Wave filters clarify a signal by filtering out all other noise. They are useful for receiving communications in deep space where there are other stellar phenomena that emit frequencies too. These extra frequencies become part of the white noise always present in space. A wave filter will keep a satellite from being confused by this extra "noise" from space.
Wave guides allow satellites to manipulate radio waves and redirect them within the satellite for processing. These are really quite essential for any satellite performing a function concerning communications.