Showing papers by "Xidian University published in 1989"

Detection performance in K-distributed and correlated Rayleigh clutters

Abstract: Performance prediction for a detection system employing noncoherent integration is carried out for a chi-square family of fluctuating targets in K-distributed clutter plus noise. The detection performance for Swerling 11 targets in the K-distributed clutter plus noise is compared with that in exponentially correlated Rayleigh clutter. The results show that the performance prediction based on N pulses integrated in clutter plus noise using the K-distributed clutter model may be approximately equivalent to that using the exponentially correlated Rayleigh-distributed clutter model. >

Four-flux model with adjusted average crossing parameter to solve the scattering transfer equation.

Abstract: Resolution de l'equation du transfert radiatif a l'aide d'un modele a 4 flux ajuste. Cas de la diffusion optique

On the characterization of the Fourier spectra of functions defined on an Abelian group

Abstract: The authors determine the necessary and sufficient conditions that should be satisfied by an ordered set of complex numbers in order to be the Fourier (Chrestenson) spectrum of a function f:G/sup n/ to D, where D denotes C, R, or G. They obtain as corollaries to the main theorems some known results for G=Z/sub 2/. >

Measurements of raindrops sizes and canting angles

Abstract: We have presented a convenient method of measurements in adjusting the parameters for distributions of raindrop sizes and obtaining canting angles to accommodate to the local geographic and meteorologic conditions to get the required data for calculation of AR and XPD in the system planning of a short ground link using millimeter wave band. The measured results had been used in a theoretical formula to compute the XPD induced by rain in ground radio link of path length 2.2km and 35.3GHz with linear polarization, and discovered that the computed XPD agreed well with the measured XPD/6/. The agreement confirms that our methods of measurements are reliable and the measurements described above at one spot in the radio path are feasible in prediction of the AR and XPD for a short ground radio link.

Synthesis of communicating process skeletons from temporal-spatial logic specifications

Abstract: Temporal—spatial logic is a propositional logic with temporal and spatial modalities asserting on a network. In this paper, a tableau—like decision procedure for network satisfiability in that logic is presented and used in the synthesis of communicating skeletons of CSP—like programs. By explicitly introducing communication network in the logic system, our approach has some advantages over the temporal one.

Incremental frequency rules for arbitrary resonant cavities

Abstract: The Q factor due to resistive losses in conductor walls of resonant cavities can be evaluated by computing the changes in resonant frequency resulting from small perturbations of either magnetic or dielectric material along the cavity wall. Two rules are presented: one in terms of derivatives, suitable for analytic solutions, and the other in terms of incremental changes, suitable for use with computer codes.

New scheme for vector quantisation of speech signals

Abstract: The design theory of a vector quantiser is valid only on some assumptions which are unfortunately not satisfied in most real-world cases. A decomposition procedure of speech signals is described which leads to a proposed method for designing the vector quantisers in a reasonable way.

A tool to generate DEBUG program of arbitrary type of microprocessors

Abstract: In order to develop a tool for generating debugging programs to simulate all kinds of microprocessors, it is important to determine a general way to describe them. A language, called the instruction set describing language (ISDL), is presented which can express any type of instruction set. After the user inputs the instruction set description table (ISDT), a DEBUG program of the required type is generated. The design and implementation of the generator on one IBM-PC are presented. >

New design of a 64 kbps modem

Abstract: The design of a 64-kb/s modem that uses a single-chip digital signal processor (DSP) is described. The key points of the modem implementation with DSP are generation of satisfactory PRS-SSB (partial response suppressed carrier single side band) line signals, recovery of the carrier in the received signals, and acquisition of the bit-synchronization information. Some computer simulation results are given. >

Comprehensive improvement in low bit rate speech coding

Abstract: A comprehensive improved LPC (linear prediction coding) vocoder scheme is suggested. Many effective techniques are used in the scheme, such as vector quantization (VQ), line-spectrum pair parameters, and the just-noticeable-difference error criterion. By using these techniques it is possible to increase the linear prediction order from 10 to 14, and the sampling rate from 8 to 10 kHz without increasing the transmission bit rate. The design principles and the specifications of the scheme are introduced. Computer simulation shows that it gives very good synthetic speech quality at 2400 b/s. The sonograms of the original and synthesized speeches are also given for comparison. >

A study of the characteristics of a novel millimeter-wave microslab waveguide

Abstract: Microslab, a novel low-loss semiplanar waveguide, is studied to provide design charts for the propagation constant and characteristic impedance by applying second order finite element method of 'hybrid mode. A finite element program is written. The results of calculations are compared with previously approximate calculations.

Simplified lattice realization of fir digital filters

Abstract: This paper suggests a simplified lattice structure for implementing FIR digital filters. which halves the hardware requirements of a conventional lattice realization. The conversion algorithms between direct realizations and the simplified lattice forms are given. Furthermore, the algorithms for linear phase FIR filters are simplified. The principal results are illustrated by a practical example.

Design and analysis of integrated operational amplifier XD1531 with low noise at low frequencies

Abstract: Principles of design are described for the low frequency integrated operational amplifler XD1531 with low noise. The procedures of design of both the circuit structure and the transistor shape are considered. The first stage of the circuit is designed with the methods of low noise at low frequencies. The measures which decrease noises, especially, the 1/f noise originating from the semiconductor surface state and defects, are used for the transistor structure design. With analysis and comparison to products here and abroad in characteristics, it is shown that XD1531 has a lower noise index at low frequencies than others, and the effectiveness of design methods for bringing low noises have been demonstrated.

A study on 10.6 micron wave propagation in cloud, fog and haze

Abstract: The propagation of 10.6 micron wave in cloud, fog and haze has a special importance in laser radar and atmospheric diagnosis. The characteristics of the propagation and scattering by these media has been calculated and analyzed by using the Mie theory and Maheu's four-flux model.