An analysis of the autodyne effect of a radio-pulse oscillator with frequency modulation

The results of investigations of an autodyne oscillator with concurrent pulse-and frequency modulation are presented, with the oscillator being affected by its own reflected radiation. The main relations for the analysis of the autodyne response with respect to the time delay of the reflected radiation are presented for the case of an arbitrary frequency modulation law. Special features of self-oscillations of such autodynes are addressed, which permit improvement of the characteristics and extension of the functional capabilities of autodyne systems in SRR applications. The analytical results are verified using the experimental prototypes of the autodyne sensors based on the oscillators employing the mm-range Gunn diodes operating on well-known principles. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 80–88, July, 2008.     

Autodyne Effect in Weak-Resonant BWO with Chaotic Dynamics

An autodyne phenomenon in the O-type Weak-Resonant Backward Wave Oscillator of K _a-band working in chaotic oscillatory regime is under investigation. The main attention is paid to the studying of the action of decorrelated reflected signals on the modulation of the power spectral density of the chaotic oscillations. Physical mechanisms are revealed and phenomenological model is suggested to explain the strong PSD modulation observed under the affect of the small refelected signal. The PSD modulation index has been introduced and its anomalous increase with the enlargement of the distance to the load is revealed experimentally, as well as the physical explanation for that effect is presented. All physical results obtained are valid for the autodyne effect in any chaotic oscillator. The results obtained can be used for the design of different autodyne based devices for the remote sensing, microwave telemetry and control systems.     

Analysis of autodyne effect of an rf oscillator

Theoretical and experimental results of investigations on a pulse-modulated autodyne oscillator affected by its own reflected radiation are presented. The main relations for the analysis of autodyne response as a function of reflected radiation delay time are obtained. Characteristics of autodyne self-oscillations, which allow improving their performance and extend functional capabilities of autodyne systems for short-range radar applications, are discussed. Experimental results are obtained for a TIGEL-08 oscillator module manufactured on the basis of a mm-wave Gunn diode using a hybrid-integral technology. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 64–70, March, 2008.     

Autodyne effect in multifrequency osciliators

The variations of the individual-oscillator amplitudes, generalized phase differences of the generated harmonics, and self-oscillation frequency of a multifrequency autodyne oscillator under the influence of reflected radiation for each of the generated harmonics are studied theoretically. Basic relations are obtained for analysis of the autodyne response of a multifrequency oscillator in synchronous and asynchronous operation. General conclusions are drawn concerning the self-oscillation characteristics of such autodynes that make it possible to improve the performance and expand the functional possibilities of autodyne systems for short-range radar.     

Analysis of Operating Regimes of EHF Hybrid-Integrated Autodynes Based on the Gunn Micropower Mesaplanar Diodes

The results of investigations into the operating regimes of EHF hybrid-integrated autodyne generators are given in the present paper. Multipurpose crystals with three mesaplanar structures, one of which serves as an active element and the two others serve as control elements, are used as active elements. The segment of a coplanar strip transmission line are used as a resonant system of the autodyne. The cw regime of autodyne operation and regimes with various types of radiation modulation, which allow the class of problems solved by short-range radar systems to be extended, are examined.     

Special features of practical measurement of parameters of promisisng frequency-modulated short-range millimeter radars

A few techniques for measuring major autodyne and homodyne parameters with frequency modulation in the millimeter range are discussed, including those using the Analog Devices standardized measuring systems. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 99–103, September, 2006.     

Generalized Model and Basic Equations for an EHF Autodyne HMC Based on the Gunn Planar Mesas

The results of theoretical investigations into an EHF autodyne HMC with the multipurpose crystal having N planar mesas are presented. Continuous regime of NMC operation as a multimodular autodyne system of polyharmonic generation under the action of self-radiation reflected at each harmonic is examined. Basic relations for autodyne response are derived. General conclusions on specific features of autodyne self-oscillations, which allow its characteristics to be improved and the functional capabilities of autodyne short-range radar systems to be extended, are made.     

Blind parameter estimation of pseudo-random binary code-linear frequency modulation signal based on Duffing oscillator at low SNR

Conventional parameter estimation methods for pseudo-random binary code-linear frequency modulation(PRBCLFM) signals require prior knowledge, are computationally complex, and exhibit poor performance at low signal-to-noise ratios(SNRs). To overcome these problems, a blind parameter estimation method based on a Duffing oscillator array is proposed. A new relationship formula among the state of the Duffing oscillator, the pseudo-random sequence of the PRBC-LFM signal, and the frequency difference between the PRBC-LFM signal and the periodic driving force signal of the Duffing oscillator is derived, providing the theoretical basis for blind parameter estimation. Methods based on amplitude method, short-time Fourier transform method, and power spectrum entropy method are used to binarize the output of the Duffing oscillator array, and their performance is compared. The pseudo-random sequence is estimated using Duffing oscillator array synchronization, and the carrier frequency parameters are obtained by the relational expressions and characteristics of the difference frequency. Simulation results show that this blind estimation method overcomes limitations in prior knowledge and maintains good parameter estimation performance up to an SNR of-35 d B.     

