Page 42 - Fundamentals of Communications Systems

1.8 Chapter One

The first chapter of this part of the book covers material that is included in the
core undergraduate electrical engineering curriculum that provides the theory
for the operation for the oscilloscope (time domain characterizations of signals)
and the theory for the operation of the spectrum analyzer (frequency domain
characterization of signals). The fundamental difference between a communi-
cation engineer and a technician is that engineers will consider noise to provide
a complete characterization of the system trade-offs. The tools used to charac-
terize noise are based on probability theory. The second chapter reviews this
material. Courses covering the material on signal and systems and probability
theory are taken before a course in communication theory. These two chapters
are included strictly as review and to establish notation for the remainder of
the book. The chapter on bandpass signals and the complex envelope notation
is where the student steps into modern communication systems theory. This
chapter will teach students how to characterize bandpass signals in the time
domain and in the frequency domain. This chapter also introduces the vector di-
agram, the theoretical basis of the vector signal analyzer. This tool is frequently
used by the modern communication engineer. These mathematical foundations
will provide the basis for communications engineering.

1.5.2 Analog Communication
This part of the book consists of four chapters that introduce the theory of
bandpass analog communication. The approach taken here is to introduce ana-
log communications before the concepts of random processes. Consequently, the
message signal is treated as a known deterministic waveform in the discussion
of analog communications. The downside of this approach is that many of the
powerful results on the power spectrum of analog communication waveforms
cannot be introduced. The advantage of this approach is that since the message
signals are known and deterministic, the tools of Fourier series, Fourier trans-
forms, and signals and systems can be applied to the understanding of analog
modulation systems. This approach allows students to ease into the world of
communications by building upon their prior knowledge in deterministic sig-
nal and system analysis. By tying these tools from early undergraduate courses
into the process of assessing the spectral efficiency and complexity of analog
communications, the student will see the efficacy of an education in the fun-
damentals of electrical engineering. The first chapter of this part of the book
presents the performance metrics in communications: performance, complex-
ity, and spectral efficiency. This three-level trade-off is a recurring theme in the
book. The following chapters introduce the classic methods of communicating
analog information; amplitude and angle modulation. Amplitude modulation
is a modulation format where the message signal is impressed upon the am-
plitude of the bandpass signal. Similarly, angle modulation is a modulation
format where the message signal is impressed in some way in the phase of
the bandpass signal. Finally, the important ideas in analog communications of
multiplexing and the phase-locked loop are presented.