CHAPTER 1: INTRODUCTION TO COMMUNICATION SYSTEMS
1. ___________ is the path for the transmission of signals. 2. ___________ is also known as the modulating signal. 3. TRUE/ FALSE: The carrier frequency is generally much
higher than the information signal.
4. The frequency spectrum of the information signal is often referred to as the___________.
5.
In modulation, the parameters that can be changed are amplitude Ec, frequency c, and ___________.6. Where does demodulation or detection takes place? 7. _________ is the general rule that relates bandwidth and
information capacity.
8. _________ is the term used in communications to refer to the combining of two or more information signals.
9. When the available frequency range is divided among the signals, the process is known as ____________.
10.Give examples of FDM.
11._________ uses single communication channel to send many signals.
12.VHF frequency ranges from________ to _______. 13.Low- frequency signals are sometimes called
__________,while high- frequency signals corresponds to SHORT WAVE.
14.___________ happens when more than one signal uses the same transmission medium and the signals interact with each other.
15.In a frequency domain representation, the _________ and is shown on one axis and the frequency is displayed on the other.
16.He is a French mathematician who discovered that a well behaved periodic waveform can be represented as a series of sine and/ or cosine waves at multiples of its fundamental frequency plus a dc offset.
17.What is the simplest ac signal?
18.TRUE/FALSE: In communications over cables, the more bandwidth used by each signal, the fewer signals can be carried by the cable.
19.___________ consist of undesired, usually random variations that interfere with the desired signals and inhibit
communication.
20.Atmospheric noise is also called __________ because lightning is the principal source of this noise. 21.__________ is the technique used to improve communication
by disabling the receiver for the duration of the burst. 22.What is the noise generated by all electronic equipment? 23.__________ is produced by the random motion of electrons
in a conductor due heat.
24.TRUE/ FALSE: Thermal noise power exists in all conductors and resistors at any temperature above absolute zero. 25.__________ is the technique where amplifiers used with very
CHANEL INFORMATION SIGNAL TRUE BASEBAND PHASE
RECEIVER HARTLEY’S LA MULTIPLEXING FREQUENCY- DIVISION MULTIPLEXING (FDM) RADIO AND TV BROADCASTING TIME- DIVISION MULTIPLEXING (TDM) 30 TO 300 MHZ LONG WAVE INTERFERENCE AMPLITUDE OR POWER JOSEPH FOURIER SINUSOID TRUE NOISE STATIC NOISE BLANKING INTERNAL NOISE THERMAL NOISE TRUE CRYOGENICS SHOT NOISE TRANSIT TIME SIGNAL- TO- NOISE POWERlow level signals are cooled artificially to reduce noise. 26.__________ is due to random variations in current flow in
active devices such as tubes, transistors, and semiconductor diodes.
27.__________ is the time a charge carrier spends in the device. 28.__________ it is the ratio of the signal power to noise power
usually expressed in decibels.
29.__________ is a figure of merit, indicating how much a component, stage, or series of stages degrades the S/N of a system.
30.The equivalent temperature of a passive system having the same noise- power output as the given system is known as the __________.
31.TRUE/ FALSE: When two or more stages are connected in cascade, the noise generated in the first stage is amplified in all succeeding stages.
32.
__________ it is the device for displaying signals in the frequency domain.NOISE FIGURE (NF) NOISE TEMPERATURE TRUE
SPECTRUM ANALYZER
CHAPTER 2: RADIO- FREQUENCY CIRCUITS
1. Who designed the first practical alternator transmitter in 1906 for a station at Brant Rock, Massachusetts?
2. TRUE/ FALSE: A capacitor, could exhibit inductance and resistance as well as capacitance.
3. _________ it is a wire that provides a small capacitance to ground that is adjusted during circuit alignment by bending the wire slightly in one direction or another. (The small length of wire is connected at one end and used as a capacitance to the ground)
4. _________ is the removal of an unwanted signal by providing a low- impedance path to ground.
5. In some amplifiers, the internal capacitance of the active device can cause feedback that produces the same effect on the circuit as a much larger capacitance across the amplifier input is called __________.
6. Wideband amplifiers typically use ___________ coupling. 7. Single- ended audio amplifiers are generally operated in
_________, where the transistor conducts current at all times for a conduction angle of 360 degrees.
8. In a _________ amplifier, each transistor is biased at cutoff, so that each conducts for 180 degrees of the input cycle. 9. In a _________ amplifier, the active device conducts for less
than 180 degrees of the input cycle.
10.__________ is a means of avoiding the instability in amplifiers by using negative feedback.
11.A circuit whose output is proportional to the product of the instantaneous amplitude of two input signals is called _________.
12.LC circuits are more common at what frequency?
13.Any amplifier can be made to oscillate if a portion of the output is fed back to the input in such a way that _________ is followed.
14.__________ it is an oscillator that can be recognized by its use
ENGR. ERNST ALEXANDERSON TRUE GIMMICK BYPASSING MILLER EFFECT TRANSFORMER CLASS A CLASS B CLASS C NEUTRALIZATION MULTIPLIER RADIO FREQUENCY BARKHAUSEN CRITERIA HARTLEY OSCILLATOR COLPITTS OSCILLATOR CLAPP OSCILLATOR
of a tapped inductor part of a resonant circuit to provide feedback.
15.__________ is an oscillator that uses a capacitive voltage divider instead of a tapped inductor to provide feedback. 16.__________ is a variation of the Colpitts circuit designed to
swamp device capacitances for greater stability. 17.A reverse- biased diode used as a voltage- variable
capacitor is known as__________.
18.____________ oscillators achieve greater stability by using a small slab of quartz as a mechanical resonator in place of an LC tuned circuit.
19.____________ an effect that occurs with some materials, such as quartz and some ceramics, whereby a voltage is
produced across the material when it is deformed; applying a voltage to the material causes mechanical deformation. 20.The circuit that uses the crystal in place of the inductor in a
series- resonant circuit consisting of C1, C2 and the crystal. 21.The frequency of a crystal oscillator can be adjusted slightly
by placing a variable capacitance in series or in parallel with the crystal. This oscillator is known as_________.
22.__________ is a nonlinear circuit that combines two signals in such a way as to produce the sum and difference of the two input frequencies at the output.
23.Mixing is different from _______ summing, because the latter produces only the two input signal frequencies.
24.When the cross products are not wanted, they are called ________distortion.
25.
_______ is a mixer in which the input frequencies are cancelled and are therefore not present at the output. 26.A device that can produce a large number of outputfrequencies from a smaller number of fixed frequency oscillators.
27._________ is a device that locks the frequency of a VCO exactly to that of an input signal.
28.What is the range over which the reference frequency can be varied and still achieve phase lock?
29.What is the total frequency range within which lock can be maintained?
30.The number by which a digital divider chain divides is called _________.
31.In a frequency synthesizer, the smallest amount by which the output frequency can be changed is called __________. 32._______ it is a divider that precedes the main programmable
divider in a frequency synthesizer.
33.The movement of a signal from one frequency to another using a mixer- oscillator combination is called _________. 34.TRUE/ FALSE: As the frequency increases, the effects of
distribute capacitance and inductance became more significant.
