Interview Questions.

Q1. Types Of Analog Modulation Are?

Modulation is a technique through which a few characteristics of signal together with amplitude or section or frequency are numerous in accordance with the immediate fee of the statistics sign . 

The signal whose traits are various is referred to as service signal, as it includes the statistics. The sign that consists of the facts is referred to as modulating sign as in keeping with it, the characteristics of carrier sign are various.

Methods of analog modulations are:

Amplitude modulation

Frequency modulation

Phase modulation

Q2. In An Amplitude Modulation?

In an Amplitude Modulation, the amplitude of the carrier varies in keeping with the on the spot values of the baseband signal. The frequency and the segment of the provider remain regular. 

The envelope of the AM wave has the same form because the message of the bottom band sign.

Q3. Selectivity Of A Receiver?

The capability of the receiver to choose the desired alerts a number of the diverse incoming indicators is named as Selectivity. It rejects the other alerts at closely lying frequencies. Selectivity is determines performance of a radio receiver that how a good deal it responds only to the radio signal that is required to get hold of. Selectivity of a receiver adjustments with incoming signal frequency and is poorer at high frequencies.

Q4. Cross Talk Is ?

Cross talk is the disturbance prompted in the close by channel or circuit because of trmitted sign. Cross talk is normally caused by undesired coupling of capacitors or inductors from one channel to every other. Electromagnetic interference (EMI) reasons go communicate inside the circuits or the channels. In crosstalk, the signals visiting closer to each other intrude with every other and cause disturbance inside the signal.

Q5. Advantages Of Using An Rf Amplifier Are?

The RF amplifiers have greater advantage that is they've better sensitivity. They have higher capability to expand vulnerable alerts received by way of the receiver. The RF amplifiers have higher selectivity i.E., better capability to select the wanted signals a number of the diverse incoming indicators. The incoming weak indicators are raised to a better stage by means of the RF amplifiers and consequently they enhance sign to noise ratio.

Q6. Advantages Of Analog Communication Over Digital Communication Are?

Due to analog to virtual conversion, the statistics fee becomes high in virtual communication. So the trmission bandwidth is also improved. Digital trmission also desires synchronization in positive applications which isn't wanted in case of analog conversation systems.

Q7. In Automatic Gain Control Of The Am Receiver?

The automated benefit control (AGC) circuit is used to alter the benefit of the receiver depending upon the electricity of the obtained signal on the receiver. The AGC offers a DC voltage as an output this is proportional to the amplitude of the obtained signal. In AGC, the output is a linear feature of the input.

Q8. Calculate The Power In One Of The Side Band In Ssbsc Modulation When The Carrier Power Is 124w And There Is 80% Modulation Depth In The Amplitude Modulated Signal?

Modulation Index = zero.8

Pc = 124W

Power in sidebands may be calculated as = m2 Pc/4

= (zero.8)2 * 124/four

= 79.36 W

Q9. Why Frequency Modulation Is Better Than Amplitude Modulation?

Modulation is higher because it provide more resistance to noise as compared to demodulation.

Q10. Synchronous Detection Me?

Synchronous detection me demodulation of obtained sign and extracting records from it. It requires a reference signal at the receivers with predetermined frequency and segment that is generated the usage of extra circuitry. Synchronous detection enables in extracting weak alerts from noise.

Q11. In Synchronous Detection Of Am Signal?

In synchronous detection of AM signal, the service signal is regionally generated and then handed through a low pass filter. At the output of the low pass filter, the authentic modulating sign is recovered. The synchronous detection requires the generation of provider on the receiver also. So extra circuitry is required on the receiver.

Q12. Bandwidth (b) Of An Am Signal Is Given By?

Bandwidth of the AM wave is the difference within the two intense frequencies of the AM signal. It is given via

B = (ωc + ωm)- (ωc - ωm)

= ωm

i.E., the bandwidth of the AM wave is two times the best frequency gift within the modulating sign.

Q13. The Process Of Recovering Information Signal From Received Carrier Is Known As?

