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High-performance integrated slow-wave coplanar waveguides (S-CPW) are compared with conventional coplanar waveguides (CPW) fabricated in a 65-nm High-Resistivity-SOI (HR-SOI) CMOS technology. As expected, S-CPW demonstrates better performance at millimeter-wave frequencies in term of higher effective dielectric permittivity, which is due to the patterned floating shield inserted between the transmission line and the substrate. In addition, S-CPW shows a lower attenuation constant despite of the added metallic patterned floating shield on HR substrate. For demonstration purpose, both low- and high- characteristic impedance S-CPW and CPW are characterized. For 28-Ω S-CPW and 65-Ω S-CPW, the effective dielectric permittivity is improved by a factor of 6 and 2, respectively. Meanwhile, attenuation constants of slow-wave structures are lower than 0.9 dB/mm and 0.57 dB/mm at 60 GHz, compared to CPW ones which are as high as 1.5 dB/mm and 0.95 dB/mm, respectively. Furthermore, the loss distribution for the S-CPW structure is detailed by varying the patterned floating shield length for both standard Bulk and HR-SOI substrates.
Date of Publication: May 2012