基于角度参数特定边界值的旋转交叉眼干扰容限研究

在干扰平台旋转或者被不同方向的雷达探测情况下,该文对传统反向交叉眼和正交四点源反向交叉眼进行了容限分析。在分析过程中引入了角度参数的概念,同时提出角度参数特定边界值(AFSBV)作为评估两种方案性能的指标。进一步推导得出角度参数特定边界值关于相位偏移和幅度增益的闭合解,在干扰平台旋转角取值不断变化时,得出角度参数特定边界值的最大值。这一结论能指导交叉眼干扰工程实践中相位和幅度的取值范围,使系统能满足所有干扰平台旋转或者被不同方向的雷达探测情况。     

A new fast locking charge pump PLL: analysis and design

In this paper a new structure for a fast locking charge pump phase locked loop (CPPLL) is introduced which overcomes the trade-off between the settling time and overshoot of the system. This fast locking PLL uses an auxiliary bang–bang frequency comparator (BBFC) as a lock-aid. An additional charge pump current controlled by the output of the BBFC is injected into the main loop filter capacitor to accelerate the locking process. An analytical approach to extract the differential equation governing on the system’s dynamics is used to evaluate the performance of this fast locking PLL. A heuristic method that results in an approximate solution for the extracted differential equation is also proposed. The correctness of the presented differential equation and its closed-form solutions are verified by comparing the obtained closed-form solutions and simulation results. Using the obtained closed-form solutions, we predict the behavior of the system and design a fast BBFC-CPPLL which meets the system’s requirements. Correctness of the differential equation and its closed-form solutions are verified by comparing the obtained closed-form solutions and simulation results.     

Solutions to Infinite Integrals of Gaussian Q-Function Products and Some Applications

Infinite integrals involving the products of two and three Gaussian Q-functions of different arguments are solved in closed-form. These solutions provide novel expressions in the error rate analyses of signals such as general rectangular quadrature amplitude modulation, differentially encoded quaternay phase shift keying and new solutions for the error rate of the repetition code. As an example, closed-form expressions for the average symbol error rates of general rectangular quadrature amplitude modulation and the repetition code are obtained for a Nakagami-m fading channel.     

Reflection of femtosecond optical pulses from multiple-layer dielectric mirrors--Analysis

We present an analytical treatment of the reflection of femtosecond pulses from broad-band multiple-layer dielectric mirrors. In particular, closed-form expressions are given for the reflected pulse amplitude which includes the dispersive effect of the cubic phase term. It is shown that this term is still insufficient to accurately describe certain experimental results obtained with 20-fs optical pulses. We introduce an alternative technique which describes the phase branches analytically and yields accurate closed-form expressions for the reflected pulse amplitude in terms of complementary error functions having real or complex arguments.     

On the outage probability of large scale decode-and-forward relay wireless networks

This paper considers a wireless network consisting of large number of clusters, wherein each cluster represents a decode-and-forward (DF) relay network. Two main scenarios according to the distances among the nodes in the network are investigated. In the case of deterministic distances, the outage probability is obtained in a closed-form expression. Whereas for the case when these distances are independent random variables, the framework of Stochastic Geometry (SG) is exploited for deriving the closed-form of the outage probability in case of Rayleigh fading channel. Furthermore, a lower and upper bound for the outage probability in case of general fading channel have been also provided. Numerical simulations are carried out to validate the derived analytical expressions, and to illustrate how the obtained results can be utilized in interference management of such networks.     

Soft-Decision Metrics for Coded Orthogonal Signaling in Symmetric Alpha-Stable Noise

This paper derives new soft-decision metrics for coded orthogonal signaling in impulsive noise, more specifically symmetric alpha-stable noise. For the case of a known channel amplitude and known noise dispersion, exact metrics are derived both for Cauchy and Gaussian noise. For the case that the channel amplitude or the dispersion is unknown, approximate metrics are obtained in closed-form based on a generalized-likelihood ratio approach. The performance of the new metrics is compared numerically for a turbo-coded system, and the sensitivity to side information of the optimum receiver for Cauchy noise is considered. The gain that can be achieved by using a properly chosen decoding metric is quantified, and it is shown that this gain is significant. The application of the results to frequency hopping ad hoc networks is also discussed.     

Closed-Form Expressions of Multilayered Planar Green's Functions That Account for the Continuous Spectrum in the Far Field

The rational function fitting method has been found useful in the derivation of closed-form expressions of spatial-domain Green's functions for multilayered media. However, former implementations of the rational function fitting method lead to Green's functions expressions that are not accurate in the far field when this far field is dominated by the continuous spectrum instead of being dominated by surface waves (as it happens, for instance, in the case of lossy multilayered media). In this paper, the authors introduce a novel implementation of the rational function fitting method, which leads to Green's functions expressions that are accurate in the far field when this is dominated either by the continuous spectrum or by surface waves. In the new approach, the far-field contribution of the continuous spectrum to the Green's functions is numerically fitted in terms of functions with closed-form Hankel transforms, and this far-field contribution is explicitly added to the total least squares approximations of the Green's functions. The numerical results obtained for the Green's functions with the new approach have been compared with numerical results obtained via direct numerical integration of Sommerfeld integrals, and excellent agreement has been found despite the contribution—continuous spectrum or surface waves—dominating the far field.      

