R4RIN – MCQs, Mock Tests | Electrical engineering Microwave Engineering MCQs Set-7

Field effect transistors are different from BJTs in that they are _________

1. monopolar devices
2. bipolar devices
3. bidirectional device
4. none of the mentioned

✅ Correct Answer: 1

GaAs MESFET –metal semiconductor field effect transistor are one of the widely used categories of FETs.

1. true
2. false
3.
4.

✅ Correct Answer: 1

At frequencies above 10GHz, MESFET are not suitable for microwave applications due to parasitic effects.

1. true
2. false
3.
4.

✅ Correct Answer: 2

Advantage of using GaAs in MESFET as compared to use of silicon is:

1. GaAs are cost effective
2. they have higher mobility
3. they have high resistance for flow of current in the reverse direction
4. none of the mentioned

✅ Correct Answer: 2

In MESFET, an applied signal at the gate modulates the electron carriers; this produces _______ in the FET.

1. voltage amplification
2. voltage attenuation
3. electron multiplication
4. electron recombination

✅ Correct Answer: 1

The frequency of operation of an FET is limited by:

1. drain to source voltage
2. gate to source voltage
3. gate length
4. effective area of an FET

✅ Correct Answer: 3

_________ is a non linear circuit that converts DC power to an AC waveform of desired frequency based on the oscillator design.

1. Attenuator
2. Amplifier
3. Oscillator
4. None of the mentioned

✅ Correct Answer: 3

The transfer function of an RF oscillator is given by:

1. A/ (1-AH (ω))
2. A/ (1+AH (ω))
3. A/ (-1+AH (ω))
4. 1/ (1-AH (ω))

✅ Correct Answer: 1

The criterion on which oscillations are produced in the oscillator circuit is called:

1. Shannon’s criteria
2. Barkhausen criteria
3. Colpitts criteria
4. None of the mentioned

✅ Correct Answer: 2

Colpitts oscillator operating at 50 MHz has an inductor in the feedback section of value 0.10µH. then the values of the capacitors in the feedback section is:

1. 100 pF, 100 pF
2. 100 pF, 50 pF
3. 70 pF, 130 pF
4. 80 pF, 60 pF

✅ Correct Answer: 1

An inductor is operating at frequency of 50 MHz. Its inductance is 0.1 µH, and then the series resistance associated with the inductor is: (Qo=100)

1. 0.31 Ω
2. 1.32 Ω
3. 1 Ω
4. 1.561 Ω

✅ Correct Answer: 1

Hartley oscillator has inductance values of 12 mH and 4 mH in the feedback section and a capacitor of 4 nF. Then the resonant frequency of the circuit is:

1. 19.89 kHz
2. 25 kHz
3. 45 kHz
4. 12 kHz

✅ Correct Answer: 1

Colpitts oscillator in the feedback section has an inductance of 4 mH and capacitors of 12 nH and 4 nH. Then the resonant frequency of Colpitts oscillator is:

1. 50.4 kHz
2. 35.1 kHz
3. 45.9 kHz
4. None of the mentioned

✅ Correct Answer: 3

One condition to be satisfied in an oscillator circuit so that stable oscillations are produced is:

1. positive feedback is to be achieved
2. negative feedback is to be achieved
3. 180degree phase shift is required between the transistor input and output.
4. none of the mentioned

✅ Correct Answer: 3

In an oscillator, the resonant feedback circuit must have must have a low Q in order to achieve stable oscillation.

1. true
2. false
3.
4.

✅ Correct Answer: 2

Quartz crystals are more efficient as a feedback network because:

1. less circuit complexity
2. cost effective
3. crystals operate at high voltage levels
4. LC circuits have unloaded Q of a few hundreds

✅ Correct Answer: 4

Quartz crystal and tourmaline used in oscillators work on the principle of:

1. photo electric effect
2. piezo electric effect
3. Raman effect
4. black body radiation

✅ Correct Answer: 2

A quartz crystals equivalent circuit is a series LCR circuit and has a series resonant frequency.

1. true
2. false
3.
4.

✅ Correct Answer: 2

Quartz crystal is used in the _______region, where the operating point of the crystal is fixed.

