Attenuation at High Frequency

Hi

Please find the attached file (image). How does SIW show less attenuation at high frequency whereas Microstrip shows high attenuation @ high frequency? Which property / parameter plays role here?

plz clarify

It's normal.Waveguides have always less attenuation compare to Transmission Lines at very high frequencies.Therefor Waveguides have "lower cut-off frequency" and they don't have higher cut-off frequency due to their EM modes ( TE or TM)

Hi

Really thank You so much. Is there any relation between TEM Vs TE modes with respect to attenuation and frequency? Please explain me and/or share me a document to understand this.

Thanks