Define PAM, PWM, and PPM. Draw waveforms.

1 Answer

image

Pulse amplitude modulation is defined as a process of varying the amplitude of the carrier pulse in accordance to the modulating signal variations.

Pulse width modulation is defined as a process of varying the width of the carrier pulse in accordance to the modulating signal variations.

Pulse Position modulation is defined as a process of varying the position of the carrier pulse, in accordance to the modulating signal variations.

Like 0 like Dislike 0 dislike

Related questions

Description : Compare PAM, PWM, and PPM on the basis of i. Variable characteristics ii. Bandwidth iii. Information contained in iv. Transmitted power

Answer : Compare PAM, PWM, and PPM on the basis of i. Variable characteristics ii. Bandwidth iii. Information contained in iv. Transmitted power

Description : Draw the diagram for PAM generation using transistors. Explain its working.

Answer : Explanation:-1. Transistor Q1 is used in the active region so it has been provided with DC biasing to its base. 2. Modulating signal is applied to the base of transistor Q1 3. In the emitter of ... . 7. In the time interval between sampling pulses output is zero. Thus we get the output as PAM.

Description : Draw the circuit diagram of PWM using IC555. State its operation.

Answer : Operation: i. The timer IC555 is operated in monostable mode. ii. The negative going carrier pulses are to the differentiator formed by R1 & C1. The differentiator produces sharp negative ... . Thus PWM signal is generated at the output pin (3) of IC555 as monostablemultivibrator. 

Description : Draw the block diagram of PWM. List its advantages 

Answer : Block diagram of PWM:- Advantages of PWM:- 1. More immune to noise. 2. Synchronization between transmitter and receiver is not required. 3. Possible to separate out signal from noise.

Description : Draw the block diagram of FM super heterodyne radio receiver with waveforms.

Answer : block diagram of FM super heterodyne radio receiver

Description : Explain effect of 'm' on AM with neat waveforms.

Answer : i)m< 1  If m < 1 or if the percentage of modulation is less than 100% the this type of modulation is known as under modulation The amplitude of modulating signal less than carrier ... greater amplitude part of its information is lost in the process of modulation which is undesirable.

Description : Define the transmission line? Draw it‟s general equivalent circuit.

Answer : Transmission line: A conductor or conductors designed to carry electricity or an electrical signal over large distances with minimum losses and distortion.  Equivalent circuit:

Description : Define pre-emphasis. State its need. Draw the circuit of pre-emphasis.

Answer : Definition- The artificial boosting of higher modulating frequencies to reduce the effect of noise is called as pre-emphasis. Need:- The artificial boosting of higher audio modulating ... by increasing the amplitude of modulating signal at higher frequencies. Circuit diagram 

Description : Draw practical set-up and explain the procedure to measure selectivity of radio receiver.

Answer : Procedure to measure selectivity of radio receiver: Throughout the measurement the receiver is kept tuned to desired frequency 950 Khz. Now the generator output frequency is deviated below ... the generator output voltage is adjusted to get a standard 50 miliwatt receiver output power.

Description : Draw and label the circuit diagram of ratio detector 

Answer : Draw and label the circuit diagram of ratio detector  

Description : Draw the structure and state applications of: i) Ferrite loop (rod) antenna ii) Horn antenna

Answer : Horn antenna: Application:- i) Used at microwave frequency. ii) Used in satellite tracking.  Ferrite loop antenna: Application:- In Am radio receiver to receive MW and SW band signals. In FM radio receiver

Description : Draw block diagram of FM receiver and explain the use of limiter circuit.

Answer : Diagram Explanation Amplitude limiter: The function of amplitude limiter is to remove all amplitude variation of FM carrier voltage that may occur due to atmospheric disturbances. Use of amplitude limiter makes the system less noisy.

Description : Draw construction of Yagi-Uda antenna and explain.

Answer : Explanation A Yagi-Uda antenna, commonly known as a Yagi antenna, is a directional antenna consisting of multiple parallel elements in a line, usually half-wave dipoles made of ... receiver with a transmission line and additional parasitic elements called reflector and one or more directors.

Description : Draw waveform for standing waves on an open and shorted line. Prove that impedance is inverted at every quarter wavelength interval.

Answer : Waveform- Explanation When the transmission line is short circuited voltage is zero and current is maximum.The variation is according to the wavelength. When the ... The pattern repeats for every half wavelength. Thus impedance is inverted at every quarter wavelength interval.

Description : Draw and explain block diagram of electronic communication system.

Answer : Block diagram of electronic communication system. Explanation Transducer: A transducer is usually required to convert the output of a source into an electrical signal that is suitable for ... etc. Output Transducer: The output transducer converts electrical signal in to sound signal.  

Description : Explain loop antenna with neat sketch. Draw radiation pattern. State its advantages and applications.