1. resistive
2. inductive reactance
3. capacitive reactance
4. none of the mentioned

✅ Correct Answer: 2

In the plot of reactance v/s frequency of a crystal oscillator, the reactance between series resonant frequency and parallel resonant frequency is:

1. capacitive
2. inductive
3. both capacitive and inductive
4. none of the mentioned

✅ Correct Answer: 2

In the equivalent circuit of a quartz crystal, LCR arm has an inductance of 4 mH and capacitor has a value of 4nF, then the series resonant frequency of the oscillator is:

1. 0.25 MHz
2. 2.5 MHz
3. 25 MHz
4. 5 MHz

✅ Correct Answer: 1

The equivalent circuit of a quartz crystal has LCR arm capacitance of 12nF and inductance of 3mH and parallel arm capacitance of 4nF. Parallel resonant frequency for the circuit is:

1. 3 MHz
2. 0.3 MHz
3. 6 MHz
4. 9 MHz

✅ Correct Answer: 1

The equivalent circuit of a quartz crystal has LCR arm capacitance of 12nF and inductance of 3mH and parallel arm capacitance of 4nF. Parallel resonant frequency for the circuit is:

1. 3 MHz
2. 0.3 MHz
3. 6 MHz
4. 9 MHz

✅ Correct Answer: 1

Any device with negative impedance as its characteristic property can be called:

1. Energy source
2. Energy sink
3. Oscillator
4. None of the mentioned

✅ Correct Answer: 1

In a microwave oscillator, a load of 50+50j is connected across a negative resistance device of impedance -50-50j. Steady state oscillation is not achieved in the oscillator.

1. True
2. False
3.
4.

✅ Correct Answer: 2

If the input impedance of a diode used in the microwave oscillator is 45-j23 Ω, then the load impedance is to achieve stable oscillation is:

1. 45-j23 Ω
2. -45+j23 Ω
3. 50 Ω
4. 23-j45 Ω

✅ Correct Answer: 2

In transistor oscillators, the requirement of a negative resistance device is satisfied using a varactor diode.

1. True
2. False
3.
4.

✅ Correct Answer: 2

In transistor oscillators, FET and BJT are used. Instability is achieved by:

1. Giving a negative feedback
2. Giving a positive feedback
3. Using a tank circuit
4. None of the mentioned

✅ Correct Answer: 2

In a transistor amplifier, if the input impedance is -84-j1.9 Ω, then the terminating impedance required to create enough instability is:

1. -84-j1.9 Ω
2. 28+j1.9 Ω
3. – (28+j1.9) Ω
4. None of the mentioned

✅ Correct Answer: 2

The stability of an oscillator is enhanced with the use of:

1. high Q tuning network
2. passive elements
3. appropriate feedback methods
4. none of the mentioned

✅ Correct Answer: 1

In oscillator tuning circuits, dielectric resonators are preferred over waveguide resonators because:

1. they have high Q factor
2. compact size
3. they are easily integrated with microwave integrated circuits
4. all of the mentioned

✅ Correct Answer: 4

A dielectric resonator is modeled as __________ when it is used as a tuning circuit with a oscillator.

1. series RLC circuit
2. parallel RLC circuit
3. LC circuit
4. tank circuit

✅ Correct Answer: 2

The coupling factor between the resonator and the microstrip line is the ratio of external Q to the unloaded Q.

1. true
2. false
3.
4.

✅ Correct Answer: 2

If the reflection coefficient seen on the terminated microstrip line looking towards the resonator is 0.5, then the coupling coefficient is:

1. 0.5
2. 0.25
3. 0.234
4. 1

✅ Correct Answer: 4

A dielectric resonator can be incorporated into a circuit to provide _________ using either parallel or series arrangement.