Analysis of LMS-Newton adaptive filtering algorithms with variableconvergence factor

An analysis of two LMS-Newton adaptive filtering algorithms with variable convergence factor is presented. The relations of these algorithms with the conventional recursive least-squares algorithm are first addressed. Their performance in stationary and nonstationary environments is then studied and closed-form formulas for the excess mean-square error (MSE) are derived. The paper deals, in addition, with the effects of roundoff errors for the case of fixed-point arithmetic. Specifically, closed-form formulas for the excess MSE caused by quantization are obtained. The paper concludes with experimental results that demonstrate the validity of the analysis presented     

Error rates for Nakagami-m fading multichannel reception of binaryand M-ary signals

This paper derives new closed-form formulas for the error probabilities of single and multichannel communications in Rayleigh and Nakagami-m (1960) fading. Closed-form solutions to three generic trigonometric integrals are presented as part of the main result, providing a unified method for the derivation of exact closed-form average symbol-error probability expressions for binary and M-ary signals with L independent channel diversity reception. Both selection-diversity and maximal-ratio combining (MRC) techniques are considered. The results are generally applicable for arbitrary two-dimensional signal constellations that have polygonal decision regions operating in a slow Nakagami-m fading environments with positive integer fading severity index. MRC with generically correlated fading is also considered. The new expressions are applicable in many cases of practical interest. The closed-form expressions derived for a single channel reception case can be extended to provide an approximation for the error rates of binary and M-ary signals that employ an equal-gain combining diversity receiver     

On filtered binary processes

The problem of calculating the probability density function of the output of anRCfilter driven by a binary random process with intervals generated by an equilibrium renewal process is studied. New integral equations, closely related to McFadden's original integral equations, are derived and solved by a matrix approximation method and by iteration. Transformations of the integral equations into differential equations are investigated and a new closed-form solution is obtained in one special case. Some numerical results that compare the matrix and iteration solutions with both exact solutions and approximate solutions based upon the Fokker-Planck equation are presented.     

Probability density functions for multilook polarimetric signatures

Derives closed-form expressions for the probability density functions (PDF's) for copolar and cross-polar ratios and for the copolar phase difference for multilook polarimetric SAR data, in terms of elements of the covariance matrix for the backscattering process. The authors begin with the case in which scattering-matrix data are jointly Gaussian-distributed. The resulting copolar-phase PDF is formally identical to the phase PDF arising in the study of SAR interferometry, so the authors' results also apply in that setting. By direct simulation, they verify the closed-form PDF's. They show that estimation of signatures from averaged covariance matrices results in smaller biases and variances than averaging single-look signature estimates. They then generalize their derivation to certain cases in which backscattered intensities and amplitudes are K-distributed. They find in a range of circumstances that the PDF's of polarimetric signatures are unchanged from those derived in the Gaussian case. They verify this by direct simulation, and also examine a case that fails to satisfy an important assumption in their derivation. The forms of the signature distributions continue to describe data well in the latter case, but parameters in distributions fitted to (simulated) data differ from those used to generate the data. Finally, the authors examine samples of K-distributed polarimetric SAR data from Arctic sea ice and find that their theoretical distributions describe the data well with a plausible choice of parameters. This allows the authors to estimate the precision of polarimetric-signature estimates as a function of the number of SAR looks and other system parameters     

Effects of carrier phase error on EGC receivers in correlated Nakagami-m fading

The effects of incoherently combining on dual-branch equal-gain combining (EGC) receivers in the presence of correlated, but not necessarily identical, Nakagami-m fading and additive white Gaussian noise are studied. Novel closed-form expressions for the moments of the output signal-to-noise ratio (SNR) are derived. Based on these expressions, the average output SNR and the amount of fading are obtained in closed-form. Moreover, the outage and the average bit error probability for binary and quadrature phase-shift keying are also studied using the moments-based approach. Numerical and computer simulation results clearly depict the effect of the carrier phase error, correlation coefficient, and fading severity on the EGC performance. An interesting finding is that higher values of the correlation coefficient results to lower irreducible error floors.     

