This is the summary notes of the important terms and concepts in Chapter 4 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
The process of impressing low-frequency information signals
onto a high-frequency carrier signal.
The reverse process of modulation where the received signals
are transformed back to their original form.
The process of changing the amplitude of a relatively high
frequency carrier signal in proportion with the instantaneous value of the modulating
Frequencies that are high enough to be efficiently radiated by
the antenna and propagated through free space.
The modulated output waveform from an AM modulator is?
Sometimes called conventional AM or simply AM.
The band of frequencies between fc – fm (max) and fc.
Any frequency within the lower sideband is called.
Lower Side Frequency
The band of frequencies between fc and fc + fm(max)
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.
The maximum percent modulation that can be imposed without
causing excessive distortion.
The _______ in a transmitter where modulation occurs
determines whether the circuit is a low or a high-level transmitter.
The modulation takes place prior to the output element of the
final stage of the transmitter.
The modulation takes place in the final element of the final
stage where the carrier signal is at its maximum amplitude.
The amplitude of the output signal depends on the amplitude of
the input carrier and the voltage gain of the amplifier.
A class C modulator capable of nonlinear mixing and the
modulating signal is applied directly to the collector.
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.
Are used for observing the modulation characteristics of AM
A form of amplitude distortion introduced when the positive
and negative alternations in the AM modulated signal are not equal
Complex waveforms comprised of two or more frequencies.
Are complex waves made up of two or more harmonically related
sine waves and include square, rectangular, and triangular waves.
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.
( QAM )