G. P. Pochanin, N. M. Kaluzhny, V. Ye. Belousov, S. A. Masalov, I. Ye. Pochanina
The research purpose is verification of has been developed by authors approach to designing of ultrawideband (UWB) antenna which is intended both for a radiation and reception of UWB impulses of electromagnetic field and for a radiation and reception of narrow-band signals in the wide frequency range and determination of attainable antennas characteristics.
The phenomenological model of radiator of UWB impulse signals is considered in the paper. The model takes into account factors which influence on antenna efficiency and also reasons and degree of signal shape distortion at radiation. The analysis of processes, what occur at excitation of radiator by the short UWB pulse signal, has allowed to draw conclusion that a radiator in form exponential tapered slot is optimum for achievement of effective radiation in the ultra wide frequency band. In this case the antenna overall dimensions are the least as compared to the overall dimensions of antennas of other forms and the same radiation efficiency.
The original algorithm for initial estimation of shape and dimensions of the exponentially tapered slot antenna is suggested.
It was shown that there is a possibility to match the radiator with feeder and free space by means of cutting a hole of certain size in a sheet of antenna. The matching quality depends on perimeter of the hole. Experimentally obtained dependence of the antenna efficiency on the matching hole perimeter allowed to find out the optimal perimeter which is equal to length of edge of conductor shaping the tapered slot. At this hole perimeter to edge length ratio the radiation efficiency is maximal.
Pick amplitude antenna patterns of radiator which has been investigated in experiments show that even if radiator dimensions (slot edge length equals 40 cm) are comparable with the spatial duration of the exciting pulse (duration equals 1 second is corresponding to spatial length which is equal 30 cm) the antenna has evident directional properties.
On the basis of obtained results the exponential tapered slot radiator with matching hole has been suggested. Using the finite difference time domain method the radiated electromagnetic fields and the frequency domain antenna patterns in frequency band from 2 GHz to 18 GHz have been calculated. Given in the paper computer simulation results of the exponential tapered slot radiator show a possibility to create antenna systems with acceptable gain flatness (less than 20%) and beamwidth variation which is less than 30% in ultra wide frequency band (about 4 – 6 octaves)