Jouko Vankka

A major advantage of a direct digital synthesizer (DDS) is that its output frequency, phase and amplitude can be precisely and rapidly manipulated under digital processor control. Other inherent DDS attributes include the ability to tune with extremely fine frequency and phase resolution, and to rapidly `hop' between frequencies. These combined characteristics have made the technology popular in military radar and communications systems. In fact, DDS technology was previously applied almost exclusively to high-end and military applications: it was costly, power-hungry, difficult to implement, and required a discrete high speed D/A converter. Due to improved integrated circuit (IC) technologies, they now present a viable alternative to analog-based phase-locked loop (PLL) technology for generating agile analog output frequency in consumer synthesizer applications. It is easy to include different modulation capabilities in the DDS by using digital signal processing (DSP) methods, because the signal is in digital form. By programming the DDS, adaptive channel bandwidths, modulation formats, frequency hopping and data rates are easily achieved. The flexibility of the DDS makes it ideal for signal generator for software radio. The digital circuits used to implement signal-processing functions do not suffer the effects of thermal drift, aging and component variations associated with their analog counterparts. The implementation of digital functional blocks makes it possible to achieve a high degree of system integration. Recent advances in IC fabrication technology, particularly CMOS, coupled with advanced DSP algorithms and architectures are providing possible single-chip DDS solutions to complex communication and signal processing subsystems as modulators, demodulators, local oscillators, programmable clock generators, and chirp generators. The DDS addresses a variety of applications, including cable modems, measurement equipments, arbitrary waveform generators, cellular base stations and wireless local loop base stations. Direct Digital Synthesizers was written to find possible applications for radio communication systems. It will have appeal for wireless and wireline communication engineers, teachers and students.

The approach adopted in Digital Synthesizers and Transmitters for Software Radio will provide an understanding of key areas in the field of digital synthesizers and transmitters. It is easy to include different digital techniques in the digital synthesizers and transmitters by using digital signal processing methods, because the signal is in digital form. By programming the digital synthesizers and transmitters, adaptive channel bandwidths, modulation formats, frequency hopping and data rates are easily achieved. Techniques such as digital predistortion for power amplifier linearization, digital compensation methods for analog I/Q modulator nonlinearities and digital power control and ramping are presented in this book. The flexibility of the digital synthesizers and transmitters makes them ideal as signal generators for software radio. Software radios represent a major change in the design paradigm for radios in which a large portion of the functionality is implemented through programmable signal processing devices, giving the radio the ability to change its operating parameters to accommodate new features and capabilities. A software radio approach reduces the content of radio frequency (RF) and other analog components of traditional radios and emphasizes digital signal processing to enhance overall transmitter flexibility. Software radios are emerging in commercial and military infrastructure.

The approach adopted in Digital Synthesizers and Transmitters for Software Radio will provide an understanding of key areas in the field of digital synthesizers and transmitters. It is easy to include different digital techniques in the digital synthesizers and transmitters by using digital signal processing methods, because the signal is in digital form. By programming the digital synthesizers and transmitters, adaptive channel bandwidths, modulation formats, frequency hopping and data rates are easily achieved. Techniques such as digital predistortion for power amplifier linearization, digital compensation methods for analog I/Q modulator nonlinearities and digital power control and ramping are presented in this book. The flexibility of the digital synthesizers and transmitters makes them ideal as signal generators for software radio. Software radios represent a major change in the design paradigm for radios in which a large portion of the functionality is implemented through programmable signal processing devices, giving the radio the ability to change its operating parameters to accommodate new features and capabilities. A software radio approach reduces the content of radio frequency (RF) and other analog components of traditional radios and emphasizes digital signal processing to enhance overall transmitter flexibility. Software radios are emerging in commercial and military infrastructure.

A major advantage of a direct digital synthesizer (DDS) is that its output frequency, phase and amplitude can be precisely and rapidly manipulated under digital processor control. Other inherent DDS attributes include the ability to tune with extremely fine frequency and phase resolution, and to rapidly `hop' between frequencies. These combined characteristics have made the technology popular in military radar and communications systems. In fact, DDS technology was previously applied almost exclusively to high-end and military applications: it was costly, power-hungry, difficult to implement, and required a discrete high speed D/A converter. Due to improved integrated circuit (IC) technologies, they now present a viable alternative to analog-based phase-locked loop (PLL) technology for generating agile analog output frequency in consumer synthesizer applications. It is easy to include different modulation capabilities in the DDS by using digital signal processing (DSP) methods, because the signal is in digital form. By programming the DDS, adaptive channel bandwidths, modulation formats, frequency hopping and data rates are easily achieved. The flexibility of the DDS makes it ideal for signal generator for software radio. The digital circuits used to implement signal-processing functions do not suffer the effects of thermal drift, aging and component variations associated with their analog counterparts. The implementation of digital functional blocks makes it possible to achieve a high degree of system integration. Recent advances in IC fabrication technology, particularly CMOS, coupled with advanced DSP algorithms and architectures are providing possible single-chip DDS solutions to complex communication and signal processing subsystems as modulators, demodulators, local oscillators, programmable clock generators, and chirp generators. The DDS addresses a variety of applications, including cable modems, measurement equipments, arbitrary waveform generators, cellular base stations and wireless local loop base stations. Direct Digital Synthesizers was written to find possible applications for radio communication systems. It will have appeal for wireless and wireline communication engineers, teachers and students.