Chapter 15: Antennas and Waveguides – Tomasi Review

(Last Updated On: March 17, 2020)

Chapter 15: Antennas and Waveguides

This is the summary notes of the important terms and concepts in Chapter 15 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.


CHAPTER 15

ANTENNAS AND WAVEGUIDES


Items

Definitions

Terms

1

A metallic conductor system capable of radiating and capturing
electromagnetic energy

Antenna

2

Couples energy from a transmitter to an antenna or from
antenna to a receiver

Transmission Lines

3

A special type of transmission line that consists of a
conducting metallic tube through which high-frequency electromagnetic energy
is propagated.

Waveguide

4

Electrical energy that has escaped into free space in the form
of transverse electromagnetic waves

Radio Waves

5

The plane parallel to the mutually perpendicular lines of the
electric and magnetic fields.

Wavefront

6

The ratio of radiated to reflected energy.

Radiation Efficiency

7

Antenna wherein two conductors are spread out in a straight
line to a total length of one quarter wavelength.

Quarter Wave Antenna

8

Another name for quarter wave antenna.

Vertical Monopole or Marconi

9

A half-wave dipole.

Hertz Antenna

10

A special coupling device that can be used to direct the
transmit and receive signals and provide the necessary isolation.

Diplexer

11

A polar diagram or graph representing field strengths or power
densities at various angular positions relative to an antenna.

Radiation Pattern

12

Radiation pattern plotted in terms of electric field strength
or power density.

Absolute Radiation Pattern

13

Radiation pattern plots field strength or power density with
respect to the value at a reference

Relative Radiation

14

The primary beam of an antenna.

Major Lobes

15

The major lobes that propagates and receive the most energy.

Front Lobe

16

Lobes adjacent to the front lobe.

Side lobes

17

The secondary beam of an antenna.

Minor Lobes

18

Lobes in a direction exactly opposite the front lobe

Back Lobe

19

The ratio of the front lobe power to the back lobe power.

Front to Back Ratio

20

The ratio of the front lobe to a side lobe.

Front to Side Ratio

21

The line bisecting the major lobe, or pointing from the center
of the antenna in the direction of maximum radiation.

Line of Shoot or Point of Shoot

22

Antenna that radiates energy equally in all directions.

Omni-directional Antenna

23

Radiates power at a constant rate uniformly in all directions.

Isotropic Radiator

24

The direction in which an antenna is always pointing.

Maximum Radiation

25

It is defined as an equivalent transmits power. It stands for
Effective Isotropic Radiated Power.

EIRP

26

The equivalent power that an isotropic antenna would have to
radiate to achieve the same power density in the chosen direction at a given
point as another antenna.

Effective Radiated Power
(ERP) or (EIRP)

27

The power density in space and the actual power that a receive
antenna produces at its output terminals.

Captured Power Density

28

It describe the reception properties of an antenna

Capture Area

29

Another name for capture area.

Effective Area

30

The relationship of captured power to the received power
density and the effective capture area of the received antenna.

Directly Proportional

31

It refers to the orientation of the electric field radiated
from the antenna.

Polarization

32

The angular separation between the two half-power (-3dB)
points on the major lobe of an antenna’s plane radiation pattern.

Antenna Beamwidth

33

The frequency range over which antenna operation is
satisfactory.

Antenna Bandwidth

34

Another name for antenna input terminal

Feedpoint

35

The feedpoint presents an ac load to the transmission line.

Antenna Input Impedance

36

The simplest type of antenna.
Another names for elementary doublet
Ø  Short Dipole,
Ø  Elementary Dipole
Ø 
Hertzian
Dipole

Elementary Doublet

37

Any dipole that is less than one-tenth wavelength

Electrically Short

38

Hertz antenna is name after him and he was the first to
demonstrate the existence of electromagnetic waves.

Heinrich Hertz

39

A single pole antenna one quarter wavelength long, mounted
vertically with the lower end either connected directly to ground or grounded
through the antenna coupling network.

Marconi Antenna

40

Main disadvantage of Marconi Antenna.

Must be close to the Ground

41

A technique use to increase the electrical length of an
antenna

Loading

42

A coil added in series with a dipole antenna which effectively
increases antenna’s electrical length.

Loading Coil

43

A loading coil approximately increases the radiation
resistance of the antenna.

5 Ohms

44

An individual radiator, such as a half or quarter wave dipole.

Two types of antenna elements
Ø  Driven
Ø 
Parasitic

Two Elements of a single antenna
Ø  Two Wire
Ø 
Folded
Dipole


Antenna Element

45

Its purpose is to increase the directivity and concentrate the
radiated power within a smaller geographic area.

Array

46

Elements that are directly connected to the transmission line
and receive power from the source.

Driven

47

Elements are not connected to the transmission line; they
receive energy only through mutual induction with a driven element.

Parasitic

48

A parasitic element that is shorter that its associated driven
element.

Director

49

Radiation pattern depends on the relative phase of feeds.

Driven

50

The simplest type of antenna arrays.

Broadside Arrays

51

A widely used antenna commonly uses a folded dipole as the
driven element and named after two Japanese scientists.

Yagi Uda

52

Typical directivity of a yagi-uda antenna.

7 dB and 9 dB

53

Formed by placing two dipoles at right angles to each other.

Turnstile Antenna

54

A class of frequency-independent antennas.

Log Periodic

55

A broadband VHF or UHF antenna that is ideally suited for
applications for which radiating circular rather than horizontal or vertical
polarized electromagnetic waves are required.
Modes of propagation:
Ø  Normal
Ø 
Axial

Helical Antenna

56

Antennas having half power beamwidths on the order of 1º or
less.
Three important characteristics:
Ø  Front-to Back Ratio,
Ø  Side-to-Side Coupling
Ø 
Back-to-Back
Coupling

Microwave Antenna

57

Antenna that provides extremely high gain and directivity and
are very popular for microwave and satellite communications link.
Two main part
Ø Parabolic Reflector
Ø Feed Mechanism

Parabolic Reflector Antenna

58

The effective area in a receiving parabolic antenna and is
always less than the actual mouth area.

Capture Area

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