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Learn about the fundamental principles of communication systems, including signal processing, receiving and processing of information by electronic means.
__is a type of radio receiver used as a component of a radio communication link.
With____, in which the frequency of the carrier signal is varied.
____the corresponding wavelength is 10,000 km.
The __ varies according to the changes in the environmental conditions and other situations.
Like all electromagnetic waves, ____in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed.
In Amplitude Demodulation, the condition which the load resistor R must satisfy to discharge capacitor C slowly between the positive peaks of the carrier wave so that the capacitor voltage will not discharge at the maximum rate of change of the modulating wave (W is message bandwidth and ω is carrier frequency, in rad/sec ) is
Calculate the frequencies available in the frequency spectrum when a 2MHz carrier is modulated by two sinusoidal signals of 350Hz and 600Hz.
Advantage of using a high frequency carrier wave is
In the TV receivers, the device used for tuning the receiver to the incoming signal is
The ___ carry the information transmitted by the radio signal.
When the _______________ is modulated onto the radio frequency carrier, the new radio frequency signal moves up and down in frequency.
More sophisticated tuners use a variable capacitor (also called a ______________) to vary the frequency.
For _____________, this can be done with a diode that just rectifies the alternating current signal.
When AM signal is of 25KHz, calculate the number of channels required in Medium Frequency (MF) band of 300KHz-3000KHz.
Calculate the power in a DSB SC signal when the modulation is 60% with a carrier power of 600W.
Types of analog modulation are:
______use analog and Frequency Division Multiplexing.
What is the effect of distortion?
In Amplitude Modulation, the instantaneous values of the carrier amplitude changes in accordance with the amplitude and frequency variations of the modulating signal.
Aliasing refers to
The amount of data transmitted for a given amount of time is called
NTSC means ____.
Convert power gains of 0.01, 0.001, and 0.0005 to decibel values
A power amplifier has a gain of 55 dB. The input power is 600 mW. What is the output power in W?
A __ consists of several elements that work together to generate radio waves that contain useful information such as audio, video, or digital data.
In simple ______________, the tuning is adjusted by varying the number of turns of wire in the coil.
The positive and negative peaks of the carrier wave, are interconnected with an imaginary line. This line helps recreating the exact shape of the modulating signal. This imaginary line on the carrier wave is called as ___.
What is the effect on the transmitted power of AM signal when the modulation index changes from 0.8 to 1?
Amplitude modulation is
Function of RF mixer is
What is the overall gain in dB (AT,dB)?
Radio waves have frequencies as high as ____to as low as 30 hertz.
The modulation technique that uses the minimum channel bandwidth and transmitted power is
An AM signal has a total power of 48 Watts with 45% modulation. Calculate the power in the carrier and the sidebands.
____are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared radiation.
Having a narrower band it is not able to provide the high quality of the _____________, but this is not needed for applications such as mobile radio communication.
These transmissions could offer high fidelity audio, and for this reason, frequency modulation is far more popular than the older transmissions on the long, medium and __.
If a receiver has poor capacity of blocking adjacent channel interference then the receiver has
The function of multiplexing is
This is a particular frequency at which the attenuation reaches a specified value.
As with any form of ______________, it is necessary to be able to successfully demodulate it and recover the original signal.
On its own(tuner), the antenna captures ______________ of all frequencies and sends them to the RF amplifier, which dutifully amplifies them all.
If an AM signal is represented by v = ( 15 + 3 Sin( 2Π * 5 * 103 t) ) * Sin( 2Π * 0.5 * 106 t) volts. (i) Calculate the values of the frequencies of carrier and modulating signals. (ii) Calculate the value of modulation index. (iii) Calculate the value of bandwidth of this signal.
Three amplifiers with gains of 12.5, 4, and 20 are cascaded as shown in the following diagram (from left to right). The input power is 120 mW. What is the overall gain and the output powers of each stage?
______________ FM (NBFM) often uses deviation figures of around ±3 kHz.
What is the condition for greatest output power at the transmitter without distortion?
Disadvantage of using a DSB or SSB signal modulation is
A sensitive amplifier that amplifies the very weak ________________ signal from the antenna so that the signal can be processed by the tuner.
A receiver’s sensitivity is the minimum received signal power for the receiver to successfully recover the transmitted signal. If a receiver’s sensitivity is -45 dBm, and the received power is 10 μW, will the receiver be able to recover the transmitted signal?
Frequency modulation is particularly well known for its use for VHF FM broadcasting.
Whether for __ or mobile radio communication systems, or for use in portable applications, FM is widely used at VHF and above.
