Blake: MCQ in Radio-Frequency Circuits

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(Last Updated On: March 27, 2020)

Blake: MCQ in Radio-Frequency Circuits

This is the Multiple Choice Questions in Chapter 2: Radio-Frequency Circuits from the book Electronic Communication Systems by Roy BlakeBlake: MCQ in Radio-Frequency Circuits. If you are looking for a reviewer in Communications Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

See also: MCQ in Electronic Communication Systems by George Kennedy

Start Practice Exam Test Questions

Choose the letter of the best answer in each questions.

MULTIPLE CHOICE

1. The time it takes a charge carrier to cross from the emitter to the collector is called:

a. base time

b. transit time

c. charge time

d. Miller time

View Answer:

Answer: Option B

Solution:

2. A real capacitor actually contains:

a. capacitance and resistance only

b. capacitance and inductance only

c. capacitance, inductance, and resistance

d. reactance only

View Answer:

Answer: Option C

Solution:

3. Bypass capacitors are used to:

a. remove RF from non-RF circuits

b. couple RF around an amplifier

c. neutralize amplifiers

d. reduce the Miller effect

View Answer:

Answer: Option A

Solution:

4. A resonant circuit is:

a. a simple form of bandpass filter

b. used in narrowband RF amplifiers

c. both a and b

d. none of the above

View Answer:

Answer: Option C

Solution:

5. Loading down a tuned-circuit amplifier will:

a. raise the Q of the tuned circuit

b. lower the Q of the tuned circuit

c. “multiply” the Q

d. have no effect on Q

View Answer:

Answer: Option B

Solution:

6. The “Miller Effect” can:

a. cause an amplifier to oscillate

b. cause an amplifier to lose gain

c. reduce the bandwidth of an amplifier

d. all of the above

View Answer:

Answer: Option D

Solution:

7. The Miller Effect can be avoided by:

a. using a common-emitter amplifier

b. using a common-base amplifier

c. increasing the Q of the tuned circuit

d. it cannot be avoided

View Answer:

Answer: Option B

Solution:

8. In a BJT, the Miller Effect is due to:

a. inductance of collector lead

b. collector-to-emitter capacitance d

c. base-to-emitter capacitance

d. base-to-collector capacitance

View Answer:

Answer: Option D

Solution:

9. In RF amplifiers, impedance matching is usually done with:

a. RC coupling

b. transformer coupling

c. direct coupling

d. lumped reactance

View Answer:

Answer: Option B

Solution:

10. Neutralization cancels unwanted feedback by:

a. adding feedback out of phase with the unwanted feedback

b. bypassing the feedback to the “neutral” or ground plane

c. decoupling it

d. none of the above

View Answer:

Answer: Option A

Solution:

11. For a “frequency multiplier” to work, it requires:

a. a nonlinear circuit

b. a linear amplifier

c. a signal containing harmonics

d. an input signal that is an integer multiple of the desired frequency

View Answer:

Answer: Option A

Solution:

12. A sinusoidal oscillation from an amplifier requires:

a. loop gain equal to unity

b. phase shift around loop equal to 0 degrees

c. both a and b, but at just one frequency

d. none of the above

View Answer:

Answer: Option C

Solution:

13. The conditions for sinusoidal oscillation from an amplifier are called:

a. the loop-gain criteria

b. the Hartley criteria

c. the Bode criteria

d. the Barkhausen criteria

View Answer:

Answer: Option D

Solution:

14. The Hartley oscillator uses:

a. a tapped inductor

b. a two-capacitor divider

c. an RC time constant

d. a piezoelectric crystal

View Answer:

Answer: Option A

Solution:

15. The Colpitts VFO uses:

a. a tapped inductor

b. a two-capacitor divider

c. an RC time constant

d. a piezoelectric crystal

View Answer:

Answer: Option B

Solution:

16. The Clapp oscillator is:

a. a modified Hartley oscillator

b. a modified Colpitts oscillator

c. a type of crystal-controlled oscillator

d. only built with FETs

View Answer:

Answer: Option B

Solution:

17. A varactor is:

a. a voltage-controlled capacitor

b. a diode

c. used in tuner circuits

d. all of the above

View Answer:

Answer: Option D

Solution:

18. Crystal-Controlled oscillators are:

a. used for a precise frequency

b. used for very low frequency drift (parts per million)

c. made by grinding quartz to exact dimensions

d. all of the above

View Answer:

Answer: Option D

Solution:

19. If two signals, Va = sin(ωat) and Vb = sin(ωbt), are fed to a mixer, the output:

a. will contain ω1 = ωa + ωb and ω2 = ωa – ωb

b. will contain ω1 = ωa / ωb and ω2 = ωb / ωa

c. will contain ω1 = (ωa + ωb ) / 2

d. none of the above

View Answer:

