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1998 Vol. 20, No. 2
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1998, 20(2): 145-150.
Abstract:
By use of the approach of complex random signal processing, the asymptotic statistical properties of the least square estimates of 2-D exponential signals are studied. In doing so it is found that the representation is considerably more intuitive, and is analytically more tractable.
By use of the approach of complex random signal processing, the asymptotic statistical properties of the least square estimates of 2-D exponential signals are studied. In doing so it is found that the representation is considerably more intuitive, and is analytically more tractable.
1998, 20(2): 151-156.
Abstract:
In this paper, the shortages of WVD s double-linearity in extracting the Doppler parameters of moving-targets are discussed, especially in multi-point moving-targets imaging processing based on the spectrum characteristics of moving-target echo signals in Synthetic Aperture Radar (SAR) imaging processing and the properties of WVD. Combined with the characteristics of Continuous Wavelet Transform (CWT), the responsibility and advantages of CWT in multi-point moving-target Doppler parameters extraction are analyzed. Finally a kind of multi-point moving- target Doppler parameters extracting algorithm based on CWT are developed, and the computer stimulating results demonstrate the correctness of the algorithm.
In this paper, the shortages of WVD s double-linearity in extracting the Doppler parameters of moving-targets are discussed, especially in multi-point moving-targets imaging processing based on the spectrum characteristics of moving-target echo signals in Synthetic Aperture Radar (SAR) imaging processing and the properties of WVD. Combined with the characteristics of Continuous Wavelet Transform (CWT), the responsibility and advantages of CWT in multi-point moving-target Doppler parameters extraction are analyzed. Finally a kind of multi-point moving- target Doppler parameters extracting algorithm based on CWT are developed, and the computer stimulating results demonstrate the correctness of the algorithm.
1998, 20(2): 157-165.
Abstract:
The frequency spectrum characteristics of SAR data link signals were derived. By means of two dimensional spectrum of SAR data link signal,the effects of the amplitude-frequency distortion and phase-frequency distortion in SAR data link system on SAR range and azmuth compressing performance were analysed. This analysis had been used in airborne SAR data link system design successfully.
The frequency spectrum characteristics of SAR data link signals were derived. By means of two dimensional spectrum of SAR data link signal,the effects of the amplitude-frequency distortion and phase-frequency distortion in SAR data link system on SAR range and azmuth compressing performance were analysed. This analysis had been used in airborne SAR data link system design successfully.
1998, 20(2): 166-174.
Abstract:
Continuous wavelet transforms (CWT) have lots of applications in the field of signal processing due to its unique characteristics. Their realization, however, request considerable computation. Therefore, a fast algorithm is provided to combat this contradiction. This algorithm is realized by organizing some computing cells which are built by two filters f(n) and g(n). In this paper, some practicable methods are discussed to construct these filters. Moreover, the structure of the whole fast algorithm, along with a method to refine the scale interval of wavelet coefficients, is also presented.
Continuous wavelet transforms (CWT) have lots of applications in the field of signal processing due to its unique characteristics. Their realization, however, request considerable computation. Therefore, a fast algorithm is provided to combat this contradiction. This algorithm is realized by organizing some computing cells which are built by two filters f(n) and g(n). In this paper, some practicable methods are discussed to construct these filters. Moreover, the structure of the whole fast algorithm, along with a method to refine the scale interval of wavelet coefficients, is also presented.
1998, 20(2): 175-181.
Abstract:
Based on the whitening property of wavelet transformation for 1/f noise, the problem of detecting deterministic signals in the presence of 1/f fractal noise is addressed. The transfer function of whitening filter is provided, the receiver structure based on Karhunen-Loeve expansion and the decision rule are also given. Finally performance of the receiver is analyzed and the experimental results are presented.