Calculate the bandwidth occupied by a DSB signal when the modulating frequency lies in the range from 100 Hz to 10KHz.
Advantage of using VSB transmission is
When this _____________ is exposed to radio waves, the waves induce a very small alternating current in the antenna.
In_____, carries video using two synchronized signal and ground pairs, termed Y and C.
For over modulation, the value of modulation index m is
AM was the earliest modulation method used for transmitting audio in radio broadcasting. It was developed during the first quarter of the 20th century beginning with ___and Reginald Fessenden's.
__is the attenuation of radio energy between the feed points of two antennas that results from the combination of the receiving antenna's capture area plus the obstacle-free, line-of-sight path through free space.
Bandwidth required in SSB-SC signal is (fm is modulating frequency):
______system depends on light as the medium for communication.
The process of transforming a carrier signal so that it can carry the information of a message signal.
The overall power gain (AT)?
Calculate the depth of modulation when a transmitter radiates a signal of 9.8KW after modulation and 8KW without modulation of the signal.
An AM transmitter has an antenna current changing from 5 A un modulated to 5.8 A. What is the percentage of modulation?
Continuous, unmodulated carrier, formerly common for radio direction finding in marine and aeronautical navigation.
The ratio between the modulating signal voltage and the carrier voltage is called?
Frequency modulation is widely used on frequencies below 30 MHz.
TRF receiver and super heterodyne receiver are used for
A circuit that can extract signals of a particular frequency from a mix of signals of different frequencies.
The oscillator usually generates a sine wave, which is referred to as a __.
A 3 GHz carrier is DSB SC modulated by a signal with maximum frequency of 2 MHz. The minimum sampling frequency required for the signal so that the signal is ideally sampled is
A modulation index of 0.5 would be same as
Convert decibel power gains of 13 dB, 33 dB, and 103 dB to power gains.
Analog signal may be converted into digital signal by
The second, called __ or FM, makes slight increases or decreases the frequency of the carrier wave.
One particular advantage of frequency modulation is its resilience to _____________.
What is SNRdB?
It is known as the deviation and is normally quoted as the number of ______________ deviation.
For low level modulation, amplifier used is
This frequency, called the _____________, is determined by the values chosen for the coil and the capacitor.
Calculate the modulation index when the un modulated carrier power is 15KW, and after modulation, carrier power is 17KW.
It is narrow band FM that is typically used for two-way radio _________________.
The tuner usually employs the combination of an ____________ (for example, a coil) and a capacitor to form a circuit that resonates at a particular frequency.
Super heterodyne receivers
It is not possible to change the frequency of a signal to give frequency modulation or FM.
The _____________ may be called a variety of names including FM demodulator, FM detector or an FM discriminator.
Broadcast stations in the VHF portion of the frequency spectrum between _____________ use large values of deviation, typically ±75 kHz.
What is the reference line for the modulating signal?
The total power in an Amplitude Modulated signal if the carrier of an AM transmitter is 800 W and it is modulated 50 percent.
The AM spectrum consists of
Which is not a kind of Analog modulation ?
In the later part of the 19th century, scientists figured out how to electronically generate __ using electric currents.
What is the change in the value of transmitted power when the modulation index changes from 0 to 1?
A power amplifier has an output power of 200 W and an input power of 8W. What is the power gain in decibels?
If the input power is 1 dBm, what is the output power in dBm?
_____affects the propagation of waves and signals in electrical circuits, in optical fibers, and in air. Electrical attenuators and optical attenuators are commonly manufactured components in this field.
Creates alternating current at the frequency on which the transmitter will transmit.
Responsible for separating the audio information from the carrier wave.
A ____filter is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency.
___ filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency.
Many receivers include_____________ to better lock on to the intended frequency — or to produce better-quality audio output — and exclude other signals.
If the value is less than 1, the modulation index is 0.5, then the modulated output would be called as___.
It uses an antenna to capture radio waves, processes those waves to extract only those waves that are vibrating at the desired frequency, extracts the audio signals that were added to those waves, amplifies the audio signals, and finally plays them on a speaker.
It is possible to apply the modulation to a _____________, and it is not necessary to use a linear form of amplification to increase the power level of the signal to its final value.
Optical communication system depends on___ as the medium for communication.
The type of system where the sender has to stop sending the signals to the recipient and then only the recipient can respond
__ carry the information transmitted by the radio signal.
Usually ______________ is allowed for each wide-band FM transmission.
