Niho type cross-correlation functions via dickson polynomials and Kloosterman sums

Suppose that n=2k is even. We study the cross-correlation function between two m-sequences for Niho type decimations d=(2/sup k/-1)s+1. We develop a new technique to study the value distribution of these cross-correlation functions, which makes use of Dickson polynomials. As a first application, we derive here the distribution of the six-valued cross-correlation function for s=3 and odd k, up to a term which depends on Kloosterman sums. In addition, applying simpler methods, we prove a theorem providing Niho type decimations with four-valued cross-correlation functions and their distribution. We conjecture that the latter result actually covers all such decimations.     

Binary m-sequences with three-valued crosscorrelation: a proof ofWelch's conjecture

We prove the long-standing conjecture of Welch stating that for odd n=2m+1, the power function x^d with d=2^m+3 is maximally nonlinear on GF(2ⁿ) or, in other terms, that the crosscorrelation function between a binary maximum-length linear shift register sequence of degree n and a decimation of that sequence by 2^m+3 takes on precisely the three values -1, -1±2^m+1     

Wavelength-time codes with maximum cross-correlation function of two for multicode-keying optical CDMA

In this paper, a new family of wavelength-time codes with expanded code cardinality and the maximum cross-correlation function of 2 (i.e., /spl lambda//sub c/=2) is constructed and analyzed. One application of the large code cardinality of our /spl lambda//sub c/=2 codes is multicode-keying wavelength-time optical code division multiple access (O-CDMA), in which each user is allocated with multiple code matrices, instead of just one code matrix in the conventional ON-OFF keying (OOK) O-CDMA. System throughput is increased because a lower baud rate O-CDMA system can be used to support higher bit-rate transmission since each code matrix is used to represent a "symbol" of several data bits. User code confidentiality is improved because of symbol transmission. The performances of two multicode-keying O-CDMA schemes with the new /spl lambda//sub c/=2 wavelength-time codes are also analyzed. The results in this paper show that there is a tradeoff between the performance and the number of code matrices per user.     

On the cross-correlation function of a nonlinear network

It is shown that the shape of the cross-correlation function of a nonlinear network consisting of the cascade connection of a linear network, a memoryless nonlinearity (NL) and a second linear network is independent, in the Gaussian case, of the presence of NL only when NL is not even. An explicit expression for the cross-correlation function of such a system is then given.     

传递函数快速相关法的激光测速技术研究

激光技术测量是实现传送带、热轧钢板等运动物体测速的主要手段，为了改善测量精度和响应速度，提出系统传递相关分析测速技术。采用计算发射端和接收端之间两路信号的系统传递函数进行相关性分析的方法，进行了理论验证和实验分析，得到了相对误差小于0.1%的实验结果。结果表明，利用系统传递函数相关分析构建激光测速系统，代替解调电路，简化信号调理电路，可降低电路部分引起的不确定度；互功率谱函数法实现快速相关分析和频域求得系统传递函数，可提高系统响应速度；合理设置发射端间距，取样积分提高测量信噪比，降低环境引起的不确定度，测量不确定度小于0.2%。该研究对传送带速率的实时测量有一定指导意义。     

新型监测接收机的基本原理和扫描功能

介绍新型监测接收机的变频、数字中频信号处理、中频全景、射频全景等基本原理,进一步分析新型监测接收机的频率扫描、存储扫描、射频全景扫描等功能,最后提出接收机使用中的注意事项。     

基于绝对值差的归一化波形匹配混合算法

基于归一化的波形匹配算法运用十分广泛,但缺点是运算量大。为此提出一种基于绝对值差的归一化混合算法。该算法先将原始波形分解成三层,在每一层分别采用改良的绝对值差法、改良的序列相似性法、归一化互相关法进行匹配,最终实现精确匹配。实验表明,这种混合算法比归一化互相关法在波形匹配速度上有了大幅度的提高。     

REAL SEQUENCES WITH GOOD AUTO-CORRELATION AND CROSS-CORRELATION

New classes of real sequences with good auto-correlation and cross-correlation areconstructed by using sinusoidal functions. The new sequences are better than the FZC and Alltopsequences in two aspects: (1) lower correlations and (2) taking real values. The new sequencescan be used in many areas.     

