Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / Modern day digital modulation techniques in communication systems produce large peak-to-average ratios. To maintain linearity, power amplifiers have to operate at backed-off levels. This results in low efficiency with consequences such as high power consumption, short battery life and excessive heat in power amplifiers. A Doherty amplifier is an efficiency enhancement technique which increases an amplifier’s efficiency at backed-off levels. This thesis presents a design procedure for a Classical Doherty amplifier. A method where Sparameter measurements from a transistor are used to predict the transistor’s transmission phase response for varying input power is presented. This method is found to be accurate by comparing it to measurements done on a non-linear network analyser. The measured S-parameters are also used to design the Doherty amplifier at its predicted peak output power. Two Classical Doherty amplifiers are designed, manufactured and characterised. The measurements are performed on a custom measurement setup using in-house developed Matlab code to automate the measurements. The first Doherty amplifier used small-signal Siemens CFY30 GaAs FETs and the second Doherty amplifier used 10W Motorola MRF282 LDMOS transistors. The performance of both amplifiers is compared to similar balanced amplifiers and shows improvements in their efficiency. The improvement in efficiency for the 10W Doherty power amplifier in relation to a balanced amplifier is compared to results found in the literature and a good correspondence between the measured and published results were obtained.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The thesis details the design, construction and experimental evaluation of 30W, 35W and 250W L-Band LDMOS Radar amplifiers. Each amplifier module contains an integrated high speed power supply in order to optimize RF pulse repeatability and to improve radar MTI factor (Moving Target Indication.) As part of the work, a pulsed RF measurement system for measuring the dynamic I-V curves of a power FET was developed. Work was also done on low impedance S-parameter measurement test fixtures for the characterisation of power FETs. These measurement systems generated design information which was used in the development of the L-Band power amplifiers / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwerp, bou en experimentele evaluering van „n 30W, 35W en 250W L-band LDMOS radarversterker. Elke versterker bevat ook „n geintegreerde hoë-spoed kragbron om optimum RF pulsherhaalbaarheid te verseker en die radar se „MTI (Moving Target Indication)‟ te verbeter. „n RF-pulsmetingstelsel is ook ontwikkel om die dinamiese I-V kurwes van „n hoë-krag FET te meet. Verder is daar ook gewerk aan „n toetsopstelling vir lae-impedansie S-parameters om hoë-krag FETs te karakteriseer. Hierdie toetsopstelling is gebruik om ontwerpsdata te genereer wat gebruik is in die ontwerp van die L-band kragversterkers.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Cellular radio communication involves wireless transmission and reception of signals at radio frequencies (RF). Base stations house equipment critical to the transmission and reception of signals. Power amplifier (PA) is a crucial element in base station assembly. PAs are expensive, take up space and dissipate heat. Of all the elements in the base station, it is difficult to design and operate a power amplifier. New designs of power amplifiers are constantly tested. One of the most important components required to perform this test successfully is a circuit simulator model of an entire communication system that generates a standard test signal. Standard test signals 524,288 data points in length require 1080 hours to complete one test of a PA model. In order to reduce the time taken to complete one test, a 'simulated test signal,' was generated. The objective of this study is to develop an algorithm to generate this 'simulated' test signal such that its characteristics match that of the 'standard' test signal.

