Feedforward Amplifiers for Wideband Communication Systems

ISBN-13: 9780387351377 / Angielski / Twarda / 2006 / 178 str.

Jon Legarda

Opis

Feedforward Amplifiers for Wideband Communication Systems has been possible thanks to the research carried out throughout several years in the field of the linearization techniques applied to digital communication systems, particularly to those with high spectral efficient modulation techniques. The wireless telecommunications are more and more demanded for the Information Society. Such requirements are reflected as a great many of communication standards with specific coverage applications and, above all, with higher and higher data transmission rates. The electromagnetic spectrum, nevertheless, is a scarce asset that can not be spread and despite the increasingly tendency to transmit in higher frequencies, the bandwidths assigned to each application are always exploited to the limit. Feedforward Amplifiers for Wideband Communication Systems merges in the need of developing frequency efficient modulations with widespread codification techniques that result in wideband communication systems, with strict regulations in the usable frequency bandwidths and tight restrictions in the spurious emissions over the remaining spectrum. The radio frequency transmitters do not remain impassive to those changes, especially the power amplifiers, which efficiency and linearity directly determines the correct performance of the entire transmission system. The linearity specifications are commonly fixed by the telecommunication standards while the efficiency rates directly strikes the commercial viability of these transmitters. Feedforward Amplifiers for Wideband Communication Systems tries to put into practice the Feedforward linearization technique, aimed at improving either the linearity or efficiency parameters of power amplifiers, just intended for achieving a trade-off between the distortion specifications of the telecommunication standards and the efficiency enhancement of the transmission systems, which set, respectively, the linearity and the output level requirements of power amplifiers. This challenge is enshrined in one of the present wideband communication systems, but all the recommended design guidelines are perfectly reusable in the future wideband applications.

Spis treści

Dedication. Preface. Acknowledgments. 1. Introduction. 1. Radio-Electric transmitters - Historical overview. 1.1 Arc and spark transmitters. 1.2 Multi-polar alternators. 1.3 Thermoionic vacuum tubes. 1.4 Discrete transistors. 1.5 Integrated transistors. 2. Digital communication systems. 2.1 Analog signal. 2.2 Discrete signal. 2.3 Digital signal. 2.4 Digital transmission. 2.5 Electromagnetic spectrum. 2.6 Modulation techniques. 2.7 Signal degradation. 2.7.1 Attenuation. 2.7.2 Noise. 2.7.3 Distortion. 2.8 Basic architectures of wireless transmitters. 2.8.1 Analog I/Q modulator vs. digital IF. 2.8.2 Other implementations. 3. Digital modulation. 3.1 Applications. 3.2 Phase Shift Keying. 3.3 Frequency Shift Keying. 3.4 Minimum Shift Keying. 3.5 Quadrature Amplitude Modulation. 3.5.1 I/Q offset modulation. 3.5.2 Differential modulation. 3.6 Broadband wireless access techniques. 2. Nonlinear distortion. 1. Harmonic distortion. 1.1 Nth harmonic distortion coefficient. 1.2 Global harmonic distortion. 2. Intermodulation analysis. 2.1 2 tone intermodulation. 2.2 3 tone intermodulation. 3. Cross modulation (XMOD). 3.1Cross modulation (m>1). 4. Distortion measurement techniques. 4.1 Harmonic distortion measurement. 4.2 Third order distortion measurement. 4.2.1 Two tone procedure. 4.2.2 Third order intercept point (IP3). 4.3 Second order distortion measurement. 4.4 Cross modulation (Xmod) measurement. 5. Measurements of wideband digital signals. 5.1 Peak to average power ratio and CCDF curves. 5.2 Modulation quality measurements. 5.3 Code domain power. 5.4 Adjacent Channel Leakage Ratio (ACLR). 3. RF power amplifiers. 1. Classification of power amplifiers. 2. Power amplifiers parameters. 2.1 The efficiency rate. 2.2 The back-off. 2.3 Power utilization factor (PUF). 3. Class A. 4. Class B. 5. Class AB (outphasing). 6. Class C. 7. Switching amplifiers. 7.1 Class D. 7.2 Class E. 7.3 Class F. 8. More operating modes. 4. Linearization techniques. 1. Classification of the linearization techniques. 2. Feedback. 2.1 RF Feedback. 2.2 Envelope Feedback. 2.3 Envelope and phase Feedback. 2.4 Polar Loop. 2.5 Cartesian Loop. 3. Predistortion. 3.1 RF Predistortion. 3.1.1 Simple analog Predistortion. 3.1.2 Compound Predistortion. 3.2 Envelope Predistortion. 3.3 Baseband Predistortion. 4. Feedforward. 5. Efficiency enhancement techniques. 5.1 Bypassing. 5.2 Envelope Elimination and Restoration. 5.3 Bias Adaptation. 5.4 LINC. 5.5 Doherty Method. 5.6 CALLUM. 6. Comparison of linearization techniques. 5. Feedforward amplifiers. 1. Feedforward linearization technique. 1.1 Frequency dependence. 1.2 Amplitude and phase adjustments. 1.3 Error amplifier distortion. 1.4 Isolation lack. 1.5 Main signal path loss. 2. Feedforward in wideband communications systems. 6. Implementation of Feedforward amplifiers. 1. Simulation of the Feedforward architecture. 1.1 Simulation models. 1.2 Simulation of the error loop. 1.3 Simulation of the distortion cancellation loop. 1.4 The isolation effect. 2. Selection of the error amplifier. 3. The adjustment of the cancellation loops. 3.1 Delay lines. 3.1.1 Configuration. 3.1.2 Length tolerances. 3.1.3 Packaging. 3.1.4 System design. 3.2 An adjustment method for delay lines. 4. Distortion enhanced measurement techniques. 4.1 Spectrum analyzer mixer level