Analysis of Parasitic Patch for Axial Ratio Bandwidth Enhancement in Circularly-polarized-slotted Microstrip Antenna

Abstract

Analysis of the circularly-polarized slotted microstrip antenna in L-Band in 2–3 GHz is analyzed and discussed in this paper. The analyzed antenna is proposed for nanosatellite for electron density and scintillation measurement of ionosphere research. The requirements for nanosatellite antenna have physical specifications, such as lightweight, thin layer and small size with length and width smaller than or equal to 100 mm × 100 mm and electrical specification, such as the axial ratio (AR) lower than 3-dB, reflection coefficient ( $S_{11}$ ) lower than −10 dB. The proposed antenna is simulated based on computer simulation technology (CST) simulator with single proximity-coupled feeding, single patch. The proposed antenna consists of the ground with a circular and rectangular slotted patch on the upper side and the shifted feed line at the bottom side. Between the ground patch and the feeding line have a substrate which has a dielectric constant of 2.17, the dissipation factor of 0.0005 and dielectric thickness of 1.6 mm. The analysis is performed by varying the length ( $l$ ), width ( $w$ ) and form ( $F$ ) such as rectangular, circular and elliptical of the parasitic patch on upper side. The effect of that antenna parameters $l, w$ and $F$ to impedance bandwidth (IBW), the 3-dB axial ratio bandwidth (ARBW) will be analyzed and presented. The characteristic of the analyzed antenna has a good agreement between simulation and measurement result. The length, width and form of the parasitic patch has dominant effects to the 3-dB axial ratio bandwidth and position of the feed line has the dominant effect to the reflection coefficient. The simulated result shows that a parasitic with rectangular form can generate the 3-dB axial ratio bandwidth more than 1 GHz from 2.1–3.2 GHz.