Spectral Energy Distribution of Radio Link FM

The series expansion for the energy distribution of quasi-niose-modulated and arbitrarily preemphasized FM signals is being derived. Computer evaluations for the CCIR multichannel preemphasis in the range applicable to systems between 12- and 1800-channel loading show that not the total phase deviation but the deviation ηtopof the upper baseband portion is the quantity governing the energy density beyond 1.5 times base bandwidth off the carrier frequency. The interference into the adjacent channel is computed and a channel spacing formula is deducted based on an interference level equivalent to 3 pW. The formula isB_{n} = 3M + 1KD, whereMis the highest baseband frequency,Ka factor between 0 and 1, andDthe peak frequency deviation obtained with peak factor of 9 dB.     

Cyclic spectral analysis of continuous-phase modulated signals

Continuous-phase modulated (CPM) signals play a prominent role in modern communication systems due to their desirable constant-modulus property and the ability to control their power and bandwidth efficiencies. Popular CPM signals include the classical minimum-shift keyed (MSK) signal, the LREC family of signals also known as continuous-phase frequency-shift-keyed (CPFSK) signals, and Gaussian MSK, which is used in state-of-the-art GSM and PCS mobile communication systems. CPM signals, like virtually all man-made communication signals, are known to exhibit cyclostationarity, which implies that their probabilistic parameters, such as mean, second moment, and higher order cumulants, are almost-periodic functions of time. A novel representation of CPM signals as a sum of PAM signals is presented for both integer and noninteger modulation index cases. Then, the Nth-order cyclostationarity properties of binary CPM signals are derived in terms of Nth-order temporal and spectral moment and cumulant functions. Moreover, the case of M-ary CPM signals is briefly addressed. The results are illustrated with simulations involving MSK, LREC, and GMSK signals     

Spectral Analysis of Analog Video and Phase-Shift-Keying Data Transmitted by FM

Models of the video luminance and chrominance processes are presented and used to derive an expression of the FM power spectrum of colour TV signals. The proposed spectrum model accounts for the spectral components at the chroma subcarrier frequency and agrees closely with the measured spectrum.     

A multilevel approach toward quadrupling the density of flashmemory

A multilevel scheme is presented that explores the possibility of quadrupling flash EEPROM storage density. Sixteen levels (4 bits/cell) of charge are stored in existing NOR stacked gate devices. A distinction is made between logical threshold voltages (as seen by the sense amplifier) and transistor threshold voltages (as defined by the gate characteristics), and precise programming gives distinct logical threshold voltage distributions, whereas transistor threshold voltage distributions are contained in a small 2.5 V range and kept low so that logical distributions survive a ten-year equivalent data retention bake     

广安电厂一次调频功能试验及应用

本文主要是对四川广安电厂300MW机组的一次调频功能原理、组成、应用及试验方法进行了介绍.     

Spectral method of Boolean function complexity

A common measure of Boolean function complexity is transformed to the Rademacher/Walsh spectral domain. The resulting spectral measure has an appealing visual interpretation not found in the functional domain. The relevance of this spectral measure to spectral translation and to the testability of certain classes of combinational networks is examined.     

伪码-载波调频侦察信号识别的谱相关方法(Ⅱ)伪码-载波调频信号的调制识别和参数估计

研究了伪码-载波调频侦察信号识别的谱相关方法,具体针对伪随机二相编码(PRBC)信号及其与正弦调频和线性调频复合信号作了研究。通过3种复合信号循环谱截面谱相关特征的分析和提取,完成了调制类型的自动识别,估计了载频和载波调频参数,对伪随机码信号的各项参数进行了估计。分析了噪声环境和有限采集时间对参数估计的影响,最后对调制识别和参数估计进行仿真分析,表明了谱相关方法在伪码-载波调频信号识别中的优势。     

Spectral density of noise generated in charge transfer devices

We calculate the spectral density of the noise added to an analog signal passed through a charge transfer device (CTD) in terms of the charge fluctuation associated with each transfer. A correlation between noise in neighboring elements substantially suppresses the energy content of the noise associated with charge transfer for frequencies much less than the clock frequency.     

Spectral density of random signals corrupted by multiplicative noise

A simple method of evaluating the spectral density of stationary random signals corrupted by multiplicative noise is presented. It is assumed that the multiplicative noise is also stationary, and that it is statistically independent of the signal.     

Noise immunity for continuous-phase pulse-frequency modulation in the presence of low-intensity noise

The minimum mean-square error that can be attained in demodulating a c.p.p.f.m. wave is determined for weak additive Gaussian-noise channels.     