1. frequency stability
2. oscillations
3. high gain
4. optimized reflection coefficient

✅ Correct Answer: 1

It is desired to design a frequency oscillator at 2.4 GHz and the reflection coefficient desired is 0.6, then the coupling coefficient between the feed line and the dielectric resonator is:

1. 1.5
2. 1
3. 0.5
4. none of the mentioned

✅ Correct Answer: 1

If the reflection coefficient between the feed line and the resonator is -0.6, then the equivalent impedance of the resonator at resonance given that the characteristic impedance of the microstrip line is:

1. 50 Ω
2. 12.5 Ω
3. 25 Ω
4. none of the mentioned

✅ Correct Answer: 2

If the equivalent impedance of the resonator at resonance is 12.5 Ω and the characteristic impedance of the feed line is 50 Ω, then the coupling coefficient is:

1. 0.25
2. 0.5
3. 0.75
4. 1

✅ Correct Answer: 1

A practical oscillator has a frequency spectrum consisting of a single delta function at its operating frequency.

1. True
2. False
3.
4.

✅ Correct Answer: 2

___________ due to random fluctuations caused by thermal and other noise sources appear as broad continuous distribution localized about the output signal.

1. Phase noise
2. White noise
3. Thermal noise
4. Shot noise

✅ Correct Answer: 1

Noise power versus frequency for an amplifier has spikes at the operating frequency without the application of an input voltage.

1. True
2. False
3.
4.

✅ Correct Answer: 2

An idealized power spectral density of amplifier has a straight line parallel to X axis and the noise is constant at all frequencies.

1. True
2. False
3.
4.

✅ Correct Answer: 2

At higher frequencies of operation of an oscillator, induced noise is mostly:

1. Thermal noise
2. White noise
3. Shot noise
4. Flicker noise

✅ Correct Answer: 1

A GSM cellular telephone standard requires a minimum of 9 dB rejection of interfering signal levels of -23 dBm at 3 MHz from the carrier, -33 dBm at 1.6 MHz from the carrier, and -43 dBm at 0.6 MHz from the carrier, for a carrier level of -99 dBm. Determine the required local oscillator phase noise at 3 MHz carrier frequency offset.

1. -138 dBc/Hz
2. -128 dBc/Hz
3. -118 dBc/Hz
4. None of the mentioned

✅ Correct Answer: 1

The most affected parameter of a receiver by the phase noise is signal to noise ratio.

1. True
2. False
3.
4.

✅ Correct Answer: 2

Oscillators operating at millimeter wavelength are difficult to realize and are also less efficient.

1. true
2. false
3.
4.

✅ Correct Answer: 1

__________ is an example for a frequency multiplier.

1. resistor
2. inductor
3. capacitor
4. transistor

✅ Correct Answer: 4

The major drawback of frequency multipliers is that they have:

1. higher attenuation
2. complex construction methods
3. complex design
4. none of the mentioned

✅ Correct Answer: 3

A reactive diode multiplier uses _______ as the key electronic component for frequency multiplication.

1. zener diode
2. light emitting diode
3. varactor diode
4. Gunn diode

✅ Correct Answer: 3

A major disadvantage of frequency multipliers is that they multiply the noise factor along with frequency.

1. true
2. false
3.
4.

✅ Correct Answer: 1

If a frequency multiplier has a multiplication factor of 10, then the increase in noise level due to frequency multiplication is:

1. 10 dB
2. 20 dB
3. 25 db
4. 15 dB

✅ Correct Answer: 2

Resistive multipliers are more efficient as compared to reactive multipliers.

1. true
2. false
3.
4.

✅ Correct Answer: 2

Reactive multipliers have a disadvantage that they cannot be used at very high frequencies and they become less efficient.

1. true
2. false
3.
4.

✅ Correct Answer: 1

For a resistive frequency multiplier of multiplication factor 2, the maximum theoretical conversion efficiency is:

1. 50 %
2. 25 %
3. 75 %
4. 12.5 %

✅ Correct Answer: 2

The material used to fabricate IMPATT diodes is GaAs since they have the highest efficiency in all aspects.

1. true
2. false
3.
4.

✅ Correct Answer: 2

IMPATT diodes employ impact ionization technique which is a noisy mechanism of generating charge carriers.

1. true
2. false
3.
4.

✅ Correct Answer: 1

An essential requirement for the BARITT diode is that the intermediate drift region be completely filled to cause the punch through to occur.

1. true
2. false
3.
4.

