Spectral predictions for pulse interval and width modulation

An expression for the frequency spectrum of pulse interval and width modulation (PIWM) is presented. Experimental results obtained have shown close agreement with spectral predictions from the formula. Performance figures are also included from a practical PIWM optical-fibre transmission system intended for use with TV and video signals.<>     

Noise performance of pulse interval modulation systems

Pulse interval modulation (PIM) is an asynchronous form of pulse position modulation. In this paper, the noise performance of the PIM system has been theoretically and experimentally investigated. A simple formula for the detected signal to noise ratio has been obtained which compared well with the measured data. The effect of noise shaping networks on the noise figure of the PIM detector has been predicted.     

Digital pulse interval modulation for optical communications

This article presents a study of digital pulse interval modulation (DPIM) for optical wireless communications using intensity modulation with direct detection. The DPIM code properties are discussed, and expressions for the transmission capacity, power spectrum, and error probability are presented. We show that for a given number of bits per symbol, DPIM has a higher transmission capacity, a similar spectral profile, and only a marginally inferior error probability performance compared with pulse position modulation, and is rather less complex to implement. Finally, problems associated with the nonuniform symbol length characteristics of DPIM together with possible solutions are discussed     

Ambiguity function of periodic pulse shaped sequences

The influence of ideal time-limited pulse shapes and ideal band-limited pulse shapes on the ambiguity function of periodic pulse shaped sequences, which are used in direct sequence spread-spectrum systems and pulse compression applications, is investigated. Furthermore, an upper bound on the absolute values of the sidelobes of the ambiguity function valid for an ideal time-limited pulse shape is derived     

光脉冲光纤周期复制技术研究

针对常用的多路高速光脉冲复制系统可能的实现形式进行了研究,根据各种应用中所需的插入损耗、输出脉冲周期性与功率稳定性等性能要求,对多种光纤光脉冲复制结构的特点进行了分析比较.通过对各种结构的输出脉冲功率、周期性及其影响因素的理论分析,论述了使各种结构的输出脉冲优化的可能性与方法.指出了有源循环式光纤延迟脉冲复制器适合于产生重复周期准确、输出功率大的光脉冲序列.     

编队雷达的脉冲重复间隔低分选设计

射频隐身是先进隐身飞机器的重要特征。低分选脉冲重复间隔设计是提高飞机器雷达射频隐身性能的一条重要途径。文中通过分析累积差值直方图法、序列差值直方图法和脉冲重复间隔变换三种常用脉冲流分选方法,给出了基于脉冲流弱自相关性的低分选设计原则;针对编队雷达之间的同频干扰和脉冲抖动约束,基于脉冲丢失概率提出了脉冲抖动重复间隔约束的编队雷达信号参数低分选设计方法。仿真表明,当脉冲丢失率大于25%或者脉冲抖动量大于7%时,正确分选率都低于80%,说明文中提出的脉冲重复间隔设计模型具有较好的低分选性能。     

大气无线光通信系统中数字脉冲间隔调制研究

基于光强闪烁的大气无线光通信系统模型,研究了数字脉冲间隔调制(DPIM)方式的差错性能,分析了符号结构、发射功率、带宽需求等问题,并与 OOK(开关键控)和 PPM(脉冲位置调制)调制方式进行比较。理论和仿真研究结果表明,DPIM 调制方式较 PPM 方式有较高的功率效率和较少的带宽需求,特别是在系统实现上相对于 PPM 大大简化。因此 DPIM 应用于无线光通信系统具有一定优势。     

大气激光通信中压缩数字脉冲间隔调制技术

为了提高大气光通信信息传输的高效性和可靠性,提出一种压缩数字脉冲间隔调制（CDPIM）技术。该技术对相邻4位信息码组分别经PPM编码后,把编码脉冲之间多余的空闲时隙用分段压缩码进行替换来进行编码。描述了CDPIM的符号结构,运用Matlab对发射功率、频带利用率、信道容量占用率、传输误包率等的仿真结果表明：在相同位分辨率4时,CDPIM的发射功率比FDPIM的发射功率节约23%,CDPIM的频带利用率比DPIM的频带利用率提高72%,CDPIM的传输容量比OOK的传输容量提高67%。在相同信噪比2时,CDPIM的误包率比DPIM的误包率提高60%,而且CDPIM调制技术能对接收的错误码组进行有效的自我纠错。     

时间控制脉冲间隔激光编码方法研究

激光编码是激光半主动制导武器抵抗激光诱偏干扰的重要措施,现有激光编码具有一定的规律性,很容易被干扰系统所识别破解,而使激光半主动制导武器受到威胁。为此,提出了一种基于绝对精确时间控制的激光脉冲激光编码方法。首先利用北斗授时系统对激光编码端授时,以此得到精确时刻,以绝对精确整秒时刻为参数,根据编码基频大小,按照编码函数一次产生当前时刻所需数量的脉冲时间间隔;然后在后续时刻利用定时器在预产生的时间间隔处产生脉冲信号,并控制脉冲宽度;最后对该编码方法的有效性进行了仿真实验和实际实验验证。实验结果表明,授时精度20 ns,脉冲编码精度优于30 ns。该编码最大的特点是各编码脉冲时间间隔各不相同,无任何规律和周期,是一种准随机分布编码,而且编码函数运算量小,易于实现,具有较强的抗解码能力。     

