This is the summary notes of the important terms and concepts in Chapter 8 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.
RECEPTION AND FM STEREO
In this receivers, the voltage at the output of the audio
detector is directly proportional to the frequency deviation at its input.
In this receivers, the voltage at the output of the audio
detector is directly proportional to the phase deviation at its input.
The circuits used to demodulate FM and PM signals are both
described under the heading ________.
A modulation where the information is impressed onto the
carrier in the form of frequency or phase variations.
A method used to remove amplitude variations caused by noise
from the composite waveform simply by clipping the peaks of the envelop prior
The section that rejects the image frequency in FM receivers.
The section that establishes the signal-to-noise ratio and
noise figure in FM receivers.
The section that down-converts RF to IF.
Mixer / Converter
The section that provide most of the gain and selectivity.
The section that removes the information from the modulated
The envelope (peak) detector common to AM receivers is
replaced in FM receivers by a ________, ________, and ________.
Limiter, Frequency Discriminator and De-emphasis
The circuit that extracts the information from the modulated
Are frequency-dependent circuits designed to produce an output
voltage that is proportional to the instantaneous frequency at its input.
Circuits used for demodulating FM signals.
Slope Detector, Foster-Seely Discriminator,
Ratio Detector, PLL Demodulator, and Quadrature Detector
Circuits that convert FM to AM and then demodulate the AM
envelope with conventional peak detectors.
Tuned-Circuit Frequency Discriminators
A tuned-circuit frequency discriminator that has the most
nonlinear voltage-versus-frequency characteristics and, therefore, is seldom
Is simply two single-ended slope detectors connected in
parallel and fed 180° out of phase.
Balanced Slope Detector
Sometimes called a phase shift discriminator that is a
tuned-circuit frequency discriminator whose operation is very similar to that
of a balanced slope detector.
The typical voltage-versus-frequency response curve for a
An FM demodulator that is relatively immune to amplitude
variations in its input signal.
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
Sometimes called a coincidence detector that extracts the
original information signal from the composite IF waveform by multiplying two
quadrature (90° out of phase) signals.
Special circuits that removes the unwanted amplitude
variations since with FM, the information is contained in frequency
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
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
FM Thresholding, FM Quieting, or FM
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.
Is the minimum dB difference in signal strength between two
received signals necessary for the capture effect to suppress the weaker
Capture Ratio of an FM Receiver
An improved monolithic low-power FM IF system manufactured by
Signetics Corporation. It is a high gain, high frequency device that offers
low-power consumption and excellent input sensitivity at 455 kHz.
A multiplier cell similar to a mixer stage, but instead of
mixing two different frequencies, it mixes two signals with the same
frequencies but with different phases.
A low-voltage, high-performance monolithic FM IF system
similar to the NE/SA614A except with the addition of a mixer/oscillator
A monolithic integrated-circuit FM radio system manufactured
by Signetics Corporation for monolithic FM portable radios. A complete FM
radio receiver on a single integrated-circuit chip.
A circuit that is used to reduce the total harmonic distortion
(THD) by compressing the IF frequency swing (deviation).
With this transmission, the information signal is spatially
divided into two 50-Hz to 15-kHz audio channels (a left and a right).
Used to broadcast uninterrupted music to private subscribers,
such as department stores, restaurants, and medical offices equipped with
special receivers; Sometimes cordially refer to as
Subsidiary Communications Authorization (
The process of placing two or more independent channels next
to each other in the frequency domain (stacking the channels), and then
modulating a single high-frequency carrier with the combined signal.
Frequency Division Multiplexing ( FDM )
The primary audio channel remained at 50 Hz to 15 kHz, while
an additional SCA channel is frequency translated to the _______ passband.
60 kHz To 74 kHz
The SCA subcarrier may be AM single- or double-sideband
transmission or FM with a maximum modulating-signal frequency of _______.
The frequency of the pilot carrier of FM stereo transmission.
When the phase of the carrier is modulated by the information
signal, _______ results.
( Indirect FM )
A monolithic FM stereo demodulator that uses PLL techniques to
derive the right and left audio channels from the composite stereo signal.
Half-duplex, one-to-many radio communications with no dial
Two-Way Mobile Radio
Provides 26.96 to 27.41 MHz public, non-commercial radio
service for either personal or business use utilizing push-to-talk AM DSBFC
and AM SSBFC.
Class D Citizens Band ( CB ) Radio
Cover a broad-frequency band from 1.8 MHz to above 300 MHz.
Designed for personal use without pecuniary interest.
Amateur ( HAM ) Radio
Provides 2.8 MHz to 457 MHz. ABS disseminates information for
the purposes of air navigation and air-to-ground communications utilizing
conventional AM and various forms of AM SSB in the HF, MF, and VHF frequency
Aeronautical Broadcasting Service ( ABS )
Full-duplex, on-to-one radio telephone communications.
Mobile Telephone Service
Provides worldwide telecommunication service using handheld
telephones that communicate with each other through low earth-orbit satellite
repeaters incorporating QPSK modulation and both FDMA and TDMA.
Personal Communications Satellite Service (
Is used extensively for public safety mobile communications,
such as police and fire departments and emergency medical services.
Two-Way FM Radio Communications
The maximum frequency deviation for two-way FM transmitters is
typically ________, and the maximum modulating-signal frequency is ________.
5 kHz ; 3 kHz
Transmissions are initiated by closing a ________ switch,
which turns on the transmitter and shuts off the receiver.
Push-To-Talk ( PTT )
It was used as early as 1921 when the Detroit Police
Department used a mobile radio system that operated at a frequency close to 2
It was used rather than a simple mechanical switch to reduce
the static noise associated with contact bounce in mechanical switches.
Transmitters equipped with ________ are automatically keyed
each time the operator speaks into the microphone, regardless of whether the
PTT button is depressed.
Voice-Operated Transmitter ( VOX )