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ECE141 > Chapter 7 & 8 - Tomasi > Flashcards

Chapter 7 & 8 - Tomasi 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 () 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

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

A

Phase Deviation

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8
Q

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

A

Frequency Deviation

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9
Q

The original unmodulated carrier frequency in the resultant angle-modulated waveform.

A

Carrier Rests Frequency

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10
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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11
Q

Is called the modulation index or sometimes index of modulation.

A

Peak Phase Modulation

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12
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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13
Q

The peak-to-peak frequency deviation (2f).

A

Carrier Swing

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14
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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15
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

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16
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

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17
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

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18
Q

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

A

200 kHz

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19
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

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20
Q

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

A

Pre-emphasis

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21
Q

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

A

De-emphasis

22
Q

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

A

Direct FM

Indirect PM

23
Q

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

A

Direct PM

Indirect FM

24
Q

Three common methods for producing direct frequency modulation.

A

Varactor Diode,
FM Reactance,
Linear IC Modulations

25
Q

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

A

MC1376

26
Q

Two common methods for producing direct phase modulation.

A

Varactor Diode and Transistor Direct PM Modulator

27
Q

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

A

Frequency Up-Conversion

28
Q

Two basic methods of performing frequency up-conversion.

A

Heterodyning and Frequency Multiplication

29
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

30
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

31
Q

What does AFC stands for?

A

Automatic Frequency Control

32
Q

A circuit that compares the frequency of he 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

33
Q

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

A

Frequency Discriminator

34
Q

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

A

Noise Immunity

35
Q

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

A

Capture Effect

36
Q

A method used to remove amplitude variations caused by noise from the composite waveform simply by clipping the peaks of the envelop prior to detection.

A

Limiting

37
Q

The section that establishes the signal-to-noise ratio and noise figure in FM receivers.

A

RF Amplifier

38
Q

The envelope (peak) detector common to AM receivers is replaced in FM receivers by a ________, ________, and ________.

A

Limiter,
Frequency Discriminator and
De-emphasis Network

39
Q

The circuit that extracts the information from the modulated wave.

A

Frequency Discriminator

40
Q

This FM demodulator requires no tuned circuits and automatically compensates for changes in the carrier frequency due to instability in the transmit oscillator.

A

PLL FM Demodulator

41
Q

The limiter circuit produces a constant-amplitude output for all input signals above a prescribed minimum input level, which is often
called the ________.

A

Threshold,
Quieting, or
Capture Level

42
Q

The improvement in the S/N ratio when the peaks of the signal have the limiter so far into saturation that the weaker noise is totally eliminated.

A

FM Thresholding, FM Quieting, or

FM Capture Effect

43
Q

The inherent ability of FM to diminish the effects of interfering signals. Also, the ability to differentiate between two signals received at the same frequency.

A

Capture Effect

44
Q

A circuit that is used to reduce the total harmonic distortion (THD) by compressing the IF frequency swing (deviation).

A

Frequency-Locked-Loop

45
Q

The amount an FM carrier frequency deviates for a given modulating input voltage level is called the ________.

A

Deviation Sensitivity

46
Q

Are used to multiply the frequency of the carrier signal of an FM signal, consist of a class C amplifier followed by a tank circuit that filters out a single harmonic, and are used to multiply the frequency deviation of an FM signal

A

Frequency Multipliers

47
Q

Another way to describe the modulation index is using the _________.

A

Deviation Ratio

48
Q

The input signal into a PLL is at the ________.

A

Phase Detector

49
Q

FM with less than or equal to 0.3 of modulation index is referred to as ______.

A

Narrow Band FM

50
Q

FM with greater than 0.3 of modulation index is referred to as ______.

A

Wide Band FM

ECE141 (3 decks)

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