Research Projects

Poster Presentations

Phase-Sensitive Optical Sensors for Frequency-Domain Biomedical Imaging
Team: Ruida Yun and Prof. Koomson
Collaborators: Prof. Sergio Fantini, Biomedical Engineering, Tufts University
Funding: National Science Foundation, Tufts FRAC Award

Optical techniques are rapidly advancing as a cost-effective and efficacious tool for functional studies and imaging of breast tissue, brain tissue, and skeletal muscle. Time-resolved optical techniques, using pulsed and sinusoidally modulated sources, allow explicit separation of tissue absorption and scattering coefficients. The application of CMOS integrated circuits to frequency-domain NIRS (FD-NIRS) instrumentation offers many advantages, including monolithic system-on-chip integration of optoelectronic devices and signal processing circuitry (for calibration, amplification, image correction, etc.), high-yield, multi-channel detection for improved spatial resolution, higher signal-to-noise ratio (SNR), and low-cost portable/wearable system development. In addition, miniaturization enables the realization of systems for concurrent measurement of multiple diagnostic modalities, thus improving diagnosis validity.

The objective of this research project is to develop a monolithically integrated optical sensor in CMOS for high-resolution phase and amplitude detection of RF-modulated optical signals for near-infrared spectroscopy applications.

3D Integrated Imaging Receivers for 10Gb/s Free-Space Optical MIMO
Team: Yiling Zhang, Juan Zeng, Prof. Koomson
Collaborators: Jun Liao, Shengling Deng, Prof. Rena Huang, Prof. James Lu, Rensselaer Polytechnic Institute
Funding: National Science Foundation

Optical MIMO (multi-input/multi-output) systems are emerging as a disruptive wireless access technology with the potential to overcome challenges faced by free-space optical (FSO) links in delivering on the promise of unlimited-bandwidth wireless channels. The use of source/detector arrays in optical MIMO processing combined with space-time coding to increase channel capacity and spectral efficiency is the sought-after solution to performance-limiting factors of FSO, namely fading due to scintillation and alignment requirements. To advance optical MIMO technology for FSO deployment requires a transformative approach to the development of multi-element imaging receivers with pixel bandwidths in the multi-GHz range, optimized optoelectronic devices integrated with complex signal processing circuitry in a single system-in-package approach.

The objective of this research project is to design, develop, and implement a new class of power-efficient imaging diversity photoreceivers, combining planar tessellated photodetectors with 3D silicon electronics for optical MIMO demonstrations at bit rates of 10Gb/s and beyond. The proposed work is a major departure from traditional imaging technology and is the first ever to consider imaging receiver design in excess of 10-Gb/s per pixel opening the door to a myriad of new applications to FSO systems, backplane communication, and optical interconnect technology. This research project makes several contributions to broadband wireless communication technology, including the development of novel low bias InGaAs MSM detectors for photodetection and mixed-signal integrated CMOS circuits for multifunctional operations (decision, amplification, and computing).

Low-power, Inductor-less 10Gb/s Transimpedance Amplifier Design
Team: Ruida Yun, Prof. Koomson
Collaborators: Analog Devices
Funding: National Science Foundation

Low-power, small footprint multi-Gb/s optical receivers are important circuit blocks for optical communications, high-speed optical I/O and multi-channel optical MIMO system applications. However, overcoming competing trade-offs to achieve low-power, high sensitivity, and high speed performance in CMOS is a design challenge. Several design techniques have been proposed to alleviate the bandwidth and noise degradation caused by the parasitic capacitance associated with the photodetector, ESD protection circuit, and opto-to-electronic packaging. The regulated cascode and shunt feedback are two conventional approaches to desensitize the channel bandwidth to input capacitance (CPD) by decreasing the TIA input impedance. This research focuses on the development of novel dual-feedback circuit topologies to extend the bandwidth of the receiver front-end without the use of large area on-chip inductors.

CMOS Imaging Diversity Receivers for Multi-Gb/s Free-space Optical Communication
Team: Yiling Zhang and Prof. Koomson

  • 10Gb/s Multipoint Imaging Receiver System in 90nm CMOS for Free-Space Optical Communication

For broadband wireless links, optical signals offer several advantages in terms of data rate, power efficiency, low transceiver complexity, networking security, and unregulated bandwidths. Optical wireless systems operating at 1.3-1.5μm wavelengths are desirable as eye safety requirements allowing higher transmit power levels in this band, which favors the use of hybrid topology integrating III/V o/e devices with CMOS circuits. Multipoint receivers with weighted-combiner circuit within the imaging receiver can effectively reduce the ambient noise and transmit power level compared to single element receivers. This receiver chip employs maximum ratio combining algorithm for multiple channels. Each channel consists of a front-end LNA, a SNR detector and signal processing circuits. The chip is implemented in a 90nm CMOS technology.

  • 6 Gbit/s Imaging Diversity Receiver Front-End Employing Select-Best Method in 180nm CMOS

Multi-point imaging diversity receiver configurations employing select-best combination can achieve high optical gain over a wide field-of-view (FOV) and significantly reduce the effects of ambient light noise, cochannel interference and multipath distortion. This imaging receiver consists of a seven channel transimpedance amplifier (TIA) array and a select-best circuit implemented in a 180nm CMOS technology. This imaging receiver is designed for flip-chip bonding to a custom InGaAs MSM (metal-semiconductor-metal) photodetector array. The select-best circuit employs a novel winner-take-all peak detector structure and demonstrates high-speed, high-precision reception.

Power-aware Integrated Control Systems for Soft-bodied Robots in Dynamic Environments
Team: Scott Pruessing, Prof. Koomson
Collaborators: Prof. Barry Trimmer (Biology), Prof. David Kaplan (Biomed. Eng.), Prof. Sonkusale (ECE), Prof. Robert White (Mech. Eng.), Prof. Jason Rife (Mech. Eng.), Prof Luis Dorfman (Civil/Env. Eng.), Gary Leisk (Mech. Eng.)

Biomimicry is a way of designing systems that are based around preexisting systems in nature. Biologically-inspired robotic systems have the potential to provide a new class of devices capable of performing tasks that no current machine can accomplish. This project is part of an interdisciplinary research initiative led by the Biomimetic Devices Laboratory at Tufts to carry out research into biologically-based technologies that use soft materials and to incorporate them into a new type of highly flexible robot. These machines will have applications in biomedical diagnosis and surgery, emergency rescue and exploration, and for monitoring or repairing space vehicles. This work focuses on the design of a low-power hardware interface for control of untethered soft-bodied robots. Tasks include: design of a wireless hardware control system with sensing capabilities, development of a graphical user interface and embedded software platforms, development of a power-aware controller for shape memory alloy actuators, and design of an ultra-low power, biologically-inspired IC neuron circuit in CMOS.

Lab Location:
Tufts Advanced
Technology Lab

200 Boston Ave.
Suite 2600
Medford, MA

Advanced Integrated Circuits and Systems Laboratory
Electrical & Computer Engineering, Tufts University
161 College Avenue, Medford, MA 02155
Tel: 617-627-2291  |  Fax: 617-627-3220  |  Email
Electrical & Computer Engineering  ::  School of Engineering  ::  Tufts Univeristy