Answer : Loop antenna:-The single turn coil carrying RF current through it having length less than the wavelength.   Advantages:- 1. highly directive 2. Small size Applications:- 1. For direction finding 2. In portable receivers 3. In navigation 

Description : Draw and explain PLL as an FM demodulator.

Answer : Explanation:- FM signal which is to be demodulated is applied to input of PLL.VCO output must be identical to input signal if PLL is to remain locked. As PLL is locked, VCO ... error voltage represents the modulating signal. Thus at the error amplifier output we get demodulated FM output.

Description : Draw the circuit diagram of practical diode detector and explain its working. 

Answer : Circuit diagram of practical diode detector:  Explanation- The circuit operates in the following manner- The diode has been reversed so that now the negative envelope is demodulated. Due to this ... to produce AGC voltage. The DC AGC voltage is proportional to the amplitude of AM signal. 

Description : Draw block diagram of basic electronic communication system and state the function of each block.

Answer : i) Input signal: - The information can be in the form of sound, picture or data coming from computer. ii) Input transducer: - it converts original information into equivalent electrical ... back to suitable form. vii) Output transducer: - It converts electrical signal into original form. 

Description : Draw the circuit diagram of limiter and explain its working.

Answer : Circuit diagram of amplitude limiter:- Explanation:- 1. In frequency modulation, the signal amplitude is held constant while the carrier frequency is varied. 2. Any noise that contaminates ... V p-p instead of the alternately driven into saturation and cutoff, it limits the signal amplitude

Description : Draw the TRF receiver block diagram and explain its working. 

Answer : Explanation:- 1. TRF receivers are simple and having high sensitivity. The AM transmission takes place in MW band and SW band. MW frequency range is 540KHz to 1640KHz. 2. ... power level to drive the loudspeaker. 7. The loudspeaker converts electrical signal into original sound information.

Description : Draw the circuit diagram of varactor diode FM modulator and explain its working.

Answer : Varactor diode modulator is the direct method of FM generation wherein the carrier frequency is directly varied by the modulating signal. A varactor diode is a semiconductor diode whose ... the magnitude of frequency change is proportional to the amplitude of the modulating signal voltage.

Description : Draw amplitude modulated waveform in time domain and frequency domain with proper labeling.

Answer : AM in Time domain  AM in frequency domain

Description : Draw the structure of horn antenna and its radiation pattern. List its any two applications.

Answer : The structure of horn antenna Radiation pattern of Horn Antenna Application:- i) Used at microwave frequency. ii) Used in satellite tracking 

Description : Draw circuit diagram of transistor reactance modulator. Explain its working.

Answer : Explanation- A reactance modulator is illustrated in figure. It is basically a standard commonemitter class A amplifier. Resistors R1 and R2 from a voltage divider to bias ... frequency, whereas a lower capacitance increases the frequency. The circuit produces direct frequency modulations.

Description : In a FM system, the maximum deviation is 75KHz. Find bandwidth for modulating frequency i. fm=500Hz ii. fm=5KHz iii. fm=10KHz Draw conclusion for bandwidth of FM from answer.

Answer : Given deviation∆=75kHz i) fm=500Hz bandwidth B.W=2(∆+fm)  =2(75k+500)=151kHz  ii). fm=5KHz bandwidth B.W=2(∆+fm)  =2(75k+5k)=160KHz iii) fm=10KHz bandwidth B.W=2(∆+fm)  =2(75k+10k)=170KHz As the modulating frequency increases bandwidth also increases.

Description : Draw radiation pattern for following antenna i) Yagi-Uda antenna ii) Loop antenna iii) Dish antenna iv) Horn antenna

Answer : Type of antenna Radiation Patteren  Yagi-Uda antenna Loop antenna Dish antenna Horn antenna 

Description : Draw Yagiuda antenna with its radiation pattern.

Answer : Construction of Yagi-Uda Antenna Radiation Pattern of Yagi-Uda Antenna

Description : Draw general equivalent circuit of transmission line.

Answer : Fig. General Equivalent circuit of transmission line 

Description : Draw the radiation pattern for Dipole antenna: (i) Half wave dipole (ii) Folded dipole.

Answer : The radiation pattern for Half wave dipole antenna The radiation pattern for Folded dipole antenna.

Description : Draw the block diagram of AM transmitter, explain its operation.

Answer : AM transmitter is of two types i)High Level AM Transmitter ii)Low Level AM Transmitter i) RF crystal oscillator: It is a source of carrier signal of desired frequency. The circuit is ... AM signal is then applied to the transmitting antenna which radiates this AM signal into air or space. 

Description : Define and explain the term beam width related to antenna with a sketch.

Answer : Definition: The beam width of an antenna is described as the angles created by comparing the half power point (3dB) on the main radiation lobe to its maximum power point. As an example the beam width ... max voltage at center of lobe (these point are known as half power points.) Sketch-  

Description : Define stub. Explain single and double stub in brief with neat sketch.