MMSE-optimal approximation of continuous-phase modulated signal as superposition of linearly modulated pulses

The optimal linear modulation approximation of any M-ary continuous-phase modulated (CPM) signal under the minimum mean-square error (MMSE) criterion is presented in this paper. With the introduction of the MMSE signal component, an M-ary CPM signal is exactly represented as the superposition of a finite number of MMSE incremental pulses, resulting in the novel switched linear modulation CPM signal models. Then, the MMSE incremental pulse is further decomposed into a finite number of MMSE pulse-amplitude modulated (PAM) pulses, so that an M-ary CPM signal is alternatively expressed as the superposition of a finite number of MMSE PAM components, similar to the Laurent representation. Advantageously, these MMSE PAM components are mutually independent for any modulation index. The optimal CPM signal approximation using lower order MMSE incremental pulses, or alternatively, using a small number of MMSE PAM pulses, is also made possible, since the approximation error is minimized in the MMSE sense. Finally, examples of the MMSE-optimal CPM signal approximation and its comparison with the Laurent approximation approach are given using raised-cosine frequency-pulse CPM schemes.     

Phase and clock synchronization of the Viterbi demodulator of continuous-phase modulation signals

The possibility of constructing the synchronization system of the Viterbi demodulator of continuous-phase modulation (CPM) signals is analyzed. The concept of multiphase trellis is introduced to provide the phase self-synchronization of a demodulator. The results calculated via computer simulation of the phase synchronization scheme that ensures efficient reception of CPM signals with constant and cyclically varying modulation indices are presented. The clock synchronization scheme whose main component is a delay discriminator is proposed and investigated. Its operability is demonstrated with the use of a minimum frequency-shift keying signal.     

Spectral density of millimeter wave amplitude scintillations in an absorption region

A detailed theory including the effect of water vapor fluctuations for the spectral density of the log amplitude scintillations of a radio wave propagating in an absorption medium is presented. The scintillation spectra obtained from links at 55.5 and 36.1 GHz on a common 4.1 km path are given together with the relevant meteorological data. Results show that the lower corner frequency predicted by Ott and Thompson, for the enhancement of the scintillations in an absorption region, is a good approximation.     

Spectral dyadic Green's function formulation for planar integratedstructures

The problem of the complete determination of the dyadic spectral Green's function for an integrated planar structure with a grounded dielectric slab has been considered and solved in a rigorous way by using the spectral theory of the electromagnetic field. The reciprocity theorem and the geometrical symmetry of the structure have demonstrated the different roles played by the independent terms of the spectral Green's function in the evaluation of the electromagnetic characteristics of the grounded slab excited with a general source. Furthermore, an equivalent circuit representation of the structure, allowing a noteworthy simplification in the determination of the total power, has been obtained. These equivalent circuits and the derived spectral Green's function presented here can be used to analyze and design microstrip antennas of arbitrary shape with a general type of loading, such as matched or unmatched loads, parasitic, and shorting pins     

Threshold characteristics of FM signals demodulated by an FM discriminator

An analysis of the threshold characteristic of FM signals when modulated by a Gaussian baseband signal and demodulated by an ideal FM discriminator has been derived. It is shown that there are two components in the demodulated output due entirely to modulation. This analysis serves also to unify the work of Rice [8], Wang [9], and Blachman [16].     

Algorithms of synchronization and detection of continuous-phase modulated signals with cyclically varying modulation index

Algorithms of simultaneous superbaud, clock, and phase synchronization for the detectors of continuous-phase modulated signals with cyclically varying modulation index are considered. The algorithms are based on the theory of nonlinear filtering and optimized with respect to the minimum mean-square error. A closed-loop model of the synchronization system is constructed and comprehensively studied with the aid of computer simulation.     

Spectral density of intensity fluctuations in semiconductor lasermodes under pseudorandom pulsed operation

The spectral density of intensity noise in individual modes as well as in the total output radiation of a semiconductor laser under pseudorandom pulsed operation was simulated for the first time. The influence of modulation and laser parameters on its noise properties is studied. The results presented are in agreement with those obtained by experiments, confirming that the new method investigated here is suitable for the analysis of intensity noise in pulsed-modulated nearly-single-mode semiconductor lasers     

Blind equalization of turbo trellis-coded partial-response continuous-phase modulation signaling over narrow-band Rician fading channels

In this paper, a blind maximum-likelihood channel estimation algorithm is developed for turbo trellis-coded/continuous-phase modulation (TTC/CPM) signals propagating through additive white Gaussian noise (AWGN) and Rician fading environments. We present CPM for TTC signals, since it provides low spectral occupancy and is suitable for power- and bandwidth-limited channels. Here, the Baum-Welch (BW) algorithm is modified to estimate the channel parameters. We investigate the performance of TTC/CPM for 16-CPFSK over AWGN and Rician channels for different frame sizes, in the case of ideal channel state information (CSI), no CSI, and BW estimated CSI.