Microstrip active path array with beam scanning

A four-element microstrip active path array with beam scanning is described consisting of locked path oscillators with DC bias phase control. The radiating elements are formed by transistor oscillators whose frequency is controlled by a rectangular patch. The oscillators are locked to an external source. Control of the radiated phase is achieved by varying the bias on the transistor. Close to 360 degrees of radiated phase control can be achieved from each element by locating two oscillators on each patch. Measured results indicate that beam scanning in excess of 40 degrees can be achieved.<>     

Semi-chaotic pulse effects in self-modulating Gunn oscillators

Self-modulation behaviour has been observed in GaAs Gunn oscillators operating at W-band, leading to nanosecond pulses of relatively high peak power. Pulse repetition rates and pulse-widths can be varied reproducibly as a function of bias voltage and bias line termination, and there is evidence for semi-chaotic behaviour in certain regimes.     

On the dynamics of two-dimensional array beam scanning viaperimeter detuning of coupled oscillator arrays

Arrays of voltage-controlled oscillators coupled to nearest neighbors have been proposed as a means of controlling the aperture phase of one-dimensional (1-D) and two-dimensional (2-D) array antennas. It has been demonstrated, both theoretically and experimentally, that one may achieve linear distributions of phase across a linear array aperture by tuning the end oscillators of the array away from the ensemble frequency of a mutually injection-locked array of oscillators. These linear distributions result in steering of the radiated beam. It is demonstrated theoretically that one may achieve similar beamsteering in two dimensions by appropriately tuning the perimeter oscillators of a 2-D array. The analysis is based on a continuum representation of the phase in which a continuous function satisfying a partial differential equation of diffusion type passes through the phase of each oscillator as its independent variables pass through integer values indexing the oscillators. Solutions of the partial differential equation for the phase function exhibit the dynamic behavior of the array during the beamsteering transient     

高次谐波锁模飞秒掺镱光纤激光器的噪声情况

高重复频率的飞秒激光在高速激光测距和三维成像等领域有着非常重要的作用。其中基于飞秒光纤激光器的高次谐波锁模是获得GHz量级以上高重复频率脉冲的重要手段之一。基于含腔内光栅对色散补偿的非线性偏振旋转（NPR）锁模的掺镱（Yb）光纤激光器,在180 mW泵浦光时获得了稳定的143 MHz基频锁模脉冲序列,当泵浦光功率升至1 W时获得了最高20次谐波（2.86 GHz）锁模脉冲序列输出。系统地对比研究了基频锁模与高次谐锁模状态下,脉冲重复频率精密锁定后的艾伦偏差和相位噪声,7次谐波锁模状态下重复频率锁定精度能够保持在10?13 Hz@1 s的稳定度,为高次谐波锁模飞秒激光脉冲序列用于精密测量提供了实验依据。     

A 6.5 GHz-11.5 GHz source using a grid amplifier with a twistreflector

The authors have constructed and tested an oscillator using a grid amplifier with external feedback from a twist reflector. The twist reflector serves two functions; it changes the output polarization to match the input, and its position sets the feedback phase. This permits a wider tuning range than has been possible with previous grid oscillators. The source could be continuously tuned from 8.2 GHz to 11.0 GHz by moving the twist reflector. By moving the polarizer and mirror in the twist reflector independently, a 1.8-to-1 frequency range from 6.5 GHz to 11.5 GHz was achieved. The peak effective radiated power was 6.3 W at 9.9 GHz     

EMI-induced failures in crystal oscillators

An electromagnetic interference (EMI) induced failure mode pertaining to crystal-based voltage-controlled oscillators (VCO) has been studied. The failure consists of a transition to a frequency of oscillation that differs from the crystal's fundamental resonant frequency, when the circuit is temporarily exposed to continuous or pulsed radio-frequency electromagnetic fields. The new state persists even after the EMI source is removed and leads to hang-up in digital systems. This mode transition has been observed experimentally. Its essential properties have been predicted theoretically and simulated numerically, using simplified oscillator models. The likelihood of observing such a failure in a noisy electromagnetic environment is assessed with respect to the radiated susceptibility levels given in MIL-STD-461B     

电磁脉冲串作用下的数字通信电台敏感判据研究

为研究电磁脉冲串对数字通信电台的阻塞效应机理,以某型数字通信电台为受试对象,通过电磁脉冲注入试验,研究了受试电台误码率随电磁脉冲串幅值、重复间隔时间的变化规律。结果表明,随着脉冲幅值的增大,误码率先单调上升再以不同规律变化;不同脉冲重复率下受试电台的敏感误码率相差较大,敏感误码率不能用固定数值作为敏感判据,但利用敏感误码率与脉冲重复率成正比作为判据则具有较高的准确度,据此给出了受试数字电台的误码率敏感判据及试验方法,以通过部分试验数据获取任意脉冲重复率下的误码率敏感判据。     

Soliton-like pulse train generation using a nonlinear optical loop mirror constructed from dispersion decreasing fiber

A nonlinear optical loop mirror constructed from dispersion decreasing fiber is used to generate a high-quality pulse train from a dual frequency beat signal. Numerical simulations show that, unlike previous techniques based on adiabatic compression in dispersion decreasing fibers which limited the repetition rates to >50 GHz, the proposed method does not use adiabatic compression and can be extended to repetition rates <20 GHz using reasonable fiber lengths.     

