Zoya Popovic - US grants

There is a need for compact, high-power sources for radar applications in the microwave and millimeter- wave range. The output power levels of solid-state devices in this frequency range are limited. A possible solution to be explored in this Research Initiation Grant is to coherently combine the outputs of hundreds of active devices that load a two- dimensional metal grid with a period equal to a fraction of a free-space wavelength. This active surface is an antenna as well as source. The devices can be MESFETs arranged in a gate-feedback configuration. This type of oscillator has a wide frequency tuning range, as is required in most applications. The oscillating active surface is backed with a tuning mirror that has an electrically variable reflection coefficient. This mirror is another metal grid loaded with varactor diodes. The capacitance of the diodes, and therefore the reflection coefficient of this tuning surface, is bias dependant. The mirror provides positive feedback to the oscillator surface, which is necessary for the devices to lock to a single mode. In a radar, for example, the signal is usually transmitted in pulses. In cases when the transmitter itself cannot be switched on and off at a high rate, a switching active surface can be used. This surface consists of a grid loaded with pin diodes, and it electrically switches the wave transmitted from the oscillator grid. This system is compact and light weight, since it consists of a stack of planar dielectrics loaded with solid-state devices that do not require large power supplies. It is versatile, for example, another active surface of Schottky diodes placed in parallel with the oscillator could have a variable phase shift for beam steering or beam forming applications, or can be used as a multiplier. In addition, the planar structure is suitable for wafer- scale or modular integration.

9350206 Popovic The research concentrates on quasi optical power combining of microwave and millimeter wave solid state devices. This technique allows the powers of a large number of individual devices to be combined in a compact, low cost, reliable high power source. Since the power combining occurs in free space, radiation and antenna design are addressed. Both amplifier and oscillator combiners are studied, using FETs or bipolar transistors. A design oriented analysis is developed for optimizing the radiating structure geometry towards different design criteria, such as power, bandwidth, efficiency or low noise. In the case of oscillators, nonlinear behaviour and injection locking of a large number of devices are studied. In the case of amplifiers, a high efficiency circuit topology is combined with the radiating structure in order to minimize heat sinking requirements. The goal of the work is to develop a compact, inexpensive microwave solid state source for a variety of applications, such as vehicular radar, mobile communications, wireless communications, atmospheric studies and remote sensing. ***

9512540 Mathys The proposed project requests major research instrumentation which consists of an RF channel simulator; microwave equipment for frequencies up to 40 Ghz including a spectrum analyzer, mixers, phase shifters, etc.; a frequency agile signal simulator; spread spectrum modems, fast A/D converters, fast DSP boards, and three workstations with simulation software. The equipment supports research and education in wireless and mobile communications. Planned research projects are in areas of channel modeling, microwave transmitter and receiver design and implementation, design and analysis of new modulation methods including transmission and reception diversity, implementation of novel concepts of detection, equalization and demodulation, design of multi-access protocols, and adaptation of routing and flow control algorithms for wireless environments. ***

We propose an integrated approach to minimizing power consumption of high-performance wireless communication systems. Our interdisciplinary approach will simultaneously address key levels of system design: minimum-energy communication techniques, energy-efficient signal processing electronics, high efficiency RF front-ends, and concurrent optimization methods. Our objective will be reached by developing design methodologies in the following research areas: (a) Modulation, detection, equalization, diversity, and resource allocation techniques for time and code-division multiple-access channels, which instead of concentrating on achieving channel capacity without regard to complexity, focus on minimum-energy communications while accounting for energy consumption for their implementation (b) Low-energy mixed-signal electronics to perform baseband functions such as data processing, coding, equalization etc. Our approach includes two components: digital logic with energy recovery using switch-mode RF circuits, and very low-power analog neural hardware. (c) High-efficiency integrated active antenna arrays, with a potential for manifold increase in overall DC to radiated carrier power efficiency. Our approach saves space and power by integrating high-efficiency switch-mode RF circuits with compact antenna arrays, allowing added functionality such as beam forming and (d) Concurrent design optimization over stochastic parameters, which can yield significantly lower power consumption in existing designs, and can take further advantage of the above methodologies. These savings will yield smaller, lighter, more reliable, and more capable wireless, hand-held, lap-top, and vehicular communication devices. The developed technologies and design methodologies will apply to mobile communication systems for the more than 25 million U.S. cellular subscribers as well as the millions of PCS subscribers over the horizon.

