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The increasing demand for wireless Internet of Things (IoT) calls for power efficient RF energy harvesting approach. The current dominant single-band RF energy harvesting front-end system restricts itself to a single frequency, which is at the risk of ineffective operation when the harvesting frequency is unavailable. This paper reviews and explores the alternative approach of a multiband RF energyharvesting front-end system. It covers all essential circuitry of a multiband RF energy harvesting front-end system, starting from the recent RF surveys which investigate the typical, usable, and high-strength RF input, to the overview of the state-of-the-art antenna, impedance matching network (IMN), and RF-DC rectifier. The recent advancement of the multiple RF input harvesting abilities, reflection loss minimization, and performance improvement are comprehensively reviewed for different operating conditions, and this review also presents the advantages and disadvantages of the different circuit architecture combinations for multiband RF energy harvesting front-end systems. In summary, this review aims to fill the research gap in the further advancement of multiband RF energy harvesting towards enhancing its performance through optimal circuit integration of the front-end system.INDEX TERMS CMOS, power conversion efficiency (PCE), multiband RF energy harvesting, RF power transmission.

Micro-electro mechanical system (MEMS) based oscillators are revolutionizing the timing industry as a cost effective solution, enhanced with more features, superior performance and better reliability. The design of a sustaining amplifier was triggered primarily to replenish MEMS resonator’s high motion losses due to the possibility of their ‘system-on-chip’ integrated circuit solution. The design of a sustaining amplifier observing high gain and adequate phase shift for an electrostatic clamp-clamp (C-C) beam MEMS resonator, involves the use of an 180nm CMOS process with an unloaded Q of 1000 in realizing a fixed frequency oscillator. A net 122dBΩ transimpedance gain with adequate phase shift has ensured 17.22MHz resonant frequency oscillation with a layout area consumption of 0.121 mm2 in the integrated chip solution, the sustaining amplifier draws 6.3mW with a respective phase noise of -84dBc/Hz at 1kHz offset is achieved within a noise floor of -103dBC/Hz. In this work, a comparison is drawn among similar design studies on the basis of a defined figure of merit (FOM). A low phase noise of 1kHz, high figure of merit and the smaller size of the chip has accredited to the design’s applicability towards in the implementation of a clock generative integrated circuit. In addition to that, this complete silicon based MEMS oscillator in a monolithic solution has offered a cost effective solution for industrial or biomedical electronic applications.

Driven by the momentum toward compact and low-power Internet-of-Things (IoT) systems, the research on fully-integrated and energy-efficient kHz-to-MHz timers increased explosively. This article examines recent publications on timers and classifies them into two major categories: open-loop-based and close-loop-based timers. Upon introducing the basic parameters for characterizing a timer, we perform an extensive investigation to gain insights into recent state-of-the-art works. We also discuss in detail the comparison between the two classes of timers. With the aid of the state-of-the-art, we present a comprehensive review from multiple perspectives, such as Energy Efficiency, Temperature Coefficient, Temperature Range, Figure-of-Merit, etc.