Arizona State University
The Ohio State University
Last Reviewed: (not done)
Connection One is a National Science Foundation Industry/University Cooperative Research Center working closely with private industry and the federal government on various projects in RF and wireless communication systems, networks, remote sensing, and homeland security. The Center’s mission is to develop the technology to enable end-to-end communication systems for a variety of applications, ranging from cellular to environmental and defense applications.
Connection One is a National Science Foundation Industry/University Cooperative Research Center working closely with private industry and the federal government on various projects in RF and wireless communication systems, networks, remote sensing, and homeland security. The Center’s mission is to develop the technology to enable end-to-end communication systems for a variety of applications, ranging from cellular to environmental and defense applications. One aspect of the research is the development of integrated RF and wireless circuits-on-a-chip to simplify and enable a small, portable, all-in-one communication device. An additional research focus is the development of efficient architectures and routing techniques for networked applications. The industry/university partnership combines an academic environment with state-of-the-art research initiatives and real-world applications.
Autonomous Self-Healing Sensor Network Radio and Mixed-Signal Readout System
This project is aimed at determining performance parameters of analog circuitry in the sensor readout and communication chain for sensor networks and using this information to determine degradation patterns in the device parameters as well as predicting the remaining lifetime.
Compact THz Air-Biased-Coherent-Detection Spectrometer
The objective of this project is to realize a fully functional, compact THz Air-Biased-Coherent-Detection (THz-ABCD) spectrometer designed for cost-effective manufacturing and ready for commercialization. The proposed THz ABCD spectrometer will be capable of transmission-reflection geometry detection with real-time spectroscopic capability as a commercial product. Two important features of this prototype are: a. extremely broad bandwidth (over 30 THz) for linear spectroscopic applications; b. extremely high THz electric field (> 1 MV/cm) for nonlinear spectroscopy (a relatively unexplored field of research due to the limitation of available THz electric field from typical pulsed THz time-domain systems).
Design of Ultra wideband Dual Polarization LongSlot Array Antenna w/ Hybrid EBG/Ferrite Ground Plane
Hyoung-sun Youn, Yip Loon Lee, Nuri Celik, Magdy F. Iskander,
Hawaii Center for Advanced communications (HCAC)-University of Hawaii
Detection and classification of buried explosive threatens usually require a wideband antenna operating a low frequency regime (< 150 MHz) for the sufficient temporal resolution and better penetration depth. In addition, in order to extract some useful features such as polarization and resonance feature of explosives, the antenna should be able to measure dual polarization scattering over the wideband width. To address this issue, we propose to develop an innovative dual polarization design of the long slot antenna array system. To provide a co-phase dual-pol aperture, we considered a planar array with connected dipoles based on Wheeler’s continuous current sheet model for wide band applications. This antenna design is achieved by sectioning the metal strips and using the resulting gaps as feed ports for the connected dipoles horizontally polarized radiation pattern. The metal strips are still capacitively connected and long slot radiation patterns with vertical polarization can still be achieved.
This long slot is intrinsically wideband because the slot elements support TEM modes with very low cutoff frequencies and provides extremely wide bandwidth when there is no ground plane in back. However, the long slot aperture radiate in both forward and backward direction. To achieve a unidirectional radiation pattern, a ground plane is required. To higher operating efficiency while maintaining the ultra wideband feature of this antenna, our group developed a hybrid EBG/Ferrite ground plane that provide over 40:1 bandwidth and with a lower band starting at 120 MHz. By integrating the dual polarization long slot antenna array with the hybrid ground plane, we were able to obtain a unidirectional pattern while maintaining the UWB characteristic. The antenna performances were characterized by HFSS and simulated antenna characteristics will be presented.
Highly Nonlinear MM-wave Sensors for Passive Threat Detection
This project will develop passive millimeter-wave (PMMW) detection sensor elements using Si/SiGe technology for direct insertion into passive millimeter-wave camera systems. The development of a new Si/SiGe backwards diode (BD) recently reported by this group (IEEE EDL, 2005 and U.S. patent filed) with ultra-high curvature at zero-bias provides new opportunities for Homeland Security.
