propagation constant

For an electromagnetic field mode varying sinusoidally with time at a given frequency, the propagation constant is the logarithmic rate of change, with respect to distance in a given direction, of the complex amplitude of any field component. The propagation constant, γ, is a complex quantity given by whereα, the real part, is the  attenuation constantβ, the imaginary part, is the  phase constanti = Source: Federal Standard 1037C.
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For an electromagnetic field mode varying sinusoidally with time at a given frequency, the logarithmic rate of change, with respect to distance in a given direction, of the complex amplitude of any field component. Note: The propagation constant, , is a complex quantity given by = +i, where , the real part, is the attenuation constant and , the imaginary part, is the phase constant.