1. Analysis, Modeling and Design Optimization of Electronic Packaging Interconnects and Microwave/Millimeter Wave Circuit Structures (Principal Investigator)
The objectives of this program are to formulate accurate and efficient methods to model both the time-domain and frequency-domain characteristics of multi-level, multi-conductor, transmission lines and circuits. These interconnect lines and structures are used in microwave, millimeter wave, and high-speed high-density integrated circuits that include geometrical and material complexities. The frequency-domain analysis is based on a general spectral domain formulation that includes the effects of multiple, lossy dielectric layers and adjacent transmission lines that may be located either at the same or different levels. Time-domain characterization uses the inverse Fourier transform to compute the transient parameters of the lines whose frequency-domain characteristics are computed with the Spectral Domain Method (SDM).
In addition, the Finite Element (FEM), SDM, and hybrids of these two methods, are used for the frequency analysis. Adaptive mesh refinement procedures are used to investigate critical points of complex packaging structures, such as fracture points and sharp discontinuities. Visualization techniques are employed to examine field intensities and distributions in critical parts of the package. The analysis, modeling and optimization are extended to include entire package structures, especially those encountered in the emerging technology of Flip-Chip packaging.
2. Advanced Helicopter Electromagnetics (AHE): Industrial/Government Associates Program (Principal Investigator)
The AHE Program is a unique program initiated at Arizona State University (ASU) on January 1, 1990, as a three-way partnership between industry-government-university. The program develops analytical methods, computational techniques, and computer codes for advanced helicopter applications. In addition, the AHE Program uses the ElectroMagnetic Anechoic Chamber (EMAC) at ASU for testing and analysis verification.
The research initiatives under the program are directed toward the analysis and modeling of antennas, scattering and penetration characteristics, and development of antenna technology related to helicopter airframes and other complex structures, and to integrate new and existing antenna elements with complex airframes, using numerical techniques, to gain insight into their effective placement. The goals are to support electromagnetic research on topics of mutual interest to the AHE membership and helicopter community, especially that of "dual-use" technology, develop standard practices for evaluation and comparison of metallic and nonmetallic airframes, facilitate the exchange of information and results on recent advances in helicopter electromagnetics, and collect and disseminate information on state-of-the-art helicopter scale model testing and evaluation.
Boeing Helicopter Systems
United Technologies-Sikorsky Aircraft Division
IBM Federal Systems Division
NASA Langley Research Center (LaRC)
U. S. Army: Communication Electronics and Command (CECOM)
U. S. Army: Army Research Office (ARO)
U. S. Army: Aviation Applied Technology Directorate (AATD)
U. S. Army: Electronic Proving Ground (USAPEG)
U. S. Navy: Naval Air Warfare Center-Aircraft Division (NAWC-AD)
The purpose of this research project is to develop low-frequency and high-frequency methods to analyze various radiating elements located on complex structures with combinations of conducting, nonconducting, and energy absorbing surfaces and interfaces. Many current methods are limited in the geometrical shape and surface conductivity that can be modeled; in many cases the surface is modeled as perfectly electric conducting. While this may be sufficient for many configurations, it is not adequate for future airframe designs which incorporate advanced composite materials.
The research focuses on fundamental concepts, techniques, and algorithms which will remove some of the present limitations in predicting the radiation characteristics of antennas on complex aerospace vehicles.
4. Penetration of High Intensity Radiated Fields (HIRF) into General Aviation Aircraft (Principal Investigator with Craig R. Birtcher)
Modern military and civilian aircraft use digital control systems to perform critical functions. Such control units installed on aircraft are vulnerable to external phenomena such as high intensity electromagnetic fields. Electromagnetic interference from external sources can cause an upset of the digital system's control unit and major damage to the aircraft. New aircraft designs must be tested, before being certified, against electromagnetic penetration. If a problem is identified, the aircraft must be redesigned to effectively reduce the intensity level of the penetrating fields.
The objectives of this study include the development of cost-effective techniques and tools to assess and certify the survivability of aircraft to sources of electromagnetic interference (EMI), both external sources[i.e., High Intensity Radiated Fields (HIRF)] and internal.
|The interactions of the HIRF fields with the aircraft can be visualized as color-coded contours, as in this figure. The warmer colors indicate higher field intensities, while cooler colors represent lower field intensities.|
|This cross section of the FDTD mesh shows the locations of the field probes in the cockpit, first class cabin, and the electronics bay. These are some of the points at which NASA LaRC made in-flight measurements for comparison with the simulations. The different colors indicate various materials, the properties of which are readily handled using the FDTD method.|
5. Smart Antennas for Future Reconfigurable Wireless Communication Networks
(Principal Investigator with 6 other Co-PIs)
The antenna is one of the fundamental distinctions between a wired and a wireless system. The design of the antenna impacts the development of each component-from the circuit design to the receiver structure and coding technique, as well as the channel access protocol - employed in future wireless communicaion networks. The most challenging environment for the design of each component is where the communication devices are extremeely small, low power computing and consuming mobile terminals. Furthermore, these terminals may be able to move randomly and organze themselves in an ad hoc communication structure. Such a network of communication terminals is referred to as a Mobile Ad Hoc NETwork (MANET). In this project, it is proposed to investigate the used of smart (adaptive) antennas to imporve channel quality in a MANET. The design of a smart antenna for a MANET will pose many challenges in antenna, feed network, signal processing, communication and protocol designs.
6. Electromagnetic and Radio Channel Modeling of Rotor Modulation on Helicopter SATCOM Systems (with Dr. Darryl Morrell)
Digital communications with a helicopter is often impaired by the fact that the antenna is often located near the main or tail rotor. As the rotor passes near the antenna, it causes electromagnetic scattering resulting in a periodic distortion of the received communications wave form. This is referred to as rotor modulation.
This project is divided into two parts: the electromagnetic modeling and the radio channel modeling of rotor modulation. In the electromagnetic modeling, the entire helicopter airframe, including the dynamic movement of the rotors, are modeled using the Finite-Difference Time-Domain (FDTD) method to calculate the rotor modulated signal of antennas mounted on such a structure. This rotor-modulated signal is then used to model the radio channel performance of digital communication systems. Different communication system and receiver architectures are investigated.
This represents the predicted modulated, due to the rotor blade motion, roll-plane radiation pattern (in dB) of a helicopter-mounted crossed dipole antenna, which was predicted using the Finite-Difference Time-Domain (FDTD) method. The level of modulation, at a particular orientation about the helicopter, is defined as the difference between the maximum and minimum levels of the radiation that occurred as a function of rotor orientation.