The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum （DS-SS） systems. The excision threshold is a non-linear function related t...The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum （DS-SS） systems. The excision threshold is a non-linear function related to the number and the power of interference, and attempting to get the exact relation of threshold related to the number and the power of interference is almost impossible. The N-sigma algorithm determines the excision threshold using subsection function; however, the excision threshold determined by this method is not exact. A new method to determine the threshold of N-sigma algorithm is proposed. The new method modifies the scale factor N by use of the membership function. The threshold determined by this method is consecutive and smooth, and it is closer to the fact than that of the initial N-sigma algorithm. The GPS signal and single-tone （CW） interference （that is, typical narrow-band interference） are implemented in the simulation, and the results are presented to demonstrate the validity of the new algorithm.展开更多
An improved method of generating the self-balanced chaotic spread-spectrum code is presented. The chaotic-map pseudorandom sequence is used as the generated source. After a series of processing two-valued quantization...An improved method of generating the self-balanced chaotic spread-spectrum code is presented. The chaotic-map pseudorandom sequence is used as the generated source. After a series of processing two-valued quantization, inversion, all upside down, radix-S block upside down and shift combination, the proposed code is achieved. Theory analysis and simulation performance of the improved code are illustrated. And the results indicate that the suggested method gains a better performance than the traditional one by reasonable choices of the initial value and the S parameter in the im- proved method. Meanwhile the chaotic sequence＇ s characteristic of large addresses is inherited when the chaotic-map is used as the source. This advantage makes this improved code very suitable for the multiple access application in communication system.展开更多
This paper presents a secure spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source ...This paper presents a secure spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source identification or doctors signature in binary image format into host digital radiological image for potential telemedicine applications. Performance of the algorithm is analysed by varying the gain factor, subband decomposition levels, size of watermark, wavelet filters and medical image modalities. Simulation results show that the proposed method achieves higher security and robustness against various attacks.展开更多
A novel monolithic digitalized random carrier frequency modulation spread-spectrum clock generator （RCF-SSCG） is proposed.In this design,the output frequency of the proposed RCF-SSCG changes with the intensity of th...A novel monolithic digitalized random carrier frequency modulation spread-spectrum clock generator （RCF-SSCG） is proposed.In this design,the output frequency of the proposed RCF-SSCG changes with the intensity of the capacitive charge and discharge current.Its analytical model is induced and the effect of the modulation parameters on the spread spectrum is numerically simulated and discussed.Compared with other works,this design has the advantages of small size,low power consumption and good robustness.The circuit has been fabricated in a 0.5μm CMOS process and applied to a class D amplifier in which the proposed RCF-SSCG occupies an area of 0.112 mm^2 and consumes 9 mW.The experimental results confirm the theoretical analyses.展开更多
A method of Direct Sequence Spread-Spectrum(DS/SS)corn,nunication based on synchronizedspatiotemporal chootic sequences is proposed.We use Coupled Logistic Maps(CLM)to generate the chaotictimes sequences.This coupled ...A method of Direct Sequence Spread-Spectrum(DS/SS)corn,nunication based on synchronizedspatiotemporal chootic sequences is proposed.We use Coupled Logistic Maps(CLM)to generate the chaotictimes sequences.This coupled mop lattices has long chaotic transient and can be recovered easily.Therobustness and the error probability is discussed and the advantage of the method in Spectral spreading andsecure communication is demonstrated.展开更多
文摘The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum （DS-SS） systems. The excision threshold is a non-linear function related to the number and the power of interference, and attempting to get the exact relation of threshold related to the number and the power of interference is almost impossible. The N-sigma algorithm determines the excision threshold using subsection function; however, the excision threshold determined by this method is not exact. A new method to determine the threshold of N-sigma algorithm is proposed. The new method modifies the scale factor N by use of the membership function. The threshold determined by this method is consecutive and smooth, and it is closer to the fact than that of the initial N-sigma algorithm. The GPS signal and single-tone （CW） interference （that is, typical narrow-band interference） are implemented in the simulation, and the results are presented to demonstrate the validity of the new algorithm.
文摘An improved method of generating the self-balanced chaotic spread-spectrum code is presented. The chaotic-map pseudorandom sequence is used as the generated source. After a series of processing two-valued quantization, inversion, all upside down, radix-S block upside down and shift combination, the proposed code is achieved. Theory analysis and simulation performance of the improved code are illustrated. And the results indicate that the suggested method gains a better performance than the traditional one by reasonable choices of the initial value and the S parameter in the im- proved method. Meanwhile the chaotic sequence＇ s characteristic of large addresses is inherited when the chaotic-map is used as the source. This advantage makes this improved code very suitable for the multiple access application in communication system.
文摘This paper presents a secure spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source identification or doctors signature in binary image format into host digital radiological image for potential telemedicine applications. Performance of the algorithm is analysed by varying the gain factor, subband decomposition levels, size of watermark, wavelet filters and medical image modalities. Simulation results show that the proposed method achieves higher security and robustness against various attacks.
基金Project supported by the National Natural Science Foundation of China(No.60436030).
文摘A novel monolithic digitalized random carrier frequency modulation spread-spectrum clock generator （RCF-SSCG） is proposed.In this design,the output frequency of the proposed RCF-SSCG changes with the intensity of the capacitive charge and discharge current.Its analytical model is induced and the effect of the modulation parameters on the spread spectrum is numerically simulated and discussed.Compared with other works,this design has the advantages of small size,low power consumption and good robustness.The circuit has been fabricated in a 0.5μm CMOS process and applied to a class D amplifier in which the proposed RCF-SSCG occupies an area of 0.112 mm^2 and consumes 9 mW.The experimental results confirm the theoretical analyses.
文摘A method of Direct Sequence Spread-Spectrum(DS/SS)corn,nunication based on synchronizedspatiotemporal chootic sequences is proposed.We use Coupled Logistic Maps(CLM)to generate the chaotictimes sequences.This coupled mop lattices has long chaotic transient and can be recovered easily.Therobustness and the error probability is discussed and the advantage of the method in Spectral spreading andsecure communication is demonstrated.
