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.
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CHAPTER 8 |
ANGLE MODULATION RECEPTION AND FM STEREO |
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Items |
Definitions |
Terms |
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1 |
In this receivers, the voltage at the output of the audio detector is directly proportional to the frequency deviation at its input. |
FM Receivers |
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2 |
In this receivers, the voltage at the output of the audio detector is directly proportional to the phase deviation at its input. |
PM Receivers |
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3 |
The circuits used to demodulate FM and PM signals are both described under the heading ________. |
FM Receivers |
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4 |
A modulation where the information is impressed onto the carrier in the form of frequency or phase variations. |
Angle Modulation |
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5 |
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 |
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6 |
The section that rejects the image frequency in FM receivers. |
Pre-selector |
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7 |
The section that establishes the signal-to-noise ratio and noise figure in FM receivers. |
RF Amplifier |
|
8 |
The section that down-converts RF to IF. |
Mixer / Converter |
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9 |
The section that provide most of the gain and selectivity. |
IF Amplifiers |
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10 |
The section that removes the information from the modulated wave. |
Detector |
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11 |
The envelope (peak) detector common to AM receivers is replaced in FM receivers by a ________, ________, and ________. |
Limiter, Frequency Discriminator and De-emphasis Network |
|
12 |
The circuit that extracts the information from the modulated wave. |
Frequency Discriminator |
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13 |
Are frequency-dependent circuits designed to produce an output voltage that is proportional to the instantaneous frequency at its input. |
FM Demodulators |
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14 |
Circuits used for demodulating FM signals. |
Slope Detector, Foster-Seely Discriminator, Ratio Detector, PLL Demodulator, and Quadrature Detector |
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15 |
Circuits that convert FM to AM and then demodulate the AM envelope with conventional peak detectors. |
Tuned-Circuit Frequency Discriminators |
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16 |
A tuned-circuit frequency discriminator that has the most nonlinear voltage-versus-frequency characteristics and, therefore, is seldom used. |
Slope Detector |
|
17 |
Is simply two single-ended slope detectors connected in parallel and fed 180° out of phase. |
Balanced Slope Detector |
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18 |
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. |
Foster-Seeley Discriminator |
|
19 |
The typical voltage-versus-frequency response curve for a Foster-Seeley discriminator. |
S-curve |
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20 |
An FM demodulator that is relatively immune to amplitude variations in its input signal. |
Ratio Detector |
|
21 |
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 |
|
22 |
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. |
Quadrature FM Demodulator |
|
23 |
Special circuits that removes the unwanted amplitude variations since with FM, the information is contained in frequency variations. |
Limiters |
|
24 |
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 |
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25 |
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 |
|
26 |
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 |
|
27 |
Is the minimum dB difference in signal strength between two received signals necessary for the capture effect to suppress the weaker signal. |
Capture Ratio of an FM Receiver |
|
28 |
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. |
NE/SA614A |
|
29 |
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. |
Quadrature Detector |
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30 |
A low-voltage, high-performance monolithic FM IF system similar to the NE/SA614A except with the addition of a mixer/oscillator circuit. |
NE/SA616 |
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31 |
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. |
TDA7000 |
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32 |
A circuit that is used to reduce the total harmonic distortion (THD) by compressing the IF frequency swing (deviation). |
Frequency-Locked-Loop |
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33 |
With this transmission, the information signal is spatially divided into two 50-Hz to 15-kHz audio channels (a left and a right). |
Stereophonic Transmission |
|
34 |
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 “elevator music” |
Subsidiary Communications Authorization ( SCA ) |
|
35 |
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 ) |
|
36 |
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 |
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37 |
The SCA subcarrier may be AM single- or double-sideband transmission or FM with a maximum modulating-signal frequency of _______. |
7 kHz |
|
38 |
The frequency of the pilot carrier of FM stereo transmission. |
19 kHz |
|
39 |
When the phase of the carrier is modulated by the information signal, _______ results. |
Direct PM ( Indirect FM ) |
|
40 |
A monolithic FM stereo demodulator that uses PLL techniques to derive the right and left audio channels from the composite stereo signal. |
XR-1310 |
|
41 |
Half-duplex, one-to-many radio communications with no dial tone. |
Two-Way Mobile Radio |
|
42 |
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 |
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43 |
Cover a broad-frequency band from 1.8 MHz to above 300 MHz. Designed for personal use without pecuniary interest. |
Amateur ( HAM ) Radio |
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44 |
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 bands. |
Aeronautical Broadcasting Service ( ABS ) |
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45 |
Full-duplex, on-to-one radio telephone communications. |
Mobile Telephone Service |
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46 |
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 ( PCSS ) |
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47 |
Is used extensively for public safety mobile communications, such as police and fire departments and emergency medical services. |
Two-Way FM Radio Communications |
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48 |
The maximum frequency deviation for two-way FM transmitters is typically ________, and the maximum modulating-signal frequency is ________. |
5 kHz ; 3 kHz |
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49 |
Transmissions are initiated by closing a ________ switch, which turns on the transmitter and shuts off the receiver. |
Push-To-Talk ( PTT ) |
|
50 |
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 MHz. |
Mobile Radio |
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51 |
It was used rather than a simple mechanical switch to reduce the static noise associated with contact bounce in mechanical switches. |
Electronic Push-To-Talk |
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52 |
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 ) |
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