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137 results on '"Buckwalter, James F."'

1. Understanding Energy Efficiency and Interference Tolerance in Millimeter Wave Receivers

Author

Skrimponis, Panagiotis, Kang, Seongjoon, Khalili, Abbas, Lee, Wonho, Hosseinzadeh, Navid, Mezzavilla, Marco, Erkip, Elza, Rodwell, Mark J. W., Buckwalter, James F., and Rangan, Sundeep

Subjects
Electrical Engineering and Systems Science - Signal Processing
Abstract

Power consumption is a key challenge in millimeter wave (mmWave) receiver front-ends, due to the need to support high dimensional antenna arrays at wide bandwidths. Recently, there has been considerable work in developing low-power front-ends, often based on low-resolution ADCs and low-power mixers. A critical but less studied consequence of such designs is the relatively low-dynamic range which in turn exposes the receiver to adjacent carrier interference and blockers. This paper provides a general mathematical framework for analyzing the performance of mmWave front-ends in the presence of out-of-band interference. The goal is to elucidate the fundamental trade-off of power consumption, interference tolerance and in-band performance. The analysis is combined with detailed network simulations in cellular systems with multiple carriers, as well as detailed circuit simulations of key components at 140 GHz. The analysis reveals critical bottlenecks for low-power interference robustness and suggests designs enhancements for use in practical systems., Comment: Appeared at the Asilomar Conference on Signals, Systems, and Computers 2021

Published
2022

2. A Case for Digital Beamforming at mmWave

Author

Dutta, Sourjya, Barati, C. Nicolas, Dhananjay, Aditya, Ramirez, David A., Buckwalter, James F., and Rangan, Sundeep

Subjects
Computer Science - Information Theory
Abstract

Due to the heavy reliance of millimeter-wave (mmWave) wireless systems on directional links, beamforming (BF) with high-dimensional arrays is essential for cellular systems in these frequencies. How to perform the array processing in a power efficient manner is a fundamental challenge. Analog and hybrid BF require fewer analog-to-digital and digital-to-analog converters (ADCs and DACs), but can only communicate in a small number of directions at a time, limiting directional search, spatial multiplexing and control signaling. Digital BF enables flexible spatial processing, but must be operated at a low quantization resolution to stay within reasonable power levels. This decrease in quantizer resolution introduces noise in the received signal and degrades the quality of the transmitted signal. To assess the effect of low-resolution quantization on cellular system, we present a simple additive white Gaussian noise (AWGN) model for quantization noise. Simulations with this model reveal that at moderate resolutions (3-4 bits per ADC), there is negligible loss in downlink cellular capacity from quantization. In essence, the low-resolution ADCs limit the high SNR, where cellular systems typically do not operate. For the transmitter, it is shown that DACs with 4 or more bits of resolution do not violate the adjacent carrier leakage limit set by 3-rd Generation Partnership Project (3GPP) New Radio (NR) standards for cellular operations. Further, this work studies the effect of low resolution quantization on the error vector magnitude (EVM) of the transmitted signal.In fact, our findings suggests that low-resolution fully digital BF architectures can be a power efficient alternative to analog or hybrid beamforming for both transmitters and receivers at millimeter wave., Comment: Submitted to IEEE Transactions on Wireless Communications

Published
2019

3. Design and Analysis of Collective Pulse Oscillators

Author

Mukim, Prashansa, Dalakoti, Aditya, McCarthy, David, Segal, Carrie, Miller, Merritt, Buckwalter, James F, and Brewer, Forrest

Subjects
Allan deviation, collective dynamics, multiphase oscillators, nonlinear amplifiers, pulse logic, voltage-controlled oscillators, Computer Hardware & Architecture, Distributed Computing, Electrical and Electronic Engineering, Computer Hardware
Published
2020

4. Distributed Pulse Rotary Traveling Wave VCO:Architecture and Design

Author

Mukim, Prashansa, Dalakoti, Aditya, McCarthy, David, Pon, Brandon, Segal, Carrie, Miller, Merritt, Buckwalter, James F, and Brewer, Forrest