✅ Correct Answer: 2

with the increase in the operating frequency of a BJT, the S22 parameter of the transistor:

1. increases
2. decreases
3. remains constant
4. none of the mentioned

✅ Correct Answer: 2

with the increase in the operating frequency of a BJT, the S22 parameter of the transistor:

1. increases
2. decreases
3. remains constant
4. none of the mentioned

✅ Correct Answer: 2

The power gain G of a two port network is independent of the source impedance of the two port network.

1. True
2. False
3.
4.

✅ Correct Answer: 1

__________ is defined as the ratio of power available from the two port network to the power available from the source.

1. Transducer power gain
2. Available power gain
3. Power gain
4. None of the mentioned

✅ Correct Answer: 2

In a two port network, the source impedance was measured to be 25 Ω and the characteristic impedance of the transmission line was measured to be 50 Ω. Then the reflection coefficient at the source end is:

1. -0.33333
2. -0.1111
3. 0.678
4. 0.2345

✅ Correct Answer: 1

Gain of an amplifier is independent of the operating frequency.

1. True
2. False
3.
4.

✅ Correct Answer: 2

If the load impedance of a two port network is 40 Ω and the characteristic impedance is 50 Ω, then the reflection coefficient of the two port network at the load end is:

1. -0.111
2. -0.333
3. -0.987
4. None of the mentioned

✅ Correct Answer: 1

For a transistor amplifier to be stable, either the input or the output impedance must have a real negative part.

1. True
2. False
3.
4.

✅ Correct Answer: 1

____________ condition, if met then the transistor can be impedance matched for any load.

1. Conditional stability
2. Unconditional stability
3. Infinite gain
4. Infinite input impedance

✅ Correct Answer: 2

A network is said to be conditionally stable if:

1. Гin│<1, │Гout│<1.
2. Гin│>1, │Гout│>1
3. Гin│>1, │Гout│<1
4. Гin│<1, │Гout│>1

✅ Correct Answer: 1

Stability condition of an amplifier is frequency independent and hence can be operated at any frequency.

1. True
2. False
3.
4.

✅ Correct Answer: 1

For any passive source termination ГS, Unconditional stability implies that:

1. │Гout│<1
2. │Гout│>1
3. │Гin│<1
4. │Гin│>1

✅ Correct Answer: 1

The condition for unconditional stability of a transistor as per the K-∆ test is │∆│> 1 and K<1.

1. True
2. False
3.
4.

✅ Correct Answer: 2

By performing the K-∆ test for a given transistor the values of K and ∆ were found to be equal to 0.383 and 0.334 respectively. The transistor with these parameters has unconditional stability.

1. True
2. False
3.
4.

✅ Correct Answer: 2

The overall gain of a transistor is always a fixed value and cannot be changed as per design requirements.

1. True
2. False
3.
4.

✅ Correct Answer: 2

The frequency response of an amplifier is _______

1. Wide band
2. Narrow band
3. Pass band
4. None of the mentioned

✅ Correct Answer: 2

Unconditionally stable devices can always be ____________ for maximum gain.

1. Lossless matched
2. Conjugate matched
3. Forward biased
4. Driven with high current

✅ Correct Answer: 2

The maximum transducer gain occurs when the source and the load are matched to the impedance Z of the transistor by lossless method.

1. True
2. False
3.
4.

✅ Correct Answer: 2

Maximum transducer gain for an amplifier is the same as the maximum gain for an amplifier.

1. True
2. False
3.
4.

✅ Correct Answer: 1

High gain is not achievable at microwave frequencies using BJT amplifiers because:

1. device construction
2. complex architecture
3. ports are not matched at high frequencies
4. none of the mentioned

✅ Correct Answer: 3

To flatten the gain response of a transistor:

1. biasing current has to be increased
2. input signal level has to increased
3. increase the operational bandwidth
4. give negative feedback to the amplifier

✅ Correct Answer: 4

In conventional amplifiers, a flat gain response is achieved at the cost of reduced gain. But this drawback can be overcome by using:

1. balanced amplifiers
2. distributed amplifiers
3. differential amplifiers
4. none of the mentioned

✅ Correct Answer: 1

Bandwidth of balanced amplifier can be an octave or more, but is limited by the bandwidth of the coupler.

