Apple Inc.
  • Cupertino, United States
Recent publications
This work proposes a multimetal gated (MMG) architecture to improve the linearity of AlGaN/GaN high-electron-mobility transistor (HEMT). The general idea of this architecture is to use different gate metals along the width of the device. Through experimentally calibrated technology computer-aided design (TCAD) simulation, a selection of metals along with widths that yields the lowest value of third-order transconductance ( $\textit{g}_{\textit{m}\text{3}}$ ) has also been estimated. Single-tone large-signal simulation of proposed device exhibits an output-referred 1-dB compression point ( $\textit{P}_{\text{1~dB}}$ ) of 1.81 W/mm, a saturation output power ( $\textit{P}_{\text{sat}}$ ) of 6.91 W/mm, and a maximum power added efficiency (PAE) of 65%, all of which are better than simulations of standard/baseline device structures. Two-tone large-signal simulation shows excellent linearity performance when biased at deep class AB showing OIP3/ $\textit{P}_{\text{dc}}$ of 13.7 dB, which is 6.3 dB higher, and IMD3 of $-\text{45.7}$ dBc, which is 12.9 dB lower than baseline device at $\textit{V}_{\text{DS},\textit{Q}}=\text{28}$ V and $\textit{I}_{\textit{D},\textit{Q}}=\text{73}$ mA/mm. These performance matrices attest to the improved linearity performance of the proposed device compared to conventional planar AlGaN/GaN HEMT.
Disclosure: M. Varma: None. M. Eghbali: None. D. Hung: None. A. Sahai: None. Background: Metformin, commonly used medication to treat Type II Diabetes Mellitus (DM) improves insulin sensitivity, reduces glucose production in liver and absorption by intestines. Type II DM patients often have higher BMI with increased incidence of sleep apnea. Metformin consuming patients sometimes report insomnia. Blood glucose levels affect sleep duration; therefore Metformin-related changes in blood glucose levels may affect sleep. Metformin prescriptions grew from 40 million in 2004 to 90 million in 2020. This has improved long term vascular complications outcomes in diabetics. Coincidentally the number of patients using sleeping aids has increased. Melatonin sales have doubled since 2004, approximating 821 million USD in sales in 2020. With diabetes and Metformin each causing significant changes in sleep, we aimed to examine sleep architecture in known diabetic patients on Metformin presenting with excessive daytime sleepiness and fatigue. Hypothesis: We hypothesize that Metformin affects sleep and influences sleep architecture in diabetic patients. Methods: Sleep architecture in 29 Type II DM patients taking Metformin, with symptoms of excessive daytime sleepiness, snoring, and fatigue was examined. Patients underwent overnight polysomnography which included six channel EEG, Electrooculogram, Electromyogram EKG, and pulse oximetry, respiratory and flow monitoring in a sleep lab. Sleep staging done using AASM guidelines. Data on age, gender, BMI, medications and sleep stages N1, N2, N3 and REM was collected. Data analyzed and shown as mean + SD, t test p<0.05 significant. Results: All patients had OSA diagnoses per AASM guidelines. The average age of patients with DM and OSA on Metformin therapy was 63 years, average BMI was 36. AASM stage distribution was N1 2.69 % + 0.02, N2 59.31% + 0.15, N3 12.22 % + 0.09, (Normal 25%) with 5.71% +0.06 REM sleep (normal 25%). All stages of sleep were reduced with significant reduction in deep sleep (N3) and REM sleep. Conclusion: Diabetic patients on Metformin had alterations in sleep architecture with significantly reduced restorative phases of deep and REM sleep. Sleep apnea reduces N3 and REM sleep, but diabetic pts had a more significant decrease. Although Metformin improves long term outcomes in diabetes associated complications, it alters sleep patterns. Altered sleep patterns further modify insulin release and over prolonged periods worsen glycemic control. Often patients on Metformin need additional medication like insulin for metabolic control. In part the progression of insulin resistance can be from altered sleep. Better understanding the effects of Metformin on sleep is needed to prevent long-term deteriorating effects on sleep while maintaining effective metabolic control. Presentation: Friday, June 16, 2023
A serrodyne modulator (SM)-based fractional frequency synthesizer is presented. The SM receives its input signal with large deterministic jitter (DJ) from a multiplexer (MUX)-based fractional divider, and by employing linear sawtooth modulation of delay, attenuates the DJ, achieving low-noise fractional frequency synthesis. With a small footprint (0.01 mm $^{2}$ in 65-nm CMOS), it is ideal for multi-output clock generation, fast frequency switching, and spread-spectrum clocking (SSC). With an on-chip phase-locked-loop (PLL)-generated 5 GHz signal as input, and a 2.4899 GHz output, the circuit achieves $\ge$ 7.2 $\times$ reduction in the peak-to-peak DJ (DJ $_{\mathrm{PP}})$ . With an external 8.7 GHz input, and a 4.33 GHz output, DJ $_{\mathrm{PP}}$ reduction is $\ge$ 6.2 $\times$ . We also present a dynamic clocked-CMOS (C $^{2}$ MOS) quadrature divider to realize a low-power and low-jitter operation.
