7.1 Introduction

This chapter examines methods of controlling RCS and the tradeoffs involved in implementing these methods. Radar cross section reduction techniques generally fall into one of four categories: 1) target shaping, 2) materials selection and coatings, 3) passive cancellation, and 4) active cancellation.

Application of each of these methods involves a compromise in performance in other areas. For instance, there are limitations to modification of an aircraft s shape from the aerodynamic optimum. Sharply angled facets may be desirable from an RCS perspective, but they degrade the aircraft s maneuverability and handling characteristics. Until recently reduction methods also tended to be narrowband and effective only over limited spatial regions. They must be chosen based on the platform s missions and expected threats. Reduction methods are applied to maintain the RCS below a specified threshold level over a range of frequencies and angles.

The next several sections examine the advantages and disadvantages of each of the four methods. The final section discusses RCS synthesis and inverse scattering; that is, given a target s scattered field, what must its composition be to achieve the specified RCS? The prescription for this problem is the RCS designer s dream. In principle, a solution to this problem can be formulated in terms of integral or differential equations. Unfortunately, solving the integral equations is practical in only the simplest cases.

7.2 Target Shaping