35.TRUE/ FALSE: Interactions between components in high- frequency can often be avoided by the use of shielding and bypassing. VARACTOR CRYSTAL PIEZOELECTRIC EFFECT PIERCE CIRCUIT VARIABLE CRYSTAL OSCILLATOR (VXO) MIXER LINEAR INTERMODULATION BALANCED MIXER FREQUENCY SYNTHESIZER
PHASE- LOCKED LOOP (PLL) CAPTURE RANGE LOCK RANGE MODULUS RESOLUTION PRESCALER FREQUENCY TRANSLATION TRUE TRUE
CHAPTER 3: AMPLITUDE MODULATION
1. The simplest and the earliest form of radio was the transmission of _______.
2. _________ it is the modulation scheme in which the amplitude of a high- frequency signal is varied in accordance with the instantaneous amplitude of an information signal.
3. The curve produced by joining the tips of the individual RF cycles of a modulated wave is called __________.
4. What is the high- frequency signal that is combined with an information signal to produce the modulated waveform? 5. The ratio between the amplitudes of the modulating signal
and the carrier is termed as __________.
6. When the modulation is greater than 1, ___________ is said to be present.
7. __________ it is term used too describe additional side
frequencies produced by overmodulation or distortion in an AM system.
8.
TRUE/ FALSE: For a full- carrier AM, m must be in the range of 0 to 1.9. Those above the carrier can be grouped into a band of frequencies called the upper sideband and the _______ sideband that looks like a mirror image of the upper, reflected in the carrier.
10.TRUE/ FALSE: In any situation where spectrum space is limited, a narrow bandwidth allows more signals to be transmitted simultaneously than does a wider bandwidth. 11.TRUE/ FALSE: The total power in an AM increases with
modulation, reaching a value 50% greater than that of the unmodulated carrier for 100% modulation.
12.TRUE/ FALSE: The extra power with modulation goes into the sidebands: the carrier power does not change with
modulation.
13.TRUE/ FALSE: AM transmission is more efficient than when the modulation index is as lose to 1 as practicable.
14.Is it possible to send two separate information signals using amplitude modulation at one carrier frequency?
15.What is the transmission of two separate information signals using two amplitude- modulated carriers at the same
frequency but differing in phase by 90 degrees?
16.TRUE/ FALSE: Removing the carrier from a fully modulated AM signal would change the power available for the
sidebands from one-third of the total to all of it.
17.___________ is an AM signal in which the carrier frequency component is eliminated and only one or both sidebands are transmitted.
18.Any AM scheme in which only one of the two sidebands is transmitted is called________.
19.TRUE/ FALSE: The S/N improvement resulting from bandwidth reduction is in addition to that achieved by increasing the transmitted in the sidebands.
20.What is the signal consisting of two audio frequencies, not harmonically related, used to test SSB transmitters?
21.The power measured at modulation peaks in an AM or SSB signal is called_______. MORSE CODE AMPLITUDE MODULATION (AM) ENVELOPE CARRIER MODULATION INDEX OVERMODULATION SPLATTER TRUE LOWER TRUE TRUE TRUE TRUE YES QUADRATURE AM TRUE SUPPRESSED- CARRIER SIGNAL SINGLE- SIDEBAND (SSB) TRUE
TWO-TONE TEST SIGNAL PEAK- ENVELOPE POWER(PEP) TRUE TRUE TRUE TRUE
22.TRUE/ FALSE: With single- tone modulation, the PEP and the average power are equal, since the signal is a sine wave with the same peak voltage for every cycle.
23.TRUE/ FALSE: The average power with voice modulation varies from PEP/4 to PEP/3.
24.TRUE/ FALSE: Full- carrier AM produces a signal with an envelope that closely resembles the information signal. 25.TRUE/ FALSE: The bandwidth of an AM signal can be halved
by suppressing one of the two sidebands, with no loss of information.
CHAPTER 4: ANGLE MODULATION
1. Who proposed a practical FM system in 1936? 2. A general term that includes frequency and phase
modulation is called__________.
3. TRUE/ FASLE: In FM, the frequency of the signal varies with the amplitude of the modulating signal.
4. TRUE/ FALSE: In PM, the phase varies directly with the modulating- signal.
5. TRUE/ FALSE: The most important of FM or PM over AM is the possibility of a greatly improved S/N ratio.
6. TRUE/ FALSE: FM is widely used for analog communication, while PM sees greatest application in data communication. 7. TRUE/ FALSE: When the frequency is greater than the carrier
frequency, the phase angle gradually moves ahead, and when the frequency is lower than the carrier frequency, the phase begins to lag.
8. TRUE/ FALSE: For an FM signal, the number of sets of sidebands is theoretically infinite.
9. The amount by which the frequency of an FM signal shifts to each side of the carrier frequency is called_________.
10.In FM and PM, what is peak amount of in radians by which the phase of a signal deviates from its resting value?
11.
TRUE/ FALSE: Unlike the amplitude modulation index, which cannot exceed one, there are no theoretical limits on mf. 12.TRUE/ FALSE: The greater the frequency change, the greaterthe increase in phase angle.
13.TRUE/ FALSE: The amount of phase change is proportional to the length of time the instantaneous frequency stays above the carrier frequency, that is, the phase deviation is proportional to the period of the modulating signal.
14.TRUE/ FALSE: Sidebands with amplitudes less than about 1% of the total signal voltage can usually be ignored, so for practical purposes an angle- modulated signal can be considered to be band- limited.
15.
If we reduce mf , what will happen to the amplitude of its sidebands?16.TRUE/ FALSE: Sometimes FM is called constant- bandwidth communications mode.
17.What is the method of approximation used to find the bandwidth of an FM signal?
18.___________is an FM with a relatively low modulation index.
EDWIN ARMSTRONG ANGLE MODULATION TRUE TRUE TRUE TRUE TRUE TRUE FREQUENCY DEVIATION MODULATION INDEX TRUE TRUE TRUE TRUE REDUCES ALSO TRUE CARSON’S RULE NARROWBAND FM WIDEBAND FM TRUE CAPTURE EFFECT THRESHOLD EFFECT
(mf < 0.5)
19.FM with a relatively large modulation index is called__________.
20.TRUE/ FALSE: FM has a significant advantage compared with AM in the presence of noise or interference provided the deviation is relatively large and the signal is reasonably strong.
21.What is the ability of an FM receiver to receive the stronger of two signals, ignoring the weaker?
22.What is the noise- reduction effect that occurs with strong FM signals?
23._________ uses a high pass filter in an FM transmitter to improve the signal- to- noise ratio.
24._________ uses a low- pass filter in the receiver to remove the effect of pre- emphasis on the frequency response. 25.TRUE/ FALSE: Stereo FM transmission is accomplished using
a multiplexing scheme that preserves compatibility with monaural receivers and requires only a slight increase in bandwidth. Noise penalty is paid with stereo FM.
26._________ is the method of measuring deviation in FM. 27.When does FM stereo broadcasting using the present
multiplexing began?
PRE- EMPHASIS DE- EMPHASIS TRUE
BESSEL- ZERO METHOD 1961
CHAPTER 5: TRANSMITTER
1. TRUE/ FALSE: The very first transmitters used a spark gap connected directly to an antenna.
2. TRUE/ FALSE: A transmitter must generate a signal at the correct carrier frequency, with the right power level, and with the modulation that is an accurate reflection of the original information signal.
3. _________ is the system that provides more gain for low- level than for higher- level
4. _________ refers to the ability to change operating frequency rapidly without extensive retuning.
5. What is the ratio of time on to total time?
6. TRUE/ FALSE: The efficiency of a transmitter is an important specification, particularly in view of the large power levels often used.
7. What is the ratio of the output power to power input from the primary source, whether it be the ac power line or battery?
