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Bandwidth is the quantity of data that may be transported from one point to another inside a network in each length of time. Typically, bandwidth is stated as a bitrate and is measured in units (bps). The term "bandwidth" is used in several other technological contexts. It is commonly measured in hertz in signal processing and is used to make the distinction between the upper and lower frequencies in transmission such as a radio signal (Hz). Here, we will learn more about the bandwidth of a signal, how it is measured, and discuss some important questions.
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Key terms: Hertz, Frequencies, RADAR, Spectrum, Ultrasound, Skywave, Transmission, Signal, Single bandwidth, Radio signal, Communication system
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Bandwidth of Signal
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A range of frequencies within an uninterrupted arrangement of frequencies is referred to as signal bandwidth. It's calculated in Hertz. A communication system's purpose is to transfer data from a transmitter located in one location to a beneficiary located, for the most part, far away from the transmitter.
When we send an email, we're sending bits of information to the collector. Depending on the model chosen, this data is transmitted over the air or a cable at a certain frequency. Another issue to consider is that the data can be presented in a variety of formats, including voice, video, photograph, word report, and so on. Thankfully, there is a vast spectrum of frequencies available for bidding.
The difference between the upper and lower frequencies of a signal created is known as its bandwidth. The signal's Bandwidth (B) is equal to the difference between the higher or upper-frequency and the lower frequency, as shown in the diagram above.
Bandwidth of the Transmission Medium
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Varied forms of transmission media, including message signals, have different bandwidths. Wire, open space and fiber optic cable are the most prevalent transmission media. With a bandwidth of roughly 750 MHz, Coaxial cable is a widely utilized wire media. Typically, these cables are utilized at frequencies below 18 GHz. Radio waves are used to communicate over a wide range of frequencies in free space, from a few hundreds of kHz to a few GHz.
The frequency range of optical communication utilizing fibers is 1 thz to 1000 thz (microwaves to ultraviolet). Transmission bandwidth of more than 100 GHz is possible using optical fiber.
An international agreement determines spectrum allotment.
The current frequency allocation scheme is managed by the International Telecommunication Union (ITU).
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Measurement of Bandwidth of a Signal
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In a variety of technical domains, bandwidth is a fundamental notion. It explains the difference between upper and lower frequencies in transmission signals such as radio signals, etc. in signal processing. The hertz unit is used to measure the bandwidth of a signal (Hz). The bandwidth may be referred to as passband bandwidth or base bandwidth depending on the context. Over a certain frequency range, a signal processing system performs well. The output of a system is smooth throughout this frequency range. The frequency response steadily decreases outside of this region. The cut-off frequency is the point in a system's frequency response when the energy flowing through it diminishes rather than passes through.
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Application of Signal Bandwidth
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- RADAR is a type of radar that employs very high-frequency noises, often on the order of 1 to 3 MHz, and is utilized in applications such as space, defence, engineering, metal research, and so on.
- In many telecommunications applications, bandwidth is a fundamental term. The frequency range occupied by a modulated carrier signal in radio communications, for example, is known as bandwidth.
- Medical uses of sound signals with a frequency of more than 20000Hz are done in hospitals for ultrasounds to detect the health and condition of internal organs or to determine the growth of a baby during pregnancy.
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Things to Remember
- Every signal is made up of a huge number of wavelengths of various frequencies, and each signal is different in its composition. This takes us to the techniques used in the signal identification procedure.
- A human's auditory range is 20 Hz to 20 kHz, whereas a dog's range is 50 Hz to 46 kHz. The most important property of bandwidth is that it allows every band of a particular width to transmit the same amount of data regardless of where it is in the frequency spectrum.
- A government agency (such as the Federal Communications Commission in the United States) may allocate regionally available bandwidth to broadcast license holders to ensure that their transmissions do not conflict with one another.
- A signal bandwidth of over 100 GHz may be achieved using optical fiber. The government of the country allocates bandwidth to radios, TVs, and cellular communication firms.
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Sample Questions
Ques. What is skywave communication? Why is this mode of propagation restricted to frequencies only up to a few MHz? (2 marks)
Ans: The transmission of skywaves When radio waves flow from one location on the planet to another after being reflected by the ionosphere, the ionosphere reflects a range of frequencies from a few MHz to 30 MHz as a short-wave band, this range is also reflected. Short wave broadcast services utilize this method of propagation. The reason for the limitation up to a few MHz is as follows: Higher frequencies (> 40 MHz) bend somewhat but are not reflected in the ground, but radio waves up to 30 MHz cannot enter the ionosphere and are reflected the earth. Because frequencies as low as a few MHz (around 30 MHz) are reflected on the ground. As a result, skywave communication uses this frequency band.
Ques. Is it required for line-of-sight communication for a sending antenna to be at the same height as the receiving antenna? The height of a television broadcasting antenna is 81 meters. If the receiving antenna is at ground level, how much service area can it cover? (2 marks)
Ans: There is no physical impediment between the transmitter and the receiver in line-of-sight communication. It is not required for the transmitting and receiving antennas to be at the same height in such communications.
