Figure 3(a) shows the fabricated antenna having dimensions obtained from
simulation. Return loss of the fabricated antenna is measured using
Keysight N9912A network analyzer. Retrun loss of better than 39 dB is
achieved for the operating frequency range of 400-407 MHz.
(a) (b)
Figure 3:(a) Fabricated
Quarter-wave antnnea and (b) measured S11 parameter
Designed monopole antenna provides maximum gain in the lower elevation
region. At higher elevation angles between 45° to 90° its gain varies
from 0 dBi to -30 dBi. This creates no coverage region or gap region
overhead the antenna. Therefore another antenna was designed to provide
the coverage in the overhead gap region of the fabricated quarter-wave
monopole antenna.
Qurter-wave monopole AntennaQuadrifilar Helix Antenna [10] is a good choice to provide the
coverage in gap region of designed quarter-wave monopole antenna.
Beam-width of greater than 100° was required in the vertical plane.
Optimizer functionality of 4NEC2 was used to achieve beam pattern and
reflection coefficient as shown in Figure 4. Final dimensions of the
antenna obtained from the 4NEC2 are tabulated in Table 3.