Detection or demodulation of the acquired sign is the healing of data or the authentic message that become trmitted by way of the trmitter after modulation. The method is likewise referred to as demodulation it recovers the authentic sign from the modulated signal obtained.

Q14. What Is Analog Modulation And State Various Techniques?

In it, the modulating approach is applied to the analog records sign. Its various techniques are:

Amplitude modulation(AM)

Frequency modulation(FM)

Phase modulation(PM)

Q15. Intermediate Frequency (if) Should Be Carefully Chosen As?

Intermediate frequency (IF) must be cautiously chosen as

High IF effects in bad selectivity and therefore bad rejection of adjacent channels.

High IF results in problems in tracking of alerts inside the receivers.

Image frequency rejection will become bad at low IF or if very excessive.

Q16. Generation Of Ssb Sc Signal Is Done By?

SSB-SC indicators are the alerts where only one of the sidebands is trmitted in an AM wave. The provider is likewise suppressed at the same time as trmitting the AM signal. SSBSC signal can be generated via two methods:

Frequency discrimination technique or filter out method

Phase discrimination technique or phase shift technique

Q17. What Is The Effect On The Trmitted Power Of Am Signal When The Modulation Index Changes From 0.8 To 1?

The overall electricity in an AM is given by means of 

Pt = Pc (1 + m2/2) 

Where Pc is the service strength and m is the modulation index.

Therefore,

Pt1 = Pc (1 + 0.Eighty two/2) = 1.32 Pc

Pt2 = Pc ( 1 + 12/2) = 1.5 Pc

Increase in strength = (1.Five Pc - 1.32 Pc)/ 1.32 Pc

= 0.1364

Q18. The Functions Of Radio Receiver Are?

The radio receivers receive the incoming modulated service via the receiving antennas. Then they select the desired sign from the service and reject the undesirable indicators and noise. The acquired signal is then amplified by way of the RF amplifiers. Detection of the information signal is achieved from the obtained carrier and the records or the modulating signal is then filtered and amplified.

Q19. Requirements Of Synchronous Detection Of Am Signal Are?

Synchronous detection of AM sign calls for local technology of the service sign at the receiver. The frequency of the domestically generated service must be identical to that of trmitted service. And the section of the locally generated provider must be synchronized to that of trmitted carrier in any other case the detected signal might get distorted.

Q20. State The Techniques Of Demodulation?

There are several approaches of demodulation relying on how parameters of the service sign, along with amplitude, frequency or segment.

For a sign modulated with a linear modulation, like AM, we can use a synchronous detector.

For a signal modulated with an angular modulation, we ought to use an FM demodulator or a PM demodulator.

Q21. Examples Of Low Level Modulation Are?

In a Low level Amplitude Modulation gadget, modulation is done at decrease strength of provider and modulating sign. Therefore the output electricity of modulation is low. So power amplifiers are required to boost the signal up to the favored power degree. Examples of low level modulation are

Square regulation diode modulation

Switching modulation

Q22. The Standard Value For Intermediate Frequency (if) In Am Receivers Is?

Intermediate frequency (IF) is a frequency at which the obtained service frequency is shifted for detection of message sign. The IF is generated with the aid of blending the obtained service with the regionally generated signal. The IF is generated and is shifted to in addition amplifiers and detectors for amplification and detection of message signal respectively. In splendid heterodyne AM receivers, an intermediate frequency of 455 KHz is used.

Q23. Analog Signal May Be Converted Into Digital Signal By?

Conversion of analog sign into virtual sign converts a continuous time signal in the shape of digits. The conversion is finished with the help of sampling method. A pattern is a set of values at a factor in time space. The average quantity of samples acquired in a single 2nd is known as sampling frequency.

Q24. Quadrature Amplitude Modulation (qam) Is?

The modulation scheme Quadrature Amplitude Modulation (QAM) enables equal bandwidth used for trmission of two DSB-SC signals. It is likewise referred to as Bandwidth Conservation scheme. However it needs synchronous detection so it needs a further device for era of provider. Also called Quadrature Carrier Multiplexing, the scheme is utilized in color tv.

Q25. Which Type Of Modulation Is Used In Tv Trmission?