Based on the whitening property of wavelet transformation for 1/f noise, the problem of detecting deterministic signals in the presence of 1/f fractal noise is addressed. The transfer function of whitening filter is provided, the receiver structure based on Karhunen-Loeve expansion and the decision rule are also given. Finally performance of the receiver is analyzed and the experimental results are presented.
1998, 20(2): 182-187.
Abstract:
A cone-kernel time-frequency representation using adaptive scheme over both time and frequency is presented. For adapting to the analysed signal, the time-frequency representation uses varying cone length in each time-frequency point. It yields better results and requires only slightly more computation than the cone-kernel time-frequency representation that uses only time adaptive scheme.
A cone-kernel time-frequency representation using adaptive scheme over both time and frequency is presented. For adapting to the analysed signal, the time-frequency representation uses varying cone length in each time-frequency point. It yields better results and requires only slightly more computation than the cone-kernel time-frequency representation that uses only time adaptive scheme.
1998, 20(2): 188-193.
Abstract:
Conventional template matching technique is a successfully used algorithm in Chinese consonant recognition, yet its disadvantage limits its recovery of error,improvement of performance. The hybrid system based on the combination of neural network(NN) and fuzzy system maintains their advantages and makes full use of error tolerence performance, calculation performance, classification performance and decision performance for fuzzy neural network. In this paper, two kinds of cosonant recognition schemes based on fuzzy neural network are studied in detail. From the discussion of their structure, recognition rate and characteristics, it can be seen that recognition performance of fuzzy neural network is superior to template matching scheme and thus is more suitable for speech recognition.
Conventional template matching technique is a successfully used algorithm in Chinese consonant recognition, yet its disadvantage limits its recovery of error,improvement of performance. The hybrid system based on the combination of neural network(NN) and fuzzy system maintains their advantages and makes full use of error tolerence performance, calculation performance, classification performance and decision performance for fuzzy neural network. In this paper, two kinds of cosonant recognition schemes based on fuzzy neural network are studied in detail. From the discussion of their structure, recognition rate and characteristics, it can be seen that recognition performance of fuzzy neural network is superior to template matching scheme and thus is more suitable for speech recognition.
1998, 20(2): 194-198.
Abstract:
It is one of the tasks of Chinese speech understanding system that translates Chinese syllable from Chinese speech recognition system into a correct Chinese character, word, and phrase, sentence, and it will implement the task of speech to text altogether with Chinese speech recognition system. This paper makes a system on Chinese phrase understanding with a close ring approach with information feedback, which based on Chinese word recognition system. This system can understand the special constructed phras,a predicted result on this experiment is achieved. Finally, this paper gives a conclusion on the experiment and summary about the approach with information feedback.
It is one of the tasks of Chinese speech understanding system that translates Chinese syllable from Chinese speech recognition system into a correct Chinese character, word, and phrase, sentence, and it will implement the task of speech to text altogether with Chinese speech recognition system. This paper makes a system on Chinese phrase understanding with a close ring approach with information feedback, which based on Chinese word recognition system. This system can understand the special constructed phras,a predicted result on this experiment is achieved. Finally, this paper gives a conclusion on the experiment and summary about the approach with information feedback.
1998, 20(2): 199-205.
Abstract:
In this paper, on the basis of analysing and comparing the characteristics of En-In noise of in-phase and inverting amplifiers,new results are presented. The methods in this paper are highly important for us to design a low-noise circuit consisting of an operational amplifier and to extract the noise parameters of the operational amplifier.
In this paper, on the basis of analysing and comparing the characteristics of En-In noise of in-phase and inverting amplifiers,new results are presented. The methods in this paper are highly important for us to design a low-noise circuit consisting of an operational amplifier and to extract the noise parameters of the operational amplifier.
1998, 20(2): 206-212.
Abstract:
The approaches to model the real defect outlines in the IC manufacturing process are compared and some useful conclusions are obtained. The results obtained in this paper will be helpful for yield prediction and fault analysis of IC.