ABSTRACT EEC-9713368 MAHAJAN It is potentially feasible to use MicroElectroMechanical Systems (MEMS) technology to produce a device for trimming and providing the fine RF tuning adjustments needed in microwave/millimeter-wave integrated circuits. However, to date there has not been a reported demonstration of this technique in a MEMS device. This award supports a tie project between two Industry/University Cooperative Research Centers, Berkeley Sensors and Actuators Center (BSAC) at the University of California at Berkeley, and the Center for Advanced Manufacturing and Packaging of Microwave, Optical and Digital Electronics (CAMPmode) at the University of Colorado at Boulder, to develop a complete numerical/experimental characterization at microwave/millimeter-wave frequencies to derive an RF network model for MEMS. The methodology developed will be illustrated by implementation of the technique in a high-efficiency, switched mode microwave/millimeter-wave power amplifier for mobile and portable systems. CAMPmode is one of the leading university research centers in millimeter microwave packaging technologies, and BSAC is one of the leading research facilities in the development of MEMS technology. Together, these two Centers are well qualified to perform the proposed research, which is a project that neither Center has the capability to perform on its own.

9979355
Popovic

The development of smart active antenna array front ends with optical/digital processing back ends is proposed. The objective is to demonstrate that:
Smart (adaptive) antennas improve adverse interference effects in wireless
communication systems;
Active smart antenna arrays increase radiated power with reduced cost and power consumption, increase dynamic range, increase reliability and reduce cost, with built-in angle-of arrival detection;
Nonlinear optical components provide a simpler, potentially low-cost alternative to
digital signal processing and can be easily integrated with active microwave and
millimeter-wave arrays.

Interfering signals can be both spatially and temporally varying, causing interference to depend on time as well as on the physical location of the users and surrounding area. To mitigate interference problems, smart antennas create a spatial division multiple access network. Currently, there are not many commercially used smart antenna wireless systems, but several companies have used smart antennas to steer nulls and reduce interference, with increase range and capacity for the same transmitted power, with additional reduced maintenance cost. Smart antennas are also attractive to providers because they provide flexibility as systems grow. The approach taken in this proposal involves a new type of adaptivity for antenna arrays, through a new front end architecture, aided by unique capabilities of nonlinear optical processing. Specific arguments are that: (1) introducing adaptation at the analog front end eases the burden on the signal processing and adaptation becomes faster and more energy efficient with no cost increase (and possible decrease); and (2) nonlinear holographic optical processing can be efficiently used to perform part of the signal processing, with reduction in power consumption, size and cost..

This proposal focuses on systems with: (1) a transmit/receive active lens antenna array front end; (2) resonant electro-optic conversion; and (3) nonlinear active optical interconnects. In order to validate the goals of cost, size and power consumption reductions, a benchmark DSP adaptive processor (4) is proposed.

Interdisciplinary expertise in microwave/millimeter wave active antenna arrays, and nonlinear optics is needed, along with knowledge of the interference properties in a wireless channel and an understanding of the most practical adaptive algorithms. Students involved in this work will gain a broad knowledge base while working on challenging fundamental research problems. This is a collaborative effort with Qualcomm (a world leader in wireless communications), the French Thomson CSF (one of the leaders in optically controlled antenna beam-forming), and the Netherlands Foundation for RadioAstronomy (a scientific institution with strong interests in adaptive arrays).
***

9979400
Scharf

An integrated program of research is proposed for exploiting all available modes of diversity in the wireless channel. This requires the development of novel antennas for transmitting in diverse modes, digital receivers for exploiting these modes, and dynamic resources allocations for assigning them.

The primary challenges in this research are to manage and exploit the complex and time varying nature of the wireless communication channel, while meeting the power and bandwidth constraints of mobiles, base stations and networks. Hence, the work emphasizes integration of digital receivers for multiaccess communication with smart antennas and dynamic resource allocation. The smart antenna excites the temporal, spatial, and polarizational modes in the wireless channel. The multiuse receiver uses these modes to decode mobile users and to estimate channel parameters, which are used by the dynamic resource allocator to provide the required QoS to end users.