Height of the specified antenna, h = 81 m Radius of earth, R = 6.4 × 106 m for range, d = 2Rh, the service area of the antenna is determined by the relation: A = πd2 = π (2Rh) = 3.14 × 2 × 6.4 × 106 × 81 = 3255.55 × 106 m2 = 3255.55 3256 km2.
Ques. The carrier wave in an amplitude modulator circuit is C(t) = 4 sin(20000π t), whereas the modulating signal is m(t) = 2sin(20000π t). The values of modulation index and lower sideband frequency are (3 marks)
(a) 0.4 and 10 kHz
(b) 0.5 and 9 kHz
(c) 0.3 and 9 kHz
(d) 0.5 and 10 kHz
Ans: (b) 0.5 and 9 kHz
Explanation: Given C(t) = 4 sin (20000 πt) ⇒ Ac = 4
m(t) = 2 sin (2000πt) ⇒ Am = 2
Modulation index now, μ = Am/Ac = 2/4 = 0.5
Lower side band frequency, f = fc – fm... (1)
For the carrier wave, the formula is (20000 πt) = 2 πfc.
fc = 10000 Hz
For modulating wave, (2000 πt) = 2πfm
fm = 1000 Hz
From (1), Lower sideband frequency = 10 kHz – 1 kHz = 9 kHz
Ques. A T.v. Tower has a height of 80m. By how much the height of the tower is increased to triple its coverage? (3 marks)
Ans: here, h1=80mh1=80m. Use the formula d1=2h1r−−−−√d1=2h1r to find the value of d1d1.
D1=2h1r−−−−√d1=2h1r
=2×80×r−−−−−−−−−√=2×80×r
=160r−−−−√=160r
If the coverage is tripled, then d1d1 changes to 3d13d1.
Hence, 2h2r−−−−√=3d12h2r=3d1.
Solving further we get,
2h2r−−−−√=3160r−−−−√2h2r=3160r
H2=720m
Ques. For the A.M. wave, define the term modulation index. What would the modulation index of an A.M. be? Write the minimum amplitude as 'b' for a wave with a maximum amplitude of 'a a'. (3 marks)
Ans: The modulation index is the ratio of the amplitude of the carrier wave to the amplitude of the carries (original) wave.
i.e., μ=Em/Ec
Here, Maximum Amplitude a=Ec+Em
Minimum Amplitude b=Ec−Em
⇒Ec=a+b/2 and
⇒Em=a−b/2
⇒μ=a−b/a+b
Ques. Which of the following frequencies will be adequate for employing sky waves to communicate beyond the horizon? (3 marks)
a) 10 kHz
b) 10 MHz
c) 1 GHz
d) 1000 GHz
Ans. (b) 10 MHz
Explanation: To communicate beyond the horizon, the signal waves must travel a vast distance. 10 kHz broadcasts cannot be aired successfully due to antenna size. High-energy signal waves enter the ionosphere (1GHz - 1000GHz). The ionosphere easily reflects 10 MHz frequencies. As a result, such frequencies of signal waves are suitable for communication beyond the horizon.
Ques: Give the setup of a basic communication system? (2 marks)
Ans. A simple communication system consists of an information source, a transmitter, a connection, and a receiver. In a simple communication system, the transmitter is usually located in one location, the receiver is usually situated somewhere else to distinguish them from the transmitter, and the channel is the unique physical medium that connects them.
Ques. The height of a transmitting antenna is 50 meters. If the earth's radius is 6250 kilometers, are you able to find the region that it covers? (3 marks)
Ans: In the question, it is given that the height of the antenna is 50m. It is required to find the area that it covers.
So, we will use the formula,
d=√d=2Rh
where d is the distance of transmission,
R = radius of the Earth = 6250km,
H is the height of the antenna.
Substitute h=50and R=6250×1000 in the formula d=√2Rh and simplify.
Substitute the value of D obtained in the formula of area of a circle, Πd2.
d=√2rh
d=√2×6250×50×103
d=2.5×104 m
Area covered=πd2
=3.14×(2.5×104)2
=1963km2
Ques. Define the following terms (3 marks)
(a) Ground wave propagation
(b) Space wave propagation
(c) Skywave propagation
Ans. a) Ground waves propagation- Ground waves are radio waves that move over the earth's surface and propagate along the earth's surface. It's limited to frequencies below 1.5 MHz
(b) Space wave propagation- Sky waves are radio waves that are reflected in the earth's ionosphere and propagate through skywave propagation.
(c) Space wave propagation— Line of sight communication employs high-frequency waves that cannot be reflected in the ground when sent from a sending antenna to a receiving antenna. The propagation of space waves is another name for it.
Ques. Long-distance radio broadcasts use short wavebands. Why? (3 marks)
Ans: Short waves are waves with a wavelength of fewer than 200m and a frequency of more than 1.5 MHz Because of their high frequency, they are absorbed by the ground. From the ionosphere, these waves are reflected. After reflection from the ionosphere, these waves reach the earth's surface only at a great distance from the point of transmission. It indicates that short waves have less attenuation. Short waves are employed in long-distance broadcasts because of this reason.
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