Search

This paper proposes a 2.4-GHz pre-bias RF energy harvesting rectifier with -35-dBm sensitivity for self-powered chips of wireless sensor networks (WSNs) for Internet of Things (IoT) applications. For high sensitivity, a pre-bias topology is presented by designing pre-stage and drive-stage rectifiers separately with multiple antennas. The pre-stage and the bias circuit just provide a proper bias voltage without driving loads. At single drive-stage configuration, -35-dBm sensitivity can be achieved with 2.4-GHz RF input power, 10-MΩ output load and 0.5-V continuous output voltage. When an 1% duty-cycled operating mode is adopted, 25-μW power can be supplied intermittently with 0.5-V output voltage. This proposed circuit is designed in 0.18-μm standard CMOS process.

This paper presents a 7.9 fJ/conversion-step 10-bit 125 MS/s successive approximation register (SAR) analog-to-digital converter (ADC) on the basis of a monotonic capacitor switching procedure. Simplified power-efficient digital control logic, multi-layer sandwich capacitor structure and high-speed level-shift bootstrapped sampling-and-holding (S/H) blocks are employed to achieve high performance with low power consumption. The prototype is implemented in 55 nm standard CMOS process, occupying an active area of 0.18 mm × 0.20 mm. Post simulation results show that an SNDR of 54.01 dB and an ENOB of 8.7 bit can be achieved by consuming 0.41 mW of the ADC core from a 1.2 V supply, and a figure of merit (FOM) of 7.9 fJ/conversion-step.

This paper presents a temperature and supply voltage variation-tolerant CMOS relaxation oscillator which is suitable for ultra-low power systems. A low-power low-cost half-period pre-charge compensation scheme is proposed to eliminate influences of the delay of the comparator and the RS latch on the frequency stability of the relaxation oscillator. In a clock period consisting of four working stages including normal charge, discharge, pre-charge and hold stage, the threshold voltage of comparators is adjusted dynamically. A 32.7-kHz relaxation oscillator with the proposed half-period pre-charge compensation scheme is implemented in a TSMC 0.18-μm CMOS process, occupying a silicon area of 0.048 mm2. Simulation results show that the proposed relaxation oscillator consumes 51-nW at room temperature from 0.6-V power supply, and temperature stability of 43.1 ppm/°C from −55 °C to 125 °C and ±0.60% frequency variation with supply voltage from 0.5 V to 1.0 V are achieved.

This paper proposes a DC-DC buck converter with all-pass network based passive level shifter in 55nm standard CMOS process, for battery powered portable applications. In order to handle high battery voltages in this advanced standard CMOS process, a passive level shifter based on all-pass network is applied for gate oxide protection. Drain extension is proposed to obtain high breakdown voltage of active region. The proposed buck converter with the passive level shifter works in DCM operation as its load current varies from 0.1–10mA. The buck converter achieves a peak efficiency of 93.7% and 83.8% at 10mA load current, with a supply voltage of 1.8V and 3.7V, respectively.

When facing with the mid-air interactive tasks in a wide range, the laser spot motion sensing technique can be as a information input mode of human-computer interaction(HCI). This paper explores the use of optical mouse sensors for building a laser spot tracking system, which can be used as a motion-based HCI device. Our work is focused on the characterization of the laser speckle sensing by optical mouse sensors. Based on the laser speckle displacement measurement capability of optical mouse sensors, we demonstrate that the low-cost optical mouse sensor can be used to record the motion of laser spot as a precise, fast and compact sensing method. To make a prototype system for demonstration, we describe a kind of deployment method for building optical mouse sensor array and propose a weighted method to fuse the raw data of multi-optical mouse sensor array. In experimental testing, the ISO standard tests for HCI input device were used for evaluating the efficiency of HCI input by optical mouse sensor-based laser spot tracking. A paradigm that using laser pointer and our laser spot tracking system to complete the dynamic hand gesture recognition task is also given in this paper.

This paper explores the use of optical mouse sensors for building positioning systems. A low-cost, customized optical sensor positioning system has been developed, with desirable high performance. Unlike the traditional dead-reckoning method using rotary encoders, optical mouse sensors are unacted on the errors induced by wheel slippage. However, some research has indicated that height variations can bring errors in 2D displacement measurements when using optical mouse sensors. What’s more, the so-called error cumulative phenomenon is an inevitable problem to every motion positioning system. To overcome these weaknesses, our main contributions are in two aspects. One is that a new adaptation mechanism is presented to enhance the positioning robustness to surface height variations. This performance enhancement attributes to the height-variation awareness of our presented system, in addition to the required positioning capability. The other is that a novel calibration paradigm with the assisted landmarks is proposed to eliminate the error cumulative phenomenon. This induced performance enhancement benefits from the high-speed optic flow sensing capability of optical mouse sensors. Experimental results are reported to validate the enhancement capability of the presented positioning system.