8. TRUE/ FALSE: Overall efficiency is reduced by factors as tube- heater power and losses in the power supply.
9. _________ is the ratio between the largest and smallest signal at a point in a system.
10.TRUE/ FALSE: Communications transmitters tend to use a relatively simple Automatic – Level- Control (ALC) that keeps the modulation as a level approaching but not exceeding 100%.
11.TRUE/ FALSE: Automatic frequency control (AFC) is a scheme for keeping a transmitter or receiver tuned to a correct frequency.
12.What type of modulation is done when the amplitude
TRUE TRUE COMPRESSION FREQUENCY AGILITY DUTY CYCLE TRUE OVERALL EFFICIENCY TRUE TRUE TRUE HIGH-LEVEL MODULATION TRUE LOW- LEVEL MODULATION
modulation of the output element of the output stage of a transmitter?
13.TRUE/ FALSE: High- level modulation is used in most AM transmitters for greater efficiency.
14.________ is the modulation of the transmitter at any point before the output element of the output stage.
15.________ is any system that generates FM without using phase modulation.
16.________ is the part of the transmitter that operates at low power level.
17.TRUE/ FALSE: The different AM transmitter stages are the oscillator stage, buffer and multiplier stage, driver stage and the power amplifier or modulator stage.
18.TRUE/ FALSE: When variable- frequency operation is
required the usual practice is to use a frequency synthesizer locked to a crystal- controlled master oscillator.
19.An amplifier stage used to isolate two other stages from each other is ________.
20.TRUE/ FALSE: Multiplier stages are required to generate harmonics as part of their design.
21.The driver stage is sometimes called____________.
22.__________ is an amplifier which supplies the required input signal power for a power amplifier.
23.__________ is the change of carrier amplitude with modulation in an AM transmitter.
24.TRUE/ FALSE: Audio circuitry is required to amplify the very small signal from a microphone to a sufficient level to modulate the transmitter.
25.TRUE/ FALSE: Transmitters require an impedance matching circuit between the output of the power amplifier and the antenna.
26.TRUE/ FALSE: The pi network can be used to transform the impedances up or down.
27.What is a noninductive power resistor used to simulate an antenna?
28.TRUE/ FALSE: A DSBSC AM can be generated by means of a balanced modulator to which baseband and carrier
frequency signals are applied.
29.SSB transmitter usually work by filtering a DSBSC signal to remove unwanted sideband, then using ________ a mixer to move the signal to the operating frequency.
30.SSB signals, like all AM signals, require ____________.
31.___________ requires that the carrier oscillator be frequency modulated.
32.In ___________, the baseband signal is integrated and then applied to a phase modulator.
33._____________ multiplies the deviation of n FM signal by the same factor as the carrier frequency.
34.___________ can be used to move the output frequency without affecting the modulation.
35.TRUE/ FALSE: Most FM transmitters use PLL modulators. 36.An oscillator whose frequency is controlled by a binary
number written to an internal register is termed as _____________. DIRECT FM EXCITER TRUE TRUE BUFFER TRUE INTERMEDIATE POWER AMPLIFIER DRIVER CARRIER SHIFT TRUE TRUE TRUE DUMMY LOAD TRUE MIXER LINEAR AMPLIFICATION DIRECT FM INDIRECT FM FREQUENCY MULTIPLIER MIXER TRUE NUMERICALLY- CONTROLLED OSCILLATOR DIRECTIONAL COUPLER SPURIOUS SIGNAL
37.It is device that allows a signal moving along a transmission line in one direction to be measured.
38.Any emission from a transmitter other than the carrier sidebands required by the modulation scheme in use is called ___________.
CHAPTER 6: RECEIVER
1. What is the very first receiving device used by Edouard Branly in 1890?
2. What is the measure of the signal strength required to achieve a given signal- to- noise ratio?
3. What is the ability to reject unwanted signals at frequencies different from that of the desired signal?
4. TRUE/ FALSE:The superhet uses a mixer/ local oscillator combination to transfer all incoming signal frequencies to a common IF.
5. ___________ is a receiver in which the signal is moved, a mixer, to an intermediate frequency before demodulation. 6. A receiver in which the signal is amplified at its original
frequency before demodulation is called __________.
7. TRUE/ FALSE: Superheterodyne receivers can receive signals at frequencies other than that to which the receiver was tuned.
8. The component tolerances cause the circuits to tune to slightly different frequencies are corrected with small adjustable capacitors called _________ and _________.
9. __________ is the reduction in effective cross- sectional area of a conductor with increasing frequency.
10.TRUE/ FALSE: At higher frequency, internal magnetic fields in the wire cause the current to flow mainly in the region near the surface of the conductor.
11.What is a bandpass filter that uses piezoelectric quartz elements?
12.Who invented the superheterodyne receiver or superhet in 1918?
13.TRUE/ FALSE: The input filter and RF stage are sometimes referred to as the __________ of a receiver.
14.___________ is an oscillator used in conjunction with a mixer t shift a signal to different frequency.
15.A frequency to which a signal is shifted as an intermediate step in reception or transmission is known as__________. 16.TRUE/ FALSE: The IF must be high enough to provide good
image rejection but low enough to allow the required selectivity to be obtained with the type of filter in use. 17.The combination of the mixer and the local oscillator is
known as_________.
18.TRUE/ FALSE: Images and other spurious responses must be rejected before the mixer. This requires bandpass filtering in the receiver before the mixer.
19.___________ is a bandpass filter using piezoelectric ceramic element.
20.TRUE/ FALSE: The stability of a superheterodyne receiver depends directly on that of the local oscillator. Changing the
COHERER SENSITIVITY SELECTIVITY TRUE SUPERHETERODYNE RECEIVER TUNED- RADIO- FREQUENCY(TRF) RECEIVER TRUE TRIMMERS PADDERS SKIN EFFECT TRUE CRYSTAL FILTER EDWIN H. ARMSTRONG TRUE LOCAL OSCILLATOR INTERMEDIATE FREQUENCY TRUE CONVERTER TRUE CERAMIC FILTER TRUE AUTOMATIC GAIN CONTROL (AGC) AUTODYNE CONVERTER SPURIOUS RESPONSE 455 KHZ
local oscillator frequency tunes the receiver.
21.A circuit used to adjust the gain of a system in accordance with the input signal strength is known as __________.
22.The mixer and local oscillator use a single transistor in a configuration is called __________.
23.Reception of signals at frequencies other than that to which the receiver is tuned is known as _________.
24.If the IF is 455 kHz and high- side injection is used, the local oscillator is tuned so that it generates frequency that is always _________ higher than the incoming signal.
25.__________ is the application to a mixer of the signal from a local oscillator that operates at a frequency above that of the incoming signal.
26.__________ is the application to a mixer of a signal from a local oscillator that operates at a frequency below that of the incoming signal.
27.For a bandpass filter, the ratio between the bandwidths for two specified amounts of attenuation is called __________. 28.TRUE/ FALSE: Adjacent channel rejection is another way of
specifying selectivity; it is commonly used with channelized systems, such CB radio.
29._________it is defined as the number of decibels by which an adjacent channel signal must be stronger than the desired signal for the same receiver.
30.The communications channel immediately above or below the desired channel in frequency is called__________.
31.The next communications channel beyond the adjacent channel is called__________.
32.___________ distortion occurs when the frequencies
generated are multiples of those in the original modulating signal.
