Figure 10: Loss difference MS.
The second transmission mode is CBCPW. CBCPW typically exhibits larger losses over frequency for the same length L when it is compared to MS, as higher conductor loss occurs due to the additional ground planes on top of the structure[3]. In this case, as the dimensions of the measured samples imply a dominant wave propagation in the substrate, the total losses are just slightly higher as for the discussed MS lines. Figure 11 displays the measurement results for material type A. The difference of the losses of the structuring processes to be compared appears to be already present for very low frequencies and that for all three line lengths. For higher frequencies the impact of fabrication process does not seem to increase much. At 110 GHz for L = 20 mm the additional loss for pattern plating is approximately 0.42 dB, which is very close to the measured value for the similar MS line. For material type B (Figure 12) resembling results as for material type A are achieved. By fitting the insertion loss for four different lengths of the CBCPW lines, in the same manner as it was done for MS, the results for material type B can be seen in Figure 13. The frequency dependence is quite different compared to MS as it seems that additional losses occur already at low frequencies, albeit, losses do not increase as steeply as for MS.
Figure 11: Material type A CBCPW.
Figure 12: Material type B CBCPW.
Figure 13: Loss difference CBCPW.
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