The approaches to model the real defect outlines in the IC manufacturing process are compared and some useful conclusions are obtained. The results obtained in this paper will be helpful for yield prediction and fault analysis of IC.
1998, 20(2): 213-218.
Abstract:
The characteristics of fully integrated filters would deviate from the desired values in the presence of parasitic poles. The effects of the finite DC gain and non-dominant poles of the integrators on filter perfomance are analyzed, deviation fomulas of pole frequency and quality factor for the second-order filters are given, and tuning of filter characteristic parameters is dealt with. Moreover, a gain-tunable current-mode continuous-time integrator is presented. Both fp and Q can be tuned with the filter based on the integrator.
The characteristics of fully integrated filters would deviate from the desired values in the presence of parasitic poles. The effects of the finite DC gain and non-dominant poles of the integrators on filter perfomance are analyzed, deviation fomulas of pole frequency and quality factor for the second-order filters are given, and tuning of filter characteristic parameters is dealt with. Moreover, a gain-tunable current-mode continuous-time integrator is presented. Both fp and Q can be tuned with the filter based on the integrator.
1998, 20(2): 219-222.
Abstract:
By discussing linear structures of Boolean functions, a large class of the first order correlation-immune nonlinear structure functions is got; After enumerating this class of functions, a new lower bound of the number of the first order correlation-immune functions is given.
By discussing linear structures of Boolean functions, a large class of the first order correlation-immune nonlinear structure functions is got; After enumerating this class of functions, a new lower bound of the number of the first order correlation-immune functions is given.
1998, 20(2): 223-228.
Abstract:
In this paper, the frequency diversity reception of multi-carrier CDMA signal is studied. The performance of multi-carrier CDMA system under perfect carrier recovery and frequency selective Rayleigh fading channel condition is analyzed. A smoothing algorithm utilizing time-frequency window for improving carrier phase estimation of multi-carrier CDMA signal is suggested. Simulation results for this algorithm are obtained under fading channel condition. It is shown that the frequency domain diversity reception scheme suggested in this paper suffers an in- significant degradation of performance comparing with theoretically optimal RAKE receiver, while considerably simplifying the receiver architecture.
In this paper, the frequency diversity reception of multi-carrier CDMA signal is studied. The performance of multi-carrier CDMA system under perfect carrier recovery and frequency selective Rayleigh fading channel condition is analyzed. A smoothing algorithm utilizing time-frequency window for improving carrier phase estimation of multi-carrier CDMA signal is suggested. Simulation results for this algorithm are obtained under fading channel condition. It is shown that the frequency domain diversity reception scheme suggested in this paper suffers an in- significant degradation of performance comparing with theoretically optimal RAKE receiver, while considerably simplifying the receiver architecture.
1998, 20(2): 229-234.
Abstract:
In CDMA mobile communication systems, multiple access interference can be cancelled by multiuser detection technique. The degradation by channel fading can be reduced by diversity reception. This paper investigates a family of multiuser receivers that combined decor-relating detection,antenna diversity and RAKE multipath diversity. The performances of the multiuser receivers are analyzed. The results demostrate a significant increase in the performances of the receivers by using multiuser detection and diversity reception.
In CDMA mobile communication systems, multiple access interference can be cancelled by multiuser detection technique. The degradation by channel fading can be reduced by diversity reception. This paper investigates a family of multiuser receivers that combined decor-relating detection,antenna diversity and RAKE multipath diversity. The performances of the multiuser receivers are analyzed. The results demostrate a significant increase in the performances of the receivers by using multiuser detection and diversity reception.
1998, 20(2): 235-240.
Abstract:
A new spreading sequences generator based on a class of chaotic maps is proposed. The theoretical performances of such sequences are shown to be good using the ergodic theory of chaos. The practical performances are then found by computer simulation. Results show that the balance property, the correlation property and the linear complexity of chaotic spreading sequences are quite good. Therefore chaotic spreading sequences are good candidates for direct-sequence spread-spectrum communications.