This project will investigate and exploit the unique properties of silicon-silicon germanium (Si/SiGe) zero-bias, backward diodes for integration and application in 94 GigaHertz (W-Band) passive, room temperature millimeter wave sensing. By having Si-based detector diodes that operate at W-band, the possibility exists for array architectures that are compatible with wafer scale manufacturing processes such as BiCMOS. Furthermore, the operating frequncy of 94 GHz offers and atmospheric window where millimeter waves permit an observer to see through inclement weather conditions (e.g., rain, fog, smoke) as well as clothing. This feature can offer a high contrast ratio between metallic objects and flesh, which is likened to an X-ray process.
The proposed project will develop a Si-based backward diode that processes the nonlinearity properties of its current compound semiconductor (e.g., InAs, GaSb), and yet be compatible in both structure and epitaxial processes like those employed in CMOS or BiCMOS manufacturing
Hybrid Metallo-Ferrite Ground Plane for Ultrawideband Antennas
The objective of this project is to develop a wideband ground plane for a long slot aperture to support greater than 20:1 operation (.2 to 2GHz) while maintaining a low effective dielectric index for ease of feeding. Our approach is to introduce a reflective surface composed of a high impedance surface (non-conductive ferrite) in the outer region tapering to an electrically conductive surface at the center of the slot. The ferrite material in the outer region aims to emulate the free-space antenna gain at low frequencies whereas the conductive center region serves to increase gain at the higher frequencies.
Microwave Stethoscope: A Novel Microwave Method for an Integrated Measurement of
The objective of this project is to develop a novel low-cost and integrated microwave “microwave stethoscope” system that can continuously monitor human vital signs with minimal discomfort to the patient. The vital signs to be measured include the heart rate, breathing rate, stroke volume, and changes in lung water content. Specifically, the proposed novel microwave method for non-invasive continuous monitoring of vital signs is based on the earlier trans-thoracic transmission coefficient measurement technique using the microwave sensor developed and patented by the Hawaii Center for Advanced Communications. The trans-thoracic transmission coefficient measurement technique was initially used for monitoring changes in lung water content but recently extended to simultaneously monitor four vital signs from a single measurement. In this project, we are proposing to use the much less sensitive reflection coefficient measurements for vital signs extraction, as opposed to the trans-thoracic transmission coefficient measurements, hence, realizing the vision of “microwave stethoscope”. To overcome the reduced sensitivity of the reflection coefficient measurements to the vital signs, we propose optimized and broadband microwave applicator designs, advanced DSP algorithms that can work with very small signal to noise ratios, and integrated low-power low-cost receiver circuitry to replace the cumbersome network analyzer. For benchmarking the accuracy of the microwave stethoscope in monitoring multiple vital signs, computer controlled manikin experiments as well as human subject testing with FDA approved medical devices are proposed with close collaboration with the University of Hawaii Medical School. The development of the microwave stethoscope technology will have applications in providing cost effective healthcare remedying the worldwide healthcare problems, monitoring of school students, and in variety of field and emergency military applications.
Modeling of High Voltage GaN-based Switching Circuits
The project is to design a new device models and optimization guidelines for power GaN-based HEMTs. It implies analytical and numerical modeling of a current collapse, optimization of the device layout and structure, design and optimization of field termination plates, allowing for better device performance. Thermal properties of the GaN HEMT will be studied analytically and employing numerical simulation of the heat transfer in the device, substrate and the heat sink. New compact circuit models for power GaN-based HEMTs taking into account the current collapse, thermal and self heating effects, and trap-assisted gate leakage will be developed. New testing technique for power GaN-based HEMTs will be acquired, enabling power FET development for communication systems. Attention will be paid to the 1/f noise studies, focusing on the correlation between noise and device degradation.
