19/7/16

Alexander Treyvas

M.Sc. student of

Professor Rafael Kastner

Physical Electronics Department, Tel Aviv University

Interference with neighboring antennas is a common problem in many communication systems. Civilian and military communication sites, command and control platforms etc. all have a large number of antennas situated in close proximity to one another. When these antennas operate in overlapping or close frequency ranges, they all might suffer from mutual interference.

Outdoor or military antenna clusters require simple, cheap and robust solutions for the mutual coupling problem. The structures in question include whip/log periodic and other wire antenna types with lengths of up to few meters. In these cases, most isolation techniques, used, e.g., in printed antenna design, such as high impedance surfaces, resonant slots and absorbing materials, are hard to implement.

One way of solving the problem is by using active cancellation systems, ones that sample the transmitted signal and transmit its opposite in order to cause out-of-phase interference. This method is effective, but requires additional equipment, which, in turn, requires additional power supply, space and extra maintenance.

By implementing the out-of-phase interference method, which includes coupling to the transmitting antenna, we have managed to achieve a significant improvement of isolation between neighboring antennas (S₂₁) over reasonable bandwidth while having tolerable effect on the antennas gain.

Another method described in this work is adaptation of a monopole ground plane to an Archimedean spiral shaped strips. These strips have a curved shape that allows a longer path for the current flowing on their surface. In this way, the field radiated by the ground plane is expected to change, and have an impact on the antenna radiation pattern and its coupling to neighboring antennas.

The results show that the new ground plane structure can reduce the near fields of a monopole antenna, having a ground plane radius of 0.5 wavelength, by ~3[dB], thus reducing the transmitted energy by ~6[dB].

Tuesday, July 19, 2016, at 13:00

Room 011, Kitot Building