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EST (Electronics System and Technologies) > Angle Modulation Transmissions (Chapter 7) > Flashcards

Angle Modulation Transmissions (Chapter 7) Flashcards

1
Q

Two forms of angle modulation.

A

FM and PM

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2
Q

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

A

1931

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3
Q

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.

A

Major E. H. Armstrong

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4
Q

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

a sinusoidal wave is varied with respect to time.

A

Angle Modulation

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5
Q

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.

A

Direct Frequency Modulation ( FM )

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6
Q

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.

A

Direct Phase Modulation ( PM )

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7
Q

Direct FM is Direct Pm. True or False?

A

False

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8
Q

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

A

Phase Deviation (Δθ )

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9
Q

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

A

Frequency Deviation (ΔF )

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10
Q

The original unmodulated carrier frequency in the resultant

angle-modulated waveform.

A

Carrier Rests Frequency

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11
Q

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.

A

Instantaneous Phase Deviation

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12
Q

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

A

Instantaneous Phase

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13
Q

The instantaneous change in frequency of the carrier and is

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

A

Instantaneous Frequency Deviation

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14
Q

The precise frequency of the carrier at a given instant of

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

A

Instantaneous Frequency

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15
Q

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.

A

Deviation Sensitivities

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16
Q

Is called the modulation index or sometimes index of

modulation.

A

Peak Phase Modulation

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17
Q

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

A

Frequency Deviation

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18
Q

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

A

Carrier Swing

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19
Q

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

A

Percent Modulation

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20
Q

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

its instantaneous phase is proportional to the modulating signal.

A

Phase Modulator

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21
Q

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

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

A

Frequency Modulator

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22
Q

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

A

Bessel Function

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23
Q

A side frequency is not considered significant unless it has

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

A

1%

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24
Q

The modulation index is less than 1.

A

Low-index Case

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25
Q

The modulation index is greater than 10.

A

High-index Case

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26
Q

Modulation indices greater than 1 and less than 10.

A

Medium Index

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27
Q

Low-index FM systems are sometimes called?

A

Narrowband FM

28
Q

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.

A

Carson’s Rule

29
Q

The worst-case modulation index and is equal to the maximum

peak frequency deviation divided by the maximum modulating-signal frequency.

A

Deviation Ratio ( DR )

30
Q

The FCC has assigned the commercial FM broadcast service a

_______ band of frequencies that extends from 88 MHz to 108 MHZ.

A

20 MHz

31
Q

The 20–MHz band is divided into 100, ________ wide channels

beginning at 88.1 MHz.

A

200 kHz

32
Q

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

A

75 kHz ; 15 kHz

33
Q

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

A

Adjacent Channel Interference

34
Q

A _______ wide guard band is usually on either side of each

assigned channel.

A

200 kHz

35
Q

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

A

FM Noise Triangle

36
Q

The high-frequency modulating signals are emphasized or

boosted in amplitude in the transmitter prior to performing modulation.

A

Pre-emphasis

37
Q

The reciprocal of pre-emphasis that restores the original

amplitude-versus-frequency characteristics to the information signals.

A

De-emphasis

38
Q

A circuit that provides a constant increase in the amplitude

of the modulating signal with an increase in frequency.

A

Pre-emphasis Network

39
Q

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

A

Direct FM ( Indirect PM )

40
Q

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

A

Direct PM ( Indirect FM )

41
Q

Angle modulation in which the frequency of the carrier is

varied directly by the modulating signal.

A

Direct FM

42
Q

Three common methods for producing direct frequency

modulation.

A

Varactor Diode, FM Reactance, Linear IC

Modulations

43
Q

Direct frequency modulator used for low-index Applications,

such as two-way mobile radio.

A

Varactor Diode Direct FM Modulator

44
Q

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

A

FM Reactance Modulator

45
Q

A complete FM modulator on a single 8-pin DIP integrated

circuit chip.

A

MC1376

46
Q

Can generate a direct FM output waveform that is relatively

stable, accurate, and directly proportional to the input modulating signal.

A

Linear IC VCO and Function Generators

47
Q

Angle modulation in which the frequency of the carrier is

deviated indirectly by the modulating signal.

A

Direct PM

48
Q

Two common methods for producing direct phase modulation.

A

Varactor Diode and Transistor Direct PM

Modulator

49
Q

The process of up-converting the frequency of the modulated

carrier after modulation has been performed.

A

Frequency Up-Conversion

50
Q

Two basic methods of performing frequency up-conversion.

A

Heterodyning and Frequency Multiplication

51
Q

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.

A

Heterodyne Method

52
Q

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.

A

Multiplication Method

53
Q

Transmitters that produce an output waveform in which the

frequency deviation is directly proportional to the modulating signal.

A

Direct FM Transmitters

54
Q

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.

A

Automatic Frequency
Control
( AFC )

55
Q

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

A

Frequency Discriminator

56
Q

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

A

dc Correction Voltage

57
Q

A ________ preceded by a differentiator generates a PM

waveform.

A

FM Modulator

58
Q

Transmitters that produce an output waveform in which phase

deviation is directly proportional to the modulating signal.

A

Indirect FM Transmitters

59
Q

Probably the most significant advantage of angle modulation

transmission over amplitude modulation transmission.

A

Noise Immunity

60
Q

Allows a receiver to differentiate between two signals

received with the same frequency.

A

Capture Effect

61
Q

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

A

Frequency Modulation

62
Q

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

A

Phase Modulation

63
Q

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

A

directly proportional

64
Q

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

A

peak amplitudes

65
Q

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

A

proportional

66
Q

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

A

Frequency (radians per second)

EST (Electronics System and Technologies) (4 decks)

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