The purpose of this chapter is to summarize the results of antenna and radome technology which are of particular interest for antenna stealth. Shape is everything when it comes to both the active and passive signatures of antennas and radomes. Once the shape is right then things such as element pattern, amplitude weighting, thickness, and edge treatment become important. First, the relationship between the radiation pattern (beamwidth, side-lobes, etc.) and the current distribution across the antenna aperture is discussed. This is followed by descriptions of the various types of antennas which have been applied to radar and datalinks, including reflectors, lenses, and arrays. Several methods of pattern synthesis are discussed. The effect of broadband signals and errors in the aperture distribution on the radiation and RCS patterns is also considered. This chapter covers both the active and passive signatures of antennas and radomes. The chapter concludes with brief discussions of radome and antenna near field interaction.

Chapter Contents:

• 7.1 Introduction
• 7.2 Antenna parameters
• 7.2.1 Fundamental definitions (adapted from Skolnik and Silver)
• 7.2.2 Antenna radiation pattern and aperture distribution
• 7.3 Single radiators
• 7.3.1 The electric dipole (adapted from Radiation Laboratories)
• 7.3.2 The magnetic dipole or small loop
• 7.3.3 Slot radiators (Adapted from Blass)
• 7.3.3.1 Small rectangular slot in infinite ground plane
• 7.3.3.2 Near half-wave radiating slot in infinite ground plane
• 7.3.3.3 Slot near field
• 7.3.4 Broadband radiators
• 7.4 Antenna arrays
• 7.4.1 Simple apertures
• 7.4.2 Sidelobe reduction functions
• 7.4.3 Error induced antenna pattern degradation
• 7.4.4 Arrays of elements
• 7.5 Electronically scanned arrays
• 7.5.1 Single beam antennas
• 7.5.2 Multibeam antennas
• 7.5.3 Active electronic scan antennas
• 7.5.4 AESA antenna example
• 7.5.5 AESA bandwidth and pulse compression
• 7.5.6 AESA exciter
• 7.5.7 AESA unique noise contributions
• 7.6 Multichannel receivers
• 7.6.1 Receiver noise sources: thermal noise
• 7.6.2 Thermal noise example
• 7.7 Antenna scattering
• 7.7.1 Basic notions
• 7.7.2 Estimating antenna RCS
• 7.7.3 Estimating AESA RCS
• 7.7.4 Estimating errors due to circuit variations
• 7.8 Low RCS radomes
• 7.8.1 Introduction
• 7.8.2 Antenna and radome integration
• 7.8.3 General formulas
• 7.8.4 Composite radomes
• 7.8.5 Thick frequency-selective layers
• 7.8.6 Edge treatment
• 7.8.7 Coordinate rotations
• 7.8.8 Radome and antenna RCS
• 7.9 Exercises
• References

Inspec keywords: military radar; radar theory; antenna radiation patterns; aperture antennas; antenna theory; passive radar; active antenna arrays; military equipment; radomes; radar antennas

Other keywords: amplitude weighting; RCS patterns; pattern synthesis; beamwidth; shape thickness; antenna technology; active radomes signature; edge treatment; passive radomes signature; antenna aperture; radome technology; aperture distribution errors; stealth radomes; broadband signals; reflectors; side-lobes; stealth antennas; RF stealth; element pattern; near field interaction; datalinks; passive antennas signature; active antennas signature; radar antennas; antenna stealth; radiation pattern; arrays; lenses

Subjects: Antenna accessories; Antenna arrays; Radar equipment, systems and applications; Radar theory; Radar and radiowave systems (military and defence); Antenna theory