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An electromagnetic current that carries data from the source to the receiver is termed a signal. The data carried through the signal can be in the forms of voice, music, video, document, or a picture. According to the type of data transmitted, the required bandwidth differs—a signal wave results from changes or fluctuations in the frequency or amplitude of transmitted data.
Generally, signals can be of different types in terms of electronics. One is Analog, which is a continuous sine wave that requires lesser signal bandwidth. Moreover, the other is the digital wave, which is squared and discrete and requires larger signal bandwidth.
Bandwidth
As per the study material notes on signal bandwidth & transmission medium, bandwidth generally refers to the span of frequencies in a band used to transmit a signal through a particular medium.
Bandwidth can be measured as
Bandwidth = f₂ – f₁,
Where f₂ is the upper frequency and f₁ is the lower frequency in a band.
Signal bandwidth
Signal bandwidth is the distance between the peak at the higher frequency and the dip at the lower frequency of a signal wave. In simpler terms, the signal bandwidth is more or like the thickness of a signal wave. The term ‘bandwidth’ came into usage in the late 19th century, referring to data transfer capacity through a communication system.
Transmission medium
A transmission medium refers to the base material that helps transmit or transfer the data from one device to another. Signal waves can be transmitted through physical cables and wires or air in the atmosphere.
Types of the transmission medium
The transmission media can be classified as the following based on transmitting the signals. The two broad groups of transmission media are:
Guided or Bound media
Unguided or unbound media
Guided or Bound Transmission media
According to study material notes on signal bandwidth & transmission medium, in a guided or bound transmission media, the data are transmitted through physical wires directed to a particular receiver. These are divided into 3 types.
Twisted cable:
Twisted cables contain a bunch of two coiled wires that are insulated separately in a protective sheath. It can be divided into two types:
Unshielded twisted pair (UTP) is a pair of two insulated copper wires that inhibit interference. Thus, it is most commonly used in telecommunications.
Shielded twisted pair (STP) has a foil covering the twisted pair of wires to block the external interference during transmission. It is mostly used in transmitting data through telephone cables and in ethernet.
Coaxial cable:
Coaxial cable consists of two insulated parallel conductors.
1st layer – The innermost copper wire layer.
2nd layer – An insulation layer around the copper wire.
3rd layer is made up of the parallel conductor, which acts as a second conductor and a noise reducer.
4th layer – another insulator is protecting the parallel secondary conductor. This whole 4-layered set-up covers the cable with a plastic tube that protects.
The coaxial cable is of two types:
Baseband uses digital signals so it can be used to deliver large amounts of data at high speed. It is used in LANs.
Broadband uses analog signals allowing multiple waves of varied frequencies to pass through. Television cables use such a medium.
Fibre optic cable:
As the name suggests, a fibre optic cable transmits light waves to transfer data. The fibre optics are packed as a bundle covered by a protective sheath. A single fibre in the bundle has three different layers.
1st layer – The innermost layer is the glass fibre core.
2nd layer – The cladding; It is a lesser density glass covering the core as a protective sheath. It has a lower refractive index than the core so that the light waves retain themselves inside the core.
3rd layer – It covers the cladding as a protective sheath, isolating it from the other fibres of the bundle.
Unguided or Unbound Transmission media
An unguided medium is a wireless medium that requires no physical bound to transmit data. The transmission occurs through the air in the atmosphere. It can be of 3 different types.
Radio wave:
The radio wave frequency range is around 3KHz to 1GHz. It can pass through the buildings and is simple to set up. Radio waves either propagate through the troposphere or the ionosphere.
Microwave:
The microwave frequency range is around 1GHz to 300GHz. It has a higher frequency than radio waves. It needs the sending and receiving antennae to be positioned accurately. The higher the antennae, the more efficient the signalling is.
Infrared wave:
The frequency range of infrared waves is around 300GHz to 400THz, so the distance travelled by the waves is shorter. It is generally used in Remotes and wireless gadgets.
Conclusion
The signal bandwidth and transmission medium study material are given in the article. The signal bandwidth is the distance between the crest and the trough of the signal wave in the transmission medium. If the signal bandwidth is high, the data transmission speed will be higher. So, the transmission medium used should be capable of transmitting the data without decreasing its quality. The human ear can hear around 20 – 20,000 kHz of frequency. The human voice produces a frequency of around 300 to 700 Hz. Thus, the phone cables must be capable of transmitting such ranges without any cross interferences.
