Compact dual-band circularly polarized microstrip antennas for RFID applications

• Main Author: Tanawie, Randy Oktavinus.
• Other Authors: Arokiaswami Alphones
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Antennas, wave guides, microwaves, radar, radio
• Online Access: http://hdl.handle.net/10356/40781
• Institution: Nanyang Technological University

The main objective of the project is to propose and fabricate compact single-feed dual-band circularly polarized (CP) microstrip antennas for radio frequency identification (RFID) reader applications. In this first part of the project, single-band CP microstrip antennas with single-feed were studied, designed and measured. The new square-shaped slotted ground-plane CP microstrip antennas are proposed for ultra-high frequency (UHF) RFID handheld reader applications. The four square-shaped slots are embedded along the each diagonal directions of a square ground-plane to generate a CP radiation. The locations of the slots are same along the diagonal directions from the ground-plane centre. Slightly changing the square-slot area one of a diagonal axes compare to other diagonal axis, CP can be obtained. The square-patch is used as a radiator. The performance of the conventional single-feed truncated corner CP microstrip antenna is also studied for comparison with the proposed compact CP antenna designs. The measured 10-dB return loss and 3-dB axial-ratio (AR) bandwidths are 31.0 MHz and 12.0 MHz respectively. The gain over the 3-dB AR bandwidth is more than 1.5 dBic. For the second part of the project, compact single-feed dual-band CP microstrip antennas are discussed. Dual-band CP antennas with operating frequency 850 – 870 MHz and 950 – 970 MHz were achieved by implementing a stacked (multi-layered) antenna and a square ring (single-layered) antenna. The stacked-antenna’s design is adopted from the first part design as its lower band and stacked with truncated corner patch to obtain the upper-band frequency. Different thickness was implemented on the stacked antenna. The truncated-corner-patch (higher band) had thicker substrate thickness as compare to the lower band patch. Moreover, the square-rings antenna designed and proposed for further study.