Digital Signal Processing Techniques and Applications in Radar Image Processing

3

BASICS OF ANTENNA THEORY

The antenna is a device that radiates or receives electromagnetic waves. In general, antennas can be classified as either single-element radiators or multiple (usually identical) radiating elements. Dipoles, horns, printed patch radiators, and reflectors are considered single-element radiators. Linear, circular, and area arrays consist of multiple (usually identical) radiating elements. Antennas play a very important role in radar-related applications. In this chapter, antenna theory is reviewed, starting with the Maxwell equation in Section 3.1. The infinitesimal dipole is described in Section 3.2, and the half-wavelength dipole is covered in Section 3.3. The 1D linear phase array is briefly reviewed in Section 3.4, and the 2D linear array is discussed in Section 3.5. The key antenna-related parameters are covered in Section 3.6. Some commonly used antennas, including the microstrip antenna, are reviewed in Section 3.7.

3.1 MAXWELL AND WAVE EQUATIONS

The classical Maxwell equations serve as the fundamental basis for all electromagnetic phenomena and are shown below:

Since for any vector , the equation 0 implies the existence of , such that ; that is