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Lecture 1 “How Antenna Works” (ECE432 Lecture 1) - Fall 2025

Total questions: 70

Worksheet time: 35mins

Name
Class
Date
1.

The IEEE defines an antenna as:

a)

A wire that transmits electricity

b)

A device that stores electromagnetic energy

c)

A part of a transmitting/receiving system that radiates or receives EM waves

d)

A waveguide

2.

An antenna acts as a:

a)

Transducer between guided waves and free-space waves

b)

Transformer

c)

Oscillator

d)

Amplifier

3.

For efficient radiation, an antenna must have a physical length that is:

a)

A small fraction of the wavelength

b)

At least an appreciable fraction of the wavelength

c)

Exactly equal to the wavelength

d)

Independent of wavelength

4.

Conventional circuits do not radiate significantly because they are:

a)

At resonance

b)

Much smaller than the operating wavelength

c)

Lossless

d)

Shielded

5.

As frequency and distance increase, the preferred transmission medium is:

a)

Transmission line

b)

Optical fiber

c)

Antenna

d)

Waveguide

6.

Radiation from a dipole occurs due to:

a)

Static charges on its ends

b)

Oscillating currents producing time-varying fields

c)

Magnetic materials inside the antenna

d)

Constant voltage across the terminals

7.

At time t = 0 in a dipole cycle, what occurs?

a)

Maximum current

b)

Peak charge accumulation

c)

Minimum field strength

d)

Zero charge build-up

8.

At t = T/4, the charges in a dipole antenna are:

a)

Maximum positive at one end

b)

Completely neutralized

c)

Maximum negative at one end

d)

Oscillating in loops

9.

The conduction current on an antenna is converted into:

a)

Magnetic flux

b)

Displacement current in space

c)

Electric potential

d)

Mechanical vibration

10.

Radiation occurs because electric field lines:

a)

Remain confined near the antenna

b)

Detach and propagate outward

c)

Cancel each other

d)

Reverse direction constantly

11.

The radiation pattern of an antenna shows:

a)

Variation of current along the wire

b)

Variation of radiated field intensity with angle

c)

Frequency response

d)

Polarization only

12.

Directivity is a measure of:

a)

Losses in the antenna

b)

Concentration of radiated power in a given direction

c)

Bandwidth

d)

Matching efficiency

13.

Antenna gain is defined as:

a)

Directivity without losses

b)

Directivity reduced by antenna losses

c)

Directivity plus efficiency

d)

Input resistance

14.

Antenna polarization refers to:

a)

Direction of maximum gain

b)

Orientation of the electric field vector of the radiated wave

c)

Impedance matching

d)

Antenna efficiency

15.

The input impedance of an antenna is the ratio of:

a)

Current to voltage

b)

Voltage to current at the antenna terminals

c)

Power to current

d)

Voltage to power

16.

The usual goal of impedance matching is:

a)

To increase frequency

b)

To minimize reflection between transmission line and antenna

c)

To maximize stored energy

d)

To improve directivity only

17.

Antenna bandwidth is the range of frequencies where:

a)

Directivity is maximum

b)

Performance parameters remain acceptable

c)

Efficiency is zero

d)

The antenna resonates only

18.

Radiation efficiency is:

a)

Ratio of input power to radiated power

b)

Ratio of radiated power to input power

c)

Ratio of gain to directivity

d)

Ratio of voltage to current

19.

Electrically small antennas are:

a)

About half a wavelength long

b)

Much smaller than a wavelength

c)

Always broadband

d)

High gain

20.

Example of an electrically small antenna:

a)

Horn antenna

b)

Short dipole

c)

Yagi-Uda

d)

Microstrip patch

21.

Resonant antennas typically have:

a)

Wide bandwidth

b)

Narrow bandwidth

c)

High directivity

d)

Low efficiency

22.

A half-wave dipole is an example of a:

a)

Resonant antenna

b)

Aperture antenna

c)

Electrically small antenna

d)

Broadband antenna

23.

A microstrip patch antenna belongs to the category of:

a)

Aperture antenna

b)

Resonant antenna

c)

Broadband antenna

d)

Electrically small antenna

24.

Broadband antennas maintain:

a)

Constant gain and input impedance over wide frequency range

b)

Very high gain only at resonance

c)

Narrow bandwidth

d)

Zero polarization

25.

