Frequency Reconfigurable Antenna for Multi Standard Wireless and Mobile Communication Systems

In this paper,low profile frequency reconfigurable monopole antenna is designed on FR-4 substrate with a compact size of 30 mm^(3)×20 mm^(3)×1.6 mm^(3).The antenna is tuned to four different modes through three pin diode switches.In Mode 1(SW1 to SW3=OFF),antenna covers a wideband of 3.15–8.51 GHz.For Mode 2(SW1=ON,SW2 to SW3=OFF),the proposed antenna resonates at 3.5 GHz.The antenna shows dual band behavior and covers 2.6 and 6.4 GHz in Mode 3(SW1 and SW2=ON,SW3=OFF).The same antenna covers three different bands of 2.1,5 and 6.4 GHz when operating in Mode 4(SW1 to SW3=ON).The proposed antenna has good radiation efficiency ranges from 70%∼84%,providing adequate average gain of 2.05 dBi in mode 1,1.87 dBi in mode 2,1.4–1.75 dBi in mode 3 and 1.05–1.56 dBi in mode 4.The achieved impedance bandwidths at respective frequencies ranges from 240 to 5000 MHz.The Voltage Standing Waves Ratio(VSWR)of less than 1.5 is achieved for all operating bands.To validate the simulation results,the proposed antenna is fabricated and experimentally tested in antenna measurement laboratory.Due to its reasonably small size and support of multiple bands operation,the proposed antenna can be used in modern communication systems for supporting various applications such as fifth generation(5G)mobile and wireless local area networks(WLAN).

Surface-Induced Dissociation of Low Energy H_2^(+) Impact on a Carbon Surface: A Monte Carlo Simulation

A Monte Carlo simulation based on the classical binary collision approximation is performed to investigate the interaction of H_2^+ ions with the carbon target.The incident H_2^+ ion is characterized by its translational energy, eigenenergy and population of the vibrational state,and orientation of the ion with respect to the target surface.It is shown that experimentally determined energy resolved mass spectrum of H_2^+ can be nicely reproduced with the help of the proposed model.These simulations predict that translational to vibrational (T → V) energy transfer efficiency increases nonlinearly with translational energy of the incident ion.T → V energy transfer efficiency along with the initial vibrational energy of the incident H_2^+ ion found to play an important role in dissociation.Our simulations also show that the fraction of absorbed,reflected,and dissociated ions depends on the translational energy.The average vibrational energy of reflected H_2^+ increases with its initial translational energy.Moreover,average number of collisions required for dissociation varies inversely with the initial translational energy of the H_2^+.

A Compact Flexible Circularly Polarized Implantable Antenna for Biotelemetry Applications

With the help of in-body antennas,the wireless communication among the implantable medical devices(IMDs)and exterior monitoring equipment,the telemetry system has brought us many benefits.Thus,a very thin-profile circularly polarized(CP)in-body antenna,functioning in ISM band at 2.45 GHz,is proposed.A tapered coplanar waveguide(CPW)method is used to excite the antenna.The radiator contains a pentagonal shape with five horizontal slits inside to obtain a circular polarization behavior.A bendable Roger Duroid RT5880 material(εr=2.2,tanδ=0.0009)with a typical 0.25 mm-thickness is used as a substrate.The proposed antenna has a total volume of 21×13×0.25 mm3.The antenna covers up a bandwidth of 2.38 to 2.53 GHz(150 MHz)in vacuum,while in skin tissue it covers 1.56 to 2.72 GHz(1.16 GHz)and in the muscle tissue covers 2.16 to 3.17 GHz(1.01 GHz).GHz).The flexion analysis in the x and y axes was also performed in simulation as the proposed antenna works with a wider bandwidth in the skin and muscle tissue.The simulation and the curved antenna measurements turned out to be in good agreement.The impedance bandwidth of−10 dB and the axis ratio bandwidth of 3 dB(AR)are measured on the skin and imitative gel of the pig at 27.78%and 35.5%,13.5%and 4.9%,respectively,at a frequency of 2.45 GHz.The simulations revealed that the specific absorption rate(SAR)in the skin is 0.634 and 0.914 W/kg in muscle on 1g-tissue.The recommended SAR values are below the limits set by the federal communications commission(FCC).Finally,the proposed low-profile implantable antenna has achieved very compact size,flexibility,lower SAR values,high gain,higher impedance and axis ratio bandwidths in the skin and muscle tissues of the human body.This antenna is smaller in size and a good applicant for application in medical implants.

Frequency Reconfigurable Antenna for Portable Wireless Applications

In this paper,the design and experimental evaluation of a hexagonalshaped coplanar waveguide(CPW)-feed frequency reconfigurable antenna is presented using flame retardant(FR)-4 substrate with size of 37×35×1.6 mm3.The antenna is made tunable to three different modes through the status of two pin diodes to operate in four distinct frequency bands,i.e.,2.45 GHz wireless fidelity(Wi-Fi)in MODE 1,3.3 GHz(5G sub-6 GHz band)in MODE 2,2.1 GHz(3G Long Term Evolution(LTE)-advanced)and 3.50 GHz Worldwide Interoperability for Microwave Access(WiMAX)in MODE 3.The optimization through simulation modeling shows that the proposed antenna can provide adequate gain(1.44∼2.2 dB),sufficient bandwidth(200∼920 MHz)and high radiation efficiency(80%∼95%)in the four resonating frequency bands.Voltage standing wave ratio(VSWR)<1.5 is achieved for all bands with properly matched characteristics of the antenna.To validate the simulation results,fabrication of the proposed optimized design is performed,and experimental analysis is found to be in a considerable amount of agreement.Due to its reasonably small size and support of multiple frequency bands operation,the proposed antenna can support portable devices for handheld 5G and Wireless LAN(WLAN)applications.

Effect of OH^- on fluorescence properties in 1.5-1.6 μm for Er:Yb:YCOB crystal

FTIR absorption spectra indicate that H^+can easily enter the crystal structure and form OH^-centers in Er:Yb:YCOB and O-H bonds prefer to lie in the a-c plane.Within our current studied concentration level,crystal samples with higher OH-abso rption coefficie nts demonstrate stro nger fluo rescence intensity and longer fluorescence lifetime at 1535 nm.As the stretching vibration energy of OH-group approximately corresponds to the energy gap between the 4 I11/2 and 4 I13/2 levels of Er^3+,and thus,OH^-ions can shorten the fluorescence lifetime of Er^3+-4I11/2 level by the phonon-assisted cross-relaxation process between the Er^3+and OH-ions.Our curre nt results confirm that a certain conte nt of OH ions can enhance the ene rgy transfer process from Yb^3+to Er^3+and subsequently promote fluorescence output in 1.5-1.6μm.