electromagneticreflectionwave
Below is a wikipedia section about reflection coefficient in electrical engineering:
source: https://en.wikipedia.org/wiki/Reflection_coefficient
It says that the incident to reflected wave ratio is complex. What does it indicate in practice here being complex?
I would use the term "Polar Response" or "Polar Gain Response". Typically it is graphed as such:
Where 0 degrees (straight up) is along the main axis of the antenna.
Small objects (small in comparison with wavelength) diffract the wave around them, rather than reflect the wave back, they are effectively invisible (unresolved). By decreasing the wavelength (increasing frequency) the objects diffract less of the waves energy and reflect more of it making them detectable.
Sharp edges, small holes etc. do the same. By decreasing the wavelength this enables such features to be resolved.
Best Answer
it just means that the reflection coefficient can be represented as a complex number/quantity in the form :
a +jb or in polar notation using magnitude and angle.
It doesn't have any "physical" significance or so. Its just a mathematical tool to represent the nature of a quantity and simplify calculations. For eg: when we represent an impedance as a complex quantity, Z = a+jw , we can infer that a there is a real part which doesn't vary with input voltage (Resistance), and there is an imaginary part jw ( Reactance part due to inductors and capacitors), which can varies with input voltage frequency.