Interview Questions.

Q1. What Is Under Sampling?

Under sampling is also referred to as aliasing effect in which the the sampling frequency is less than the maximum frequency of the signal and therefore the successive cycles of the spectrum overlap.

Q2. What Are The Disadvantages Of Pwm?

PWM, in standard, reuires a greater common power than PAM systems. Also, the PWM system reuires a more bandwidth than PAM.

Q3. What Are The Advantage Of Ppm?

One of the principle benefits of pulse role modulation is that it's miles an Mary modulation techniue that may be implemented noncoherently, such that the receiver does now not need to use a phaselocked loop (PLL) to tune the section of the carrier.

This makes it a appropriate candidate for optical communications systems, where coherent section modulation and detecting are tough and extremely high-priced. The simplest other not unusual Mary noncoherent modulation techniue is Mary freuency shift keying, which is the freuency area twin to PPM.

The other benefits of pulse function modulation are:

The amplitude is held consistent as a consequence much less noise interference.

Signal and noise separation may be very easy.

Due to regular pulse widths and amplitudes, trmission energy for each pulse is same.

Q4. What Si The Need For Modulation?

Consider, as an instance, image sign of a T.V camera. It has freuency spectra of DC to five.5MHz.Any such wide band of freuency can’t be propagated thru ionosphere. However, if this sign is modulated with a carrier in VHF and UHF variety, the percentage bandwidth becomes very small and the signal end up suitable for trmission through surroundings.

Q5. What Is Amplitude Modulation?

Amplitude Modulation is defined as the manner in which the immediately fee of the amplitude of the provider is numerous in step with the amplitude of the modulating or base band signal.

Q6. What Is The Purpose Of Using Differential Pulse Position Modulation?

It is possible to restrict the propagation of errors to adjoining symbols, so that an error in measuring the differential put off of one pulse will have an effect on handiest two symbols, rather than effecting all successive measurements.

Q7. Define Pam And Write Down Its Drawbacks?

Pulse Amplitude Modulation is the system via which the amplitude of the regularly spaced pulses varies in step with the the amplitude of the modulating sign.

The drawbacks are:

Since the amplitude of the pulses varies therefore the peak strength of the modulating s/g is an awful lot more.

The bandwidth required for trmitting is more because the amplitude varies.

Q8. What Is Pulse Position Modulation?

Pulse role modulation (PPM) is the process wherein the position of a wellknown pulse is numerous as a function of the amplitude of the sampled signal.

Q9. What Is Modulation?

Modulation may be described because the manner by way of which a few parameters of a high freuency sign termed as service, is varie according with the signal to be trmitted.

Q10. What Is The Puprpose Of Ppm?

PPM can be used to trmit analog data, consisting of non-stop speech or records.

Q11. Explain The Principle Of Pwm?

Pulsewidth modulation (PWM) of a signal or electricity source involves the modulation of its duty cycle, to either deliver records over a communication channel or control the quantity of energy despatched to a load. PWM makes use of a suare wave whose pulse width is modulated resulting inside the variation of the common cost of the waveform is immediately depending on the obligation cycle D.

Q12. What Are The Applications Of Pulse Position Modulation?

It is commonly beneficial for optical verbal exchange systems, wherein there tends to be little or no multipath interference. Narrowband RF (Radio freuency) channels with low electricity and long wavelength (i.E., low freuency) are affected by and large by way of flat fading, and PPM is better desirable.

Q13. What Are The Different Types Of Analog Modulation?

Amplitude modulation

angle modulation.

Q14. State The Advantages Of Super Heterodyning?

The blessings are:

High selectivity and sensitivity.

No alternate in Bandwidth that is bandwidth remains equal all around the working variety.

High adjoining channel rejection.

Q15. What Are The Objectives Met By Modulation?

Length of antenna is shortened, signal loss is reduced, ease of radiation, adjustment of bandwidth, shifting signal freuency of the assigned fee.

Q16. What Is Pwm Or Pulse Length Modulation Or Pilse Duration Modulation?

