Triangular Lattice Electromagnetic BandGap Antenna

A frequency domain video is now available at:
http://www.youtube.com/watch?v=R54hzIW7TRU

These antennas are realized arranging ceramic rods in a simple triangular or cylindrical lattice, realizing an approximation of an ideal two-dimensional structure made with infinite long rods. These two-dimensional structures may present a BandGap, a range of frequencies in which electromagnetic propagation is not allowed.

If we excite a TM mode in a cavity created by removing a dielectric rod from the lattice, energy at frequencies outside the band-gap will be free to propagate through the structure, while energy at frequencies within the bandgap will be trapped in the cavity. Trapped energy can be directed toward a specific direction by creating an angular defect in the structure.

A three-dimensional antenna is realized placing a feeding quarter-wavelength probe in the center of the EBG structure. For low elevation angles, the excited fields have a distribution very similar to the 2D configuration: the 3D structure is a good approximation of the 2D structure and, at frequency within the bandgap, a high attenuation is expected in the EBG structure direction. For increasing elevation angles, the 3D EBG structure approximation of the 2D structure progressively fails; however, given the intrinsic configuration of the excited fields (the electric field magnitude is decreasing as the elevation angle increases), low radiated fields are expected anyway. Gain is therefore expected in the same angular direction of the defect window whilst in the opposite direction, where the structure is intact, the radiation is attenuated.

Few prototypes have been built and tested, achieving 31% fractional bandwidth and average gain and FTBR of 11.5dBi and 27dB respectively.

Category:

Science & Technology

Tags:

• electromagnetic
• bandgap
• antenna
• EBG
• TEBG