激光干扰点源红外跟踪系统敏感参数研究

理论分析了激光干扰调制盘型点源跟踪系统敏感参数。根据理论分析结果:结合近场和外场到达点源跟踪系统处目标、干扰激光辐射功率密度等效原则,设计和进行了不同激光功率、外调制频率、外调制占空比和重复频率下激光干扰点源跟踪系统光学锁定断开近场模拟实验。理论分析和实验结果均表明:干扰激光功率、外调制频率和外调制占空比是实现调制盘型点源跟踪系统光学锁定断开的关键参数;干扰激光重复频率与调制盘载频没有严格对应关系,干扰激光重复频率和占空比应满足激光器最佳工作状态,以提高干扰激光功率。本文对小功率激光干扰系统设计研制和试验开展具有重要参考意义。     

A continuum model of the dynamics of coupled oscillator arrays forphase-shifterless beam scanning

The behavior of arrays of coupled oscillators has been previously studied by computational solution of a set of nonlinear differential equations describing the time dependence of each oscillator in the presence of signals coupled from neighboring oscillators. The equations are sufficiently complicated in that intuitive understanding of the phenomena which arise is exceedingly difficult. We propose a simplified theory of such arrays in which the relative phases of the oscillator signals are represented by a continuous function defined over the array. This function satisfies a linear partial differential equation of diffusion type, which may be solved via the Laplace transform. This theory is used to study the dynamic behavior of a linear array of oscillators, which results when the end oscillators are detuned to achieve the phase distribution required for steering a beam radiated by such an array     

V-band MMIC oscillator array

A V-band strongly-coupled single-chip MMIC oscillator array is presented. For wide bandwidth and easy biasing to push-pull type oscillators, modified 2-port microstrip parasitic coupled antennas are employed. When measured in a closed oversized waveguide, the MMIC oscillator array with two 2-port antennas and four oscillators radiated an output power of 4.4 dBm with excellent spatial power combining efficiency of 93% at 58.59 GHz.     

Numerical study on a frequency-tunable actively mode-locked fiber laser

We have numerically presented an actively mode-locked fiber laser with tunable repetition rate based on phase modulator. By finely optimizing intra-cavity parameters, the ultrashort pulses with tunable repetitive frequency at giga hertz level can be easily generated due to the balance between dispersion and nonlinearity in the fiber laser cavity. When the pulse frequency is changed from 1.0 GHz to 4.2 GHz, the spectral width increases from ~15.65 nm to ~27.25 nm. In addition, the corresponding pulse duration decreases from ~81.59 ps to ~31.57 ps. Moreover, these output pulses with giga hertz repetitive rates and the picosecond widths can be further compressed by using the reasonable dispersion medium. For the pulse regime with repetition frequency at giga hertz level, the obtained smallest pulse duration is about ~62 fs based on chirp pulse compression. We hope that these simulation results can promote further research and application in the ultrashort pulse lasers with high repetition rate.     

Higher harmonic generation in CMOS/SOS ring oscillators

Harmonic generation is found with 101-stage ring oscillators. Harmonics have not been observed for the usual ring oscillators with a small number of stages. If one mistakes the higher harmonic generation for the fundamental, he obtains a wrong propagation delay which is shorter than the real one. It is shown experimentally and theoretically that only odd harmonics are generated for the ring oscillators with an odd number of stages. The propagation delay tpdof the nth harmonic oscillation is given byt_{pd} = n cdot T/2NwhereTis the observed repetition period andNthe number of stages. Computer simulation shows that a ring oscillator with an even number of stages can also oscillate if every inverter is the same, and that the oscillation decays if there is asymmetry in the inverter chain. IfNis large and the effects of the deviations of the transistor parameters cancel one another, the harmonic oscillation that happens to be generated can continue.     

