OVERVIEW

In Chapter 3, we describe the principles of simple modulation techniques and we also give a performance summary for a large class of modulated systems in a linear additive white gaussian noise (AWGN) environment. Chapter 4 deals with the characteristics of linear and non-linear microwave amplifiers. Chapter 5 features the system gain concept, and its applications are also introduced.

Now, as a well equipped reader, you should find it relatively easy to understand the principles of operation and the performance characteristics of the more sophisticated M-ary phase shift keyed (PSK) and M-ary quadrature amplitude modulated (QAM) digital radio systems presented in this chapter. Following the description of a multichannel digital radio transmitter and receiver, the theory of operation of bandwidth-efficient M-ary PSK and QAM systems is presented. These systems frequently have a spectral efficiency of 3b/s/Hz or higher. The filtering requirements and a practical optimization procedure designed to meet FCC or other regulatory constraints are described in Section 6.3. In Chapter 4 it is pointed out that microwave power amplifiers (PA) operate more efficiently in the nonlinear mode, close to saturation, which implies that in this operating mode a higher transmitted power can be obtained. Unfortunately, a non-linear amplifier causes spectral spreading; also, due to the AM to AM and AM to PM non-linearities, a P(e) degradation exists. These effects are highlighted in Section 6.4. Finally, in the last two sections of this chapter, digital radio system performance design guidelines are presented,...