Dr. S. Ramprabhu Assistant Professor Department of Electronics Engineering Madras Institute of Technology Anna University Chennai 600 044 Aperture antennas Session Meta Data
Author Dr. S. Ramprabhu
Version No 1.2
Release Date 22-09-2023
Reviewer
3 v 1.1 Revision History
Date of Revision Details Version Number
4 v 1.1 Session Objectives
To study the radiation mechanism of aperture antennas
To derive the field components
5 v 1.1 Session Outcomes
At the end of the session, students will be able to
Understand the radiation mechanism of aperture antennas Develop the radiated field equations
6 v 1.1 Aperture Antennas
7 v 1.1 What are Aperture Antennas? An Antenna with an aperture at the end can be termed as an Aperture antenna.
Waveguide is an example of aperture antenna. The edge of a
transmission line when terminated with an opening, radiates energy.
This opening which is an aperture, makes it an Aperture antenna.
The main types of aperture antennas are −
Wave guide antenna
Horn antenna
Slot antenna
8 v 1.1 Some Important Theorems
Aperture Antenna analysis using uniqueness theorem
Field equivalence principle
Duality principle
Image principle
9 v 1.1 Electric Current and Fields
10 v 1.1 Magnetic Current and Fields
11 v 1.1 Total field Component
12 v 1.1 Uniqueness Theorem
Statement: for a given set of sources and boundary conditions in a lossy medium, the solution to Maxwell’s equations is unique.
13 v 1.1 Uniqueness Theorem Consider a source-free volume V in an isotropic homogeneous medium bounded by a surface S. (E1,H1) be the fields inside it produced by a set of sources external to the volume. Now, let (E2,H2) be another possible set of fields in the volume V It can be shown that if either the tangential E or the tangential H is the same on the surface S for the two sets of solutions, the fields are identical everywhere in the volume. This is known as the uniqueness theorem.
14 v 1.1 Field Equivalence Theorem Consider a set of current sources in a homogeneous isotropic medium
producing electromagnetic fields E and H everywhere.
Enclose all the sources by a closed surface S, separating the entire
space into two parts, volume V1 containing the sources and the
volume V2 being source-free.
Let the surface S be chosen such that it is also source-free.
Let n be a unit normal to the surface drawn from V1 into V2
15 v 1.1 Field Equivalence Theorem
16 v 1.1 Field Equivalence Theorem
According to the field equivalence principle, the fields in V2 due
to the sources in volume V1 can also be generated by an equivalent set of virtual sources on surface S, given by Js = n × H and Ms = E × n where E and H are the fields on the surface S produced by the original set of sources in volume V1.
Set of virtual sources produce null fields everywhere in V1.
17 v 1.1 Types of Equivalence
18 v 1.1 Types of Equivalence
19 v 1.1 Duality Principle Duality is a consequence of the symmetry in Maxwell’s equations obtained with the introduction of the magnetic charge density, ρm, and magnetic current density, M. This is a very useful principle in obtaining the solution of a dual problem from the original solution, without having to solve it again.
20 v 1.1 Dual Quantities
21 v 1.1 Method of Images
22 v 1.1 Method of Images
23 v 1.1 Radiated Fields from Rectangular Aperture
24 v 1.1 Radiated Fields from Rectangular Aperture
25 v 1.1 Radiated Fields from Rectangular Aperture
26 v 1.1 Radiated Fields from Rectangular Aperture
27 v 1.1 Radiated Fields from Rectangular Aperture
28 v 1.1 Radiated Fields from Rectangular Aperture
29 v 1.1 Summary Learnt radiation mechanism of a Aperture antenna
