Question No. 01: What is modulation?
Answer: Modulation is the
process of varying some characteristic of a periodic wave with an external
signal.
Radio
communication superimposes this information bearing signal onto a carrier signal.
These high
frequency carrier signals can be transmitted over the air easily and are capable
of traveling long distances.
The
characteristics (amplitude, frequency, or phase) of the carrier signal are
varied in accordance with the information bearing signal.
Modulation
is utilized to send an information bearing signal over long distances.
Question No. 02: What is resistor?
Answer: A resistor is a two-terminal
electronic component that opposes an electric current by producing a voltage
drop between its terminals in proportion to the current, that is, in accordance
with Ohm’s law: V = IR.
Question No. 03: What is an
Amplifier?
Answer: Amplifier is an electronic
device or electrical circuit that is used to boost (amplify) the power, voltage
or current of an applied signal.
Question No. 04: What is inductor?
Answer: An inductor is a passive
electrical device employed in electrical circuits for its property of
inductance. An inductor can take many forms.
Question No. 05: What is op-amp?
Answer: An operational
amplifier, often called an op-amp, is a DC-coupled high-gain electronic voltage
amplifier with differential inputs [1] and, usually, a single output. Typically
the output of the op-amp is controlled either by negative feedback, which
largely determines the magnitude of its output voltage gain, or by positive
feedback, which facilitates regenerative gain and oscillation.
Question No. 06: What is
demodulation?
Answer: Demodulation is the act
of removing the modulation from an analog signal to get the original baseband
signal back. Demodulating is necessary because the receiver system receives a
modulated signal with specific characteristics and it needs to turn it to
baseband.
Question No. 07: What is meant by
impedance diagram?
Answer: The equivalent circuit
of all the components of the power system are drawn and they are interconnected
is called impedance diagram.
Question No. 08: What is the need
for base values?
Answer: The components of power
system may operate at different voltage and power levels. It will be convenient
for analysis of power system if the voltage, power, current ratings of the
components of the power system is expressed with reference to a common value called
base value.
Question No. 09: Explain AM and FM?
Answer:
AM-Amplitude modulation is a type of
modulation where the amplitude of the carrier signal is varied in accordance
with the information bearing signal.
FM-Frequency modulation is a type of
modulation where the frequency of the carrier signal is varied in accordance
with the information bearing signal.
Question No. 10: What is Electronic?
Answer: The study and use of
electrical devices that operate by controlling the flow of electrons or other
electrically charged particles is called Electronic.
Question No. 11: What is transistor?
Answer: In electronics, a
transistor is a semiconductor device commonly used to amplify or switch
electronic signals. The transistor is the fundamental building block of computers,
and all other modern electronic devices. Some transistors are packaged individually
but most are found in integrated circuits.
Question No. 12: What are CDMA,
TDMA, and FDMA?
Answer: Code division multiple
access (CDMA) is a channel access method utilized by various radio communication
technologies. CDMA employs spread spectrum technology and a special coding
scheme (where each transmitter is assigned a code) to allow multiple users to
be multiplexed over the same physical channel. By contrast, time division multiple
access (TDMA) divides access by time, while frequency division multiple access
(FDMA) divides it by frequency.
An analogy
to the problem of multiple access is a room (channel) in which people wish to
communicate with each other. To avoid confusion, people could take turns
speaking (time division), speak at different pitches (frequency division), or
speak in different directions (spatial division). In CDMA, they would speak
different languages. People speaking the same language can understand each
other, but not other people.
Question No. 13: What is the need
for load flow study?
Answer: The load flow study of a
power system is essential to decide the best operation existing system and for
planning the future expansion of the system. It is also essential for designing
the power system.
Question No. 14: Advantages of
negative feedback over positive feedback?
Answer: Much attention has been
given by researchers to negative feedback processes, because negative feedback
processes lead systems towards equilibrium states. Positive feedback reinforces
a given tendency of a system and can lead a system away from equilibrium
states, possibly causing quite unexpected results.
Question No. 15: What is
communication?
Answer: Communication means
transferring a signal from the transmitter which passes through a medium then
the output is obtained at the receiver or communication says as transferring of
message from one place to another place called communication.
Question No. 16: What is pass band?
Answer: Pass band is the range
of frequencies or wavelengths that can pass through a filter without being
attenuated.
Question No. 17: Explain RF?
Answer: Radio frequency (RF) is
a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz.
This range corresponds to frequency of alternating current electrical signals
used to produce and detect radio waves. Since most of this range is beyond the vibration
rate that most mechanical systems can respond to, RF usually refers to oscillations
in electrical circuits or electromagnetic radiation.
Question No. 18: What is
Instrumentation Amplifier (IA) and what are all the advantages?
Answer: An instrumentation
amplifier is a differential op-amp circuit providing high input impedances with
ease of gain adjustment by varying a single resistor.
Question No. 19: What is a semi
conductor?
Answer: A semiconductor is a
solid material that has electrical conductivity in between that of a conductor
and that of an insulator (An Insulator is a material that resists the flow of electric
current. It is an object intended to support or separate electrical conductors without
passing current through itself); It can vary over that wide range either permanently
or dynamically.