Vegestial facet band modulation (VSBM).

Q26. In Low Level Amplitude Modulation?

In a Low level Amplitude Modulation system, modulation is done at lower strength of provider and modulating signal. Therefore the output power of modulation is low. So electricity amplifiers are required to boost the sign as much as the favored electricity stage.

Q27. What Is The Carrier Frequency In An Am Wave When Its Highest Frequency Component Is 850hz And The Bandwidth Of The Signal Is 50hz?

Upper frequency = 850Hz

Bandwidth = 50Hz

Therefore lower Frequency = 850 - 50= 800 Hz

Carrier Frequency = (850-800)/2

= 825 Hz

Q28. What Is The Maximum Trmission Efficiency Of An Am Signal?

The trmission performance (η) of AM wave is described as the percentage of overall power contributed by means of facet bands of the AM signal. The maximum trmission performance of an AM sign is 33.33%, i.E., simplest one 1/3 of the entire trmitted electricity is carried with the aid of the aspect bands in an AM wave. The ultimate  0.33 of the whole trmitted power gets wasted.

Q29. The Advantages Of Using An Rf Amplifier Are?

The RF amplifiers are utilized in exquisite heterodyne receivers. The benefits of the usage of RF receivers are 

They have higher sensitivity i.E. They have got stepped forward benefit to the sign

They have better signal to noise ration than other amplifiers

The selectivity is better as they've higher rejection to the adjoining undesired indicators.

Q30. The Costas Receiver Is Used For ?

Costas receiver is a synchronous receiver system used for demodulating DSB-SC waves. The incoming modulated carrier is implemented at two inputs of the coherent detectors of the receiver. The domestically generated service applied to the 2 inputs is but in segment quadrature with every other. The frequencies of the nearby carriers are adjusted as equal as the carrier frequency of the acquired signal.

Q31. Squelch Circuit Is?

Squelch circuit suppresses the output audio while there may be insufficient desired enter signal on the receiver. The circuit is used to suppress the unwanted channel noise when there may be no reception through the receiver. Squelch circuits may be used in wireless microphones stay far from replicating the noise whilst sufficient sign isn't always obtained. Regulating squelch is provided in some structures for the receiver.

Q32. Frequency Components Of An Am Wave (m = Modulation Index) Are?

Frequency additives of an AM wave having m modulation index are 

service frequency (ωc ) with amplitude A

upper facet band (ωc + ωm) having amplitude mA/2

lower side band (ωc - ωm) having amplitude mA/2

Q33. Explain The Need Of Modulation And Demodulation ?

Modulation is required to ship the facts over lengthy distances as low frequency signals are not capable of cover massive place.

While demodulation is required to get back the data sent at the receiving aspect.

Q34. In Terms Of Signal Frequency (fs) And Intermediate Frequency (fi), The Image Frequency Is Given By?

The picture frequency is defined as the sign frequency added to twice the value of intermediate frequency. It is the undesirable frequency generated at the receiver which also receives amplified with the message signal. The photograph frequency reasons interference and consequently  or more stations or assets can be obtained concurrently on the receiver output.

Q35. Pilot Carrier Is?

Pilot service is a small service trmitted with modulated sign from the trmitter. It is separated on the receiver and used to segment lock the regionally generated carrier sign generated at the receiver. It presents synchronization on the receiver. 

As a vulnerable carrier is trmitted with the DSB sign, it is also called in part suppressed service device, because the provider isn't totally suppressed. So it's far a case of over modulation.

Q36. What Is Digital Modulation And State Various Techniques?

We can bear in mind it as conversion of analog to virtual sign. Its various techniques are:

PSK- Phase shift keying

ASK- Amplitude shift keying

FSK- Frequency shift keying

QAM- Quadrature amplitude modulation

Q37. Limitations Of Frequency Discrimination Method Are?

Limitations of Frequency discrimination technique are that because the base band sign ought to be appropriately associated with the service signal frequency, the designing of band skip clear out is hard if the service frequency is quite higher than the bandwidth of the baseband sign. The device isn't always beneficial for video communique purpose.

Q38. Disadvantages Of Using Synchronous Detection Of Am Signal Are?