Lin Pui-Yu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 103-105). / Abstracts in English and Chinese. / Acknowledgement / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Nonlinear Phenomenon of Power Amplifier --- p.5 / Chapter 2.1. --- AM-AM and AM-PM Distortion --- p.5 / Chapter 2.2. --- Intermodulation Distortion --- p.7 / Chapter Chapter 3 --- Linearization Techniques --- p.10 / Chapter 3.1. --- Power Backoff --- p.11 / Chapter 3.2. --- Feedback --- p.12 / Chapter 3.3. --- Predistortion --- p.12 / Chapter 3.4. --- Feedforward --- p.14 / Chapter 3.5. --- Other Linearization Techniques --- p.15 / Chapter Chapter 4 --- Analysis of Feedforward Power Amplifier --- p.17 / Chapter 4.1. --- Feedforward Efficiency --- p.18 / Chapter 4.2. --- Design Criteria of the Auxiliary Amplifier --- p.20 / Chapter 4.3. --- Sensitivity Analysis --- p.21 / Chapter 4.3.1. --- Phase and Amplitude Mismatch --- p.22 / Chapter 4.3.2. --- Delay Mismatch --- p.23 / Chapter 4.3.3. --- Combined Effect --- p.25 / Chapter 4.3.4. --- Practical Consideration --- p.27 / Chapter 4.4. --- Other Design Criteria --- p.28 / Chapter Chapter 5 --- Adaptive Control Networks for FFPA --- p.29 / Chapter 5.1. --- Basic Principles of the Adaptive Control Network --- p.30 / Chapter 5.1.1. --- Lookup Table --- p.30 / Chapter 5.1.2. --- Power Minimization Vs. Correlation --- p.31 / Chapter 5.2. --- Analog Vs Digital Implementation of the Adaptive Control Network --- p.34 / Chapter 5.3. --- Techniques for Improving the Convergence Behaviour at the Distortion Cancellation Loop --- p.35 / Chapter 5.4. --- Important Notes on the Control Networks --- p.38 / Chapter Chapter 6 --- Novel Analysis of Adaptive FFPA --- p.40 / Chapter 6.1. --- Gradient algorithm --- p.40 / Chapter 6.2. --- Dual Loop Adaptive FFPA --- p.41 / Chapter 6.2.1. --- System Modeling --- p.42 / Chapter 6.2.2. --- Adaptation Behavior of the Distortion Extraction Loop --- p.44 / Chapter 6.2.3. --- Adaptation Behavior of the Distortion Cancellation Loop --- p.48 / Chapter 6.2.4. --- Accuracy Requirement of the Control Signals --- p.50 / Chapter 6.2.5. --- Effect of Delay Mismatch on the Convergence Accuracy --- p.51 / Chapter 6.2.6. --- Convergence Behaviors for Two Tone Input Signal --- p.52 / Chapter 6.2.6.1. --- Distortion Extraction Loop --- p.53 / Chapter 6.2.6.2. --- Distortion Cancellation Loop --- p.55 / Chapter 6.2.6.3. --- Simulation Results --- p.57 / Chapter 6.2.7. --- Convergence Behaviors for Digital Modulated Test signal --- p.60 / Chapter 6.2.7.1. --- Distortion Extraction Loop --- p.61 / Chapter 6.2.7.2. --- Distortion Cancellation Loop --- p.66 / Chapter 6.2.7.3. --- Simulation Results --- p.68 / Chapter 6.2.8. --- Comparison for the Adaptation Performance with Two Tone and Digital Modulated Test Signal --- p.70 / Chapter 6.3. --- Triple Loop Adaptive FFPA --- p.71 / Chapter 6.3.1. --- Adaptation Performance of the Additional Loop --- p.73 / Chapter 6.3.2. --- Adaptation Performance of the Distortion Cancellation Loop --- p.75 / Chapter 6.3.3. --- Improvement in Bias Error at the Distortion Cancellation Loop --- p.76 / Chapter 6.3.4. --- Effect of Delay Mismatch --- p.77 / Chapter 6.3.5. --- Simulation Results --- p.79 / Chapter Chapter 7 --- Implementation and Measured Performance of Triple Loop Adaptive FFPA --- p.85 / Chapter 7.1. --- Hardware Design --- p.85 / Chapter 7.1.1. --- Vector Modulator --- p.87 / Chapter 7.1.2 --- Complex Correlator --- p.88 / Chapter 7.2. --- Experimental Setup and Measured Results --- p.90 / Chapter Chapter 8 --- Conclusion --- p.95 / Appendix I Matlab Program for Simulation of Dual Loop Adaptive FFPA --- p.97 / Appendix II Matlab Program for Simulation of Triple Loop Adaptive FFPA --- p.100 / Reference --- p.103 / Author's Publication --- p.106