Interlook cross-correlation function of speckle in SAR images of sea surface processed with partially overlapped subapertures

In the present paper, a general integral expression is derived and discussed for the cross-correlation function (CCF) of speckle patterns in synthetic aperture radar (SAR) images processed by using partially overlapped subapertures of arbitrary Doppler center frequencies (or equivalent azimuth times). It is shown that, under the white noise approximation for the backscattered field, the CCF of the interlook speckle intensity patterns is given by the squared modulus of the autocorrelation function of the amplitude weighting function of subapertures where the time lag is the center time difference. It is also shown that the CCF of the interlook speckle patterns is independent of the surface coherence time of sea surface. The integral expression for the intensity CCF is then evaluated for a rectangular weighting function, and comparison is made with Japanese Earth Resources Satellite-1 (JERS-1) L-band and RADARSAT-1 C-band SAR images of sea surface to test the theory. The CCFs computed from the JERS-1 SAR data show excellent agreement with the theory, and good agreement is obtained with the RADARSAT-1 data.     

Calculation of the local cross-correlation function on the basis ofthe Laguerre transform

A simple and computationally efficient mechanism for calculating a running or local cross-correlation function of two time-domain signals is presented. In order to obtain a running cross-correlation function, the signals must be windowed. It is argued that an appropriate window for a local cross correlation is an exponential function. To obtain a computationally efficient mechanism, the windowed functions are decomposed in a series of orthogonal functions. The set or orthogonal functions is matched to the chosen window and is a Laguerre-Fourier series. The cross correlation of the windowed functions is equal to a weighted summation of cross-correlated pattern functions. The weights are determined by cross correlating the Laguerre coefficients     

A new polyphase sequence with perfect even and good odd cross-correlation functions for DS/CDMA systems

A class of polyphase signature sequences for direct-sequence code-division multiple-access (DS/CDMA) systems is proposed. The proposed class has zero periodic (=even) cross-correlation (CC) function and approximate maximum magnitude N//spl pi/ of odd cross-correlation (OCC), where N is the length of sequences. Although the maximum magnitude is relatively large, it is observed that the maximum magnitude has little effect on the performance of the DS/CDMA system, since its frequency is very low. The performance of the proposed sequence in DS/CDMA systems is investigated and shown to be better than that of other sequences for an asynchronous additive white Gaussian noise channel environment with and without Rayleigh multipath fading.     

Optical orthogonal codes with unequal auto- and cross-correlation constraints

An optical orthogonal code (OOC) is a collection of binary sequences with good auto- and cross-correlation properties; they were defined by Salehi and others as a means of obtaining code-division multiple access on optical networks. Up to now, all work on OOCs have assumed that the constraint placed on the autocorrelation and that placed on the cross-correlation are the same. We consider-codes for which the two constraints are not equal. Specifically we develop bounds on the size of such OOCs and demonstrate constriction techniques for building them. The results demonstrate that a significant increase in the code size is possible by letting the autocorrelation constraint exceed the cross-correlation constraint. These results suggest that for a given performance requirement the optimal OOC may be one with unequal constraints. This paper also views OOCs with unequal auto- and cross-correlation constraints as constant-weight unequal error protection (UEP) codes with two levels of protection. The bounds derived are interpreted from this viewpoint.<>     

Simulation of Nakagami fading channels with arbitrary cross-correlation and fading parameters

Nakagami fading model is widely used in modeling wireless communication systems. In this paper, we present methods to generate Nakagami fading signals with arbitrary cross-correlation and fading parameters by taking the square root of correlated Gamma random variables (RVs) with the corresponding shape parameters. To generate correlated Gamma RVs with different noninteger values of m-parameters, two methods, namely the decomposition method and Sim's method, are proposed. The former is more flexible and efficient. The latter is mathematically exact but carries constraints on the permissible simulation parameters. Simulations show that both methods produce outputs that match well with the specifications.     

