|
|
|
|
|
|
Projects |
|
Reconfigurable
RF CMOS for Adaptive Spectrum-Agile Radios Our life is evolving towards
a world where micro-systems will add intelligence to almost every object that
surrounds us or that we use on a daily basis. Communication devices are no
exception. In the next5-10 years, we expect a seismic shift in radio design
that will break the spectrum availability bottleneck by having radios that
are aware of and can sense their environment and accordingly adapt their
transmission and reception parameters to best serve the user. The anticipated
radio’s cognitive skills will be handled by higher levels of
communication protocols. The adaptation and sensing skills are primarily the
function of the physical layer specifically, the radio frequency (RF) front
end module. The exponential growth in microelectronics capabilities has been
an enabler of the new spectrum sharing approach. However, the continuous
down-scaling in technology poses its own limitations on the physical layer
realization, and forces the RF design community to rethink traditional RF
circuits’ concepts and design procedures. This project deals
with new adaptive
circuits,
systems, and integration techniques, based on fundamental understanding of
the collective physical properties of active and passive devices. Our research has three
main thrusts: (1) The development of novel circuits that are applicable to
various scenarios of multi-frequency tuning and signal generation. (2) The formulation of a
systematic and modular approach to RF design that can form the foundation of
the new field of RF synthesis that is not bounded by the complexity
of the communication system. (3) The investigation of wafer-level 3D vertical
hyper-integration as an alternative approach to system-in-package (SiP) and system-on-package (SoP) for
future cognitive radios that support higher frequencies and multiple-antenna
systems. |
|
3D Integration of
Smart Antenna Transceivers The field of RFIC design
and manufacturing always faces constant pressure for increased performance
while still decreasing the chip size and accommodating more functionality in the
die and in the package. The long term goal has always been to integrate
everything on the same die (i.e, System-on-chip
SOC). However, cost and performance issues have forced the industry to
rethink its strategy towards using the package to incorporate some of the
functions. For example, while inductors in today’s technology have seen
tremendous increase in quality factor compared to a decade ago, their
performance is still limited. Several system-in-a-package (SiP) and silicon-on-a-package (SOP) techniques are
currently being pursued to incorporate passive elements in the package for
module-level integration. The above approaches target mainly low density circuit
architectures and limited numbers of passives. Multi-antenna
systems on the other hand, operate with multiple wideband transceivers with Tx and Rx RF paths functioning simultaneously. Clock
distribution and I/Q matching usually pose major challenges as the lateral
dimensions increase on chip (for SOC). They also require digital detection
techniques whose complexity grows with the antenna and constellation size. As
we move towards supporting millimeter-wave standards (24GHz and 60GHz) for
future communication systems, the increase in frequency will complicate
controlling interconnect parasitics due to the
small wavelength. Howver, the reduced antenna size
and spacing will make it possible to integrate them directly on chip and in
the package This project focuses
on using 3D wafer stack for full integration of smart antenna systems. RPI has one of the
most elaborate 3D platforms in the nation. However, while other packaging
techniques (SiP, MCM, LTCC)
are in production, 3D technology is mostly in research labs. Challenges in
thermal management, co-design and simulation tools, wafer bonding, and through
wafer via structures are still under investigation. The main research topics
in this project include assessing the performance improvement using 3D technology
and the limitations (EM isolation, cross-talk, etc) and their effect on
previously designed RF Front-end modules. Our main collaborators are Prof.
Ron Gutman and Prof.
James Lu of the Interconnect
Focus Center |
|
Hybrid
Free-Space-Optical/RF System for Vehicular Networks Vehicular ad-hoc networks (VANETs) are a
special form of mobile ad-hoc networks (MANETs)
that features high dynamics and frequent topology changes which require a high
degree of adaptability. So far, most of the focus in vehicular and mobile
networks in general has been on using RF technology (open-spectrum platforms
like 802.11b/a/g). However, the network in this case is still bound by the
provable limits in per-node throughput for lower GHz radio frequency-based
communication. In this project, we address combined physical and link layer
co-design (in collaboration with Prof. Shivkumar
Kalyanaraman , and Prof. Murat Yuksel ) to increase the data capacity of VANETs. Our group deals mainly with the physical layer implementation using
a hybrid RF/optical wireless system implemented in low cost
single-chip/module. Free space optical wireless (FSO) has emerged as a
promising high speed, wireless technology for short-distance network access,
but so far its applications have been limited to fixed nodes. . While the
expected data rates from both the millimeter-wave and the FSO link are
similar, other factor would determine the used technology such as the
robustness and the quality of service (error rate, packet lost, etc) as well
as the total power consumption in the communication link. Weather conditions
are also another factor; FSO links are highly susceptible to dense fog, smoke
and dust particles but relatively less vulnerable to rain conditions and the
opposite is true for RF systems. Thus for out-door highly mobile wireless
applications as in VANET, we target a hybrid millimeter-wave/FSO
communication to improve the overall wireless link/network availability.
However, both millimeter-wave and FSO require line-of-sight (LOS). Adaptive
electronically steered beams can be used to solve this issue, but increasing
the speed and the resolution of the beam coverage would result in increasing
the complexity of the system (power and multi-phase generation). The case is
even more complicated in vehicular communication applications where the high
degree of mobility requires ultra-fast LOS discovery and tracking. We use distribute LOS-tracking-task over multiple
frequency bands with different radiation patterns, which requires building
multi-band RF transceivers that spans the RF and the mm-wave bands. For simultaneous
transmission of optical and multi-band RF signals, we investigate different
integration of optical components in main stream silicon technologies. |
|
Digital
Power Amplifiers in CMOS Nanometer Technologies There is a tremendous desire for adaptive
(i.e. frequency band, modulation, etc) and high performance radio frequency
circuits that operates from low supply voltage and is implemented in scaled “digital” technologies.
The continuous reduction in supply voltage for emerging nanometer
technologies, poses major challenges on the linearity and output power
capability of the RF transmitter in general, and the power amplifier in
particular. This project studies novel power amplifier architectures geared
towards full digital implementation that can satisfy variable output power,
and linearity requirements while operating efficiently from sub-1V supply
voltages |
RF-Powered,
Micro-power Wireless Communication Circuits for Bio-Implantable and Wearable
Microsystems
With the growing
demand for implantable and wearable devices for health monitoring and
non-intervention diagnostic, there are higher restrictions on the power
consumption and the overall size of the used circuitry. The project focuses
on novel micro-power circuit architectures, and bio-compatible integration
techniques, as well as senor design. The primary application for this project
is studying patients with low back pain and spinal disorders to identify the mechanism by which
repetitive loading initiates and then exacerbates degenerative diseases of
the spine. The project is done in collaboration with Prof. Ledet
and Dr. Hisham Mohamed at Wadsworth labs.
|
[RPI][School of Engineering] [ECSE]
©
2006 Rensselaer Polytechnic Institute. All Rights Reserved
Electrical, Computer, and Systems Engineering Department
Rensselaer Polytechnic Institute -