TABLE OF CONTENTS Phased array antennas consist of multiple stationary antenna elements, which are fed coherently and use variable phase or time-delay control at each element to scan a beam to given angles in space. Variable amplitude control is sometimes also provided for pattern shaping. Arrays are sometimes used in place of fixed aperture antennas (reflectors, lenses), because the multiplicity of elements allows more precise control of the radiation pattern, thus resulting in lower sidelobes or careful pattern shaping. However, the primary reason for using arrays is to produce a directive beam that can be repositioned (scanned) electronically. Although arrays with fixed (stationary) beams and multiple stationary beams will be discussed in this text, the primary emphasis will be on those arrays that are scanned electronically.
The radar or communication system designer sees the array antenna as a component (with measurable input and output) and a set of specifications. The array designer sees the details of the array and the physical and electrical limitations imposed by the radar or communications system, and within those constraints seeks to optimize the design. This chapter is written from the perspective of, and for, the system designer. The remainder of the text discusses array design issues.
In accordance with the principle of power conservation, the radiated power density in watts/square meter at a distance R from a transmitter with an omnidirectional antenna is given by
where P rad is the total radiated power (watts), and...
