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The spacetime-causality light-cone concept has been well-known since being introduced in Einstein’s Special Theory of Relativity, but it has not been explicitly explored in antennaarray electronics. To date, antenna-array radio frequency (RF) receivers have been constructed by replicating RF receiver chains at each array element. Ignoring shared frequency references required for RF-input down-conversion, each receiver in such designs acts independently of its neighbors until the received signals reach the array beamformer. While the use of independent receiver chains is convenient, it is not the optimum and does not take advantage of the additional opportunities afforded by the light-cone concept. This work presents the first experimental demonstration of noise and distortion (ND) shaping. The NDs originating in the receiver itself are spatio-temporally shaped away from the beamformer region of support (ROS), thereby permitting their suppression by the beamformer. The demonstrator is a 24.3–28.7-GHz 79.28-mW 4-port receiver for a 4-element linear antenna array implemented in 22-nm FDSOI CMOS. When shaping was enabled, the demonstrator provided average improvements to the noise figure (NF) of 1.6 dB, IP1dB of 2.25 dB, and IIP3 of 1.4 dB (compared to a reference design), and achieved NF = 2.6 dB, IP1dB = −18.7 dBm, and IIP3 = −12.5 dBm while consuming 19.8 mW/ch.

A four-sector competitive general equilibrium model has been developed with both male and female labour in presence of capital market distortion to analyse the effect of social transition on female labour force participation and gender-based wage inequality. The analysis finds that although gender wage inequality worsens in the existing structure, the consequence on female participation in the workforce depends on the stage of social transition. While it falls in the early stages, it begins to rise once a certain critical level of transition is crossed. Finally, we have advocated in favour of a policy that can effectively speed up the process of social transition thereby gender empowerment.

We report on the first experimental demonstration of five self-sustaining feedback oscillators referenced to a single multimode resonator, using piezoelectric aluminum nitride on silicon (AlN/Si) microelectromechanical systems (MEMS) technology. Integrated piezoelectric transduction enables efficient readout of five resonance modes of the same AlN/Si MEMS resonator, at 10, 30, 65, 95, and 233 MHz with quality ( ${Q}$ ) factors of 18 600, 4350, 4230, 2630, and 2138, respectively, at room temperature. Five stable self-sustaining oscillators are built, each referenced to one of these high- ${Q}$ modes, and their mode-dependent phase noise and frequency stability (Allan deviation) are measured and analyzed. The 10, 30, 65, 95, and 233 MHz oscillators exhibit low phase noise of −116, −100, −105, −106, and −92 dBc/Hz at 1 kHz offset frequency, respectively. The 65 MHz oscillator yields the Allan deviation of $4\times 10^{-{9}}$ and $2\times 10^{-{7}}$ at 1 and 1000 s averaging time, respectively. The 10 MHz oscillator’s low phase noise holds strong promise for clock and timing applications. The five oscillators’ overall promising performance suggests suitability for multimode resonant sensing and real-time frequency tracking. This work also elucidates mode dependency in oscillator noise and stability, one of the key attributes of mode-engineerable resonators.

This paper describes an adaptive noise generator circuit suitable for on-chip simulations of stochastic chemical kinetics. The circuit uses amplified BJT white noise and adaptive low-pass filtering to emulate the power spectrum and autocorrelation of random telegraph signals (RTS) with Poisson-distributed level transitions. A current-mode implementation in the AMS 0.35 $\mu \text{m}$ BiCMOS process shows excellent agreement with theoretical results from the Gillespie stochastic simulation algorithm over a 60 dB range in mean current levels (modeling molecule count numbers). The circuit has an estimated layout area of 0.032 mm2 and typically consumes 400 $\mu \text{A}$ , which are 73% and 50% less, respectively, than prior implementations. Moreover, it does not require any off-chip capacitors. Experimental results from a discrete board-level implementation of the circuit are in good agreement with theoretical predictions.

A general-purpose analog computing method is proposed to compute the continuous-time solutions of nonlinear partial differential equations (PDEs). The discrete-time difference operator in the standard finite difference time domain (FDTD) method is replaced by continuous-time delay operators that can be realized using analog all-pass filters. The resulting spatially discrete time-continuous (SDTC) update equations are realized using analog circuits which compute continuous-time solutions of the PDE with prescribed initial and boundary conditions. The proposed concept is demonstrated in simulation via an integrated circuit (IC) design of a nonlinear acoustic wave equation solver in 180 nm CMOS technology. Analog arithmetic operations (multiply, scale, and add) are realized in parallel using fully differential op-amps and analog multipliers. The proposed IC computes the PDE solution in parallel at 33 discrete spatial points and has a simulated bandwidth and power consumption of approximately 2 MHz and 3 W, respectively. The performance of the IC is simulated using foundry-supplied device models and quantified using i) the mean squared difference between the circuit simulation results and FDTD simulations, and ii) the noise to signal energy ratio. Acceptable accuracy is obtained, with error metric values varying between −7 and −30 dB for various configurations of the problem. Comparison of the custom analog IC simulations with MATLAB- and C-based FDTD code running on a modern workstation shows an expected average speedup of 205 × and 140 ×, respectively. [ABSTRACT FROM AUTHOR]

