Microwave and Wireless Communications Technology

Propagation Modes in Waveguide 91

c = ~/VpVg

(5-3)

In any wave phenomenon the product of

frequency and wavelength

is the

velocity.

Thus, for a TEM wave in unbounded free space, we know that

c = F Ko (5-4)

Because the frequency (F) is fixed by the generator, only the wavelength can

change when the velocity changes. In a microwave waveguide, we can relate phase

velocity to wavelength as the wave is propagated in the waveguide (~.):

/~xc

;to (5-5)

where

Vp

= phase velocity in meters per second (m/s)

c = free-space velocity (3 x 108 m/s)

~, = wavelength in the waveguide in meters (m)

~o = wavelength in free space (c/F)