33.___________ takes place when frequency components in the original signal mix in a nonlinear device, creating sum and difference frequencies.
34.TRUE/ FALSE: SSBSC require a beat- frequency oscillator to reinsert the carrier, and generally use product detectors. 35.The ratio between two signal levels expressed in decibel is
the __________ of the receiver.
36.TRUE/ FALSE: Any nonlinearity in the detector or any of the amplification stages can cause intermodulation between components of the original signal.
37.The reduction of gain for a weak signal due to a strong signal close to it in frequency is called __________. (desensitization or desense)
38.TRUE/ FALSE: An image must be rejected prior to mixing: once it has entered the IF chain the image will be
indistinguishable from the desired signal and impossible to filter out.
39.___________ is sometimes used to describe the same phenomenon as image response.
40.What is the circuit used to recover the baseband signal from a modulated signal?
41.___________ is an AM demodulator that works by rectifying the signal and low- pass filtering the result.
42.___________ is a detector for suppressed carrier AM signals
HIGH- SIDE INJECTION LOW- SIDE INJECTION SHAPE FACTOR TRUE ADJACENT CHANNEL REJECTION ADJACENT CHANNEL ALTERNATE CHANNEL HARMONIC INTERMODULATION TRUE DYNAMIC RANGE TRUE BLOCKING TRUE DOUBLE- SPOTTING DEMODULATOR/ DETECTOR ENVELOPE DETECTOR PRODUCT DETECTOR PILOT CARRIER DISCRIMINATOR QUADRATURE DETECTOR TRUE TRUE MECHANICAL FILTER QUIETING SENSITIVITY TRUE TRUE SQUELCH SURFACE- ACOUSTIC-
that works by multiplying the signal with a regenerated carrier.
43.A low- level carrier signal transmitted to facilitate the regeneration of the carrier at the receiver is
called___________.
44.Any detector for FM or PM signals is called __________. 45.__________ is an FM detector that is based on a 90 degree
phase- shift network.
46.TRUE/ FALSE: FM detectors should respond to frequency variations and ignore amplitude modulation. Limiters can be used to remove AM before the detector.
47.TRUE/ FALSE: Receivers require some form of AGC to compensate for the very great range in the signal strength at the antenna.
48.__________ is a bandpass filter that uses a mechanical resonator.
49.The strength of unmodulated carrier that reduces the noise output of the FM receiver by a specified amount is known as _____________.
50.TRUE/ FALSE: SINAD is the ratio of the signal- plus- noise and distortion to noise- plus- distortion.
51.TRUE/ FASLE: S- meter is a meter on the receiver that indicates the strength of the received signal.
52.___________ is a system that disables the output of a receiver in the absence of a suitable signal.
53.A filter that uses acoustic waves on the surface of a substrate to achieve the desired response is called __________.
54.__________ is the adjustment of two or more tuned circuits so that they can be tuned simultaneously with one adjustment. 55.__________ is the FM signal strength with defined deviation,
required to produce a specified SINAD in a receiver.
56.TRUE/ FALSE: Signal injection and signal tracing are useful troubleshooting techniques fro receivers and for many other types of electronic system.
WAVE (SAW) TRACKING
USABLE SENSITIVITY TRUE
CHAPTER 7: DIGITAL COMMUNICATIONS
1. TRUE/ FALSE: Digital communication came first than analog communication.
2. A device that decodes and recodes a digital signal as well as amplifying it is called__________.
3. The relationship between time, information capacity, and channel bandwidth is given by the equation called
__________.
4. TRUE/ FALSE: Modern digital systems have better
performance and use less bandwidth than equivalent analog systems.
5. ___________ is a device that detects the amplitude of an input signal at a particular time called sampling time and maintains its output at or near that amplitude until the next sampling time.
6. ___________ is a distortion caused by using too low sampling rate when coding an analog signal for digital transmission.
TRUE
REGENERATIVE REPEATER HARTLEY’S LAW TRUE
SAMPLE- AND- HOLD CIRCUIT
ALIASING/ FOLDOVER DISTORTION
7. TRUE/ FALSE: An analog signal that is to be transmitted digitally must be sampled at least twice per cycle of its highest- frequency component. Failure to do so creates undesirable aliasing.
8. A series of pulses in which the amplitude of each pulse represents the amplitude of the information signal at a given time is known as ___________.
9. What is the series of pulses, in which the duration of each pulses represents the amplitude of the information signal at a given time?
10.What is the series of pulses, in which the timing of each pulse represents the amplitude of the information signal at a given time?
11.What is the series of pluses, in which the amplitude of the information signal at a given time is coded as a binary number?
12.TRUE/ FALSE: In linear PCM, levels are separated by equal voltage gradations.
13.TRUE/ FALSE: PCM requires that the amplitude of each sample of a signal be converted to a binary number. The more bits used for the number, the greater the accuracy but the greater the bit rate required.
14.__________ is the representation of a continuously varying quantity as one of a number of discrete values.
15.__________ are inaccuracies caused by the representation of a continuously varying quantity as one of a number of discrete values.
16.TRUE/ FALSE: For a linear PCM system, the maximum dynamic range in decibels is given approximately by DR= (1.76 + 6.02m) dB where m is the number of bits per sample.
17.The combination of compression at the transmitter and expansion at the receiver of a communication system is called ___________.
18.____________ is the amplification of a signal in such a way that there is less gain for higher- level input signals than for lower- input signals.
19.
TRUE/ FALSE: In companding, the system used in the North American telephone system uses a characteristics known as the mu (
) law.20.__________ is the conversion of a sampled analog signal into a PCM or delta modulation bitstream.
21.What is the device that converts the sampled analog signal to and from its PCM or delta modulation equivalent?
22.
TRUE/ FALSE: Delta modulation transmits only one bit per sample, indicating whether the signal level is increasing or decreasing, but it need a higher sampling rate than PCM for equivalent results.23.TRUE/ FASLE: The binary number produced by the codec in a telephone system has eight bits.
24.____________ is the filtering of signals by converting them to digital form, performing arithmetic operations on the data bits, then converting back to analog form.
25.___________ is a coding scheme that records the change in signal level since the previous sample.
PULSE-AMPLITUDE MODULATION (PAM) PULSE- DURATION MODULATION (PDM/PDM) PULSE- POSITION MODULATION (PPM) PULSE- CODE MODULATION (PCM) TRUE TRUE QUANTIZING QUANTIZING VALUE TRUE COMPANDING COMPRESSION TRUE CODING CODEC TRUE TRUE DIGITAL SIGNAL PROCESSING (DSP) DELTA MODULATION SLOPE OVERLOAD TRUE LINE CODE NEGATIVE LOGIC POSITIVE LOGIC TRUE NRZ RZ
26.When a signal in a region changes more rapidly than the system can follow, the error created in the output is called ____________.
27.TRUE/ FALSE: In adaptive modulation in which the step size varies according to previous values is more efficient.
28.A system for translating logic ones and zeros into voltage or current levels for transmission is called___________.
29.__________ is a logic system in which a high level represents logic one and a low level represents logic zero.
30.___________ is a logic system in which a low level represents a logic one and a high level represents logic zero.
31.TRUE/ FALSE: The term unipolar means that the voltage or current polarity is always the same.
32.A data line code in which the voltage or current does necessarily return to zero between bits is known as ___________.
33._________ is a line code in which the voltage or current returns to zero at the end of each bit period.
34.TRUE/ FALSE: Manchester code is a type of biphase code. Every bit has a level transition in the center of the bit period.