Face masks provide effective, easy-to-use, and low-cost protection against airborne pathogens or infectious agents, including SARS-CoV-2. Existing masks are all passive in nature, i.e., simply act as air filters for the nasal passage and/or mouth. This article presents a new “active mask” paradigm, in which the wearable device is equipped with smart sensors and actuators to both detect the presence of airborne pathogens in real time and take appropriate action to mitigate the threat. The proposed approach is based on a closed-loop control system that senses airborne particles of different sizes near the mask and then makes intelligent decisions to reduce their concentrations. In the current implementation, an on-board controller determines ambient air quality via a commercial particulate matter sensor, and if necessary activates a piezoelectric actuator that generates a mist spray to load these particles, thus causing them to fall to the ground. The system communicates with the user via a smart phone application that provides various alerts, including the need to recharge and/or decontaminate the mask prior to reuse. The application also enables a user to override the on-board control system and manually control the mist generator if necessary. Experimental results from a functional prototype demonstrate significant reduction in airborne PM counts near the mask when the active protection system is enabled.

The biological inner ear, or cochlea, is a sophisticated signal processing system that performs spectrum analysis over an ultra-broadband frequency range of ~20 Hz to 20 kHz with exquisite sensitivity and high energy efficiency. Electronic cochlear models, which mimic the exponentially-tapered structure of the biological inner ear using bidirectional transmission lines or filter cascades, act as fast and hardware-efficient spectrum analyzers at both audio and radio frequencies. This paper describes a cochlea-based digitally-programmable single-chip radio frequency (RF) spectrum analyzer in 65 nm CMOS. This “RF cochlea” chip includes a transmission-line active cochlear model with 50 parallel exponentially-spaced stages that analyzes the radio spectrum from 1.0-8.3 GHz. The outputs of all stages are encoded in parallel as delta-sigma ($\Delta - \Sigma $) modulated digital signals for real-time demodulation and analysis by a digital back-end processor. The chip consumes 418 mW and typically generates ~1 GS/s of total data at an ENOB of 5–6 bits. An artificial intelligence (AI)-driven single-channel cognitive radio (CR) receiver based on the RF cochlea has also been implemented and tested. [ABSTRACT FROM AUTHOR]

This paper presents a fully-integrated integer- $N$ frequency synthesizer that uses switched-gain control (SGC) within the phased-locked loop (PLL). Unlike other methods to improve PLL performance, the SGC method exploits the potential advantages of positive feedback within the main loop. The proposed SGC-PLL uses a supervisor with four switching regions in the phase plane to minimize the effects of circuit non-linearity within the PLL. This results in significantly lower settling time than conventional designs while maintaining similar phase noise. The design has been implemented in the UMC 180 nm CMOS process for an output frequency range of 1-16 MHz. Test results show that the proposed approach decreases the settling time by a maximum of 24.7% compared to a conventional PLL with the same loop parameters. [ABSTRACT FROM AUTHOR]

Early detection of symptoms is considered an effective approach to prevent deaths due to cardiovascular disease (CVD). Routine cardiac check-ups are therefore suggested by clinicians to detect CVD at an early stage. Unfortunately, existing methods for cardiac diagnosis are costly and time-consuming as in most of the cases, these facilities are available only in hospitals or clinics. In this article, a novel wearable ultrasonic imaging assembly is proposed for routine monitoring of the carotid arteries in an easy-to-use and economical way. Using standard B-mode ultrasound, which is suitable for wearable form factors, the device monitors intima-media thickness (IMT), which is a proven indicator of cardiovascular disease. The design parameters for all the essential hardware components of the proposed wearable imaging system along with an efficient algorithm for predicting IMT anomalies from ultrasound images are proposed. Finally, we describe a custom-designed prototype of the proposed system and demonstrate its capability in acquiring ultrasound images.

