Angle Modulation Transmissions (Chapter 7)

Question 1

Two forms of angle modulation.

Answer 1

FM and PM

Question 2

Angle modulation was first introduced in the year ________ as
an alternative to amplitude modulation.

Answer 2

1931

Question 3

He developed the first successful FM radio system in 1936, and
in July 1939, the first regularly scheduled broad-casting of FM signals began
in Alphine, New Jersey. Also developed the superheterodyne receiver.

Answer 3

Major E. H. Armstrong

Question 4

A modulation that results whenever the phase angle (θ) of

a sinusoidal wave is varied with respect to time.

Answer 4

Angle Modulation

Question 5

Varying the frequency of a constant-amplitude carrier directly
proportional to the amplitude of the modulating signal at a rate equal to the
frequency of the modulating signal.

Answer 5

Direct Frequency Modulation ( FM )

Question 6

Varying the phase of a constant-amplitude carrier directly
proportional to the amplitude of the modulating signal at a rate equal to the
frequency of the modulating signal.

Answer 6

Direct Phase Modulation ( PM )

Question 7

Direct FM is Direct Pm. True or False?

Answer 7

False

Question 8

The relative angular displacement (shift) of the carrier phase
in radians in respect to the reference phase.

Answer 8

Phase Deviation (Δθ )

Question 9

The relative displacement of the carrier frequency in hertz in
respect to its unmodulated value.

Answer 9

Frequency Deviation (ΔF )

Question 10

The original unmodulated carrier frequency in the resultant

angle-modulated waveform.

Answer 10

Carrier Rests Frequency

Question 11

The instantaneous change in the phase of the carrier at a
given instant of time and indicates how much the phase of the carrier is
changing with respect to its reference phase.

Answer 11

Instantaneous Phase Deviation

Question 12

The precise phase of the carrier at a given instant of time.

Answer 12

Instantaneous Phase

Question 13

The instantaneous change in frequency of the carrier and is

defined as the first time derivative of the instantaneous phase deviation.

Answer 13

Instantaneous Frequency Deviation

Question 14

The precise frequency of the carrier at a given instant of

time and is defined as the first time derivative of the instantaneous phase.

Answer 14

Instantaneous Frequency

Question 15

Are the output–versus-input transfer functions for the
modulators, which give the relationship between what output parameter changes
in respect to specified changes in the input signal.

Answer 15

Deviation Sensitivities

Question 16

Is called the modulation index or sometimes index of

modulation.

Answer 16

Peak Phase Modulation

Question 17

The change in frequency that occurs in the carrier when it is
acted on by a modulating-signal frequency.

Answer 17

Frequency Deviation

Question 18

The peak-to-peak frequency deviation (2Δf).

Answer 18

Carrier Swing

Question 19

The ratio of the frequency deviation actually produced to the
maximum frequency deviation allowed by law stated in percent form.

Answer 19

Percent Modulation

Question 20

A circuit in which the carrier is varied in such a way that

its instantaneous phase is proportional to the modulating signal.

Answer 20

Phase Modulator

Question 21

A circuit which the carrier is varied in such a way that its

instantaneous phase is proportional to the integral of the modulating signal.

Answer 21

Frequency Modulator

Question 22

________ of the first kind for several values of modulation
index provides the number of side frequency pairs and their corresponding
magnitude.

Answer 22

Bessel Function

Question 23

A side frequency is not considered significant unless it has

amplitude equal to or greater than ____ of the unmodulated carrier amplitude.

Answer 23

1%

Question 24

The modulation index is less than 1.

Answer 24

Low-index Case

Question 25

The modulation index is greater than 10.

Answer 25

High-index Case

Question 26

Modulation indices greater than 1 and less than 10.

Answer 26

Medium Index

Question 27

Low-index FM systems are sometimes called?

Answer 27

Narrowband FM

Question 28

A rule which is an approximation and gives transmission bandwidths that are slightly narrower than the bandwidths. It defines a bandwidth that includes approximately 98% of the total power in the modulated wave.

Answer 28

Carson’s Rule

Question 29

The worst-case modulation index and is equal to the maximum | peak frequency deviation divided by the maximum modulating-signal frequency.

Answer 29

Deviation Ratio ( DR )

Question 30

The FCC has assigned the commercial FM broadcast service a | _______ band of frequencies that extends from 88 MHz to 108 MHZ.

Answer 30

20 MHz

Question 31

The 20–MHz band is divided into 100, ________ wide channels | beginning at 88.1 MHz.

Answer 31

200 kHz

Question 32

To provide high-quality, reliable music, the maximum frequency deviation allowed is _______ with a maximum modulating-signal frequency of _______.