Examples of broadband antennas include:

a)

Spiral and log-periodic dipole array

b)

Yagi-Uda and microstrip patch

c)

Horn and reflector

d)

Short dipole and loop

26.

Aperture antennas have:

a)

No physical opening

b)

A physical aperture through which waves propagate

c)

Very low gain

d)

High reactance only

27.

Gain of aperture antennas generally:

a)

Decreases with frequency

b)

Increases with frequency

c)

Remains constant

d)

Is always zero

28.

Examples of aperture antennas are:

a)

Yagi and dipole

b)

Horn and reflector

c)

Patch and loop

d)

Spiral and log-periodic

29.

Which antenna is commonly used in AM radio reception (electrically small)?

a)

Half-wave dipole

b)

Short vertical monopole

c)

Horn antenna

d)

Log-periodic

30.

Which antenna type is best for wideband applications like TV broadcasting?

a)

Microstrip patch

b)

Spiral antenna

c)

Dipole antenna

d)

Horn antenna

31.

Which Maxwell’s law states that there are no magnetic charges?

a)

Faraday’s law

b)

Gauss’s law for magnetism

c)

Ampère’s law

d)

Continuity equation

32.

Faraday’s law relates:

a)

Divergence of B to charge density

b)

Curl of E to rate of change of B

c)

Curl of H to current density

d)

Divergence of D to magnetic charge

33.

Ampère’s law (with Maxwell’s correction) is:

a)

∇⋅B=0\nabla \cdot \mathbf{B} = 0

b)

∇×E=−∂B∂t\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}}{\partial t}

c)

∇×H=J+∂D∂t\nabla \times \mathbf{H} = \mathbf{J} + \frac{\partial \mathbf{D}}{\partial t}

d)

∇⋅D=ρv\nabla \cdot \mathbf{D} = \rho_v

34.

The continuity equation ensures:

a)

Energy conservation

b)

Charge conservation

c)

Momentum conservation

d)

Power conservation

35.

Boundary condition for H-field tangential component:

a)

Continuous everywhere

b)

Discontinuous due to surface current density

c)

Discontinuous due to volume charge

d)

Always zero

36.

Boundary condition for E-field tangential component:

a)

Continuous across all boundaries

b)

Discontinuous due to surface magnetic current

c)

Zero at any dielectric interface

d)

Constant everywhere

37.

Magnetic current density M is:

a)

A real physical quantity

b)

A fictitious mathematical concept used for symmetry

c)

A measure of magnetic charges

d)

Equal to ∇⋅B\nabla\cdot\mathbf{B}

38.

If one side of the boundary is a perfect conductor, the tangential electric field at the surface is:

a)

Maximum

b)

Zero

c)

Infinite

d)

Equal to surface current

39.

The magnetic vector potential is denoted as:

a)

Φ

b)

A

c)

F

d)

J

40.

The divergence of A is specified using:

a)

Gauss’s law

b)

Faraday’s law

c)

Lorenz condition

d)

Continuity equation

41.

The Lorenz condition helps to:

a)

Couple variables in equations

b)

Decouple variables and derive wave equation

c)

Eliminate electric field

d)

Define polarization

42.

In solving Maxwell’s equations, a point source is first solved because:

a)

It is physically realizable

b)

General sources can be modeled as superposition of point sources

c)

It eliminates fields

d)

It avoids boundary conditions

43.

A point source current has:

a)

No direction

b)

Always a z-direction component

c)

Radial direction only

d)

Undefined orientation

44.

Outward solution of the point source corresponds to:

a)

Standing wave

b)

Radiating wave

c)

Evanescent wave

d)

Reactive field

45.

The vector potential for an arbitrary current distribution is found by:

a)

Using only one point source

b)

Integrating contributions from all point sources

c)

Ignoring orientation

d)

Taking divergence only

46.

An infinitesimal current element is also called:

a)

Microstrip dipole

b)

Hertzian dipole

c)

Folded dipole

d)

Patch antenna

47.

Condition for ideal dipole approximation:

a)

Δz≫λ\Delta z \gg \lambda

b)

Δz≪λ\Delta z \ll \lambda

c)

Δz≈λ\Delta z \approx \lambda

d)

Δz=λ/2\Delta z = \lambda/2

48.

In the far-field of an ideal dipole ( r≫λr \gg \lambda ), the fields vary as:

a)

1/r21/r^2 and 1/r31/r^3

b)

1/r1/r

c)

r2r^2

d)

Constant

49.

