TABLE OF CONTENTS The discussion of transmitter techniques up to this point has assumed that the transmitter components, most notably the RF power amplifier, are intrinsically linear to a degree commensurate with the application under consideration. This is typically not so and some form of linearisation or RF synthesis technique is required to create the desired high-power RF signal. A complete and detailed discussion of RF power amplifier linearisation techniques is beyond the scope of this book and has been previously undertaken by the author [1]. This section will therefore concentrate on summarizing the primary techniques for linearisation that are currently employed in software defined radio systems and how these may be incorporated or accommodated in the transmitter architectures outlined in Chapter 5.
The various options break down in to three categories:
Power amplifier linearisation techniques. These can be employed in direct substitution for the linear power amplifier blocks shown in the transmitter architectures outlined in Chapter 5.
Transmitter linearisation techniques. These techniques are typically baseband input systems (with either digital or analogue inputs) and must be employed within or around the architectures described in Chapter 5.
RF synthesis techniques. Again, these are typically baseband input systems; however, the high-power RF waveform is now formed at the output of the transmitter from high-power non-linear waveforms generated within the transmitter. Again, these must be employed within or around the architectures described in Chapter 5. Most of these techniques have yet to find widespread acceptance in software defined radio...
