Antennas and Propagation

1. Antennas and Propagation

2. Multi-Purpose Antenna • Faculty: W. Davis • Sponsor: Astron Wireless Technologies • Description: Develop multiband antenna: Condense (VHF/UHF) line-of-sight, UHF satellite communication, L-band and global positioning system (GPS) functions into a single airborne aperture that can be used on a Navy aircraft like the E-2C.

3. Ultra-Wideband AntennaFor Electronic Attack Aircraft • Faculty: W. Davis • Sponsor: Astron Wireless Technologies • Description: UWB jamming antennas/arrays to conform to radome (18”-26”-180”). Four bands: 50-550 MHz, 100-1000 MHz, 500-2500 MHz, and 2-18 GHz. UWB antenna designs within physical limits of radome. Short Vivaldi Antenna Directivity, 960 MHz.

4. Shorted Inner Radius Radiating Annulus Capacitive Load Ring Capacitive Loading for Size Reduction in Shorted Annular Ring Antenna Elements • Faculty: A. Zaghloul Dissertation in preparation by: W. Mark Dorsey (NRL) • Description: The shorted annular ring antenna’s (SAR) two radii satisfy the dominant mode resonance condition of a standard circular patch and also keep from exciting a surface wave mode in the substrate. A higher frequency antenna can be placed within the inner radius of the shorted annular ring antenna to provide dual-band operation. Edge loading techniques are used to reduce the outer radius of a SAR element without altering the inner radius by increasing the capacitance of the resonant structure. Reference:A.I. Zaghloul, C.B. Ravipati and M.T. Kawser, “Modeling and Analysis of a Dual-Band Dual-Polarization Radiator Using FEKO,” 21st ACES Conference, March 2006.

5. Advanced Antennas • Faculty: W. Davis, C. Dietrich • Sponsor: ONR(Advanced Wireless Integrated Navy Network) • Description: • Compact antennas for handheld and mobile terminals • Antenna Characterization – transient & wideband • UWB antenna design (support of AWINN demonstrations) • Antennas providing polarization, spatial, and pattern diversity – Evaluation of antennas in a MIMO environment • Wideband balanced antenna/array feed networks

6. d D Hybrid Reflector-Array Antenna Concept • Faculty: A. Zaghloul in collaboration with: B. Pontano, Comsat Labs Division of ViaSat • Description: This work describes a concept for a hybrid antenna that combines the conventional reflector with an array of printed circuit elements that uses the reflector surface as the array aperture. Objective is to increase the functionality of the antenna by reusing the conical surface of the reflector as a direct radiating array. Studies of the performance of an array printed on a paraboloidal surface showed high aperture efficiencies. Reference: A.I. Zaghloul and B.A. Pontano, “Hybrid Reflector-Array Antenna Concept,” IEEE International Symposium on Antennas and Propagation, July 2006. S. Kumar, “Investigation of a Phased Array of Circular Microstrip Patch Elements Conformal to a Paraboloidal Surface,” MS Thesis, Virginia Tech, September 2006.

7. Cell Phone HAC • Faculty: W. Davis • Sponsor:Sony-Ericsson Mobile Communication • Description: Cell phone radiation mechanisms – NEAR FIELD: slope discontinuity of current and low-Q antennas => DECREASE near fields  Hearing Aid Compatibility(HAC)

8. Distributed Beam Former for Conformal or Distributed-Aperture Phased Arrays • Faculty: A. Zaghloul in collaboration with: O. Kilic, The Catholic University of America • Description: The objective is to develop a low-cost, low-loss and light weight beam former for distributed aperture antenna that can be shaped to conform to certain structures. The array is divided in modular subarrays, and its beam former is distributed in two stages: a first RF stage at the subarray level with pre-set scanning positions and a second digital stage that operates on the combined outputs of the subarrays. The two-stage beam former presents a significant reduction in the number of required components. Reference: A.I. Zaghloul and O. Kilic, “Distributed Beam Former for Distributed-Aperture Electronically Steered Antennas,” 25th Army Science Conference, November 2006.

9. Faculty: C.B. Dietrich, S.W. Ellingson, W.A. Davis, J.H. Reed, A.I. Zaghloul Funding: Pending Description: Signals from multiple elements can be multiplexed using a variety of techniques to reduce cabling requirements in satellites or other small vehicles (upper figure). Remote array processing (lower figure) carries this a step further. Miniaturized Array Processing

10. Measurements • Faculty: W. Davis • Sponsors: • Applied EM • NanaSonic • FRC • Description: Antenna measurements of near and far fields, pattern, impedance, transient response.

11. TR TR Air Sand Clay Granite R R R R R R Development of GPR Models to Detect and Discriminate Landmines • Faculty: A. Zaghloul, L. Mili, G. Brown in collaboration with J.S. Goldstein, SAIC Dissertation in preparation by: N. Schwartz • Description: The objective is to develop a landmine detection technique or algorithm that isolates landmines, particularly plastic anti-personnel mines, from clutter-causing objects. This includes: • Statistical modeling of different Ground Penetrating Radar (GPR) systems’ performance • Sensitivity of the sensor and detection technique against simulated or inert landmines • Space-Time Adaptive Processing (STAP) as applied to GPR • Design of robust processors which improve processor performance in terms of convergence, SINR, computational and numerical complexity Test Bed Layout

12. LMSS System Design • Faculty: W. Davis, R.M. Buehrer, A. Zaghloul • Sponsor: Unspecified • Description: • Antenna Trade Study • Propagation Issues • Modulation Requirements • Signal Processing to Enhance Throughput

13. Systems Potentially Affected by Spurious Emissions Reader Active RFID EMC on Aircraft • Faculty: S. Ellingson • Funding: AVSI • Description: • Characterize tag emissions & behaviors, apply models for aircraft interior propagation; and assess risk. • Bench-top characterization of emissions from tags of many vendors. • Construct models for interference path loss (IPL) from existing data, physical models, and new in situ measurements.