Optimization of Return Loss Parameter of Feed Network of Turnstile Antenna in LEO Satellites Application

This paper , design of a turnstile antenna in UHF band (465 MHz) is carried out. optimum values for its main physical parameters such as monopole lengths, monopoles distance and angles are obtained by using HFSSV10 software. Antenna feed network is designed with microstrip lines to achieve in to the 90 degrees phase difference between adjacent monopoles and small size, simultaneously. Obtained scattering parameters from antenna design are used with microstrip feed network in Microwave Office software to achieve the desired VSWR characteristic of antenna at 465 MHz. In next step, the line and stub lengths are optimized in order to achieve a return loss better than 20 dB in operation frequency. Variable lumped capacitors are used in designed feed network for frequency fine tuning. The designed antenna and feed network are fabricated and tested. The diagrams represent a very good agreement between simulation and measurement.