This article presents a low-voltage (LV) sub-sampling phase-locked loop (LVSSPLL). The architecture of hybrid dual-path loop-based SSPLL is proposed to mitigate the issue of limited output voltage ...range of LV charge pump (CP). Four LV building blocks, including a proportional path sub-sampling CP (SSCP), an integral path SSCP, an LV sub-sampling phase detector, and an LV digitally controlled capacitor array in the LC -based voltage-controlled oscillator, are proposed to simultaneously reduce the PLL integrated jitter and the jitter variation over supply voltage variation. Fabricated in 40-nm CMOS process with a core active area of 0.24 mm 2 , the LVSSPLL operates at 0.65-V supply and achieves 12-16-GHz tuning range, 56.4-fs integrated jitter at 14 GHz, 7.2-mW power consumption, and −256.4-dB figure-of-merit (FoM). The measured integrated jitter variation is less than 14.5 fs within the supply voltage range from 0.62 to 0.7 V, which shows robustness over supply voltage variation.
Visible light communication (VLC) technology employing light-emitting diodes (LEDs) as light sources has the advantages of using the license-free spectrum, being power and cost-efficient and having ...high security. However, common LED devices have the limitations of narrow bandwidths, nonlinear optical and frequency responses over different bias current levels, which cause inter-symbol interference and signal distortion, especially under high order modulation schemes with large current swings. In view of this, a compact PAM-4 VLC transceiver system employing a white LED as the light source with pre- and post-equalization is proposed. The white LED consists of a red, a green and a blue LED unit (RGB LED). Controlled by 3-bit thermometer codes, three separate drivers with feed-forward equalizers (FFEs) drive the RGB LED units to produce the PAM-4 optical signal. The driving currents from the three drivers with FFEs can be calibrated using digital and analog tunings to eliminate the differences in optical and frequency responses of the RGB LED units. A cascaded continuous-time linear equalizer (CTLE) is used at the receiver side as post-equalization to compensate for the narrow bandwidth of LED units. Based on experimental results, the proposed RGB PAM-4 VLC system can improve the highest achievable data rate by 1.67 times from 28 to 75 Mb/s using the pre- and post-equalization scheme.
This article presents two dual-photodiode (PD) differential optical receivers that achieve double photodetection area to support gigabit-per-second optical wireless communication (OWC), while ...maintaining the receiver bandwidth. To enable differential light detection with a single incident light beam, a dual-PD OWC receiver architecture is proposed. In this architecture, two PDs are connected to the receiver complementarily without sacrificing the receiver bandwidth, and meanwhile, remain properly reversely biased. In addition, an adaptive dc photocurrent cancellation (ADPC) circuit is employed to prevent the saturation of the receivers under strong and imbalanced incident light. Based on the proposed architecture, two OWC receivers are implemented, including a proposed receiver and a reference one. In the proposed receiver, a low-noise shunt-feedback transimpedance amplifier (SF-TIA) with differential-pair-based current reuse and cross-coupled resistive feedback is proposed to enhance the sensitivity. In contrast, the reference receiver employs positive capacitive feedback to improve the transimpedance amplifier (TIA) performance. Both receivers have been fabricated with a standard 180 nm CMOS process and have been wire-bonded to two PDs. Experimental results indicate that both receivers can detect optical signals with data rates up to 2 Gb/s, and the proposed receiver architecture has significantly improved the bit error rate (BER) at 1.5 Gb/s from worse than <inline-formula> <tex-math notation="LaTeX">10^{-6} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">10^{-9} </tex-math></inline-formula> (error-free) with constrained optical power density. Moreover, the proposed receiver achieves an input sensitivity of <inline-formula> <tex-math notation="LaTeX">3.4~\mu \text{A}_{\mathrm {pp}} </tex-math></inline-formula> due to the superior performance of the proposed TIA, which outperforms the sensitivity of <inline-formula> <tex-math notation="LaTeX">10.4~\mu \text{A}_{\mathrm {pp}} </tex-math></inline-formula> from the reference receiver. Both sensitivities are measured at 1.5 Gb/s for a BER of <inline-formula> <tex-math notation="LaTeX">10^{-9} </tex-math></inline-formula> (error-free). The power consumption of the proposed and the reference receiver are 24.3 and 19.1 mW, respectively, excluding the output driver.
Water plays an important role in the whole process of geopolymer synthesis. X-ray diffraction (XRD) and thermogravimetry (TG) showed that residual water depressed the activity development of calcined ...kaolin before stable crystalline phases formed as confirmed by the compressive strength. Reaction heat evolution measurement revealed that high liquid/solid ratio could accelerate the dissolution of raw materials and the hydrolysis of Si
4+ and Al
3+ compounds but hinder the polycondensation when OH
− concentration is high enough as 12 mol/L. The effect of nonevaporable water on the strength variation of geopolymers was firstly analyzed. The results indicated that nonevaporable water was necessary to keep the strength stable and the optimum content was about 7.4%.
