In this communication, a biotelemetry device for scalp implantation is proposed with an ultraminiaturized and simple-structured implantable antenna that exhibits dual-band characteristics in the ...industrial, scientific, and medical bands (915 MHz and 2.45 GHz). The proposed system incorporates two batteries and microelectronic components in a total volume of 434.72 mm 3 . The recommended antenna has a reduced volume of 9.8 mm 3 (7 mm <inline-formula> <tex-math notation="LaTeX">\times7 </tex-math></inline-formula> mm <inline-formula> <tex-math notation="LaTeX">\times0.2 </tex-math></inline-formula> mm), which is the smallest antenna presented so far. In homogeneous and heterogeneous environments, the designed antenna system has peak gain values of −28.04 and −28.94 dBi, respectively, at 915 MHz, and −23.01 and −23.06 dBi, respectively, at 2.45 GHz. For validation, the prototype of the antenna and corresponding system are immersed in a 3-D head phantom (saline solution), and the measured results are found in close agreement with the simulation results. Additionally, the data communication range is analyzed through a link budget calculation at several data rates and an input power of −16 dBm. The radiation of the antenna system in the two principal planes (E and H) are similar to being omni-directional and directed away from the anatomical human body model as mandatory for the telemetry applications. Hence, the proposed antenna system can be employed in scalp implantation, especially for intracranial pressure monitoring.
Design and analysis of a dual-band polarization converting metasurface is presented in this letter. The proposed converter, which consists of two square split ring resonators, exhibits peak ...resonances at frequencies of 5.6, 7.3, 8.8, 15.1, and 15.9 GHz. The surface behaves as a polarization converter for linearly polarized incident waves in two frequency ranges, i.e., 5.4-9.0 GHz with a polarization conversion ratio (PCR) <inline-formula><tex-math notation="LaTeX">\geq</tex-math></inline-formula> 93<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula>, and 14.6-16.1 GHz with a PCR <inline-formula><tex-math notation="LaTeX">\geq</tex-math></inline-formula> 99<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula>). The size and thickness of the unit cell are, respectively, <inline-formula><tex-math notation="LaTeX">0.126\lambda _{\mathrm{o}}</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">0.057\lambda _{\mathrm{o}}</tex-math></inline-formula>, where <inline-formula><tex-math notation="LaTeX">\lambda _{\mathrm{o}}</tex-math></inline-formula> is the largest wavelength (corresponding to the lower frequency). The mechanism of polarization conversion is studied by examining the surface currents for all the resonance frequencies. Both simulated and experimental results reveals that the polarization converter can be utilized in C-, X- and Ku-band applications.
Abstract
The manipulation of polarization state of electromagnetic waves is of great importance in many practical applications. In this paper, the reflection characteristics of a thin and dual-band ...metasurface are examined in the microwave frequency regime. The metasurface consists of a 22 × 22 element array of periodic unit cells. The geometry of the unit cell consists of three layers, including a 45° inclined dipole shape metal patch on top, which is backed by a 1.6 mm thick FR-4 substrate in the middle, and a fully reflective metallic mirror at the bottom. The proposed surface is exposed to horizontally (
x
) or vertically (
y
) polarized plane waves and the co and cross polarization reflection coefficients of the reflected waves are investigated experimentally in the 6–26 GHz frequency range. The metasurface is designed to convert incident waves of known polarization state (horizontal or vertical) to orthogonal polarization state (vertical and horizontal) in two distinct frequency bands, i.e. 7.1–8 GHz and 13.3–25.8 GHz. In these two frequency bands the simulated and experimental results are in good agreement. The polarization conversion ratio (PCR) of the surface is greater than 95% in the targeted frequency bands. A detailed parametric analysis of the metasurface is also discussed in this work and it has been estimated that the surface has the additional ability to convert linearly polarized waves to circularly polarized waves at several distinct frequencies. The proposed metasurface can be utilized in sensor applications, stealth technology, electromagnetic measurements, and antennas design.
