Overview

This introductory discussion of radar is divided into three broad topics:

• How radar waves are generated and transmitted;

• How radar waves interact with external objects and return to the radar;

• How (fundamentally) the returned signals are processed to yield interesting information.

Those topics are discussed in Chapters 2, 3, and 4, respectively. This chapter focuses on generating radar waves, sending them outside the radar hardware through the antenna, and receiving and digitizing the returned echoes.

2.1 Fourier Transforms

This book frequently refers to Fourier transforms (FTs). Details of FTs can be found in many references. An extremely abbreviated summary (from Brigham [1]) is as follows. Consider a voltage signal that is a continuous function of time; s(t) is the signal as expressed in the time domain. Joseph Fourier (1768 1830) showed that we can also consider such a signal as the sum of a (finite or infinite) number of signals, each at a different frequency with a particular amplitude. Thus we can express the same signal in the frequency domain as S(f). If s(t) is a uniform tone at frequency f ₀ , S(f) is zero everywhere except at f ₀ , at which it is a spike; that is known as a delta function (see Section 4.2.1 for a discussion of positive and negative frequencies). If s(t) is band limited, that is, contains frequencies only within B/2 of f ₀ , then S(f)