Chapter 7 & 8 - Tomasi Flashcards Preview

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Flashcards in Chapter 7 & 8 - Tomasi Deck (50):
1

Two forms of angle modulation.

FM and PM

2

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

1931

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.

Major E. H. Armstrong

4

A modulation that results whenever the phase angle () of a sinusoidal wave is varied with respect to time.

Angle Modulation

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.

Direct Frequency Modulation
( FM )

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.

Direct Phase Modulation
( PM )

7

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

Phase Deviation

8

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

Frequency Deviation

9

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

Carrier Rests Frequency

10

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.

Deviation Sensitivities

11

Is called the modulation index or sometimes index of modulation.

Peak Phase Modulation

12

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

Frequency Deviation

13

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

Carrier Swing

14

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

Percent Modulation

15

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.

Carson’s Rule

16

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

Deviation Ratio

17

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

20 MHz

18

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

200 kHz

19

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

75 kHz ;
15 kHz

20

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

Pre-emphasis

21

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

De-emphasis

22

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

Direct FM
( Indirect PM )

23

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

Direct PM
( Indirect FM )

24

Three common methods for producing direct frequency modulation.

Varactor Diode,
FM Reactance,
Linear IC Modulations

25

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

MC1376

26

Two common methods for producing direct phase modulation.

Varactor Diode and Transistor Direct PM Modulator

27

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

Frequency Up-Conversion

28

Two basic methods of performing frequency up-conversion.

Heterodyning and Frequency Multiplication

29

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.

Heterodyne Method

30

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.

Multiplication Method

31

What does AFC stands for?

Automatic Frequency Control

32

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.

Automatic Frequency Control
( AFC )

33

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

Frequency Discriminator

34

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

Noise Immunity

35

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

Capture Effect

36

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.

Limiting

37

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

RF Amplifier

38

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

Limiter,
Frequency Discriminator and
De-emphasis Network

39

The circuit that extracts the information from the modulated wave.

Frequency Discriminator

40

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

PLL FM Demodulator

41

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

Threshold,
Quieting, or
Capture Level

42

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.

FM Thresholding, FM Quieting, or
FM Capture Effect

43

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.

Capture Effect

44

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

Frequency-Locked-Loop

45

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

Deviation Sensitivity

46

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

Frequency Multipliers

47

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

Deviation Ratio

48

The input signal into a PLL is at the ________.

Phase Detector

49

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

Narrow Band FM

50

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

Wide Band FM