In this paper two triple-band monopole antennas are proposed for portable wireless applications such as WiFi, WiMAX and WLAN. Two different geometrical structures are used for the radiating elements ...of these antennas, each printed on a low cost FR-4 substrate. Truncated metallic copper ground is used to attain optimum radiation pattern and better radiation efficiency. The frequency of the antennas is reconfigured using a lumped-element switch. The proposed antennas covers three frequency bands 2.45, 3.50 and 5.20GHz depending upon the switching conditions. Both antennas works with an optimum gain (1.7–3.4dB), bandwidth (6–35%), VSWR (<1.5) and radiation efficiency (85–90%). Due to its affordable size (1.6×35×53mm3), the antennas can be used in modern and portable communication devices such as laptops, iPads and mobile phones. The prototype of the antennas are fabricated and the measurements and simulations are found in close agreement.
This paper presents a novel compact unilayer frequency selective surface (FSS) for ultra‐wideband (UWB) applications particularly for gain enhancement of printed antennas. The proposed FSS unit cell ...consists of simple metallic patterns printed on both sides of 14 mm × 14 mm FR4 substrate. The proposed FSS has very low transmission co‐efficient and linearly decreasing reflection phase over the bandwidth of 9 GHz in 3–12 GHz range, which makes it suitable candidate to provide in‐phase reflection for UWB antennas. For the validation of gain‐enhancement capability, the FSS is paired with a general monopole UWB antenna demonstrating an average gain improvement of 4 dB. The antenna composite has a maximum gain of 8.9 dBi.
In this paper, a single layer polarization converting metasurface (PCMS) is designed and analyzed for wideband and high efficient cross polarization conversion (CPC) and radar cross section reduction ...(RCSR). In reflection mode, the PCMS efficiently converts a linearly-polarized (LP) incident electromagnetic (EM) waves to cross-polarized (CP) EM waves from 8.5 to 25.5 GHz with a fractional bandwidth (FBW) of 100%. The polarization conversion ratio (PCR) is more than 90% in the operating band which covers X, Ku, and a portion of K band. There are three resonance frequencies of 9.3, 16.8, and 24.5 GHz over which 100% PCR has been achieved. The unit cell dimensions are 0.2λo×0.2λo (6.8 mm × 6.8 mm) and the height of the substrate is 0.085λo (3 mm), where λo is free space maximum wavelength at the minimum frequency of the operating band. The designed metasurface also performs RCS reduction in chessboard-like array arrangement based on the polarization conversion capability of the proposed PCMS. This method lifts the limitations with conventional techniques such as narrow bandwidth, larger size, and complex to design. The designed array produce a phase difference of (180±37°) between the scattered EM waves which fulfills the criteria for RCS reduction. The different orientations of the same unit cell in the chessboard shaped array result in a different reflection phases. The phase difference between reflected EM waves result in scatter wave cancellation (destructive interference) in the source direction and hence RCS reduction. The PCMS achieves RCSR of less than 10 dB from 6.9 to 25 GHz with a FBW of 114%. The array surface is tested experimentally. Simulated and experimental results are quite similar. The designed PCMS has a great potential in the fields of low RCS and wireless communication.
•Highly efficient ultra-wideband polarization converter for RCS reduction is designed.•The PCR exceeds 90% in the frequency range of 8.5–25.5 GHz with a FBW of 100%. .•RCS reduction of −10 dB is achieved in the frequency range of 6.9–25 GHz with a FBW of 114%.•The PCMS offers high efficiency, ultra-wide bandwidth, simple structure having a minimal thickness.