CO2激光自差信号的功率谱研究

利用10MHz高速数据采集和处理系统分析了激光自差信号的功率谱.其功率谱分布在低频区;当多普勒频移增大时,自差信号的带宽增加,功率谱对频率的积分收敛于信号的功率.实验结果还表明,利用高速数据采集和处理的分析方法,比频谱分析仪有更多的优点.     

Injection locking of a diode laser locked to a Zeeman frequency stabilized laser oscillator

We describe the design and performance of an injection-locked diode laser locked to a stabilized, single frequency, unmodulated diode laser. The master oscillator is a grating-tuned, external cavity diode laser which is stabilized on a Doppler free alkali metal resonance transition frequency via Zeeman locking. The master oscillator frequency is shifted by an acousto-optic modulator, which provides optical isolation of the master oscillator laser while tuning of the acousto-optic modulation frequency can also provide frequency offset tuning. The slave laser is a free running diode which is injection-locked by a small fraction of the frequency shifted master oscillator light. Good long- and short-time frequency stability are observed for both the Zeeman-locked master oscillator and the injection-locked slave laser.     

Microwave Photonic Up- and Down-Converter with Tunable Phase Shift Based on an Integrated Dual-Polarization Dual-Parallel Mach–Zehnder Modulator without Optically Filtering

ABSTRACT

In this paper, we propose and numerically simulate a microwave photonic phase-tunable frequency converter (MPPTFC) without optically filtering to realize both frequency up- and down-conversion and a full 360° phase-shift for the microwave signal based on an integrated dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM). In the proposed scheme, both microwave RF signal and frequency-tunable local oscillator (LO) are modulated on the lightwave by single-sideband carrier suppression (SSB-CS) modulation to generate optical orthogonally polarized optical tones carrying RF signal with up- or down-converted frequency. A PolM that can support lightwave modulation with opposite modulation indices in transverse electric (TE) and transverse magnetic (TM) modes is used to introduce a phase difference between the two modes. Then the orthogonally polarized optical tones are aligned into a single polarized state by a polarizer (Pol) and detected by a photodiode (PD), a frequency-converted and phase-shifted microwave signal can be obtained. Simulation results demonstrate that the proposed MPPTFC can up-/down-convert the microwave signal with a tunable frequency shift of LO frequency and realize a 360° continuously tunable phase shift via the DC bias voltage of the PolM simultaneously.     

Linear and nonlinear resonance features of an erbium-doped fibre ring laser under cavity-loss modulation

The continuous-wave output of a single-mode erbium-doped fibre ring laser when subjected to cavity-loss modulation is found to exhibit linear as well as nonlinear resonances. At sufficiently low driving amplitude, the system resembles a linear damped oscillator. At higher amplitudes, the dynamical study of these resonances shows that the behaviour of the system exhibits features of a nonlinear damped oscillator under harmonic modulation. These nonlinear dynamical features, including harmonic and subharmonic resonances, have been studied experimentally and analysed with the help of a simple time-domain and frequency-domain information obtained from the output of the laser. All the studies are restricted to the modulation frequency lying in a regime near the relaxation oscillation frequency.     

Ultra-Stable Rubidium-Stabilized External-Cavity Diode Laser Based on the Modulation Transfer Spectroscopy Technique

We construct an ultra-stable external-cavity diode laser via modulation transfer spectroscopy referencing on a hyperfine component of the ST Rb D2 lines at 780 nm. The Doppler-free dispersion-like modulation transfer signal is obtained with high signal-to-noise-ratio. The instability of the laser frequency is measured by beating with an optical frequency comb which is phase-locked to an ultra-stable oven controlled crystal oscillator. The Allan deviation is 3.9 × 10-13 at I s averaging time and 9.8 ×10-14 at 90s averaging time.     

