Low-cost inverted line in silicon/glass technology for filter in the Ka-band

This paper introduces a new low-cost technology for inverted lines on glass or on silicon. After a description of the simple technological process, the single and coupled lines characteristics are examined versus several geometrical parameters. Electromagnetic simulations and measurements are compared and a good agreement is obtained between them. The line attenuation is shown to be very low. Another advantage of this technology is the increase of the coupled lines spacing for some given odd and even characteristic impedances in comparison with classical technology, which helps the design of coupled line filters. Using the presented line characteristics, a coupled line bandpass filter has been designed, fabricated, and characterized in the Ka-band. According to simulations, measurement results show the good performances of the filter: the bandpass is of 28%, the measured insertion loss and return loss are, respectively, -2.2 and -24 dB at the center frequency. The attained performances show that the proposed technology is a good candidate to be used in the fabrication of millimeter-wave integrated circuits.