Disadvantages of the usage of synchronous detection of AM signal are that it wishes an extra system for technology of service. The frequency of the locally generated provider have to be identical to that of trmitted provider. And the phase of the regionally generated provider should be synchronized to that of trmitted carrier in any other case the detected signal would get distorted so it wishes an additional device for synchronization of carrier. This makes the receiver complex and costlier.

Q39. In High Level Amplitude Modulation?

In High degree Amplitude Modulation device, Modulation is completed at high power of provider and modulating indicators so Power amplifiers are used to boost the carrier and modulating signals before modulation. Collector modulation method is the instance of High stage Amplitude Modulation.

Q40. What Is Modulation And Demodulation ?

Modulation is the procedure of altering the characteristics of the amplitude, frequency, or section attitude of the high-frequency sign in accordance with the immediately fee of the modulating wave.

Demodulation is the procedure of extracting the unique information sign from a modulated service sign.

Q41. Radio Waves Travel Through?

Radio verbal exchange or wireless communique takes region through electromagnetic waves.

The message is trmitted through open area thru electromagnetic waves or radio waves. The waves are trmitted inside the open space thru antenna after processing of signal.

Q42. Vestigial Side Band Signals Are Detected By?

Vestigial side band signals are detected through Synchronous detection or coherent detection technique. The distortions in a VSB signal can be decreased through reducing the modulation index and growing the width of VSB.

Q43. The Factors That Determine The Sensitivity Of Super Heterodyne Receiver Are?

Sensitivity of a receiver is described as the potential of the receiver to increase susceptible indicators received via the receiver. It is the voltage that have to be carried out at the enter terminals of the receiver to reap a minimum preferred output on the output of the receiver. The elements that determine the sensitivity of extraordinary heterodyne receiver are?

Gain of the IF amplifier

Noise determine of the receiver

Gain of RF amplifier

Q44. Analog Communication Indicates?

Analog conversation me that the records is trmitted in the form of a continuous signal, including a legitimate wave. The sign has varying amplitude or section or frequency. 

Coding isn't always applied to the signal as in case of virtual facts. Amplitude modulated signal and frequency modulated signals are the examples of analog communication.

Q45. Phase Shift Method Is?

Phase shift approach is one of the techniques used for the technology of SSB-SC indicators. This method consists of two balanced modulators and  phase moving networks and avoids the use of filters. Both the balanced modulators produce facet band as an output. 

The SSB-SC signals are generated the usage of multiple tone modulating signals as if executed with unmarried tone modulating sign, they do no longer bring any beneficial records.

Q46. If Modulation Index Is Greater Than 1?

Modulation index is the degree of extent to which the parameter of the provider is varied according with the modulating sign. If modulation index is extra than 1, or the modulation percent is more than 100%, it's miles called over modulation. 

The baseband signal isn't always preserved within the envelope of the AM sign and therefore, the recovered sign is distorted at the output of the receiver.

Q47. What Is The Difference Between Detector And Demodulator?

A detector is a tool that recovers information of interest contained in a modulated wave.

Demodulation is up to date form of detector which extracts the unique statistics from a modulated service wave.

Q48. Function Of Frequency Mixer In Super Heterodyne Receiver Is?

The function of a frequency mixer in a tremendous heterodyne receiver is that it mixes or multiplies the incoming modulated service with the locally generated provider. It then produces some of frequencies. The produced frequencies are both the sum or the differences of the frequencies of the obtained alerts. The output of the mixer is used to hit upon the modulating or statistics sign from the acquired modulated carrier.

Q49. Automatic Gain Control Is?

Automatic gain manipulate gives controlled signal amplitude at the output even supposing there are amplitude variations at the input. This controlled output adjusts the input to output gain to a appropriate fee in order that the device may fit well even for extensive variety of variations at the input. 

The AGC is utilized in AM radio receivers for controlling the weak and strong sound alerts.

Q50. What Is Depth Of Modulation?

It refers to the ratio of the unmodulated carrier amplitude to the amplitude deviation for which the modulated provider wave reaches its minimum cost.