• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 599
  • 80
  • 60
  • 25
  • 24
  • 13
  • 10
  • 10
  • 9
  • 9
  • 7
  • 7
  • 7
  • 7
  • 7
  • Tagged with
  • 1029
  • 1029
  • 312
  • 276
  • 179
  • 155
  • 150
  • 142
  • 124
  • 120
  • 105
  • 101
  • 101
  • 100
  • 86
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

Simultaneous transmission of baseband signal and in band RF signal

Chen, Cheng January 2015 (has links)
No description available.
212

CMOS RF low noise amplifier with high ESD immunity.

January 2004 (has links)
Tang Siu Kei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 107-111). / Abstracts in English and Chinese. / Acknowledgements --- p.ii / Abstract --- p.iii / List of Figures --- p.xi / List of Tables --- p.xvi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of Electrostatic Discharge --- p.1 / Chapter 1.1.1 --- Classification of Electrostatic Discharge Models --- p.1 / Chapter 1.2 --- Electrostatic Discharge in CMOS RF Circuits --- p.4 / Chapter 1.3 --- Research Goal and Contribution --- p.6 / Chapter 1.4 --- Thesis Outline --- p.6 / Chapter Chapter 2 --- Performance Parameters of Amplifier --- p.8 / Chapter 2.1 --- Amplifier Gain --- p.8 / Chapter 2.2 --- Noise Factor --- p.9 / Chapter 2.3 --- Linearity --- p.11 / Chapter 2.3.1 --- 1-dB Compression Point --- p.13 / Chapter 2.3.2 --- Third-Order Intercept Point --- p.14 / Chapter 2.4 --- Return Loss --- p.16 / Chapter 2.5 --- Power Consumption --- p.18 / Chapter 2.6 --- HBM ESD Withstand Voltage --- p.19 / Chapter Chapter 3 --- ESD Protection Methodology for Low Noise Amplifier --- p.21 / Chapter 3.1 --- Dual-Diode Circuitry --- p.22 / Chapter 3.1.1 --- Working Principle --- p.22 / Chapter 3.1.2 --- Drawbacks --- p.24 / Chapter 3.2 --- Shunt-Inductor Method --- p.25 / Chapter 3.2.1 --- Working Principle --- p.25 / Chapter 3.2.2 --- Drawbacks --- p.27 / Chapter 3.3 --- Common-Gate Input Stage Method --- p.28 / Chapter 3.3.1 --- Built-in ESD Protecting Mechanism --- p.29 / Chapter 3.3.2 --- Competitiveness --- p.31 / Chapter Chapter 4 --- Design Theory of Low Noise Amplifier --- p.32 / Chapter 4.1 --- Small-Signal Modeling --- p.33 / Chapter 4.2 --- Method of Input Termination --- p.33 / Chapter 4.2.1 --- Resistive Termination --- p.34 / Chapter 4.2.2 --- Shunt-Series Feedback --- p.34 / Chapter 4.2.3 --- l/gm Termination --- p.35 / Chapter 4.2.4 --- Inductive Source Degeneration --- p.36 / Chapter 4.3 --- Method of Gain Enhancement --- p.38 / Chapter 4.3.1 --- Tuned Amplifier --- p.38 / Chapter 4.3.2 --- Multistage Amplifier --- p.40 / Chapter 4.4 --- Improvement of Reverse Isolation --- p.41 / Chapter 4.4.1 --- Common-Gate Amplifier --- p.41 / Chapter 4.4.2 --- Cascoded Amplifier --- p.42 / Chapter Chapter 5 --- Noise Analysis of Low Noise Amplifier --- p.44 / Chapter 5.1 --- Noise Sources of MOS Transistor --- p.44 / Chapter 5.2 --- Noise Calculation using Noisy Two-Port Network --- p.46 / Chapter 