ABSTRACT
Millimeter wave (mm-Wave) wireless communication systems require high gain antennas to overcome path loss effects and thereby enhance system coverage. This paper presents the design and analysis of an antenna array for high gain performance of future mm-wave 5G communication systems. The proposed antenna is based on planar microstrip technology and fabricated on 0.254 mm thick dielectric substrate (Rogers-5880) having a relative permittivity of 2.2 and loss tangent of 0.0009. The single radiating element used to construct the antenna array is a microstrip patch that has a configuration resembling a two-pronged fork. The single radiator has a realized gain of 7.6 dBi. To achieve the gain required by 5G base stations, a 64-element array antenna design is proposed which has a bore side gain of 21.2 dBi at 37.2 GHz. The 8 × 8, 8 × 16, and 8 × 32 antenna array designs described here were simulated and optimized using CST Microwave Studio, which is a 3D full-wave electromagnetic solver. The overall characteristics of the array in terms of reflection-coefficient and radiation patterns makes the proposed design suitable for mm-Wave 5G and other communication systems.
ABSTRACT
InP based HEMTs are of great importance, due to their enormous potential in a high-speed modern microwave circuit, power amplifier, and low noise amplifier applications. Therefore, an accurate non-linear equivalent circuit model of HEMTs is very important for an accurate circuit design. This paper presents improved characterization and accurate modelling of drain current derivatives of InP based HEMTs devices. The proposed model is simple, easy to extract, and suitable for implementation in simulation tools. The Ψ function is extended to increase the flexibility of the proposed model. A gate-drain dependent current source is added to increase the S-parameter fitting. A one-dimensional intrinsic multi-bias capacitances model is introduced to avoid convergence failure. The fitting results of the I-V characteristics and its high order derivatives show high accuracy. In addition, S-parameters and Pout for the proposed model are compared with the original Angelov model. The proposed model shows better accuracy.
ABSTRACT
This paper analyses, the influence of Si3N4-PECVD and Al2O3-ALD surface passivation on the DC and RF characteristics of InP HEMTs with different gate lengths 0.08 µm, 0.1 µm, 0.12 µm, and 0.15 µm. A significant improvement in maximum drain current IDS, MAX, transconductance gm, MAX and oscillation frequency fmax, MAX is obtained by scaling the thickness of the passivation layers An increase in gm, MAX and fmax, MAX, fT, MAX is observed by reducing parasitic capacitance w.r.t. the decrease in gate length. In addition, an analytical model of fT based on a small-signal equivalent circuit is developed, which consist of extrinsic parameters Rs, Rd, Cgs_ext and Cgd_ext and intrinsic parameters Cgsi, Cgdi, gmi and goi. The carrier transport is improved by increasing gmi, thus the transit time τt , the parasitic charging delay τext and the τpar are reduced by lowering the extrinsic capacitances. An excellent fitting between measured and simulated fT is achieved, which inturn leads a realistic way for further improvement in fT.
ABSTRACT
This study was planned to examine the hard and soft form of learning resources available on the internet accessed by the teaching faculty. This study was conducted at the Peshawar Medical College, Peshawar, Pakistan from January 2to April 2017. As the target population was not too large, no sampling technique was employed and census-based approach was adopted. For data collection, the pre-tested questionnaire was distributed among 115 faculty members of both basic and clinical sciences groups with a response rate of 66(57.39%). Data was analysed using SPSS. Among the respondents, 38(57.6%) were males and 28(42.4%) were females. A majority 51 (77.27%) of the respondents used the internet for teaching and research. Library was the most frequently 22 (33.33%) used place for the internet use. Low internet speed, virus on computers and a lack of modern trainings were the major barriers. E-journals, e-books, online databases and theses and dissertations were the major sources consulted by the participants.