大气激光通信中压缩数字脉冲间隔调制技术

为了提高大气光通信信息传输的高效性和可靠性,提出一种压缩数字脉冲间隔调制( CDPIM)技术。该技术对相邻4位信息码组分别经PPM编码后,把编码脉冲之间多余的空闲时隙用分段压缩码进行替换来进行编码。描述了CDPIM的符号结构,运用Matlab对发射功率、频带利用率、信道容量占用率、传输误包率等的仿真结果表明：在相同位分辨率4时,CDPIM的发射功率比FDPIM的发射功率节约23%,CDPIM的频带利用率比DPIM的频带利用率提高72%,CDPIM的传输容量比OOK的传输容量提高67%。在相同信噪比2时,CDPIM的误包率比DPIM的误包率提高60%,而且CDPIM调制技术能对接收的错误码组进行有效的自我纠错。     

基于单片机及CPLD的多间隔脉冲产生电路

单片机具有逻辑控制功能灵活的特点,复杂可编程逻辑器件(CPLD)具有集成度高、可靠性好及工作速度快的优点,基于二者各自的优点,设计了一种脉宽固定为1μs,周期可调的单头、双头、三头三路脉冲产生电路,该脉冲发生器可实现在脉冲不间断的情况下改变周期,其波形要求精度高、漂移小、抗干扰能力强。     

Steady-state analysis of piecewise-linear systems with periodic inputs

A specific form of a recently proposed algorithm is derived for the rapid determination of the steady-state response of large classes of piecewise-linear systems subjected to periodic inputs. It can be directly incorporated at marginal cost into a computer-oriented state space approach for generating the time domain response of such systems. The algorithm has been successfully applied to several circuits.     

Steady-state analysis of nonlinear circuits with periodic inputs

In the computer-aided analysis of nonlinear circuits with periodic inputs and a stable periodic response the steady-state periodic response is found for a given initial state by simply integrating the system equations until the response becomes periodic. In lightly damped systems this integration could extend over many periods making the computation costly. In this paper a Newton algorithm is defined which converges to the steady-state response rapidly. The algorithm is applied to several nonlinear circuits. The results show a considerable reduction in the amount of time necessary to compute the steady-state response. In addition, the initial iterates give information on the transient response of the system.     

Theory and analysis of leaky coaxial cables with periodic slots

Frequency band and coupling loss are the two important parameters of leaky coaxial cables with periodic slots. The frequency band can be predicted by analyzing the arrangement of the slots on the outer shield of the cable, but the coupling loss is not so easy to determine by classical methods. In this paper, the finite-difference time-domain (FDTD) method is used to calculate the electric field distribution in the slot cut in the outer conductor of the coaxial cable. The dyadic Green's function is then used to calculate the radiation field of the equivalent surface magnetic current densities. By these two methods, the coupling losses of the leaky coaxial cables with different periods, sizes and shapes of the slots can be accurately obtained. Some results in this paper were verified by the experimental results of leaky coaxial cables designed for railway mobile communications with a frequency band of 100-500 MHz     

Three regimes of orotron with two-row periodic structure in the frequency interval 105–234 GHz

The generation in orotron with a two-row periodic structure (period, 0.5 mm; slit-to-period ratio, 0.25; heights of the lower and upper rows, 0.3 and 0.5 mm, respectively; and working voltages, 1500–18500 V) is experimentally studied using several configurations of open resonators. The working regimes employ (i) the second spatial harmonic, (ii) the first spatial harmonic, and (iii) surface waves (BWT regime).     

关于具有"三项式特性"的二元周期序列

本文研究了二元周期序列的“三项式特性”，给出了：1）一个数对可以作为“三项式对”的充要条件；2）序列不存在“三项式对”的条件；3）一个数对是一个序列的“三项式对”的充要条件的另一种描述，这种描述比文献[1]更直观、简洁；4）以给定的数对为“三项式对”的二元周期序列的计数公式和具体的求解方法。     

关于具有"三项式特性"的pm元周期序列

研究了pm元周期序列的“三项式特性”,推广了文献[1]中的结论,并首次给出了求解给定序列的所有“三项式对”的有效算法,从而完美地解决了序列的“三项式特性”的相关问题。     

Analysis of periodic pulse evolutions in a passively mode-lockedring dye laser

Complex pulse evolutions, observed in a passively mode-locked continuous phase modulated ring dye laser, that are highly sensitive to the frequency chirping processes in the laser cavity are investigated. For particular values of intracavity group velocity dispersion, the pulse evolutions are periodic and reminiscent of soliton evolutions. A numerical model of the laser that successfully simulates the qualitative features of the real laser output temporally and spectrally is described. A careful investigation of the numerical model shows that, in the case of strong mode locking, the observed periodic pulse evolutions are not solitonlike, but result from a combination of frequency chirp and spectral walkoff. A distinct regime is identified where solitonlike pulse evolutions are sustained, and the transition between the two modes of operation is related to the strength of the mode locking     

Circular TE01 periodic waveguide as delay line for pulse compression

An iris-loaded circular waveguide 1.3 m long, operating in the low-loss circular TE01 mode, produced 500 ns differential delay for a 50 MHz bandwidth at X band. The insertion loss was 2.2 dB.     

色噪声背景下微弱周期脉冲信号的混沌检测方法

该文将微弱周期脉冲信号引入特定的混沌系统中,以系统相轨迹由混沌状态到大尺度周期状态的跃迁作为微弱周期脉冲信号的检测依据。用特定的混沌系统实现了对强噪声背景下周期脉冲信号的检测,仿真实验表明该混沌检测系统对被强噪声覆盖的周期脉冲信号非常敏感,对任何色噪声均具有极强的抑制能力。