The intrinsic impedance of free space is:

a)

50 Ω50\,\Omega

b)

120π Ω120\pi\,\Omega

c)

75 Ω75\,\Omega

d)

377/2 Ω377/2\,\Omega

50.

Near fields of an ideal dipole consist of:

a)

Radiation only

b)

Electrostatic and induction fields

c)

Magnetic only

d)

Constant power density

51.

The distance where radiated and reactive powers are equal for a dipole is:

a)

λ/2\lambda/2

b)

λ/4\lambda/4

c)

λ/(2π)\lambda/(2\pi)

d)

λ2\lambda^2

52.

A uniform line source assumes:

a)

Current distribution varies with position

b)

Current is constant along its extent

c)

Magnetic current only

d)

No electric fields

53.

An isotropic radiator is defined as:

a)

Radiates only in one direction

b)

Hypothetical antenna radiating equally in all directions

c)

Omnidirectional in one plane only

d)

Real physical dipole

54.

An omnidirectional antenna radiates:

a)

Constantly in all 3D directions

b)

Constantly in one plane

c)

Strongly in endfire direction

d)

With no main lobe

55.

A directional antenna radiates:

a)

Equally in all directions

b)

More effectively in certain directions

c)

Without polarization

d)

Constantly in a plane

56.

The E-plane is defined as:

a)

Plane containing H-field vector

b)

Plane containing E-field vector and direction of max radiation

c)

Plane perpendicular to propagation

d)

Plane of zero current

57.

The H-plane is defined as:

a)

Plane containing H-field vector and direction of max radiation

b)

Plane containing E-field vector

c)

Plane of zero field

d)

Any arbitrary plane

58.

A normalized radiation pattern is obtained by:

a)

Setting maximum field to unity

b)

Dividing by wavelength

c)

Multiplying by impedance

d)

Eliminating phase

59.

Radiation lobes include:

a)

Main, side, and back lobes

b)

Nulls only

c)

Forward and reverse currents

d)

Resonant peaks

60.

Half-power beamwidth (HPBW) is:

a)

Angle at which power falls to 50% of maximum

b)

Null-to-null width

c)

Main lobe width at full strength

d)

Side lobe angle

61.

A broadside antenna has its maximum radiation:

a)

Along the plane of the antenna

b)

Normal to the plane of the antenna

c)

In all directions

d)

In backward direction

62.

Part E – Field Regions, Radian & Steradian: The far-field region begins when phase error due to parallel ray assumption is:

a)

π/2\pi/2

b)

π/8\pi/8

c)

π\pi

d)

Zero

63.

Part E – Field Regions, Radian & Steradian: The boundary between near and far field depends on:

a)

λ/2\lambda/2

b)

Antenna dimension and wavelength

c)

Current amplitude

d)

Polarization

64.

Part E – Field Regions, Radian & Steradian: Near field region is divided into:

a)

Induction and electrostatic fields

b)

Reactive near field & radiating near field

c)

Broadside and endfire

d)

Null and lobe

65.

Part E – Field Regions, Radian & Steradian: For an ideal dipole, the reactive to radiating near field boundary is at:

a)

λ/4\lambda/4

b)

λ(2π)\lambda(2\pi)

c)

λ/2\lambda/2

d)

λ\lambda

66.

Part E – Field Regions, Radian & Steradian: A large antenna is defined as:

a)

D ≪ λ\lambda

b)

D>2.5λD > 2.5\lambda

c)

D=λ/2D = \lambda/2

d)

D=λD = \lambda

67.

Part E – Field Regions, Radian & Steradian: A small antenna has:

a)

Dimension ≫ λ\lambda

b)

Dimension ≪ λ\lambda

c)

Dimension = λ/2\lambda/2

d)

Dimension = 2λ2\lambda

68.

Part E – Field Regions, Radian & Steradian: One radian corresponds to:

a)

180∘180^\circ

b)

Angle subtended by arc length = radius

c)

1/4 of a circle

d)

360∘360^\circ

69.

Part E – Field Regions, Radian & Steradian: The total radians in a circle:

a)

π\pi

b)

2π2\pi

c)

180

d)

360

70.

Part E – Field Regions, Radian & Steradian: The total steradians in a closed sphere:

a)

2π2\pi

b)

4π4\pi

c)

180

d)

360

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