Development of multiband microstrip antennas for GPS applications

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2019
Önder, Mustafa Caner
In this thesis study, the design, fabrication and measurements of dualband and triband circularly polarized microstrip antennas for GPS applications are presented. Characteristic mode analysis technique is applied to get an insight into circularly polarized patch antennas. A design flow is presented for a circularly polarized L1 GPS band microstrip antenna by using characteristic mode analysis. A single fed L1/L2 GPS band right hand circularly polarized four-slotted patch antenna is designed by using reactive loading technique. A novel zigzag four-slotted patch is designed to operate at L1/L2 GPS bands without the need of reactive loading and designed antenna is fabricated. The frequency ratio of 1.31 is achieved with zigzag four-slotted patch. The axial ratios 7.5 dB and 8.1 dB are measured at lower and higher operating bands, respectively. An L1/L2/L5 GPS band single fed right hand circularly polarized two-layer stacked antenna is designed and fabricated. In measurements, it is seen that the impedance bandwidths of 58 MHz, 28 MHz and 11 MHz are achieved at operating frequencies. The axial ratios of 0.7 dB, 8 dB and 7.5 dB are measured at operating frequencies. An L1/L2/L5 GPS band single fed right hand circularly polarized three-layer stacked antenna is designed and fabricated. In measurements, the impedance bandwidths of 71.1 MHz, 4 MHz and 32 MHz are achieved at the center frequencies of L5, L2 and L1 GPS bands, respectively. The axial ratios of 0.7 dB and 3-dB axial ratio bandwidth of 5 MHz are measured at L1 GPS band. The lowest axial ratios of 1.5 dB and 8.9 dB are measured at the lowest and the middle operating frequencies, respectively.