Compact Millimeter-Wave CMOS Bandpass Filters Using Grounded Pedestal Stepped-Impedance Technique

This paper presents compact CMOS millimeter-wave bandpass filters based on a new stepped-impedance technique by incorporating a grounded pedestal into the microstrip line. The characteristic impedance of a microstrip line can be effectively changed by varying both the height of pedestal and the width of line. Therefore, the stepped-impedance resonators and stubs can be realized in the compact three-dimensional forms in CMOS. Two millimeter-wave bandpass filters were designed by using the new stepped-impedance resonators and stubs. Their chip sizes are significantly miniaturized to 0.37
$\,\times\,$
0.2 mm
$^{2}$
, equivalently 0.012
$\lambda_{g}^{2}$
. The first chip filter has the insertion loss of 3.1–3.4 dB in 59–71 GHz and the second filter has the insertion loss of 3.5–3.8 dB in 53–64 GHz. Both chip filters have good stopband suppression attributed from the existence of transmission zeros.