A polarization-reconfigurable cylindrical dielectric resonator antenna (DRA) based on a tunable feed network is presented in this paper. HEM 11δ modes excited by two-port side-fed probes are adapted to design the proposed DRA. Polarization reconfigurable characteristic can be obtained by a tunable feed network that consists of Wilkinson equal power divider, parasitic elements used for phase shifters, and p-in diodes between them. By controlling the four pairs of p-in diode switches to active corresponding elements as effective phase shifters, two sources with equal amplitude and 0 • or ±90 • phase differences are obtained to generate linear-polarized (LP) or circular-polarized (CP) states, respectively. A fully functional prototype of the proposed antenna with the dimension of 0.55λ×0.55λ×0.14λ has been designed, fabricated, and tested. The results indicate that the proposed DRA can achieve the bandwidths of more than 30% for both impedance bandwidth and 3-dB axial ratio bandwidth at CP states, and two LP states with the impedances of 6.3% and 9.5%. Stable directional patterns and realized gains are obtained for all the states. These performances make the proposed DRA suitable for polarization diversity scenarios in communication systems. INDEX TERMS Cylindrical dielectric resonator antenna, HEM 11δ mode, polarization reconfiguration, Wilkinson power divider, p-in diodes.
A compact, frequency-reconfigurable dielectric resonator antenna (DRA) with wideband and continuously tunable narrowband states is presented. It is intended for the application scenario in the cognitive radio system. The wideband state is the sensing state and operationally covers 3.82-8.94 GHz. The narrowband states are intended to cover communications within the 5.14-5.98 GHz range, which completely covers the WLAN frequency bands. Three p-in diodes are employed to switch between wide and some narrowband operational states by selecting the corresponding path. A varactor diode is used to shift the operational frequencies continuously among the narrowband states. The proposed DRA consists of a rectangular dielectric resonator excited by microstrip feedline with a reconfigurable filter; it has a compact dimension: 0.31λ L × 0.41λ L × 0.06λ L , where the wavelength λ L corresponds to the lower bound of its operating frequencies. The measured reflection coefficients, far-field radiation patterns, and realized gains for both operation states are in good consistent with their simulated values. INDEX TERMS Cognitive radio, dielectric resonator antenna, frequency reconfiguration, filter antenna, continuously tuning.
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