Chapter 7 & 8 - Tomasi

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 () 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

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

Answer 7

Phase Deviation

Question 8

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

Answer 8

Frequency Deviation

Question 9

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

Answer 9

Carrier Rests Frequency

Question 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.

Answer 10

Deviation Sensitivities

Question 11

Is called the modulation index or sometimes index of modulation.

Answer 11

Peak Phase Modulation

Question 12

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

Answer 12

Frequency Deviation

Question 13

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

Answer 13

Carrier Swing

Question 14

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

Answer 14

Percent Modulation

Question 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.

Answer 15

Carson’s Rule

Question 16

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

Answer 16

Deviation Ratio

Question 17

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

Answer 17

20 MHz

Question 18

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

Answer 18

200 kHz

Question 19

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

Answer 19

75 kHz ;

15 kHz

Question 20

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

Answer 20

Pre-emphasis

Question 21

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

Answer 21

De-emphasis

Question 22

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

Answer 22

Direct FM

Indirect PM

Question 23

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

Answer 23

Direct PM

Indirect FM

Question 24

Three common methods for producing direct frequency modulation.

Answer 24

Varactor Diode,
FM Reactance,
Linear IC Modulations

Question 25

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

Answer 25

MC1376

Question 26

Two common methods for producing direct phase modulation.

Answer 26

Varactor Diode and Transistor Direct PM Modulator

Question 27

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

Answer 27

Frequency Up-Conversion

Question 28

Two basic methods of performing frequency up-conversion.

Answer 28

Heterodyning and Frequency Multiplication

Question 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.

Answer 29

Heterodyne Method

Question 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.

Answer 30

Multiplication Method

Question 31

What does AFC stands for?

Answer 31

Automatic Frequency Control

Question 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.

Answer 32

Automatic Frequency Control | AFC

Question 33

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

Answer 33

Frequency Discriminator

Question 34

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

Answer 34

Noise Immunity

Question 35

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

Answer 35

Capture Effect

Question 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.

Answer 36

Limiting

Question 37

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

Answer 37

RF Amplifier

Question 38

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

Answer 38

Limiter, Frequency Discriminator and De-emphasis Network

Question 39

The circuit that extracts the information from the modulated wave.

Answer 39

Frequency Discriminator

Question 40

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

Answer 40

PLL FM Demodulator

Question 41

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

Answer 41

Threshold, Quieting, or Capture Level

Question 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.

Answer 42

FM Thresholding, FM Quieting, or | FM Capture Effect

Question 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.

Answer 43

Capture Effect

Question 44

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

Answer 44

Frequency-Locked-Loop

Question 45

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

Answer 45

Deviation Sensitivity

Question 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

Answer 46

Frequency Multipliers

Question 47

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

Answer 47

Deviation Ratio

Question 48

The input signal into a PLL is at the ________.

Answer 48

Phase Detector

Question 49

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

Answer 49

Narrow Band FM

Question 50

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

Answer 50

Wide Band FM