A compact four-element multiple-input multiple output (MIMO) antenna is proposed for medical applications operating at a 2.4 GHz ISM band. The proposed MIMO design occupies an overall volume of 26 mm × 26 mm × 0.8 mm. This antenna exhibits a good impedance matching at the operating frequency of the ISM band, whose performance attributes include: isolation around 25 dB, envelope correlation coefficient (ECC) less than 0.02, average channel capacity loss (CCL) less than 0.3 bits/s/Hz and diversity gain (DG) of around 10 dB. The average peak realized gain of the four-element MIMO antenna is 2.4 dBi with more than 77 % radiation efficiency at the frequency of interest (ISM 2.4 GHz). The compact volume and adequate bandwidth, as well as the good achieved gain, make this antenna a strong candidate for bio-medical wearable applications.

This study presents an original asymmetric stepped‐impedance resonator filter combined with meander coupled‐line structures and enabling the realisation of finite transmission zeros (TZs) and the implementation of multi‐band bandpass filters. The meander coupled sections (MCSs) tune the TZs and resonant frequencies: with higher‐order spurious frequencies cancelled by the TZs, a single wideband with wide stopband from 1.18 to 1.84 GHz is possible. Furthermore, by positioning the finite TZs between the high‐order spurious frequencies and adjusting the coupling strength between resonators, a quint‐wideband filter can be realised, with centre frequencies of 1.19, 4.29, 5.43, 6.97, 9.9 GHz and fractional bandwidths of 31.9, 15.4, 15.8, 4.3, 39.2%, respectively. More importantly, two filters with single/quad‐wideband performance can be realised by tuning the parameters of the MCS, and therefore they can be designed separately by using only one original structure. The triple‐wideband filter is realised with the help of the asymmetric parallel uncoupled microstrip section. These filter structures enjoy the advantage of single/multi‐band versatility, structure reusability and simplicity. The good in‐band and out‐of‐band performance, low loss and simple structure of the proposed single/tri/quint‐wideband filters make them very promising for applications in future multi‐standard wireless communication.

In this paper, a new miniaturized compact dual-band microstrip slot antenna is presented. To achieve the dual-band characteristics, two adjunct partial arc-shaped small slots are joined to two main circular slots embedded in the ground of the antenna structure. With a reduced size of 30 × 28.5 × 0.8 mm3, the proposed antenna presents a dual-band characteristic. The design is optimized using a High Frequency Structure Simulator (HFSS) followed by experimental verifications. An impedance bandwidth, for S11≤10 dB, that covers the 1.8 GHz and 2.4 GHz bands is accomplished, which makes the proposed antenna basically suitable for hand-held devices and medical applications. More applications such as digital communication system (DCS) 1.71–1.88 GHz, personal communication services (PCS) 1.85–1.99 GHz, Universal and mobile telecommunications system UMTS 1.92–2.17 GHz, Bluetooth 2.4–2.5 GHz, and Wi-Fi 2.4–2.454 GHz, Industrial Scientific and Medical radio frequency (RF) band ISM-2.4 GHz, Wireless Local Area Network (WLAN-2.4)are possible by simply changing one of the geometrical antenna dimensions. The antenna is characterized by stable radiation patterns as well.

Reconfigurable radiation pattern shaping by means of circular disc planer antenna with a slot ring is presented. The proposed microstrip antenna has an overall dimension of 70×70mm 2 designed on a substrate of a dielectric constant 4.3. The designed antenna operates at 5.35 GHz with a central coaxial probe feed. By altering the configuration of two PIN diodes switches, the designed antenna has three different beam patterns in the yz plane. Biasing each diode separately result in about 60 o change in the main radiation pattern steering angle, while the frequency response are largely maintained. At resonance, the peak gains are approximately 3.5 dB, 4 dB and 4.3 dB, in the three configurations of the diodes. Return losses, peak gains and reconfigurable radiation patterns are reported, which are in very good agreement for WiMax/WiFi (IEEE 802.11a) applications.

A new compact Cylindrical Dielectric Resonator Antenna (CDRA) with a defected ground for ultra-wideband applications is presented. The structure is based on two cylindrical dielectric resonators asymmetrically located with respect to the center of an offset rectangular coupling aperture, with consideration of three and four Dielectric Resonators (DR). The resonant modes generated by the defected ground are studied and investigated. A parametric optimization study of the antenna design has been carried out to determine the optimal dimensions of the defected ground plane, resulting in an impedance bandwidth of over 133% that covers the frequency band from 3.6 GHz to 18.0 GHz. A power gain of about 7.9 dBi has been achieved. Design details and measured and simulated results are presented and discussed. INDEX TERMS Cylindrical dielectric resonators antenna, ultra-wideband, defected ground structure.