In PWM, the heart beat amplitude is kept steady but the main facet, trailing edge or each can be various as a function of the amplitude of the sampled signal and care must be taken to make certain that the heartbeat don’t overlap in a TDM gadget.

Q17. What Do You Mean By Fm And Classify Fm?

Frequency Modulation may be described as the frequency of the carrier (wc) is varied acc. To the modulating sign approximately an unmodulated frequency.

FM are of 2 types:

Narrowband FM

Wideband FM

Q18. What Is Freuency Modulation (fm)?

Freuency modulation is the system of varying the freuency of a carrier wave in proportion to the instantaneous amplitude of the modulating sign with none variation inside the amplitude of the provider wave.

Q19. Explain The Principle Of Ppm?

The amplitude and the width of the heartbeat is saved steady on this device, at the same time as the placement of every pulse, in relation to the position of a recurrent reference pulse is numerous via each immediately sampled value of the modulating wave. This me that the trmitter ought to send synchronizing pulses to operate timing circuits within the receiver. The PPM has the benefit of reuiring consistent trmitter electricity output, but the drawback of depending on trmitterreceiver synchronization.

Q20. What Is Modulation? What Happens In Over Modulation?

Modulation is described as the system wherein a few characteristics of the signal known as service is various in keeping with the modulating or baseband signal. For example – Amplitude Modulation, Phase Modulation, Frequency Modulation.

In case of over modulation, the modulation index is extra than one and envelope distortion takes place.

Q21. What Do You Mean By Nyquist Rate?

In case of Nyquist charge, the sampling frequency is identical to the maximum frequency of the sign and therefore the successive cycles of the spectrum does now not overlap.

Q22. What Are The Application Of Ppm?

PPM is hired in narrowband RF channel structures, with the location of every pulse representing the angular position of an analogue manage at the trmitter, or possible states of binary transfer. The quantity of pulse consistent with body offers the variety of controllable channels available. The advantage of the use of PPM for this sort of utility is that the electronics reuired to decode the signal are extremely easy, which results in small, light-weight receiver/decoder units. (Model aircraft reuire components that are as light-weight as feasible).

Q23. How Can Be Aliasing Be Avoided?

Aliasing can be averted if:

Sampling frequency have to be more than the frequency of the modulating sign.

The frequency should be band constrained to maximum frequency of the signal(fm) Htz.

If prealias filter out is used.

Q24. Mention The Applications Of Pwm?

PWM may be used to reduce the whole amount of energy delivered to a load with out losses generally incurred when a energy source is restrained by using resistive me. This is because the average strength added is proportional to the modulation obligation cycle. With a sufficiently excessive modulation charge, passive electronic filters may be used to clean the pulse educate and get better a median analog waveform.

Q25. What Are The Advantage Of Pam And Pwm?

PWM machine offers a greater signal to noise ratio in comparison to PAM however reuires a larger bandwidth to attain this.

Q26. What Is Multiplexing? Name The Types Of Multiplexing?

Multiplexing is defined because the system wherein a number of message alerts are mixed collectively to form composite indicators in order that they can be trmitted thru the not unusual channel.

The  kinds of multiplexing are:

Frequency Division Multiplexing: In this method, fixed frequency bands are allotted to each user inside the complete channel bandwidth. Such frequency is allocated to person on a continuous basis.

Time Division Multiplexing: When the heart beat is present for the short time duration and most of the time their is no sign gift inbetween them than this loose area among the two pulses can occupied by means of the pulses from other channels. This is known as Time Division Multiplexing.

Q27. What Is The Advantage Of Ppm Over Pwm And Pam?

The section deviation are usually small. The noise produces a smaller stressful impact at the time function of the modulating pulse educate and as a result, PPM waves have a higher overall performance with appreciate to sign to noise ratio in contrast to PAM and PWM structures.

Q28. What Is Sampling? What Is Sampling Theorem?

Sampling is described as the manner in which an analog indicators are converted into digital alerts. It me that a continuous time signal is transformed into a discrete time sign.

Sampling Theorem is described as : ’The continuous time signal that may be represented in its samples and recovered back if the sampling frequency (fs) is greater than the most frequency of the signal (fm) this is fs >2fm’.