Electro-Textile Ground Planes for Multipath and Interference Mitigation in
GNSS Antennas Covering 1.1 to 1.6 GHz
B. Rama Rao, E. N. Rosario
The MITRE Corporation
Bedford, Massachusetts
Biography:
B. Rama Rao is a Principal Engineer at The MITRE Corporation. He had received his
Ph.D. degree in Applied Physics from Harvard University. Prior to joining MITRE, he
held technical staff positions at the Sperry Research Center and M.I.T. Lincoln
Laboratory. He was also an Assistant Professor of Applied Physics at Harvard University
and a Research Associate at M.I.T. He holds 10 U.S. patents, three of which are on GPS
antennas.
Eddie N. Rosario is a member of the technical support staff in the Sensors and
Electromagnetics Systems department at The MITRE Corporation in Bedford,
Massachusetts. He helps in the design and in the measurement of antennas needed for a
wide variety of projects using The MITRE Corporation’s Near Field and Far-Field
Antenna Test Ranges.
Abstract:
This paper deals with the design of new types of ground planes made from low cost,
lightweight, and flexible electro-textiles that suppress both edge and curved surface
diffraction effects that can degrade the radiation pattern of GNSS antennas. Two of these
are very thin, resistivity tapered textile ground planes that are ultra wideband and able to
operate from 1.1 to 1.6 GHz. Their resistivity profile has been specifically designed to
suppress edge diffraction effects; their wide bandwidth makes them particularly suitable
for use with multiband GNSS antennas. This ground plane can be sandwiched between
plastic cover sheets for weather protection. The second type is a conformal ground plane
designed to suppress curved surface diffraction that affects GNSS antennas used in
avionics. It operates as a frequency selective surface with Electronic Band Gap (EBG)
characteristics and is able to attenuate antenna backlobes caused by curved surface
diffraction from the fuselage of an aircraft. It is designed to operate only over a specific
band of frequencies and is very effective when used in conjunction with a “Reduced
Surface Wave (RSW)” antenna consisting of an annular ring microstrip patch antenna
whose inner periphery is connected to the fuselage of the aircraft. The RSW antenna is
also made from electro-textiles. The performance this antenna when used with the EBG
ground plane has been validated through measurements on a large diameter metal
cylinder which simulates the fuselage of an aircraft. The results of these measurements,
performed in the GPS L
1
band, indicate that when used together they are able to suppress
almost all of the antenna backlobe radiation below the horizon. This is an enhancement
above the body masking capability of the aircraft fuselage and provides improved
