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Achieving low-power and polarization-insensitive communication is a crucial and challenging task in the Internet of Everything. In this communication, we propose and demonstrate the implementation of two amplitude-reconfigurable metasurfaces, loaded with p-i-n diodes and operated around 5.8 GHz, to develop a novel polarization-insensitive backscatter communication (BC) system. Both communication transmitters using uniform and gradient metasurfaces are able to achieve high-efficiency polarization conversion and thus can cooperate with the receiver end to mitigate the interference generated by environmental carrier sources. To achieve the directional information transmission, we design a corner reflector metasurface and a gradient metasurface, which, respectively, enhances the gain in the backward and fixed scattering directions. Due to the advantages of polarization insensitivity and low energy consumption, this system promises great potential for future engineering applications in the Internet of Things, particularly for smart homes, wearable sensing, and other related areas.

This article proposes a reconfigurable intelligent surface (RIS) segmented symbiotic ambient backscatter system, which is composed of a primary source (S), a RIS, and a cooperative receiver (D) that decodes the signals from S and RIS with the aid of successive interference cancellation (SIC). For such, the RIS is segmented into two zones, namely, an EP zone and a BD zone, where the EP zone is used to enhance the received primary signal at D while the BD zone is utilized to backscatter RIS's signal to D. The coexistence outage probability (COP) is first developed, which is shown to be dominated by the minimum number of reflectors in the two zones for sufficiently high transmit signal-to-noise ratio (SNR). In contrast, the sum ergodic capacity (EC) can only be improved by increasing the transmit power and the number of reflectors in the EP zone at high transmit SNR. Finally, two algorithms are designed to minimize the number of reflectors in the two zones while achieving acceptable COP or sum EC.

This brief proposes a frequency domain model for injection-locked LC oscillators by introducing the impulse sensitivity function (ISF) and injection factor, analyzes the effect of the injection pulse width and injection position on oscillator performance based on this model, and derives an equation that can guide the design and optimization of oscillators. The model fills the gap in the field of frequency domain models for injection-locked LC oscillators. Based on the above model, a clock generator circuit structure operating at 14 GHz, combining a phase-locked loop with an injection-locked oscillator, is designed and measured based on a 65-nm cmos process. The circuit achieves better phase noise performance by optimizing the two parameters, which verifies the accuracy of the proposed model.