5.3 --- Noise Calculation using Small-Signal Model --- p.49 / Chapter 5.3.1 --- Low Noise Amplifier with Inductive Source Degeneration --- p.49 / Chapter 5.3.2 --- Common-Gate Low Noise Amplifier --- p.52 / Chapter Chapter 6 --- Design of an ESD-protected CMOS Low Noise Amplifier --- p.54 / Chapter 6.1 --- Design of DC Biasing Circuitry --- p.55 / Chapter 6.2 --- Design of Two-Stage Architecture --- p.57 / Chapter 8.3.1 --- Design of Common-Gate Input Stage --- p.57 / Chapter 8.3.2 --- Design of Second-Stage Amplifier --- p.59 / Chapter 6.3 --- Stability Consideration --- p.61 / Chapter 6.4 --- Design of Matching Networks --- p.62 / Chapter 6.4.1 --- Design of Inter-Stage Matching Network --- p.64 / Chapter 6.4.2 --- Design of Input and Output Matching Networks --- p.67 / Chapter Chapter 7 --- Layout Considerations --- p.70 / Chapter 7.1 --- MOS Transistor --- p.70 / Chapter 7.2 --- Capacitor --- p.72 / Chapter 7.3 --- Spiral Inductor --- p.74 / Chapter 7.4 --- Layout of the Proposed Low Noise Amplifier --- p.76 / Chapter 7.5 --- Layout of the Common-Source Low Noise Amplifier --- p.79 / Chapter 7.6 --- Comparison between Schematic and Post-Layout Simulation Results --- p.81 / Chapter Chapter 8 --- Measurement Results --- p.82 / Chapter 8.1 --- Experimental Setup --- p.82 / Chapter 8.1.1 --- Testing Circuit Board --- p.83 / Chapter 8.1.2 --- Experimental Setup for s-parameter --- p.84 / Chapter 8.1.3 --- Experimental Setup for Noise Figure --- p.84 / Chapter 8.1.4 --- Experimental Setup for 1-dB Compression Point --- p.85 / Chapter 8.1.5 --- Experimental Setup for Third-Order Intercept Point --- p.86 / Chapter 8.1.6 --- Setup for HBM ESD Test --- p.87 / Chapter 8.2 --- Measurement Results of the Proposed Low Noise Amplifier --- p.89 / Chapter 8.2.1 --- S-parameter Measurement --- p.90 / Chapter 8.2.2 --- Noise Figure Measurement --- p.91 / Chapter 8.2.3 --- Measurement of 1-dB Compression Point --- p.92 / Chapter 8.2.4 --- Measurement of Third-Order Intercept Point --- p.93 / Chapter 8.2.5 --- HBM ESD Test --- p.94 / Chapter 8.2.6 --- Summary of Measurement Results --- p.95 / Chapter 8.3 --- Measurement Results of the Common-Source Low Noise Amplifier --- p.96 / Chapter 8.3.1 --- s-parameter Measurement --- p.97 / Chapter 8.3.2 --- Noise Figure Measurement --- p.98 / Chapter 8.3.3 --- Measurement of 1-dB Compression Point --- p.99 / Chapter 8.3.4 --- Measurement of Third-Order Intercept Point --- p.100 / Chapter 8.3.5 --- HBM ESD Test --- p.101 / Chapter 8.3.6 --- Summary of Measurement Results --- p.102 / Chapter 8.4 --- Performance Comparison between Different Low Noise Amplifier Designs --- p.103 / Chapter Chapter 9 --- Conclusion and Future Work --- p.105 / Chapter 9.1 --- Conclusion --- p.105 / Chapter 9.2 --- Future Work --- p.106 / References --- p.107 / Author's Publications --- p.112
213

A low power signal front-end for passive UHF RFID transponders with a new clock recovery circuit.