Two-dimensional array beam scanning via externally and mutuallyinjection-locked coupled oscillators

The use of arrays of injection-locked voltage-controlled oscillators coupled to nearest neighbors has been proposed as a means of controlling the aperture phase of one and two-dimensional (2-D) phased-array antennas. It has been demonstrated both theoretically and experimentally that one may achieve linear distributions of phase across a linear array aperture by injection locking to an external oscillator the end oscillators of an array of a mutually injection-locked oscillators. These linear distributions cause steering of the radiated beam. It is demonstrated theoretically here that one may achieve beamsteering in a similar manner in two dimensions by injecting appropriately phased signals into the perimeter oscillators of a 2-D array. The analysis is based on a continuum representation of the phase previously developed in the context of beamsteering via tuning of the perimeter oscillators     

高重频1.57μm内腔光学参量振荡器

理论分析了被动调Q固体激光泵浦的光参量振荡器。利用激光二极管泵浦,Cr4+:YAG被动调Q Nd:YAG激光泵浦的内腔光学参量振荡器,磷酸氧钛钾(KTP)晶体作为非线性晶体,获得了高重复频率,高峰值功率的人眼安全激光输出,改变Cr4+:YAG被动调Q晶体的参数,可获得不同重频不同脉宽的调Q激光脉冲;当Cr4+:YAG晶体初始透过率为 T0=80%时,获得了平均功率大于3.8 W,重频约80 kHz的1.572 μm波长信号光输出,脉宽30 ns,脉冲峰值功率达到1.58 kW。     

Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2laser

The envelope and frequency characteristics of the output pulse of a high repetition rate hybrid TEA-CO2laser are presented. Both the intrapulse and interpulse laser frequency stabilities are experimentally determined at repetition rates up to 300 Hz. The recovery of the CW laser signal following the generation of the TEA laser pulse is analyzed theoretically and experimentally. Short term reproducibilities of ±2 MHz are observed at a pulse repetition rate of 300 Hz with initial chirp rates of about 1.5 MHz/μs. Improvements and limits on power and repetition rate are discussed.     

Phased arrays based on oscillators coupled on triangular and hexagonal lattices

Phased arrays have been proposed in which a two-dimensional array of voltage-controlled oscillators coupled to nearest neighbors provides excitations for the radiating elements which are properly phased to result in a steerable radiated beam. These arrays have been arranged on a rectangular lattice and the beam is steered by tuning the oscillators along the four edges of the array. Proposed here are similar arrays in which the oscillators are coupled on a triangular lattice or a hexagonal lattice and provide excitations for radiating elements similarly disposed in a planar triangular array. Beam steering is accomplished by tuning the oscillators along the three edges of the array. The dynamic behavior of the arrays is studied via a continuum model and the results compared with those of a full nonlinear discrete analysis and a linearized discrete model.     

Long-term ultra-precision phase synchronization technique for locking the repetition rate of OFCs based on FLOM-PD

Long-term ultra-precision synchronization between optical frequency combs (OFCs) and microwave oscillators is important for various fields, including scientific observation, smart grid, positioning and navigation, etc. Here, a phase-locked loop system based on fiber loop optical-microwave phase detector (FLOM-PD) is proposed to realize the synchronization of the repetition rate of OFCs and rubidium atomic clocks. Firstly, the scheme and locking process of the system are elaborated, then the mathematical model of the system is established, and the feasibility of the scheme is proved by theoretical analysis and experimental verification. After synchronization, the instability of the system reaches 8.69×10-12 at 1 s and 2.94×10-13 at 1 000 s, indicating that the phase synchronization system can achieve ultra-precision and stability of OFCs repetition rate.     

虚地反馈法设计GaAs HBT微波宽带VCO单片电路

给出了采用虚地和反馈等原理实现振荡器设计的方法,该方法改变了设计振荡器的传统观念,不同形式的振荡电路总是可以变成放大器和移相选频网络级联,后经反馈构成.并给出了完整的计算公式和设计过程,另外还对虚地法进行了改进,解决了设计微波振荡器电路难以找到反馈通路的困难.利用该方法成功设计了采用HBT工艺制作的宽带VCO单片电路,验证了该方法的有效性.本方法对设计VCO电路有一定的参考价值.     

Complex digital oscillators and FSK modulators

The authors present complex-valued free running oscillators derived from digital filter structures. Four alternative approaches of complex direct-form and coupled-form oscillator structures are discussed leading to a multiple-output direct-form oscillator as the best solution from the viewpoint of computational efficiency. Two inherent advantages of direct-form structures can be avoided by appropriate means. The problem of poor frequency resolution at low frequencies is solved by a method called two's complement improvement (TCI). An oscillator frequency displacement is discovered which is caused by correlation between one state variable and the quantization error using finite arithmetic. This frequency error can be substantially reduced by appropriate error noise shaping. Some telecommunication applications like fixed-frequency complex oscillators for baseband signal processing, complex baseband frequency shift keying (FSK) modulators, and multiple-phase oscillators for multipath filters are discussed