Transformed lumped element integrated passive bandpass filters for gigahertz range spectrum monitor receivers

Two integrated bandpass filters have been designed and fabricated on standard 130 nm CMOS technology. The lumped element, third-order Butterworth bandpass filters at 9.45 and 1.75 GHz are designed for sub-band filtering in a spectrum monitoring receiver function in a future cognitive radio. A series coupled resonator topology is selected and a novel delta-star transformation technique is applied to obtain element values suitable for reliable fabrication on an integrated circuit. Occupying die areas of 780 × 200 μm and 1750 × 500 μm each, the filters achieve insertion losses of 15.6 and 8.6 dB, and band-widths of 1 GHz and 210 MHz, respectively, which are suitable for the chosen spectrum monitor receiver architecture.