Rectangular patch antenna: Design, wideband properties and loss tangent influence

This study gives experimental results for a rectangular microstrip patch antenna, regarding its parameters and their dependence on the substrate loss tangent. Antenna was modeled to exhibit circular polarization at two frequencies of interest: 826 MHz (a frequency in the digital dividend spectrum, mainly reserved in Europe for LTE networks) and 900 MHz (a frequency in the GSM uplink band). Experimental model was realized based on the simulation results obtained from FEKO and SEMCAD X numerical tools. Significant impact of substrate loss tangent on antenna impedance and gain was noticed. The results clearly showed direct dependence of the antenna radiation characteristics on substrate loss in such a way that low-loss materials should be used in order to achieve patch antenna with sufficient gain. Furthermore, special attention needs to be devoted to impedance matching with respect to substrate losses. On the other hand, substrate loss tangent variations did not cause any noticeable polarization change. The used design resulted in a wideband total gain, but the circular polarization was produced only at the lower and upper frequency limits.