Hybrid and resonant switched capacitor converters show promise in a number of power management applications, but are subject to a range of challenges in control and implementation. In particular, hybrid topologies use a network of switched flying capacitors to reduce voltage stress on switching devices and energy storage requirements of inductor(s). However the increased order of system dynamics can lead to problems with voltage balance and regulation of the unique flying capacitor voltage states, leading to higher voltage stress and other undesirable effects. This work presents a simple yet comprehensive state-space analysis of hybrid topologies which can be used to predict and control system dynamics including voltage imbalance phenomena. The model affords new perspectives on modern-control metrics through a condition-number-based treatment, providing relative quantification of observability and controllability. Expanded opportunities such as a state observer and discrete time eigenvalues which govern natural balance are presented. The model is exemplified and validated using flying-capacitor multilevel converter (FCML) hardware prototypes.
Microarchitectural attacks, such as side-channel, exploit shared resources to leak sensitive information. Performing microarchitectural attacks on the cloud is possible once the attacker’s virtual machine (VM) is co-located with the victim’s VM. Hence, the co-location requirement with the victim limits the practicality of microarchitectural attacks on the cloud. In this work, we demonstrate that resource provisioning systems (RPSs) can be exploited to solve the co-location challenge of microarchitectural attacks in the cloud by deploying adversarial evasion attacks on RPSs to co-locate attackers’ VMs with victims’ VMs. Moreover, we discuss the adaptability of defense techniques proposed against adversarial attacks in the image classification domain on the RPSs.
Circular data clustering has recently been solved exactly in sub-quadratic time. However, the solution requires a given number of clusters; methods for choosing this number on linear data are inapplicable to circular data. To fill this gap, we introduce the circular silhouette to measure cluster quality and a fast algorithm to calculate the average silhouette width. The algorithm runs in linear time to the number of points on sorted data, instead of quadratic time by the silhouette definition. Empirically, it is over 3000 times faster than by silhouette definition on 1,000,000 circular data points in five clusters. On simulated datasets, the algorithm returned correct numbers of clusters. We identified clusters on round genomes of human mitochondria and bacteria. On sunspot activity data, we found changed solar-cycle patterns over the past two centuries. Using the circular silhouette not only eliminates the subjective selection of number of clusters, but is also scalable to big circular and periodic data abundant in science, engineering, and medicine. The resulting software package ‘CircularSilhouette’ is open source, freely available at</uri
Apple has developed the Liquid Retina XDR Displays with >8k mini‐LEDs, featuring extreme dynamic range with 1,000‐nit full‐screen‐sustaining luminance capability, 1,600‐nit peak luminance, and a 1,000,000:1 contrast ratio, with an ultra‐thin profile, suitable for portable system integration. Key technical enablers, including mini‐LED design, optimum LED zone layout, optical system design, and mini‐LED driving scheme will be reviewed.
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Cupertino, United States