A new spreading sequences generator based on a class of chaotic maps is proposed. The theoretical performances of such sequences are shown to be good using the ergodic theory of chaos. The practical performances are then found by computer simulation. Results show that the balance property, the correlation property and the linear complexity of chaotic spreading sequences are quite good. Therefore chaotic spreading sequences are good candidates for direct-sequence spread-spectrum communications.
1998, 20(2): 241-246.
Abstract:
In this paper, the method of signal flow graphs is applied to path enumeration and deflection routing performance analysis in multihop networks. A Taylor series expansion of the transfer function yields the number of paths of a given length between the source and the destination.
In this paper, the method of signal flow graphs is applied to path enumeration and deflection routing performance analysis in multihop networks. A Taylor series expansion of the transfer function yields the number of paths of a given length between the source and the destination.
1998, 20(2): 247-250.
Abstract:
An explicit and stable time-domain method for solving the propagation of wave envelope in optical structures is proposed. Based on Dufort-Frankel method and variable change, it is a explicit difference. The method takes less memory and less time and it is applied to propagation of a 500 fs pulse in a waveguide over 2mm. Transient behavior of the pulse and the effects of the waveguide parameters are given.
An explicit and stable time-domain method for solving the propagation of wave envelope in optical structures is proposed. Based on Dufort-Frankel method and variable change, it is a explicit difference. The method takes less memory and less time and it is applied to propagation of a 500 fs pulse in a waveguide over 2mm. Transient behavior of the pulse and the effects of the waveguide parameters are given.
1998, 20(2): 251-256.
Abstract:
Ionospheric time delay is one of the largest error sources in C/A code GPS navigation and positioning. In this paper, a method is proposed for real-time dual-frequency ionospheric time-delay correcting using a C/A code GPS receiver, and the principle of the circuit block diagram for this method is analyzed with its feasibility theoretically demonstrated.
Ionospheric time delay is one of the largest error sources in C/A code GPS navigation and positioning. In this paper, a method is proposed for real-time dual-frequency ionospheric time-delay correcting using a C/A code GPS receiver, and the principle of the circuit block diagram for this method is analyzed with its feasibility theoretically demonstrated.
1998, 20(2): 257-262.
Abstract:
An alternative hybrid method which combines an extrapolation technique with the moment method (MM) for solving scattering problems involving large scatterers is presented. The Matrix Pencil (MP) method which is more robust to noise in the sampled data is employed to extract characteristic parameters, and an effective and simple extrapolation technique is adopted. The bistatic RCS of 2D dielectric strip and 3D conduction thin wire are calculated by the modified method in this paper. The results are in good agreement with those from general MM. The effectiveness of the proposed method is demonstrated.
An alternative hybrid method which combines an extrapolation technique with the moment method (MM) for solving scattering problems involving large scatterers is presented. The Matrix Pencil (MP) method which is more robust to noise in the sampled data is employed to extract characteristic parameters, and an effective and simple extrapolation technique is adopted. The bistatic RCS of 2D dielectric strip and 3D conduction thin wire are calculated by the modified method in this paper. The results are in good agreement with those from general MM. The effectiveness of the proposed method is demonstrated.
1998, 20(2): 263-266.
Abstract:
The eigenvalue equation of the helix-cylindrical waveguide system is derived and the complex roots of this system are obtained for the first time. The separation conditions among the real, imaginary and complex root modes are derived. A set of eigenvalue curves are presented. The radiation pattern of a helicone antenna is approximately calculated based on the eigenvalue equation. The numerical results agree with the previously measured data.
The eigenvalue equation of the helix-cylindrical waveguide system is derived and the complex roots of this system are obtained for the first time. The separation conditions among the real, imaginary and complex root modes are derived. A set of eigenvalue curves are presented. The radiation pattern of a helicone antenna is approximately calculated based on the eigenvalue equation. The numerical results agree with the previously measured data.