Nanoparticle-based Analytical Biosensor
Low-dimensional, metal-oxide semiconductor nanomaterials have stimulated great interest and extensive research due to their novel electronic and optical properties in addition to their biocompatibility. They are compelling as a platform for interfacing biorecognition elements, with transducers for signal amplification. This project investigates the immobilization of aptamers onto various materials for the capture of specific targets. The targets will fluorescence at wavelengths that can be selectively detected by a nanoparticle-based detector. Metal oxides are being investigated for their bandgap properties that correspond to the detection of intrinsic fluorescence from potential biohazards. Previous work focused on zinc oxide (ZnO) nanoparticles on various substrates for the selective detection of tryptophan fluorescence. This work focused on indium oxide (In2O3) for its selective detection of NADH fluorescence. Both material and device properties will be presented as well as the methods of surface immobilization and results.
PL Studies of Deep-UV LEDs
Deep UV LEDs have highly promising applications to fluorescence detection, sterilization and disinfection and communication. Nitride based deep UV LEDs face problems like low efficiency, ageing under high current stress and efficiency droop at high injection currents. In addition to Photoluminescence (PL) and Electroluminescence (EL), these characteristics of LEDs are studied by sophisticated techniques such as Time Resolved Photoluminescence (TRPL), Scanning Near Field Optical Microscopy (SNOM), confocal microscopy etc.
Efficiency droop is a well known feature in case of InGaN LEDs. Many possible reasons including carrier delocalization, carrier leakage and tunneling outside the quantum wells, Auger recombination etc . Auger recombination is ascribed as one of the possible causes of the droop in InGaN systems. However, the energy difference between the first and second conduction band at Γ point of AlGaN is off resonance with the band gap which rules out the contribution of Auger recombination to efficiency droop in case of AlGaN deep UV LEDs. PL experiments were performed to study the role of carrier temperature and localization of carriers on the efficiency droop in AlGaN/AlGaN multiple quantum wells (MQWs) which form the active region of deep UV LEDs. The intensities of excitation used in the experiments averted a substantial contribution of QW saturation and overflow effects. It was found that carrier heating is the major cause of PL efficiency droop at lower temperatures in these AlGaN structures . However, at higher temperatures, the PL results obtained from structures having different well widths showed that filling in of the localized states which in turn increases the possibility of carriers reaching the non radiative centers becomes the dominating mechanism and causes PL efficiency droop . The localization has been found to be stronger in narrow quantum wells which results in lower droop in efficiency at high temperatures. TRPL experiments performed on AlGaN epilayers with different Al content confirmed that the efficiency droop is related to an increase in the possibility of carriers to reach non radiative recombination sites under high excitation . The PL efficiency was shown to reduce by ~3 times as the Al content was increased from 17% to 50%. This can be attributed to higher concentration of non radiative centers in samples with higher Al content. Samples with higher Al content also showed onset of droop at lower excitation intensities indicating a higher concentration of localized states.
Ageing and reliability of deep UV LEDs constitute another important concern. Studies on ageing of AlGaN QW based LEDs were performed using PL, TRPL, EL and SNOM techniques. LEDs emitting at 270 nm and 335 nm by SET Inc. were used for the experiments. Using SNOM and EL, it was found that the spectrum of the 335 nm device (low Al content) did not change much under current stress. It was thus concluded that the alloy does not show structural changes on being stressed . The shifts in the peak wavelength observed at high currents were attributed to change in the local alloy temperature and hence the band gap. For the 270 nm device (high Al content), the EL spectrum showed a permanent shift upon ageing with the peak wavelength showing a red shift. This was ascribed to N vacancy related transitions in p-type cladding layer . Aged 270 nm LED also showed non uniform illumination across the surface. This effect of ageing is attributed to local variations in defect concentrations.
