Applicants
Current Fellows
Sensors and Electron Devices Directorate Research Areas
Electromagnetics
Diffractive Elements for Millimeter Waves
Advisor: JN Mait
Key words: diffraction, algorithm, millimeter wave
Diffractive technology has been successfully applied to optical systems through the development of design algorithms and fabrication technology capable of defining features that range from 100 nm to 1 mm. As sensor technology attempts to bridge the terahertz gap (roughly 100 GHz to 10 THz), it should be possible to apply diffractive techniques to enhance system performance in this part of the spectrum as well. Applications might include enhanced imaging, spectroscopy, or antenna design.
However, millimeter wavelengths dictate fabrication techniques more similar to traditional machining than to photolithography. Methods for rapid prototyping may also be applicable for fabrication. Further, the ability to realize features that are on the order of a wavelength or less implies that design algorithms must rely on rigorous diffraction theory, as opposed to scalar-based diffraction theory.
The major goal of this research is to develop design methodologies suitable to the terahertz gap that include the effects of fabrication and rigorous electromagnetic theory, and to demonstrate the efficacy of this technology in imaging, spectroscopy, and radiation applications.
Electrically Scanned Antenna Array
Advisor: SJ Weiss
Key words: electrically scanned antenna array, rotman lens, true-time delay
The Army is interested in the development and analysis of electrically scanned antenna arrays in the millimeter region of the spectrum. Opportunities exist for research on low-profile antenna arrays, novel beamforming lens concepts (i.e., Rotman lens), and true-time delay phase shifters (i.e., ferroelectrics, MEMS).
We are investigating aperture-fed planar antenna arrays to transmit and receive energy. Many challenging issues need to be addressed. Polarization diversity is an essential requirement for the array(s) because they must be able to accommodate horizontal, vertical, and circular polarization. Each array element must exhibit wide bandwidth while minimizing mutual coupling.
A Rotman lens is used as a beamformer for azimuth scans. For the Rotman lens, we are addressing issues such as bandwidth, phase integrity, and minimizing loss. Ferroelectric delay lines are being considered for phase shifting in elevation.
It is critical to optimize a coupling method that will preserve the desired phase shift over a specified bandwidth. We are considering MEMS-based phase shifting concepts as well as a variety of other low-loss switching technologies. Interconnections between all of the components of the ESA are an important concern.
Our goal is to produce a low profile, low-cost, lightweight millimeter-wave antenna array that rapidly scans in azimuth and elevation. Much research is needed to resolve issues of each component of the antenna as well as the interconnections. We are interested in candidates that would work on either part of the system (e.g., the aperture design, the Rotman lens) or on the system as a whole.