Question No. 20: What is sampling?
Answer: The process of obtaining
a set of samples from a continuous function of time x(t) is referred to as
sampling.
Question No. 21: Different types of
communications?
Answer: Types of communications are
Analog and digital communication.
Analog communication: As a technology,
analog is the process of taking an audio or video signal (the human voice) and
translating it into electronic pulses. Digital on the other hand is breaking the
signal into a binary format where the audio or video data is represented by a
series of “1”s and “0”s.
Digital communication: Digital signals
are immune to noise, quality of transmission and reception is good, components
used in digital communication can be produced with high precision and power
consumption is also very less when compared with analog signals.
Question No. 22: What is a base
station?
Answer: Base station is a radio
receiver/transmitter that serves as the hub of the local wireless network, and
may also be the gateway between a wired network and the wireless network.
Question No. 23: What are the main
divisions of power system?
Answer: The generating system, transmission
system, and distribution system.
Question No. 24: What is Barkhausen criterion?
Answer: Barkhausen criteria,
without which you will not know which conditions, are to be satisfied for
oscillations.
“Oscillations
will not be sustained if, at the oscillator frequency, the magnitude of the product
of the transfer gain of the amplifier and the magnitude of the feedback factor
of the feedback network (the magnitude of the loop gain) are less than unity”.
The
condition of unity loop gain - Aβ = 1 is called the Barkhausen criterion. This condition
implies that
Aβ = 1 and
that the phase of - Aβ is zero.
Question No. 25: Example for
positive feedback and negative feedback?
Answer: Example for +ve feedback
is Oscillators and for -ve feedback is Amplifiers.
Question No. 26: State ‘Sampling
Theorem’?
Answer: It states that, while
taking the samples of a continuous signal, it has to be taken care that the
sampling rate is equal to or greater than twice the cut off frequency and the minimum
sampling rate is known as the Nyquist rate.
Question No. 27: How many satellites
are required to cover the earth?
Answer: 3 satellites are
required to cover the entire earth, which is placed at 120 degree to each other.
The life span of the satellite is about 15 years.
Question No. 28: Explain different
types of feedback?
Answer: Types of feedback are:
Negative feedback: This tends to reduce
output (but in amplifiers, stabilizes and linearizes operation). Negative
feedback feeds part of a system’s output, inverted, into the system’s input; Generally
with the result those fluctuations are attenuated.
Positive feedback: This tends to
increase output. Positive feedback, sometimes referred to as “cumulative
causation”, is a feedback loop system in which the system responds to
perturbation (A perturbation means a system, is an alteration of function,
induced by external or internal mechanisms) in the same direction as the
perturbation. In contrast, a system that responds to the perturbation in the
opposite direction is called a negative feedback system.
Bipolar feedback: which can either
increase or decrease output.
Question No. 29: Where do we use AM
and FM?
Answer:
AM is used
for video signals for example TV. Ranges from 535 to 1705 kHz
FM is used
for audio signals for example Radio. Ranges from 88 to 108 MHz
Question No. 30: What is stop band?
Answer: A stop-band is a band of
frequencies, between specified limits, in which a circuit, such as a filter or
telephone circuit, does not let signals through, or the attenuation is above the
required stop-band attenuation level.
Question No. 31: What is Oscillator?
Answer: An oscillator is a
circuit that creates a waveform output from a direct current input.
The two main
types of oscillator are harmonic and relaxation. The harmonic oscillators have
smooth curved waveforms, while relaxation oscillators have waveforms with sharp
changes.
Question No. 32: What is conductor?
Answer: A substance, body, or device
that readily conducts heat, electricity, sound, etc. Copper is a good conductor
of electricity.
Question No. 33: What is a repeater?
Answer: A repeater is an
electronic device that receives a signal and retransmits it at a higher level
and/or higher power, or onto the other side of an obstruction, so that the
signal can cover longer distances without degradation.
Question No. 34: What is cut-off
frequency?
Answer: The frequency at which
the response is -3dB with respect to the maximum response.
Question No. 35: What is diode?
Answer: In electronics, a diode
is a two-terminal device. Diodes have two active electrodes between which the
signal of interest may flow, and most are used for their unidirectional current
property.
Question No. 36: Name the modulation
techniques?
Answer:
For Analog
modulation–AM, SSB, FM, PM and SM
Digital
modulation–OOK, FSK, ASK, PSK, QAM, MSK, CPM, PPM, TCM, OFDM
Question No. 37: What is a feedback?
Answer: Feedback is a process
whereby some proportion of the output signal of a system is passed (fed back)
to the input. This is often used to control the dynamic behavior of the
system.
Question No. 38: What is crosstalk?
Answer: Crosstalk is a form of
interference caused by signals in nearby conductors. The most common example is
hearing an unwanted conversation on the telephone. Crosstalk can also occur in
radios, televisions, networking equipment, and even electric guitars.
Question No. 39: What is an
Integrated Circuit?
Answer: An integrated circuit
(IC), also called a microchip, is an electronic circuit etched onto a silicon
chip. Their main advantages are low cost, low power, high performance, and very
small size.