35.What is the data code that uses both polarities of voltage or current?
36.What is a line code in which the polarity of the voltage or the direction of the current remains the same at all times? 37.A group of twelve frames is called ___________.
38.___________ a bits added to a digital signal to help the receiver to detect the beginning and end of data frames. 39.What is the method of data compression by encoding the
length of strings of ones or zeros instead of transmitting all the one and zero bits individually?
40.What is the circuit for digitizing voice at a low data rate by using knowledge of the way in which voice sounds are produced?
41.What is the sampling of an analog signal using a sample- and- hold circuit such that the sample has the same amplitude for its whole duration?
42.___________ is a sampling of an analog signal, so that the sample amplitude follows that of the original signal for the duration of the sample.
43.TRUE/ FASLE: The S/N ratio for either PCM or delta modulation signals can often be improved by using companding.
44.TRUE/ FALSE: Lossless compression eliminates redundant data bits, thereby reducing the bit rate with no effect on signal quality.
45.TRUE/ FALSE: Lossy compression compromises signal quality in order to reduce the bit rate.
TRUE
BIPOLAR CODE UNIPOLAR CODE SUPERFRAME FRAMING BITS
RUN- LENGTH ENCODING VOCODER
FLAT- TOPPED SAMPLING NATURAL SAMPLING TRUE
TRUE TRUE
CHAPTER 8: THE TELEPHONE SYSTEM
1. The first telephone was invented by ____________. 2. DTMF stands for:
ALEXANDER GRAHAM BELL
a. Digital Telephony Multiple Frequency c. Dual-Tone Multifrequency
b. Dial Tone Master Frequency d. Digital Trunk Master Frequency
3. TRUE/ FALSE: The PSTN is of great importance for wireless communication because it links wireless users with other users— both wireless and wired.
4. LATA stands for: 5. A LATA is a:
6. Central offices are connected by:
a. local loops c. both a and b b. trunk lines d. none of the above
7. Local loops terminate at _____________.
8. TRUE/ FALSE: Call blocking occurs when the central office capacity is exceeded
9.TRUE/ FALSE: In telephony, POP stands for Point Of Presence 10. The cable used for local loops is mainly _______________________. 11. TRUE/ FALSE:FITL stands for Fiber In the Toll Loop
12. TRUE/ FALSE: Loading coils were used to reduce the attenuation of voice signals
13. DC current flows through a telephone when it is ___________. 14. The range of DC current that flows through a telephone is: 15. TRUE/ FALSE: The separation of control functions from signal switching is known as common control
16. The typical voltage across a telephone when on-hook is: 17. The typical voltage needed to "ring" a telephone is: 18. TRUE/ FALSE: The bandwidth of voice-grade signals on a telephone system is restricted in order to allow signals to be multiplexed
19. VNL stands for____________.
20. Signal loss is designed into a telephone system to: 21. The reference noise level for telephony is:
22. The number of voice channels in a basic FDM group is: 23. Basic FDM groups can be combined into supergroups, jumbogroups and ______________
24. In telephone system FDM, voice is put on a carrier using: 25. PABX stands for:
26. TRUE/ FALSE: SLIC stands for Subscriber Line Interface Card 27. In DS-1, bits are "robbed" in order to:
28. "Bit-stuffing" is more formally called:
29.TRUE/ FALSE: ISDN stands for Integrated Services Digital Network.
30. Central offices are connected together by ____________________ lines.
C. DUAL-TONE MULTIFREQUENCY TRUE
LOCAL ACCESS AND TRANSPORT AREA A LOCAL CALLING AREA B. TRUNK LINES CENTRAL OFFICE TRUE TRUE TWISTED-PAIR COPPER WIRE TRUE TRUE OFF HOOK 20 MA TO 80 MA TRUE 48 VOLTS 90 VOLTS, 20 HERTZ AC TRUE
VIA NET LOSS
PREVENT OSCILLATION 1 PW 12 MASTERGROUPS SSB PRIVATE AUTOMATIC BRANCH EXCHANGE TRUE CARRY SIGNALING JUSTIFICATION TRUE TRUNK
CHAPTER 9: DATA TRANSMISSION
1. TRUE/ FALSE: PCM and Delta modulation convert analog
2. Data codes are also known as character sets and ________________.
3. _______________ are set of rules that translate alphanumeric characters into binary numbers.
4. TRUE/ FALSE: Baudot code is used for low- data- rate channels like HF radio.
5. _____________ Communications involves synchronizing the transmitter and receiver clocks at the start of each
character.
6. TRUE/ FALSE: UART stands for Universal Asynchronous Receiver- Transmitter.
7. TRUE/ FALSE: Computer data must be first converted from parallel to serial form before being transmitted back to parallel form at the receiver.
8. The type of transmission wherein only one channel is used__________.
9. TRUE/ FALSE: Errors can be detected and corrected within limits by adding redundant information.
10.___________________ is an error control system based on the repetition of data blocks that contain errors.
11.____________ is the addition of extra bits to a data block to avoid accidental generation of a flag pattern.
12._____________ an error detecting method in which the binary number corresponding to the group of bits to be checked is divided by a pre- determined binary number, and the
remainder is transmitted as a check.
13._____________ an error correcting system in which errors are corrected at the receiver using redundant transmitted data without using retransmission requests.
14.TRUE/ FALSE: Huffman coding is a data compression scheme that uses fewer bits to represent more frequently occurring characters or bit patterns and more bits to represent those that occur less frequently.
15.TRUE/ FALSE: Encryption of data is important to ensure privacy.
16._______________ is a data compression scheme that replaces repeated characters or bit patterns with a code indicating the character or pattern and number of repetitions.
17._________ is a line condition representing binary zero.
CHARACTER CODES CHARACTER CODES TRUE ASYNCHRONOUS TRUE TRUE SERIAL TRANSMISSION TRUE ARQ BIT STUFFING CRC FEC TRUE TRUE
RUN- LENGTH ENCODING SPACE
CHAPTER 10:
LOCAL AREA NETWORKS
1.TRUE/ FALSE: Local area networks are small data networks that can be arranged in star, ring, or bus configuration
2. The Internet is a network of ____________________.
3. In a ____________________ network, all nodes are connected to a central computer.
4. In a ____________________-switched network, users have a dedicated channel for the duration of communications.
5. The ____________________ of a network describes how it is physically connected together.
6. Ring networks often use ____________________-passing.
TRUE NETWORKS STAR CIRCUIT TOPOLOGY TOKEN PACKET
7. A ____________________ is a short section of a message in digital form.
8. ____________________ is when two nodes try to seize the same cable at the same time.
9. A ____________________ occurs when two nodes transmit simultaneously on the same baseband cable.
10. In CSMA/CD networks, all collisions must be ____________________.
11. Carrier-Sense means that a node "listens" for the cable to be ____________________ before using it.
12. A "____________________" cable links clusters of computers together.
13. 100BaseT cables can reliably carry up to ____________________ bits per second.
