Design Of Dual Band Circularly Polarized Patch Antenna For Civilian GPS Applications

In recent years, there has been an increase in demand for Global Positioning System (GPS) technology particularly for civilian applications such as marine navigation and satellite communication. The modernization of GPS signals implies new requirements for GPS receivers. Since antenna is an important part of GPS receivers, there is a great need for the design and production of new antennas which are fully compatible with modernized signals.Because of their advantages such as low cost, compact size, low profile, ability to support dual-frequency and circular polarization operation, microstrip patch antennas have become widely used in GPS antenna designs.Two circular polarization patch antennas are proposed in this thesis. The first antenna is a stacked square patches antenna designed to operate at L1(1575.42MHz) and L5(1176.45MHz) frequency bands and the second is a new compact slot patch antenna intended for L1frequency operation. Initially, a corner-truncated patch antenna for GPS L1operation was designed to validate simulation in Ansoft High Frequency Structure Simulator (HFSS). The simulation results obtained for this antenna were used to design the two proposed antennas.The dual-frequency antenna, GPS L1L5patch antenna uses two square patches and two probe-feeds to generate RHCP radiation. The feeds were connected in orthogonal axes to generate modes with equal amplitude but in phase quadrature necessary for CP operation. The new compact slot patch antenna uses corner-truncated square patch and single probe feed to generate right hand circular polarization (RHCP) radiation. In this design four slits and one slot were utilised to reduce the overall size of the antenna. After the simulation, the antenna was fabricated and measured using Anritsu MS2026vector network analyser.The simulation results obtained for all designed antennas are presented. In addition, the simulation and measurement results for a proposed new compact slot antenna were compared. The results obtained for all antennas meet the performance specifications for civilian GPS applications.