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A compact quasi-isotropic dielectric resonator (DR) antenna (DRA) with filtering response is first investigated in this communication. The cylindrical DRA is fed by a microstrip-coupled slot, exciting in its ${\text {HEM}}_{11 \delta }$ mode which radiates like a magnetic dipole. A small ground plane is used for this DRA and it radiates like an electric dipole. The combination of the two orthogonal dipoles leads to a quasi-isotropic radiation pattern, with gain deviation as low as 5.8 dB in the 360° full space. To integrate the filtering function, the microstrip feed-line and the ground plane are turned upside down, and further two stubs with different lengths are used together to excite the DR. Due to the different loading effects of the feeding stubs, two resonances of the DR ${\text {HEM}}_{11 \delta }$ mode are excited in the passband, effectively enhancing the bandwidth of DRA ($\varepsilon _{r} = 20$) to 7%. Furthermore, two controllable radiation nulls are generated by the DR loaded microstrip feed-line, bringing about high frequency selectivity at the edges of the passband and a quasi-elliptic bandpass response. For demonstration, a prototype operating at 2.4 GHz was fabricated and tested; reasonable agreement is obtained between the simulated and measured results. [ABSTRACT FROM AUTHOR]

A wideband filtering patch antenna is investigated in this paper. The patch antenna is fed by an F-shaped probe, which consists of one upper and two lower horizontal arms, as well as a vertical arm that connects them. Owing to the novel excitation scheme, two probe modes along with a patch mode are simultaneously excited within the passband, producing a wide bandwidth of 21.3% with stable antenna gains and radiation patterns. Meanwhile, cross-coupling is constructed in the antenna, generating two symmetrical radiation nulls right at the two sides of the passband. Consequently, a compact filtering antenna with bandpass response and high selectivity is obtained, without utilizing any extra filtering circuit. This design is also extended to realize a reconfigurable filtering antenna. Two varactor diodes are embedded in the F-shaped probe to continuously tune the frequency of the operating band from 2.05 to 2.52 GHz. The antenna bandwidth can be flexibly tuned from 2.2% to 21.3%, and simultaneously good filtering performance is kept during the tuning of different states. [ABSTRACT FROM AUTHOR]

A compact single-polarized filtering dielectric resonator (DR) antenna (DRA) with high selectivity is investigated. The DRA is fed by hybrid microstrip line/conformal strip, excited in its fundamental TE $_{1\delta 1}^{y} $ mode. Owing to different loading effects of the microstrip stub and conformal strip, the resonance frequency of TE $_{1\delta 1}^{y}$ mode excited by the two feed lines is slightly different. Such stepping resonances yield a wide bandwidth of 21.9% and a very flat gain of 5.1 dBi. The hybrid-feeding scheme also establishes a cross-coupled structure in the DRA, which introduces two radiation nulls right near the band edges. A compact wideband filtering DRA (FDRA) with quasi-elliptic bandpass response is, therefore, obtained without requiring any specific filtering circuit. This single-polarized design is also modified to realize a dual-polarized FDRA by adding another orthogonal port with the same feeding scheme. To reduce mutual coupling between the two ports, the microstrip stubs are folded to L shape, and four additional metal posts are inserted into the DR. As a result, the isolation is improved by 14 dB, from 7.2 to 21.2 dB. [ABSTRACT FROM AUTHOR]

A wideband omnidirectional dielectric resonator antenna (DRA) with filtering response is investigated. The DRA is placed on a circular patch and excited by a hybrid feed that consists of a probe and a metallic disk. Two omnidirectional DR modes (TM 01\delta and TM013 modes) along with a patch mode and a probe mode are simultaneously excited by the hybrid feed, providing a broad bandwidth of 52.8%. The feeding scheme also establishes a cross-coupled structure in the DRA, which introduces a radiation null at the upper edge of the passband. A ring slot and four shorting pins are loaded on the patch to provide another radiation null at the lower edge of the passband. Consequently, a compact wideband filtering DRA (FDRA) with quasi-elliptic bandpass response is obtained without requiring specific filtering circuits. This wideband design is also modified to realize a dual-band FDRA. The metallic disk of the hybrid feed is moved to touch the upper DR face of the cylindrical hole. It divides the wide passband into two separate bands, giving a flat stopband between them. Four additional rectangular ring slots and shorting pins are fabricated on the ground plane to further widen the bandwidth and improve the filtering performance of the second band. As a result, a dual-band FDRA with the bandwidths of 10.1% and 3.73% is achieved. In each design, both the measured and simulated out-of-band suppression levels are about 15 dB. [ABSTRACT FROM PUBLISHER]