Super high gain substrate integrated clamped-mode printed log-periodic dipole array antenna," IEEE Trans.Abstract-This communication presents some interpretative studies on a circularly polarized broadband patch antenna using an artificial ground structure (AGS). This patch antenna has a broadband characteristics in both impedance and axial ratio, which are more than 20% and 40%, respectively. The principle to expand the 3-dB axial ratio characteristics is discussed using a combination of circularly polarized patch antenna and an AGS polarizer. Furthermore, a broadband matching method using an extended outer conductor of coaxial cable is discussed. The mechanism of the matching structure is also discussed.Index Terms-Artificial ground structure (AGS), artificial magnetic conductor (AMC), axial ratio, broadband antenna, circular polarization, matching, microstrip patch antenna, polarizer.
Abstract-Bandwidth enhancement technique of circularly polarized square slot antenna is presented in this paper. A square slot antenna with the components of L-probe separated could achieve an axial ratio (AR) bandwidth of 33.84%. Placing Stubs in the slot by studying the electric field behaviour could enhance the AR bandwidth by around 10%. Creating an L-shaped slot on the ground plane, where the electric field rotates in the desired clockwise direction, can further enhance the bandwidth by 7%. A < −10 dB S 11 bandwidth of 46.15% and < 3 dB AR bandwidth of 50.35% could be achieved with the present design. Unidirectional patters are obtained by having a cavity at the wide slot of the antenna and shows a measured bandwidth of 41.79% in S 11 and 44.97% in AR. Both antennas show a cross polarization discrimination of more than 15 dB on a wide azimuth range. The measured results well comply with the simulated results.
Novel circularly polarized antennas with a circular radiating aperture for broadband characteristics are presented in this paper. The vertical and horizontal components of the L-shaped probe are separated and placed at the front and back side of the substrate. The antennas are excited by a microstrip line which is connected to the vertical component of the L-shaped probe and electromagnetically couples the signal to the horizontal component of the L-shaped probe. A novel concept of placing stub in the slot of a planar antenna, by observing the electric field vector behaviour in the slot, is proposed to enhance the axial ratio (AR) bandwidth by around 10%. Unidirectional patterns can be obtained by having a cylindrical cavity of height λ g /4 behind the antenna and is effective when no stubs are placed in the slot. A < 3 dB AR bandwidth of 39.5% with cavity and 41.18% without cavity but with stub in the slot is obtained in simulation and the results well match with the measurement.
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