The Bandwidth of a Signal
What is implied by the signal bandwidth? Signal bandwidth is a scope of frequencies inside a nonstop arrangement of frequencies. It is estimated in Hertz. The reason behind a communication system is to move information from the transmitter, which is situated in one spot to a beneficiary, which is, for the most part, far away from the transmitter.
At the point when we send an email, we are sending it as bits of information to the collector. This information is moved over the air or wire at a specific frequency relying upon the model picked. Another factor at play is that the information can be in numerous structures; voice, video, photograph, word report, and so forth. Fortunately, there is an enormous spectrum of frequencies waiting for bidding.
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The smaller frequencies are utilized for significant distance communications and can travel unaffected over enormous distances. More significant frequencies have more energy and can convey more information; however, they are exceptionally inefficient and can't be transmitted over significant distances. One such arrangement of frequencies is utilized for a different reason than others, i.e., the microwaves. For transmitting sounds or speech, the range of frequencies from 300 Hz to 3100 Hz is adequate, and henceforth the present phones work at a transmission capacity of 2800 Hz. Transmission of music requires a signal bandwidth of 20 kHz due to the different instruments with an assortment of pitches.
The perceptible range of a human is from 20 Hz to 20 kHz while a dog can hear from 50 Hz to 46 kHz. The critical attribute of the bandwidth of a signal is that any band of a given width can convey a similar quantity of information, paying little heed to where the band is situated in the frequency spectrum. For instance, a 4kHz bandwidth of a signal can transmit a phone discussion, whether through lower frequency, similar to a wired phone or modulated to a higher frequency, i.e., mobile phone.
What we examined until now was for analogue signals. Digital signals are in rectangular structure, either on or off, i.e., 1 or 0. The sine wave is the essential waveform, and each other sort of waveform (triangular, rectangular as in digital) can be composed as a mix of the crucial sine wave. We get digital pulses when we superimpose sine waves of various harmonics.
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The Bandwidth of Transmission Modes
There are different modes of transmission, from smoke signals and beating drums to the modern fibre optics. The quantity of data these different methods can transfer vary colossally. During the 1990s and the mid-2000s, India had a dial-up internet, which was genuinely moderate; however, now, with changes in infrastructure, we have quicker internet. Wires are the most ordinarily utilized transmission media. Wire offers a bandwidth of around 750 MHz. The transmission over the air and free space extends from a couple of hundred kHz to a couple of GHz. An optical fibre can offer a bandwidth of a signal of more than 100 GHz. The bandwidths are allotted to radios, TVs, and cellular communication-related companies by the country's government.
Measurement of the Bandwidth of a Signal
Bandwidth is a critical idea in a few technological fields. In signal preparing, it portrays the contrast among upper and lower frequencies in transmission signals like radio signals, and so on. The estimation of the bandwidth of a signal is done in Hertz (Hz). The bandwidth of a signal can be referred to as passband or base bandwidth, depending on the context.
A signal processing system works productively over a limited scope of frequencies. Inside this band of frequencies, the reaction of a system is flat. Outside this band, the frequency reaction bit by bit drops off. The boundary in a system’s frequency response at which the energy moving through a system decreases instead of going through is known as the cut-off frequency.
Passband bandwidth is a distinction between the upper and lower cut off frequency, and a baseband bandwidth defines as the highest system's frequency. The bandwidth of a signal in Hertz is a focal idea in numerous fields like hardware, radio, digital communications, the theory of information, and so on.
FAQs on Bandwidth of a Signal
1. What is meant by the bandwidth of a signal in Physics?
In Physics, the bandwidth of a signal refers to the range of frequencies contained within that signal. It is defined as the difference between the highest frequency component (f_max) and the lowest frequency component (f_min) present in the signal. Every signal that carries information, whether it's audio, video, or data, occupies a specific range on the frequency spectrum, and this range is its bandwidth.
2. How is the bandwidth of a signal measured and what is its unit?
Signal bandwidth is measured in Hertz (Hz). For a simple passband signal, it is calculated as the difference between the upper (f_upper) and lower (f_lower) cut-off frequencies. The cut-off frequencies are the points at which the signal's energy starts to decrease significantly. The formula is: Bandwidth = f_upper - f_lower. For a baseband signal, the bandwidth is simply considered its highest frequency.
3. Can you provide some real-world examples of bandwidth requirements for different signals?
Yes, different types of signals require different bandwidths for clear transmission. Here are some common examples as per the CBSE/NCERT syllabus:
- Speech Signals: For telephonic communication, a bandwidth of about 2800 Hz (from 300 Hz to 3100 Hz) is sufficient.
- Music Signals: To reproduce music with high fidelity, a much wider bandwidth of about 20 kHz is needed to accommodate the range of instruments and pitches.
- Video Signals: Television video signals require a very large bandwidth, typically around 4.2 MHz, to transmit the vast amount of visual information.
4. What is the fundamental difference between the bandwidth of an analog signal and a digital signal?
The key difference lies in their frequency composition. An analog signal, like a sine wave, typically has a well-defined and finite bandwidth based on its highest frequency component. A digital signal, which is a sequence of square-like pulses, is theoretically composed of an infinite number of sine waves (harmonics). Therefore, its bandwidth is theoretically infinite. In practice, we limit the bandwidth for a digital signal to a range that contains the most significant harmonics needed to preserve the pulse shape without distortion.
5. How does signal bandwidth differ from the bandwidth of a communication channel?
This is a crucial distinction. Signal bandwidth is an intrinsic property of the information being sent (e.g., the frequencies in your voice). In contrast, channel bandwidth is a property of the transmission medium (e.g., an optical fibre, a coaxial cable). The channel bandwidth specifies the range of frequencies that the medium can transmit effectively. For successful communication, the channel bandwidth must be equal to or greater than the signal bandwidth.
6. Why do different transmission media like optical fibres and coaxial cables offer vastly different bandwidths?
The difference in bandwidth is due to the physical principles they operate on. Coaxial cables transmit electrical signals, which suffer from increased power loss (attenuation) at higher frequencies, limiting their practical bandwidth (around 750 MHz). In contrast, optical fibres transmit signals using light waves. Since light has a much higher frequency than the radio waves used in electrical cables, optical fibres can support an enormous range of frequencies, giving them a massive bandwidth of over 100 GHz and enabling much faster data transmission.
7. In the context of modulation, how does the bandwidth of a message signal affect the bandwidth of the modulated wave?
In modulation, the message signal is superimposed onto a high-frequency carrier wave. This process directly impacts the bandwidth requirement. For Amplitude Modulation (AM), the modulated wave contains the carrier frequency plus two sidebands (upper and lower). The total bandwidth of the AM wave becomes twice the maximum frequency (or bandwidth) of the message signal. For example, if a 5 kHz audio signal is amplitude modulated, the resulting modulated wave will have a bandwidth of 10 kHz.
