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Electronics Communication > Electronics Communication > Flashcards

Electronics Communication Flashcards

1
Q

Is the transmission, reception, and processing of information with the use of electronic circuits.

A

Electronic Communication

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2
Q

System involving the transmission of digital pulses.

A

Digital Transmission

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3
Q

Is the transmittal of digitally modulated analog signals(carriers) between two or more points in a communication system.

A

Digital Modulation

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4
Q

The information signal is digital and the frequency (f) of the carrier is varied proportional to the information signal.

A

Frequency Shift Keying ( FSK )

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5
Q

The information signal is digital and the amplitude (V) of the carrier is varied proportional to the information signal.

A

Amplitude Shift Keying ( ASK )

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6
Q

The information signal is digital and the phase (θ) of the carrier is varied proportional to the information signal.

A

Phase Shift Keying ( PSK )

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7
Q

Is defined as knowledge or intelligence that is communicated between two or more points.

A

Information

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8
Q

A modulation where both the amplitude and the phase are varied proportional to the information signal.

A

Quadrature Amplitude Modulation (QAM)

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9
Q

Performs level conversion and then codes the incoming data into groups of bits that modulate an analog carrier.

A

Pre-coder

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10
Q

Is a highly theoretical study of the efficient use of bandwidth to propagate information through electronic communications systems.

A

Information Theory

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11
Q

Is a measure of how much information can be propagated through a communications system and is a function of bandwidth and transmission time.

A

Information Capacity

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12
Q

The most basic digital symbol used to represent information.

A

Binary Digit / Bit

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12
Q

Refers to the rate of change of a signal on a transmission medium after encoding and modulation have occurred.

A

Baud

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13
Q

In 1928, _________ of Bell Telephone Laboratories developed a useful relationship among bandwidth, transmission time, and information capacity.

A

R. Hartley

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14
Q

Simply represents a digit that corresponds to the number of conditions, levels, or combinations possible for a given number of binary variables.

A

M

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15
Q

Refers to the rate of change of a digital information signal, which is usually binary.

A

Bit Rate

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16
Q

Sometimes called a symbol and could be encoded as a change in the amplitude, frequency, or phase

A

Signaling Element

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16
Q

The minimum theoretical bandwidth necessary to propagate a signal.

A

Nyquist Bandwidth

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17
Q

The carrier is either “on” or “off” which is why amplitude-shift keying is sometimes referred to as ________.

A

On-Off Keying

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18
Q

A logic 1 frequency (fm) for FSK.

A

Mark

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19
Q

A logic 0 frequency (fs) for FSK.

A

Space

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20
Q

The mark and space frequencies are separated from the carrier frequency by the _________and from each of by 2 Δf.

A

Peak Frequency Deviation (Δf)

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21
Q

_______ is the peak frequency deviation of the carrier and is equal to the difference between the carrier rest frequency and either the mark or space frequency.

A

Δf

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22
Q

Is binary FSK except the mark and space frequencies are synchronized with the input binary bit rate.

A

Continuous-Phase FSK ( CP-FSK )

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23
Q

A signal state-space diagram, is similar to a phasor diagram except that the entire phasor is not drawn. Only the relative positions of the peaks of the phasors are shown.

A

Constellation Diagram

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24
Q

Is a product modulator; the output signal is the product of the two input signals.

A

Balanced Modulator

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25
Q

Also known as quadrature PSK that is another form of angle-modulated, constant-amplitude digital modulation.

A

Quaternary PSK (QPSK)

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26
Q

A group of two bits.

A

Dibit

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27
Q

It modulates the carrier that is in phase with the reference oscillator.

A

I bit

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28
Q

It modulates the carrier that is 90 out of phase or in quadrature with reference carrier.

A

Q bit

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29
Q

Is two BPSK modulators combined in parallel

A

QPSK Modulator

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30
Q

The highest fundamental frequency present at the data input to the I or the Q balanced modulator is equal to _______ of the input data rate.

A

1/4

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31
Q

The fastest output rate of change (baud) is also equal to________ of the input bit rate.

A

1/2

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32
Q

The outputs of the product detectors are fed to the ________, here they are converted from parallel I and Q data channels to a single binary output data stream.

A

Bit Combining Circuit

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33
Q

Is a modified for of QPSK where the bit waveforms on the I and Q channels are offset or shifted in phase from each other by one-half of a bit time.

