Inkjet Printed Flexible Patch Antennas for Full Duplex and Circular Polarization Applications

Abdul Rakib Hossain

doi:10.7273/000005012

Flexible devices are getting more popular nowadays because of it’s lightweight, small size, portability, less expensive, environment friendly, and disposability. Flexible antenna, part of flexible devices, has become an important component of research for electrical engineers. The flexible antenna can be built using different materials like PET, PEN, liquid crystal polymer, PDMS, and textiles like woolen felt, cotton, cordura, and fleece as substrate. This thesis focuses on designing and fabricating antennas on PET paper by using inkjet printing for full duplex and circular polarization applications. Firstly, a flexible full-duplex antenna is proposed with robust performance and high isolation for 5.8 GHz using foam and PET paper. The patch of the antenna is modified by corner cut and inset feeding, while the defected ground structure is used to improve isolation between transmit and receive ports. Silver nanoparticle ink is used for printing the antenna in an inkjet printer. The fabricated version supports simulated results by showing acceptable performance in desired bandwidth. Bending tests and human body loading experiments are carried out on the fabricated antenna to demonstrate the antenna’s effectiveness for wearable applications. To the best of author’s knowledge, this is the first flexible full duplex antenna designed, achieving a high isolation level of -50 dB. Moreover, wide bandwidth, improved gain, and radiation efficiency, low cost, easy fabrication, and robust performance make it a good option for 5.8 GHz wearable applications. Secondly, a simple and compact CPW-fed circularly polarized antenna is presented. The proposed antenna consists of a modified “S” shaped patch, which has slots in three different places along with a slot in the ground plane. These slots contribute to increasing the bandwidth of the axial ratio. The antenna has a 3 dB axial ratio bandwidth of 10.47% (4.07 GHz- 4.52 GHz) and an impedance bandwidth of 17.53% (3.8 GHz - 4.53 GHz) covering the full region of axial ratio band. Moreover, this antenna is designed using PET paper which makes it flexible in nature and the first flexible antenna in the discussed frequency range to the best of author’s knowledge. Finally, an inkjet printed circularly polarized antenna using CPW feeding on PET substrate is proposed. The antenna is designed and optimized using ANSYS HFSS, which operates at 4.01 GHz - 5.05 GHz and 6.23 GHz - 7.58 GHz with a return loss of < -10 dB. On top of that, the antenna shows an axial ratio of less than 3 dB at 4.23 GHz - 4.62 GHz and 7.11 GHz - 7.36 GHz, whereas left hand circular polarization (LHCP) is observed in the first band and right hand circular polarization (RHCP) is observed in the second band. The dimension of the antenna is 31 mm x 37 mm x 0.135 mm. Measurement of the fabricated version shows good agreement with the simulated version. To the best of author’s knowledge, this antenna is the first flexible CPW-fed circularly polarized antenna with dual band.

Inkjet Printed Flexible Patch Antennas for Full Duplex and Circular Polarization Applications

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