Volume 76, Issue 7-8

TV White space has the potential to extend internet connection to remote areas worldwide. In this paper, a dual-band frequency reconfigurable microstrip patch antenna has been designed for TV white space applications. Switching between the frequencies (reconfiguration) has been achieved by introducing a switch between two radiating strips on the top surface of the substrate. The prototype has been designed and fabricated on a cost-effective FR-4 substrate ( εr  = 4.4, tan δ  = 0.02) with an overall dimension of 30 × 261 × 0.8 mm 3 . ON and OFF condition of the switch provides two operating frequency bands namely 626.7–778.11 MHz and 461.5–549.7 MHz The proposed monopole TV white space antenna operates with a peak gain of 2 dB with an efficiency greater than 85% in both the bands. The simulated and measured parameters are well-matched in both the operating bands along with desired radiation patterns suitable for TV white space applications.

This paper presents a triple-band planar antenna with diverse radiation patterns. The proposed planar antenna is a modified swastika shape with three fingers and the ground plane is a circle with rectangular slots etched on four sides radially. The slotted ground plane is loaded with Four PIN diodes to realign the surface current. Pattern reconfigurability is achieved at the triple bands by changing the states of the diode. The antenna operates in triple bands centered at 2.2, 2.9 and 3.5 GHz. The antenna is printed on FR4 Epoxy substrate. The simulated reflection coefficient is well below −10dB at resonant frequencies. The measured patterns and return loss are in very close agreement with the simulated results. This antenna can find potential applications in 5G systems.

This paper proposes a novel metal-graphene plasmonic antenna over a Si/SiO 2 substrate, working in terahertz frequency band. Novelty of the work lies in the use of metal and graphene as a patch antenna, as this combination enhances the gain & the radiation efficiency of the whole structure. Besides the analysis provides detailing of graphene and its conductivity modelling using MATLAB. The antenna is analyzed using FDTD based CST software, conductivity of graphene used in CST is verified with the conductivity achieved using MATLAB. Further, a 3-element Multiple Input and Multiple Output (MIMO) antenna system using same single element antenna, is designed & analyzed. The metal-graphene hybrid patch antenna provides maximum directivity around 5.8 dBi, maximum gain around 5 dBi, and high radiation efficiency (approx. 80%) at resonant frequency of 1.8 THz. Besides, the 3-element MIMO antenna provides radiation efficiency around 77%, with directivity around 5 dB & diversity gain of around 10 dBi. The proposed metal-graphene hybrid MIMO patch antenna has the potential to be used in advanced THz communication systems.

In this article, a microstrip antenna having circular polarization switching capability is presented. This antenna consists of a circular-shaped radiating patch with a single co-axial probe feed line. The polarization reconfigurability is achieved by introducing four symmetrical U-shaped slots and silicon PIN diodes on the radiating patch. A prototype of the design is fabricated on an FR-4 substrate with overall dimension of 70 × 70 × 1.6 mm to verify the performances. The measured results of the antenna exhibit an impedance bandwidth ( S 11  < −10 dB) of 5% in the frequency range of 2.37–2.49 GHz. The maximum gain of the antenna is found to be 2.99 dBic at 2.43 GHz. The antenna shows stable radiation performances at 2.4 GHz with 4.1% of 3-dB axial ratio bandwidth, and more than 105° of 3-dB axial ratio beamwidth for both right-hand circular polarization and left -hand circular polarization which make it suitable for ISM band Smart city applications.

