In the context of transmission lines, the concept of "phase wavelength" is not commonly used. However, it is possible that you are referring to the electrical wavelength or the physical length that corresponds to a phase change of 360 degrees (or 2π radians) in a transmission line.
In a transmission line, signals propagate as electromagnetic waves. The electrical wavelength (λe) is the distance traveled by the wave in the transmission line during one complete cycle of the signal's frequency. It is related to the physical wavelength (λ) in free space and the characteristic impedance (Z0) of the transmission line through the following equation:
λe = λ / √(1 - (Z0 / Zc)^2)
Where:
- λe is the electrical wavelength in the transmission line
- λ is the physical wavelength in free space
- Z0 is the characteristic impedance of the transmission line
- Zc is the impedance of the load connected to the transmission line
The electrical wavelength can be shorter or longer than the physical wavelength, depending on the characteristic impedance of the transmission line and the impedance of the load. The phase velocity in the transmission line is also different from the speed of light in free space, which is another factor affecting the relationship between the physical and electrical wavelengths.
Therefore, the "phase wavelength" in a transmission line is not a commonly used term, but the electrical wavelength is a related concept used to describe the propagation of signals in transmission lines.