Abstract
A miniature circularly polarized filtering antenna device is presented here. The device consists of circular radiating patch impeccably coupled using pins to strip line circuits having open loop ring resonators. In proposed design the last stage of filter acts as radiating patch and having low profile of size 0.57λ0 x 0.57λ0 x 0.07λ0 at center frequency 4.26GHz. Filtering circuit improves wide impedance bandwidth and axial ratio 3dB bandwidth. It gives a deep null at upper and lower band edges of filter response. The CP version develops from two LP design by introducing a T-shaped near-field resonant parasitic element near the probe to create two transmission paths with an inherent 90° phase difference. The filtenna is design, fabricated and measured having gain more than 2.5dB and reflection coefficient (S11) < -14dB for an impedance bandwidth of 580MHz from 4.06 to 4.64GHz. Fractional bandwidth, which is 13.33%, gives good candidature for variety of wireless applications. The developed circularly polarized co-design filtering antenna is verified using full wave models and testing. The filtering antenna is useful for biomedical applications such as wearable devices and 5G applications.
Keywords: Circularly Polarized, Compact Antennas, Filtennas, Linearly Polarized Antennas, Low Profile.