A

Offset QPSK( OQPSK )

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34
Q

The advantage of OQPSK is the _________ that must be imparted during modulation.

A

Limited Phase Shift

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35
Q

With ________, three bits are encoded, forming tribits and producing eight different output phases.

A

8 PSK

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36
Q

Group of 3 bits

A

Tribit

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37
Q

Also known as maximum distance code used to reduce the number of transmission errors.

A

Gray Code

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38
Q

Converts the I/C and Q/C bit pairs to serial, Q, and C output data streams.

A

Parallel-to-SerialLogic Circuit

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39
Q

Group of 4 bits.

A

Quadbit

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40
Q

Is an M-ary encoding technique where M = 8. The output signal from this modulator is not a constant-amplitude signal.

A

8 - QAM

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41
Q

The process of introducing transitions (pulses) into the binary signal using a prescribed algorithm

A

Scrambling

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42
Q

It uses the same algorithm for scrambling to remove the transitions

A

Descrambler

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43
Q

Is an alternative form of digital modulation where the binary input is contained in the difference between two successive signaling elements rather than the absolute phase

A

Differential Phase-Shift Keying ( DPSK )

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44
Q

Is the ratio of the average carrier power (the combined power of the carrier and its associated sidebands) to the thermal noise power.

A

Carrier-To-Noise Power Ratio

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45
Q

Is the process of extracting a phase-coherent reference carrier from a receiver signal. Sometimes called phase referencing.

A

Carrier Recovery

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46
Q

Three methods of carrier recovery.

A

Squaring Loop, Costas Loop, & Remodulator

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47
Q

Can be used to determine the approximate bandwidth for an FSK wave.

A

Bessel Functions

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48
Q

a form of digital modulation similar to PSK except the digital information is contained in both the amplitude and the phase of the transmitted carrier.

A

Quadrature Amplitude Modulation (QAM)

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49
Q

A theoretical (mathematical) expectation of the bit error performance.

A

Probability of error P(e)

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50
Q

An empirical (historical) record of a system’s actual bit error performance.

A

Bit Error Rate (BER)

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51
Q

A function of the carrier-to-noise power ratio (or, more specifically, the average energy per bit-to-noise power density ratio) and the number of possible encoding conditions used (M-ary)

A

probability of error

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52
Q

A common method of achieving carrier recovery for BPSK.

A

Squaring loop

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53
Q

A second method of carrier recovery. Produces the same results as a squaring circuit followed by an ordinary PLL in place of the BPF.

A

Costas Loop

54
Q

A third method of achieving recovery of a phase and frequency coherent carrier. Produces a loop error that is proportional to twice the phase error between the incoming signal and the VCO signal.

A

Remodulator

55
Q

Is the transmittal of digital signals between two or more points in a communications system.

A

Digital Transmission

56
Q

Circuit for digitizing voice at a low data rate by using knowledge of the way in which voice sounds are produced

A

Vocoder

57
Q

_________ developed the first digital transmission system forthe purpose of carrying digitally encoded analog signals, such as humanvoice, over metallic wire cables between telephone offices.

A

AT&T

58
Q

The primary advantage of digital transmission over analog transmission.

A

Noise Immunity

59
Q

Digital signals are also better suited than analog signals for processing and combining using a technique called _____.

A

Multiplexing

60
Q

Is the processing of analog signals using digital methods and includes band limiting the signal with filters, amplitude equalization, and phase shifting.

A

Digital Signal Processing ( DSP )

61
Q

Digital transmission systems are more resistant to analog systems to additive noise because they use ________ rather than signal amplification.

A

Signal Regeneration

62
Q

Consist essentially of sampling analog information signals and then converting those samples into discrete pulses and transporting the pulses from a source to a destination over a physical transmission medium.

A

Pulse Modulation

63
Q

The four predominant methods of pulse modulation.

A

PWM, PPM, PAM and PCM

64
Q

Sometimes called pulse duration modulation (PDM) or pulse length modulation (PLM), as the width (active portion of the duty cycle) of a constant amplitude pulse is varied proportional to the amplitude of the analog signal at the time the signal is sampled.

A

Pulse Width Modulation ( PWM )

65
Q

The position of a constant-width pulse within a prescribed time slot is varied according to the amplitude of the sample of the analog signal.