Subjects
Built Environment and Design, Engineering, Architecture, Voltage Controlled Oscillator, Rotary Traveling Wave Oscillator, pulse oscillator, transmission line stabilization, low duty-cycle multi-phase oscillator
Published
2019

5. Distributed Pulse Rotary Traveling Wave VCO: Architecture and Design

Author

Mukim, Prashansa, Dalakoti, Aditya, Mccarthy, David, Pon, Brandon, Segal, Carrie, Miller, Merritt, Buckwalter, James F, Brewer, Forrest, and Society, IEEE Computer

Subjects
Voltage Controlled Oscillator, Rotary Traveling Wave Oscillator, pulse oscillator, transmission line stabilization, low duty-cycle multi-phase oscillator
Published
2019

6. A Survey of GaN HEMT Technologies for Millimeter-Wave Low Noise Applications

Author

Miller, Nicholas C., primary, Arias-Purdue, Andrea, additional, Arkun, Erdem, additional, Brown, David, additional, Buckwalter, James F., additional, Coffie, Robert L., additional, Corrion, Andrea, additional, Denninghoff, Daniel J., additional, Elliott, Michael, additional, Fanning, Dave, additional, Gilbert, Ryan, additional, Green, Daniel S., additional, Herrault, Florian, additional, Heying, Ben, additional, King, Casey M., additional, Lam, Eythan, additional, Moon, Jeong-Sun, additional, Rowell, Petra V., additional, Siddiqi, Georges, additional, Smorchkova, Ioulia, additional, Tai, Joe, additional, Uyeda, Jansen, additional, and Wojtowicz, Mike, additional

Published
2023
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7. Integrated SOAs enable energy-efficient intra-data center coherent links

Author

Maharry, Aaron, primary, Andrade, Hector, additional, Misak, Stephen, additional, Liu, Junqian, additional, Xia, Yujie, additional, Wissing, Aaron, additional, Movaghar, Ghazal, additional, Arrunategui-Norvick, Viviana, additional, Chansky, Evan D., additional, Du, Xinhong, additional, Saleh, Adel A. M., additional, Buckwalter, James F., additional, Coldren, Larry, additional, and Schow, Clint L., additional

Published
2023
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9. Artificial Neural Networks for Power Match Modeling and Verification With a Novel D-Band Vector Load—Pull Bench

Author

Arias-Purdue, Andrea, Rowell, Petra V., Ahmed, Sajjad, Veetil, Suhas I., Urteaga, Miguel E., and Buckwalter, James F.

Abstract

We present an artificial neural network (ANN) model that predicts high-frequency, large-signal hetero-junction bipolar transistor (HBT) performance as a function of the load reflection coefficient and input power trained on a set of load—pull (LP) data that include delivered source power, output power, power-added efficiency (PAE), gain compression, input voltage, and output current. The ANN models are trained with data measured using a novel $D$ -band vector LP test bench at 130, 135, and 140 GHz. We analyze common-base (CB) and common-emitter (CE) indium phosphide (InP) HBTs and show that the CE HBT provides the highest impedance margin that maximizes PAE across a 10% bandwidth centered at 140 GHz. We fabricate CE HBT power cells and demonstrate state-of-the-art measured performance (36.2% PAE at 135 GHz at 4-dB compressed gain and 13.6 dBm). Using the ANN model trained at 130 GHz, transfer learning is accomplished for 135 GHz, 140 GHz, and prematched device datasets. The size of the ANN training sets is varied from 25% to 1% of the data collected, showing that our models are capable of predicting performance with an average rms error below 1.5% across sets. To our knowledge, this is the first demonstration of transfer learning within ANNs for transistor nonlinear modeling.

Published
2024
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10. Inductive Source Degeneration in 40-nm GaN HEMTs for Operation Above 100 GHz

Author

Arias-Purdue, Andrea, Guidry, Matthew, Lam, Eythan, and Buckwalter, James F.

