Mohd Najib Mohd Yasin

A review of LNA topologies for wireless applications

This paper presents the reviews of few previous works for low noise amplifier design (LNA). This paper will explore several recent architectures of LNA but focused on four techniques of topologies which are forward body bias, self-biased inverter, common source cascade and cascode technique. Those architectures are able to minimize power consumed in a typical CMOS for wireless sensor network (WSN). Besides, high gain, low noise, input and output matching are also reviewed. As to provide extremely low power and also optimized all characteristics aspects, the performance for each topologies then are discussed. Further research will be conducted based on these four topologies comparisons in order to design a new successful LNA.

1.575 GHz Circular Polarization wearable antenna with three different substrate materials

This paper presents an analysis of a Left-Handed Circular Polarization (LHCP) wearable antenna with different textile material (substrates) for Global Positioning System (GPS) application. The proposed antennas have achieved circular polarization (CP) by truncating two opposite edged of the square patch for all designed antennas with three different substrates. The analysis is focusing on using felt, jeans and cotton as substrates while maintaining shieldit supper as a conductor. The performance comparison have been made on the simulated reflection coefficient (S11), axial ratio (AR), bandwidth and gain. The results show that jeans fabric attained a better reflection coefficient of -41.36 dB at 1.575 GHz as compared to the other materials. Besides, the jeans has achieved good AR bandwidth of 17 MHz, followed by felt with AR bandwidth of 16 MH and cotton with AR bandwidth of 13 MHz.

The cadmium sulfide light emitting diodes die performance based on different structures

In this paper, cadmium sulfide (CdS) light emitting diodes (LED) die performance based on different structures configuration are simulated and investigated. The CdS LED extensively play an essential role in many applications, especially for the light sensor. The CdS LED die involves in this study are 10 μm height cylindrical circular, 9μm height dome-shaped, 10 μm height dome-shaped and 11 μm height dome-shaped structures. Increasing the height of the dome slightly changes the doping concentration and its ratio. Changes in the ratio of p-type and n-type affect the process recombination of electrons and holes. Thus, this produce high emission rate and optimum biased voltage. For the 10 μm height cylindrical circular structure, the threshold voltage of 1.95 V is recorded. Meanwhile, the 9μm height of domeshaped, 10μm height of dome-shaped and 11μm height of dome-shaped, the minimum voltage required to turn on the devices are 1.95 V, 1.96 V, and 1.975 V, respectively. It was found that dome-shaped with 11μm height generated the highest total emission rate for LED efficiency compared to other structures.

Comparison of rectifier performance using different matching technique

This paper describes the design and implementation of the 4-stage Villard multiplier for RF energy harvesting. Each stage is a combination of two HSMS 2850 Schottky diodes and two capacitors for each stage. For ambient energy harvesting, the incident power is extremely small, thus an efficient rectifier is needed. The designed rectifier with the matching circuit is a good candidate since it is able to enhance the rectified output power up to 300% during -40dBm input power compared to the rectifier circuit alone.

Investigation of transmission performance between antennas with textile Artificial Magnetic Conductor jacket on male and female subjects

This work investigates the transmission performance of on-body antennas with the proposed textile Artificial Magnetic Conductor (AMC) waveguide jacket. On-body measurements have been performed on male and female subjects to compare the S21 transmission of the antennas when positioned on top of the AMC sheet. The on-body transmission performance of the antennas when positioned on top of the AMC jacket exhibit good agreement for both male and female subjects. S21 peaks are obtained at 2.45GHz resonant frequency for all the measurements on the male and female subjects. With the introduction of the AMC waveguide sheet, the transmission performance between the antennas was enhanced. Results proved that the proposed AMC sheet works well on both male and female bodies; and its performance is independent of body type as well as the orientation and position of the antennas.

Circular Polarization Textile Antenna for GPS Application

A right-handed circular polarization (RHCP) textile antenna for Global Positioning System (GPS) application is proposed. The circular polarization (CP) is achieved by truncated two opposite edged of the 84 mm square patch. The proposed antenna design use a shieldit super as the radiator and felt fabric as substrates. Such presented antenna attains a good bandwidth of 90 MHz from 1.53–1.62 GHz. Besides, the antenna is capable to perform an axial ratio of less than <3 between 1.56 and 1.62 GHz which covered the GPS operating frequency of 1.575 GHz. Moreover, this paper discussed the parametric study of the truncated patch in order to achieve CP. The simulated result shows that the presented antenna is potential for point-to-point wireless communication system.