A

Pulse Position Modulation ( PPM )

66
Q

The amplitude of a constant-width, constant-position pulse is varied according to the amplitude of the sample of the analog signal.

A

Pulse Amplitude Modulation

67
Q

The analog signal is sampled and then converted to a serial ln-bit binary code for transmission.

A

Pulse Code Modulation ( PCM )

68
Q

A circuit that periodically samples the analog input signal and converts those samples to a multilevel PAM signal.

A

Sample-and-Hold Circuit

69
Q

The transmission line ________ are placed at prescribed distances to regenerate the digital pulses.

A

Repeaters

70
Q

An integrated circuit that performs the PCM encoding and decoding functions.

A

Codec ( Coder / Decoder )

71
Q

The function of a _________ in a PCM transmitter is to periodically sample the continually changing analog input voltage and convert those samples to a series of constant-amplitude pulses that can more easily be converted to binary PCM code.

A

Sampling Circuit

72
Q

The sampling process alters the frequency spectrum and introduces an error called _________.

A

Aperture Error

73
Q

The ________ of the capacitor is called the A/D conversion time because it is during this time that the ADC converts the sample voltage to a PCM code.

A

Storage Time

74
Q

If the input to the ADC is changing while it is performing the conversion, _______ results.

A

Aperture Distortion

75
Q

_________ theorem establishes the minimum sampling rate (fs)that can be used for a given PCM system.

A

Nyquist Sampling

76
Q

The binary codes used for PCM are _________, where n may be any positive integer greater than 1.

A

N-Bit Codes

77
Q

The sign bit in a sign-magnitude code.

A

Most Significant Bit ( MSB )

78
Q

Is the process of converting an infinite number of possibilities to a finite number of conditions. Is the process of rounding off the amplitudes of flat-top samples to a manageable number of levels.

A

Quantization

79
Q

A type of code where the codes on the bottom half of the table are a mirror image of the codes on the top half, except for the sign bit.

A

Folded Binary Code

80
Q

The magnitude difference between adjacent steps.

A

Quantization Interval or Quantum

81
Q

If the magnitude of the sample exceeds the highest quantization interval, ________ (also called peak limiting) occurs.

A

Overload Distortion

82
Q

Any round-off errors in the transmitted signal are reproduced when the code is converted back to analog in the receiver.

A

Quantization Error (Qe ) QuantizationNoise (Qn)

83
Q

Is the ratio of the largest possible magnitude to the smallest possible magnitude (other than 0V) that can be decoded by the digital-to-analog converter in the receiver.

A

Dynamic Ratio

84
Q

During times when there is no analog input signal, the only input to the PAM sampler is random, thermal noise also called as __________, that is converted to a PAM sample just as if it were a signal.

A

Idle Channel Noise

85
Q

A way to reduce idle channel noise wherein the first quantization interval is made larger in amplitude than the rest of the steps.

A

Midtread Quantization

86
Q

Is the process of compressing and then expanding.

A

Companding

87
Q

Two methods of companding:

A

μ-Law and A-law Companding

88
Q

Involves compression in the transmitter after the input sample has been converted to a linear PCM code and then expansion in the receiver prior to PCM decoding.

A

Digital Companding

89
Q

When digitizing speech signals only, special voice encoders/decoders called _______ are often used

A

Vacoders

90
Q

A _________ coder extracts the most significant portions of speech information directly from the time waveform rather than from the frequency spectrum as with the channel and formant vocoders.

A

Linear Predictive

91
Q

_________ modulation uses a single-bit PCM code to achieve digital transmission of analog signals.

A

Delta

92
Q

Two problems associated with delta modulation that do not occur with conventional PCM.

A

Slope Overload and Granular Subdivision

93
Q

With ________, the difference in the amplitude of two successive samples is transmitted rather than the actual sample.

A

Differential PCM ( DPCM )

94
Q

A ________ is simply the superposition of a series of harmonically related sine waves with specific amplitude and phase relationships.

A

Pulse Modulation

95
Q

Multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency.

A

Frequency Division Multiplexing

96
Q

Used for the transmission of PCM-encoded time-division multiplexed digital signals.

A

T Carriers

97
Q

Forms of delay-modulated codes where a logic 1 condition produces a transition in the middle of the clock pulse, and a logic 0 produces no transition at the end of the clock intervals unless followed by another logic 0.