Leung Chi-Shuen. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 82-89). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Review of Linearization Techniques --- p.4 / Chapter 2.1 --- Feedforward --- p.5 / Chapter 2.2 --- Feedback --- p.7 / Chapter 2.3 --- Predistortion --- p.10 / Chapter Chapter 3 --- The Volterra Series Method for Nonlinear Analysis --- p.12 / Chapter 3.1 --- Volterra Series Method --- p.13 / Chapter 3.2 --- Nonlinear Transfer Function --- p.14 / Chapter 3.3 --- Weakly Nonlinear Approximation --- p.18 / Chapter 3.4 --- Nonlinear Modeling --- p.19 / Chapter 3.5 --- Determination of Nonlinear Transfer Function --- p.22 / Chapter Chapter 4 --- Manifestation of Nonlinear Behavior --- p.25 / Chapter 4.1 --- Two-Tone Volterra Series Analysis --- p.25 / Chapter 4.2 --- Harmonic Distortion --- p.28 / Chapter 4.3 --- AM/AM and AM/PM --- p.29 / Chapter 4.4 --- Intermodulation Distortion --- p.31 / Chapter Chapter 5 --- The Generalized Baseband Signal Injection Method --- p.33 / Chapter 5.1 --- Generalized Baseband Signal Injection Method (GM) --- p.34 / Chapter 5.2 --- Application of GM to Predistorter-Amplifier Linearization --- p.38 / Chapter 5.2.1 --- Case 1: Standalone Amplifier without Injection --- p.40 / Chapter 5.2.2 --- Case 2: Injection to Amplifier Only --- p.41 / Chapter 5.2.3 --- Case 3: Injection to Diode Predistorter Only --- p.41 / Chapter 5.2.4 --- Case 4: Injection to Both Diode Predistorter and Amplifier --- p.42 / Chapter 5.3 --- Application of GM to Multi-Stage Amplifier Linearization --- p.43 / Chapter 5.3.1 --- Case 1: Amplifying System with No Signal Injection --- p.46 / Chapter 5.3.2 --- Case 2: Amplifying System with Single Injection Point --- p.47 / Chapter 5.3.3 --- Case 3: Amplifying System with Two Injection Points --- p.48 / Chapter Chapter 6 --- Experimental Setup and Measurements --- p.50 / Chapter 6.1 --- Experimental Setup --- p.51 / Chapter 6.1.1 --- Diode Predistorter --- p.51 / Chapter 6.1.2 --- Small Signal Amplifier --- p.54 / Chapter 6.1.3 --- Medium Power Amplifier --- p.58 / Chapter 6.1.4 --- Baseband Signal Generation Circuit --- p.61 / Chapter 6.1.5 --- Baseband Amplifiers --- p.63 / Chapter 6.2 --- Linearization of Amplifier with Predistortion Circuitry --- p.65 / Chapter 6.2.1 --- Two-Tone Test --- p.65 / Chapter 6.2.2 --- Vector Signal Test --- p.68 / Chapter 6.2.3 --- Dynamic Range Evaluation --- p.70 / Chapter 6.3 --- Linearization of Multi-Stage Amplifying System --- p.71 / Chapter 6.3.1 --- Determination of Transfer and Gain Coefficients --- p.71 / Chapter 6.3.2 --- Two-Tone Test --- p.74 / Chapter 6.3.3 --- Vector Signal Test --- p.77 / Chapter 6.3.4 --- Dynamic Range Evaluation --- p.79 / Chapter Chapter 7 --- Conclusion and Future Work --- p.80 / References --- p.82 / Author's Publications --- p.90

Digital transmitters offer several advantages over conventional analog transmitters such as reconfigurability, elimination of scaling-unfriendly, power hungry and bulky analog blocks and portability across technology. The rapid advancement of technology in CMOS processes also enables integration of complex digital signal processing circuitry on the same die as the digital transmitter to compensate for their non-idealities. The use of this digital assistance can, for instance, enable the use of highly efficient but nonlinear switching-class power amplifiers by compensating for their severe nonlinearity through digital predistortion. While this shift to digitally intensive transmitter architectures is propelled by the benefits stated above, several pressing challenges arise that vary in their nature depending on the frequency of operation - from RF to mmWave. Millimeter wave CMOS power amplifiers have traditionally been limited in output power due to the low breakdown voltage of scaled CMOS technologies and poor quality of on-chip passives. Moreover, high data-rates and efficient spectrum utilization demand highly linear power amplifiers with high efficiency under back-off. However, linearity and high efficiency are traditionally at odds with each other in conventional power amplifier design. In this dissertation, digital