A new type of transistor: CBT

A transistor called the channel-base transistor (CBT), which is constructed by making channels through the base of the conventional bipolar junction transistors (BJTs), is proposed. In principle, a CBT can be treated as a combination of a BJT and a normally-off junction-type field-effect transistor (E-JFET). Silicon planer CBTs have been fabricated with BJTs on the same wafer for comparison. The electrical characteristics of CBTs are similar to those of a conventional BJTs, but the variations of current gain with temperature and emitter current in CBTs are much less than those in the BJTs. In addition, the magnitude of current gain of CBTs is higher than that of comparable BJTs. Transistor-transistor-logic (TTL) NAND-gate ICs implemented with CBTs have been fabricated. The temperature variations of parameters in CBT ICs are less than those in BJT ICs. Experiments have shown that silicon CBT discrete devices and ICs can be used over a wide range of temperatures from -60°C to 200°C. Experimental and theoretical analysis results for CBTs are presented     

一种新型可控硅固态调压装置

本文介绍了一种利用可控硅相控整流技术调节电压的方法及实用装置。对组成调压装置的主要电路的设计思想和工作原理作了简要分析。并结合该装置的实际应用介绍了一些优点并提出了自己的看法。     

Device with a new type of current-voltage characteristic

A new type of unijunction transistor device has been discovered. This is suitable for use in integrated circuits and resembles a metal-oxide-silicon field-effect transistor.     

Adaptive JPEG steganography with new distortion function

This paper presents an adaptive steganographic scheme in JPEG images by designing a novel distortion function. While some previous works employed distortion functions based on coefficient difference, we point out that the data embedding on coefficients with larger absolute values may cause less steganalytic detectability. In the proposed scheme, the distortion function is derived from both the coefficient residual and coefficient value, which measures the risks of detection due to the modification on cover data. With an exhaustive searching method, the parameters of the proposed distortion function are optimized. Then, we may employ syndrome trellis coding to embed the secret data into JPEG images when keeping a low risk. This way, the modifications are forced into high textured areas in JPEG images, and experimental results demonstrate that the steganographic security is improved by the designed distortion function.     

Some experiments with a new type of crossed-field gun

The construction and testing of a crossed-field gun based on an exact space-charge flow solution will be described. All the characteristic parameters of a gun of this type may be obtained analytically. Experimentally the gun was found to perform essentially as predicted. This gun has a moderately high convergence and produces a beam whose gross features give a very good approximation to planar Brillouin flow. Work by Anderson has indicated that crossed-field beams produced by a gun of this type may be somewhat less noisy than similar beams produced by other types of guns.     

CameraCube新型图像传感技术

随着消费者对于体积更小、功能更丰富的可携式装置需求口益殷切,数码图像市场也持续展现微型化的趋势.这个趋势也为更为轻薄短小的高品质低成本行动相机带来了更大的需求.为了因应成熟数码图像市场的需求,一些图像传感器厂商也加快速度提升其面素、镜头与封装技术的核心能力.     

A new type photonic crystal fiber with high birefringence

Highperformancepolarization maintainingfibers (PMFs)havepotentialforanumberofapplicationssuchashighbitratecommunicationsystem,PMfibre loopsforgyroscopesandsoon.Theindex guidingPCFs arecharacterizedbyaseriesofholesrunningthroughou thelengthofthefiberarrangedinamicroscalestructurearoundahighindexcore.Thisoffersanewpossibilityto createhighbirefringenceintheindex guidingPCFs,be causethestack and drawprocessallowstheformationoftherequiredsymmetricorasymmetricmicrostructure andtheindexcontrasto…