This paper describes a digitally programmable single-chip feedback ASIC for MEMS-referenced oscillators in the 0.4–15-MHz range. The chip contains a differential-difference low-noise amplifier (DD-LNA), a variable-gain amplifier (VGA) for analog gain control, several programmable-gain amplifiers (PGAs) for digital gain control, two second-order active $R-C$ band-pass filters (BPFs) for band selection, two all-pass filters (APFs) for phase shifting, an automatic level control (ALC) loop, and differential output buffers to allow interfacing with a wide variety of MEMS devices. Many on-chip parameters are digitally programmable via a standard serial peripheral interface (SPI) bus, thus allowing fine-grained optimization of the overall feedback transfer function. In addition, a compensation path with its own PGAs, a programmable attenuator, and an APF is provided for canceling electrical feedthrough within the chosen MEMS resonator. The chip was designed in 180-nm CMOS and consumes 4.6 mW. It was used to realize a ~6.9-MHz low-phase-noise (−105 dBc/Hz at 10 Hz) oscillator based on an ultra-high- $Q$ ($\sim 3.2\times 10^{6}$ at a bias voltage of 35 V) wafer-level vacuum-encapsulated Lamé mode single-crystal Silicon (SCS) MEMS resonator. Oven control and active temperature compensation improve the oscillator’s frequency stability to ±0.5 ppm with an Allan deviation of $1 \times 10^{-8}$ at $10^{3}$ s. Two such oscillators were also electrically coupled to realize a low-phase-noise quadrature reference oscillator suitable for complex-domain PLLs. [ABSTRACT FROM AUTHOR]

Two analog computing methods are proposed to compute the continuous-time solutions of one-dimensional (1-D) Maxwell’s equations. In the first method, the spatial domain partial derivatives in the governing partial differential equation (PDE) are approximated using discrete finite differences while applying the Laplace transformation along the time dimension. The resulting spatially discrete time-continuous update equation is utilized to design an analog circuit that can compute the continuous-time solution. The second method replaces the discrete-time difference operators in the standard finite difference time domain (FDTD) cell (Yee cell) using continuous-time delay operators, which can be realized using analog all-pass filters. Both methods have been simulated using ideal analog circuits in Cadence Spectre for the Dirichlet, Neumann, and radiation boundary conditions. The performance of the proposed methods has been quantified using: i) mean squared differences between the results and fully discrete FDTD simulations and ii) the noise to signal energy ratio. Both methods have been extended to design the analog circuits that compute the continuous-time solution of the 1-D and 2-D wave equations. The 1-D wave equation solver is simulated with a dominant-pole model (which better approximates the non-ideal circuit behavior) along with a propagation delay compensation technique. The experimental results from a simplified board-level low-frequency implementation are also presented. The key challenges toward CMOS implementations of the proposed solvers are identified and briefly discussed with possible solutions. [ABSTRACT FROM AUTHOR]

When you purchase medicine at the drugstore, you assume that it's what you think it is and that the active ingredient in the drug is present in the specified concentration. Unfortunately, your assumption might be all wrong. Counterfeit and substandard medicines have become widespread, particularly in low- and middle-income countries with weak regulatory systems. Indeed, according to the World Health Organization (WHO), one out of 10 medicines sold in developing countries should be considered “substandard.” Your drug could even be an outright fake. [ABSTRACT FROM AUTHOR]

This paper presents a programmable single-chip sustaining amplifier for MEMS-referenced oscillators. The chip integrates a low-noise amplifier, variable-gain amplifiers (VGAs), band-pass filters (BPFs), all-pass filters (APFs), automatic level control, and output buffers. It also contains a second signal path for background cancellation, i.e., eliminating the effect of electrical feedthrough capacitance of the MEMS resonator. Important parameters of each circuit block (e.g., VGA gain, BPF center frequency and quality factor ($Q$), APF phase shift, and so on.) can be set using bias currents, thus enabling fine-grained control over the overall transfer function. The amplifier was designed and fabricated in $0.5~\mu \text{m}$ CMOS. The chip was integrated with board-level current DACs (programmable via an I2C bus) and tested inside a vacuum chamber with various polysilicon (poly-Si) and single crystal (SC-Si) silicon comb-drive MEMS devices with resonant frequencies in the 10–90 kHz range. Oscillators referenced to a high- $Q$ (~13 000) SC-Si device had 20 dBc/Hz lower close-in phase noise (at 10 Hz) than those referenced to the low- $Q$ (~320) poly-Si device. Experimental results highlight advantages of the design, including automatic mode selection, background cancellation, control of feedback phase to optimize phase noise, and frequency locking to an external reference. [ABSTRACT FROM AUTHOR]

Illness caused by adulterated and counterfeit foods is a very common health issue for consumers. Food fraud also affects manufacturers by damaging their reputation, resulting in a decrease in market share and consumer trust. Thus, food safety has emerged as a critical issue for consumers and manufacturers alike. Fraudulent food products are often the result of opportunities taken by willful offenders who mislabel, falsify, and/or adulterate for economic gains. In some cases, the contents of a packaged food item may not match its label. In other cases, the labeling may be correct while the product itself is counterfeit. Thus, in today's market where most food items are industrially packaged prior to sale, it is important to prioritize the consumers' right to authentic and safe food products. The solution to this challenge is not to use expensive security measures that increase the final price, but to develop economical and portable food safety, quality assurance, and authentication devices for use at all stages of a food product life cycle-from production to consumption. Such devices would be a game-changer in the field of food safety.