In this work, metamaterial (MTM) inspired a compact CPW-fed antenna with triple operating band is proposed. A rectangular Split Ring Resonator (SRR) is unified in a circular slot of the polygon-shaped radiator in MTM inspired antenna. The antenna exhibits three operating band which are based on metamaterial characteristics of unit cell. The CPW-fed antenna is ensuing 10 dB impedance bandwidth varies from 2.28 to 2.38 GHz, 3.07 to 3.78 GHz, and 5.05 to 7.03 GHz, whereas notch band exist from 2.39 to 3.06 GHz frequency. Metamaterial behaviour leads into the bandwidth enhancement as well as miniaturization in lower operating band with electric length of 0.14 λ 0  × 0.21 λ 0 . The antenna archives the peak gain of 1.49 dB at 2.34 GHz, 2.04 dB at 3.32 GHz, and 4.14 dB at 6.5 GHz frequency. The measured results authenticate the simulated outcomes and consequently the proposed antenna can be pertinent in LTE, WLAN, and 5G communications.

In this article, a single feed antenna design which consists of a parasitic patch slot with an I-tree shaped fractal defected ground structure for circularly polarized radiation is presented. In the proposed design, circular polarization characteristics are achieved by deploying fractal slotted defected ground structures. The antenna design with a third iterative I-tree shaped fractal slot on an Fr4 substrate is fabricated and tested for verifying the simulated results. The circular polarization mechanism is performed using parametric studies. The measured and simulated results confirmed that the proposed structure can adequately generate an impedance bandwidth of 10.6% with 3 dB axial ratio bandwidth of 4.89%, with the measured peak gain of the proposed antenna being 5.16 dBic. The proposed article is suitable for C-band and CA-band applications.

In this letter, a differential driven shorted annular-ring microstrip antenna is presented. The antenna configuration, operation theory and parametric studies are described. Finally, an exemplary antenna is designed, simulated, fabricated and tested to verify the theoretical prediction. The fabricated antenna exhibits many good performances including wider impedance bandwidth, lower backward radiation and direct connection with other differential components.

This paper is focused on providing a viable solution to wearable antenna performance disconcertment caused by the underlying human body. Direct placement of the antenna on the body yields undesired results owing to the frequency detuning effect. The simplest possible way out is to make use of a metallic reflector. Hence, a reflector backed antenna is presented for 5.8 GHz ISM band with total lateral dimensions of 28 × 28   × 13.58 mm 3 . The reflector makes use of a conformal high dielectric laminate coated with a thin copper layer owing to which the assembled design achieves low SAR (Specific Absorption Rate). The prototype provides excellent results at the cost of some extra volume occupation in an off-body direction. Another AMC (Artificial Magnetic Conductor) backed technique is followed and implemented separately to have the structural compactness lacking in the former case. The antenna at hand is backed by a 2 × 2 array of AMC unit cells. The overall design dimensions are reduced. The reflector backed design achieves 8.2 dB gain, above 90% efficiency, and 99% bandwidth overlap with the primary antenna. The AMC backed design provides good spectrum coverage from 5.73 to 5.94 GHz with high gain. Free space response, on-body performance, and investigation of SAR analysis of the proposed designs substantiate effective wireless data transfer in body-centric communication.

In this paper, a novel multilayer microstrip implant antenna (MIA) design based on the Archimedean spiral (AS) radiator element is presented for dual-band biotelemetric health care monitoring system. The proposed AS-MIA design has a layered structure consists of the spiral antenna elements and superstrate, namely layer #1 , layer #2 and layer #3 , respectively. While achieving the dual-band multi-layer implantable antenna design, firstly, each of the radiating elements in the respective layers is designed to cover separately in the desired bands, that is, layer #1 and layer #2 operate in the ISM (Industrial, Scientific, and Medical 2.4–2.48 GHz) and MICS (Medical Implant Communication Services 402–405 MHz) bands, respectively. Subsequently the ultimate multilayered AS-MIA design is formed by combining the individually designed layers. The compact implantable antenna has a dimension of r  = 5 mm radius and h  = 3.81 mm height, owning the electrically size of 0.067  λ 0 and h  = 0.051  λ 0 , respectively, where λ 0 is free space wavelength at 402 MHz in MICS band. Since the AS-MIA is intended to be used in an intra-arm smart health system, the simulated radiation performances of the antenna in a created numerical arm phantom are presented in the article. Also note that numerical analysis of the implant antenna was carried out using CST MW studio simulator based on finite integral method. The prototype of the implantable antenna was fabricated using Rogers 3210 substrate with electrical permittivity of ε r  = 10.2. In-vitro return loss measurements were realized in skin mimicking gels, suggested in the literature. It was observed that in vitro measurement and simulation results were quite compatible with each other, except for some discrepancies due to the manufacturing and material tolerances during the preparation of the prototype antenna and skin mimicking gels. The proposed AS-MIA offers a dual-band operation with 15 and 16% S 11 bandwidth at each band of 402 MHz and 2.4 GHz respectively where | S 11 | ≤ 10 dB criterion along with 50-Ω system is considered. Also the proposed design can be a good candidate to be used in dual-band medical implant communication systems with its miniature size and reasonable radiation characteristics.

