Chapter 2 Basics of Wireless Communications
Before we begin to talk about wireless, we briefly remind the reader of a previous acquaintance with three concepts that are ubiquitous in radio engineering: sinusoidal signals, complex numbers, and imaginary exponentials. The reader who is familiar with such matters can skip this section without harm.
Almost everything in radio is done by making tiny changes—modulations—of a signal that is periodic in time. The archetype of a smooth periodic signal is the sinusoid (Figure 2-1), typically written as the product of the angular frequency ω and time t.
Both of these functions alternate between a maximum value of 1 and minimum value of – 1; cosine starts at +1, and ...