The design of a high frequency (e.g., 30 Ghz), high bandwidth radiating and receiving antenna which is agile in space, time, and polarization will involve numerical modeling, device construction, and testing of a prototype, based on prior experience with millimeter wave lens antennas. The design of multiaccess receivers which exploit available degrees of freedom will be based on actual device characteristics and on realistic scattering models for the channel. These receivers will be designed and implemented in reduced dimension subspaces. These subspaces are generated by resolving the real channel into a parallel combination of virtual diversity channels, using a special canonical space-time coordinate system. The designs will be evaluated using the software radio testbed currently under development at Eurecom.. The innovative aspect of the proposed dynamic network allocation work is the shared use of information at the physical and network layers to jointly optimize the use of channel and network resources for ensuring QoS. Dynamic resource allocation will exploit all the channel modes made available by the antennas and receivers. Estimates of signal to interference plus noise ratio (SINR) and bit error rate (BER) will be shared between the physical and network layers to dynamically allocate power and bandwidth across different channel modes, while keeping signaling and receiver complexity manageable. This integrated research program will influence the conception, development, and implementation of future wireless communication networks.

A key element of this project is the integration of student and faculty research activities at three universities: the University of Wisconsin, the University of Colorado, and Eurecom in France, the later a recipient of an IEEE Education Award for its innovative integration of mobile wireless, multimedia, and networking. The likelihood of success I this collaborative program is high, because working relationships between the three schools have been established through prior visits, sabbaticals, and collaborations.

The management plan is built around regular visits between laboratories at the participating schools, and joint advising of students working at technology boundaries. The integrated perspective developed in this research program will be incorporated into a new undergraduate wireless communication laboratory, a graduate colloquium course, and a wireless communication reading course. This work will impact the content of existing courses in communications, signal processing, networks, antennas, and electromagnetics.
***

ITR Small Proposal
0113385/0112591
Sayeed/Popovic

Abstract

Reliable and seamless wireless connectivity in varied environments is a necessary requirement for the rich and diverse communications of the future. Space-time processing has emerged as a key enabling technology for future wireless communications: signal space dimensions are fundamental to reliable communication and antenna arrays augment the traditional dimensions of time and frequency with the spatial dimension. While recent theoretical and technological advances provide a tremendous boon for modern communications, the state-of-the-art is far from realizing the full potential of space-time processing due to significant gaps in our current understanding on two fronts:

Fundamental mechanisms underlying the interaction of the space-time channel with the signal space in spatial, temporal, and spectral dimensions.

Jointly optimized design of front-end hardware, antenna arrays, and signal processing algo-rithms.

The overall goal of the work proposed here is an integrated approach to the design of antenna array hardware and space-time processing algorithms for significantly improved wireless link performance
at reduced cost and complexity.

0218744
Popovic

This proposal addresses design and implementation of adaptive RF front ends for the next generation communication systems that will require operation at several frequency bands. The adaptive RF front ends will be developed by a collaboration between the University of Colorado at Boulder (CU) with expertise in microwave high efficiency circuits, and the Georgia Institute of Technology (GIT) with expertise in tunable RF MEMS.

More specifically, this project will focus on the development of a multi-band RF power amplifier used in the transmitter sections of all communication hardware. The goal is to demonstrate adaptation of tuning impedances on the millisecond scale using MEMS switches for multiband transmitter operation (e.g., the 5.7 and 24-GHz unlicensed bands), resulting in a larger overall average efficiency and multi-band frequency coverage. For this reason, switched-mode PAs (classes E and F) will be tuned with a multi-band MEMS output circuit and a reconfigurable MEMS input circuit. Linearization using bias and drive control of multi-band high efficiency PAs will also be studied, with the main goal of proving that these amplifiers are advantageous for modulation schemes that require linearity. Results of this work will have direct impact on worldwide commercial wireless systems moving from 2G to higher standards in which RF front-ends must support multi-band operation under various modulation schemes. It could also potentially lead to revolutionary miniaturized load-pull systems that replace the bulky and very expensive load-pull systems currently available. The proposed solution adheres with the low-power, small-size, low weight and low-cost requirements of next generation communication systems.

