Dual-band and switched-band highly efficient power amplifiers

The Power Amplifier is the most challenging module of a wireless network to design and it is the highest power consumer. Lots of research has been dedicated to design highly efficient and linear power amplifiers. The high demand for wireless communication systems creates the requirement for multiband transmitters and receivers. Providing high efficiency for power amplifiers in multiband applications is even more challenging. The work presented in this thesis is focused on designing high efficiency frequency adaptive power amplifiers. Frequency adaptive power amplifiers are categorized in three groups: broadband, multi-band and switched-band power amplifiers. Two main design methodologies of frequency adaptive power amplifiers are proposed in this thesis. They are dual-band and switched-band power amplifiers. The advantages and limitations of their output performances are evaluated. The main goals in this thesis are achieving high efficiency and required output power over all working bands and maintaining consistent performance over the bandwidth. In the dual-band power amplifiers, the distributed matching network is designed without any switches. Both of the switched-band Class-E power amplifiers have switched shunt capacitor values. The results demonstrate the tradeoffs between achieving consistent high performance in each band and introducing losses and complexity in the switching design

Experimental evaluation of 79 and 300 ghz radar performance in fire environments^†

This paper presents an experimental study of the propagation of mm-wave/low-THz signals in the frequency ranges of 79 and 300 GHz through fire. Radar performance was investigated in various real scenarios, including fire with strong flame, dense smoke and water vapour. A stereo video camera and a LIDAR were used as a comparison with other common types of sensors. The ability of radars to enable the visibility of objects in fire environments was proven. In all scenarios, the radar signal attenuation was measured, and in the case of steam was compared with theoretical calculations. The analysis of the experimental results allows us to conclude that there are good prospects for millimetre wave and Low Terahertz radar in the field of firefighting imaging equipment.</p

The effect of 6 weeks of Tai chi training on cognitive status, dynamic balance and quality of life in women with stroke

Background and Objectives: Stroke can lead to permanent disabilities, including motor and cognitive impairments. The aim of this study was to determine the effect of Tai Chi training on cognitive status, dynamic balance, and quality of life in women with stroke. Methods: In this quasi-experimental study, 20 women with stroke (mean age, 65.8&plusmn;3.5 years; weight, 68.4&plusmn;14kg; and body mass index, 26.3&plusmn;5.1kg/m2) in Qom city, were selected voluntarily and randomly divided into experimental (N=10) and control (N=10) groups. Cognitive status, dynamic balance, and quality of life were assessed by Mini-Mental State Examination (MMSE) and SF-36 quality of life questionnaires and Timed Up and Go test. Tai Chi group trained for 6 weeks, three 60-minute sessions per week (a 10-minute warm-up period, a 40-minute simplified Tai Chi exercise, and a 10-minute cool-down period). Data were analyzed using dependent and independent t-tests and (p<0.05). Results: Significant increases were observed in mental health, physical function, role limitations due to physical problems, and total quality of life score in the experimental group compared to the control group (p0.05). Conclusion: According to de results of the study, it can be said that Tai Chi training as a low-intensity and simple training improves dynamic balance and quality of life in women with stroke

Automotive Radar Parameter Estimation for Cognitive Interference Mitigation

A methodology to estimate waveform parameters of unknown interfering signals and number of interfering sources within the field of view of victim radar (VR) is presented using real time measured data. On the basis of identified interference parameters, waveform parameters of VR can be cognitively adapted to mitigate interference using ‘sense and avoid’ approach