Answer 32

75 kHz ; 15 kHz

Question 33

The highest side frequencies from one channel are allowed to spill over into adjacent channels, producing an interference known as _______.

Answer 33

Adjacent Channel Interference

Question 34

A _______ wide guard band is usually on either side of each | assigned channel.

Answer 34

200 kHz

Question 35

The noise voltage at the output of an FM demodulator increases linearly with frequency. This is called ______.

Answer 35

FM Noise Triangle

Question 36

The high-frequency modulating signals are emphasized or | boosted in amplitude in the transmitter prior to performing modulation.

Answer 36

Pre-emphasis

Question 37

The reciprocal of pre-emphasis that restores the original | amplitude-versus-frequency characteristics to the information signals.

Answer 37

De-emphasis

Question 38

A circuit that provides a constant increase in the amplitude | of the modulating signal with an increase in frequency.

Answer 38

Pre-emphasis Network

Question 39

When the frequency of the carrier is modulated by the information signal, _______ results.

Answer 39

Direct FM ( Indirect PM )

Question 40

When the phase of the carrier is modulated by the information signal, _______ results.

Answer 40

Direct PM ( Indirect FM )

Question 41

Angle modulation in which the frequency of the carrier is | varied directly by the modulating signal.

Answer 41

Direct FM

Question 42

Three common methods for producing direct frequency | modulation.

Answer 42

Varactor Diode, FM Reactance, Linear IC | Modulations

Question 43

Direct frequency modulator used for low-index Applications, | such as two-way mobile radio.

Answer 43

Varactor Diode Direct FM Modulator

Question 44

A direct FM modulator using a JFET as the active device.

Answer 44

FM Reactance Modulator

Question 45

A complete FM modulator on a single 8-pin DIP integrated | circuit chip.

Answer 45

MC1376

Question 46

Can generate a direct FM output waveform that is relatively | stable, accurate, and directly proportional to the input modulating signal.

Answer 46

Linear IC VCO and Function Generators

Question 47

Angle modulation in which the frequency of the carrier is | deviated indirectly by the modulating signal.

Answer 47

Direct PM

Question 48

Two common methods for producing direct phase modulation.

Answer 48

Varactor Diode and Transistor Direct PM | Modulator

Question 49

The process of up-converting the frequency of the modulated | carrier after modulation has been performed.

Answer 49

Frequency Up-Conversion

Question 50

Two basic methods of performing frequency up-conversion.

Answer 50

Heterodyning and Frequency Multiplication

Question 51

An up-conversion method where a low-frequency modulated carrier can either be up- or down-converted to a different location in the frequency spectrum without changing its modulation properties.

Answer 51

Heterodyne Method

Question 52

An up-conversion method where the modulation properties of a carrier can be increased at the same time that the carrier frequency is up-converted.

Answer 52

Multiplication Method

Question 53

Transmitters that produce an output waveform in which the | frequency deviation is directly proportional to the modulating signal.

Answer 53

Direct FM Transmitters

Question 54

A circuit that compares the frequency of the non-crystal carrier oscillator to a crystal reference oscillator and then produces a correction voltage proportional to the difference between the frequencies.

Answer 54

Automatic Frequency Control ( AFC )

Question 55

A frequency-selective device whose output voltage is proportional to the difference between the input frequency and its resonant frequency.

Answer 55

Frequency Discriminator

Question 56

A voltage added to the modulating signal to automatically adjust the master oscillator’s center frequency to compensate for the low-frequency drift.

Answer 56

dc Correction Voltage

Question 57

A ________ preceded by a differentiator generates a PM | waveform.

Answer 57

FM Modulator

Question 58

Transmitters that produce an output waveform in which phase | deviation is directly proportional to the modulating signal.

Answer 58

Indirect FM Transmitters

Question 59

Probably the most significant advantage of angle modulation | transmission over amplitude modulation transmission.

Answer 59

Noise Immunity

Question 60

Allows a receiver to differentiate between two signals | received with the same frequency.

Answer 60

Capture Effect

Question 61

Proportional to the amplitude, not the frequency, of the modulating signal.

Answer 61

Frequency Modulation

Question 62

it is the phase shift, rather than the frequency deviation, that is proportional to the instantaneous amplitude of the modulating signal.

Answer 62

Phase Modulation

Question 63

In FM and PM, the frequency deviation is _______ to the amplitude of the modulating signal.

Answer 63

directly proportional

Question 64

In PM, the maximum leading or lagging phase shift occurs at the _______ of the modulating signal

Answer 64

peak amplitudes

Question 65

In PM, the carrier deviation is _______ to both the modulating frequency and the amplitude, independent to frequency.

Answer 65

proportional

Question 66

It is the rate of change of phase (which is the derivative of phase)

Answer 66

Frequency (radians per second)