January 2009 (has links)
Chan, Chi Fat. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.2 / 摘要 --- p.5 / Acknowledgement --- p.7 / Table of Contents --- p.9 / List of Figures --- p.11 / List of Tables --- p.14 / Chapter 1. --- Introduction --- p.15 / Chapter 1.2. --- Research Objectives --- p.16 / Chapter 1.3. --- Thesis Organization --- p.18 / Chapter 1.4. --- References --- p.19 / Chapter 2. --- Overview of Passive UHF RFID Transponders --- p.20 / Chapter 2.1. --- Types of RFID Transponders and Design Challenges of Passive RFID Transponder --- p.20 / Chapter 2.2. --- Selection of Carrier Frequency --- p.22 / Chapter 2.3. --- Description of Transponder Construction --- p.22 / Chapter 2.3.1. --- Power-Generating Circuits --- p.23 / Chapter 2.3.2. --- Base Band Processor --- p.28 / Chapter 2.3.3. --- Signal Front-End --- p.29 / Chapter 2.4. --- Summary --- p.30 / Chapter 2.5. --- References --- p.31 / Chapter 3. --- ASK Demodulator for EPC C-l G-2 Transponder --- p.32 / Chapter 3.1. --- ASK Demodulator Design Considerations --- p.32 / Chapter 3.1.1. --- Recovered Envelope Distortion --- p.32 / Chapter 3.1.2. --- Input Power Level Considerations --- p.34 / Chapter 3.1.3. --- Input RF power Intercepted by ASK Demodulator --- p.36 / Chapter 3.2. --- ASK Demodulator Design From [3-4] --- p.36 / Chapter 3.2.1. --- Envelope Waveform Recovery Design --- p.37 / Chapter 3.2.1.1. --- Voltage Multiplier Branch for Generating Venv --- p.39 / Chapter 3.2.1.2. --- Voltage Multiplier Branch for Generating Vref --- p.41 / Chapter 3.2.2. --- Design Considerations for Sensitivity of ASK Demodulator --- p.41 / Chapter 3.2.3. --- RF Input Power Sharing with Voltage Multiplier --- p.44 / Chapter 3.2.4. --- ASK Demodulator and Voltage Multiplier Integrated Estimations for Maximum RF Power Input --- p.47 / Chapter 3.2.5. --- Measurement result and Discussion --- p.49 / Chapter 3.3. --- Proposed Envelope Detector Circuit --- p.52 / Chapter 3.3.1. --- Sensitivity Estimation --- p.52 / Chapter 3.3.2. --- Maximum Tolerable Input Power Estimation --- p.53 / Chapter 3.3.3. --- Envelope Waveform Recovery of the Proposed Envelope Detector --- p.54 / Chapter 3.4. --- Summary --- p.57 / Chapter 3.5. --- References --- p.58 / Chapter 4. --- Clock Generator for EPC C-l G-2 Transponder --- p.59 / Chapter 4.1. --- Design Challenges Overview of Clock Generator --- p.59 / Chapter 4.2. --- Brief Review of PIE Symbols in EPC C1G2 Standard --- p.62 / Chapter 4.3. --- Proposed Clock Recovery Circuit Based on PIE Symbols for Clock Frequency Calibration --- p.64 / Chapter 4.3.1. --- Illustration on PIE Symbols for Clock Frequency Calibration --- p.64 / Chapter 4.3.2. --- Symbol time-length counter --- p.72 / Chapter 4.3.3. --- The M2.56MHZ Reference Generator and Sampling Frequency Requirement --- p.75 / Chapter 4.3.4. --- Symbol Length Reconfiguration for Different Tari and FLL Stability --- p.80 / Chapter 4.3.5. --- Frequency Detector and Loop Filter --- p.83 / Chapter 4.3.6. --- Proposed DCO Design --- p.84 / Chapter 4.3.7. --- Measurement Results and Discussions --- p.88 / Chapter 4.3.7.1. --- Frequency Calibration Measurement Results --- p.89 / Chapter 4.3.7.2. --- Number x and Tari Variation --- p.92 / Chapter 4.3.7.3. --- Temperature and Supply Variation --- p.93 / Chapter 4.3.7.4. --- Transient Supply Variation --- p.94 / Chapter 4.3.8. --- Works Comparison --- p.95 / Chapter 4.4. --- Clock Generator with Embedded PIE Decoder --- p.96 / Chapter 4.4.1. --- Clock Generator for Transponder Review --- p.96 / Chapter 4.4.2. --- PIE Decoder Review --- p.97 / Chapter 4.4.3. --- Proposed Clock Generator with Embedded PIE Decoder --- p.97 / Chapter 4.4.4. --- Measurement Results and Discussions --- p.100 / Chapter 4.5. --- Summary --- p.103 / Chapter 4.6. --- References --- p.105 / Chapter 5. --- ASK Modulator --- p.107 / Chapter 5.1. --- Introduction to ASK Modulator in RFD Transponder --- p.107 / Chapter 5.2. --- ASK Modulator Design --- p.109 / Chapter 5.3. --- ASK Modulator Measurement --- p.110 / Chapter 5.4. --- Summary --- p.113 / Chapter 5.5. --- References --- p.113 / Chapter 6. --- Conclusions --- p.114 / Chapter 6.1. --- Contribution --- p.114 / Chapter 6.2. --- Future Development --- p.116
214

