characteristic of the initial stage of the transient process in a backward wave oscillator when the beam operating current is far in excess of the starting current. Numerical simulations have yielded the conditions under which the efficiency of the power transfer from an electron beam with a particle energy of 300 keV, a current of 2 kA, and a duration of 1 ns into a microwave pulse containing 8-10 high-frequency field periods approaches 90%. Experimentally, it has been demonstrated that the production of pulses like these with a duration of 200-250 ps, a power of up to /spl sim/400 MW, and a central frequency of about 38 GHz is feasible.

Generation of subnanosecond microwave pulses based on the Cherenkov superradiance effect

Experimentally observed Cherenkov superradiance produced by a subnanosecond electron bunch traveling through a partially filled waveguide is reported. 400-ps microwave pulses with a peak power of 2 MW are obtained. The experimental results are in good agreement with the theoretical analysis and numerical simulations performed with the help of the PIC code KARAT.