Design of pattern-reconfigurable circularly polarized unidirectional antenna based on quasi-radiator for ISM applications.

A pattern-reconfigurable circularly polarized antenna for 2.45 GHz industrial, scientific, and medical (ISM) band applications is designed in this work. The proposed antenna consists of a slotted-stepped monopole connected to a rectangular ground plane via a shorting side-stub. This converts the omnidirectional radiation pattern of the antenna into stable unidirectional radiation. To dynamically steer the realized pattern, two switchable RF PIN diodes are jointly incorporated into the side-stubs to achieve symmetrical radiations in specific operating modes. In this way, the radiation patterns can be simultaneously tuned in the ± y directions by the simple switching of the PIN diodes ON and OFF. The fabricated prototype achieves an S 11 smaller than -10dB within the 3dB axial ratio (AR) bandwidth with stable far-field patterns. The antenna maintains a low-profile and compact size of 0.055 λ 0 2 which makes it suitable for body-centric wireless communication (BWC) and personal wireless area networks.

Design and circuit analysis of a single and dual band-notched UWB antenna using vertical stubs embedded in feedline.

Within the frequency band designated by the FCC for UWB systems, there are other frequency bands that are also designated for use for other technologies like WLAN (5.15 - 5.35 GHz) and WiMAX (3.3-3.7 GHz). These systems can cause interference with UWB systems when operated at the same time. Therefore, an antenna operating in the UWB spectrum needs to have band-notch capabilities in order to mitigate interference resulting from nearby communication systems operating within the UWB frequency band. In this paper, the notched bands are achieved by using vertical stubs protruded from a microstrip feedline. The antenna is etched on a 25 × 30 mm2 substrate. Two antenna structures are presented; one is designed to notch an intended narrowband from 3.3 - 3.6 GHz and the second is designed to include an additional band notch from 5.15 - 6 GHz. The simulations and measurements show that the proposed antennas achieve an ultra-wide bandwidth of 3-10.6 GHz with successful single and dual band-notches, good gain and good group delay rejection in the notch bands. Stable radiation patterns with low cross polarization are also realized across the operating bandwidth. A detailed analysis of how the filtering is also achieved using circuit theory is presented in this work as well.