Energy efficient radio frequency system design for mobile WiMax applications. Modelling, optimisation and measurement of radio frequency power amplifier covering WiMax bandwidth based on the combination of class AB, class B, and C operations.

In today´s digital world, information and communication technology accounts for 3% and 2% of the global power consumption and CO2 emissions respectively. This alarming figure is on an upward trend, as future telecommunications systems and handsets will become even more power hungry since new services with higher bandwidth requirements emerge as part of the so called ¿future internet¿ paradigm. In addition, the mobile handset industry is tightly coupled to the consumer need for more sophisticated handsets with greater battery lifetime. If we cannot make any significant step to reducing the energy gap between the power hungry requirements of future handsets, and what battery technology can deliver, then market penetration for 4G handsets can be at risk. Therefore, energy conservation must be a design objective at the forefront of any system design from the network layer, to the physical and the microelectronic counterparts. In fact, the energy distribution of a handset device is dominated by the energy consumption of the RF hardware, and in particular the power amplifier design. Power amplifier design is a traditional topic that addresses the design challenge of how to obtain a trade-off between linearity and efficiency in order to avoid the introduction of signal distortion, whilst making best use of the available power resources for amplification. However, the present work goes beyond this by investigating a new line of amplifiers that address the green initiatives, namely green power amplifiers. This research work explores how to use the Doherty technique to promote efficiency enhancement and thus energy saving. Five different topologies of RF power amplifiers have been designed with custom-made signal splitters. The design core of the Doherty technique is based on the combination of a class B, class AB and a class C power amplifier working in synergy; which includes 90-degree 2-way power splitter at the input, quarter wavelength transformer at the output, and a new output power combiner. The frequency range for the amplifiers was designed to operate in the 3.4 - 3.6 GHz frequency band of Europe mobile WiMAX. The experimental results show that 30dBm output power can be achieved with 67% power added efficiency (PAE) for the user terminal, and 45dBm with 66% power added efficiency (PAE) for base stations which marks a 14% and 11% respective improvement over current stateof- the-art, while meeting the power output requirements for mobile WiMAX applications

Approach Towards Energy Efficient Power Amplifier for 4G Communications.

yesThe biggest challenge for future 4G systems is the need to limit the energy consumptions of battery-powered and base station devices, with the aim to prolong their operational time and avoid active cooling in the base station. The green wireless communications requires research in areas such as energy efficient RF front end, MAC protocol, networking, deployment, operation, and also the integration of base station with renewable power supply. In this paper, the design concept of energy efficient RF front end is considered in terms of RF power amplifiers at which it represents the workhorse of modern wireless communication systems and inherently nonlinear. The approach of output power back off is to amplify the signal at the linear region to avoid distortion, but this approach suffers from significant reduction in efficiency and power output. To boost the efficiency at wide range of output power and keep the same margin for signal with high crest factor, the load modulation technique with new offset line are employed to operate over the frequency range of 3.4GHz to 3.6GHz band. The performances of load modulation power amplifier are compared with balanced amplifier. The results of 42dBm output power and 62% power added efficiency are achieved

Design of Energy Efficient Power Amplifier for 4G User Terminals.

yesThis paper describes the characterization and design of energy efficient user terminal transceiver power amplifier. To reduce the design of bulky external circuitry, the load modulation technique is employed. The design core is based on the combination of Class B and Class C that includes quarter wavelength transformer at the output to perform the load modulation. The handset transceiver for this power amplifier is designed to operate over the frequency range of 3.4GHz to 3.6GHz mobile WiMAX band. The performances of the load modulation amplifier are compared with conventional Class B amplifier. The results of 30dBm output power and 53% power added efficiency are achieved

Design of Power Efficient Power Amplifier for B3G Base Stations.

yesFourth generation systems require the use of both amplitude and phase modulation to efficiently utilize the available spectrum and to obtain high data rates, hence imposing stringent requirements on the power amplifier in terms of efficiency and linearity and requires the power amplifier to operate linearly and efficiently. The B3G base station transceiver Doherty power amplifier was designed to operate over the frequency range of 3.47GHz to 3.53GHz mobile WiMAX band using Freescale¿s N-Channel Enhancement-Mode Lateral MOSFET Transistor, MRF7S38010HR3; The performances of the Doherty amplifier are compared with that of the conventional Class AB amplifier. The results of 43 dBm output power and 66% power added efficiency are achieved