14. In CSMA/CD, packets must have a ____________________ length to ensure that collisions are detected.
15. In CSMA/CD, the ____________________ of a cable is limited to ensure that collisions are detected.
16. A unique numerical address is provided to a node by its ____________________.
17. A 100BaseTX cable is a ____________________ cable.
18. Hubs can be ____________________ to form, in effect, one big hub.
19. A switch looks at the ____________________ of each incoming packet.
20. The effect of a switch is to greatly reduce ____________________. CONTENTION COLLISION DETECTED QUIET BACKBONE 100 MEGA MINIMUM LENGTH NIC FIBER-OPTIC STACKED ADDRESS CONTENTION
CHAPTER 11: WIDE-AREA NETWORKS AND THE INTERNET
1. TRUE/ FALSE: The three major WAN topologies are leased lines, circuit switches and packet switching.
2. A ____________________-Area Network could extend across a nation.
3. A dedicated telephone line can be ____________________ on a monthly basis.
4. The use of digital circuit-____________________ lines is cheaper than dedicated lines.
5. Packet switching is done on a store-and-____________________ network.
6. A ____________________ is a hierarchy of procedures for implementing digital communications.
7. Voltage levels on a cable are specified at the ____________________ layer.
8. Bad frames are usually detected at the ____________________ layer.
9. Setting up a path through the network is done by the ____________________ layer.
10. The X.25 protocol was developed by the ____________________. 11. In X.25, the data-link layer is called the ____________________ layer.
12. In X.25, the network layer is called the ____________________ layer. TRUE WIDE LEASED SWITCHED FORWARD PROTOCOL PHYSICAL DATA-LINK NETWORK CCITT FRAME PACKET VIRTUAL BIT-ERROR LESS 53 REAL REPEATERS BRIDGES
13. The physical route of a ____________________ circuit changes each time it is used.
14. Frame Relay requires channels with low ____________________ rates.
15. Compared to X.25, Frame Relay does ____________________ error checking.
16. All ATM frames contain just ____________________ bytes. 17. Small frame size and a high-speed channel allow ____________________-time communications.
18. ____________________ simply regenerate and retransmit packets in a network.
19. ____________________ look at the address inside a packet to decide whether or not to retransmit it.
20. ____________________ decide the best network path on which to forward a packet.
21.TRUE/ FALSE: The processing required to store and forward packets of different lengths is greater than that required for packets of a fixed length. More processing implies more time per packet, which implies fewer packets per second through the network.
22. TRUE/ FALSE: Every time a packet is forwarded on to the next store-and-forward node in the network, it is considered tobe one "hop".
23. TRUE/ FALSE: Each packet contains a number representing the maximum number of allowed hops. At each hop, thisnumber is reduced by one. When it gets to zero, the packet is deleted from the network.
ROUTERS TRUE TRUE TRUE
CHAPTER 12:
DIGITAL MODULATION AND MODEMS
1. Digital transmission uses frequency, phase, and __________ amplitude variations, just as does analog transmission.2. The response to RTS is ____________________.
3. FSK stands for Frequency-Shift ____________________. 4. DSR stands for ____________________ Set Ready.
5. QAM stands for ____________________ Amplitude Modulation. 6. The number of symbols per second is called the
____________________ rate.
7. The 2 bits of information in a QPSK symbol is called a ____________________.
8. QPSK uses ____________________ different phase angles. 9. DPSK stands for ____________________ PSK.
10. The QAM amplitude-phase combinations are shown with a ____________________ diagram.
11. ITU stands for International _________________________ Union. 12. In QAM modems, ____________________ coding adds extra bits to improve performance on a noisy line.
13. ____________________ is used in a high-speed modem to compensate for uneven frequency and phase response on a line. 14. The maximum allowed speed for a modem on a dial-up line is about ____________________ bps.
15. The nominal maximum speed on an RS-232 cable is ____________________ bps.
16. How many points will be on the constellation diagram of a QAM
AMPLITUDE CTS KEYING DATA QUADRATURE BAUD DIBIT FOUR DELTA CONSTELLATION TELECOMMUNICATIONS TRELLIS EQUALIZATION 54K 20K 16 HARDWARE
system using 8 phase angles and 2 amplitude levels?
17. Between hardware flow control and software flow control, ____________________ flow control is referred.
18. A voltage higher than ____________________ volts should be considered a high on an RS-232 receiver.
19. A ____________________ modem cable is used to connect two DTEs via their serial ports.
20. ADSL stands for ____________________ DSL.
21. A typical CATV system is organized as a ____________________ network.
22. In a CATV system using cable modems, a ____________________ is used to put several channels of data into fiber-optic backbone. 23. ____________________ is the process of synchronizing
transmitted data from cable modems to a CMTS.
3 NULL ASYMMETRICAL TREE CMTS RANGING
CHAPTER 13: MULTIPLEXING AND MULTIPLE-ACCESS TECHNIQUES 1. Multiplexing allows many signals to ____________________ a
channel.
2. Three methods of multiple access are FDMA, TDMA, and ____________________.
3. In FDM, each signal uses part of the bandwidth ____________________ of the time.
4. In TDM, each signal uses all of the bandwidth ____________________ of the time.
5. Using CDMA on a radio channel, all signals can transmit ____________________ of the time.
6. DS-1 is an example of ____________________-division multiplexing. 7. The AM radio band is an example of ____________________-division multiplexing.
8. A DS-1 frame contains one sample from each of ____________________ channels.
9. T1 uses the ____________________ line code.
10. Each DS-1 frame contains a total of ____________________ bits. 11. A DS-1 frame is transmitted at a rate of ____________________ bits per second.
12. Each sample in a DS-1 frame contains ____________________ bits. 13. A group of twelve DS-1 frames is called a ____________________. 14. Switching signals from one line to another is called
____________________ switching.
15. Moving PCM samples from one time slot to another is called ____________________ switching.
16. The deep fades caused by signal-cancellation due to reflection are called ___________________ fading.
17. A PN sequence is a ____________________-random noise sequence.
18. One method of spread-spectrum is frequency ____________________.
19. It is ____________________ to jam a spread-spectrum signal. 20. It is ____________________ to eavesdrop on a spread-spectrum signal.
21. The extra bits added to the data in direct-sequence spread-spectrum are called ____________________.
SHARE CDMA ALL PART ALL TIME FREQUENCY 24 AMI 193 1.544 MEG 8 SUPERFRAME SPACE TIME RAYLEIGH PSEUDO HOPPING DIFFICULT DIFFICULT CHIPS TEN CODE ORTHOGONAL
22. A chipping-rate of at least ____________________ times the bit rate of the data is common.
23. The 'C' in CDMA stands for ____________________. 24. In a frequency-hopping CDMA system, when no two
transmitters use the same frequency at the same time the PN sequences are said to be ____________________.
CHAPTER 14: TRANSMISSION LINES
1. A transmission line has 2.5 pF of capacitance per foot and 100 nH of inductance per foot. Calculate its characteristic impedance. 2. Two wires with air as a dielectric are one inch apart. The diameter of the wire is .04 inch. Calculate, approximately, its characteristic impedance.
3. If a coaxial cable uses plastic insulation with a dielectric constant Îr = 2.6 , what is the velocity factor for the cable? 4. Twisted-pair cables are transmission lines for relatively ____________________ frequencies.
5. To analyze a transmission line, it is necessary to use ____________________ parameters instead of lumped ones.
6. The increase of a wire's resistance with frequency is called the ____________________ effect.
7. The increase of a wire's resistance with frequency is caused by the ____________________ field inside the wire.
8. Dielectrics become more ____________________ as the frequency increases.
9. The inductance and capacitance of a cable are given per unit ____________________.
10. Characteristic impedance is sometimes called ____________________ impedance.
11. A cable that is terminated in its characteristic impedance is called a ___________________ line.
12. A pulse sent down a cable terminated in a short-circuit will reflect with the __________________ polarity.
13. The apparently stationary pattern of waves on a mismatched cable is called a ____________________ wave.
14. SWR stands for ____________________-wave ratio. 15. The ideal value for SWR is ____________________. 16. Transmission line impedances can be found using a ____________________ chart.
