Deck 4: Communications Circuits

Question 1

A(n)_________ generates a waveform by converting direct-current energy to an alternating current.
A.amplifier
B.synthesizer
C.oscillator
D.feedback loop

Answer 1

oscillator

Question 2

___________ manifests itself as an opposition to current flow in ac circuits and is measured in ohms.
A.Resistance
B.Reactance
C.Impedance
D.Capacitance

Answer 2

Reactance

Question 3

What is commonly used in single-sideband systems to attenuate the unwanted sideband?
A.Passband
B.Stopband
C.Wire leads
D.Crystal filter

Answer 3

Crystal filter

Question 4

What is the most common method of detecting an SSB signal?
A.Phase-locked loop
B.Mechanical filter
C.Product detector
D.Voltage-controlled oscillator

Question 5

What type of filter is commonly used in single-sideband systems to attenuate the unwanted sideband?
A.Crystal
B.Bandpass
C.Mechanical
D.Constant- k

Question 6

What does the application of two different input frequencies produce?
A.Cross products
B.Power series
C.Mechanical vibrations
D.Frequency sensitivity

Question 7

The disadvantages of DDS include the limit on maximum output frequency and higher ___________.
A.cost
B.output waveforms
C.phase noise
D.analog units

Question 8

What is the purpose of a balanced modulator?
A.To produce an output frequency that varies in response to changes in a control voltage.
B.To change frequency in response to a DC control voltage applied to it.
C.To allow a range of frequencies to be generated from a stable, single-frequency reference.
D.To suppress the carrier, leaving only the two sidebands.

Question 9

Which of the following configurations of an LC or RC filter is defined as a sharper transition from passband to stopband than other configurations,but with ripple on both?
A.Chebyshev
B.Cauer
C.Bessel
D.Butterworth

Question 10

A crystal oscillator is one that uses a piezoelectric crystal as what type of element of an LC circuit?
A.External
B.Stable
C.Inductive
D.Inherent

Question 11

Resonance is the condition where inductive and capacitive reactances are ___________.
A.equal
B.reduced
C.increased
D.rejected

Question 12

Synthesizers are found in any device that must operate over a range of frequencies. Which of the following is an example of such a device?
A.Resonant tank circuits
B.Cellular phones
C.Rotary dial phones
D.Landline phones

Question 13

Amplifiers are classified by the amount of time during each input cycle that the active device within the circuit conducts __________.
A.harmonic content
B.pulse-width modulation
C.high linearity
D.current

Question 14

Which of the following is an advantage of mechanical filters?
A.New technology
B.Extreme flexibility
C.Excellent rejection characteristics
D.Compatible with larger equipment

Question 15

The rate of attenuation is the steepness of the filter's response curve. What term is used to describe this rate?
A.Tank circuit
B.Dissipation
C.Roll-off
D.Band-reject

Question 16

Why are virtually all oscillators used in communications applications the feedback type?
A.They are capable of producing highly pure sine waves.
B.The currents in the diodes and the currents in the transistors are the same.
C.They use RC timing circuits to generate nonsinusoidal waveforms.
D.They allow waveform distortion.

Question 17

Which of the following would be an application where a SAW filter would be used?
A.Miniaturized equipment
B.Radar systems
C.IF transformers
D.Single-sideband systems

Question 18

Which of the following criteria would help you to choose the oscillator type for use in electronic circuits?
A.Input frequency required
B.Frequency stability required
C.Range of frequency output
D.Allowable waveforms

Question 19

From what material are ceramic filters normally constructed?
A.Quartz
B.Crystal
C.Lead zirconate-titanate
D.Lithium niobate

Question 20

A__________ is where the currents in the diodes and the currents in the transistors are the same.
A.current mirror
B.push-pull
C.cutoff
D.conduction angle

Question 21

When are CMOS devices preferred?
A.When power consumption is a consideration.
B.When much smaller spacing between output frequencies is necessary.
C.When stability is directly governed by the stability of the reference input.
D.When synthesizer frequency range is determined by the range of frequencies over which the VCO can operate.

Question 22

The PLL is said to be in lock whenever the __________ can be matched to the reference.
A.free-running frequency
B.VCO frequency
C.capture range
D.capacitance

Question 23

Frequency multiplication introduces ___________.
A.noise
B.high reference frequencies
C.drift problems
D.output waveform

Question 24

Which of the following is needed in a reference oscillator to produce many frequencies?
A.Low-pass filter
B.Varactor diode
C.Phase comparator
D.One crystal

Question 25

To what does any modern,"frequency-agile" communication system owe its existence?
A.Crystal oscillators
B.Amplifiers
C.Parallel LC tank circuits
D.Phase-locked loops