Antenna - RF amplifier - tuner - detector - audio amplifier - _____________
It is often necessary to manage the constraints within the loop carefully but once done it provides and excellent solution.
What happens when the amplitude of the modulating signal is greater than the amplitude of the carrier?
An amplifier has an output power of 5W. What is this amount of power in dBm?
Radio communication system works even without the aid of an antenna.
In half Duplex communication system, both the two parties can’t communicate simultaneously.
What is the percentage of modulation if the modulating signal is of 7.5V and carrier is of 9V?
What is the SNR?
Analog communication indicates:
Convert power gains of 100, 1000 and 2000 to decibel values
When does over-modulation occur?
For _______________, less bandwidth is used.
An AM broadcast station transmits modulating frequencies up to 6 kHz. If the AM station is transmitting on a frequency of 894 kHz, the values for maximum and minimum upper and lower sidebands and the total bandwidth occupied by the AM station are:
What’s left after the diode has its way with the alternating current signal is a direct current signal that can be fed to an ______________.
his component’s job is to amplify the weak signal that comes from the detector so that it can be heard. This can be done using a simple ______________.
Modulation is required for
The ______________ by which the signal moves up and down is important.
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.
In this mode of communication, the information is sent through light.
To generate a __, the frequency of the radio carrier is changed in line with the amplitude of the incoming audio signal.
The amplitude of the carrier signal containing ____varies as per the amplitude of the signal containing information, at each instant.
Synchronous detection means
The ___varies in accordance with the instantaneous amplitude of the modulating signal.
A range of frequencies within a given band, in particular that used for transmitting a signal.
What is the carrier frequency in an AM wave when its highest frequency component is 850Hz and the bandwidth of the signal is 50Hz?
The more powerful the __, the more powerful the broadcast.
This method simply requires the use of a varactor diode placed within the tuned circuit of an oscillator circuit.
Adds useful information to the carrier wave.
Noise figure of merit in SSB modulated signal is
You can adjust the ______________ by varying the amount of inductance in the coil or the capacitance of the capacitor.
_____is the process of transforming a carrier signal so that it can carry the information of a message signal. It superimposes the contents of the message signal over a high-frequency carrier signal, which is then transmitted over communication channels.
Standard intermediate frequency used for AM receiver is
Captures the radio waves.
The first, called __ or AM, makes slight increases or decreases to the intensity of the carrier wave.
What is the line connecting the positive and negative peaks of the carrier waveform called?
Calculate the total modulation Index when a carrier wave is being modulated by two modulating signals with modulation indices 0.8 and 0.3.
FM speech communication , often used for marine radio and many other VHF communications.
Two components are required for radio communication: a transmitter and a __.
This is a method of combining more than one signal over a shared medium.
An unmodulated AM signal produces a current of 5.4 A. If the modulation is 100 percent, calculatesada) the carrier power, (b) the total power, (c) the sideband power when it is transmitted through an antenna having an impedance of 50Ω.
When the __ is modulated onto the radio frequency carrier, the new radio frequency signal moves up and down in frequency.
Baseband transmissions use digital signaling and ____.
Calculate the side band power in an SSBSC signal when there is 50% modulation and the carrier power is 50W.
Emitter modulator amplifier for Amplitude Modulation
A radio receiver is the _____________ of a radio transmitter.
In addition to its widespread use for high quality audio broadcasts, FM is also used for a variety of __ radio communication systems.
Unless you want to listen to every radio channel at the same time, you need a circuit that can pick out just the signals for the channel you want to hear. That’s the role of the ____________.
The ____________ is simply a length of wire.
Radio waves have frequencies as high as _____to as low as 30 hertz.
In_____, the amplitude of the carrier wave is varied in proportion to that of the message signal being transmitted.
What is the circuit used for producing AM called?
The ability of the receiver to select the wanted signals among the various incoming signals is termed as
______which is an international, non-profit organization developing voluntary standards for digital television.
The antenna current of the transmitter is 10A. Find the percentage of modulation when the antenna current increases to 10.4A.
__is the process of converting a digital bit stream into an analog carrier wave for transmission via a communication channel.
Calculate the power saved in an Amplitude Modulated wave when it is transmitted with 45% modulation – Without carrier, – Without carrier and a sideband
Frequency modulation is able to provide near interference free reception, and it was for this reason that it was adopted for the VHF sound broadcasts.
Type of communication system where two equipments can communicate with each other in both the directions simultaneously
Provides the necessary electrical power to operate the transmitter.
While changing the amplitude of a radio signal is the most obvious method to modulate it, it is by no means the only way.
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