Abstract:
Patch antennas are a type of low profile antennas those can yield a nice broadside radiation pattern with a moderate gain. In patch antenna fabrication process, substrate selection is also very important since gain is much affected by the proper choice of substrate. In this research, experimental investigation with the fabricated antennas at two widely used GSM bands (900 MHz and 1800 MHz) have been done. Later the experimental results have been verified by simulations. Although in literature there are numerous examples of fabricated patch antennas, the novelty of this research is the way antennas have been fabricated based on its mathematical modeling. At the beginning, a 900 MHz rectangular patch antenna loaded with plastic substrate was fabricated and tested in the laboratory. This antenna showed some deviations in radiation characteristics. So, another rectangular patch antenna at 1800 MHz frequency loaded with the same substrate was fabricated. The experimental results of this antenna showed good resonance and radiation behavior. However, both the antennas constructed with plastic substrates became bulky and heavy. That is why, in order to reduce the size and weight of the antenna, a high permittivity material (barium titanate) was used as the substrate for 1800 MHz rectangular patch antenna. Since barium titanate substrate is available in powdered form for industrial use, suitable shaped substrate was fabricated in laboratory for using it in patch antenna. The gain and radiation characteristics of this antenna were satisfactory despite of the fact that the gain decreased by a certain amount due to using high permittivity material as the antenna substrate. The antennas were later simulated in HFSS (High Frequency Structural Simulator) software to verify the experimental results by keeping all the dimensions same as fabricated antennas. The experimental and simulation results of all the antennas showed good conformity except for the 900 MHz plastic loaded rectangular patch antenna, the radiation pattern of which showed comparatively higher deviation. It was not possible to investigate several other important characteristics of the antenna, such as- s-parameter, polarization ratio etc. due to limitation of lab equipments. For this reason, some other analogous characteristics (e.g. received power level instead of s-parameter) have been used. After reviewing all the experimental and simulation results, it can be concluded that all the fabricated antennas show moderate resonance and radiation characteristics which is comparable to their ideal cases.
