Application of classical cosine series window functions to fullresponse signaling offset quadrature binary modulation systems

It is proposed that classical cosine series window functions be applied to finite symbol duration quadrature binary modulation systems as pulse shapes in the interest of increasing the spectral confinement of the resulting modulated signals. The respective modulation systems are analyzed in terms of modulated signal envelope uniformity, spectral confinement, and bit error rate in the presence of white Gaussian noise with varying degrees of modulated signal amplitude compression. Even in the presence of moderate modulated signal compression, classical cosine series window function pulse shapes offer spectral confinement for quadrature binary modulation systems that is equal to or better than that provided by the conventional pulse shapes corresponding to QPSK, MSK, SFSK, and DSFSK. It is shown that moderate levels of modulated signal compression have negligible effects on the system bit error rate. A system implementation using the sum of FSK modulated signal components to achieve spectral confinement based on the classical cosine series window functions is presented     

Effect of velocity mismatch and microwave attenuation ontime-domain response of traveling-wave electrooptic modulators

The dynamic response of a traveling-wave (TW) electrooptic phase modulator is treated using a Fourier transform technique. An integral expression for the induced phase shift which takes into account the optical-microwave velocity mismatch and the microwave attenuation is derived. In the case of a Gaussian modulating pulse and negligible microwave attenuation, the temporal dependence of the modulated pulse amplitude can be expressed in terms of error functions. Calculated pulse shapes showing the transition from a Gaussian to a flat top output pulse with increasing phase mismatch in the absence of microwave attenuation are presented. The effect of microwave attenuation on pulse shape, amplitude, and width is also explored. The method used to obtain these results is generally applicable to the time-domain analysis of TW modulators     

Minimisation of timing jitter in CDMA code tracking

A method for chip waveform design that minimises the tracking jitter in code division multiple access (CDMA) synchronisation is presented. The method is based on the use of prolate spheroidal wave functions. Examples of optimised waveforms are given and their performance compared to other conventional pulse shapes in terms of timing error variance and bandwidth occupancy.     

Theory and methods for design of pulse shapes for broadcastteletext

The theoretical and practical engineering constraints, considerations, and methods for pulse shape design for North American broadcast teletext transmissions are described. The principles and concepts described are for broadcast over-the-air transmission, but they are also applicable to satellite and cable transmission of broadcast teletext signals. Overall objectives of pulse shape design are summarized. Basic constraints and considerations from the Nyquist theory are described. The practical and engineering constraints on teletext pulse shapes are discussed in detail. Pulse shape apportioning and specification are treated. A critical review is provided of the theory and design methods for teletext pulse shaping. A review of analytical and numerical approaches is given. Modelling and simulation approaches are described, including novel comprehensive model. Improved overall and transmitted pulse shapes are evaluated and their performance compared to that obtained with other common pulse shapes     

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     

On the power spectral density of certain digitally modulatedsignals with applications to code despreading

Techniques for deriving the power spectral density (PSD) of certain digitally modulated signals that are more general and easier to use than other similar methods are developed. These techniques are especially well suited for deriving the PSD of signal-product waveforms with arbitrary modulating pulse shapes. This is done by decomposing the PSD expression into two factors, one depending solely on the underlying sequences and the other depending only on the pulse shapes. General formulas are derived and, for some cases, they are expressed in terms of the discrete Fourier transform of appropriately defined sequences and the Fourier transform of the modulating pulse shape. Applications where these expressions would be useful include bit and code synchronizers, delay-and-multiply-type of detectors, and spread-spectrum and code-division multiple-access systems, either at radio or at optical frequencies     

相遇时间对双布里渊放大池放大控制脉冲波形的影响

在传统独立双池结构的受激布里渊散射(SBS)相位共轭镜(PCM)系统中,对布里渊放大池进行改进。引入修整放大池,采用主放大池与修整放大池相结合的双布里渊放大池结构控制脉冲波形,主放大池对脉冲波形进行粗调,修整放大池对脉冲波形,特别是脉冲前沿进行微调。理论和实验研究了相遇时间对双布里渊放大池放大控制脉冲波形的影响,得到了不同相遇时间下,脉冲波形随双池间距的变化规律。研究表明,相遇时间是决定放大光脉冲波形整体形状的重要参数,相遇时间越长,脉冲可控范围越大,但是系统的效率越低。     

The Polarizabilities of Electrically Small Apertures of Arbitrary Shape

Numerical procedures, based on a method of moments approach, are given for computing the magnetic and electric polarizabilities of electrically small apertures of arbitrary shape. The magnetic polarizability density is determined through the use of pulse expansion functions defined over quadrilateral subdomains, while the electric polarizability density is obtained by using basis functions, each of which consists of a piecewise arrangement of simple linear functions defined over triangles and having an area coordinate representation. All the subdomains are generated automatically by applying either the Gordon-Hall or the Zienkiewicz-Phillips subdivision techniques. Computed results are obtained for several aperture shapes, including the circle and the ellipse. The calculations for the last two cases are in excellent agreement with the exact values.     

