In this study, the authors present a simple reconfigurable multiband antenna with two PIN diode switches for worldwide interoperability for microwave access (WiMAX)/wireless local area networks (WLAN) applications. The antenna permits reconfigurable switching in up to ten frequency bands between 2.2 and 6 GHz, with relative impedance bandwidths of around 2.5 and 8%. The proposed antenna has been simulated using computer simulation technology microwave studio software and fabricated on an FR‐4 substrate. It is compact, with an area of 50 × 45 mm ² , and has a slotted ground substrate. Both measured and simulated return loss characteristics of the optimised antenna show that it satisfies the requirement of 2.4/5.8 GHz WLAN and 3.5 GHz WiMAX antenna applications. Moreover, there is good agreement between the measured and simulated results in terms of radiation pattern and gain.

This paper presented a new circular polarization reconfigurable antenna for 5G wireless communications. The antenna, containing a semicircular slot, was compact in size and had a good axial ratio and frequency response. Two PIN diode switches controlled the reconfiguration for both the right-hand and left-hand circular polarization. Reconfigurable orthogonal polarizations were achieved by changing the states of the two PIN diode switches, and the reflection coefficient |S11| was maintained, which is a strong benefit of this design. The proposed polarization-reconfigurable antenna was modeled using the Computer Simulation Technology (CST) software. It had a 3.4 GHz resonance frequency in both states of reconfiguration, with a good axial ratio below 1.8 dB, and good gain of 4.8 dBic for both modes of operation. The proposed microstrip antenna was fabricated on an FR-4 substrate with a loss tangent of 0.02, and relative dielectric constant of 4.3. The radiating layer had a maximum size of 18.3 × 18.3 mm², with 50 Ω coaxial probe feeding.

A compact planar monopole antenna is proposed for ultra‐wideband applications. The antenna has a microstrip line feed and band‐rejected characteristics and consists of a ring patch and a partial ground plane with a defective ground structure of rectangular shape. An annular strip is etched above the radiating element and two slots, one C‐shaped and one arc‐shaped, are embedded in the radiating patch. The proposed antenna has been optimised using bio‐inspired algorithms such as the particle swarm optimisation and the firefly algorithm, based on a new software algorithm (Antenna Optimizer). Multi‐objective optimisation achieves rejection bands at 3.3–3.7 GHz for Worldwide Interoperability for Microwave Access, 5.15–5.825 GHz for the 802.11a wireless local area network system or HIPERLAN/2, and 7.25–7.745 GHz for C‐band satellite communication systems. Validated results show wideband performance from 2.7 to 10.6 GHz with S ₁₁ < −10 dB. The antenna has compact dimensions of 28 × 30 mm ² . The radiation pattern is comparatively stable across the operating band with a relatively stable gain except in the notched bands.

A compact dielectric resonator antenna (DRA) for wideband applications is proposed. Two cylindrical dielectric resonators that are asymmetrically located with respect to the center of a rectangular coupling aperture are fed through this aperture. By optimizing the design parameters, an impedance bandwidth of about 29%, covering the frequency range from 9.62 to 12.9 GHz, and a gain of 8 dBi are obtained. Design details of the proposed antenna and the results of both simulation and experiment are presented and discussed.

This article presents a miniaturized triple-band antenna for Internet of Things (IoT) applications. The miniaturization is achieved by using a split square ring resonator and half ring resonator. The antenna is fabricated on an FR4 substrate with dimensions of (33 × 22 × 1.6) mm³. The proposed antenna resonates at the frequencies 2.4 GHz, 3.7 GHz, and 5.8 GHz for WLAN and WiMax applications. The obtained −10 dB bandwidth for the three bands of the proposed antenna are 300 MHz, 360 MHz, and 900 MHz, respectively. The measured reflection coefficient values of the proposed antenna corresponding to each resonant frequency are equal to −14.772 dB, −20.971 dB, and −28.1755 dB, respectively. The measured gain values are 1.43 dBi, 0.89 dBi, and 1 dBi, respectively, at each resonant frequency. There is a good agreement between the measured and simulated results, and both show an omnidirectional radiation pattern at each of the antenna resonant frequencies that is suitable for IoT portable devices.

A low profile and compact size cognitive radio (CR) sensing/communicating antenna system is presented in this paper. A slotted elliptical monopole antenna is proposed as an ultra-wideband sensing antenna for the CR system, while the CR communication relies on a triangular reconfigurable monopole antenna. Two PIN diodes are attached to the reconfigurable antenna to provide four different wideband CR communications with variable bandwidths. The simulation and measured results are in good agreement, and they demonstrate that both antennas have an omnidirectional radiation pattern with acceptable gain values compatible with the portable CR devices. In addition, the results show low mutual coupling between the sensing antenna and the communicating antenna that reaches to values less than −16 dB for all operational modes of the PIN diodes.