This article proposes an LC -based spiral transmission line structure, which can effectively reduce the area of ON-chip transmission lines. The quarter-wavelength transmission line realized by this ...transmission line structure can be widely used in millimeter-wave circuits design. Based on the LC -based spiral transmission line structure, a 28-GHz single-pole double-throw (SPDT) switch and a 37-GHz Wilkinson power combiner are implemented with an area of only 0.028 mm 2 in 65-nm CMOS. Measurement results indicate that the SPDT switch has an insertion loss of less than 1.5 dB and an isolation better than 23.7 dB in the frequency range from 20 to 35 GHz. The insertion loss and the isolation of the Wilkinson power combiner at 36.9 GHz is 0.9 and 30.3 dB, respectively.
In this Letter, a novel inverter-based trans-impedance amplifier (TIA) with enhanced gain and sensitivity is presented for Gb/s visible light communication (VLC). By employing capacitive feedback ...with a large negative equivalent capacitance to reduce the TIA input capacitance, the proposed TIA achieves a trans-impedance gain of 89.4 dBΩ with 5.7 dB improvement and an input referred noise current of 0.43 µArms with 1.8 dB improvement when compared to a reference TIA without capacitive feedback. Both the proposed TIA and the reference TIA have the same −3 dB bandwidth (BW) of 3 GHz and the same power consumption of 1 mW, and they are designed with a 40 nm CMOS process.
Fire is an essential Earth system process that alters ecosystem and atmospheric composition. Here we assessed long-term fire trends using multiple satellite data sets. We found that global burned ...area declined by 24.3 ± 8.8% over the past 18 years. The estimated decrease in burned area remained robust after adjusting for precipitation variability and was largest in savannas. Agricultural expansion and intensification were primary drivers of declining fire activity. Fewer and smaller fires reduced aerosol concentrations, modified vegetation structure, and increased the magnitude of the terrestrial carbon sink. Fire models were unable to reproduce the pattern and magnitude of observed declines, suggesting that they may overestimate fire emissions in future projections. Using economic and demographic variables, we developed a conceptual model for predicting fire in human-dominated landscapes.
Indoor visible light positioning (VLP) systems can be directly integrated with existing lighting infrastructure and achieve high-accuracy positioning when using CMOS image sensors as receivers. Due ...to cameras' limited field of view (FOV), VLP systems based on multiple light emitting diodes (LEDs) require lamps to be arranged with high density, which is not practical in realistic scenarios. Additionally, smartphones held in the human hand may rotate about the x-, y- or z-axis. This article proposes a tilted receiver camera correction method for indoor VLP systems to eliminate the additional positioning errors caused by rotation. Furthermore, the proposed method can suppress the positioning errors when part of the LED light is blocked, and can therefore enhance the robustness of the VLP system. The experimental results show that the proposed VLP method can achieve average positioning error within 7 cm when more than 40% of the LED image is captured, and can achieve average positioning error of 3.9 cm when more than 90% of the LED image is captured.
An indoor positioning algorithm is presented that uses a single rectangular visible light communication (VLC)-modulated LED as a transmitter and the CMOS image sensor of a smartphone camera as a ...receiver. The real-world location of the LED is transmitted as a VLC signal that is decoded by the smartphone using optical camera communication (OCC). Then the location of the smartphone is calculated by finding the camera pose using the perspective-n-point algorithm on the real-world coordinates and corresponding image coordinates of the LED. The algorithm is experimentally evaluated as a real-time application running on a smartphone. The experimental results show that the algorithm can achieve an average 3D positioning error of less than 5 cm for an arbitrarily tilted smartphone.
Fibronectin leucine-rich repeat transmembrane proteins (FLRTs) are cell-adhesion molecules with emerging functions in cortical development and synapse formation. Their extracellular regions interact ...with latrophilins (LPHNs) to mediate synapse development, and with Uncoordinated-5 (UNC5)/netrin receptors to control the migration of neurons in the developing cortex. Here, we present the crystal structures of FLRT3 in isolation and in complex with LPHN3. The LPHN3/FLRT3 structure reveals that LPHN3 binds to FLRT3 at a site distinct from UNC5. Structure-based mutations specifically disrupt LPHN3/FLRT3 binding, but do not disturb their interactions with other proteins or their cell-membrane localization. Thus, they can be used as molecular tools to dissect the functions of FLRTs and LPHNs in vivo. Our results suggest that UNC5 and LPHN3 can simultaneously bind to FLRT3, forming a trimeric complex, and that FLRT3 may form transsynaptic complexes with both LPHN3 and UNC5. These findings provide molecular insights for understanding the role of cell-adhesion proteins in synapse function.
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•The crystal structure of the LPHN3/FLRT3 complex reveals the binding interface•Mutations at the binding interface disrupt the interaction of FLRT3 and LPHN3•LPHN, FLRT, and UNC5 form a trimeric complex•LPHN3/FLRT3 and FLRT3/UNC5 mediate formation of intercellular contacts
FLRTs, LPHNs, and UNC5s are families of interacting neuronal cell-surface receptors that mediate brain development. The LPHN3/FLRT3 structure, reported by Lu et al., reveals that LPHN3 binds to FLRT3 at a site distinct from UNC5. FLRT3 simultaneously binds to LPHN3 and UNC5, and forms a trimeric complex.
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