assistance is used to relax this trade-off and enable the use of state-of-the-art switching class power amplifiers. A novel digital transmitter architecture which simultaneously employs aggressive device-stacking and large-scale power combining for watt-class output power, dynamic load modulation for linearization, and improved efficiency under back-off by supply-switching and load modulation is presented. At RF frequencies, while the problem of watt-class power amplification has been long solved, more pressing challenges arise from the crowded spectrum in this regime. A major drawback of digital transmitters is the absence of a reconstruction filter after digital-to-analog conversion which causes the baseband quantization noise to get upconverted to RF and amplified at the output of the transmitter. In high power transmitters, this upconverted noise can be so strong as to prevent their use in FDD systems due to receiver desensitization or impose stringent coexistence challenges. In this dissertation, new quantization noise suppression techniques are presented which, for the first time, contribute toward making watt-class fully-integrated digital RF transmitters a viable alternative for FDD and coexistence scenarios. Specifically, the techniques involve embedding a mixed-domain multi-tap FIR filter within highly-efficient watt-class switching power amplifiers to suppress quantization noise, enhancing the bandwidth of noise suppression, enabling tunable location of suppression and overcoming the limitations of purely digital-domain filtering techniques for quantization noise.

Ng, Yuen Sum. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Abstract also in Chinese. / Chapter 1. --- INTRODUCTION --- p.11 / Chapter 1.1 --- Motivation --- p.11 / Chapter 1.2 --- Specifications --- p.12 / Chapter 1.3 --- Organization of the Thesis --- p.16 / Chapter 1.4 --- References --- p.16 / Chapter 2. --- BASIC THEORY OF POWER AMPLIFIER AND TRANSMITTER FRONT-END --- p.18 / Chapter 2.1 --- Classification of Power Amplifier --- p.18 / Chapter 2.1.1 --- Class A --- p.20 / Chapter 2.1.2 --- Class B --- p.21 / Chapter 2.1.3 --- Class AB --- p.22 / Chapter 2.1.4 --- Class C --- p.23 / Chapter 2.1.5 --- Class D --- p.24 / Chapter 2.1.6 --- Class E --- p.25 / Chapter 2.1.7 --- Class F --- p.28 / Chapter 2.2 --- Figure-of-Mhrit of Power Amplifier --- p.28 / Chapter 2.2.1 --- Small Signal Analysis --- p.29 / Chapter 2.2.1.1 --- S-parameter --- p.29 / Chapter 2.2.1.2 --- Gain and Stability --- p.29 / Chapter 2.2.2 --- Large Signal Analysis --- p.32 / Chapter 2.2.2.1 --- 1-dB compression point --- p.33 / Chapter 2.2.2.2 --- Third-order intermodulation point --- p.33 / Chapter 2.2.2.3 --- Power Gain --- p.35 / Chapter 2.2.2.4 --- Drain Efficiency and Power Added Efficiency --- p.35 / Chapter 2.2.2.5 --- AM-AM and AM-PM conversion --- p.36 / Chapter 2.2.3 --- Modulation Analysis --- p.36 / Chapter 2.2.3.1 --- Constellation Diagram and Error Vector Magnitude --- p.36 / Chapter 2.3 --- Reference --- p.37 / Chapter 3. --- CIRCUIT DESIGN OF POWER AMPLIFIER --- p.39 / Chapter 3.1 --- Introduction --- p.39 / Chapter 3.2 --- Topology of the Power Amplifier Design --- p.39 / Chapter 3.3 --- Design in Power Amplifier --- p.40 / Chapter 3.2.1 --- Power Stage --- p.40 / Chapter 3.2.2 --- Driver Stage and Input matching --- p.46 / Chapter 3.4 --- Simulation Result on Power Amplifier --- p.49 / Chapter 3.5 --- Layout consideration --- p.50 / Chapter 3.6 --- Measurement Result on Power Amplifier --- p.51 / Chapter 3.4.1 --- Small signal measurement --- p.52 / Chapter 3.4.2 --- Large signal measurement --- p.55 / Chapter 3.4.3 --- Modulation measurement --- p.56 / Chapter 3.7 --- Performance Summary --- p.58 / Chapter 3.8 --- Reference --- p.59 / Chapter 4. --- CIRCUIT DESIGN OF TRANSMITTER FRONT-END --- p.60 / Chapter 4.1 --- Introduction --- p.60 / Chapter 4.2 --- Topology of the Transmitter Front-End Design --- p.61 / Chapter 4.3 --- Design in transmitter