Adiabatic smart card / RFID.

January 2007 (has links)
Mok, King Keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 77-79). / Abstracts in English and Chinese. / Abstract --- p.1 / Contents --- p.5 / List of Figures --- p.7 / List of Tables --- p.10 / Acknowledgments --- p.11 / Chapter 1. --- Introduction --- p.12 / Chapter 1.1. --- Low Power Design --- p.12 / Chapter 1.2. --- Power Consumption in Conventional CMOS Logic --- p.13 / Chapter 1.2.1. --- Dynamic Power --- p.13 / Chapter 1.2.2. --- Short-Circuit Power --- p.15 / Chapter 1.2.3. --- Leakage Power --- p.17 / Chapter 1.2.4. --- Static Power --- p.19 / Chapter 1.3. --- Smart Card / RFID --- p.21 / Chapter 1.3.1. --- Applications --- p.21 / Chapter 1.3.2. --- Operating Principle --- p.22 / Chapter 1.3.3. --- Conventional Architecture --- p.23 / Chapter 2. --- Adiabatic Logic --- p.25 / Chapter 2.1. --- Adiabatic Switching --- p.25 / Chapter 2.2. --- Energy Recovery --- p.27 / Chapter 2.3. --- Adiabatic Quasi-Static CMOS Logic --- p.29 / Chapter 2.3.1. --- Logic Structure --- p.29 / Chapter 2.3.2. --- Clocking Scheme --- p.31 / Chapter 2.3.3. --- Flip-flop --- p.33 / Chapter 2.3.4. --- Layout Techniques --- p.38 / Chapter 3. --- Adiabatic RFID --- p.41 / Chapter 3.1. --- System Architecture --- p.41 / Chapter 3.2. --- Circuit Design --- p.42 / Chapter 3.2.1. --- Voltage Limiter --- p.43 / Chapter 3.2.2. --- Substrate Bias Generation Circuit --- p.45 / Chapter 3.2.3. --- Ring Oscillator --- p.46 / Chapter 3.2.4. --- ROM and Control Logic --- p.48 / Chapter 3.2.5. --- Load Modulator --- p.52 / Chapter 3.2.6. --- Experimental Results --- p.53 / Chapter 4. --- Adiabatic Smart Card --- p.59 / Chapter 4.1. --- System Architecture --- p.59 / Chapter 4.2. --- Circuit Design --- p.61 / Chapter 4.2.1. --- ASK Demodulator --- p.61 / Chapter 4.2.2. --- Clock Recovery Circuit --- p.63 / Chapter 4.3. --- Experimental Results --- p.67 / Chapter 5. --- Conclusion --- p.74 / Chapter 6. --- Future Works --- p.76 / Reference --- p.77 / Appendix --- p.80
215

Design and performance evaluation of RFID counting algorithms under time-correlated channels.