1998, 20(2): 267-272.
Abstract:
This paper describes a method about the design of the transition region of the electron beam from partially shielded cathode with uniform and periodic magnetic focusing field. It is necessary to use paraxial ray equation in non-equipotential space for the electron optics system in which anode potential is not the same as helix potential or for the electron optics system in which anode potential is the same as helix potential, but the perveance is high, thus the anode hole influence is strong. Some idea about the problem of coincidence of electron trajectory in electron gun with magnetic flux line for the electron optics system using partially shielded cathode with periodic magnetic focusing field is presented.
This paper describes a method about the design of the transition region of the electron beam from partially shielded cathode with uniform and periodic magnetic focusing field. It is necessary to use paraxial ray equation in non-equipotential space for the electron optics system in which anode potential is not the same as helix potential or for the electron optics system in which anode potential is the same as helix potential, but the perveance is high, thus the anode hole influence is strong. Some idea about the problem of coincidence of electron trajectory in electron gun with magnetic flux line for the electron optics system using partially shielded cathode with periodic magnetic focusing field is presented.
1998, 20(2): 273-276.
Abstract:
In this paper, the mathmetical description of signal coding based on MSDE and LMSDE model is given. The signal coding under LMSDE model is transformed into solving a quadratic programs with nonlinear constrains. Finally, the efficiency and robustness under high SNR are shown by coding to two signals.
In this paper, the mathmetical description of signal coding based on MSDE and LMSDE model is given. The signal coding under LMSDE model is transformed into solving a quadratic programs with nonlinear constrains. Finally, the efficiency and robustness under high SNR are shown by coding to two signals.
1998, 20(2): 277-280.
Abstract:
A quantitative analysis on the local precision and the ability against noise for image edge detection with wavelets (IEDW) has been done in this paper. With an appropriate wavelet function, IEDW algorithm is equal with a process that consists of two child processes: denoising and edge detecting. The feature is relative to the type of edges and the scales. The influence of the scale is a morror of the local feature of wavelet transform.
A quantitative analysis on the local precision and the ability against noise for image edge detection with wavelets (IEDW) has been done in this paper. With an appropriate wavelet function, IEDW algorithm is equal with a process that consists of two child processes: denoising and edge detecting. The feature is relative to the type of edges and the scales. The influence of the scale is a morror of the local feature of wavelet transform.
1998, 20(2): 281-284.
Abstract:
Field emission arrays are important to vacuum microelectronic microwave devices. The downward pyramid filled cone and upward etched silicon cone are fabricated. Two kinds of packing structures are used and the emission properties of these cones are tested. The characteristics of these structures and the application for microwave devices are analyzed.
Field emission arrays are important to vacuum microelectronic microwave devices. The downward pyramid filled cone and upward etched silicon cone are fabricated. Two kinds of packing structures are used and the emission properties of these cones are tested. The characteristics of these structures and the application for microwave devices are analyzed.
1998, 20(2): 285-288.
Abstract:
In this paper, a new type of microwave radiometer, real-time calibrated microwave radiometer was introduced. It has the following characteristics: (1) insensitive to system gain variations; (2)insensitive to receiver noise temperature variations; (3) the ability to provide realtime calibration; (4) wide measurement range. The prototype of real-time calibrated microwave radiometer at C -band was made in our laboratory. The integration time is 0.2s, the sensitivity is 0.2K,linearity of the receiver is 0.9990....
In this paper, a new type of microwave radiometer, real-time calibrated microwave radiometer was introduced. It has the following characteristics: (1) insensitive to system gain variations; (2)insensitive to receiver noise temperature variations; (3) the ability to provide realtime calibration; (4) wide measurement range. The prototype of real-time calibrated microwave radiometer at C -band was made in our laboratory. The integration time is 0.2s, the sensitivity is 0.2K,linearity of the receiver is 0.9990....