A

Miller Codes

98
Q

Commonly called the Manchester Code and specified in IEEE standard 802.3 for Ethernet local area networks.

A

Biphase L

99
Q

Used for encoding SMPTE(Society of Motion Picture and Television Engineers) time-code data for recording on videotapes.

A

Biphase M

100
Q

Uses one cycle of a square wave at 0◦ phase to represent a logic 1 and one cycle of a square wave at 180◦ phase to represent a logic 0.

A

Biphase

101
Q

Popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering.

A

Digital Biphase

102
Q

Produces a condition in which a receive may lose its amplitude reference for optimum discrimination between received 1’s & 0’s.

A

DC Wandering

103
Q

Less than 100% of the bit time.

A

Return to Zero

104
Q

Categorize the type of transmission.

A

Duty Cycle

105
Q

Two nonzero voltages are involved ( a positive voltage for a logic 1 and an equal-magnitude negative voltage for a logic 0 or vice versa).

A

Bipolar

106
Q

Involves the transmission of only a single nonzero voltage level.

A

Unipolar

107
Q

Converting standard logic levels.

A

Digital Line Encoding

108
Q

First bit of the code.

A

Address Bit

109
Q

Identify when transitions occur in the data and whether that transition is from a 1 to a 0 or vice versa.

A

Three-Bit Code

110
Q

Provides frequency shifting for the master group signals.

A

Signal Processor

111
Q

Transmission of information from one or more source To one or more destination over the same transmission medium (facility).

A

Multiplexing

112
Q

Unsophisticated form of multiplexing that simply constitutes propagating signals from different sources of different cables that are contained within the same trench.

A

Space-Division Multiplexing

113
Q

Considered as transmission medium.

A

Trench

114
Q

Form of phase-division multiplexing (PDM) where to date channels (the I and Q) modulate the same carrier frequency that has been shifted 90◦ in phase.

A

QPSK

115
Q

Modulates a sine wave carrier.

A

I - Channel Bits

116
Q

Modulates a cosine wave carrier.

A

Q - Channel Bits

117
Q

Three most predominant methods of multiplexing signals.

A

Time-Division Multiplexing; Frequency-DivisionMultiplexing; Wavelength-Division Multiplexing

118
Q

Transmissions from multiple sources occur on the same but not on the same time.

A

Time-Division Multiplexing

119
Q

Most prevalent encoding technique used for TDM digital signals.

A

PCM

120
Q

Simply an electronically controlled digital switch with two inputs and one outputs.

A

Multiplexer

121
Q

A communications system that uses digital pulses rather than analog signals to encode information.

A

Digital Carrier System

122
Q

Voice band channel bandwidth.

A

300 Hz to 3000 Hz

123
Q

Circuit for digitizing voice at a low data rate by using knowledge of the way in which voice sounds are produced

A

Vocoder

124
Q

A coding scheme that records the change in the signal level since the previous sample

A

Delta Modulation

125
Q

Distortion created by using too low a sampling rate when coding an analog signal for digital transmission

A

Either aliasing or foldover distortion

126
Q

Inaccuracies caused by the representation of a continuously varying quantity as one of a number of discrete values

A

Quantizing Errors

127
Q

A device that encodes and recodes a digital signal as well as amplifying it.

A

Regenerative Repeater

128
Q

The ratio of the largest possible magnitude to the smallest possible magnitude (other than 0 V) that can be decoded by the digital-to-analog converter in the receiver.

A

Dynamic Range (DR)

129
Q

What is the control system that generates a signal with a fixed relation to the phase of a
reference signal and responds to both the frequency and the phase of the input signals?

A

Phase Locked Loop (PLL)

130
Q

Simplest form of PSK, where N=1 and M=2. A form of square-wave modulation of a continuous wave (CW) signal.

A

Binary Phase Shift Keying (BPSK)

131
Q

other form of angle-modulated, constant-amplitude digital modulation. An M-ary encoding scheme where N=2 and M=4

A

Quaternary phase shift keying (QPSK) /or quadrature PSK

132
Q

when tops of the sample pulses retain their natural shape during the sample interval, making it difficult for an ADC to convert the sample to a PCM code

A

natural sampling

133
Q

It is popular type of line encoding that produces a strong timing component for
clock recovery and does not cause DC wandering.

A

Digital Biphase

Electronics Communication (1 decks)

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