In this paper, a frequency reconfigurable multiband multiple-input-multiple-output (MIMO) antenna is developed for 5G communication systems. The presented MIMO antenna element consists of a 50 Ω microstrip line, a rectangular monopole divided into two patches, and a partial ground plane. A split-ring resonator (SRR) is introduced into the upper patch to cover multiple 5G application bands, and an RF PIN diode is embedded between the upper and lower patches to enable the frequency diversity feature. In order to design a MIMO antenna with improved inter-element isolation, four antenna elements are orthogonally located with ground planes connected to each other. The antenna design covers the n41/n46/n48/n79 5G application bands. The prototype MIMO antenna is developed on the FR-4 substrate, and the measured results match with the simulated outcomes. The overall footprint of the prototype antenna is 70 × 70 × 1.6 mm³.

In this paper, an inset-fed dual-band patch antenna with truncated corners is presented. The ground plane of the antenna is loaded with D-shaped complementary split ring resonator (D-CSRR) structures to obtain dual-band resonance and size miniaturization. The overall electrical size of the antenna is 0.29λ₀ × 0.25λ₀ and patch size is 0.14λ₀ × 0.13λ₀, where λ₀ is evaluated at the lowest resonating frequency. The proposed planar antenna is low profile and does not need a dual feed or any external feeding mechanism for obtaining circular polarization. A size reduction of 66% is achieved as compared to the conventional patch antenna. The newly designed D-CSRR results in better miniaturization factor making proposed antenna suitable for modern wireless applications. The prototype of the antenna is fabricated and experimental findings are compared with electromagnetic and analytical results.

In this work, a new compact, low profile, frequency, and end-fire pattern reconfigurable antenna is presented. The proposed antenna consists of four parasitic elements and an electric-inductive-capacitive (ELC) resonator enclosed with a closed ring resonator (CRR). The reconfigurability in the proposed antenna is achieved with the help of five PIN diodes (D1–D5) embedded on the top surface of the substrate. The diode (D1) is implanted between ELC and CRR resonators for frequency reconfigurability. The other four diodes (D2–D5) are implanted between the ground plane and four parasitic elements to control the electrical length of the ground plane to achieve pattern diversity. The ground plane and parasitic elements steer the primary omni-directional beam to bi-directional and uni-directional end-fire radiation at multiple frequencies. The proposed antenna exhibits multiband operation and end-fire pattern diversity depending upon the different states of PIN diodes. The overall size of the proposed antenna is 0.20λ₀× 0.17λ₀× 0.009λ₀, where λ₀ is calculated at the lowest resonance frequency. The impedance bandwidth of the antenna ranges from 1.45 to 26.22%, while peak gain varies from 0.86 to 3.86 dBi depending upon the state of operation. The measured results are in agreement with the simulated results, which confirm the frequency and pattern diversity performance of the antenna. The proposed antenna can be used in back-to-back repeater systems.

In this paper, a low-profile, compact hexa-band pattern reconfigurable antenna is presented. The proposed antenna consists of a square patch fed by a microstrip line of 50 Ω and a ground plane. The ground is loaded with a pair of the split-ring resonators and two rectangular slots that offer multiband operation and pattern reconfigurability. On the top surface of the antenna, two diodes (D1 and D2) are introduced to control current distribution and to achieve pattern diversity. The antenna operates at 2.4 GHz, 3.8 GHz, 4.35 GHz, 4.7 GHz, 5.5 GHz, and 6.25 GHz, with impedance bandwidth in the range of 1.01% to 4.09%. Depending upon the state of operation, the gain of the proposed reconfigurable antenna varies from 1.90 dBi to 2.82 dBi and pattern tilt of ±10^° at 3.8 GHz, ±45^° at 4.35 GHz, ±25^° at 4.7 GHz, ±45^° at 5.5 GHz, and ±45^° at 6.25 GHz is observed. The prospective antenna is fabricated and practical inferences are compared with the simulated results. The experimental outcomes are found in good agreement with the simulated results, which validates the beam steering capability of the antenna.

In the present article, a design approach to accomplish circular polarization-based rhombus ring microstrip-fed monopole antenna working at 5.8 GHz for wireless body area network (WBAN) applications is proposed. The input impedance calculation using an electromagnetic theory of transmission line in a travelling wave coupled to the parallel-plate inductor model is conducted. Radiated electric field pattern calculation of the conventional square ring microstrip patch antenna (MSPA) using Biot and Savart’s law is reported. The circular polarization of the proposed antenna is accomplished by loading the radiating path with a capacitive element sectioned in the neighbourhood of the feed line. The proposed planar monopole antenna of volume ( is evaluated at the resonant frequency of 5.8 GHz) achieves a -10 dB impedance bandwidth of 86.20% in the band (3-8 GHz) with a stable real gain of 8.29 dBic in circular polarization at the resonant frequency of 5.8 GHz and axial ration bandwidth of about 32.75% in the (5-6.9 GHz) band. Specific absorption rate (SAR) evaluation of the studied antenna is computed numerically on a part of the human phantom model to justify its use in WBAN applications. It is noted that the maximum amount of radiation absorbed by a part of the human phantom model is limited to a maximum SAR value of 1.45 W/kg and 0.754 W/kg on 1 g and 10 g of tissue mass, respectively. The prospective design has been fabricated and tested, and the experimental results are in good agreement with the simulation outcomes.