Publications based on the work:
 G. Tamulaitis et. al., “Carrier dynamics and efficiency droop in AlGaN epilayers
with different Al content”, Phys. Status Solidi C, pp.1–3, 2011
 G. Tamulaitis et. al., “Carrier dynamics and efficiency droop in AlGaN epilayers
with different Al content”, manuscript under preparation
 A. Pinos et. al., “Optical studies of degradation of AlGaN quantum well based deep ultraviolet light emitting diodes”, J. Appl. Phys., vol. 108, no. 093113, 2010
Radiation hardening by design of digital circuits
Use of commercial digital integrated circuits in space is problematic because they experience transient hang-ups that require an extensive restart sequence and can result in the loss of critical data. If part of a critical system, such errors could lead to missions being lost when required actions not being performed (e.g. firing a thruster) or being performed at the wrong time (e.g. opening a parachute). Digital systems can be hardened to transient upset by triple modular redundancy (TMR), where all logic is triplicated and the output is voted. An alternative approach is to add temporal redundancy, for example, by using flip flops with multiple internal delay paths having different delay that are subsequently voted. This project will evaluate the trade-offs between these two approaches and attempt to partially automate the processes needed to harden a design starting from the RTL level. A simple digital system, such as an 8051 microcontroller will be used as the primary test case.
Radio Frequency (RF) Characterization of Composites and
New material systems are new packaging solutions for high performance telecommunications circuits. This research entails high-frequency characterization of new materials and circuits comprised of flexible polymer and carbon nanotube (CNT) technologies. These materials offer unprecedented capabilities in terms of dielectric constant design and flexibility necessary for conformal installations. Particular interest is on high frequencies where conventional multi-layer technologies are not suitable. As low cost and reliable printing is introduced, polymer substrates will be rapidly entering the electronics market, making their characterization necessary for performance simulations and integration into RF front ends. The proposed research is a result of the complementary activities at two I/UCRC Connection One Universities: The University of Arizona (UA) and Ohio State University (OSU). The work focuses on electrical properties for a new class of polymer-based materials.
Before CNT and other new materials technologies can be introduced into new products, accurate information on their electrical properties is needed. The project involves the development of processes to yield frequency dependent mathematical models for material permittivity of the ceramic powders via transmission line structures fabricated on such materials. New, frequency-dependent permittivity models for porting into high frequency simulation tools will be developed.
Scaling of Inductors through Integration of Improved Magnetic Materials
The objective of this proposed research is to scale the size of inductors down to 50 μm while satisfying all important performance requirements, including greater than 1 nH inductance over 1 GHz with double-digit quality factor, thus reaching high inductance density of more than 400 nH/mm2. Inductor scaling will be achieved by introducing magnetic materials with the optimized patterning and geometry to significantly improve ferromagnetic resonance frequency, to reduce eddy current losses, to reduce skin effect as well as maintain the high permeability for thicker magnetic films.
Tunable Strain Sensor with Nanoscale Resolution Based on Buckled Thin Films
This project seeks to explore the application of a newly developed buckled thin-film grating for high sensitivity strain sensing of microelectronic packages and extending to backend films in semiconductor wafers. The buckled thin-film grating will be attached to the packages under-study, which makes the grating periods change as the local strain changes. Such changes will be recorded with optical system, while the scanning across the sample surface will allow the 2D spatial mapping of the strain change.
Unconditionally Stable, Digitally Controlled LDOs for SOC Applications
In this project, an all-digital implementation of a robust sliding-mode controller will be implemented with low analog complexity, and high accuracy for low-power digital power generation systems. Sliding Mode Controller (SMC) is a form of Variable Structure System (VSS), suitable for systems that perform mostly—if not all—in discontinuous or large-signal-mode of operations. The basic principle of SMC is to employ a certain sliding surface as a reference path such that the controlled state variable’s trajectory can be directed toward the desired equilibrium. SMCs like many other feedback control systems could be realized in both analog and digital (or discrete-time) formats.