Abstract

Source degeneration and neutralization techniques are investigated at millimeter-wave (mm-Wave) in gallium nitride (GaN) high-electron-mobility transistors (HEMTs). The role of thru-substrate vias for inductive source degeneration (ISD) is analyzed and modeled. A series of 40-nm GaN HEMTs with ISD are measured under small-signal, pulsed I–V and 94-GHz load pull. The ISD HEMTs demonstrate a 3-dB improvement in available gain at 83 GHz but also an unanticipated up to 75% increase in power density at 94 GHz with respect to the baseline devices. We discuss possible reasons for the performance enhancement. Device characterization to 200 GHz is presented.

Published
2024
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18. An integrated subharmonic coupled-oscillator scheme for a 60-GHz phased-array transmitter

Author

Buckwalter, James F., Babakhani, Aydin, Komijani, Abbas, and Hajimiri, Ali

Subjects
Integrated circuits -- Design and construction, Semiconductor chips -- Design and construction, Oscillators (Electronics) -- Usage, Phased array antennas -- Usage, Standard IC, Business, Computers, Electronics, Electronics and electrical industries
Abstract

This paper describes the design of an integrated coupled-oscillator array in SiGe for millimeter-wave applications. The design focuses on a scalable radio architecture where multiple dies are tiled to form larger arrays. A 2 x 2 oscillator array for a 60-GHz transmitter is fabricated with integrated power amplifiers and on-chip antennas. To lock between multiple dies, an injection-locking scheme appropriate for wire-bond interconnects is described. The 2 x 2 array demonstrates a 200-MHz locking range and 1 x 4 array formed by two adjacent chips has a 60-MHz locking range. The phase noise of the coupled oscillators is below -100 dBc/Hz at a 1-MHz offset when locked to an external reference. To the best of the authors' knowledge, this is the highest frequency demonstration of coupled oscillators fabricated in a conventional silicon integrated-circuit process. Index Terms--BiCMOS integrated circuits, coupled oscillator, mutual injection locking, phased arrays.

Published
2006

19. Data-dependent jitter in serial communications

Author

Analui, Behnam, Buckwalter, James F., and Hajimiri, Ali

Subjects
Microwave devices -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

We present a method for predicting data-dependent jitter (DDJ) introduced by a general linear time-invariant LTI system based on the system's unit step response. We express the exact DDJ of a first-order system and verify the validity of the solution experimentally. We then propose a perturbation technique to generalize the analytical expression for DDJ. We highlight the significance of the unit step response in characterizing DDJ and emphasize that bandwidth is not a complete measure for predicting DDJ. We separate the individual jitter contributions of prior bits and use the result to predict the DDJ of a general LTI system. In particular, we identify a dominant prior bit that signifies the well-known distribution of deterministic jitter, the two impulse functions. We also show a jitter minimization property of high-order LTI systems. We verify our generalized analytical expression of DDJ for several real systems including an integrated CMOS 10-Gb/s trans-impedance amplifier by comparing the theory and measurement results. The theory predicts the jitter with as low as only 7.5 % error. Index Terms--Data-dependent jitter (DDJ), deterministic jitter (DJ), jitter, jitter distribution, linear time-invariant (LTI) system, step response.

Published
2005

20. Synchronization design of a coupled phase-locked loop

Author

Buckwalter, James F., Heath, Ted H., and York, Robert A.

Subjects
Antenna arrays -- Design and construction, Circuit design -- Analysis, Circuit designer, Integrated circuit design, Business, Computers, Electronics, Electronics and electrical industries
Abstract

Coupled phase-locked loops (CPLLs) are introduced as novel circuits for phased-array antennas. Successful implementation relies on characterizing the synchronization behavior of CPLL circuits over a broad range of circuit parameters. Considering inherent time delay in the phase-locked loop demonstrates the degradation in the pull-in and hold-in ranges, as well as circuit instabilities, suggesting circuit parameter limits in a phased-array design. We compare the theoretical limits, in the form of analytic equations and numerical simulations, with measurements of the pull-in and hold-in processes of a 1.5-GHz prototype CPLL. Index Terms--Coupled phase-locked loop (CPLL), hold-in range, pull-in range, time delay.

Published
2003

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