Joint Probabilistic Data Association (JPDA) is a very fine optimal multitarget tracking and association algorithm in clutter. However, the calculation explosion effect in computation of association probabilities has been a difficulty. This paper will propose a method based on layered searching construction of association hypothesis events. According to the method, the searching schedule of the association events between two layers can be recursive and with independence, so it can also be implemented in parallel structure. Comparative analysis of the method with relative methods in other references and corresponding computer simulation tests and results are also given in the paper.

The theory of distributed inference and decision is a kind of theory to be used to solve the distributed interwound decision problems. This theory is first presented to solve the problem of target data association in this paper. The basic principle and structure of distributed target data association decision system are formulated and a algorithm for this problem is designed based on the principle and structure. The algorithm is divided into two stages , the one is initial inference and decision stage, another is distributed inference and decision stage. In the end of this paper the algorithm is discussed.

The paper gives a detail analysis of the mathematical principle of the RELAX algorithm that separating and resolving the signals, and the performance of the characters of the separation and resolution in the circumstance that the algorithm resolves the signals or not. The relationship and development of the algorithm from DD-RELAX to CD-RELAX, RELAX-AS and MD-RELAX are also discussed. The computer simulation are made to confirm the theory analysis.

Fast recovery and frequency-shifting of real bandpass signal based on second-order sampling is discussed. Using FFT and complex filtering, real bandpass signal can be recovered as a analytic signal whose central frequency is within two times of its bandwidth, and phase property is not changed. Finally, using simple computation, original frequency can be acquired. Computer simulation shows the correction of the method.

The main methods for estimation of cyclic spectra for cyclostationary processes are temporally smoothed cyclic periodogram and spectrally smoothed cyclic periodogram. In case of short record length, both methods have low resolution and reliability. This paper uses two-channel complex maximum entropy (autoregressive) spectral analysis method to estimate cyclic spectra. Fine performances such as resolution and reliability can be obtained with this method.

Short time Fourier transform and pseudo-Wigner distribution are two most useful tools in time-frequency analysis, the choice of window functions is the base for their applications, which require deep study. The criteria of window functions are discussed in detail, and the optimal length of window is obtained by means of optimal frequency resolutions.

The relationship between the discrete Fourier transform (DFT) and the symmetrical/Asymmetrical number system (SNS/ANS) is introduced in this paper. And the influence of noise upon the solution to an ambiguity problem in number system is also discussed. The principle of noise insensitive solution to the ambiguity in ANS is extended to SNS. The unambiguous bandwidth equation with noise protection in SNS is presented,based on which a real time noise insensitive algorithm in SNS for resolving undersampling ambiguous frequency is proposed.

The concern here is retrieval of multiple tone harmonics observed in complex-valued multiplicative noises with zero mean. Cyclic statistics have proved to be useful for harmonic retrieval in the presence of complex-valued multiplicative noises with zero mean of arbitrary colors and distributions . Performance analysis of cyclic estimators is carried through and large sample variance expressions of the cyclic estimators are derived. Simulations validate the large sample performance analysis.

Range-Doppler method is the most common method in ISAR imaging. To obtain radar image of a target, certain angle of the target with respect to Radar Light Of Sight (RLOS) during the coherent integration interval is required. In some case, there will exist scatterers migration. Actually, scatterers Migration Through Resolution Cell (MTRC) occurs inevitably in higher resolution radar image, which will result in the point-spread function broadening and image resolution decreasing. The scatterers' migration is discussed in the paper and a simple and efficient method is proposed to compensate MTRC. Compensation results of the simulated data and the real data collected in a microwave anechoic chamber show that the resolution of the final radar image is improved.

Impersonation and eavesdropping are the crucial threats in wireless communication systems. In personal communication systems (PCS), it is necessary to provide security protection on the voice/data transmitted over wireless links, and perform mutual authentication between mobile user and serving network. Recently, many protocols are proposed for different mobile networks, such as GSM, IS-41, CDPD and wireless LAN. However, these protocols have different weakness when they are applied in PCS environment. Based on the public-key P&A model proposed by M.J. Beller, et al.(1993), this paper presents an authentication protocol for mobile user registration. Then the formalized security proof of the protocol using BAN authen- tication logic, and the qualitative analysis about its computing complexity are given. Results show that many new security features are added to the proposed protocols when it is compared with the protocols available.

CBR is one of the most important kinds of real-time traffic in ATM network. Guarantying the quality of service(QOS) of CBR traffic is crucial to the success of ATM technology. So, analyzing the QOS of the CBR traffic is worth studying. The paper analyzes the QOS of CBR traffic in a bursty enviroment through computer simulation. It is found that multiplexer utilization, buffer capacity, background intensity and autocorrelation property of the background traffic can all make hard effects on the delay and delay jitter of CBR traffic. Especially, when the background traffic exhibits long-range dependence, the QOS of CBR traffic will degrade severely. Some control actions should be taken to minimize the effects of all the factors.