The proposed effort covers a period of three years during which the following will be accomplished:

oDesign and demonstration of a multi-band impedance tuner using MEMS
oDesign and demonstration of a multi-band high-efficiency power amplifier using switched-mode topologies (such as classes E or F) with a simple switch between two output and input matching circuits
oStudy of linearization of multiband high efficiency saturated PAs using dynamic drive and bias control
oIntegration of the amplifier and tuner
oIntegration of transistor with tuners for miniaturized MEMS load-pull

The proposed research will be complemented by educational activities that will integrate the research findings into the curriculum of both universities and other related outreach efforts. GIT and CU will provide travel funds for the PIs to visit the collaborator and give seminars to undergraduate and graduate students each semester. The PIs plan to propose REU projects, in addition to UROP, SMART and SIRFs (undergraduate research and minority programs funded by our respective universities), so that GIT undergraduates work at CU in the summer, while CU students work at GIT for a semester, with the goal of a graduate student recruitment program between the two universities. The investigators will follow NSF's reporting requirements and will also publicize their results in peer reviewed journals and conferences.

ABSTRACT

This integrative systems proposal focuses on the optimized design of focal-plane arrays in the 100-300GHz range, with an integrated design methodology of hardware and image processing.
Intellectual merit of the proposal: In many applications of sub-millimeter and millimeter-wave imaging it is critical to acquire high-resolution images in real-time, and remove noise and distortions. New nonuniform sampling of the focal surface coupled with efficient image reconstruction algorithms will be investigated. Dual-polarization antennas coupled with optimized image processing algorithms will be designed. Noise removal and deconvolution algorithms specific to the limitations of FPAs will be studied.
Methods for designing low-loss quasi-optical components tailored to FPAs will be investigated. Antenna aperture efficiency will be improved using microlens-coupled antennas. Dual polarized antenna arrays with low polarization coupling; and multi-band nested antenna arrays with nonuniform periodicities will be designed. Design and fabrication methods will be investigated.

Broader impacts of the proposed work: This research will lead to the design of fast imaging techniques for the detection of non-metallic concealed weapons, and will have an impact on public safety. The technology developed will also have direct applications to astronomy, and medical imaging. This project will foster multidisciplinary collaborative research spanning areas of high-frequency analog quasi-optical techniques and image processing. The proposed research will be complemented by educational activities that will transfer the findings into a course. The investigators will disseminate their results in journals, through a regularly updated interactive web site and through a workshop that brings together all areas needed for millimeter-wave imaging.

ECS-0636650
R. McLeod, University of Colorado at Boulder

This new architecture requires an equally novel integration platform for hybrid electro-optic systems. The proposed platform can be thought of as "optical wire-bonding" in which arbitrary discrete RF or optical components are interconnected in 3D to form complex, dense circuits. This process is made possible by advanced photopolymers that can simultaneously encapsulate the individual hybrid subcomponents and can be photo-patterned in 3D to develop micron-scale gradient index features. These index features in the form of optical waveguides are aligned to the encapsulated hybrids by a custom 3D lithography system, avoiding all active alignment.
Intellectual Merit
This proposal presents a revolutionary integration technology for RF/optical components in the context of a hybrid wireless/optical communication system. The architecture supports multi-channel, mobile GHz bandwidth without the limitations of traditional spread-spectrum codes or adaptive beam-steered antenna arrays. The cornerstone of the communication architecture is a smart electro-optic node (SEON) that adaptively tracks multiple broadband mobile transmitters. Reception is performed with a small-aperture adaptive array automatically listening on as many channels as it has antenna elements; a scaling which is significantly better than current adaptive beam-forming systems.

