11-04-2014, 12:56 PM
Antenna Array Analysis and Synthesis
[attachment=61035]
Introduction
This chapter deals with some basic aspects of array antenna analysis and synthesis. The
approach adopted involves systematic building up of concepts ultimately leading to antenna
design. Since the matter involves many aspects only the most essential ones are briefly
described. In order to understand the array analysis, first the concepts relating to retarded
potentials are introduced, followed by introduction to weighting functions for Actual Source
Antennas and Equivalent Source Antennas. These weighting functions are then related to
array factors, which are taken to be the basis for antenna analysis and subsequently for
synthesis. Initially the analysis problem is directly addressed in terms of array factor. Later
the application of Schelkunoff Unit Circle, which is related to the array factor, has been
explored. Similarly there are many approaches to synthesize an antenna array. Other aspects
of antennas that need to be addressed, viz. sum and difference patterns, beam width and
location of the main lobe, location of nulls, number, levels and locations of side lobes,
directivity of antenna, etc. Since all the above aspects cannot be addressed in a single
introductory chapter, the matter is covered only to the extent of introducing the subject.
Array Structures
An array may be defined as a collection of elements. It may be composed of large number
of elements, which may run from few to thousands and are limited by practical constraints.
The elements in an array may be Dipoles, Polyrods, Helix, Spirals, Log Periodic Struc-
tures, Slots or Horns. Dipoles and Slots generate broad band pattern, and are widely used
in simple structures. Polyrods, Helices, Spirals and Log Periodic Structures have more
directivity. Slots and Horns are used at UHF and Microwave frequencies and are easy to
construct.
[attachment=61035]
Introduction
This chapter deals with some basic aspects of array antenna analysis and synthesis. The
approach adopted involves systematic building up of concepts ultimately leading to antenna
design. Since the matter involves many aspects only the most essential ones are briefly
described. In order to understand the array analysis, first the concepts relating to retarded
potentials are introduced, followed by introduction to weighting functions for Actual Source
Antennas and Equivalent Source Antennas. These weighting functions are then related to
array factors, which are taken to be the basis for antenna analysis and subsequently for
synthesis. Initially the analysis problem is directly addressed in terms of array factor. Later
the application of Schelkunoff Unit Circle, which is related to the array factor, has been
explored. Similarly there are many approaches to synthesize an antenna array. Other aspects
of antennas that need to be addressed, viz. sum and difference patterns, beam width and
location of the main lobe, location of nulls, number, levels and locations of side lobes,
directivity of antenna, etc. Since all the above aspects cannot be addressed in a single
introductory chapter, the matter is covered only to the extent of introducing the subject.
Array Structures
An array may be defined as a collection of elements. It may be composed of large number
of elements, which may run from few to thousands and are limited by practical constraints.
The elements in an array may be Dipoles, Polyrods, Helix, Spirals, Log Periodic Struc-
tures, Slots or Horns. Dipoles and Slots generate broad band pattern, and are widely used
in simple structures. Polyrods, Helices, Spirals and Log Periodic Structures have more
directivity. Slots and Horns are used at UHF and Microwave frequencies and are easy to
construct.