clarifications on SIW basics

Dear All,

Please clarify my doubts:

1. Is there any relation between TEM Vs TE modes with respect to attenuation and frequency?

2. Is Tight Tolerance (fabrication) at Very high frequency a disadvantage of planar transmission line? If we design a component @ 90GHz, in which of the following real time fabrication is difficult? plz explain

Microstrip , Rectangular waveguide , Dielectric filled waveguide, SIW

3. Dielectric filled waveguide Vs SIW:

As per my understanding, size of the component will be same if it is designed using Dielectric filled waveguide or SIW. Am I right?

Leakage / radiation Losses will be higher if a component is designed using SIW when compared to Dielectric filled waveguide . Am I right?

But a component designed using SIW will be compact (since it is in substrate itself) and when compared to Dielectric filled waveguide . Am I right?

4. What is the role of SIW interconnect/transition ? Is it mode conversion alone? Or anything with impedance matching?

Thank You