Phase mismatch effects on the dynamics of a semilinear photorefractive oscillator with reflection-type gratings

This paper describes the effect of pump waves misalignement on the performance of the semilinear photorefractive coherent oscillator with the reflection gratings. The oscillation intensity and its modulation frequency are calculated numerically for different misalignement angles, coupling strengths and pump intensity ratios. It is shown that a small angular detuning of the pump wave, less than one milliradian, extends the range of pump ratios and the range of coupling strengths for which a non-degenerate oscillation occurs. The results of experiments with the BaTiO₃-based semilinear oscillator are in qualitative agreement with the calculated data.     

Response of a Bloch oscillator to a THz-field

In this paper we report on the observation of response of a Bloch oscillator at room temperature to a THz-field of a frequency larger than the Bloch frequency. The oscillator consisted of a semiconductor superlattice structure, with an applied dc voltage giving rise to a dc electron drift current. Submitting the oscillator to a field at a frequency of 3.3 THz caused a sizeable reduction of the current; the THz-field was generated by use of intense THz-radiation pulses focused on an antenna coupled to the superlattice. We attribute the THz-field induced reduction of the current to a frequency modulation of the Bloch oscillations of electrons at the frequency of the THz-field, leading to reduction of the electron drift velocity and, consequently, of the current.     

EHF autodyne signals for tracking the parameters of moving objects

To improve the characteristics of short-range autodyne radar systems and to extend their application range, it is very important from both theoretical and practical viewpoints to study the autodyne signal waveform and spectrum. In the present paper, the results of investigations into the specific features of the autodyne response of an EHF generator are presented as functions of the parameters of a moving object and the radiation reflectance. The results of experiments performed in the present work are in agreement with theoretical conclusions. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 54–60, July, 2000.     

Noise properties of an optical frequency comb from a SESAM-mode-locked 1.5-μm solid-state laser stabilized to the 10?13 level

We present a detailed investigation of the noise properties of an optical frequency comb generated from a femtosecond diode-pumped solid-state laser operating in the 1.5-??m spectral region. The stabilization of the passively mode-locked Er:Yb:glass laser oscillator, referred to as ERGO, is achieved using pump power modulation for the control of the carrier envelope offset (CEO) frequency and by adjusting the laser cavity length for the control of the repetition rate. The stability and the noise of the ERGO comb are characterized in free-running and in phase-locked operation by measuring the noise properties of the CEO, of the repetition rate, and of a comb line at 1558?nm. The comb line is analyzed from the heterodyne beat signal with a cavity-stabilized ultra-narrow-linewidth laser using a frequency discriminator. Two different schemes to stabilize the comb to a radio-frequency (RF) reference are compared. The comb properties (phase noise, frequency stability) are limited in both cases by the RF oscillator used to stabilize the repetition rate, while the contribution of the CEO is negligible at all Fourier frequencies, as a consequence of the low-noise characteristics of the CEO-beat. A?linewidth of ??150?kHz and a fractional frequency instability of 4.2×10^?13 at 1?s are obtained for an optical comb line at 1558?nm. Improved performance is obtained by stabilizing the comb to an optical reference, which is a cavity-stabilized ultra-narrow linewidth laser at 1558?nm. The fractional frequency stability of 8×10^?14 at 1?s, measured in preliminary experiments, is limited by the reference oscillator used in the frequency comparison.     

A first-principles molecular dynamics approach for predicting optical phonon lifetimes and far-infrared reflectance of polar materials

The Lorentz oscillator model is well-known for its effectiveness to describe the far-infrared optical properties of polar materials. The oscillator strength and damping factor in this model are usually obtained by fitting to experimental data. In this work, a method based on first-principles simulations is developed to parameterize the Lorentz oscillator model without any fitting parameters. The high frequency dielectric constant is obtained from density functional perturbation theory, while the optical phonon frequencies and damping factors are calculated using an analysis of ab initio molecular dynamics trajectories. This method is then used to predict the far-infrared properties of GaAs, and the results are in good agreement with experimental data.     

X波段重频过模返波振荡器实验研究

根据两腔振荡器和返波管的特点研制了过模结构返波振荡器, 该器件主要由调制腔和换能腔(慢波结构)两部分组成. 调制腔既是电子束的预调制腔, 也是微波谐振反射腔, 它同换能腔形成一个过模微波谐振腔,经调制腔调制后的电子束在换能腔中实现束波能量转换. 根据加速器的电子束参数(束压为1 MV,束流为20 kA)设计了一个X波段的高功率微波器件,2.5维粒子模拟程序模拟得到微波频率为8.25 GHz,输出功率为5.70 GW. 用超导磁体作为引导磁场,单次运行输出微波功率为5.20 GW,微波频率为(8.25±0. 关键词： 两腔振荡器 返波振荡器 多波切连科夫发生器