Answer: Option A

Solution:

20. In a balanced mixer, the output:

a. contains equal (balanced) amounts of all input frequencies

b. contains the input frequencies

c. does not contain the input frequencies

d. is a linear mixture of the input signals

View Answer:

Answer: Option C

Solution:

21. “VFO” stands for:

a. Voltage-Fed Oscillator

b. Variable-Frequency Oscillator

c. Varactor-Frequency Oscillator

d. Voltage-Feedback Oscillator

View Answer:

Answer: Option B

Solution:

22. A “frequency synthesizer” is:

a. a VCO phase-locked to a reference frequency

b. a VFO with selectable crystals to change frequency

c. a fixed-frequency RF generator

d. same as a mixer

View Answer:

Answer: Option A

Solution:

COMPLETION

1. Generally, conductor lengths in RF circuits should be ____________________.

View Answer:

Answer: short

Solution:

2. At UHF frequencies and above, elements must be considered as ____________________ instead of as being “lumped”.

View Answer:

Answer: distributed

Solution:

3. When one side of a double-sided pc board is used for ground, it is called a ____________________.

View Answer:

Answer: ground-plane

Solution:

4. Interactions between parts of an RF circuit can be reduced by using ____________________ between them.

View Answer:

Answer: shielding

Solution:

5. In high-frequency RF circuits, the placement of wires and ____________________ can be critical.

View Answer:

Answer: components

Solution:

6. A ____________________ circuit is used to remove RF from the DC voltage bus.

View Answer:

Answer: decoupling

Solution:

7. A ____________________ capacitor is used to short unwanted RF to ground.

View Answer:

Answer: bypass

Solution:

8. The bandwidth of a tuned-circuit amplifier depends on the ____________________ of the tuned circuit.

View Answer:

Answer: Q

Solution:

9. A value of ____________________ or more for Q is required for the approximate tuned circuit equations to be valid.

View Answer:

Answer: 10

Solution:

10. In a class C RF amplifier, the ____________________ extracts one frequency from all the harmonics contained in the device current (e.g. collector current).

View Answer:

Answer: tuned circuit

Solution:

11. Using additional feedback to compensate for “stray” feedback is called ____________________.

View Answer:

Answer: neutralization

Solution:

12. A Colpitts oscillator uses a ____________________ voltage divider to provide feedback.

View Answer:

Answer: capacitive

Solution:

13. Electrically, a piezoelectric crystal has both a ____________________ and a ____________________ resonant frequency.

View Answer:

Answer: series, parallel

Solution:

14. To produce sum and difference frequencies, a mixer must be a non-____________________ circuit.

View Answer:

Answer: linear

Solution:

15. At some bias point, a diode or a transistor can act as a ____________________-law mixer.

View Answer:

Answer: square

Solution:

SHORT ANSWER

1. What inductance would you use with a 47-pF capacitor to make a tuned circuit for 10 MHz?

View Answer:

Answer: 5.4 µH

Solution:

2. What value of Q is required for a 10-MHz tuned circuit to have a bandwidth of 100 kHz?

View Answer:

Answer: 100

Solution:

3. A tuned-circuit amplifier with a gain of 10 is being used to make an oscillator. What should be the value of the feedback ratio to satisfy the Barkhausen criteria?

View Answer:

Answer: 0.1

Solution:

4. What is the advantage of a Clapp oscillator compared to a Colpitts oscillator?

View Answer:

Answer: It is more stable because it “swamps” the device capacitance with large value capacitors in the feedback divider.

Solution:

5. If a varactor has a capacitance of 90 pF at zero volts, what will be the capacitance at 4 volts?

View Answer:

Answer: 30 Pf

Solution:

6. An oscillator has a frequency of 100 MHz at 20°C, and a tempco of +10 ppm per degree Celsius. What will be the shift in frequency at 70°C? What percentage is that?

View Answer:

Answer: 50 kHz, 0.05%

Solution:

7. Two sinusoidal signals, V1 and V2, are fed into an ideal balanced mixer. V1 is a 20-MHz signal; V2 is a 5- MHz signal. What frequencies would you expect at the output of the mixer?

View Answer:

Answer: 15 MHz and 25 MHz

Solution:

8. Suppose the phase-locked-loop frequency synthesizer of Figure 2.39 has a reference frequency of 1 MHz and a fixed-modulus divider of 10. What should be the value of the programmable divider to get an output frequency of 120 MHz?

View Answer:

Answer: 12

Solution:

Complete List of MCQ in Electronic Communication Systems by Blake

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