V型振子脉冲天线的形状优化

在大多数脉冲电磁场的应用中，需要能在空间某一方向上产生最强瞬时冲击脉冲的天线，为了这一目的，本文中用时间步进法对曲线形状偶极子天线的时域辐射特性进行了分析，并在此基础上用共轭梯度法对天线的形状进行了优化。优化过程的目标函数为天线前向辐射脉冲的瞬时冲击值，优化变量为天线的形状参数。     

ICI Reduction in OFDM System Using IMBH Pulse Shapes

In this paper, the Improved Modified Bartlett-Hanning (IMBH) window family is used in an OFDM system to reduce the ICI. It is found that the IMBH pulse shape gives better results than the PMSP, ISP, BTRC, RC, Bartlett and rectangular pulse shapes in terms of both ICI and BER. The optimization of SIR in terms of window parameters has also been obtained. This analysis provides a better insight to control ICI or BER with proposed pulse shape. The IMBH pulse shapes give an improvement of 2–3 dB in ICI with different frequency offsets and roll-off factors. Similarly, with proposed pulse shapes the BER level can be obtained at lower SNR of approximately 5 dB. Therefore, the IMBH pulse shapes outperform other reported pulse shapes in both the dimensions, i.e., ICI and BER.     

Wavelet packet modulation for orthogonally multiplexedcommunication

Utilizing multidimensional signaling techniques, a generalized multirate wavelet-based modulation format for orthogonally multiplexed communication systems is presented. Wavelet packet modulation (WPM) employs the basis functions from an arbitrary pruning of a dyadic tree structured filter bank as orthogonal pulse shapes for conventional quadrature amplitude modulation (QAM) symbols. This generalized framework affords an entire library of basis sets with increased flexibility in time-frequency (T-F) partitioning. The bandwidth efficiency and power spectral density figures of merit for the general signal are derived and shown to be that of standard QAM     

Space vector-based analytical analysis of the input currentdistortion of a three-phase discontinuous-mode boost rectifier system

In this paper the low frequency harmonic distortion of the mains current of a three-phase single-switch discontinuous-mode boost-rectifier is calculated. The system analysis is based on application of space vector calculus and on substitution of discontinuous time shapes within a pulse period by quasicontinuous time shapes. The quasicontinuous time shapes are defined by averaging over the pulse period. The dependency of the shape of the input currents on the voltage transformation ratio is given for various control methods in analytical form. The results of the theoretical analysis are verified by digital simulation and by measurements on a laboratory model. A good consistency of the results has been found     

An Experimental Investigation of the Distribution of Current And Charge Induced on a Tubular Conducting Cylinder by an Electromagnetic Pulse

The distribution of current and charge induced on a tubular cylinder by an electromagnetic pulse (EMP) is investigated experimentally in the Harvard parallel-plate EMP simulator (HES). The pulse shapes of the current and charge induced on the surface of the cylinder are measured. After Fourier transforms of the observed pulse shapes are taken, the distributions of the several frequency components on the surface are obtained. The measured distribution of each frequency component is then compared with the theoretical distribution calculated using Kao's method.     

Pulse Shape Design for Teletext Data Transmission

This paper studies the problem of designing a suitable pulse shape for teletext data transmission. The following four criteria are used: 1) Nyquist I criterion, 2) Nyquist II criterion, 3) degree of overshoots in the channel signal, and 4) robustness to sampling phase jitter. For system bandwidths less than the inverse-baud rate, it is not possible to satisfy all these criteria simultaneously; tradeoffs that have to be made are illustrated. Several candidate pulse shapes are given and a composite criterion developed. A pulse shape, which satisfies the Nyquist I criterion and is closest to satisfying the Nyquist II criterion, in a sum-of-squares-of-deviations sense, is recommended.     