Broader Impacts
The proposed hybrid circuits are fabricated on a single, inexpensive lithography station that, similar to rapid-prototyping processes, can fabricate complex single parts with no costly masks using only low-cost monomer. This enables both large economic impact in small production volumes and large-scale undergraduate educational use. The PI's will extend this educational impact via a new graduate course, ECEN 5004, Fundamentals and technology for RF-optical communication systems

Integrative, Hybrid and Complex Systems
Saeed Mohammadi, Purdue University
Zoya B. Popovic, University of Colorado at Boulder
COLLABORATIVE RESEARCH: A Heterogeneous Integrated, Self Powered Wireless System


Intellectual Merit:
This project considers the design and implementation of a wireless transceiver that is low cost, battery-less (i.e., does not require traditional batteries), miniaturized, sensitive, low power, and highly efficient. The research uses a recently developed heterogeneous integration technology to integrate an ultra-low power subthreshold complementary metal oxide semiconductor (CMOS) radio frequency (RF) receiver chip with a highly efficient power amplifier and embedded passive components. The integrated system can be used as a self-powered long-range and high data-rate wireless sensor node as well as an implantable miniaturized electronic system. Applications include monitoring in-vivo activities, nerve actuation, and drug delivery.


Broader Impact:
This research will impact research and education, as well as the marketplace. The research will be linked to multiple undergraduate and graduate courses at the collaborating institutions. Emphasis will be placed in attracting underrepresented undergraduate and graduate students through existing programs at the University of Colorado, including the "SMART" and "IMPART" programs and an Alliances for Graduate Education Program (AGEP) award from the National Science Foundation. This research will also be integrated with existing recruitment programs at Purdue University, an NSF Alliances For Graduate Education (AGEP) award, the NSF-supported Indiana Louis Stock Alliance for Minority Partnership (LSAMP), an NSF Integrative Graduate Education and Research Training (IGERT) award, a Department of Education Graduate Assistance in Areas of National Need (GAANN) award, and the Engineering Projects In Community Service (EPICS) program. The investigators will establish EPICS and graduate course projects. Research results will be disseminated broadly via publications in scientific journal and presentations at technical conferences.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The objective of this research is to develop a low-cost non-destructive, non-contact probing method for surface and sub-surface characterization of inhomogeneous materials and devices. New artificial and nano-material development requires fast, low-complexity and ultra-sensitive high-resolution characterization of materials, as well as defect detection during fabrication processes, with sub-micron spatial resolution. The approach focuses on combining a near-field microwave probing system with optical interferometry for topology sensing and correction.

The intellectual merit of the research stems from new electronic designs through investigation of fundamental limitations, and miniaturization through integration, enabling a scalable solution. Electromagnetic and noise analysis, design of calibration test structures, and related metrology, are used to understand the fundamental limitations on sensitivity and design miniaturized active probes. Different penetration depths enable sub-surface probing by using different frequencies.

The broader impacts of the proposed research are to provide a fast and inexpensive tool for detection of defects for new material technologies and rapid classification of samples into batches for yield and uniformity analysis. Such a tool can impact material manufacturing technology and maintain the nation?s leadership in this area. An impact on the institution will be development of core competency in the field and interactions with existing research projects and multidisciplinary education. A new module will be added to existing K-12 outreach, entitled Electromagnetic Eyes, where children ?see? a coin through an opaque cover. A successful recruiting effort which focuses on under-represented groups will expand, and the international collaboration with one of the top engineering universities in Germany, Technische Universität München, developed.

Abstract (Proposal No. 1202193)


Intellectual Merit: This proposal addresses a new method of integrated design and implementation of an external passive radiometer for monitoring internal body temperature. The goal for the proposed research is to develop a temperature-monitoring device with a potential of being wearable, disposable and inexpensive. The motivating applications are in several areas: (1) medical diagnostics, e.g. monitoring infant brain damage, arthritis, detecting localized tumors and monitoring temperature rise during hyperthermia treatment; (2) monitoring people under stress, e.g., athletes during training/competition, emergency workers and military personnel in hazardous conditions; and (3) manufacturing, e.g., monitoring internal temperature of foods during the manufacturing process. The specific issues addressed in the project are the basic understanding of principles and limitations of near-field microwave radiometry, an engineering approach for monitoring internal body temperature in an environment with radio interference. The anticipated result of the research is development of a wearable and ultimately disposable radiometric thermometer for a wide range of applications, with a spatial resolution on the order of 1cm and temperature resolution of 0.1K. The radiometer data can easily be transmitted using a low-power wireless transceiver for further off-body processing.