Green Wireless Internet Technology

YesIET Editorial: In the future communications will be pervasive in nature, allowing users access at the “touch of button” to attain any service, at any time, on any device. The future device design process requires both a reconfigurable RF front end and back end with high tuning speed, energy efficiency, excellent linearity and intelligence to maximise the “greenness” of the network. But energy efficiency and excellent linearity are the main topics that are driving the designs of future transceivers, including their efforts to minimise network contributions to climate changes such as the effect of CO2 emissions: the minimisation of these is a requirement for information and communication technology (ICT) as much as for other technologies. Recently, information and communication technologies were shown to account for 3% of global power consumption and 2% of global CO2 emissions, and hence far from insignificant. The approach towards energy conservation and CO2 reduction in future communications will require a gret deal of effort which should be targeted both at the design of energy efficient, low-complexity physical, MAC and network layers, while maintaining the required Quality of Service (QoS). There is also a need, in infrastructures, networks and user terminals, to take a more holistic approach to improving or achieving green communications, from radio operation, through functionality, up to implementation. The increasing demand for data and voice services is not the only cause for concern since energy management and conservation are now at the forefront of the political agenda. The vision of Europe 2020 is to become a smart, sustainable and inclusive economy, and as part of these priorities the EU have set forth the 20:20:20 targets, whereby greenhouse gas emissions and energy consumption should be reduced by 20% while energy from renewables should be increased by 20%

Optimum Design of Doherty RFPA for Mobile WiMAX Base Stations

YesRF power amplifiers in mobile WiMAX transceivers operate in an inherently nonlinear manner. It is possible to amplify the signal in the linear region, and avoid distortion, using output power back-off; however, this approach may suffer significant reduction in efficiency and power output. This paper investigates the use of Doherty techniques instead of back-off, to simultaneously achieve good efficiency and acceptable linearity. A 3.5 GHz Doherty RFPA has been designed and optimized using a large signal model simulation of the active device, and performance analysis under different drive levels. However, the Doherty EVM is generally poor for mobile WiMAX. Linearity may be improved by further digital pre-distortion, and a simple pre-distortion method using forward and reverse AM-AM and AM-PM modeling. Measurements on the realized amplifier show that this approach satisfies the EVM requirements for WiMAX base stations. It exhibits a PAE over 60%, and increases the maximum linear output power to 43 dBm, whilst improving the EVM

Multi-Antenna OFDM System Using Coded Wavelet with Weighted Beamforming

yesA major drawback in deploying beamforming scheme in orthogonal frequency division multiplexing (OFDM) is to obtain the optimal weights that are associated with information beams. Two beam weighting methods, namely co-phasing and singular vector decomposition (SVD), are considered to maximize the signal beams for such beamforming scheme. Initially the system performance with and without interleaving is investigated using coded fast Fourier transform (FFT)-OFDM and wavelet-based OFDM. The two beamforming schemes are applied to the wavelet-based OFDM as confirmed to perform better than the FFT-OFDM. It is found that the beam-weight by SVD improves the performance of the system by about 2dB at the expense of the co-phasing method. The capacity performances of the weighting methods are also compared and discussed

Explanation of DC/RF Loci for Active Patch Antennas

YesA characteristic loop locus of dc power versus RF output power was observed as the frequency was varied around the optimum point of an operational active antenna. A new technique was introduced into the simulation, plotting the dependence of parameters such as supply current, efficiency or output power on internal impedance as seen by the naked transistor. It is now clear that the loop was formed as a consequence of the interaction of the transistor packaging elements with the patch impedances

Assessment of health risks associated with wastewater irrigation in Yola Adamawa State, Nigeria

The study was conducted to assess the health risks from the use of wastewater for irrigation to ensure a sustainable and safer agricultural production. Samples of wastewater and lettuce wash-water were analyzed to determine the faecal coliform count and the presence of helminth eggs. Besides, the opinion of the public was seeked through the use of questionnaire. The data collected were analysed using some statistical analysis (ANOVA), correlation analysis and simple statistics. The result shows that there were significant differences (p ≥ 0.05) among the faecal coliform counts in the wastewater of the study area. However, in the case of the lettuce wash-water, there were no significant differences (P ≥ 0.05) among the values of the faecal coliform in the area except that of Bajabure which differed significantly from the rest. The result also shows that there was no correlation (r = -0.15) between the faecal coliform in the wastewater and that in the lettuce wash-water. Helthminth eggs were found to be present in some of the wastewater and the lettuce wash-water of the study area

Frequency Tuned Planar Inverted F Antenna with L Shaped Slit Design for Wide Frequency Range.

yesA frequency tuned antenna has been designed to meet the coverage requirements of the DCS, PCS, UMTS and WLAN bands. The antenna consists of a main patch, and a planar inverted L (PIL) slot. The radiator patch is fed, and shorted, using simple feed lines with broadband characteristics. The handset represents the finite ground plane, and a varactor diode is mounted across the middle of the slot for tuning purposes. Initial tuning was obtained by placing lumped capacitors, instead of the varactor, over the radiator. Good agreement is obtained between the predicted and measured input return loss, gain and radiation pattern over the tuned frequency range.MSCR