Emerging millimeter-wave (mmW) wireless systems require beamforming and multiple-input multiple-output (MIMO) approaches in order to mitigate path loss, obstructions, and attenuation of the communication channel. Sharp mmW beams are essential for this purpose and must support baseband bandwidths of at least 1 GHz to facilitate higher system capacity. This paper explores a baseband multi-beamforming method based on the spatial Fourier transform. Approximate computing techniques are used to propose a low-complexity fast algorithm with sparse factorizations that neatly map to integer $W/L$ ratios in CMOS current mirrors. The resulting approximate fast Fourier transform (FFT) can thus be efficiently realized using CMOS analog integrated circuits to generate multiple, parallel mmW beams in both transmit and receive modes. The paper proposes both 8- and 16-point approximate-FFT algorithms together with circuit theory and design information for 65-nm CMOS implementations. Post-layout simulations of the 8-point circuit in Cadence Spectre provide well-defined mmW beam shapes, a baseband bandwidth of 2.7 GHz, a power consumption of 70 mW, and a dynamic range >42.2 dB. Preliminary experimental results confirm the basic functionality of the 8-beam circuit. Schematic-level analysis of the 16-beam I/Q version show worst-case and average side lobe levels of −10.2 dB and −12.2 dB at 1 GHz bandwidth, and −9.1 dB and −11.3 dB at 1.5 GHz bandwidth. The proposed multi-beam architectures have the potential to reduce circuit area and power requirements while meeting the bandwidth requirements of emerging 5G baseband systems.

We discuss the use of cochlear models for spectrum analysis at radio frequencies. We describe performance characteristics of such models, including noise, dynamic range, and frequency resolution. We show that the addition of phase information improves frequency estimation as compared to the use of amplitude information alone. In particular, the use of both amplitude and phase information in a novel nonlinear bio-inspired center-surround coincidence-detection stage simultaneously improves frequency estimation and implements a lowpass-to-bandpass transformation on cochlear outputs. In order to further improve frequency estimation we propose a novel wireless receiver architecture that is a broadband generalization of narrowband heterodyning systems commonly used in radio. We term this architecture cochlear heterodyning. It exploits the efficiency of cochlear spectrum analysis to perform parallel, multi-scale analysis of wideband signals and can be constructed with cochlea-like traveling-wave structures. When combined with our prior work on an RF cochlea, such architectures may be useful in cognitive radios for creating RF foveas that select narrowband components present within wideband, but spectrally sparse signals. The operation of RF foveas is analogous to how the eye foveates on narrow but interesting portions of an image. Analogies between spectrum analysis and the process of successive-subranging analog-to-digital conversion illustrate how successively finer frequency resolution is achieved in an RF fovea. Finally, we show that RF foveas can be used in feedback loops to perform interference cancellation. [ABSTRACT FROM PUBLISHER]

We investigate theoretical and practical aspects of the design of far-field RF power extraction systems consisting of antennas, impedance matching networks and rectifiers. Fundamental physical relationships that link the operating bandwidth and range are related to technology dependent quantities like threshold voltage and parasitic capacitances. This allows us to design efficient planar antennas, coupled resonator impedance matching networks and low-power rectifiers in standard CMOS technologies (0.5-μm and 0.18-μm) and accurately predict their performance. Experimental results from a prototype power extraction system that operates around 950 MHz and integrates these components together are presented. Our measured RF power-up threshold (in 0.18-μm, at 1 μW load) was 6 μW ± 10%, closely matching the predicted value of 5.2 μW. [ABSTRACT FROM AUTHOR]

We describe the design and CMOS implementation of a baseband spread-spectrum communication system using chaotic signals for spreading digital data. The communication system uses a new chaotic modulation scheme called modified differential chaos shift keying (M-DCSK). The M-DCSK scheme and its characteristics are analyzed for single user and multi user applications. The chaotic signals were generated using a simple and robust circuit. The dynamics of this chaos generating circuit are also studied. The spectral properties of the system are investigated and compared with theoretical expectations. [ABSTRACT FROM AUTHOR]