Broader Impacts: The broader impacts of the proposed research are transformative in several areas. The technical goal of providing a new method of non-invasive monitoring of internal temperature, when applied to a human body, can lead to on-time preventive treatment. Not having access to internal body temperature is not only a problem for various diseases, but also has a considerable impact in national security (military personnel under heavy training; emergency personnel in hazardous conditions). In terms of education and outreach, the broader impacts include multi-disciplinary education at the undergraduate and graduate level, spanning areas of high-frequency analog circuit design, electromagnetic simulations, and metrology. An impact on the institution will be development of core competency in the field and interactions with existing research projects. The PI has been active in outreach, and related to this proposed work plans to add a new module to the existing K-12 outreach, entitled Hot inside?, where children can use a radiometer to ?see? a hot spot inside an object. A collaboration with NIST-Boulder will enhance the metrology component of the research. The international component of the proposed effort includes a collaboration with ETH-Zurich (Switzerland), in the form of student exchanges, software donations and no-cost participation.

This collaborative proposal develops a new method of integrated design of exposure and excitation of electromagnetic (EM) fields in the UHF and low microwave frequency range for next-generation magnetic resonance imaging (MRI) at high magnetic fields (B>3T). High magnetic fields improve the signal-to-noise ratio in MRI, and are accompanied by increased RF frequencies, which can lead to propagating modes inside the bore with a patient. For example, at 7T, the required RF frequency is in the 300MHz range, while a bore that fits a human is at least 60cm in diameter, making it above the cutoff frequency for at least one mode of the bore viewed as a waveguide, when loaded with the body. The travelling waves can potentially be advantageous in terms of a more comfortable environment for patients, larger field of view, imaging to-date MRI inaccessible areas, and enabling new spatial encoding schemes and a variety of mode sensitivity profiles. It is important, however, to be able to design the modes in the bore for better excitation field profile uniformity and control of power exposure to the body.
Intellectual Merit: The principal goal of the proposed research is development of design methodologies for RF field profiles and associated cavity wall surface impedances and excitation probes, enabled by extremely fast and accurate full-wave higher order computational EM simulations of large body-loaded cavities. Several of the designs will be fabricated, characterized, and transitioned to clinical and research collaborators at Harvard University for imaging research. The specific issues to be addressed are: (a) Understanding the fundamental principles and limitations of radio-frequency electromagnetic field profile design for next-generation travelling-wave, high-field MRI; (b) Developing an engineering approach for modification of surface impedances in body-loaded bore cavities, enabled by extremely fast and reliable simulation techniques; (c) Solving the problem of proper field profile excitation (probe) design integrated with loaded cavity; (d) Evaluation and control of specific absorption rates inside the phantom, animal, or human; and (e) Implementing the designs for several clinical and research MRI machines operated by collaborators at Harvard University (these implementations are not supported by the proposed grant). The project will investigate periodic or quasi-periodic surface impedance structures in the form of printed resonant structures or three-dimensional dielectric-metal artificial surface impedances, and different types of excitations combining wire dipoles and loops, patch-antenna probes with coaxial feeds, and cavity backed slot exciters (multiple probes for different modes will be incorporated with switching circuits). Other (non-MRI) applications of the resulting research in loaded multi-mode cavities include areas from low-power wireless power delivery in closed spaces to high-power advanced smart microwave ovens. Broader impacts of the proposed work on basic science and engineering support the nation's science and technology advantage. The anticipated results will provide a new method of medical imaging with more comfort for patients, and an increased field of view, sensitivity, and functionality. Broader impacts on society are especially warranted by growing needs for such improved medical diagnostic tool. Because of the potential to change the way medical diagnostics using MRI is done in the longer term, the proposal may be considered transformative in its nature. Multi-disciplinary education at the undergraduate and graduate levels, spanning areas of high-frequency analog circuit design, EM simulations, bio-EM, and metrology, will make an impact on two top institutions in the state of Colorado, strengthening the existing core competency. The PIs at both institutions have been active in outreach, and related to this proposed work plan to add several new modules to the existing K-12 outreach, with hundreds of middle-school children on "Electric Field Trip" visits. A recruiting effort at all levels focusing on underrepresented groups will continue to enrich the educational environments. Collaborations related to medical applications with Harvard and Intermountain Neuroimaging Consortium, international collaboration with XLIM, University of Limoges, in France, and industry partnership (NXP) are evidenced by no-cost technical participation and insertion into clinical studies, student exchanges, and hardware donations.

