Incorporating different wavelength (400 to 1000nm) LEDs, photoplethysmography (PPG) sensors allow wearable devices to monitor various health parameters such as heart rate (HR), oxygen saturation (SpO 2 ), and blood pressure (BP). Nowadays, PPG sensing technology at the wrist is well established. To cope with the large degree of motion turbulence presented at the wrist, PPG sensors use Green (Gr) LEDs together with multiple photodiodes (PD), and they are driven by wide-dynamic-range (DR) current-sensing front-ends [1]. It is attractive to use a near-infra-red (nIR) PPG sensor in a True Wireless Stereo (TWS), as the ear provides the best site to measure heart rhythm (more blood flow, constant distance from the heart, and less motion than at the finger or wrist). However, TWS requires a PPG sensor that is more stringent on size and power consumption (shown in Fig. 28.2.1). A promising solution [2, 3] is integrating an array of PDs with an ADC to dramatically reduce power while also providing monolithic integration. However, the limited DR (<80 dB) and the poor spectral responsivity remain challenging. This work advances [1] by demonstrating a CMOS monolithic PPG sensor, and improves spectral responsivity more than $4 \times (0.3\mathrm{A} /\mathrm{W}$ across 400 to 1000nm) compared to [2]. The sensor is fabricated by back-side illumination (BSI) CMOS technology providing 90dB DR (18dB improvement from [3]) while consuming only $24 \mu \mathrm{W}$ power and 5.5mm 2 silicon area.

Incorporating different wavelength (400 to 1000nm) LEDs, photoplethysmography (PPG) sensors allow wearable devices to monitor various health parameters such as heart rate (HR), oxygen saturation (SpO2), and blood pressure (BP). Nowadays, PPG sensing technology at the wrist is well established. To cope with the large degree of motion turbulence presented at the wrist, PPG sensors use Green (Gr) LEDs together with multiple photodiodes (PD), and they are driven by wide-dynamic-range (DR) current-sensing front-ends [1]. It is attractive to use a near-infra-red (nIR) PPG sensor in a True Wireless Stereo (TWS), as the ear provides the best site to measure heart rhythm (more blood flow, constant distance from the heart, and less motion than at the finger or wrist). However, TWS requires a PPG sensor that is more stringent on size and power consumption (shown in Fig. 28.2.1). A promising solution [2, 3] is integrating an array of PDs with an ADC to dramatically reduce power while also providing monolithic integration. However, the limited DR (<80 dB) and the poor spectral responsivity remain challenging. This work advances [1] by demonstrating a CMOS monolithic PPG sensor, and improves spectral responsivity more than $4 \times (0.3\mathrm{A} /\mathrm{W}$ across 400 to 1000nm) compared to [2]. The sensor is fabricated by back-side illumination (BSI) CMOS technology providing 90dB DR (18dB improvement from [3]) while consuming only $24 \mu \mathrm{W}$ power and 5.5mm 2 silicon area.

Abstract Objective: To propose a new anthropometric index that can be employed to better predict percent body fat (PBF) among young adults and to compare with current anthropometric indices. Design: Cross-sectional. Setting: All measurements were taken in a controlled laboratory setting in Seoul (South Korea), between 1 December 2015 and 30 June 2016. Participants: Eighty-seven young adults (18–35 years) who underwent dual-energy x-ray absorptiometry (DXA) were used for analysis. Multiple regression analyses were conducted to develop a body fat index (BFI) using simple demographic and anthropometric information. Correlations of DXA measured PBF (DXA_PBF) with previously developed anthropometric indices and the BFI were analysed. Receiver operating characteristic curve analyses were conducted to compare the ability of anthropometric indices to identify obese individuals. Results: BFI showed a strong correlation with DXA_PBF (r = 0·84), which was higher than the correlations of DXA_PBF with the traditional (waist circumference, r = 0·49; waist to height ratio, r = 0·68; BMI, r = 0·36) and alternate anthropometric indices (a body shape index, r = 0·47; body roundness index, r = 0·68; body adiposity index, r = 0·70). Moreover, the BFI showed higher accuracy at identifying obese individuals (area under the curve (AUC) = 0·91), compared with the other anthropometric indices (AUC = 0·71–0·86). Conclusions: The BFI can accurately predict DXA_PBF in young adults, using simple demographic and anthropometric information that are commonly available in research and clinical settings. However, larger representative studies are required to build on our findings.

A video graphics array (VGA) (640 $\times $ 480) indirect time-of-flight (ToF) CMOS image sensor has been designed with 4-tap 7- $\mu \text{m}$ global-shutter pixel in 65-nm back-side illumination (BSI) process. With a 4-tap pixel structure, we achieved motion artifact-free depth map. Peak current during exposure time has been reduced by current spreading with constant delay chain in the photo-gate driver. Column fixed-pattern phase noise (FPPN) from the constant delay chain is self-compensated by the proposed time-interleaving technique with the two inversely directional clock chains in the photo-gate driver. Quantum efficiency (QE) and demodulation contrast (DC) have been optimized by using appropriate optical engineering techniques with an optimal silicon thickness. As a result, QE of 34% at 940-nm near-infrared and high DC of 86% at 100-MHz modulation frequency have been achieved. In addition, motion artifact and column FPPN are successfully removed in the depth map. The proposed ToF sensor shows depth noise less than 0.57% with 940-nm illuminator over the working distance up to 4 m, and consumes only 160 mW for VGA output at 60 frames/s.

