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 x 0.2 mm², equivalently 0.012 λg² . 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.