Summary
A two‐port multiple‐input‐multiple‐output (MIMO) antenna system operating in the mm‐wave band for 5G applications is presented. The two elements of MIMO structure are separated from each ...other by 19 mm (1.9
λ) and excited by microstrip feed. The MIMO elements are circular patches with round cuts at the edges to improve impedance bandwidth. Quadrilateral slot in the ground plane is designed to improve the radiation characteristics of the radiating element having size 18
×19× 0.8 mm3. The MIMO design is simulated through CST. The proposed antenna works in 27–29 GHz range, providing a potential bandwidth of 2 GHz. Furthermore a gain is improved from 8.2 to 8.75 dB and efficiency increase from 85% to 88% and high isolation of 64 dB is achieved by placing 4‐elements of metamaterial with size 4.5
× 18 mm2 in the middle of two circular monopole antennas. The metamaterial gives us a band stop response and act as decoupler and enhance the isolation to reduce mutual coupling. By analyzing the radiation characteristics of the proposed design, in term of reflection coefficient, surface currents, reduced mutual coupling, suitable gain, envelope correlation coefficient (ECC), diversity gain (DG) and radiation pattern, the recommended antenna can be considered a good candidate for 5G applications.
In this paper, a two‐port metamaterial‐based multiple‐input‐multiple‐output (MIMO) antenna system for 5G applications is presented. A metamaterial gives us a band stop response and act as a decoupler to enhance the isolation and reduce mutual coupling. The proposed antenna system is analyzed in terms of the radiation characteristics, reflection coefficient, surface currents, mutual coupling, gain, envelope correlation coefficient, and diversity gain. based on the above‐mentioned parameter the proposed antenna can be considered a suitable candidate for 5G applications.
In this paper, a triple-band polarization converting metasurface for
X
and
K
u
band applications is investigated. The unit cell consists of an asymmetric circular ring, terminated with a T-shaped ...stub, printed on FR-4 substrate, and backed by copper cladding. The triple-band polarization convertibility of the metasurface results from the proper engineering and anisotropy along the
x
- and
y
-axis. The metasurface has three plasmonic resonances with a polarization conversion ratio (PCR) of almost 100% in the lower two frequencies bands and 95% in the higher frequency band. The plasmonic resonances at 8.2 and 13.6 GHz are due to magnetic dipole moment while response at 19 GHz is due to electric dipole moment. Cross linear polarization conversion, linear to circular polarization conversion, and circular to circular polarization conversion are observed, both for normal and oblique wave incidences. Measured and simulation results are in good agreement with an excellent polarization conversion in three frequency bands, i.e., 7.7 to 9.2 GHz, 10.8 to 15.5 GHz, and 17.5 to 19.2 GHz. The polarization conversion response of the metasurface is same for both
x
- and
y
-polarized waves and is quite stable under oblique incidence of the impinging wave. The metasurface dominates the merits of multi-band resonances, angle sensitivity, and higher PCR, and thus has eminent values for application in polarization-control appliances.
An ultra-wideband and efficient single layer polarization converting metasurface based on an L-shaped resonator is presented. The metasurface is based on an F4B dielectric substrate with relative ...permittivity of 2.65 and a loss tangent of 0.002. The size of the unit cell is 0.132
λ
o
× 0.132
λ
o
and the thickness of the metasurface is 0.05
λ
o
, where
λ
o
is the largest wavelength (corresponding to the lower frequency) in the operation band of interest. The proposed structure effectively transforms the linearly or circularly polarized incident wave to its orthogonal equivalent, which is justified by both simulated and measured results where the polarization conversion ratio (PCR) is greater than 90% in the frequency range from 8.6 GHz to 22 GHz with a fractional bandwidth of 88%. The polarization transformation process is illustrated in depth by the surface current distribution. Simulation results reveal that ultra-wideband is achieved because of strong electric and magnetic dipole resonances on the upper and the lower layer of the metasurface. Furthermore, the bandwidth and central frequency can be efficiently adjusted over a wide spectrum by changing the geometric aspects of the unit cell, thereby retaining high transformation proficiency. The designed converter can be used in applications such as antenna design, radar invisibility, imaging, microwave communications, and remote sensing.
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