In this write up, I attempt to demystify propagation of energy in waveguides without touching upon complex mathematics which anyway is found in literature. Traditionally, at lower frequencies upto VHF and UHF, coaxial cable has been obvious choice for transmission of energy. However, skin effect severely degrades the performance of such lines at high frequencies and this presses us to look at an alternative that could let us transmit energy not in the form of currents but in the form of fields. Simply using an antenna to radiate fields in to free space is not viable due to the inherent path losses involved. We look for a setup that could 'guide' energy in the form of fields from one point to another.
It is well known that the reflection coefficient of a surface made out of pure conductor is -1. Which means that an EM wave incident on a metallic surface is turned back completely with its phase inverted by 180 degrees. If we could find an arrangement such that the EM waves are completely reflected back into a region from 'all' sides and the arrangement is such that the waves are also carried forward, what we arranged is a waveguide.
This is precisely what a waveguide does. It is made out of a nearly perfect conductor to make the reflection coefficient as close to -1 as possible. This would mean little penetration of fields into the thickness of the conductor and hence little losses in the walls.
Having established that wave propagation is indeed possible by multiple reflections from all sides, Iam rather tempted to assert at this point that, not all frequencies are willing to go down the waveguide of given dimensions.
In my coming posts, I will attempt to explain further as what kind of arrangement accommodates a given frequency. I hope you enjoyed reading this. A rather lucid explanation is found in the book "Electronic communication systems" by John.F.Kennedy.
It is well known that the reflection coefficient of a surface made out of pure conductor is -1. Which means that an EM wave incident on a metallic surface is turned back completely with its phase inverted by 180 degrees. If we could find an arrangement such that the EM waves are completely reflected back into a region from 'all' sides and the arrangement is such that the waves are also carried forward, what we arranged is a waveguide.
This is precisely what a waveguide does. It is made out of a nearly perfect conductor to make the reflection coefficient as close to -1 as possible. This would mean little penetration of fields into the thickness of the conductor and hence little losses in the walls.
Having established that wave propagation is indeed possible by multiple reflections from all sides, Iam rather tempted to assert at this point that, not all frequencies are willing to go down the waveguide of given dimensions.
In my coming posts, I will attempt to explain further as what kind of arrangement accommodates a given frequency. I hope you enjoyed reading this. A rather lucid explanation is found in the book "Electronic communication systems" by John.F.Kennedy.
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