五阶非线性下不同形状脉冲对的交叉相位调制

为了探讨光纤中五阶非线性下不同形状光脉冲对的交叉相位调制特性,从包含五阶非线性效应的扩展耦合非线性薛定谔方程组出发,导出了不同形状光脉冲对的非线性相移和频率啁啾公式。计算并比较了它们的相移、啁啾和功率频谱。结果表明,较强的负五阶非线性对相移、啁啾和频谱曲线中心附近的形状有较大的影响,而正五阶(较弱的负五阶)非线性则只使相移和啁啾量增大(减小),使频谱变宽(变窄)、谱峰变多(变少)。孤子对和高斯对的谱形相似,随五阶非线性系数的不同,能量最强的谱峰可能在中央附近也可能在最边缘处。各阶超高斯对的谱形也相似,但能量大部分集中在中央峰处。研究对光脉冲压缩、光开关器件和光纤通信系统性能的提高等有一定的意义。     

Filtering Allocation in Teletext Data Transmission Under Power and Peak Constraints

Various pulse shapes have been proposed for teletext data transmission. The effect of apportioning the different pulse shapes between the transmitter and the receiver is studied for the cases of a constraint on the power and a constraint on the peak value of the channel signal.     

Pulse Waveform Degradation Due to Dispersion in Waveguide

Phase velocity in a waveguide is a nonlinear function of frequency and thus causes dispersion of the spectral components in a pulse waveform. For most practical cases, it is a good assumption to consider the phase constant to be a quadratic function of frequency. An expression can then be derived for the exit waveform shape as a function of guide length, dispersion, and width of the input rectangular pulse. The derived expression is given in terms of tabulated error functions and Fresnel integrals. It is universal in form and applicable to a wide range of practical problems, A family of degraded shapes has been computed from this expression and is presented graphically. The results apply for any mode in a straight waveguide of arbitrary but constant cross section.     

Different pulse shapes to obtain small fiber selective activation by anodal blocking--a simulation study

The aim of this study was to investigate whether it is possible to reduce a charge per pulse, which is needed for selective nerve stimulation. Simulation is performed using a two-part simulation model: a volume conductor model to calculate the electrical potential distribution inside a tripolar cuff electrode and a human fiber model to simulate the fiber response to simulation. Selective stimulation is obtained by anodal block. To obtain anodal block of large fibers, long square pulses (> 350 micros) with a relatively high currents (1-2.5 mA) are usually required. These pulses might not be safe for a long-term application because of a high charge per pulse. In this study, several pulse shapes are proposed that have less charge per pulse compared with the conventional square pulse and would therefore be safer in a chronic application. Compared with the conventional square pulse, it was possible to reduce the charge with all proposed pulse shapes, but the best results are obtained with a combination of a square depolarizing pulse and a blocking pulse. The charge per pulse was up to 32% less with that pulse shape than with a square pulse. Using a hyperpolarizing anodal prepulse preceding a square pulse, it was not possible to block nerve fibers in a whole nerve bundle and to obtain reduction of a charge per phase. Reduction of the charge could be achieved only with spatially selective blocking. The charge per phase was larger for the combination of a hyperpolarizing anodal prepulse and a two-step pulse than for the two-step pulse alone.     

Cross-correlation studies of pulses from the double mode-locked CW dye laser

A detailed investigation of the dual-wavelength pulse trains from the double mode-locked CW dye laser is made using cross-correlation measurements. Direct displays of pulse shapes and of the system jitter distribution are experimentally determined on a picosecond time scale. Techniques for determining the relative time of generation between the two double mode-locked pulse trains are also demonstrated. A variety of operating modes for this system is discussed in detail, providing further insight into the fundamental mechanisms involved in the production of the two pulse trains.     

Multi‐carrier platform for wireless communications. Part 1: High‐performance,high‐throughput TDMA and DS‐CDMA via multi‐carrier implementations

Multi‐carrier technologies in general, and OFDM and MC‐CDMA in particular, are quickly becoming an integral part of the wireless landscape. In this first of a two‐part survey, the authors present the innovative transmit/receive multi‐carrier implementation of TDMA and DS‐CDMA systems. Specifically, at the transmit side, the pulse shape (in TDMA) and the chip shape (in DS‐CDMA) corresponds to a linear combining of in‐phase harmonics (called a CI signal). At the receiver side, traditional time‐domain processing (equalization in TDMA and RAKE reception in DS‐CDMA) is replaced by innovative frequency based processing. Here, receivers decompose pulse (or chip) shapes into carrier subcomponents and recombine these in a manner achieving both high frequency diversity gain and low MAI. The resulting system outperforms traditional TDMA and DS‐CDMA systems by 10–14 dB at typical BERs, and, by application of pseudo‐orthogonal pulse shapes (chip shapes), is able to double system throughput while maintaining performance gains of up to 8 dB. Copyright © 2002 John Wiley & Sons, Ltd.