Search

The demand for wideband circularly polarized (CP) antennas in wireless communication applications has been increasing, given that it offers reliable signals with reduced interference. In particular, planar monopole antennas are a popular choice for use in CP applications due to their compact size and ease of integration. However, achieving CP characteristics often requires complex modifications, an increased antenna size, and design complexity. To address these challenges, this study proposes a simplified radiator structure modification for CP planar monopole antennas and validates the performance of the proposed antenna for ultra-wideband (UWB) applications by conducting both frequency-domain and time-domain analyses. The size of the proposed antenna is 34 mm × 41 mm × 1.6 mm, with FR-4 as the substrate. Both the −10 dB S11 bandwidth and 6 dB axial ratio axial ratio is 3.46–5.5 GHz, with the radiation patterns in the frequency range of interest being omni-directional. The proposed UWB CP antenna also yields decent antenna performance in time-domain analyses, such as the antenna fidelity factor and the system fidelity factor.

Repeaters have been widely used to improve communication quality and extend the coverage areas of wireless communication systems. However, mutual coupling between the Tx and Rx antennas significantly deteriorates the performance of repeater systems. This work presents a high-isolation repeater antenna operating in a frequency range of 3.6–3.7 GHz in a 5G communication system. Perpendicularly arranged microstrip patch antennas are used because this arrangement can lead to greater isolation than a parallel arrangement. However, the perpendicular arrangement results in radiation pattern distortion due to the ground mode. A novel defected ground structure (DGS) is developed to suppress the ground mode and simultaneously reduce the mutual coupling between the Tx and Rx antennas. An electromagnetic bandgap (EBG) is additionally employed to further increase isolation. The measurement results of a fabricated repeater antenna show no radiation pattern deformation and an isolation improvement of 28 dB over the repeater antenna without the DGS and EBG.

External partial discharge (PD) sensors for the ultra-high frequency (UHF) method are widely used to detect the PD signals in high-voltage power equipment for ease of installation and maintenance. However, conventional external PD sensors detect not only PD signals but also LTE signals; thus, a microwave filter is usually employed. In this work, a UHF filtering antenna (filtenna) is proposed as the external PD sensor to detect PD signals and simultaneously block LTE-band signals. The proposed UHF filtenna is the printed monopole antenna with a built-in interdigital bandpass geometry, which is selected for its compact size. Measurement results show that the proposed UHF-printed monopole filtenna operates adequately in the frequency range of 1 GHz to 1.6 GHz and simultaneously blocks LTE signals significantly.