Electrical engineering/Microwave Engineering MCQs Set-7 Sample Test,Sample questions

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

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

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

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.

A major advantage of differential amplifiers is:

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

A network is said to be conditionally stable if:

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

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

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

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:

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:

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

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

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

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

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)

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

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

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

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

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

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.

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:

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:

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

Distributed amplifiers offer very high _________

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

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

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

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

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

Gain of an amplifier is independent of the operating frequency.

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

Gain of power amplifiers __________ with increase in operating frequency.

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:

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

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

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:

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

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:

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:

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:

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:

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:

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

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

Important factors to be considered for power amplifier design are:

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.

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

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:

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

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

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

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

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

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:

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

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

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

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:

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

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

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

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

Power amplifiers in the increasing order of efficiency is:

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

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

Quartz crystals are more efficient as a feedback network because:

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

Resistive multipliers are more efficient as compared to reactive multipliers.

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

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

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

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

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:

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:

The frequency of operation of an FET is limited by:

The frequency response of an amplifier is _______

The major drawback of frequency multipliers is that they have:

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

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

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

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

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

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

The transfer function of an RF oscillator is given by:

To flatten the gain response of a transistor:

Unconditionally stable devices can always be ____________ for maximum gain.

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

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

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

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

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

__________ is an example for a frequency multiplier.

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

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

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

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

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