In this chapter we review some of the basic concepts in communication systems. We will start with a brief summary of Fourier and Hilbert transforms, both of which serve as great tools to analyze RF circuits and systems. We will also present an overview of RF filters, both the real and complex domain structures, and discuss quadrature signal generation. To establish some foundation for the noise analysis presented in Chapter 4, we will also provide a summary of stochastic processes and random variables. We conclude this chapter by briefly describing the fundamentals of analog modulation schemes and analog modulators.
The majority of the material presented in this chapter is a review of various concepts that exist in signal processing, communication systems, and basic circuit theory. However, we feel it is important to present a reminder as well as a summary as throughout this book they will be referred to frequently.
The specific topics covered in this chapter are:
• Fourier series and Fourier transform;
• impulse response, poles, zeros, and network functions;
• passive and active filters;
• Hilbert transforms, polyphase filters, and quadrature signals;
• random processes, Gaussian signals, stationary and cyclostationary processes;
• amplitude, phase, and frequency modulation;
• narrowband FM and Bessel functions;
• introduction to modern digital communication.
For class teaching, we recommend focusing on selected topics from Sections 2.3, 2.5, 2.7, 2.8, and 2.9 while Sections 2.1, 2.2, and 2.4 may be comfortably assigned as reading.
Stochastic processes (Section 2.6) are crucial to attain a thorough understanding of noise in RF circuits, and particularly oscillator phase noise. For an introductory RF course, however, proper coverage of noise and phase noise may not be feasible. Consequently we defer Section 2.6 and the majority of phase noise discussion (in Chapter 8) to a more advanced course, and certainly the more astute readers. What Section 2.6 offers is a summary of selected topics that are most relevant to RF design, which will greatly complement our discussions on mixer and oscillator noise.