CMOS Power Amplifier Design Techniques for UWB Communication: A Review

This paper reviews CMOS power amplifier (PA) design techniques in favour of ultra-wideband (UWB) application. The PA circuit design is amongst the most difficult delegation in developing the UWB transmitter due to conditions that must be achieved, including high gain, good input and output matching, efficiency, linearity, low group delay and low power consumption. In order to meet these requirements, many researchers came up with different techniques. Among the techniques used are distributed amplifiers, resistive shunt feedback, RLC matching, shuntshunt feedback, inductive source degeneration, current reuse, shunt peaking, and stagger tuning. Therefore, problems and limitation of UWB CMOS PA and circuit topology are reviewed. A number of works on the UWB CMOS PA from the year 2004 to 2016 are reviewed in this paper. In recent developments, UWB CMOS PA are analysed, hence imparting a comparison of performance criteria based on several different topologies

Subtraction dual-wavelength for enhanced transmission performance of free-space optical communication over turbulence effect

Performance of a free-space optical communication system is influenced by atmospheric turbulence which degrades signal transmission quality. A gamma–gamma channel model is employed to characterise this turbulence under weak-to-strong conditions. The proposed dual diffuser modulation using subtraction dual-wavelength concept is combined with a phase screen diffuser to improve signal transmission. Its performances are compared with conventional intensity modulationdirect detection on off keying and partial coherent beam on off keying techniques. In comparison, results show that the dual diffuser modulation demonstrates superior performances in both received power and bit rate transmission under different turbulence conditions

Impact of Rain Attenuation in Borneo using Free Space Optics Propagation

In recent years, Free Space Optics (FSO) communication provides attractive bandwidth enhancement with unlicensed bands worldwide spectrum. However, the link capacity and availability are the major concern in the different atmospheric conditions. The reliability of the link is highly dependent on weather conditions that attenuate the signal strength. In the tropical region specifically in Borneo Sarawak, rain is the dominant weather that act as the limiting factor to FSO performance. Hence, this study highlights on the impact of rain attenuation to the performance of FSO communication system. The finding is based on atmospheric model and performed through the simulation of OptiSystem software. The design of parameters in the simulation involves iteration of wavelengths, size of transmitter and receiver aperture and beam divergence angle. The simulation result shows longer wavelength 1550nm is much better than 785nm. The 0.25m of receiver aperture and transmitter aperture at 0.05m can reduce the loss. Narrow beam divergence angle can reduce the power consumption and maintain the high power at receiver. The analysis indicates that proposed FSO communication system is capable to withstand the attenuation from rain weather

Performance Analysis of Double-MIMO Free Space Optical System under Atmospheric Turbulence

Over the last few years, free space optical communication (FSO) has emerged as a viable alternative to radio frequency communication. It provides a promising high-speed point�to-point communication solution. However, atmospheric absorption, scattering and turbulence degrade wireless optical communication significantly, lowering device efficiency. The attenuation of signals due to the above atmospheric reasons is another major factor that affects device efficiency. The atmospheric turbulence conditions are observed implemented into different models of FSO systems, such as Single Input Single Output (SISO), Multiple Input Multiple Output (MIMO), Wavelength Division Multiplexing MIMO (WDM-MIMO) and proposed model Double Multiple Input Multiple Output (DMIMO) using the Gamma-Gamma model for a variety of reasons. The OptiSystem 7.0 software was used to run simulations to study how various weather conditions (clear, haze and fog) affected the performance of the channel. Simulation results show that implementing Double Multiple Input Multiple Output (DMIMO) techniques for FSO systems provides high quality factor for various ranges while still achieving accurate transmitted data at the receiver side. In the presence of atmospheric turbulence conditions such as clear air, haze and fog, performance improvements signal power levels, quality factor and link distance range have been demonstrated

A Review of Highly Efficient Class F Power Amplifier Design Technique in Gigahertz Frequencies

Highly efficient class F power amplifier (PA) in Gigahertz (GHz) frequencies for wireless application is reviewed in this paper. The study focused on the technique used in designing a class F PA especially at GHz frequencies. Several works on the class F PA with different semiconductor technologies from year 2001 to 2016 are discussed. Recent works on class F PA in wireless applications are examined and a comparison of the PA performances of various techniques is presented. Key performance indicators for high efficiency class F PA include power added efficiency (PAE) and output power (Pout)

Effect of Substrate Orientation on the Growth of Germanium Oxide in Dry Oxygen Ambience

The present investigation deals with the effect of substrate orientation effect on the growth of thermally oxidized Ge. The thermal oxidation was performed at temperature between 375 and 550°C in dry oxygen ambient under atmospheric pressure. The thickness of thermally oxidized Ge films was measured by spectroscopic ellipsometry and the chemical bonding structures were characterized by using x-ray photoelectron spectroscopy (XPS). No orientation dependence was observed for the oxidation at temperature of 375°C while for oxidation at 490 and 550°C, Ge oxidation and GeO desorption rate of (100) orientation yield higher rate than (111). The larger atomic space of (100) orientation explains the higher oxidation and desorption rate at Ge surface

Surface Analysis of Thermally Growth Ge Oxide on Ge(100)

The understanding of Ge oxidation is utmost importance in order to form the good quality dielectric/Ge interface in fabricating Ge Metal Oxide Semiconductor Field Effect Transistor (MOSFETs). In addition, the mechanism of Ge oxidation is still under intensive studies. For Silicon oxidation, Deal and Grove Model have been accepted to explain the Si Oxidation mechanism. The purpose of this paper is to report the mechanism of Ge oxidation at two different temperatures, 375 and 490°C and the detail of Ge oxide composition at Ge oxide/Ge interface. After wet chemical cleaning with HCl, the thermal oxidation was performed at temperature 375 and 490°C at atmospheric pressure. The thickness and composition of Ge oxide were measured with spectroscopic ellipsometry and x-ray photoelectron spectroscopy, respectively. It was observed that the n value extracted from a log-log plot of oxidation time versus oxide thickness was dependent on the oxidation temperature. The oxygen-deficient region was formed during thermal oxidation of Ge and the electronic states of suboxide component were observed in the region within 2.3eV above the top valence band. The novelty of this work is to investigate the kinetics oxidation of Ge and evaluate the composition of oxide layer after thermal oxidation that becomes useful information for the development of Ge MOSFETs

Design of CMOS Power Amplifier with Resistive Feedback and Notch Filter for UWB Systems

A CMOS power amplifier (PA) with the implementation of the notch filter designed for ultra-wideband (UWB) systems is presented in this paper. The design is consisted of two stages of amplifier involving source follower and common source topologies with a notch filter and an output matching network. Such design is meant for full band UWB applications that utilize the frequency range within 3.1 GHz to 10.6 GHz with the elimination at 5-6 GHz using 0.18 µm CMOS process. The simulation shows that the proposed PA design achieved 19.25 dB maximum gain with 1.8 V power supply. In this work, the achieved input and output return loss ranging from -8.13 dB to -19.19 dB, and -1.68 dB to -16.03 dB, respectively, through full band frequency