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A new design for circularly-polarized (CP) slot antennas is first described. The antenna is a combination of a shorted square-ring slot and an L-shaped linear slot, and its CP operation frequency can be easily tuned under the condition that the slot area is unchanged. Based on the CP design, two reconfigurable slot antennas are then developed. One is a frequency reconfigurable antenna, whose CP operation frequency can be switched between two adjacent frequencies. The other is a polarization reconfigurable antenna, whose polarization can be switched between two orthogonal CP senses. The two reconfigurable antennas are realized using PIN diodes. Details of the designs and experimental results are shown. [ABSTRACT FROM AUTHOR]

The design of an aperture-coupled microstrip patch antenna whose radiation can be switched between circular polarisation (CP) and linear polarisation (LP) states is presented. For the proposed design, the CP and LP radiations are excited through the couplings of a ring slot and an open-ring slot in the ground plane, respectively. The effects of the key parameters of the proposed design on the CP and LP performances are investigated in details. A prototype that uses a pin diode to reconfigure the coupling slot is implemented and tested. From the obtained results, the prototype has a cross polarisation level of more than 25 dB when it is operated at the LP state and an axial ratio of less than 3 dB when it is operated at the CP state. Moreover, the two states share a 10 dB input impedance bandwidth. Consequently, the proposed reconfigurable microstrip antenna has the feature of polarisation diversity at a fixed frequency band. [ABSTRACT FROM AUTHOR]

A novel design of a printed ring-slot antenna with circular polarisation (CP) is first proposed. The CP radiation of the slot antenna is achieved by a series microstrip-line feed configuration. Using the single CP slot antenna as an array element, the 1 × 2 and 2 &times 2 slot arrays are constructed and measured. To obtain wider CP bandwidth, phase sequential rotation technique is applied to the feed network of these printed slot arrays. The experimental results show that the 2 × 2 slot array antenna is capable of 15% bandwidth for an axial ratio of less than 3 dB. [ABSTRACT FROM AUTHOR]

A single-feed dual-frequency microstrip patch antenna that can produce dual circular polarisations (CP) is presented. The microstrip antenna has an annular-ring patch and is excited by an L-shaped microstrip line through the coupling of a ring slot in the ground plane. The occurrence of the dual CP is because the magnetic currents circulating along the ring slot at two specific frequencies have opposite flowing directions. Both simulated and measured results are provided to validate the CP performance of the proposed antenna. [ABSTRACT FROM AUTHOR]

Presents the novel design of the circular polarization (CP) for an annular-ring antenna operated at its TM11 and TM12 modes. Indication that the CP radiations of the proposed design are achieved by placing an L-shaped strip connected to two orthogonal sides of the inner boundary of the annular patch; Observation that broadside radiation patterns with good CP characteristics can be obtained at the two operating resonant modes.