A wideband, pattern-reconfigurable antenna is reported that is, for example, a good candidate for ceiling-mounted indoor wireless systems. Switchable linearly polarized broadside and conical radiation patterns are achieved by systematically integrating a wideband low-profile monopolar patch antenna with a wideband L-probe fed patch antenna. The monopolar patch acts as the ground for the L-probe fed patch, which is fed with a coaxial cable that replaces one shorting via of the monopolar patch to avoid deterioration of the conical-beam pattern. A simple switching feed network facilitates the pattern reconfigurability. A prototype was fabricated and tested. The measured results confirm the predicted wideband radiation performance. The operational impedance bandwidth, i.e., |S ₁₁ | ≤ -10 dB, is obtained as the overlap of the bands associated with both pattern modalities. It is wide, from 2.25 to 2.85 GHz (23.5%). Switchable broadside and conical radiation patterns are observed across this entire operating bandwidth. The peak measured gain was 8.2 dBi for the broadside mode and 6.9 dBi for the conical mode. The overall profile of this antenna is 0.13λ 0 at its lowest operating frequency.

This communication introduces a polarization reconfigurable wideband circularly polarized (CP) antenna, which consists of four radiating arms connected to a reconfigurable feeding network. The four radiating arms excited by the feeding network are able to generate wideband CP waves with bidirectional radiation patterns in free space. In order to increase the gain and obtain a broadside radiation pattern, the proposed antenna is placed above a metallic reflector with the distance of quarter wavelength at the center frequency. In addition, polarization reconfigurability is realized by utilizing PIN diodes in the feeding transmission lines such that left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) modes can be selectively excited by controlling the on/off states of the PIN diodes. The proposed antenna exhibits a wide impedance bandwidth of 80% and an overlapped axial ratio (AR) bandwidth of 23.5% for both modes. The antenna gain is stable across the operating bandwidth with the peak gain of 4.8 dBic. The antenna has a wide AR beamwidth of 90°. The presented work is suitable for GPS, CNSS, or RFID applications.

Pattern reconfigurable antennas with multiple switchable beams, especially with both boresight and endfire directions, are highly desired for wireless communications. In this letter, a novel pattern reconfigurable antenna is proposed that provides an efficient solution. By reconfiguring parasitic strip lines placed around a radiating dipole and reflecting metal pieces under the dipole using PIN diodes, the antenna main beam can be switched to five directions in elevation plane, approximately from -90° (left endfire), -45°, 0° (boresight), +45°, to +90° (right endfire). The proposed antenna operates at 2.45 GHz with dimensions of about 0.57${\lambda}{\times}$0.45${\lambda}{\times}$0.28${\lambda}$. An antenna prototype is fabricated and measured. For all five directional beams, the measured ${\vert}$S11${\vert}$values are below -13 dB, and the measured realized gains range from 5.2-6.5 dBi. They agree reasonably well with the simulated ones.

This paper presents a multi-polarization reconfigurable antenna with four dipole radiators for biomedical applications in body-centric wireless communication system (BWCS). The proposed multi-dipole antenna with switchable 0°, +45°, 90° and -45° linear polarizations is able to overcome the polarization mismatching and multi-path distortion in complex wireless channels as in BWCS. To realize this reconfigurable feature for the first time among all the reported antenna designs, we assembled four dipoles together with 45° rotated sequential arrangements. These dipoles are excited by the same feeding source provided by a ground tapered Balun. A metallic reflector is placed below the dipoles to generate a broadside radiation. By introducing eight PIN diodes as RF switches between the excitation source and the four dipoles, we can control a specific dipole to operate. As the results, 0°, +45°, 90° and -45° linear polarizations can be switched correspondingly to different operating dipoles. Experimental results agree with the simulation and show that the proposed antenna well works in all polarization modes with desirable electrical characteristics. The antenna has a wide impedance bandwidth of 34% from 2.2 to 3.1 GHz (for the reflection coefficient ≤-10 dB) and exhibits a stable cardioid-shaped radiation pattern across the operating bandwidth with a peak gain of 5.2 dBi. To validate the effectiveness of the multi-dipole antenna for biomedical applications, we also designed a meandered PIFA as the implantable antenna. Finally, the communication link measurement shows that our proposed antenna is able to minimize the polarization mismatching and maintains the optimal communication link thanks to its polarization reconfigurability.

An omnidirectional circularly polarized (OCP) antenna operating at 28 GHz is reported and has been found to be a promising candidate for device-to-device (D2D) communications in the next generation (5G) wireless systems. The OCP radiation is realized by systematically integrating electric and magnetic dipole elements into a compact disc-shaped configuration (9.23 mm $^{3} =0.008~\lambda _{0}^{3}$ at 28 GHz) in such a manner that they are oriented in parallel and radiate with the proper phase difference. The entire antenna structure was printed on a single piece of dielectric substrate using standard PCB manufacturing technologies and, hence, is amenable to mass production. A prototype OCP antenna was fabricated on Rogers 5880 substrate and was tested. The measured results are in good agreement with their simulated values and confirm the reported design concepts. Good OCP radiation patterns were produced with a measured peak realized RHCP gain of 2.2 dBic. The measured OCP overlapped impedance and axial ratio bandwidth was 2.2 GHz, from 26.5 to 28.7 GHz, an 8 % fractional bandwidth, which completely covers the 27.5 to 28.35 GHz band proposed for 5G cellular systems.