This paper presents a miniaturized multi-band frequency selective surface for band-stop applications. The proposed design is evolved from a modified swastik structure with L-shaped arms printed on FR4 substrate. The structure is designed to operate at 2.4, 5.8, 8.6, and 10.8 GHz covering Wifi, WiMAX, and X-band applications. The proposed quad-band FSS has an overall unit cell size of 0.084 λ 0  × 0.084 λ 0 , where λ 0 is the wavelength of the lower operational frequency. The symmetric FSS structure provides the advantage of polarization independency. It also exhibits a stable frequency response up to 60° for both the horizontally polarized EM waves (Transverse Magnetic Mode) and the vertically polarized EM waves (Transverse Electric Mode). Moreover, measurement results obtained from the fabricated prototype are compared with the simulation results and are found to be in close agreement with each other. Single layer structure, compact, and coverage of multiple applications are the advantages of the proposed multiband FSS.

Ultra thin wideband metasurface polarization converter is presented in this paper. The proposed structure is used for linear conversion i.e., X polarized to Y polarized and vice versa. The design of the structure consists of stair case shaped and is fabricated on FR-4 substrate having overall dimension of 3 mm × 3 mm. The Polarization Conversion Ratio (PCR) obtained is wideband having bandwidth of 10.81 GHz (10.57–21.38 GHz) above 89%. Two distinct peaks are observed in the range of interest having frequencies at 11.66 and 18.13 GHz with maximum magnitude of 99.30 and 99.90%. These two peaks occur due to plasmonic resonance. At these two peaks, surface current distribution is plotted to explain the wideband response from the structure. The structure is simulated using commercially available ANSYS HFSS 19.1 and measured inside an anechoic chamber with the help of Vector Network Analyser (VNA). The proposed structure find applications for X (8–12 GHz), Ku (18–21 GHz) and K (21–27 GHz) band. At last the structure is measured with already reported polarization converters and find practical applications for frequency reconfigurable antennas, linearly conversion of incident waves, etc.

In the past decades, photonic integrated circuits have been considered to overcome the bandwidth limitations of electronics circuits. However, photonic devices have yet to offer the same reconfigurability and programmability available in their electronics counterpart. This challenge can be addressed by integrating phase-change materials such as Ge 2 Sb 2 Te 5 (GST) into photonic devices. We inserted a periodic arrangement of GST in a subwavelength grating (SWG) slot waveguide in order to have an optical filter with Bragg grating. The non-volatile and reversible phase-transition of GST, embedded in the silicon SWG slot waveguide, enables us to design a reconfigurable notch filter without static power consumption. The three-dimensional finite-difference time-domain (3D FDTD) simulation confirms that it is possible to create a 6.1 nm blueshift at the middle of the passband only by changing and controlling the phase transition of the GST. The spectral characteristics and their dependences on the geometrical parameters are investigated. The comparison of our filter with a conventional slot waveguide clearly indicates that the SWG slot waveguide provides a larger wavelength shift upon phase-transition of GST. Moreover, the SWG structure greatly improves the extinction ratio of the notch filter.