17. Short transmission-line sections called ____________________ can be used as capacitors or inductors.
18. Any cable that radiates energy can also ____________________ energy.
19. A ____________________-dB loss in a cable means only half the power sent reaches the load.
20. It is often best to measure SWR at the ____________________ end of a cable. Z0 = 200 OHMS 386 OHMS 0.62 LOW DISTRIBUTED SKIN MAGNETIC LOSSY LENGTH SURGE MATCHED OPPOSITE STANDING STANDING ONE SMITH STUBS ABSORB 3 LOAD
CHAPTER 15: RADIO-WAVE PROPAGATION
same permeability as free space. What is the characteristic impedance of that dielectric?
2. Radio waves were first demonstrated by ____________________. 3. Radio waves are ____________________ electromagnetic waves. 4. The propagation speed of radio waves in free space is
____________________ m/sec.
5. Electromagnetic radiation can be thought of as a stream of particles called ____________________.
6. Unlike sound or water waves, radio waves do not need a ____________________ to travel through.
7. The dielectric strength of clean dry air is about ____________________ volts per meter.
8. Waves from an ____________________ source radiate equally in all directions.
9. The wavefront of a point source would have the shape of a ____________________.
10. At a far distance from the source, a radio wavefront looks like a flat ____________________-wave.
11. The polarization of a radio wave is the direction of its ____________________ field.
12. The electric field of a radio wave is ____________________ to its magnetic field.
13. Both the electric and magnetic fields of a radio wave are ____________________ to its propagation direction.
14. With ____________________ polarization, the direction of a radio wave's electric field rotates as it travels through space.
15. An antenna is said to have ____________________ in a certain direction if it radiates more power in that direction than in other directions.
16. The watts per square meter of a radio wave
____________________ as the wave-front moves through space. 17. Reflection of plane-waves from a smooth surface is called ____________________ reflection.
18. ____________________ is the "bending" of radio waves as they travel across the boundary between two different dielectrics.
19. The process of ____________________ makes radio waves appear to "bend around a corner".
20. ____________________ waves travel from transmitter to receiver in a "line-of-sight" fashion.
21. ____________________ waves are vertically polarized radio waves that travel along the earth's surface.
HERTZ TRANSVERSE 300 ´ 106 PHOTONS MEDIUM 3 ´ 106 ISOTROPIC SPHERE PLANE ELECTRIC PERPENDICULAR PERPENDICULAR CIRCULAR GAIN DECREASE SPECULAR REFRACTION DIFFRACTION SPACE GROUND CHAPTER 16: ANTENNA
1. TRUE/ FALSE: The real part of an antenna's input impedance is due to the radiated signal.
2. A half-wave dipole is sometimes called:
3. TRUE/ FALSE:The end-to-end length of a half-wave dipole antenna is actually slightly shorter than a half-wavelength 4. The radiation of energy from an antenna can be seen in the _____________of the antenna
5. TRUE/ FALSE: Measured on the ground, the field strength of a horizontally polarized half-wave dipole antenna is strongest in two
TRUE A HERTZ ANTENNA TRUE RADIATION RESISTANCE TRUE DIRECTIVITY
directions.
6. The ability of an antenna to radiate more energy in one direction than in other directions is called:
7. An antenna is the interface between the transmission line and ____________________.
8. Hertz antenna is another name for a half-wave ____________________.
9. The length of a half-wave dipole is about ____________________ % of a half-wave in free space.
10. The ____________________ resistance is the portion of an
antenna's input impedance due to transmitted radio waves leaving the antenna.
11. Input impedance at the center feed point of a resonant half-wave dipole is about ____________________W.
12. Input impedance at the center feed point of a resonant folded dipole is about ____________________ W.
13. The vertical angle of radiation is called the angle of ____________________.
14. Antenna radiation patterns are typically drawn on graphs with ____________________ coordinates.
15. As compared to a ____________________ source, a half-wave dipole has a gain of about 2 dBi.
16. Antenna gain measured in ____________________ is with reference to a half-wave dipole.
17. A horizontally mounted dipole will radiate waves with ____________________ polarization.
18. A folded dipole has ____________________ bandwidth than a standard dipole.
19. A monopole antenna is typically mounted in the ____________________ direction.
20. The length of a typical monopole antenna is ____________________ wavelength.
21. A monopole antenna mounted high on a tower typically uses a ____________________ plane.
22. A vertical antenna has an _________________________ radiation pattern for ground-based receivers.
23. The number of driven elements in a Yagi antenna is typically ____________________.
24. The reflector on a Yagi antenna is called a ____________________ element.
25. An LPDA is a ____________________ dipole array.
26. If an LPDA had five elements, the number of driven elements it had would be ____________________.
27. All the waves that hit the surface of a parabolic antenna merge at the ____________________.
28. A ____________________ beam has all its individual rays parallel to each other.
29. A microwave ____________________ antenna is essentially an extension of a waveguide.
30. An ____________________ chamber is often used to test microwave antennas. SPACE DIPOLE 95 RADIATION 70 280 – 300 ELEVATION POLAR POINT ISOTROPIC DBD HORIZONTAL WIDER VERTICAL ONE-QUARTER GROUND OMNIDIRECTIONAL ONE PARASITIC LOG-PERIODIC FIVE FOCUS COLLIMATED HORN ANECHOIC
1. ____________________ is the effect of a pulse "spreading out" as it travels through a waveguide.
2. The electric field is ____________________ along the walls of a rectangular waveguide.
3. The waveguide mode with the lowest cutoff frequency is the ____________________ mode.
4. In TE10 mode, the ____________________ field peaks in the middle of the waveguide cross section.
5. In TE20 mode, the electric field has ____________________ peaks in the waveguide cross section.
6. In a circular waveguide, ____________________ mode is used because of its circular symmetry.
7. A waveguide acts as a ____________________-pass filter.
8. In a waveguide, group velocity is always ____________________ than the speed of light.
9. In a waveguide, phase velocity is always ____________________ than the speed of light.
10. In a waveguide, impedance ____________________ as frequency increases.
11. A ____________________ TEE is a combination of E-plane and H-plane TEES.
12. The Q of a resonant cavity is very ____________________ compared to lumped LC circuits.
13. A wavemeter is a resonant ____________________ with an adjustable plunger.
14. A Gunn device oscillates because of its negative ____________________.
15. Both magnetrons and TWTs are slow ____________________ tubes.
16. Both klystrons and TWTs are ____________________-beam tubes. 17. A ____________________ antenna is just a waveguide with a hole in it.
18. A ____________________ antenna is a flat piece of copper on an insulating substrate with a ground plane on the other side.
19. The radar cross section of a target is typically ____________________ than its actual size.
20. The frequency of the returned signal will be
____________________ than the transmitted signal if the target is moving toward the radar antenna.
DISPERSION ZERO DOMINANT ELECTRIC TWO TM01 HIGH SLOWER FASTER DECREASES HYBRID HIGH CAVITY RESISTANCE WAVE LINEAR SLOT PATCH SMALLER HIGHER
CHAPTER 18: TERRESTRIAL MICROWAVE COMMUNICATION SYSTEMS 1. One microwave link is called a ____________________.