An Electronic Nose (F-Nose). capable of recognizing various odors and flavors, will add essential functions to Al robots [1], which traditional physical sensors such as cameras cannot provide. To date, a miniaturized E-Nose, as a chemical sensor, that is capable of sensing multiple gases below ppm-level, still remains a challenge. As a miniaturized but highly sensitive gas sensor platform, chemically coated resonators such as beam resonator [2], Surface Acoustic Wave (SAW) [4], and Film Bulk Acoustic Resonator (FBAR) [5] or integrated metal nanosheets with catalytic reaction [3] have been reported so far. However, none of them demonstrates 1 ppm sensitivity in response to a change in temperature (TEMP) and relative humidity (RH). This work advances the state-of-the-art by integrating a TEMP sensor, an RH sensor within a 4.0×3.7×1.0mm3 package allowing TEMP (15°C~ 35°C) and RH (30 ~ 70%RH) regulated sensing (ppm-level accuracy) of up to 4 different gases at once. With the help of dedicated AFE, chemically-tuned 2.5GHz Shear Horizontal (SH) SAW sensor responds to a 1 ppm Toluene gas within 200 seconds with a limit of detection (LoD) of 0.02ppm.

This paper presents an area-efficient temperature sensor with 1°C resolution based on a successive approximation algorithm. SoC requires several die temperature sensors to be integrated in a chip to manage the performance because die temperature directly affects leakage current level and performance of clock-based digital circuits. However, the size of temperatures sensor restricts the use of sensor in several places in a chip. The proposed area efficient temperature sensor uses only 0.13mm 2 in Samsung 45nm CMOS process to obtain 1°C resolution in the range from -15°C to 125°C. For accurate temperature sensing, SAR type algorithm and software-based 2-point calibration method are adopted. After the 2-point calibration, the temperature sensor achieves 1°C resolution with ±2°C accuracy and the power consumption is 360uW in 1.8V.

The emergence of wide channel bandwidth wireless standards requires the use of a highly linear, wideband integrated CMOS baseband chain with moderate power consumption. In this paper, we present the design of highly linear, wideband active RC filters and a digitally programmable variable gain amplifier. To achieve a high unity gain bandwidth product with moderate power consumption, the feed‐forward compensation technique is applied for the design of wideband active RC filters. Measured results from a 0.5 µm CMOS prototype baseband chain show a cutoff frequency of 10 MHz, a variable gain range of 33 dB, an in‐band IIP3 of 13 dBV, and an input referred noise of 114 µVrms while dissipating 20 mW from a 3 V supply.

A novel CMOS variable gain amplifier operating on current signals with a dB-linear gain control is presented. The gain control is achieved by multiplying a digitally synthesized exponentially varying control current signal by a differential input signal in the current domain. A current amplifier at the output sets the gain to the desired level. Current-mode operation allows for a reduced supply voltage by minimizing the voltage swing at the low impedance nodes of the circuit. Multiple circuit realizations for various blocks are presented allowing for designs meeting different constraints. Experimental realization of the variable gain amplifier shows the validity of the presented approach.

This paper presents a CMOS realization of a low voltage transresistance amplifier (LVTA) that is capable of operation at a supply voltage as low as 1.5V in a 5V CMOS technology. The circuit employs current feedback to reduce stacking of devices between the supply rails and to lower voltage signal swings, enabling low voltage operation. A R-2R ladder based variable gain amplifier (VGA) designed using the LVTA shows good linearity and a closed loop gain independent of bandwidth. Measured results for a prototype fabricated in a 0.5/spl mu/ CMOS technology are presented that experimentally demonstrates the proposed approach.

This dissertation describes the design and implementation of analog baseband filter and variable gain amplifiers (VGA) for wireless communication receivers. Since discrete high-Q image rejection and IF filters are eliminated, fully integrated receiver architecture demands baseband filters and VGAs which exhibit high linearity and wide dynamic range. In this dissertation, baseband chains for WLAN receivers and base station application, and low voltage transresistance based filter and VGA are presented. For WLAN receiver, three different baseband chains are introduced in chapter 3. First baseband chain is designed based on the feed forward compensated amplifier. Since the amplifier demonstrates high gain bandwidth and phase margin, the operation of filter is not affected by phase error and finite gain bandwidth of the amplifier. The feedforward compensated amplifier based filter and VGA are fabricated in 0.5μ CMOS technology and measured. Second baseband chain is designed based on fully differential buffer. The fully differential buffer shows the characteristics such as wide bandwidth, low output impedance, and high linearity, which are required in the design of wideband filter. Since identical buffer circuits are applied for the design of filter and VGA, design and optimization time are saved. This baseband chain is fabricated in 0.18 μ CMOS technology and test results are presented. Third baseband chain is designed based on the differential difference amplifier(DDA) and folded cascode ii amplifier. The DDA is used to implement wide band width buffer and folded cascode amplifier is used to design variable gain amplifier. The VGA of this baseband chain is fabricated in 0.5 μ CMOS technology and tested. In chapter 4, the band pass filter and VGA for basestation are presented. Since base station requires strong linearity and power compression behavior, the baseband chain must demonstrate high linearity and wide dynamic range. To achieve required linearity, power consumption is increased and the use of nonlinear components is minimized. Seven filter blocks and five attenuators are cascaded for the realization of the baseband chain. The baseband chain is fabricated in 0.5 μ CMOS technology. Finally, in chapter 5, the design of low voltage transresistance amplifier is presented. The amplifier is operated with 1.8 V supply in 5 V CMOS technology. The amplifier is implemented to design Tow-Thomas filter and R2R ladder based VGA. The amplifier and VGA are fabricated in 0.5 μ CMOS technology and tested.