January 2012 (has links)
最近,幾種以Kodialam等人提出的RFID數量估計算法為基礎的新算法相繼出現。這些新算法不僅考慮到RFID讀器和RFID標簽之聞無線信道的不穩定性和不確定性,而且還可以保證其估算具有一定的準確性。然而,這些RFID數量估計算法的設計和性能評估都是基於一個比較簡化的信道模型。根據這個信道模型,封包在RFID讀器和標簽之聞傳送時遺失的概率是符合獨立分布的。然而,一些實證測量研究指出,在一般的室内環境,人的活動和設備的移動對信道的影響是不可忽視的。這些活動可以引起多普勒效應,從而使信號變成時域相關。因此,在真實的無線信道傳輸中,封包的遺失也是時域相關的。由於不同的RFID數量估計算法具體的設計和實現方法各有不同,封包遺失的時域相關性可能對這些RFID數量估計算法造成不同程度的影響。 / 在本論文中,我們評估了三系列的算法在更真實的時域相關的無線信道下的性能。具體來,我們重點研究和分析了時域相關性在哪些方面影響了現有的RFID數量估計算法的準確性。依據描述真實無線信道特性的實驗數據,我們改進了原來的信道模型,使其概括了RFID讀器和標簽之聞向前信道/向後信道的時域相關性。通過觀察這三系列算法在更真實的時域相關的無線信道下的表現,我們分析了造成估算值和真實值之間差距的原因。同時,提出了一些改善數量估計算法準確性的方法,並且通過模擬試驗證明這些改進可以提高算法在真實無線信道下的準確性。 / Recently, several new RFID counting algorithms have been proposed based on the probabilistic counting schemes introduced by Kodialam et. al.. These existing algorithms took into account the unreliable and non-deterministic nature of the radio communication channels between the RFID reader and the tags,and are capable of providing tag-count estimates that satisfy a desired level of accuracy. However, all algorithms were designed and evaluated based on a simplistic packet loss model. It assumes that the loss probability of a packet between the reader and the tag-set follows an independent, identical distribution. No characterizations of possible temporal correlations of the channels were performed. As presented by some empirical measurements, movements of personnel or equipments in a building can generate Doppler effect, which introduces time correlations to the fading signal. Thus, the realistic packet loss caused by the wireless channels is temporally correlated due to the frequent change of the nearby environment. Depending on specific implementation details of each individual algorithm,temporally correlated packet loss might have significant impact on the tag-set cardinality estimation. / In this thesis, we will evaluate the performance of the aforementioned RFID counting algorithms under a more sophisticated time-correlated channel fading model. In particular, we focus on investigating and analyzing how the temporal correlations would influence the accuracy of these existing counting algorithms. Based on the experimental statistics that characterized the realistic indoor channels, we refine the channel model to describe the time-correlation of the forward and backward channel between the RFID reader and the tags. We also modify the model to support implementations of different communication scenarios. Comparisons of the performance of the existing counting schemes under the simplistic uncorrelated packet loss channel model and the refined correlated channel model are conducted. We also propose extensions for these RFID counting schemes to mitigate the estimation inaccuracy generated by the correlated packet loss. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Deng, Yulin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 99-107). / Abstracts also in Chinese. / Abstract --- p.i / Acknowledgement --- p.vi / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background and related work --- p.7 / Chapter 3 --- Modeling time-correlated channels in RFID systems --- p.13 / Chapter 3.1 --- Memoryless channel model --- p.14 / Chapter 3.2 --- Backscattering channel model --- p.16 / Chapter 3.2.1 --- Discussions of channel differences with active tags --- p.18 / Chapter 3.3 --- Difficulties in extending mathematical analysis for Memoryless channel model to time-correlated Backscattering channel model --- p.19 / Chapter 3.4 --- Implementations of Backscattering channel model --- p.20 / Chapter 3.4.1 --- Model the one-way fading channel based on the Clarke and Gans model --- p.20 / Chapter 3.4.2 --- Other implementation aspects of the Twoway Backscattering channel model --- p.25 / Chapter 4 --- Performance evaluation of the First-two-moment implicit approach under time-correlated channels --- p.27 / Chapter 4.1 --- System model --- p.28 / Chapter 4.2 --- Estimator Accuracy --- p.30 / Chapter 4.3 --- Performance evaluation of the First-two-moment implicit RFID counting scheme over time-correlated channels --- p.32 / Chapter 4.3.1 --- Modeling differences --- p.34 / Chapter 4.3.2 --- Coherence time --- p.37 / Chapter 4.3.3 --- Rician fading channel --- p.40 / Chapter 4.3.4 --- Discussions for the case with active tags --- p.42 / Chapter 4.4 --- Correcting estimation errors under time-correlated channels --- p.44 / Chapter 4.4.1 --- Correcting estimation mean --- p.44 / Chapter 4.4.2 --- The impact of time-correlated channels on estimation variance --- p.47 / Chapter 4.5 --- Chapter summary --- p.49 / Chapter 5 --- Performance Evaluation of the Capture-Recapture approach under time-correlated channels --- p.50 / Chapter 5.1 --- System model --- p.51 / Chapter 5.2 --- Different estimation algorithms --- p.53 / Chapter 5.2.1 --- Union-based approach --- p.53 / Chapter 5.2.2 --- The Capture-Recapture approach --- p.55 / Chapter 5.3 --- Performance evaluation of the estimation schemes under time- correlated channels --- p.58 / Chapter 5.3.1 --- Simulation Setup --- p.60 / Chapter 5.3.2 --- Observations and Analysis --- p.65 / Chapter 5.4 --- Extensions of correcting the errors under timecorrelated channels --- p.69 / Chapter 5.5 --- Chapter Summary --- p.72 / Chapter 6 --- Performance evaluation of adaptive RFID counting algorithms under time-correlated channels --- p.74 / Chapter 6.1 --- System Model --- p.75 / Chapter 6.2 --- Adaptive RFID counting Algorithms --- p.76 / Chapter 6.2.1 --- Adaptive Union approach --- p.77 / Chapter 6.2.2 --- Probabilistic Estimation For Lossy Channels (PELOC) --- p.78 / Chapter 6.3 --- Performance evaluation of the adaptive counting algorithms under time-correlated channels --- p.80 / Chapter 6.3.1 --- Simulation Setup --- p.81 / Chapter 6.3.2 --- Observation and analysis --- p.82 / Chapter 6.4 --- Extensions to correct the inaccuracy under timecorrelated channels / Chapter 6.5 --- Chapter Summary --- p.93 / Chapter 7 --- Conclusion and Future work --- p.95 / Bibliography --- p.99
216