2. A line-of-sight microwave link operating at 4 GHz has a
separation of 40 km between antennas. An obstacle in the path is located midway between the two antennas. By how much must the beam clear the obstacle?
3.TRUE/ FALSE: The typical reliability of a microwave system is 99.99%
4. Adding more links causes ____________________ in a digital microwave system.
5. In microwave systems, it is more convenient to use noise ____________________ than noise figure in calculations.
HOP 16.4 METERS TRUE JITTER TEMPERATURE NOISE DENSITY FADING
6. In digital microwave systems, the energy per bit per ____________________ is a key parameter.
7. Multipath reception can cause 20 dB or more of ____________________.
8. Two antennas stacked one above the other on a tower is an example of ___________________ diversity in a microwave system. 9. The ability to use two frequencies simultaneously is an example of ____________________.
10. Microwave systems generally use less than ____________________ watts of power.
11. ____________________ are necessary in a microwave system that extends beyond the line-of-sight distance.
12. Analog microwave systems use both IF and ____________________ repeaters.
13. Microwave digital radio techniques reduce the accumulation of ____________________ as a signal goes from link to link.
14. MMDS is unidirectional, but ____________________ is bidirectional.
15. If the line-of-sight distance for an optical beam is 12 km, what would it be, approximately, for a microwave beam?
16. A transmitter and receiver operating at 1 GHz are separated by 10 km. How many dBm of power gets to the receiver if the
transmitter puts out 1 Watt, and both the sending and receiving antennas have a gain of 20 dBi?
SPACE DIVERSITY TEN REPEATERS BASEBAND NOISE LMDS 16 KM –42.4 DBM CHAPTER 19: TELEVISION
1.TRUE/ FALSE: NTSC stands for National Television Systems Committee
2. The ____________________ standard for TV has been in use since 1953.
3. Video systems form pictures by a ____________________ process. 4. During the horizontal blanking interval, the electron beam ____________________ from right to left.
5. The NTSC specifies a ____________________ video signal. 6. The ____________________ ratio of a CRT screen is the ratio of width to height.
7. Brightness information is called ____________________. 8. Color information is called ____________________.
9. The blanking period before the sync pulse is called the front ____________________.
10. Odd and even fields are identified by the ____________________ of the vertical sync pulse.
11. Each horizontal scan line takes ____________________ microseconds, not including blanking.
12. Horizontal blanking lasts ____________________ microseconds. 13. Vertical blanking lasts about ____________________ milliseconds. 14. Picture elements are called ____________________.
15. The maximum number of scan lines under NTSC is ____________________.
16. The human eye is most sensitive to the color ____________________.
17. The color sub-carrier frequency is approximately
TRUE NTSC SCANNING RETRACES COMPOSITE ASPECT LUMINANCE CHROMA/ CHROMINANCE PORCH POSITION 62.5 10 1.3 PIXELS 525 GREEN 3.58 SEPARATE ULTOR 20 TO 30 PHOSPHOR FLYBACK
____________________ MHz.
18. SAP stands for ____________________ audio program. 19. The second anode of a CRT is often called the ____________________.
20. The accelerating voltage for a color CRT is about ____________________ kV.
21. The inside of a CRT's face-plate is coated with ____________________ to generate the picture.
22. The horizontal output transformer is called the ____________________ transformer.
23. A good way to separate luma from chroma is to use a ____________________ filter.
24. The color ____________________ turns off the color circuitry when a color TV is receiving a monochrome signal.
25. Signal levels in cable TV systems are usually measured in ____________________.
26. The antenna for a CATV system is located at the ____________________ end.
27. A ____________________ shows a color-bar signal with predetermined levels and phases.
28. Color intensity is called ____________________.
29. The ____________________ of the chroma signal represents the color hue.
30. The ____________________ controls in a color TV adjust the electron beams to strike the correct color phosphor dots. 31. The ____________________ controls in a color TV adjust the electron beams to strike the correct triad of phosphor dots.
COMB KILLER DBMV HEAD VECTORSCOPE SATURATION PHASE PURITY CONVERGENCE
CHAPTER 20: SATELLITE COMMUNICATIONS
1. A satellite in geosynchronous orbit takes ____________________ hours to complete one orbit.
2. The ____________________ is the signal path from the earth station to the satellite.
3. The area on the earth that is "covered" by a satellite is called its:
4. TRUE/ FALSE: The velocity required to stay in orbit is higher close to the earth than far from the earth.
5. An antenna is aimed by adjusting the two "look angles" called: 6. The ____________________ is the signal path from the satellite to the earth station.
ANS: 7.A satellite in a ____________________ orbit appears to stay directly above one spot on the equator.
8. Non-geostationary satellites are sometimes called ____________________ satellites.
9. A geosynchronous orbit is about ____________________ km above the earth.
10. A ____________________ is an outline of the area on the earth's surface that a satellite broadcasts to.
11. All satellite orbits are ____________________ in shape.
12. The ____________________ is the distance of a satellite's closest approach to the earth.
24 UPLINK FOOTPRINT TRUE AZIMUTH AND ELEVATION DOWNLINK GEOSTATIONARY ORBITAL 35,780 FOOTPRINT ELLIPTICAL PERIGEE APOGEE AZIMUTH ELEVATION DECLINATION
13. The ____________________ is a satellite's farthest distance from the earth.
14. An antenna's ____________________ is its angular direction between east and west.
15. An antenna's ____________________ is its vertical angle with respect to the earth's surface.
14. An antenna's ____________________ is the angle by which it is offset from the earth's axis.
16. Satellites using the ____________________ band operate on 12 GHz.
17. The time for a signal to make a round trip via satellite is about ____________________ milliseconds.
18. A ____________________ is a type of repeater used on communications satellites.
19. Both the gain and the beamwidth of a dish antenna depend on its ____________________.
20. VSAT systems commonly use a ____________________ network configuration.
21. To date, LEO satellite systems have been a financial ____________________.
22. C-band antennas are ____________________ than Ku-band antennas.
23. The "payload" on a communications satellite consists of: 24. "Station-keeping" refers to:
25. TRUE/ FALSE: DBS stands for direct-broadcast satellite 26. A reduction in TWT power for linearity is called:
27. TVRO stands for:
28. A typical VSAT system is configured as a:
29. TRUE/ FALSE: For real-time communication, LEO systems require a constellation of satellites
KU 500 TRANSPONDER DIAMETER STAR FAILURE LARGER TRANSPONDERS ORBITAL ADJUSTMENTS TRUE BACKOFF TELEVISION RECEIVE ONLY STAR TRUE
CHAPTER 21: CELLULAR RADIO
1. TRUE/ FALSE: IMTS stands for improved mobile telephone service.
2. TRUE/ FALSE: AMPS stands for advanced mobile phone service.
3. TRUE/ FALSE: Personal communications systems work best when they are portable, connected to the public switched telephone network, and widely available at reasonable cost. 4. _______________ is the North American first generation
cellular radio standard using analog FM.
5. _______________ is a switching facility connecting cellular telephone base stations to each other and to the other public switched telephone network.
6. A company that acts as a carrier of radiotelephone signal is known as ___________.
7. TRUE/ FALSE: Forward cell is the communication from a cell site or repeater to the mobile unit.
8. A communication channel from mobile station to base station is known as _______.
9. ________ is the transfer of a call in progress from one cell site to another. TRUE TRUE TRUE AMPS MSC/MTSO RADIO COMMON CARRIER TRUE REVERSE CHANNEL HANDOFF TRUE 30KHZ
