Quiz 4: Communications Circuits

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

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

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

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

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

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.

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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