Answer : Stub:- Stub is the piece of short circuited transmission line which is used to tune out the reactance of the load when connected across the transmission line as close as possible ... but lengths are independently adjustable. The double stub matching provides wide range of impedance matching. 

Description : Define electromagnetic wave and polarization.

Answer : Electromagnetic wave:-An electromagnetic wave such as light consists of a coupled oscillating electric field and magnetic field which are always perpendicular; by convention Polarization:-polarization" of electromagnetic waves refers to the direction of the electric field.

Description : Define the term baluns and explain where is it used?

Answer : A type of electrical transformer used to connect an unbalanced circuit to a balanced oneORA balun is a type of transformer: it's used to convert an unbalanced signal to a balanced ... :- In audio applications, baluns convert between high-impedance unbalanced and low impedance balanced lines.

Description : Define selectivity and sensitivity of AM Receiver. 

Answer : Selectivity:-It needs to accept signals of the wanted frequency and reject other unwanted frequencies. Sensitivity:-The sensitivity of a radio receiver is its ability to amplify weak signals. It is ... the receiver input terminals to give a standard output power, measured at the output terminals. 

Description : Define: (i) Image frequency and (ii) Double spotting

Answer : i)Image frequency:- Image Frequency is defined as the signal frequency plus twice the intermediate frequency. It is denoted as fsi = fs+2fi Where, fs = Signal Frequency fi =intermediate frequency ... It is due to the poor front end selectivity i.e., inadequate image frequency rejection.

Description : Define modulation index in AM and give its formula.

Answer : In AM wave, the modulation index (m) is defined as the ratio of the amplitude of the modulating signal (Vm ) to the amplitude of carrier signal (Vc). m = Vm / Vc

Description : Define rectifier. Draw circuit diagram and input-output waveforms of bridge type full wave rectifier 

Answer : Rectifier - This circuit convert AC signal into DC.

Description : Define the following terms related to antennas; (i) Antenna resistance (ii) Directivity (iii) Antenna gain (iv) Power density

Answer : Antenna Resistance - The resistance of an antenna has two components: 1. Its radiation resistance due to conversion of power into electromagnetic waves 2. The resistance due to actual losses in the ... the transmitter power divided by the surface area of a sphere (4πR2) at that distance.

Description : Define critical frequency w.r. to wave propagation.

Answer : Define critical frequency w.r. to wave propagation.

Description : Define VSWR with refernce to standing waves.

Answer : Voltage Standing Wave Ratio: The voltage standing wave ratio (VSWR) is the ratio of max voltage to min voltage. VSWR= VMAX /VMIN

Description : Define sensitivity with graph.

Answer : Define sensitivity with graph.

Description : Define: 1)Frequency 2)Bandwidth 3)Wavelength 4)Time period

Answer : Frequency: Frequency is the number of cycles per second. Bandwidth: A range of frequencies within a given band, in particular that used for transmitting a signal. Wavelength: Wavelength can be defined as ... for one complete cycle of vibration to pass a given point.  OR Time period=1/frequency

Description : State the types of electromagnetic polarization? Define any one of it.

Answer : Transverse electromagnetic wave:- The polarization of a plane EM wave is simply the orientation of the electric field vector with respect to the surface (i.e. looking at the horizon) If ... the field strength varies with change in polarization the wave is said to have an elliptical polarization 

Description : Define modulation? State the desirable value of modulation index of AM.

Answer : Modulation: It is the process in which any of these Parameters (Amplitude, Frequency, Phase) of high frequency signal (carrier signal) are varied in accordance with low frequency signal(modulating signal) For an AM, modulation index range is 0 to 1.

Description : Define fading? List the causes.

Answer : The fluctuation in signal strength at a receiver, which is mainly due to the interference of two waves which left the same source but arrived at the destination by different paths, is known ... , such as irrigation, or from multiple transmission paths, irregular earth surfaces, and varying terrains.

Description : Define pulse modulation. State its types. 

Answer : Pulse Modulation - consists essentially of sampling analog information signals and then converting those samples into discrete pulses. OR It consists essentially of sampling analog information signals and then converting those ... PAM - PWM - PPM  ii) Digital Pulse Modulation - PCM - DM - ADM 

Description : Define modulation index in FM. What is maximum value of deviation ratio.

Answer : Modulation Index of FM: It is defined as the ratio of Frequency Deviation (δ) to the modulating signal frequency (fm). (OR)  

Description : Define the following terms: (i) Polarization (ii) Antenna gain (iii)Antenna resistance (iv)Directivity

Answer : i) Polarization:- It is defined as the direction of electric field vector in the EM wave radiated by the transmitting antenna. ii) Antenna Gain:- Antenna gain is defined as the ratio of ... in only one direction in which the radiation is maximum. That is directivity = Max. directive gain

← Prev Question Next Question →
Ask a Question
Choose topic