Amplitude Modulation Transmission (Chapter 4) Flashcards
It is the process of changing the amplitude of relatively high frequency carrier signal in proportion with the instantaneous value of the modulating signal.
Amplitude Modulation (AM)
It is a relatively inexpensive, low quality form of modulation that is used for commercial broadcasting of both audio and video signals. It is also used for for two-way mobile radio communications, such as Citizens band radio
Amplitude Modulation (AM)
These are nonlinear devices with two inputs and one output
AM modulators
What are frequencies tht are high enough to be efficiently radiated by an antenna and propagated through free space?
Radio Frequencies
The modulated output waveform from an AM modulator is often called an _______
AM envelope
The most commonly used amplitude modulation
Double-Sideband Full Carrier (DSBFC)
In Amplitude Modulation, if there is no modulating signal, the output waveform is simply the carrier signal. True or False?
True
For AM, the repitition rate of the envelope is _______ to the freqeuncy of the modulating signal
Equal
The process of impressing low-frequency information signals
onto a high-frequency carrier signal.
Modulation
The reverse process of modulation where the received signals
are transformed back to their original form.
Demodulation
Sometimes called conventional AM or simply AM.
AM DSBFC
The band of frequencies between fc – fm (max) and fc.
Lower sideband
Any frequency within the lower sideband is called.
Lower Side frequency
The band of frequencies between fc and fc + fm(max)
Upper Sideband
Any frequency within the upper sideband is called?
Upper Side Frequency
The term used to describe the amount of amplitude change
(modulation) present in an AM waveform signal.
Coefficient of Modulation
The coefficient of modulation stated as a percentage.
Percent Modulation
The maximum percent modulation that can be imposed without
causing excessive distortion.
100%
The _______ in a transmitter where modulation occurs
determines whether the circuit is a low or a high-level transmitter.
Location
The modulation takes place prior to the output element of the
final stage of the transmitter.
Low-level Modulation
The modulation takes place in the final element of the final
stage where the carrier signal is at its maximum amplitude.
High-Level Modulation
The amplitude of the output signal depends on the amplitude of
the input carrier and the voltage gain of the amplifier.
Emitter Modulation
A class C modulator capable of nonlinear mixing and the modulating signal is applied directly to the collector.
Collector Modulator
Used to translate the low-frequency intelligence signals to
radio-frequency signals that can be efficiently radiated from an antenna and
propagated through free space.
Up-converter
Are used for observing the modulation characteristics of AM
transmitters.
Trapezoidal Pattern
A form of amplitude distortion introduced when the positive
and negative alternations in the AM modulated signal are not equal
(nonsymmetrical modulation).
Carrier Shift
Complex waveforms comprised of two or more frequencies.
Nonsinusoidal Signals
Are complex waves made up of two or more harmonically related
sine waves and include square, rectangular, and triangular waves.
Complex Repetitive
Waveforms
A form of AM where signals from two separate information
sources modulate the same carrier frequency at the same time without
interfering with each other. The information sources modulate the same
carrier after it has been separated into two carrier signals that are 90º out
of phase with each other.
Quadrature Amplitude
Modulation
( QAM )
