Considering that chaotic systems are highly sensitive to parameters, we design two new parameter variable chaotic systems by constructing parameter perturbation items. These systems are constructed using the state variables of the Liu chaotic system to perturb the parameters of the Lorenz and Chen chaotic systems and are called the Lorenz-Liu chaotic system (LLCS) and Chen-Liu chaotic system (CLCS), respectively. In particular, the parameter perturbation items constructed in this study are not periodic but rather chaotic signals and change in real time. Compared with the original systems, they exhibit more complex randomness and dynamic behaviors. In the proposed cryptosystem, which considers the concept of Deoxyribonucleic Acid (DNA), the solar radio spectrogram is dynamically encoded through the LLCS, and then, the CLCS is used to scramble and diffuse the decoding matrices. In addition, the algorithm uses the 256-bit Secure Hash Algorithm (SHA-256) to generate the initial keys, which enhances the algorithm’s sensitivity to plaintext. Simulation results and security analysis show that the cryptosystem has a large key space and high key sensitivity, and can resist various attacks, such as differential attacks and chosen-plaintext attacks.

The improvement of Analog-to-Digital Converter (ADC) performance is crucial to improve the data quality of the signal acquisition system. Therefore, based on the dithering technology, combined with the chaotic system, the study designs and analyses a novel method to improve the Spurious-Free dynamic range (SFDR) of the ADC. First, a new five-dimensional chaotic system is proposed in this paper. The chaotic characteristics and dynamic behavior of the new system have been deeply analysed. The analysis methods mainly consist of the Lyapunov exponent, bifurcation diagram, power spectrum and sample entropy. The corresponding simulation model has been developed in Simulink, and the simulation results prove the reality and feasibility of the new chaotic system. Second, the random number homogenization universal algorithm is used to modify the amplitude of the chaotic sequences generated by the new chaotic system. The uniformity and correlation analysis prove that the Dither signal has strong uniformity and randomness. Third, a behaviour-level simulation model of the pipeline ADC is built; then, the narrowband, broadband and different amplitude Dither signals are added to verify the improvement effect for the dynamic performance of the ADC. The experimental results demonstrate that the designed method can improve the SFDR of the ADC by 10.37 dBc, which effectively eliminates the harmonic energy and improves the dynamic performance of the ADC.

Based on the block compressed sensing theory (BCS), combined with the five-dimensional chaotic system, we propose and analysis a novel spectrogram visual security encryption algorithm. The research is devoted to solving the compression, encryption and steganography problems of spectrograms with large data volume and high complexity. Firstly, Discrete wavelet transform (DWT) is applied to process the spectrogram to generate the coefficient matrix. Then block compressed sensing is applied to compress and pre-encrypt the spectrogram. Secondly, the study designed a new five-dimensional chaotic system. Then several typical evaluation methods, such as phase diagram, Lyapunov exponent (LE), bifurcation diagram and sample entropy (SE) are applied to deeply analyze the chaotic behavior and dynamic performance of the system. Moreover, the corresponding Simulink model has been built, which proves the realizability of the chaotic system. Importantly, the measurement matrix required for compressed sensing is constructed by the chaotic sequence. Thirdly, performing dynamic Josephus scrambling and annular diffusion on the secret image to get the cipher image. Finally, an improved least significant bit embedding method (LSB) and Alpha channel synchronous embedding are designed to obtain the steganographic image with visual security properties. To make the initial keys of each image is completely different from other images, the required keys are produced using the SHA-256 algorithm. The experimental results confirm that the visual

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The dynamic spectrum of solar radio burst is a very important tool to study the characteristics of solar radio burst. However, due to the influence of the instruments noise of the solar radio telescope, external interference, the change of ambient temperature, absorption of clouds and so on, the sensitivity of the observation system will be reduced. In particular, the weak solar radio burst signal is easily submerged by various interference signals. In order to improve the sensitivity of solar radio telescope to observe solar radio burst signals and remove narrow-band interference signals, a spectrum data processing algorithm of spectral subtraction method based on entropy and energy threshold values (SSM-EE) is proposed in this article. There are multiple processing steps of SSM-EE. The new spectrum data are obtained by subtraction method between the original spectrum data and the noise floor data. After a large number of data simulation and verification of the actual observation data, it shows that the method proposed in this article has good practical value.