High-Gain On-Chip Antenna Design on Silicon Layer with Aperture Excitation for Terahertz Applications

This letter investigates the feasibility of designing a high gain on-chip antenna on silicon technology for subterahertz applications over a wide-frequency range. High gain is achieved by exciting the antenna using an aperture fed mechanism to couple electromagnetics energy froma metal slot line, which is sandwiched between the silicon and polycarbonate substrates, to a 15-element array comprising circular and rectangular radiation patches fabricated on the top surface of the polycarbonate layer. An open ended microstrip line, which is orthogonal to the metal slot-line, is implemented on the underside of the silicon substrate. When the open ended microstrip line is excited it couples the signal to the metal slot-line which is subsequently coupled and radiated by the patch array. Measured results show the proposed on-chip antenna exhibits a reflection coefficient of less than -10 dB across 0.290-0.316 THz with a highest gain and radiation efficiency of 11.71 dBi and 70.8%, respectively, occurred at 0.3 THz. The antenna has a narrow stopband between 0.292 and 0.294 THz. The physical size of the presented subterahertz on-chip antenna is 20 x 3.5 x 0.126 mm(3)

Financing micro-entrepreneurs for poverty alleviation: a performance analysis of microfinance services offered by BRAC, ASA, and Proshika from Bangladesh

Microfinance services have emerged as an effective tool for financing microentrepreneurs to alleviate poverty. Since the 1970s, development theorists have considered non-governmental microfinance institutions (MFIs) as the leading practitioners of sustainable development through financing micro-entrepreneurial activities. This study evaluates the impact of micro-finance services provided by MFIs on poverty alleviation. In this vein, we examine whether microfinance services contribute to poverty alleviation, and also identify bottlenecks in micro-finance programs and operations. The results indicate that the micro-loans have a statistically significant positive impact on the poverty alleviation index and consequently improve the living standard of borrowers by increasing their level of income

Disordered protein-graphene oxide co-assembly and supramolecular biofabrication of functional fluidic devices

Supramolecular chemistry offers an exciting opportunity to assemble materials with molecular precision. However, there remains an unmet need to turn molecular self-assembly into functional materials and devices. Harnessing the inherent properties of both disordered proteins and graphene oxide (GO), we report a disordered protein-GO co-assembling system that through a diffusion-reaction process and disorder-to-order transitions generates hierarchically organized materials that exhibit high stability and access to non-equilibrium on demand. We use experimental approaches and molecular dynamics simulations to describe the underlying molecular mechanism of formation and establish key rules for its design and regulation. Through rapid prototyping techniques, we demonstrate the system's capacity to be controlled with spatio-temporal precision into well-defined capillary-like fluidic microstructures with a high level of biocompatibility and, importantly, the capacity to withstand flow. Our study presents an innovative approach to transform rational supramolecular design into functional engineering with potential widespread use in microfluidic systems and organ-on-a-chip platforms

Circular polarized transparent antenna for 5.8 GHz WLAN applications

© 2015, Electromagnetics Academy. All Rights Reserved.A novel design for a transparent circularly polarized circular slot antenna fed by a coplanar waveguide (CPW) is presented in this paper. The circular polarization is achieved by introducing a tapered split gap in the ring patch of the circular slot antenna in combination with unequal CPW ground arms. The antenna is designed using AgHT-4 laminated on a 2mm thick glass with a relative permittivity of 7. The proposed antenna is designed to operate at 5.8 GHz for WLAN applications. The tapered split gap and inequality in the lengths of the CPW ground arms contribute to a 3 dB axial ratio bandwidth from 5.4 to 6.2GHz. The proposed antenna has been studied theoretically and fabricated. The measured results show that the proposed antenna has a gain of 0.92 dB at 5.8 GHz. Reflection coefficient (S11), axial ratio (AR), and radiation patterns are presented and briefly discussed

A wideband frequency reconfigurable rectangular dielectric resonator antenna

A wideband frequency reconfigurable dielectric resonator antenna (DRA) is presented and discussed. The proposed antenna is capable of frequency switching at two different bands between 4.12 GHz and 8.85 GHz. The rectangular dielectric resonator with a permittivity of 15 is fed by U-shaped microstrip feed line. By setting the switch on the connecting lines of a network that feeds the dielectric element and changing the state of switch from ON to OFF, a shift of the well-matched operating frequency range is obtained. The total antenna dimensions are 40 × 45 × 4.5748 mm3. The results indicate that the proposed antenna with acceptable performance provides two wideband modes with the impedance bandwidth of 49% and 25%

A C-shaped dielectric resonator antenna with frequency reconfigurable for ISM and LTE band applications

A frequency tunable dielectric resonator antenna (DRA) is studied and presented for ISM and LTE band applications. Here, the frequency operation of the proposed DRA is switched from dual band to narrowband mode by using the PIN diode switches. The switches are employed by RF PIN diodes and placed on the feed line network to excite the dielectric resonator (DR). The proposed reconfigurable DRA has a compact size with a thickness of 3 mm and the overall size of 30 × 37 mm2 that is proper for mobile devices. The measured and simulated results indicate that the proposed DRA provides a single and dual band modes which covers the ISM applications and 2.6 GHz LTE system, respectively

Path loss model and root mean square delay spread characterization of near-ground outdoor UWB channel

The large bandwidth of ultra wideband (UWB) makes it attractive in high speed transmission applications. However, the possibility of frequency selectivity of the channel is high due to this bandwidth. Channel characterization is important to study the behavior of the channel. The ground reflection effects are important parameters affecting the ultra wideband channel. In this paper, based on outdoor time domain measurements, path loss model and root mean square (RMS) delay spread characteristics for near-ground (NG) UWB channel have been presented. Moreover, the interdependencies of these characteristics of the multipath channel are also investigated. The NG UWB channel characteristics are compared to the UWB channel above the ground. From the results it has been found that the path loss in NG UWB channel is less as compared to the above ground case. Also, the values of RMS delay spread are low