In this article, a compact coplanar waveguide (CPW) technique based ultra-wideband multiple-input-multiple-output (MIMO) antenna is proposed. The design is characterized by a broad impedance bandwidth starting from 3 GHz to 11 GHz (266%). The overall size of the MIMO design is 60 × 60 mm 2 (1.24 × 1.24 𝝀 𝒈 𝟐 @ 3 GHz) with a thickness of 1.6 mm. To make the design ultra-wideband, the proposed MIMO antenna design has four jug-shaped radiating elements. The design is printed on a FR-4 substrate (relative permittivity of 𝜀r = 4.4 and loss tangent of tan𝛿 = 0.025). The polarization diversity phenomenon is realized by placing four antenna elements orthogonally. This arrangement increases the isolation among the MIMO antenna elements. The simulated results of the ultra-wideband MIMO antenna are verified by measured results. The proposed MIMO antenna has a measured diversity gain greater than 9.98, envelope correlation coefficient (ECC) less than 0.02, and good MIMO performance where the isolation is more than -20dB between the elements. The group delay, channel capacity loss (CCL), and the total active reflection coefficient (TARC) multiplexing efficiency and mean effective gain results are also analyzed. The group delay is found to be less than 1.2ns, CCL values calculated to be less than 0.4 bits/sec/Hz, while the TARC is below -10dB for the whole operating spectrum. The proposed design is a perfect candidate for ultra-wideband wireless communication systems and portable devices.INDEX TERMS Multi-input-multi-output (MIMO), ultra-wideband, envelope correlation coefficient (ECC), channel capacity loss (CCL), group delay, total active reflection coefficient (TARC).
Biomedical implantable antennas have a major role in biomedical telemetry applications. Therefore, a compact-size low-profile implantable antenna working in industrial, scientific, and medical (ISM) band at 915 MHz is presented. The presented antenna is a simple slotted patch fed with a coaxial probe of 50 Ω impedance. The patch consists of four slotted resonators printed on a flexible Roger Duroid RT5880 substrate ( ε r = 2.2 , tan δ = 0.0009 ) with the standard thickness of 0.254 mm. The complete volume of the designed antenna is 7 mm × 7 mm × 0.254 mm ( 0.08 λ g × 0.08 λ g × 0.003 λ g ). The antenna covers the bandwidth from 800 MHz to 1 GHz (200 MHz) inside skin tissue. A good agreement between the simulation and measurements of the antenna has been obtained. Finally, the specific absorption rate (SAR) values have also been analyzed through simulations as 8.17 W/kg inside skin over 1 g of mass tissue. The proposed SAR values are less than the limit of the Federal Communications Commission (FCC). This antenna is miniaturized and an ideal applicant for applications in biomedical implants.
Biomedical implantable antennas play a vital role in medical telemetry applications. These types of biomedical implantable devices are very helpful in improving and monitoring patients’ living situations on a daily basis. In the present paper, a miniaturized footprint, thin-profile bear-shaped in-body antenna operational at 915 MHz in the industrial, scientific, and medical (ISM) band is proposed. The design is a straightforward bear-shaped truncated patch excited by a 50-Ω coaxial probe. The radiator is made up of two circular slots and one rectangular slot at the feet of the patch, and the ground plane is sotted to achieve a broadsided directional radiation pattern, imprinted on a Duroid RT5880 roger substrate with a typical 0.254-mm thickness (= 2.2, tan = 0.0009). The stated antenna has a complete size of 7 mm × 7 mm × 0.254 mm and, in terms of guided wavelength, of 0.027 × 0.027 × 0.0011. When operating inside skin tissues, the antenna covers a measured bandwidth from 0.86 GHz to 1.08 GHz (220 MHz). The simulations and experimental outcomes of the stated design are in proper contract. The obtained results show that the calculated specific absorption rate (SAR) values inside skin of over 1 g of mass tissue is 8.22 W/kg. The stated SAR values are lower than the limitations of the federal communications commission (FCC). Thus, the proposed miniaturized antenna is an ultimate applicant for in-body communications
Implantable antennas have a vital role in biomedical telemetry applications. Therefore, a compact low-profile circularly polarized biomedical implantable antenna operational in industrial, scientific, and medical (ISM) band at 2.45 GHz is reported. The presented antenna is fed by a modified co-planar waveguide (CPW) technique to keep the size of the antenna compact. The radiating monopole consists of a slotted rectangular patch with one slot at an angle of 45 degree and truncated small patch on the left end of the CPW ground plane to make the antenna circularly polarized at the required frequency band. A flexible Roger Duroid RT5880 substrate (εr = 2.2, tanδ = 0.0009) with the standard thickness of 0.254 mm is used to achieve bending abilities. The complete volume of the designed antenna is 21 mm × 13.5 mm × 0.254 mm (0.25 × 0.16 × 0.003 ). The antenna covers the bandwidth from 2.35-2.55 GHz (200 MHz) in free space while from 1.63 GHz to 2.8 GHz (1.17 GHz) inside skin tissue. As the designed antenna is operational in skin tissue with larger bandwidth, the bending analysis along the (x & y)-axis is also analyzed through the simulation. A good agreement between the simulation and measurements of the bended antenna is observed. The measured -10dB impedance bandwidth and the 3dB axial ratio (AR) bandwidth inside skin-mimicking gel are 47.7% and 53.8%, respectively at 2.45 GHz frequency band. Finally, the specific absorption rate (SAR) values are also analyzed through simulations, and it is 0.78 W/kg inside skin over 1 g of mass tissue. The proposed SAR values are less than the limit of the federal communication commission (FCC). This antenna is miniaturized and an ideal applicant for the biomedical implantable applications.
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