The rapid growth of wireless communications and sensing demand more efficient use of the precious frequency spectrum, imposing tougher constraints on the radio-frequency hardware. To responds to this challenge, transformative radio front-end designs are needed. This collaborative project proposes new classes of electrically-tuned RF front-ends for efficient, on-demand spectrum access/sharing in spectrally-congested environments. Although 5G networks, devices and communication schemes have been extensively discussed, they are not yet appropriately defined, deployed and fully exploited. The goal of this project is to develop RF front-ends with multiple levels of transfer-function adaptivity enabled by electrically-controlled materials and new types of RF filters that can: (a) arbitrarily define the band of operation; (b) efficiently transmit/receive under dynamic spectrum allocations; and (c) co-exist in unlicensed bands. The co-design of filters with other transceiver components such as antennas, power amplifiers and low-noise amplifiers will increase power efficiency while reducing the size of RF front-end. The multi-level adaptivity and circuit co-design are fundamental methodology advances which will allow transformative improvements in hardware performance. The proposed research will be carried out by a unique multi-institute team from the University of Colorado at Boulder (UCB) and the University of Michigan (UM), with complementary expertise in RF filters, active circuits and microfabrication. The outreach components of this project focus on: (i) broadening the undergraduate experience in practical training and research through NSF Research Experiences for Undergraduates (REU) program, as well as university and industry-funded opportunities for students; (ii) enhancing the UCB/UM curriculum with new class contents integrating the proposed research results; (iii) increasing the participation of underrepresented undergraduate/graduate students by active recruiting through organized events and university scholarship programs; and (iv) outreach efforts for K-12 students through existing infrastructure at UCB/UM such as the well-established Science Discovery Program at UCB.

The technical objective of the proposed collaborative research is to investigate new classes of fully-reconfigurable co-designed RF front-ends that will facilitate efficient spectrum access at frequencies below 6 GHz, where the spectrum is most congested. For 5G applications, the millimeter-wave frequency allocations allow for larger bandwidths, but are accompanied by higher atmospheric loss and higher cost. The proposed hardware developments will exploit the multi-functional voltage-controlled properties of barium strontium titanate (BST) as structural materials for bulk acoustic-wave resonators (FBARs) and electrically-tuned reactive elements. This allows for significantly increased functionality through: (1) new filter design methodologies and tuning schemes for continuous and analog RF tuning; (2) high quality factor FBARs with intrinsically-switched transfer function; (3) co-designed RF passive and active circuit elements resulting in miniaturization and reduced loss; and (4) frequency-selective agile harmonic terminations to increase the circuit efficiency and dynamically adapt to RF signals with diverse spectral and spatial content. The collaborative research effort will lead to the development of switchless transmitter/receiver front-end chains with multiple levels of transfer function adaptivity capable of achieving higher efficiency and lower noise than conventional approaches. The proposed tuning speeds on the order of hundreds of ns will allow dynamic frequency coverage in 0.8 - 6 GHz and adaptive multi-band front-end chains.