1. true
2. false
3.
4.

✅ Correct Answer: 1

Coupler that is mostly used in balanced amplifiers to achieve the required performance is:

1. branch line coupler
2. wilkinson coupler
3. lange coupler
4. waveguide coupler

✅ Correct Answer: 3

Distributed amplifiers offer very high _________

1. gain
2. bandwidth
3. attenuation
4. none of the mentioned

✅ Correct Answer: 2

In distributed amplifiers, all the FET stages in the amplifier are connected in series to one another.

1. true
2. false
3.
4.

✅ Correct Answer: 2

____________ uses balanced input and output, meaning that there are 2 signal lines, with opposite polarity at each port.

1. differential amplifier
2. distributed amplifier
3. balanced amplifier
4. none of the mentioned

✅ Correct Answer: 1

A major advantage of differential amplifiers is:

1. high gain
2. low input impedance
3. higher output voltage swing
4. none of the mentioned

✅ Correct Answer: 3

_______________ are used in the final stages of radar and radio transmitters to increase the radiated power level.

1. Power amplifiers
2. Oscillators
3. Transistors
4. Attenuators

✅ Correct Answer: 1

Important factors to be considered for power amplifier design are:

1. Efficiency
2. Gain
3. Thermal effect
4. All of the mentioned

✅ Correct Answer: 4

Amplifier efficiency is the ratio of RF output power to DC input power. This parameter determines the performance of an amplifier.

1. True
2. False
3.
4.

✅ Correct Answer: 1

Gain of power amplifiers __________ with increase in operating frequency.

1. Increases
2. Decreases
3. Increases exponentially
4. Decreases exponentially

✅ Correct Answer: 2

__________ amplifiers are linear circuits, where the transistor is biased to conduct over the entire range of the input signal cycle.

1. Class A amplifiers
2. Class B amplifiers
3. Class C amplifiers
4. None of the mentioned

✅ Correct Answer: 1

A class B amplifier consists of _______ transistors in order to conduct the input signal over the entire cycle.

1. 1
2. 2
3. 4
4. 6

✅ Correct Answer: 2

Power amplifiers in the increasing order of efficiency is:

1. Class A, B, C
2. Class C, A, B
3. Class B, A, C
4. Efficiency of all the 3 amplifiers is the same

✅ Correct Answer: 1

Behavior of a transistor in power amplifiers is unpredictable at all input signal levels.

1. True
2. False
3.
4.

✅ Correct Answer: 2

If the output power of an amplifier is 10 V, and the input power supplied to the amplifier is 0.229 V given that the DC voltage used is 38.5 V, efficiency of the power amplifier is:

1. 25%
2. 50%
3. 75%
4. 35%

✅ Correct Answer: 1

If a power amplifier has an output power of 10 W, and an amplifier gain of 16.4 dB, then the input drive power is:

1. 400 mW
2. 225 mW
3. 229 mW
4. 240 mW

✅ Correct Answer: 3

If an antenna has a directivity of 16 and radiation efficiency of 0.9, then the gain of the antenna is:

1. 16.2
2. 14.8
3. 12.5
4. 19.3

✅ Correct Answer: 1

Gain of an antenna is always greater than the directivity of the antenna.

1. True
2. False
3.
4.

✅ Correct Answer: 2

A rectangular horn antenna has an aperture area of 3λ × 2λ. Then the maximum directivity that can be achieved by this rectangular horn antenna is:

1. 24 dB
2. 4 dB
3. 19 dB
4. Insufficient data

✅ Correct Answer: 3

A rectangular horn antenna has an aperture area of 3λ × 2λ. If the aperture efficiency of an antenna is 90%, then the directivity of the antenna is:

1. 19 dB
2. 17.1 dB
3. 13 dB
4. 21.1 dB

✅ Correct Answer: 2

With an increase in operating frequency, the background noise temperature:

1. Increases
2. Decreases
3. Remains constant
4. Remains unaffected

✅ Correct Answer: 1