front-end circuit --- p.64 / Chapter 4.2.1 --- I/Q Modulator --- p.64 / Chapter 4.2.2 --- Power Amplifier --- p.66 / Chapter 4.2.3 --- On-chip LC Balun --- p.72 / Chapter 4.4 --- Simulation Result of the Transmitter Front-End Design --- p.74 / Chapter 4.5 --- Layout consideration --- p.75 / Chapter 4.6 --- Measurement Result of the Transmitter Front-End Design --- p.76 / Chapter 4.4.1. --- Transmitter Front-End Measurement --- p.77 / Chapter 4.4.1.1 --- Output Reflection coefficient --- p.77 / Chapter 4.4.1.2 --- Large Signal Measurement --- p.78 / Chapter 4.4.1.3 --- Modulation Measurement --- p.81 / Chapter 4.4.2. --- LC Balun Measurement --- p.84 / Chapter 4.7 --- Performance Summary of the transmitter front-end circuit --- p.86 / Chapter 4.8 --- Reference --- p.89 / Chapter 5. --- CONCLUSION --- p.90 / Chapter 6. --- FUTURE WORK --- p.91

The nonlinearity of RF power amplifiers (PA) is one of critical concerns for RF designers because it causes spectral regrowth related to in-band and out-of-band spurious emissions control in communication standards. Traditionally, RF power amplifiers must be backed off considerably from the peak of their power level in order to prevent spectral regrowth. The digital predistortion (DPD) technique is being widely used for compensation of the nonlinearity of RF power amplifiers, as the high power efficiency becomes increasely important in wireless communication systems. However, the latest generations of communication systems, such as Wi-Fi, WiMAX, and LTE, using wider bandwidth have some additional memory distortion, other than the traditional memoryless distortion. The distortion caused by memory effect makes the traditional predistorter not precise any more for the PA linearization. In this dissertation, the traditional prediction of 3rd order memoryless spectrum regrowth is applied to 4G communication signals in terms of the 3rd intercept point of PAs, based on the previous researches in Portland State University led by Professor Fu Li. Then, the spectrum regrowth prediction is extended to an arbitrarily high order with intercept points of an RF power amplifier. A simple predistortion method which enables direct calculation of the predistorter coefficients from the intercept points is also proposed. Furthermore, the memory effect is taken into account for both PA modeling and predistortion. A simplified Hammerstein structure based method is proposed to analyze the nonlinear characteristic of PAs more precisely and completely. By applying the inverse structures of the PA model, the proposed predistorter corrects both the traditional memoryless nonlinear distortions and the memory effect that may exist in RF power amplifiers. The order of nonlinearity and depth of memory of a predistorter can be chosen from 0 to any arbitrarily high number. This increases the flexibility for designers to decide how to linearize power amplifier effectively and efficiently.

The RF high power amplifier is a key module in the NMR spectrometer. Robustness, lower power consumption, and small size are requirements. In this thesis, devices are studied and different design approaches are considered. New ideas are introduced, and simulations are used to show if it these work. A real prototype is developed. Results from the prototype are satisfactory and in good agreement with the simulation results. This allows for the possibility of a real portable NMR spectrometer 'Lapspec'. Points of note: • Feedback to stabilize amplifier, • Hard bias to improve rise time of pulse, • A rugged device is chosen, • Power limiter technology is used to avoid overdrive amplifier, • Lower value attenuator at output of final stage to reduce load VSWR, • Reason of spike is studied, the solution to reduce spike is given, • The reason of instability of amplifier with NMR load is analyzed, • A method is introduced to ensure there is no oscillation while the High Power Amplifier (HPA) is connected with the NMR probe.