The Effects of Mobile Phone Radiation on the Human Central Nervous System

Perentos, Nicholas, nperentos@gmail.com January 2009 (has links)
The effects of mobile phone-like electromagnetic radiation on the human brain activity are examined. The research focuses on both radio frequency (RF) exposures and the much less studied low frequency (ELF) exposures (less than 40 kHz) arising from the battery operation of GSM handsets. The first single blind study recruited a small sample of twelve human volunteers. The eyes closed resting EEG activity is monitored after radio frequency exposure. With SAR levels of 2 W/kg, results reveal no statistical changes in any of the examined frequency bands for neither pulsed modulated RF signals nor continuous wave RF signals. In the second double blind study, a sample of 72 volunteers is recruited and an improved protocol comprised of separate pulsed RF, continuous RF and pulsed ELF exposures is employed. Exposures are delivered through a custom made handset capable of independent RF and ELF exposures. Findings include a reduced alpha band frequency activity during pulsed radio frequency and low frequency radiations exposures but no changes under the continuous RF radiation. Changes are present both during as well as after exposure, while greater changes are observed during exposures. The study of some non linear measures of the resting EEG revealed no changes under any of the active exposures. As the observed changes are very close to the normal EEG variation during resting conditions, their biological significance and health impact is not immediately obvious. However, their mere demonstration points to a low level interaction mechanism which may deserve further study.
217