In this paper, a novel moving picture coding algorithm, called the adaptive multilevel quantized subsampled block truncation coding is presented. The experiments show that this algorithm has better performance than the other algorithms of the same kind and can be realized in real time with software in current PC, the compression ratio is 30 and the peak signal to noise ratio is 35.4 dB.

Key escrow systems have gained much attention in recent years. A key escrow system can provide cryptographic protection to sensitive data ,while at the same time, allows for the decryption of encrypted message under lawful authorization. Since the public were not satisfied with the classified encryption method used in key escrow system in hardware, such as Clipper and Capstone, NIST of US announced a cooperative program with industry to explore the possibilities of performing key escrow cryptography using software-only techniques. This paper proposes a scheme for supporting the implementation of key escrow systems in software, which employs symmetric encryption algorithm for securing communication, and one-way hash function and asymmetric cryptography for identifying the users and verifying session key.

In this paper a threshold secret sharing scheme to identify cheaters is proposed by using authentication codes.The performance of the scheme is discussed. The results show that in the scheme the valid shareholders not only can identify the impersonation of an adversary, but also are able to detect the cheating of some valid shareholders, in particular one honest shareholder is able to detect the cheating of the other participants forming a coalition, and the information rate of the scheme is higher than that of others.

An approach to generate a multi-energy electron beam by transmitting a monoen-ergetic beam though a solid film is proposed. The energy (velocity) spectrum of the resultant beam is predicted by Monte Carlo simulation of electron scattering. The calculation accuracy is fairly good in comparison with available measurements. Space charge effect of a multi-energy electron beam in a uniform electrical field or field-free space has also been analyzed.

In this paper, parallel corner feeding with two ports is proposed to realize the high isolation, dual-polarized microstrip antenna. A novel dual-polarized feedline network is designed for the array. A method of analysis is developed, which is based on the multiport network model, the cavity theory, the segmentation technique and the desegmentation technique. A one-layer coplanar microstrip antenna array at 6GHz band is designed. The measured isolation between two feeding ports reaches -50dB, which is much better than those of one-layer dual-polarized arrays commonly used.

Based on a quaternary algebra, this paper presents a unified theory of ternary circuits-theory of three essential circuit elements (signal, network and load). The theory shows that a simple transform relation exists between ternary gate stage and switch stage, between ternary switch stage structures and between ternary dynamic and static circuits. Particularly, various ternary dynamic and static circuits can be deduced from the same equation.

An MSM photodiode equivalent circuit model based on external microwave port characters are presented in this paper, while the parameters of DC and capacitance model preserve the physical meaning. The circuit simulation results are agree with experimental results.

Synaptic connection matrix encodes limited information. It is well known that neural network memory with storage prescriptions based on Hebb s rule will collapse as more patterns are stored. By requiring that old patterns are automatically forgotten and the memory recalls only the most recent ones, a new short-term neural network memory based on Y.Baram s fractal neural network is proposed. Comparison is made with Morris and Wong's method and the experimental results are shown to be rather satisfactory and encouraging.

Foliage penetrating (FOPEN) VHF/UHF SAR can image hidden man-made targets with wide-angle and ultra-wideband to achieve both range and azimuth with high resolutions. The target can be modeled by dihedral formed between its side and the ground due to the long wavelength of VHF/UHF. The paper provides the backscattering signal form of dihedral model, SAR image of man-made targets is simulated in theory and the signature library is formed which can be utilized in the subsequent stages of target detection and recognition.

The parallel attack is discussed in this paper from the semantics, and the method of decision is presented.

This paper points out the drawback of the secret sharing schemes proposed by J.He, et al. (1994) and L. Harn(1995). This paper also gives the secret sharing schemes, which overcome the above mentioned drawback.

The radiation field formulas are given for a parabolic torus reflector antenna. A five-beam parabolic torus antenna with 90?azimuth coverage has been designed and developed. An experimental radiation pattern of these five beams and theoretical patterns of the central beam of the antenna are also given. Comparison between calculated and measured patterns shows they are in good agreement. Finally, the measured gain data for the central beam and the edge beam are presented.

A symmetric double-layer frequency selective surface is studied by adopting the symmetric and anti-symmetric excitation method. Transmission properties of the structure are discussed for different dielectric parameters of the structure. It is shown that the frequency response of the structure can be great by improved by choosing suitable dielectric parameters of the covering and coating layers.

To improve the precision of the outer measuring system,the accuracy of radiowave refractive correction must be raised. The refractive correction's formulation in the assumption of atmospheric ballface stratification does not meet the requirements,because the atmospheric parameters are fucnctions of the four dimention at temporospatial structure. The new refractive correction's formulation needs to study the atmospheric variations not only on space, but also on time. This paper gives the experimental results of the effect of the atmospheric time variation on the precision of the radiowave refractive correction.