Propagation velocity through coax's with different velocity factors?

[hobbs125]

Hi everyone,

I have been studying transmission lines and it got me thinking.

If we have a series circuit which has two equal length transmission lines with the same Zo but with different velocity factors how does this effect the wave velocity through the circuit?

Do the waves travel faster through one line and then slow down and bunch up in the other?

Does the mismatch in velocity factor produce reflections even through the Zo and length of each line is identical?

 

[Baluncore]

The reflections on a line are due to changes in line impedance.
There is no reflection at a change in velocity factor unless there is also a change in impedance.

 

[meBigGuy]

When velocity factor changes, wavelength changes so there is no bunching.

 

[Baluncore]

The constant here is the period, frequency or pulse repetition rate.

There is a good analogy with traffic on a road that has an increase in speed limit.
The vehicles are further apart, but they still have the same time period between vehicles and the same number of vehicles per hour.

The length of the road or transmission line is not important.

 

[alphy]

I can provide some insight into this question. The velocity factor of a coaxial cable refers to the ratio of the speed of an electromagnetic wave traveling through the cable to the speed of light in a vacuum. This value is affected by the dielectric material used in the cable and can vary between different types of coaxial cables.

In a series circuit with two equal length transmission lines, the wave velocity will be affected by the velocity factor of each line. This means that the wave will travel faster through the line with a higher velocity factor and slower through the line with a lower velocity factor.

This can cause the waves to arrive at different times at the end of the circuit, which can result in reflections and interference. The mismatch in velocity factor can also cause impedance mismatches, which can lead to signal loss and distortion.

To avoid these issues, it is important to use transmission lines with the same velocity factor in a series circuit. This will ensure that the waves travel at the same speed and arrive at the end of the circuit at the same time, minimizing reflections and maintaining signal integrity.

In conclusion, the velocity factor of a coaxial cable can have a significant impact on the propagation velocity of waves through a series circuit. It is important to consider this factor when designing and setting up transmission lines to ensure optimal performance.