A Binary Quantized Digital Phase Locked Loop: A Graphical Analysis

A non-uniform sampling digital phase locked loop (DPLL), with a hard limiter as quantizer, is analyzed by a graphical method in the case of phase and frequency step inputs and no noise. The cycle slipping and the limit cycles phenomena are investigated. An upper-bound to the model gain and, consequently, to the pull-in range is obtained. Also a closed-form expression of acquisition time is derived. Moreover, using a random-walk model, the stationary phase error variance, the mean acquisition time and the mean first slip time have been evaluated. Some two channel configurations are proposed, which allow us to obtain a faster acquisition. Finally the problems relevant to the practical implementation of the loop are analyzed.     

Analysis and optimization of pilot symbol-assisted Rake receivers for DS-CDMA systems

The effect of imperfect channel estimation (CE) on the performance of pilot-symbol-assisted modulation (PSAM) and MRC Rake reception over time- or frequency-selective fading channels with either a uniform power delay profile (UPDP) or a nonuniform power delay profile (NPDP) is investigated. For time-selective channels, a Wiener filter or linear minimum mean square error (LMMSE) filter for CE is considered, and a closed-form asymptotic expression for the mean square error (MSE) when the number of pilots used for CE approaches infinity is derived. In high signal-to-noise ratio (SNR), the MSE becomes independent of the channel Doppler spectrum. A characteristic function method is used to derive new closed-form expressions for the bit error rate (BER) of Rake receivers in UPDP and NPDP channels. The results are extended to two-dimensional (2-D) Rake receivers. The pilot-symbol spacing and pilot-to-data power ratio are optimized by minimizing the BER. For UPDP channels, elegant results are obtained in the asymptotic case. Furthermore, robust spacing design criteria are derived for the maximum Doppler frequency.     

Mitigation of transmit correlation for TIMO spatial multiplexing through phase rotation

In MIMO wireless communications, spatial multiplexing can be employed to achieve a high data rate. However, its performance can be degraded by spatial correlation between the transmit antennae. Hence, a simple closed-form linear precoder is proposed to improve performance when two transmit antennae are exploited at the transmitter. The proposed precoder rotates the constellation by a certain phase angle, which can be easily obtained from the correlation matrix of the channel. The simulation results show that the proposed algorithm can achieve near- optimal performance with remarkably reduced computational complexity due to the closed-form solution.     

Analysis of Four Decision-Feedback Carrier Recovery Loops in the Presence of Intersymbol Interference

The performance of four decision-feedback carrier recovery techniques is evaluated in the presence of additive noise and intersymbol interference (ISI). For QAM signal constellations, a closed-form expression is given for the phase jitter variance (PJV) of each loop, and the loop tracking performance is examined. The analytic results are then computed in the case of a 16 QAM digital radio system subjected to multipath fading. Two cases are considered: in the first case no countermeasure techniques are used against selective fading, while in the second case a three-coefficient decision-feedback equalizer (DFE) is used. Computer simulations using a pseudorandom sequence to estimate loop performance are also reported which support the theoretical results.     

Phase compensation on an OTA-C integrator for high-frequency continuous-time filters

A phase compensation technique for an OTA integrator is presented. A closed-form design equation is given which offers a simple way to implement the desired zero. SPIC simulation confirmed the analytical results obtained.<>     

On the average crossing rates in selection diversity

This letter presents new results on the average crossing rate of the combined signal of a selection diversity in Rayleigh fading channels. Exact closed-form expressions are derived for the inphase zero crossing rate, inphase rate of maxima, phase zero crossing rate, and the instantaneous frequency zero crossing rate of the output of the selection combiner. The utility of the new theoretical formulas, validated by Monte Carlo simulations, are briefly discussed as well     

Closed-Form Expressions for the Current Densities on the Ground Planes of Asymmetric Stripline Structures

In this paper, closed-form expressions for the current density on the ground planes of an asymmetric stripline structure are derived. The derivation utilizes image theory in order to obtain a suitable quasi-static Green's function for this asymmetric geometry. For the special case of a symmetric stripline geometry and the limiting case of a microstrip line, it is demonstrated that the results obtained here reduce to previously derived results. As expected, it is illustrated that the current densities on the ground planes of an arbitrary asymmetric stripline are bounded by the current distribution of a symmetric stripline and that of a microstrip line. The validity of the analytical results is investigated by comparing to numerically obtained results. Finally, expressions are presented for the total ground-plane currents as fractions of the total current on the signal trace     

Extension of phase correlation to subpixel registration

In this paper, we have derived analytic expressions for the phase correlation of downsampled images. We have shown that for downsampled images the signal power in the phase correlation is not concentrated in a single peak, but rather in several coherent peaks mostly adjacent to each other. These coherent peaks correspond to the polyphase transform of a filtered unit impulse centered at the point of registration. The analytic results provide a closed-form solution to subpixel translation estimation, and are used for detailed error analysis. Excellent results have been obtained for subpixel translation estimation of images of different nature and across different spectral bands.