Wideband HF power amplifier modelling for linearisation

Urmonas, Richard January 2003 (has links)
Existing linearisation methods were examined to establish the requirements for a wideband power amplifier model. A range of memoryless models were investigated, in particular polynomial models. No suitable memoryless models were found. The shortcomings of the models were analysed and directions for future investigations presented. / thesis (MEng(ElectronicsEngineering))--University of South Australia, 2003.
218

A study of the effects of mobile-phone type signals on calcium ion levels with a human leukaemic T cell line

Cranfield, Charles G., ccranfield@swin.edu.au January 2001 (has links)
The work presented here outlines experiments done using a novel RF exposure chamber. This device allows biological cells to be exposed to microwave radiation similar to those emitted by mobile telephones, whilst imaging them using a laserscanning confocal microscope. Jurkat E6.1 T lymphocytes in the exposure chamber were kept within �0.5�C of 37�C, allowing for the investigation of possible athermal effects of microwave energies. These cells were loaded with the fluorescent probe Fluo-3 AM, which is specific for calcium ions, and were monitored over two 10minute periods. The first period being a control period, the second being a period where the cells were either exposed to RF energy or sham exposed. Another 5min imaging period was for the positive control,where maximal fluorescence can be achieved by the addition of the ionophore A23187. 5 different conditions for cell exposure were investigated. Both continuous wave 900MHz and continuous wave 900MHz pulse modulated at 217Hz exposures were carried out on cells that were either unactivated, or those that were activated by the mitogen phytohaemaglutinin (PHA). For these 4 conditions the average Specific Absorption Rate (SAR) was calculated to be 1.5W/kg. A group of unactivated cells were also exposed to continuous wave 900MHz energy with an average SAR calculation of 7.5W/kg. Results showed that no significant changes in calcium ion levels occurred when averaged fluorescence slopes were compared between RF exposed cells and the control period. The mean change in slopes exposed/sham period � control period)between cells that were exposed and those sham exposed also showed no significant difference. Following an inference made in the work of Galvanovskis et al. (1999)1 who showed there is a change in the calcium ion oscillation spectrum as a result of 50Hz magnetic fields, a measure of the mean frequencies of all cells was determined using a Fast Fourier Transform (FFT) analysis. The change in the average mean frequencies in cells was then measured for all conditions. Of statistical significance was the change in average mean frequency between the control period and the sham/exposed period between cells that were exposed and those sham exposed, when cells were activated by PHA. The results also showed that there was an overall drop in average mean frequency as a result of RF exposure. Assuming there is a biological significance to the findings of this thesis, careful analysis of the calcium dynamics of tissue samples and cell types associated with RF exposure from mobile phones would need to be carried out to determine what they are. This was unfortunately beyond the scope of the present study.
219

Design, adoption and implementation issues in RFID applications

Zeng, Yuyu, January 2006 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.
220

The design of delta-sigma modulators for multi-standard RF receivers

Liu, Mingliang 09 June 2003 (has links)
The transition from second-generation (2G) to third-generation (3G) wireless cellular and cordless telephone systems requires multi-standard adaptability in a single RF receiver equipment. An important answer to this request is the use of Delta-Sigma modulators for IF-to-baseband conversion, which will satisfy the dynamic range requirements for digital signal processing, and at the same time, add adaptability and programmability to the characteristics of a RF receiver. This thesis addresses the issues of designing a Delta-Sigma modulator for a multi-standard wireless receiver. A single-loop third-order modulator topology suitable for low power and high integration multi-standard receiver design is proposed. The trade-offs in the modulator design are also presented and explained. The modulator, which has been implemented as a part of a monolithic receiver chip, will be fabricated in a standard 0.35-��m CMOS process. The post-layout simulation results have verified the outcomes of system analysis. / Graduation date: 2004

Page generated in 0.0397 seconds