The past few decades have witnessed a substantial increase in terahertz (THz) research. Utilizing THz waves to transmit communication and imaging data has created a high demand for phase and amplitude modulation. However, current active THz devices, including modulators and switches, still cannot meet THz system demands. Double-channel heterostructures, an alternative semiconductor system, can support nanoscale two-dimensional electron gases (2DEGs) with high carrier concentration and mobility and provide a new way to develop active THz devices. In this Letter, we present a composite metamaterial structure that combines an equivalent collective dipolar array with a double-channel heterostructure to obtain an effective, ultrafast, and all-electronic grid-controlled THz modulator. Electrical control allows for resonant mode conversion between two different dipolar resonances in the active device, which significantly improves the modulation speed and depth. This THz modulator is the first to achieve a 1 GHz modulation speed and 85% modulation depth during real-time dynamic tests. Moreover, a 1.19 rad phase shift was realized. A wireless free-space-modulation THz communication system based on this external THz modulator was tested using 0.2 Gbps eye patterns. Therefore, this active composite metamaterial modulator provides a basis for the development of effective and ultrafast dynamic devices for THz wireless communication and imaging systems.

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High efficient implementation of scaling in residue number system (RNS) is one of the critical issues for the applications of RNS in digital signal processing (DSP) systems. In this paper, an efficient scaling algorithm for signed integers in RNS is proposed firstly through introducing a correction constant in negative integers scaling procedure. Based on the proposed scaling algorithm, an efficient RNS 2 n scaling implementation method is presented, in which Chinese remainder theorem (CRT) and a redundant modulus are used to perform the base extension to obtain the least significant n bits of RNS integers. With the redundant modulus, the RNS sign detection can be achieved by the parity detection. And then, an approach to update the residue digit of the redundant channel is also proposed. Meanwhile, this paper provides a method of computing the correction constant of the redundant channel in negative integers scaling. The analysis results indicate that the complexity of the proposed scaling algorithm grows linearly with the word-length of the RNS dynamic range without using Look-up Table (LUT). Furthermore, the proposed algorithm is employed for a specific moduli set 2 n scaling. The synthesis results show that the critical path of the proposed algorithm is shortened by 12%, the area and power consumption performance is improved by about 35%, compared to the existing cascading 2 n scaling method for very large scale integration (VLSI) implementation under the same restriction. Besides, the VLSI layout indicates that the parallel structure is simpler. CitationMa S, Hu J H, Ye Y L, et al. A 2 n scaling scheme for signed RNS integers and its VLSI implementation.

In order to improve the image encryption system's ability to resist plaintext, noise, and data loss attacks, in this paper, a new plaintext-related and chaos-based image encryption scheme is proposed, which includes two rounds of encryption operations. The block parity checking, performed in the first round of encryption, is used to associate the plaintext information with a secret key so that the encryption scheme can resist plaintext attacks. Moreover, repetitive coding, which is adopted in the second round of encryption, is used to protect the plaintext-related parameters against noise and data loss attacks. Meanwhile, a highspeed digital chaotic sequence generator based on permutation polynomials and residue number system is also presented. The detailed performance evaluations, including key space, key sensitivity, differential attack resisting ability, anti-noise ability, correlation coefficient, and information entropy, show that our scheme not only possesses the properties of good randomness and large key space but also has a high degree of robustness against plaintext, noise, and data loss attacks.

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We propose and describe new error control algorithms for redundant residue number systems (RRNSs) and residue number system product codes. These algorithms employ search techniques for obtaining error values from within a set of values (that contains all possible error values). For a given RRNS, the error control algorithms have a computational complexity of t·O(log2 n + log2 mֿ) comparison operations, where t denotes the error correcting capability, n denotes the number of moduli, and mֿ denotes the geometric average of moduli. These algorithms avoid most modular operations. We describe a refinement to the proposed algorithms that further avoids the modular operation required in their respective first steps, with an increase of ⌈log2 n⌉ to their computational complexity. The new algorithms provide significant computational advantages over existing methods.