Why are Coaxial Cables Highly Insulated?
Why are Coaxial Cables Well Insulated?
What is Coaxial Cable?
Coaxial cables conduct electrical signals using an inner conductor, usually made of copper or copper-plated wire, which is surrounded by an insulating layer and enclosed by a shield. This shield typically consists of one to four layers of woven, braided aluminum or copper wire, and aluminum foil.
Common applications of coaxial cables include video and CATV distribution, RF and microwave transmission, as well as computer instrumentation and connectors.
Construction of Coaxial Cable
A coaxial cable consists of a central conductor, usually copper, surrounded by insulation, a grounded shield, and a braided wire. Some coaxial cables include both a braided wire and aluminum foil for additional shielding. Coaxial cabling is primarily used in the cable television industry and for computer networks like Ethernet.
Many coaxial cables have an outer insulating sheath to protect them from environmental factors. The term “coaxial” (co-axial) refers to the inner conductor and shield sharing the same geometric axis. Coaxial cables are distinct from other cables that carry high-frequency signals, such as RF signals, and those that carry low-frequency signals, like audio.
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Operation of Coaxial Cables
During electrical conduction through a copper wire, not all the energy reaches its destination; some energy is lost as heat due to the internal resistance of the copper. The electrical energy is carried by electrons, and as they move, they emit electromagnetic radiation of varying frequencies and wavelengths when they jump between energy levels after absorbing energy.
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Application of Coaxial Cables
Coaxial cables are used as transmission lines for radio frequency signals. They connect radio transmitters and receivers to their antennas, are used in computer networks, and are commonly employed in distributing television signals.
One advantage of coaxial cables over other types of transmission lines is that, in an ideal coaxial cable, the electromagnetic field carrying the electrical signals exists only in the space between the inner and outer conductors. This allows the cables to be installed near metallic objects, such as gutters, without significant power loss during signal transmission, unlike other transmission lines that may leak signals into the surrounding environment.
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Signal Leakage in Cables
Signal leakage occurs when electromagnetic fields or radiation pass through the shield of the cable, potentially in all directions. External signals can also penetrate the cable, causing interference, a process known as ingress. Interference causes noise and reduces signal quality. Similarly, signals within the cable can leak out into the environment, a process known as egress, which also results in interference and reduces the efficiency of the transmitted signal.
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Why is a Coaxial Cable Highly Insulated?
The electrical cables found in our homes are insulated. Electrical cables are insulated for safety purpose and also to minimize energy loss. The insulation offers great resistance to leakage of energy to the surrounding. Since the loss of energy is minimal in such cables, when there is excessive current, it damages the cables and that is why we have fuse in our home devices. Just as electrical cables emits electromagnetic radiation and electrical energy in form of heat, coaxial cables can do the same but are hindered from doing so by insulating them. For a single core cable, the resistance offered by the insulation to electrical energy is given as
Rins = ρdr / 2πrl
When integrated;
Rins [ ρ / 2πrl (loge (r1/r2))]
where
- ρ = resistivity of the conductor.
- r1 = radius of the conductor.
- r2 = radius of the insulator.
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We are everyday being bombarded by electromagnetic waves from all angles. There are lots and lots of waves passing through our homes all the times. These waves could be radio waves propagated from a nearby radio station, microwave, waves from our cell phones, infrared ray and lots more.
There is a possibility that the waves propagated by the cables will have the same frequency or wavelength which can cause interference. Not only will the cables leak signals and cause interference and reduce the signals’ intensity, it can also absorb a signal that is passing close by.
With our cell phones switched on, our radio on and our TV set also on, if the coaxial cables were not highly insulated you hardly can hear a sound due to interference. Also notice that when you are close to a radio and a signal comes into your cell phone, the radio set begins to make unwanted noise due to interference of the waves.
Coaxial cables are well-insulated to prevent signal leakage and to block external signals from penetrating into the cable. In addition to preventing signal leakage, these cables also prevent the loss of electrical energy, as the insulating materials used are non-conductive to both heat and electricity.
The coaxial design confines the magnetic and electric fields propagated along the conductor to the dielectric, which acts as an insulator, allowing minimal or no signal leakage outside the shield.
Coaxial cables are an excellent choice for transmitting weak signals that cannot tolerate external interference, as well as for carrying higher electrical signals that must not radiate or couple into nearby structures or circuits.
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How inform elecronik
No edge at cross-section formation yields minimum electric field, both edges of cable yield stronger electric field, so most people select coaxial cable using under high voltage.
Such good information in this article, really impressive. Thanks a lot, it was very helpful and I will definitely share this post.