The internal temperature of the human body can be considerably different from that of the skin. Athletes, soldiers, firefighters, and astronauts under heavy training or challenging ambient conditions can have abnormal core temperatures, resulting in hyperthermia, and heatstroke, making internal body temperature monitoring important. The difference between internal temperature (e.g., heart) and skin varies up to 2 degrees Celsius over the 24-hour circadian cycle for a healthy person. A disrupted circadian rhythm can result in seasonal affective disorder, type-2 diabetes, and heart disease. Internal tissue temperature is relevant in cancer hyperthermia (heating) treatment, and hypothermic (cooling) neo-natal brain rescue. Currently, a noninvasive, wearable and inexpensive method of measuring internal body temperature (IBT) does not exist. The goal of the proposed research is to study and develop an internal body temperature monitoring device that has the potential of being disposable and inexpensive. The motivating applications are in areas of: (1) medical diagnostics and monitoring; (2) medical treatment; and (3) forensics, organ transportation and artificial tissue growth. The proposed device lends itself to internet of things (IoT) integration in hospital, home and ambulance settings. Additionally, the method applies to industrial applications such as monitoring temperature of food, mixed waste, etc. The PI is active in outreach, and related to this proposed work plans to engage with local schools through the Timmerhaus Ambassador program, and by informing athletes and working with the University of Colorado Sleep and Chronobiology Laboratory. The international component of the proposed effort includes a collaboration with Carlos III Univ. in Madrid, evidenced by proposed student exchanges and no-cost participation in tissue grafting applications.

A new method of integrated design, implementation and calibration of an external passive radiometer will be studied and developed for monitoring internal body temperature by measuring total black-body power in a narrow frequency range with relatively long integration time. The frequency of operation is chosen for low interference (quiet bands) and high skin depth in tissues. The proposed basic research builds on a successful proof-of-concept that unveiled challenges that need to be solved before the method can be applied. This proposal focuses on the following topics:
1. Comparing radiometer architectures and determining the best architecture to achieve improved temperature resolution over a small (few degrees C) temperature range on a chip, at frequencies that have low RF interference, e.g. the 1.4 GHz quiet band.
2. Investigating the fundamental limits on spatial resolution, and designing probes and probe arrays that enable high resolution. Near-field phased array probes are proposed for improving transversal spatial resolution, while multi-frequency probes show promise for improved depth resolution, with a goal of 1cm in all three dimensions.
3. Tissue layer thicknesses and electrical properties vary on different parts of the body and between humans. In order to estimate internal temperature, a one-time time-domain reflectometry probe array measurement that determines tissue layer characteristics is proposed, for improved temperature resolution estimation.

In summary, the intellectual merits include contributions in high-frequency circuit and system design, near-field phased array probes over complex layered media and time-domain layer characterization.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

The Terahertz (THz) Measurement Facility, a collaboration between New York University, University of Colorado at Boulder, University of Nebraska–Lincoln, and Florida International University, is a laboratory to support basic measurements of devices, circuits, materials, and radio propagation channels at the highest reaches of the radio spectrum. While today’s cellular telephones and wi-fi networks operate at frequencies below 100 GHz, there is great promise for greater download speeds and vast new wireless applications by moving up to the underexplored sub-THz and THz frequency bands – frequencies from 100 to 500 GHz. This MRI grant provides a facility to explore wireless components and systems at these new frequencies. <br/><br/>This grant supports three areas of measurement: a) Radio Frequency Integrated Circuit (RFIC) measurements, b) radio propagation and channel modeling, and c) metrology and calibration, over the contiguous frequency range of 75 GHz to 500 GHz. A unique concept of this facility is the loan of equipment, where institutions may borrow THz components to conduct remote field measurements for wireless communications, propagation, and sensing. Evolving semiconductors and integrated circuits, as well as the next-generation electronics based on layered materials (e.g., graphene), will be measured at THz bands using the RFIC probe station. This facility will have a broad impact on the future of communications, materials, and devices. The creation of new calibration and metrology approaches are vital for accurate and repeatable measurements throughout the US research community in this underexplored range of frequencies. The study of nanotechnology devices using the RFIC probe station will unleash new capabilities in sensing, communications, and computing that may have a transformative impact on society. The radio propagation measurement systems offer vital knowledge for researchers in industry, academia and international standard bodies who will design future high-speed wireless networks for 6G, 7G and beyond. Students using this facility will gain knowledge at these new frequency bands. The THz Measurement Facility will host a robust website for the explanation of available equipment, tutorials for learning how to use the facility, and a repository of measurement results, metrology approaches, and recent research results. The website link is https://engineering.nyu.edu/THzLAB and will be maintained and updated regularly. Popular simulators, measurement studies, calibration results, student and collaborator activities, sponsor and vendor activities, equipment user notes, and K-12 outreach events will be placed on the website.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.