Summary A wirelessly powered temperature sensor is presented in complementary metal‐oxide‐semiconductor (CMOS) 180‐nm process. The wireless power transfer (WPT) is performed using resonant magnetic coupling, and a diode‐less AC to DC conversion is achieved through a quadrature‐oscillator with native‐MOS. The quadrature‐signals are subsequently used to control the diode‐less rectifier switches. The on‐chip temperature sensor exploits the subthreshold region temperature, and the sensed temperature is converted to frequency using a ring‐oscillator, which is implemented using differential cross coupled oscillator‐based delay cells. The temperature sensor architecture also employs a temperature‐insensitive replica circuit to minimize process dependence and enhance power‐supply rejection ratio (PSRR) of the sensing process. The application‐specific integrated circuit has been designed and fabricated in 180‐nm CMOS process and has dimensions of 2 mm × 2 mm. The measurement results demonstrate that the WPT circuit generates a DC voltage of 1V with a power transfer efficiency of 85% for distances 2 to 8 mm with settling time of microseconds to milliseconds. The temperature sensor demonstrates a resolution of < ±0.6C with a sensitivity of 0.52 mV/C and 126.9 Hz/C along with PSRR of −63dB and Integral Non‐Linraity (INL) of 5% measured across six different dies. The back‐scattering communication demonstrates a −53‐dB signal at a distance of 4 mm without affecting the WPT efficiency. The total power consumption of the temperature sensor along with the integrated biases is 120 nW.
This research focuses on intelligent unmanned aerial vehicle (UAV)-based, real-time video surveillance to ensure better monitoring and security of remote locations over 4G-LTE cellular networks by maximizing end-user quality of experience (QoE). We propose a novel server-based crosslayer rate-adaptive scheme (SCRAS) for real-time video surveillance over 4G-LTE networks using UAVs. Our key contributions are: (1) In SCRAS, mobile UAVs having preprogrammed flight co-ordinates act as servers, streaming real-time video towards a remote client; (2) server-side video rate adaptation occurs in 4G-LTE based on the physical characteristics of the received signal conditions due to variations in the wireless channel and handovers; (3) SCRAS is fully automated and independent of client assistance for rate adaptation, as it is intended for real-time, mission-critical surveillance applications; (4) SCRAS ensures that during rate adaptation, the current video frame should not be damaged by completing the current group of packet (GoP) before adaptation. Our simulations in NS3 provide credible evidence that SCRAS outperforms recently proposed schemes in providing better QoE for real-time, rate-adaptive, video surveillance over 4G-LTE under varying channel quality and frequent handovers that occur during flight by UAVs.
Summary A configurable full‐duplex low‐voltage differential signaling transceiver is presented, which can be configured to operate either for smaller differential channels (a few inches of striplines) or for longer channels (10 m of twisted pair cables). The configurability is embedded in the form of functionalities like pre‐emphasis, equalization, and slew rate control within the transceiver. The transmitter employs a hybrid voltage–current‐mode driver, which due to replica action, achieves a high‐impedance current‐mode signal dispatch and at the same time provides a matched impedance at the near end for improved intersymbol interference. The transmitter achieves slew rate control through a band‐limited pre‐driver, while the pre‐emphasis is achieved through a capacitive feed‐forward. The receiver employs a large‐input common‐mode first stage enclosed in a common‐mode control loop that enables its first stage to also act like a domain shifter (VDDIO‐to‐VDDCORE) reducing the overall power consumption. The equalization in the receiver is implemented by using carefully sized active inductive loads inside the receiver. The transceiver is designed and fabricated in 150‐nm complementary metal–oxide–semiconductor, sharing the space with a larger die, occupying an area of 400 × 400μm. The measurement results demonstrate that the transceiver is operating at 2 Gbps both for a 4‐in microstrip and a 10‐m twisted pair CAT6 cable with 30 and 180 ps of total jitter, respectively. The built‐in impedance calibrator minimizes the spread in the on‐die termination at the near end provided by the transmitter‐minimizing bit error rate across process, voltage, and temperature corners. The transmitter consumes a total power of 17 mW operating at 2 Gbps, that is, 8.5 pJ/bit of energy consumption; the receiver consumes a total power of 3.5 mW while driving a load of 5 pF at 2 Gbps. Copyright © 2016 John Wiley & Sons, Ltd.
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